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  • Articles  (107)
  • diatoms  (58)
  • Nitrification  (49)
  • Springer  (107)
  • 1990-1994  (70)
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  • Articles  (107)
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  • Springer  (107)
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  • 1
    Electronic Resource
    Electronic Resource
    Effect of bamboo harvest on dynamics of nutrient pools, N mineralization, and microbial biomass in soil (1994)
    Springer
    Biology and fertility of soils 18 (1994), S. 137-142 
    Details
    ISSN: 1432-0789
    Keywords: Microbial biomass ; Bamboo savanna ; N mineralization ; Nutrient pools ; Temporal variations ; Nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of harvesting bamboo savanna on the dynamics of soil nutrient pools, N mineralization, and microbial biomass was examined. In the unharvested bamboo site NO inf3 sup- -N in soil ranged from 0.37 to 3.11 mg kg-1 soil and in the harvested site from 0.43 to 3.67 mg kg-1. NaHCO3-extractable inorganic P ranged from 0.55 to 3.58 mg kg-1 in the unharvested site and from 1.01 to 4.22 mg kg-1 in the harvested site. Over two annual cycles, the N mineralization range in the unharvested and harvested sites was 0–19.28 and 0–24.0 mg kg-1 soil month-1, respectively. The microbial C, N, and P ranges were 278–587, 28–64, and 12–26 mg kg-1 soil, respectively, with the harvested site exhibiting higher values. Bamboo harvesting depleted soil organic C by 13% and total N by 20%. Harvesting increased N mineralization, resulting in 10 kg ha-1 additional mineral N in the first 1st year and 5 kg ha-1 in the 2nd year following the harvest. Microbial biomass C, N and P increased respectively by 10, 18, and 5% as a result of bamboo harvesting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336460
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  • 2
    Electronic Resource
    Electronic Resource
    Diatom responses to late Quaternary vegetation and climate change, and to deposition of two tephras in an alpine and a sub-alpine lake in Yoho National Park, British Columbia (1994)
    Springer
    Journal of paleolimnology 11 (1994), S. 173-188 
    Details
    ISSN: 1573-0417
    Keywords: Late Quaternary ; diatoms ; pollen ; climate change ; tephra ; shallow alpine and sub-alpine Iakes ; British Columbia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The late Quaternary diatom records from alpine Opabin Lake (altitude 2285 m a.s.l.) and sub-alpine Mary Lake (altitude 2054 m a.s.l.), located in Yoho National Park, British Columbia (lat. 51 ° 21′N; long. 116 ° 20′), have been analyzed, and changes in these records have been used to reconstruct lake histories. The results have also been related to independently inferred vegetation and climate changes. Following deglaciation, when both lakes were receiving high inputs of clastic materials, benthic diatom taxa dominate the records of these two shallow lakes with small species ofFragilaria being particularly prominent. During the early to mid-Holocene period, when treeline was at a higher elevation than today, the diatom flora of both lakes became more diverse with previously minor species becoming more prominent.Cyclotella radiosa occurs in cores from both Mary Lake, and much deeper, neighbouring Lake O'Hara during the warm early Holocene, and may reflect this warmer climate, a longer ice-free season than presently, and perhaps less turbid water, or its presence may reflect a subtly higher nutrient status of the lake water during this period. The Neoglacial is marked by increased amounts of sediments originating from glacial sources in Opabin Lake, which undoubtedly led to very turbid water, and by the presence ofEllerbeckia arenaria f.teres andCampylodiscus noricus v.hibernica in Opabin Lake; however, these species are absent from Mary Lake which has not been influenced by either glacial activity since the recession of the glaciers prior toc. 10 000 years BP or water originating from Opabin Lake. The impact of the two tephras during the Holocene was dramatic in terms of increased diatom production, as exemplified by the increases in diatom numbers, but there was little effect upon species composition. The diatom records and changes in the diatom:cyst ratio suggest that the chemical status of these two small, shallow lakes has changed little during the Holocene, other than after deposition of the two tephras. These results provide evidence that shallow alpine and high sub-alpine lakes are sensitive recorders of past environmental changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00686864
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  • 3
    Electronic Resource
    Electronic Resource
    Rescaling species optima estimated by weighted averaging (1994)
    Springer
    Journal of paleolimnology 12 (1994), S. 155-162 
    Details
    ISSN: 1573-0417
    Keywords: calibration ; weighted averaging ; diatoms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The common practice of linear deshrinking in weighted averaging is known to be equivalent to a linear rescaling of the estimated species optima. In published lists of species optima, the use of rescaling is recommended, as it allows values derived from different data sets to be compared and used for new inferences, assuming that taxonomic consistency is assured. Rescaling optima is also shown to influence WA estimates of species tolerances. Non-linear rescaling is also discussed, in the form of cubical rescaling and weighted averaging-partial least squares (WA-PLS). The use of a different deshrinking equation in a small data set did lead to similar prediction errors, probably because of the small size of the data set used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00678091
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  • 4
    Electronic Resource
    Electronic Resource
    A new method for the determination of absolute abundance of diatoms and other silt-sized sedimentary particles (1994)
    Springer
    Journal of paleolimnology 12 (1994), S. 171-179 
    Details
    ISSN: 1573-0417
    Keywords: diatoms ; methods ; absolute abundance ; microfossils ; paleolimnology ; paleoceanography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The determination of absolute abundances of diatoms in paleolimnological and paleoceanographic studies is now becoming a routine step in diatom paleoecological investigations. Several distinct methods have been described for establishing absolute diatom abundance. Each of these methods has its own strengths and weaknesses. The most common weakness in diatom preparation methods is the use of aliquot subsampling from an assumed ‘well-mixed’ diatom suspension. Described here is a simple, efficient and inexpensive method that utilizes settling of diatoms through a 10 cm water column, which yields an effectively random distribution, and uses no aliquot subsampling. Only a few milligrams of sample are needed, permitting microstratigraphic analysis of, for example, individual varves. The method is shown to be both reproducible and accurate for sediments ranging in diatom concentration from less than 10 million to more than one billion diatoms per gram. Multiple slides or SEM stubs can be simultaneously prepared. The method works well for the analysis of most silt-sized microfossils or other sedimentary particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00678093
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  • 5
    Electronic Resource
    Electronic Resource
    The CASPIA project: diatoms, salt lakes, and environmental change (1994)
    Springer
    Journal of paleolimnology 12 (1994), S. 191-196 
    Details
    ISSN: 1573-0417
    Keywords: diatoms ; saline lakes ; palaeolimnology ; palaeoclimate ; transfer functions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The Climate and Salinity (CASPIA) Project is concerned with diatoms as environmental indicators in inland waters and their use in reconstructing salinity and major ion composition from fossil diatom assemblages in lake sediments. By comparing saline lake diatom floras from around the world the project aims to establish a common, harmonised approach to sample collection, diatom identification and nomenclature, and to develop techniques for numerical analysis and data storage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00678020
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  • 6
    Electronic Resource
    Electronic Resource
    Diatom-salinity relationships in 111 lakes from the Interior Plateau of British Columbia, Canada: the development of diatom-based models for paleosalinity reconstructions (1994)
    Springer
    Journal of paleolimnology 12 (1994), S. 197-221 
    Details
    ISSN: 1573-0417
    Keywords: diatoms ; paleolimnology ; paleoclimatology ; salinity ; athalassic ; British Columbia ; CCA ; transfer function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Diatoms were identified and enumerated from the surface sediments of 111 lakes, 45 from the Kamloops region and 66 from the Cariboo/Chilcotin region, located on the southern Interior Plateau of British Columbia, Canada. This paper is an extension of another study which investigated the relationship of diatoms to salinity and ionic composition in 65 lakes from the Cariboo/Chilcotin region. The 111 lakes spanned a large gradient in salinity, ranging from fresh through hypersaline (late-summer salinity values ranged from 0.04 to 369 g l−1), and included both carbonate- and sulphate-dominated lakes with sodium and magnesium as the dominant cations. The Kamloops region had more sulphate-dominated, hypersaline lakes and fewer carbonate-rich lakes than the Cariboo/Chilcotin region. Most lakes had higher salinities in the late-summer compared to the spring. Both salinity and brine-type were important variables that could explain the different diatom assemblages present in the lakes. The majority of diatom taxa had salinity optima in the freshwater to subsaline range (〈3 g l−1), and the taxa displayed a range of both narrow and broad tolerances along the salinity gradient. Weighted-averaging regression and calibration, and maximum likelihood techniques were used to develop salinity inference models from the diatom assemblages based on their relationship to the spring, late-summer and average lakewater salinity measurements. Simple weighted-averaging (WA) models generally produced the same or lower bootstrapped RMSEs of prediction than weighted-averaging with tolerance downweighting (WA(tol)) in the two regional and the combined datasets. Weighted averaging partial least squares (WA-PLS) showed little or no improvement in the predictive abilities of the datasets, as judged by the jackknifed RMSE of prediction. In all cases, the combined dataset of 102 lakes performed better than either of the smaller regional datasets, with relatively little difference between spring, average and late-summer salinity models. The maximum likelihood models gave lower apparent RMSEs of prediction in comparison to other methods; however, independent validation of this technique using methods such as bootstrapping were not undertaken because of the computer intensive nature of such analyses. These diatom-based salinity models are now available for reconstructing salinity and climatic trends from appropriately chosen closed-basin lakes in the Interior region of British Columbia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00678021
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  • 7
    Electronic Resource
    Electronic Resource
    A Holocene paleoenvironmental history of Lake Alexandria, South Australia (1994)
    Springer
    Journal of paleolimnology 12 (1994), S. 259-268 
    Details
    ISSN: 1573-0417
    Keywords: sediments ; 14C ; 210Pb ; diatoms ; geochemical analyses ; coastal paleoenvironments ; paleolimnology ; Nodularia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract An investigation of Holocene sediments within Lake Alexandrina, a shallow coastal lake at the mouth of the Murray River, South Australia, is presented based on a multidisciplinary approach.14C and210Pb radiometric dating methods are used to establish a geochronological framework for the last 7000 yr BP, and diatoms, sand-siltclay ratios, organic carbon, phosphorus and copper concentrations are used to infer paleoenvironmental changes. The diatom assemblages indicate a change from marine-brackish to oligosaline-freshwater conditions between 7000 and 6000 yr BP, with sea-level stabilisation and continuous barrier formation across the Murray mouth. Sand pulses after 2300 yr BP document sand spit formation in the lake and the commencement of extensive lacustrine sedimentation. In the past 100 years which include the advent of European settlement in the region, the short-term210Pb-based mass accumulation rate of 0.063 g cm−2 yr−1 is greater than that of the longer-term mean14C-based rate (0.023 g cm−2 yr−1), and high concentrations of phosphorus and copper correspond to historical records of blue-green algal blooms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00678024
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  • 8
    Electronic Resource
    Electronic Resource
    Acidity of twelve northern New England (U.S.A.) lakes in recent centuries (1994)
    Springer
    Journal of paleolimnology 12 (1994), S. 103-154 
    Details
    ISSN: 1573-0417
    Keywords: acidification ; alkalization ; pH ; alkalinity ; diatoms ; sediment chemistry ; New England ; catchment effects ; land use ; logging ; acidic deposition ; air pollutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Studies of sediment cores from 12 acidic lakes in granitic, forested and uninhabited catchments in northern New England, U.S.A. produced diatom-inferred pH (IpH) 5.2 to 5.8 and alkalinity (Ialk) −12 to 31 µeq l−1, with slowly declining values at some lakes, for one to four centuries prior to logging. Increases of IpH (Δ0.05 to 0.60) and Ialk (Δ5 to 40 µeq l−1) correlate with logging in the catchments in the early-1800s to early-1900s. Recovery to pre-logging IpH and Ialk correlates with forest succession toward conifers, and is completed in the late-1800s to mid-1900s. Beginning at 1915–1920 (4 lakes), 1930–1950 (4 lakes) and 1965–1970 (4 lakes), IpH and Ialk start decreasing below pre-logging values due to atmospheric acidic deposition, leading to respective total decreases of 0.10 to 0.45 (X=0.25) and 5 to 25 µeq l−1 (X=15). Inputs of anthropogenic Pb, Zn, V, polycyclic aromatic hydrocarbons, and soot from the atmosphere are first detectable in early- to late-1800s sediment, and Cu in late-1800s sediment, increase rapidly in the late-1800s to mid-1900s, and level off or decrease since the 1960s — partly due to emission controls. Decreasing Ca, Mn, and possibly Zn relative to other metals and normalized to organic content, and increasing flux of Fe to the lakes, indicate soil and water acidification after 1900.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00678090
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  • 9
    Electronic Resource
    Electronic Resource
    The Holocene history of West Basin Lake, Victoria, Australia; chemical changes based on fossil biota and sediment mineralogy (1994)
    Springer
    Journal of paleolimnology 12 (1994), S. 235-258 
    Details
    ISSN: 1573-0417
    Keywords: West Basin ; crater lake ; salinity ; diatoms ; ostracods ; pollen ; carbonate geochemistry ; Cyclotella caspia ; dissolution ; Australia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Analyses of diatoms, ostracods, pollen and sediment mineralogy from a 524 cm core from a stratified, hypersaline crater lake, West Basin, Victoria, has revealed clear shifts in the lake's water balance and chemistry and the region's climate over the last 10 000 years. Diatom and ostracod analyses reveal lake water salinity changes which are consistent with the conditions suitable for the precipitation of the carbonate and other minerals identified using x-ray diffraction analysis. The fluctuations in lake water balance deduced from diatom and ostracod inferred lake salinity suggest that the lake began to fill at the beginning of the Holocene and was saline and shallow. Toward the mid-Holocene the water levels rose and yet the lake remained largely saline. The late Holocene is marked by a return to more shallow but fluctuating, water conditions. Through the whole period, the regional dryland vegetation was dominated by open sclerophyll woodland. Both the lacustrine and regional environments interpreted here are consistent with those from Holocene records elsewhere in the region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00678023
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  • 10
    Electronic Resource
    Electronic Resource
    A synthesis of post-glacial diatom records from Lake Baikal (1994)
    Springer
    Journal of paleolimnology 10 (1994), S. 213-252 
    Details
    ISSN: 1573-0417
    Keywords: diatoms ; paleolimnology ; palynology ; Holocene ; climate change ; Lake Baikal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The biostratigraphy of fossil diatoms contributes important chronologic, paleolimnologic, and paleoclimatic information from Lake Baikal in southeastern Siberia. Diatoms are the dominant and best preserved microfossils in the sediments, and distinctive assemblages and species provide inter-core correlations throughout the basin at millennial to centennial scales, in both high and low sedimentation-rate environments. Distributions of unique species, once dated by radiocarbon, allow diatoms to be used as dating tools for the Holocene history of the lake. Diatom, pollen, and organic geochemical records from site 305, at the foot of the Selenga Delta, provide a history of paleolimnologic and paleoclimatic changes from the late glacial (15 ka) through the Holocene. Before 14 ka diatoms were very rare, probably because excessive turbidity from glacial meltwater entering the lake impeded productivity. Between 14 and 12 ka, lake productivity increased, perhaps as strong winds promoted deep mixing and nutrient regeneration. Pollen evidence suggests a cold shrub — steppe landscape dominated the central Baikal depression at this time. As summer insolation increased, conifers replaced steppe taxa, but diatom productivity declined between 11 and 9 ka perhaps as a result of increased summer turbidity resulting from violent storm runoff entering the lake via short, steep drainages. After 8 ka, drier, but more continental climates prevailed, and the modern diatom flora of Lake Baikal came to prominence. On Academician Ridge, a site of slow sedimentation rates, Holocene diatom assemblages at the top of 10-m cores reappear at deeper levels suggesting that such cores record at least two previous interglacial (or interstadial?) periods. Nevertheless, distinctive species that developed prior to the last glacial period indicate that the dynamics of nutrient cycling in Baikal and the responsible regional climatic environments were not entirely analogous to Holocene conditions. During glacial periods, the deep basin sediments of Lake Baikal are dominated by rapidly deposited clastics entering from large rivers with possibly glaciated headwaters. On the sublacustrine Academician Ridge (depth = 300 m), however, detailed analysis of the diatom biostratigraphy indicates that diastems (hiatuses of minor duration) and (or) highly variable rates of accumulation complicate paleolimnologic and paleoclimatic reconstructions from these records.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00684034
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  • 11
    Electronic Resource
    Electronic Resource
    Exploratory analysis of paleoecological data using the program CanoDraw (1994)
    Springer
    Journal of paleolimnology 12 (1994), S. 163-169 
    Details
    ISSN: 1573-0417
    Keywords: CANOCO ; CanoDraw ; exploratory data analysis ; diatoms ; canonical correspondence analysis ; loess smoothing ; generalized linear models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract This paper attempts to persuade the reader that methods of direct gradient analysis may serve as a basis for more detailed exploration of the data and that these exploration methods can be also used for checking the appropriateness of the assumptions of the applied ordination method. Generalized linear models and generalized loess smoothing together with several ways of data presentation are used to explore a sample data set.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00678092
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  • 12
    Electronic Resource
    Electronic Resource
    Interpretation of Holocene lake-level change from diatom assemblages in Lake Sidi Ali, Middle Atlas, Morocco (1994)
    Springer
    Journal of paleolimnology 12 (1994), S. 223-234 
    Details
    ISSN: 1573-0417
    Keywords: diatoms ; lake-level ; Middle Atlas ; Morocco ; Holocene ; palaeohydrology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract While palaeohydrological changes in non-outlet lakes provide a key proxy indicator of past climatic fluctuations, for lake systems which have been chemically insensitive, it is necessary to use indicators of water depth rather than salinity to reconstruct their hydro- climatic histories. A study of diatoms in the modern sediments of Sidi Ali, a non-outlet lake in the Middle Atlas of Morocco, has shown a statistically significant correlation between water depth and the ratio of planktonic to littoral diatoms. This relationship is used to calibrate fossil diatom assemblages from a lake sediment core from the same lake to provide a quantitative index of water levels over the pastc. 6500 years. Palaeoecological evidence suggests that climatically induced hydrological variations have dominated the bulk of the mid-late Holocene lake sediment record, with significant human-induced catchment disturbance only occurring during the twentieth century. The pattern of water depth fluctuations suggests that the response time of the regional groundwater system to climatic forcing is 〈100 years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00678022
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  • 13
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    Diatom paleoecology of the Mar Chiquita lagoon delta, Argentina (1994)
    Springer
    Journal of paleolimnology 10 (1994), S. 17-23 
    Details
    ISSN: 1573-0417
    Keywords: diatoms ; paleoecology ; multivariate analysis ; coastal lagoon ; Holocene ; environmental changes ; South America ; Argentina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract A 68 cm thick outcrop of diatomaceous sediments at the head of Mar Chiquita Lagoon on the Argentine coast near Buenos Aires provides evidence of Holocene paleoenvironmental changes related to sea level changes and freshwater input to the lagoon system. Salinity tolerances of extant diatom taxa were used for the reconstruction and multivariate analytical techniques were applied to reduce subjective interpretations of the diatom percentage data. The basal half of the record was deposited before 3000 years ago and fossil diatoms indicate generally freshwater conditions with one fluctuation in mesohalobous diatoms suggesting brackish water conditions at a depth of about 60 cm. Polyhalobous (marine) diatoms characterize the record after 3000 years ago and large numbers of epiphytic diatoms indicate salt marsh environments with episodic seawater fluctuations to supratidal levels. Freshwater diatoms returned at the top of the outcrop, presumably as a result of the restriction of the historic marine inlet to the lagoon and the effects of freshwater inflow to the basin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00683142
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  • 14
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    Effect of Baythroid on nitrogen transformations in soil (1994)
    Springer
    Biology and fertility of soils 17 (1994), S. 173-176 
    Details
    ISSN: 1432-0789
    Keywords: Ammonification ; Cyfluthrin ; Nitrification ; Nitrogen ; N mineralization ; N transformations ; Pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Laboratory incubation experiments were conducted in soil to study the influence of the insecticide Baythroid on immobilization-remineralization of added inorganic N, mineralization of organic N, and nitrification of added NH inf4 su+ -N. Baythroid was applied at 0, 0.4, 0.8, 1.6, 3.2, and 6.4 μg g-1 soil (active ingredient basis). The treated soils were incubated at 30°C for different time intervals depending upon the experiment. The immobilization and mineralization of N were significantly increased in the presence of Baythroid, the effect being greater with higher doses of the insecticide. Conversely, nitrification was retarded at lower doses of Baythroid and significantly inhibited at higher doses. The results of these studies suggest that excessive amonts of insecticide residues affect different microbial populations differently, leading to changes in nutrient cycling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336318
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  • 15
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    Effects of preemergence and postemergence herbicides on urea hydrolysis and nitrification of urea nitrogen in soil (1994)
    Springer
    Biology and fertility of soils 17 (1994), S. 309-313 
    Details
    ISSN: 1432-0789
    Keywords: Herbicides ; Urea hydrolysis ; Nitrification ; Ammonia toxicity ; Nitrification inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influence of 5 and 50 mg active ingredient kg-1 soil of nine preemergence and nine postemergence herbicides on transformations of urea N in soil was studied in samples of two coarse-textured and two fine-textured soils incubated aerobically at 20°C. The effects of each herbicide on soil urea transformations was measured by determining the amounts of urea hydrolyzed and the amounts of NO inf3 sup- and NO inf2 sup- produced at various times after treatment with urea. Applied at the rate of 5 mg active ingredient kg-1 soil, none of the herbicides retarded urea hydrolysis in the four soils used, but four of the postemergence herbicides (acifluorfen, diclofop methyl, fenoxaprop ethyl) retarded urea hydrolysis in the two coarse-textured soils. All the herbicides tested except siduron retarded nitrification in the two coarse-textured soils when applied at 50 mg of urea N active ingredient kg-1 soil, and fenoxaprop ethyl and tridiphane markedly retarded nitrification of urea N in all four of the soils when applied at this rate. One-way analysis of variance and correlation analyses indicated that the inhibitory effects of the 18 herbicides tested on nitrification of urea N in soil increased with a decrease in the organic-matter content and an increase in the sand content of the soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00383987
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  • 16
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    Increase in nitrous oxide production in soil induced by ammonium and organic carbon (1994)
    Springer
    Biology and fertility of soils 18 (1994), S. 1-6 
    Details
    ISSN: 1432-0789
    Keywords: Ammonium ; Denitrification ; Nitrification ; Nitrous oxide ; Organic carbon ; Acetylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We observed that soil cores collected in the field containing relatively high NH inf4 sup+ and C substrate levels produced relatively large quantities of N2O. A series of laboratory experiments confirmed that the addition of NH inf4 sup+ and glucose to soil increase N2O production under aerobic conditions. Denitrifying enzyme activity was also increased by the addition of NH inf4 sup+ and glucose. Furthermore, NH inf4 sup+ and glocose additions increased the production of N2O in the presence of C2H2. Therefore, we concluded that denitrification was the most likely source of N2O production. Denitrification was not, however, directly affected by NH inf4 sup+ in anaerobic soil slurries, although the use of C substrate increased. In the presence of a high substrate C concentration, N2O production by denitrifiers may be affected by NO inf3 sup- supplied from NH inf4 sup+ through nitrification. Alternatively, N2O may be produced during mixotrophic and heterotrophic growth of nitrifiers. The results indicated that the NH inf4 sup+ concentration, in addition to NO inf3 sup- , C substrate, and O2 concentrations, is important for predicting N2O production and denitrification under field conditions.
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    URL: http://dx.doi.org/10.1007/BF00336436
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  • 17
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    Wood-ash fertilization and fire treatments in a Scots pine forest stand: Effects on the organic layer, microbial biomass, and microbial activity (1994)
    Springer
    Biology and fertility of soils 17 (1994), S. 57-63 
    Details
    ISSN: 1432-0789
    Keywords: Coniferous humus ; Ergosterol ; Soil respiration ; Substrate induced respiration ; Metabolic quotient ; Nitrification ; Pinus sylvestris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We studied the reactions of humus layer (F/H) microbial respiratory activity, microbial biomass C, and the fungal biomass, measured as the soil ergosterol content, to the application of three levels of wood ash (1000, 2500, and 5000 kg ha-1) and to fire treatment in a Scots pine (Pinus sylvestris L.) stand. Physicochemical measurements (pH, organic matter content, extractable and total C content, NH 4 + and total N content, cation-exchange capacity, base saturation) showed similarity between the fire-treated plots and those treated with the lowest dose of wood ash (1000 kg ha-1). The ash application did not change the level of microbial biomass C or fungal ergosterol when compared to the control, being around 7500 and 350 μg g-1 organic matter for the biomass C and ergosterol, respectively. The fire treatment lowered the values of both biomass measurements to about half that of the control values. The fire treatment caused a sevenfold fall in the respiration rate of fieldmoist soil to 1.8 μl h-1 g-1 organic matter compared to the values of the control or ash treatments. However, in the same soils adjusted to a water-holding capacity of 60%, the differences between the fire treatment and the control were diminished, and the ash-fertilized plots were characterized by a higher respiration rate compared to the control plots. The glucose-induced respiration reacted in the same way as the water-adjusted soil respiration. The metabolic quotient, qCO2, gradually increased from the control level with increasing applications of ash, reaching a maximum in the fire treatment. Nitrification was not observed in the treatment plots.
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    URL: http://dx.doi.org/10.1007/BF00418673
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    Effect of long-term field exposure of soil to acetylene on nitrification, denitrification, and acetylene consumption (1994)
    Springer
    Biology and fertility of soils 18 (1994), S. 42-48 
    Details
    ISSN: 1432-0789
    Keywords: N2O ; Coated Calcium Carbide ; Acetylene ; Nitrification ; Denitrification ; Soil respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Coated CaC2 is a newly developed product which can supply nitrification-inhibiting quantities of C2H2 (1–10 Pa) to the soil, throughout a cropping season. This method of applying C2H2 to the soil maintains C2H2 in the soil continuously for several months. It is not know whether these low C2H2 concentrations alter soil microbial processes. A field study was initiated to determine the effect of supplying C2H2 to a clay soil, using coated CaC2, on soil respiration, denitrification, nitrification, and C2H2 consumption. The C2H2 consumption rate increased with length of soil exposure to C2H2 (r 2=0.59). The rates of CO2 production (r 2=0.88) and denitrification (r 2=0.86) were both highly correlated with the C2H2 consumption rates. The nitrifier potential decreased to a minimum of 21% of the control after 3 months of C2H2 treatment. After this time, nitrifier activity increased to 41% of the control after 11 months of treatment. This increase was due to increased C2H2 consumption in the soil. After 3 months of continuous application of C2H2 to the soil, the C2H2 concentrations were generally below that necessary to inhibit nitrification. No adaptation to the C2H2 by nitrifiers was found. Repeating these measurements 1 year later showed that soils previously exposed to C2H2 retained their enhanced C2H2 oxidation capacity and the capacity to use C2H2 to increase denitrification. Nitrification potentials remained about 50% lower in soils exposed to C2H2 a year earlier compared to soils not previously exposed to C2H2.
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    URL: http://dx.doi.org/10.1007/BF00336443
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    Diatom succession related to land use during the last 6000 years: a study of a small eutrophic lake in southern Sweden (1993)
    Springer
    Journal of paleolimnology 8 (1993), S. 49-69 
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    ISSN: 1573-0417
    Keywords: South Sweden ; Holocene ; diatoms ; pollen ; eutrophication ; catchment history
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Diatoms, pollen, physical and magnetic analyses of the sediments have been used to reconstruct the development over the last 6000 years of Lake Bussjösjön, a small lake in southern Sweden. Stratigraphic variations in a core of more than 15 m reveal changes in diatom assemblages, which correspond closely to changes in pollen, loss-on-ignition, and magnetic measurements that are related to land use and vegetation changes in the catchment. From ca 6000 BP to 2700 BP, a forest surrounded what was then a slightly eutrophic lake. The sudden appearance of Cyclostephanos dubius (Fricke) Round and several epiphytic/epipsammic diatoms at 2700 BP coincides with deforestation of the catchment (2700 BP to 2500 BP). A change in land use from predominantly pasture to arable land from 1300 BP to 1100 BP caused a high level of soil erosion with a decrease of C. dubius and the increase of Stephanodiscus species. An increase of epiphytic/epipsammic species coincides with increased arable farming and the change from a field-rotation to a crop-rotation system, and shows not only an increase in eutrophication but also changes in water depth. The influence of the catchment through time resulted in a smaller, shallower and eutrophic to hypertrophic lake.
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    URL: http://dx.doi.org/10.1007/BF00210057
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    The history and impact of air pollution at Čertovo Lake, southwestern Czech Republic (1993)
    Springer
    Journal of paleolimnology 8 (1993), S. 211-231 
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    ISSN: 1573-0417
    Keywords: Long-term air pollution ; trace metals ; pollen ; diatoms ; Chrysophyceae ; land-use ; lake acidification ; radionuclides ; Czech Republic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract This multi-disciplinary investigation documents the longterm effects of atmospheric pollution of metals and acids on a geologically sensitive catchment in the Šumava Mountains, southwestern Czech Republic, a region with a long history of human disturbance. A 30 cm long sediment core (I) from Čertovo Lake was analyzed for natural and artifical radionuclides, metals, diatoms, chrysophytes, and pollen in sediments accumulated during the last 200 years. A second core (II), extending to 95 cm, included sediment judged to be free of atmospheric deposition of pollutants associated with the Industrial Revolution. Chronostratigraphic markers include several changes in the pollen assemblages corresponding to well-documented changes in land-use, and distinct distributions of 137Cs, 134Cs and 241Am from weapons testing and the 1986 nuclear accident at Chernobyl, Russia. These markers corroborate the 210Pb dating and, together, produce a reliable chronology extending back nearly to 1800 A.D. Stratigraphic profiles of Cu, Pb, and Zn in Core I are unlike any previously reported in the literature. Concentrations of Cu, Pb, and Zn remain generally above 100, 400, and 200 μg g-1, respectively, for the 200 years represented by Core I. These values are unusually high for sediments from a watershed with no known heavy-metal ore bodies. Accumulation rates for Cu, Pb, and Zn, which include both atmospheric and watershed contributions, are also high (ca 1, 〉 1 and 〉 1 μg cm-2 yr-1, respectively) for the same period, although the anthropogenic contribution of Zn rose from nearly zero at 1800 A.D. The Cu and Pb accumulation rates rose dramatically about 1640 A.D. Accumulation rates of anthropogenically-derived Be, a relatively abundant element in the soft coals of the region, are also elevated by about 0.01 μg cm-2 yr-1 in sediments of this period. Vanadium accumulation rates increased only since 1980 A.D., presumably along with increased consumption of oil. Diatom assemblages illustrate that the lake was acidic (pH between 4.5 and 5) through at least the past 200 years. The pH declined significantly (from ca 5 to 4) between 1960 and 1985 with a slight increase to 4.5 in the last few years. Recent diatom and chrysophyte assemblages suggest high trace metal concentrations, consistent with the present lake-water chemistry.
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    URL: http://dx.doi.org/10.1007/BF00177857
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    Acidification and metal contamination in Whitepine Lake (Sudbury, Canada): a paleolimnological perspective (1993)
    Springer
    Journal of paleolimnology 9 (1993), S. 141-146 
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    ISSN: 1573-0417
    Keywords: diatoms ; chrysophytes ; acidification ; Al ; Ni ; Sudbury ; recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Diatom and chrysophyte assemblages from a sediment core from Whitepine Lake were examined to infer changes in lakewater pH, nickel and aluminum concentrations since pre-industrial times, and to help determine the cause of the virtual extirpation of the lake trout population from the lake during the 1960s and 1970s. Our study indicates that acidification started in the 1920s, and that the maximum inferred pH decline (from 6.2 to 5.8) occurred between 1960 and 1970, coincident with the peak in metal mining and smelting activity in the Sudbury basin. Lakewater [Al] and [Ni], as inferred from our diatom transfer functions, increased. It appears that in addition to the pH decline, elevated [Al] may have played an important role in the decline of lake trout from Whitepine Lake in the 1960s and 1970s. Diatom-inferred lakewater pH and [Ni] have recovered slightly in the recent sediments, which coincides with reductions in emissions that have occurred since the mid-1970s.
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    URL: http://dx.doi.org/10.1007/BF00677515
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    Late glacial — early holocene palaeosalinity in Alberta, Canada — climate implications (1993)
    Springer
    Journal of paleolimnology 8 (1993), S. 149-161 
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    ISSN: 1573-0417
    Keywords: palaeosalinity ; diatoms ; pollen ; late glacial-holocene climate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Palaeolimnological and palynological records from climatically variable central Alberta, Canada, document periods of hypersaline lake conditions indicative of late glacial and early Holocene drought. The sensitivity of palaeolimnological indicators for inferring palaeoclimates is examined by comparing records from two sites at opposite ends of the regional precipitation gradient. Palaeosalinity is identified by the presence of Ruppia pollen, a hypersaline aquatic plant not presently growing in either lake, and diatom assemblages comprising both saline epipelic and planktonic species. Goldeye Lake (52° 27′ N; 116° 12′ W), in the relatively moist Rocky Mountain Foothills remained saline from its inception before ca 14500 years BP until ca 10400 years BP by which time pioneering forests had replaced tundra vegetation; however, freshwater planktonic diatoms dominated ca 12500 to 11500 years BP. However, dating problems endemic to the Foothills region make this chronology only tentative. Moore Lake (54° 30′ N; 110° 30′ N), in dry, east-central Alberta contained Ruppia only between ca 9000 and 6000 years BP. Freshwater diatoms dominated until ca 10000 years BP when they were succeeded by taxa characteristic of saline water. The lake remained saline until ca 6000 years BP. The late glacial period of palaeosalinity at Goldeye Lake occurred because the lake was surrounded by Cordilleran and Laurentide glacial ice, and therefore, cut off from moisture sources until the early Holocene by which time significant ice recession had occurred. Factors causing the second period of salinity remain unknown at this time. In contrast, by the early Holocene, Moore Lake was influenced by drought caused by high summer insolation induced by orbital fluctuations. Freshwater conditions were maintained through the Holocene in the Foothills region of west-central Alberta, but occurred consistently only over the last 4000 years in central and east-central Alberta. The warmer, drier climate during the early Holocene did affect lake levels in at least one headwater Foothills lake (Fairfax Lake — 52° 58′ N; 116° 34′ W). The severity of the drought increased in an easterly direction across the province.
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    Palaeoclimatic studies in South Shetland Islands, Antarctica, based on numerous stratigraphic variables in lake sediments (1993)
    Springer
    Journal of paleolimnology 8 (1993), S. 233-272 
    Details
    ISSN: 1573-0417
    Keywords: lake sediments ; diatoms ; spores ; tephra ; mineralogy ; sediment chemistry ; mosses ; multivariate analysis ; palaeoclimate ; holocene ; Livingston Island ; Antarctica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The hitherto longest found lake sediment sequence on Byers Peninsula, Livingston Island, South Shetland Islands, was analysed with respect to lithology, chronology, diatoms, Pediastrum, pollen and spores, mosses, mineralogy, and sediment chemistry. During the ca. 5000 year long development the sediments were influenced by frequent tephra fall-outs. This volcanic impact played a major role in the lake's history during two periods, 4700–4600 and 2800–2500 BP, but was of importance during the lake's entire history with considerable influence on many of the palaeoenvironmentally significant indicators. The large and complex data set was analysed and zonated with different types of multivariate analysis. This resulted in a subdivision of the sequence into 8 time periods and 21 variables. Redundancy analysis (RDA) of this data set, both without and with the tephra periods, and with 4–6 of the variables as explanatory environmental variables, reveal that climatic/environmental signals are detectable. The palaeoclimatic picture that emerged out of the tephra ‘noise’ suggests that the first 100 years were characterized by mild, humid conditions. This was followed by a less mild and humid climate until ca. 4000 BP when a gradual warming seems to have started, coupled with increased humidity. These mild and humid conditions seem to have reached an optimum slightly after 3000 BP. At ca. 2500 BP a distinct climatic deterioration occurred with colder and drier conditions and long seasons with ice cover. This arid, cold phase probably reached its optimum conditions at ca. 1500 BP, when slightly warmer conditions might have prevailed for a while. Except for the modern sample with rather mild climate, the last 1400 years seem to have been fairly arid and cold, and the effects of the frequent volcanic activity during this period is only vaguely seen in the records.
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    Resting spores of the freshwater diatomsAcanthoceras andUrosolenia (1993)
    Springer
    Journal of paleolimnology 9 (1993), S. 55-61 
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    ISSN: 1573-0417
    Keywords: diatoms ; Acanthoceras ; Attheya ; Rhizosolenia ; Urosolenia ; cysts ; resting spores
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Diatom resting spores are a widespread, but sometimes misconstrued component of siliceous microfossil assemblages. We illustrate and discuss resting spore morphology found in populations ofAcanthoceras andUrosolenia, two widely distributed freshwater genera. Taxonomic status of these genera and the potential paleolimnologic interpretation of resting spores are discussed.
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    URL: http://dx.doi.org/10.1007/BF00680035
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    Temperature dependence of nitrification, denitrification, and turnover of nitric oxide in different soils (1993)
    Springer
    Biology and fertility of soils 15 (1993), S. 21-27 
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    ISSN: 1432-0789
    Keywords: NO production ; NO consumption ; Chemodenitrification ; Nitrification ; Denitrification ; Activation energy ; Temperature optimum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The temperature dependence of the NO production rate and the NO consumption rate constant was measured in an Egyptian soil, a soil from the Bavarian Forest, and a soil from the Donau valley, together with the temperature dependence of the potential rates of ammonium oxidation, nitrite oxidation, and denitrification, and the temperature dependence of the growth of NH inf4 sup+ -oxidizing, NO inf2 sup- -oxidizing, and NO inf3 sup- -reducing bacteria in most probable number assays. In the acidic Bavarian Forest soil, NO production was only stimulated by the addition of NO inf3 sup- but not NH inf4 sup+ . However, NO production showed no temperature optimum, indicating that it was due to chemical processes. Most probable numbers and potential activities of nitrifiers were very low. NO consumption, in contrast, showed a temperature optimum at 25°C, demonstrating that consumption and production of NO were regulated individually by the soil temperature. In the neutral, subtropical Egyptian soil, NO production was stimulated only by the addition of NH inf4 sup+ but not NO inf3 sup- . All activities and most probable numbers showed a temperature optimum at 25° or 30°C and exhibited apparent activation energies between 61 and 202 kJ mol-1. However, a few nitrifiers and denitrifiers were also able to grow at 8° or 50°C. Similar temperature characteristics were observed in the Donau valley soil, although it originated from a temperate region. In this soil NO production was stimulated by the addition of NH inf4 sup+ or of NO inf3 sup- . Both NO production and consumption were stimulated by drying and rewetting.
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    URL: http://dx.doi.org/10.1007/BF00336283
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    Seasonal nitrification measurements with different species of forest litter applied to granite-sand-filled lysimeters in the field (1993)
    Springer
    Biology and fertility of soils 15 (1993), S. 28-34 
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    ISSN: 1432-0789
    Keywords: Plant forest litters ; Biodegradation ; Nitrification ; Nitrogen mineralization ; Litter decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The biodegradation of litter from Festuca silvatica, Abies pectinata, Fagus silvatica, Calluna vulgaris, Picea abies associated with forest brown acid soils or with podzolic soils was studied in field lysimeters filled with granite sand. Analysis of the leachates collected during 2 years made it possible to determine NO inf3 sup- , NH inf4 sup+ , and soluble organic N production in order to investigate the specific influence of the different species of litter on the mineralization of organic N and the variations in nitrification. With Festuca silvatica (grass), active nitrification was observed after the addition of fresh litter in autumn (fall of leaves). Nitrification remained significant in winter, reached a maximum in spring until early summer, and then decreased after mineralization of the easily mineralizable organic N. Nitrification was the major N transformation process in this litter. The addition of fresh litter of Abies pectinata (fir), Fagus silvatica (beech), Calluna vulgaris (heather), and Picea abies (spruce) in autumn induced an inhibition of nitrification during winter and spring. With these litter species, nitrification started again by the end of spring and was at a maximum in summer and autumn until leaf fall. By comparison with Festuca, inhibition observed in winter and spring with the other litter species was definitely due to the chemical composition of the leaves. Simultaneously, a lower C mineralization of these plant material occured. These litter species, in particular Calluna and Picea released leachates containing significant amounts of soluble organic N that were only slightly decomposed. We conclude that NO inf3 sup- production outside of the plant growth period can definitely be involved in soil acidification and weathering processes.
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    Nitrification and nitrifying potential of tropical and subtropical soils (1993)
    Springer
    Biology and fertility of soils 15 (1993), S. 87-90 
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    ISSN: 1432-0789
    Keywords: Nitrification ; Tropical soil ; Subtropical soil ; Nitrifying population
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrification was measured in five different soils (slate alluvial soil, sandstone shale alluvial soil, sandstone shale and slate alluvial soil, red soil, and Taiwan clay). In these soils different lag periods were recorded before the onset of nitrification. Nitrifying activity was highest in sandstone shale alluvial soil and the lowest in acidic red soil. A part from those in the red soil, the numbers of nitrifying bacteria detected were all higher than numbers reported in temperate soils. However, there were no clear relationships between the numbers of nitrifying bacteria and the rate of nitrification in these soils. When soil cores were incubated for 3 weeks, no NO inf2 sup- or NO inf3 sup- was defected in the slate alluvial soil. This was ascribed to denitrification.
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    In situ net N transformations in pine, fir, and oak stands of different ages on acid sandy soil, 3 years after liming (1993)
    Springer
    Biology and fertility of soils 15 (1993), S. 120-126 
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    ISSN: 1432-0789
    Keywords: Lime ; Forest soil ; Nitrification ; N mineralization ; Nitrate leaching ; Pinus sylvestris ; Pseudotsuga menziesii ; Quercus robur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of liming on in-situ N transformations was studied in two stands of different ages of each of Scots pine (Pinus sylvestris L.), Douglas fir [Pseudotsuga menziesii (Mirb.) Franco], and common oak (Quercus robur L.). The stands were located on acid sandy soils in an area with high atmospheric N input. The organic matter of the upper 10-cm layer of the soil, including the forest floor, had a relatively high N content (C: N ratio 〈25) in all stands. Using a sequential core technique, N transformations were measured in both control plots and plots that had been limed 3 years previously with 3 t ha-1 of dolomitic lime. Limed plots had a higher net NO inf3 sup- production and a higher potential for NO inf3 sup- leaching than the controls in all stands except that of the younger oak. Net N mineralization did not differ significantly between limed and control plots in oak stands and younger coniferous stands but was significantly lower in the limed plots of the older coniferous stands. It is concluded that long-term measurements of net N mineralization in limed forest soils are needed to evaluate the effect of liming with respect to the risk of groundwater pollution.
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    Mineralization of nitrogen in fertilizer-acidified lime-amended soils (1993)
    Springer
    Biology and fertility of soils 15 (1993), S. 249-252 
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    ISSN: 1432-0789
    Keywords: N fertilizer requirement ; Nitrification ; Zea mays ; N mineralization ; Lime ; Soil pH ; Nitrate-N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The application of NH inf4 su+ -based fertilizers to soils slowly lowers soil pH, which in turn decreases nitrification rates. Under these conditions nitrification and N mineralization may be reduced. We therefore investigated the impact of liming fertilizer-acidified soils on nitrification and N mineralization. Soil samples were collected in the spring of 1987 from a field experiment, initiated in 1980, investigating N, tillage, and residue management under continuous corn (Zea mays L.). The pH values (CaCl2) in the surface soil originally ranged from 6.0 to 6.5. After 6 years the N fertilizer and tillage treatments had reduced the soil pH to values that ranged between 3.7 and 6.2. Incubation treatments included two liming rates (unlimed or SMP-determined lime requirement), two 15N-labeled fertilizer rates (0 or 20 g N m-2), and three replicates. Field-moist soil was mixed with lime and packed by original depth into columns. Labeled-15N ammonium sulfate in solution was surface-applied and columns were leached with 1.5 pore volumes of deionized water every 7 days over a 70-day period. Nitrification occurred in all pH treatments, suggesting that a ferilizer-acidified soil must contain a low-pH tolerant nitrifier population. Liming increased soil pH values (CaCl2) from 3.7 to 6.2, and increased by 10% (1.5 g N m-2) the amount of soil-derived NO3 --N that moved through the columns. This increase was the result of enhanced movement of soil-derived NO3 --N through the columns during the first 14 days of incubation. After the initial 14-day period, the limed and unlimed treatments had similar amounts of soil N leaching through the soil columns. Lime increased the nitrification rates and stimulated the early movement of fertilizer-derived NO3 --N through the soil.
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    Phosphorus and nitrogen dynamics during field incubations in forest and fallow subarctic soils (1993)
    Springer
    Biology and fertility of soils 16 (1993), S. 243-248 
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    ISSN: 1432-0789
    Keywords: Nitrification ; Mineralization ; Immobilization ; Forest floor ; Subarctic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A knowledge of the nutrient dynamics that occur with land use changes, e.g., in clearing forests for farmland, is useful in choosing the most efficient soil and fertilizer management practices. To determine net in situ P and N mineralization and nitrification rates of forest floor materials and their nutrient value for agricultural crops, plastic bags containing different materials (moss, O horizon, and A horizon) collected from a subarctic black spruce (Picea mariana Mill.) forest were incubated for 2 years in their respective forest horizons and at 7.5 cm depth in a nearby fallow field. Net amounts of P and N mineralized were highest in moss and were similar in forest and field when the temperature and moisture content were similar, but smaller in forest when the water content was higher. Net nitrification was negligible in O and A horizon material but significant in moss during the 2nd year, occurring sooner and producing higher NO inf3 sup- levels in the field (171 mg ha-1) than in the forest (13 mg ha-1). Moss P and N mineralization rates were correlated in the fallow field. Temperature, moisture content, and substrate quality were important factors controlling P and N dynamics of forest floor materials in a subarctic fallow field and native forest. In subarctic regions, incorporation and mineralization of forest floor materials could provide an early source of N and P (70 and 17 kg ha-1, respectively) for succeeding agricultural crops.
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    Effect of cattle slurry in grassland on microbial biomass and on activities of various enzymes (1993)
    Springer
    Biology and fertility of soils 16 (1993), S. 249-254 
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    ISSN: 1432-0789
    Keywords: Microbial biomass ; Soil enzymes ; Nitrification ; Cattle slurry ; Grassland soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We examined the long-term effects of cattle slurry, applied at high rates, on microbial biomass, respiration, the microbial quotient (qCO2) and various soil enzyme activities. In March, June, July, and October 1991, slurry-amended grassland soils (0–10 cm) contained significantly higher levels of microbial biomass, N mineralization and enzyme activities involved in N, P, and C cycling. With microbial biomass as the relative value, the results revealed that the slurry treatment influenced enzyme production by the microbial biomass. High levels of urease activity were the result not only of a larger microbial biomass, but also of higher levels of enzmye production by this microbial biomass. The ratio of alkaline phosphatase and xylanase to microbial biomass was nearly constant in the different treatments. The metabolic quotient (qCO2) declined with increased levels of slurry application. Therefore it appears that microorganisms in slurry-amended soils require less C and energy if there is no competition for nutrients. The results of this study suggest that urease activity, nitrification, and respiration (metabolic quotient) can be used as indicators of environmental stress, produced by heavy applications of cattle slurry.
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    Effect of wax-coated calcium carbide and nitrapyrin on nitrogen loss and methane emission from dry-seeded flooded rice (1993)
    Springer
    Biology and fertility of soils 16 (1993), S. 71-75 
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    ISSN: 1432-0789
    Keywords: Nitrification ; Denitrification ; Nitrification inhibitors ; 15N balance ; Nitrous oxide ; Greenhouse gases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effectiveness of wax-coated calcium carbide (as a slow-release source of acetylene) and nitrapyrin in inhibiting nitrification and emission of the greenhouse gases N2O and CH4 was evaluated in a microplot study with dry-seeded flooded rice grown on a grey clay near Griffith, NSW, Australia. The treatments consisted of factorial combinations of N levels with nitrification inhibitors (control, wax-coated calcium carbide, and nitrapyrin). The rate of nitrification was slowed considerably by the addition of wax-coated calcium carbide, but it was inhibited only slightly by the addition of nitrapyrin. As a result, the emission of N2O was markedly reduced by the application of wax-coated calcium carbide, whereas there was no significant difference in rates of N2O emission between the control and nitrapyrin treatments. Both nitrification inhibitors significantly reduced CH4 emission, but the lowest emission rates were observed in the wax-coated calcium carbide treatment. At the end of the experiment 84% of the applied N was recovered from the wax-coated calcium carbide treatment compared with ∼ 43% for the nitrapyrin and control treatments.
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    URL: http://dx.doi.org/10.1007/BF00336519
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    Effect of acetylene provided by wax-coated calcium carbide on transformations of urea nitrogen applied to an irrigated wheat crop (1993)
    Springer
    Biology and fertility of soils 16 (1993), S. 86-92 
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    ISSN: 1432-0789
    Keywords: Nitrogen immobilization ; Mineralization ; Nitrification ; Nitrification inhibitor ; Acetylene ; CaC2 ; 15N enrichment ; Urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of acetylene (provided by wax-coated calcium carbide, CaC2) on N transformations in a red-brown earth was measured in a field experiment with irrigated wheat by determining the change in the concentration and 15N enrichment of the organic N and mineral N pools with time. The study was conducted in the Goulburn-Murray Irrigation region of south-eastern Australia using 0.3 m by 0.3 m microplots fertilized with 15N-labelled urea (10 g N m-2; 5 atom% 15N). Acetylene was effective in slowing the nitrification of both unlabelled and labelled N. Nitrate derived from the added fertilizer reached a maximum 19 days after sowing in the treatment without CaC2, whereas little nitrate accumulated in the 8 g CaC2 m-2 treatment. There was significant immobilization of the urea N by 19 days after sowing in all treatments, but the extent of immobilization was not affected by the acetylene. The addition of acetylene slowed net mineralization of labelled and unlabelled N from the organic N pool, and resulted in increased accumulation of both unlabelled and labelled N in wheat tops.
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    URL: http://dx.doi.org/10.1007/BF00369408
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    The early holocene hydrosere in a small acid hill-top basin studied using crustacean sedimentary remains (1992)
    Springer
    Journal of paleolimnology 7 (1992), S. 1-22 
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    ISSN: 1573-0417
    Keywords: hydrosere ; natural acidification ; zooplankton ; diatoms ; water level fluctuations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The hydroseral development of a former small lake in Southern Finland was studied by means of subfossil cladoceran remains, diatoms, pollen, plant macrofossils and other sediment data. The diatom analysis shows the lake to have become markedly acid during the Early Holocene. This is reflected in the cladoceran communities in the form of a fall in the proportions of Bosmina longirostris etc. and a reciprocal rise in Bosmina (Eubosmina) longispina, an increase in the proportions of the chydorid species indicative of acidity, and the appearance of certain new morphotypes. The concentrations of both planktonic and littoral species and the numbers of such species increase with acidification. Advancement in the hydroseral succession is reflected in the disappearance of benthic species from the chydorid communities and a pronounced increase in exclusively phytophile species. Sedimentation and the drop in water levels are seen to have led to a spread of helophytes and floating-leaved plants over the water body around 6500–7000 B.P., and a vegetation-filled swamp was created at the site. The zooplankton was practically exterminated, but the concentrations of littoral cladocerans reached their peak at this point. The basin became overgrown completely at the beginning of the Subboreal chronozone (approx. 4600–4800 B.P.), simultaneously with the low-water phase observed in many lakes. It became covered with a Sphagnum stand, and this in turn led to complete destruction of the cladoceran communities. The planktonic/littoral ratio among the Cladocera closely reflected the relation between open water and the macrophyte zone as a function of time. Climatically induced rises and falls in water level are shown to have played a significant role in promoting the advancement of the hydroseral succession.
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    URL: http://dx.doi.org/10.1007/BF00197028
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    Differential diatom dissolution in Late Quaternary sediments from Lake Manyara, Tanzania: an experimental approach (1992)
    Springer
    Journal of paleolimnology 7 (1992), S. 235-251 
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    ISSN: 1573-0417
    Keywords: diatoms ; dissolution ; transfer functions ; taphonomy ; Lake Manyara ; Tanzania ; Late Quaternary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Diatom dissolution in saline lakes represents an important obstacle to the quantitative reconstruction of water chemistry and climate from lake sediment archives. This problem is here approached experimentally by artificially dissolving diatom-bearing core sediment from Lake Manyara, Tanzania. Manyara holds one of the longest continuous palaeolimnological records from tropical Africa although its interpretation is based on a fragmentary diatom record due to frustule dissolution. These experiments have revealed clear changes in assemblage composition as dissolution operated differentially with respect to diatom taxa. Differential dissolution has considerable impact on the water chemistry estimates derived from transfer functions. Taphonomy, rather than environmental change, may have been responsible for minor fluctuations in the diatom assemblages from Manyara, although major palaeohydrological changes during the Late Pleistocene and Early Holocene can be identified. Particularly well represented by MANE-87 is a period of intermediate lake level between 27 500 and 23 000 14C yr BP which has regional palaeohydrological significance.
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    URL: http://dx.doi.org/10.1007/BF00181716
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    Fossil diatoms and the mid to late holocene paleolimnology of Lake Turkana, Kenya: a reconnaissance study (1992)
    Springer
    Journal of paleolimnology 7 (1992), S. 23-35 
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    ISSN: 1573-0417
    Keywords: diatoms ; paleolimnology ; paleoclimatology ; sediments ; radiocarbon chronology ; East Africa (Kenya)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract A 12 m sediment core recovered from the south basin of Lake Turkana, northwestern Kenya, reveals four major diatom assemblages that span approximately 5450 to 1070 years BP based on AMS radiocarbon analyses. The oldest assemblage, Zone D (5450 to 4850 yr BP), is dominated by Melosira nyassensis and Stephanodiscus spp. and is interpreted to reflect higher lake levels, fresher water and more variable seasonal mixing of the water column than the modern lake. Melosira dominates the assemblage in Zone C (4850 to 3900 yr BP) with some Surirella engleri and Stephanodiscus. This assemblage indicates a continuation of relatively high lake levels and seasonal mixing of a stratified lake. The brief peak of Surirella, interpreted as benthic, suggests an episode of slightly lower lake level. Thalassiosira rudolfi and Surirella predominate since the beginning of Zone B (3900 to 1900 yr BP), reflecting a decrease in lake level and increase in water column salinity. Increasing dominance of Surirella in Zone A (1900 to 1070 yr BP) may suggest that the lake continued to decrease in depth. Salinity probably rose to levels comparable with the modern lake. These results are consistent with paleoclimatic interpretations based on carbonate abundance, lamination thickness, oxygen isotope and bulk geochemistry profiles from this core and cores recovered from the north basin. It extends the known paleolimnology beyond 4000 yr BP of the earlier research to 5450 yr BP and into the early to mid Holocene pluvial phase in northern intertropical east Africa.
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    Relationships between sedimentary diatom assemblages and lakewater pH values in the Experimental Lakes Area (1992)
    Springer
    Journal of paleolimnology 7 (1992), S. 145-156 
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    ISSN: 1573-0417
    Keywords: Experimental Lake Area (ELA) ; paleolimnology ; inferred pH ; diatoms ; acidification ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Relationships between sedimentary diatom assemblages and lakewater pH values from 36 lakes and experimentally acidified Lake 223, in the Experimental Lakes Area, were analyzed. The relationships were used to assign diatoms in the 36 lakes into pH preference groupings. Based on their regional distribution Cyclotella stelligera and Tabellaria flocculosa strain IIIp were categorized as pH indifferent, in comparison to other areas were they have been categorized as acidophilic. Two models were then applied to calculate transfer coefficients which were used to calculate diatom-inferred pH values for Lake 223. Index B and a multiple linear regression of the pH groupings yielded similar correlations (r2 0.82 and 0.84 respectively, p=0.0001). The multiple linear regression inferred a pH of 5.36 for acidified Lake 223 compared to a measured pH of 5.46.
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    Carbon and nitrogen mineralization and ammonia volatilization from fresh, aerobically and anaerobically treated pig manure during incubation with soil (1992)
    Springer
    Biology and fertility of soils 13 (1992), S. 135-141 
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    ISSN: 1432-0789
    Keywords: Ammonia loss ; CO2-C evolution ; Combined first- and zero-order kinetics ; N-immobilization ; Nitrification ; Non-linear regression ; Priming effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We studied the decomposition of aerobically and anaerobically treated pig manure during a 2-month incubation with soil. The manure samples had not been in contact with straw or with animal urine. The aerobically decomposed manure proved to be the most stable (23% C mineralization), followed by fresh (75%) and anaerobically treated manure (105%, priming effect). The course of mineralization fitted combined first- and zeroorder kinetics. In the anaerobically treated manure, 76% of NH 4 + -N was immobilized during the initial incubation phase, followed by a slow linear mineralization. In the aerobically treated manure there was a slow linear mineralization after 5 days, and in the fresh material, a slightly faster linear mineralization after 6 days. Total mineralized N was very similar after 2 months (12%) in all treatments. Total NH3 losses were highest from the anaerobically treated manure (14%), reflecting a higher NH 4 + content with N mineralization following first-order kinetics. Relating NH3 losses to the initial NH 4 + content showed that all NH3 in the aerobically treated manure was volatilized, whereas only 28% was volatilized from the fresh and the anaerobically treated manure.
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    Effects of long-term 2,4-D application on microbial populations and biochemical processes in cultivated soil (1992)
    Springer
    Biology and fertility of soils 13 (1992), S. 187-191 
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    ISSN: 1432-0789
    Keywords: Dehydrogenase activity ; DHA ; Microbial biomass ; Microbial populations ; 2,4-D ; Nitrification ; Soil respiration ; Urease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of 15 years of field applications of 2,4-dichlorophenoxy acetate (2,4-D) on soil microbial population and biochemical processes were studied in a field cropped with maize followed by potatoes. Amine or ester formulations at the rate of 0.95 kg 2,4-D per hectare applied in May and October every year. Fungal, bacterial, and actinomycete populations, and microbial biomass C and N were reduced by the 2,4-D treatment, the reduction being more marked where the ester was used. N mineralization, nitrification, and potentially mineralizable N were reduced by the 2,4-D ester only, while urease activity was depressed by both formulations. Dehydrogenase activity and soil microbial respiration tended to be temporarily increased by the amine, but were reduced substantially by the ester, indicating that the ester probably interfered with nutrient cycling.
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    Nitrogen turnover rates in a riparian fen determined by 15N dilution (1992)
    Springer
    Biology and fertility of soils 14 (1992), S. 230-236 
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    ISSN: 1432-0789
    Keywords: N mineralization ; Assimilation ; Nitrification ; NO in3 sup- reduction ; Riparian fen ; 15N substrates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Gross rates of N mineralization, assimilation, nitrification, and NO in3 sup- reduction were determined in soil from a wet riparian fen by 1-day incubations of soil cores and slurries with 15N-labelled substrates. N mineralization transformed 0.1% of the total organic N pool daily in the soil cores, of which 25% was oxidized through autotrophic nitrification and 53%–70% was incorporated into microorganisms. N mineralization and nitrification were markedly inhibited below 5 cm in soil depth. At least 80% of the NO in3 sup- reduction in aerated cores occurred through dissimilatory processes. Dissimilatory reduction to NH in4 sup+ (DNRA) occurred only below 5 cm in depth. The results show that NH in4 sup+ oxidation was limited by available substrate and was itself a strong regulator of NO in3 sup- -reducing activity. NO in3 sup- reduction was significantly increased when the soil was suspended under anaerobiosis; adding glucose to the soil slurries increased NO in3 sup- reduction by 2.4–3.7 times. Between 3% and 9% (net) of the added NO in3 sup- was reduced through DNRA in the soil slurries. The highest percentage was observed in soil samples from deeper layers that were pre-incubated anaerobically.
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    A palaeoenvironmental study of Fairfax Lake, a small lake situated in the rocky mountain foothills of west-central Alberta (1991)
    Springer
    Journal of paleolimnology 6 (1991), S. 1-15 
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    ISSN: 1573-0417
    Keywords: diatoms ; sedimentary pigments ; pollen ; stomatocysts ; lake history ; Fairfax Lake ; Alberta ; Canada
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Fairfax Lake is a small, oligotrophic to mesotrophic headwater lake situated in the Foothills of the Rocky Mountains of west-central Alberta (Latitude 52° 58′ N; Longitude 116° 34′ W). Through acquisition of a sediment core, and analyses of the diatoms, chrysophyte stomatocysts, pollen and sedimentary pigments, including myxoxanthophyll and oscillaxanthin, a palaeoenvironmental history of the lake has been determined. The sedimentary record spans ca. 13 200 years. An open tree-less vegetation existed in the region ca. 13 200–ca. 11 600 years BP. Maximum oscillaxanthin and myxoxanthophyll concentrations, hence the largest blue-green algal populations, occurred during the same interval. With increasing temperature pioneering parkland vegetation appeared ca. 11 600 years BP but was replaced ca. 10 100 years BP by spruce forest. Pine appeared ca. 7800 years BP and this marked the development of the present day montane boreal forest. Diatoms were not found until ca. 11 255 years BP. Benthic taxa dominated but by ca. 10 100 years BP planktonic taxa had become more prominent. Lake levels are interpreted as having risen, and the lake water was probably more transparent. Maximum chlorophyll and total carotenoid concentrations occur ca. 11 255 to ca. 7000 years BP corresponding to the warm early to mid-Holocene period. Lake nutrient levels appear to have been higher prior to ca. 7000 years BP, and the lake has changed from being eutrophic during the early Holocene to its present status as an oligotrophic to mesotrophic lake. Subtle hydrological changes have also occurred in the catchment as water levels do not appear to have remained constant.
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    Mid and late holocene diatoms from ‘Water Supply Lake’, Baffin Island, N.W.T., Canada (1991)
    Springer
    Journal of paleolimnology 6 (1991), S. 199-204 
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    ISSN: 1573-0417
    Keywords: paleolimnology ; diatoms ; Baffin Island ; Arctic Canada ; Fragilaria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Diatom analyses from a 40 cm sediment core from ‘Water Supply Lake’, northeastern Baffin Island, reveal 67 taxa of primarily benthic forms, strongly dominated by small Fragilaria spp. No major stratigraphic changes are noted in the diatom floral record, which encompasses the last 7000 years. In the uppermost 2 cm, there are increases in: a) F. virescens var. subsalina, b) the ratio of symmetric: asymmetric valves of F. construens, and c) species richness. These are interpreted as reflecting anthropogenic modifications of the lake (chlorination and deepening) associated with its use as a source of water for the community of Pond Inlet since 1979.
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    A paleolimnological record of anthropogenic disturbances at Holmes Lake, Adirondack Mountains, New York (1991)
    Springer
    Journal of paleolimnology 5 (1991), S. 255-262 
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    ISSN: 1573-0417
    Keywords: paleolimnology ; diatoms ; lake acidification ; logging ; watershed disturbance ; Adirondacks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Holmes Lake, Adirondack Mountains, New York, is a clear-water acidic lake that was treated with lime in 1983 to permit stocking of trout. Diatom assemblages in dated sediments reflect three anthropogenic modifications of the lake ecosystem: 1) assemblages from the mid- and late 1800's are associated with historical and sedimentary records of forest clearance, and indicate slightly increased pH; 2) acidobiontic species increase in sediments from the mid-1900's, a period of local reforestation and regionally increasing anthropogenic acid loading; 3) liming caused large increases of circumneutral periphytic species in the first growing season, and decreases of acidobiontic species by the second.
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    The late Cenozoic diatom stratigraphy and paleolimnology of Tule Lake, Siskiyou Co. California (1991)
    Springer
    Journal of paleolimnology 6 (1991), S. 205-255 
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    ISSN: 1573-0417
    Keywords: paleolimnology ; paleoclimate ; diatoms ; Cenozoic ; northern California
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Lacustrine diatoms are diverse, well preserved and abundant in cores of lake sediment to 334 m depth near the town of Tulelake, Siskiyou County, northern California. The cores have been dated by radiometric, tephrochronologic and paleomagnetic techniques, which indicate a basal age of about 3 million years (Ma) and a nearly continuous depositional record for the Tule Lake basin for the last 3 million years (My). Fossil diatoms document the late Cenozoic paleolimnologic and paleoclimatic history for the northwestern edge of the Basin and Range Province. During the last 3 My, Tule Lake was typically a relatively deep, extensive lake. The Pliocene is characterized by a diatom flora dominated by Aulacoseira solida suggesting more abundant summer precipitation and warmer winters. Increases in ‘Fragilaria’ at 2.4 Ma and between 2.0 and 1.7 Ma imply cooler summers that correlate to glacial environments recorded elsewhere in the world. Stephanodiscus niagarae and ‘Fragilaria’ species dominate the Pleistocene. Benthic diatoms of alkalineenriched, saline waters occur with S. niagarae between 100 and 40 m depth (0.90–0.14 Ma). Tephrochronology indicates slow deposition and possible hiatuses between about 0.6 and 0.2 Ma. Overall, the Pleistocene diatom flora reflects cooler and sometimes drier climates, especially after major glaciations began 0.85 Ma. The chronology of even-numbered oxygen isotope stages approximately matches fluctuations in the abundance in ‘Fragilaria’ species since 1 Ma, suggesting that glacial periods at Tule Lake were expressed by relatively cool summers with enhanced effective moisture. Interglacial periods are represented by variable mixtures of freshwater planktonic and benthic alkaline diatom assemblages that suggest seasonal environments with winter-spring precipitation and summer moisture deficits. Glacial-interglacial environments since 150 ka were distinct from, and more variable than, those occurring earlier. The last full glacial period was very dry. Aulacoseira ambigua characterizes the late glacial and early Holocene record of Tule Lake. Its distribution indicates that warmer and wetter climates began about 15 ka in this part of the Great Basin. Fluctuations in diatom concentration suggests a 41000-yr. cycle between 3.0 and 2.5 Ma and 100000-yr. cycles after 1.0 Ma. In the late Pliocene and early Pleistocene, Aulacoseira solida percentages wax and wane in an approximately 400000-yr. cycle. The apparent response of Tule Lake diatom communities to orbitally induced insolation cycles underscores the importance of this record for the study of late Cenozoic paleoclimate change. The diatom stratigraphy records the evolution and local extinction of several species that may be biochronologically important. Stephanodiscus niagarae first appeared and became common in the Tule Lake record shortly after 1.8 Ma. Stephanodiscus carconensis disappeared about 1.8 Ma, while Aulacoseira solida is rare in the core after about 1.35 Ma. Cyclotella elgeri, a diatom characteristic of some outcrops referred to the Yonna Formation (Pliocene), is common only near the base of the core at an age of about 3 Ma. Detection of local extinctions is complicated by reworking of distinctive species from Pliocene diatomites surrounding Tule Lake. A new species, Aulacoseira paucistriata, is described from Pliocene lake deposits in the Klamath Basin.
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    Oscillaxanthin and myxoxanthophyll in two cores from Lake Wabamun, Alberta, Canada (1991)
    Springer
    Journal of paleolimnology 5 (1991), S. 127-137 
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    ISSN: 1573-0417
    Keywords: oscillaxanthin ; myxoxanthophyll ; Lake Wabamun ; Alberta ; diatoms ; sediment cores
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract A sedimentary blue-green algal record has been investigated through measurement of myxoxanthophyll and oscillaxanthin in two cores taken from deep and shallow sites in Lake Wabamun, Alberta, Canada (Longitudes 114° 26′ and 114° 44′ W; Latitudes 50° 30′ and 50° 35′ N). Blue-green algae have been a component of the algal flora of this lake throughout the Holocene period. Myxoxanthophyll and oscillaxanthin maxima occur in early Holocene sediments (ca. 9000 years BP), whereas oscillaxanthin concentrations are high between 7000 and 3800 years BP. High oscillaxanthin levels suggest that a phytoplankton assemblage, which included Oscillatoria spp., existed during this latter period and the lake was more eutrophic than at present. Decreases in the number of planktonic diatoms in the core from the deep site (Seba core) appear to be related to increased eutrophy, increased salinity, and sediment redistribution as well as possible competition with Oscillatoria. That the lake has been less productive during the last 2500 years in supported by the diatom record, the diatom: chrysophyte statospore (stomatocyst) ratio and concentrations of the blue-green algal pigments. In the core from the shallow site (Moonlight Bay) concentrations of blue-green algal pigments are initially high, which along with the diatom assemblage, indicates a younger basal age of the sediments. It is possible that benthic blue-green algae contributed significantly to sedimentary pigment concentrations in the Moonlight Bay core. Major fluctuations in the Osc: Myx ratio, particularly in the Seba core, casts some doubt upon the usefulness of this ratio, and suggests that it is not degradation-independent.
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    Field calibration and performance of sediment traps in a eutrophic holomictic lake (1991)
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    Journal of paleolimnology 5 (1991), S. 175-188 
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    ISSN: 1573-0417
    Keywords: sediment traps ; aspect ratio ; resuspension ; lake sediment accumulation rate ; diatoms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract In wind-stressed and unstratified Lough Neagh low aspect ratio sediment traps, which allow for internal resuspension, collected sediment at a rate close to the natural sediment accumulation rate inferred from dated sediment cores. High aspect ratio traps grossly overestimated the natural rate of sediment accumulation as did, but to a lesser extent, burial rate measurements on an artificial stratigraphic marker. The former type of trap deployed over long exposure periods is therefore recommended as providing the best estimate of net downward particle flux in lakes such as Lough Neagh. However, it is emphasized that all sediment trap types, when operated in shallow turbulent lakes, will to a greater or lesser extent be ‘contaminated’ by secondary or redeposited material and so will not provide a direct measure of primary sedimentation. Use of tube traps in lakes such as Lough Neagh should not, however, be discounted since they can provide a record of the quality of sedimenting material through time.
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    Palaeolimnology of the Upper Lerma Basin, Central Mexico: a record of climatic change and anthropogenic disturbance since 11 600 yr BP (1991)
    Springer
    Journal of paleolimnology 5 (1991), S. 197-218 
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    ISSN: 1573-0417
    Keywords: palaeolimnology ; Quaternary ; diatoms ; Mexico ; climatic change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The Upper Río Lerma valley, Estado de México, is a high-altitude (2575 m a.s.l.) basin floored by Quaternary alluvial, lacustrine and pyroclastic deposits. Two pits were dug in the swampy bed of the recently drained L. Chiconahuapan. Ten 14C dates have been obtained from these profiles, which consist of diatomaceous organic lake muds and peats with intercalated tephras. The oldest unit is the Upper Toluca Pumice (Tripartite Ash), dated 11 580±70 yr BP. Analyses of sediment chemistry, loss-onignition, mineral-magnetic variations and subfossil diatom assemblages provide evidence of environmental changes since this date. Alkaline ponds or freshwater lakes developed during the intervals 9000–6000, 6000–5500, 3600–1400 and 800–0 yr BP, and acidic marshes or bogs during the intervening dry episodes. An important phase of accelerated erosion, beginning around 3100 yr BP and culminating around 1400–700 yr BP, appears to have been associated with human disturbance of the basin soils.
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    Variability in diatom and chrysophyte assemblages and inferred pH: paleolimnological studies of Big Moose Lake, New York, USA (1991)
    Springer
    Journal of paleolimnology 5 (1991), S. 267-284 
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    ISSN: 1573-0417
    Keywords: variability ; diatoms ; chrysophytes ; acidification ; paleolimnology ; Adirondacks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We measured variability in the composition of diatom and chrysophyte assemblages, and the pH inferred from these assemblages, in sediment samples from Big Moose Lake, in the Adirondack Mountains of New York. Replicate samples were analyzed from (1) a single sediment core interval, (2) 12 different intervals from each of 3 separate cores, and (3) 10 widely spaced surface sediment samples (0–1 cm). The variability associated with sample preparation (subsampling, processing, and counting) was relatively small compared to between-core and within-lake variability. The relative abundances of the dominant diatom taxa varied to a greater extent than those of the chrysophyte scale assemblages. Standard deviations of pH inferences for multiple counts from the same sediment interval from diatom, chrysophyte, and diatom plus chrysophyte inference equations were 0.04 (n=8), 0.06 (n=32), and 0.06 (n=8) of a pH unit, respectively. Stratigraphic analysis of diatoms and chrysophytes from three widely spaced pelagic sediment cores provided a similar record of lake acidification trends, although with slight differences in temporal rates of change. Average standard deviations of pH inferences from diatom, chrysophyte and diatom plus chrysophyte inference equations for eight sediment intervals representing similar time periods but in different cores were 0.10, 0.20, and 0.09 pH unit, respectively. Our data support the assumption that a single sediment core can provide an accurate representation of historical change in a lake. The major sources of diatom variability in the surface sediments (i.e., top 1.0 cm) were (1) differences in diatom assemblage contributions from benthic and littoral sources, and (2) the rapid change in assemblage composition with sediment depth, which is characteristic of recently acidified lakes. Because scaled chrysophytes are exclusively planktonic, their spatial distribution in lake sediments is less variable than the diatom assemblages. Standard deviations of pH inferences for 10 widely spaced surface sediment samples from diatom, chrysophyte and diatom plus chrysophyte inference equations were 0.21, 0.09, and 0.16 of a pH unit, respectively.
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    Siliceous microfossil succession in the recent history of Green Bay, Lake Michigan (1991)
    Springer
    Journal of paleolimnology 6 (1991), S. 123-140 
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    ISSN: 1573-0417
    Keywords: diatoms ; paleolimnology ; eutrophication ; Great Lakes ; Green Bay ; Lake Michigan ; North America
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Quantitative analysis of siliceous microfossils in a 210Pb dated core from Green Bay of Lake Michigan shows clear evidence of eutrophication, but a different pattern of population succession than observed in the main deposition basins of the Great Lakes. Sediments deposited prior to extensive European settlement (ca A.D. 1850) contain high relative abundance of chrysophyte cysts and benthic diatoms. Quantity and composition of microfossils deposited during the pre-settlement period represented in our core is quite uniform, except for the 30–32 cm interval which contains elevated microfossil abundance and particularly high levels of attached benthic species. Total microfossil abundance and the proportion of planktonic diatoms begins to increase ca 1860 and rises very rapidly beginning ca 1915. Maximum abundance occurs in sediments deposited during the 1970's, with a secondary peak in the late 1940's — early 1950's. Increased total abundance is accompanied by increased dominance of taxa tolerant of eutrophic conditions, however indigenous oligotrophic taxa, particularly those which are most abundant during the summer, are not eliminated from the flora, as in the lower Great Lakes. It appears that a combination of silica resupply from high riverine loadings and replacement of indigenous populations by periodic intrusions of Lake Michigan water allow sequential co-existence of species usually exclusively associated with either eutrophic or oligotrophic conditions.
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    Decomposition of sawdust and bark treated with cellulose-decomposing microorganisms (1991)
    Springer
    Biology and fertility of soils 11 (1991), S. 105-110 
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    ISSN: 1432-0789
    Keywords: Compost ; Sawdust ; Bark ; Cellulolysis ; Ammonification ; Nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The decomposition of coniferous sawdust and bark with added N and P was studied in relation to its capacity to serve as a substrate for plant growth. With sawdust as a substrate, there was more microbial biomass, greater CO2 evolution, more ammonification and more actinomycetes but less nitrification and less fungi compared with bark. All groups and activities were greater in sawdust and bark compared with soil used as the substrate. Inoculation with cellulolytic strains of Bacillus sp. Cephalosporium sp. and Streptomyces sp. sometimes increased these activities but only marginally. The derived sawdust and bark composts increased the yields of tomato compared with soil to which the same nutrients had been added.
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    Variations in the rates of nitrification and denitrification during the growth of potatoes (Solanum tuberosum L.) in soil with different carbon inputs and the effect of these inputs on soil nitrogen and plant yield (1991)
    Springer
    Biology and fertility of soils 11 (1991), S. 157-162 
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    ISSN: 1432-0789
    Keywords: Carbon ; Denitrification ; Immobilisation ; Mineralisation ; Nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A potato crop (Solanum tuberosum L. cv. Maris piper) was grown in a soil to which N was added, as NH4NO3, with or without added C, as sucrose or straw. Shortly after amendment the soil, in all treatments, contained only relatively low levels of mineral N. However, these levels increased later. The increase, which was greatest in the absence of added C and least with added sucrose, occurred before the emergence of the plant canopy. The addition of C to the soil had no effect on plant yield, measured either as dry matter or total N content. The potential nitrification rate was high early in the season, and decreased significantly as the plants developed. The potential denitrification rate showed two significant peaks in activity, possibly related to plant development, the first to the development of new roots and the second to root senescence. It seems probable that the amount of C released by the potato plants was only about one-quarter of that required for the maximum microbial activity.
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    Inhibition of nitrification in soil by gaseous hydrocarbons (1991)
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    Biology and fertility of soils 11 (1991), S. 231-233 
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    ISSN: 1432-0789
    Keywords: Nitrification ; Hydrocarbons ; Methane ; Ethane ; Ethylene ; Acetylene ; Nitrosomonas europaea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Recent work has shown that gaseous hydrocarbons such as methane, ethane, and ethylene are competitive inhibitors of the monooxygenase enzyme responsible for oxidation of ammonia by chemoautotrophic nitrifying microorganisms such as Nitrosomonas europaea. Because methane, ethane, and ethylene are produced by microbial activity in soil, we studied the possibility that they may inhibit oxidation of ammonia by the nitrifying soil microorganisms. We found that all three of these gaseous hydrocarbons inhibited nitrification in soil and that their ability to inhibit nitrification decreased in the order: ethylene 〉 ethane 〉 methane. Ethylene was much more effective than ethane or methane for inhibiting nitrification of ammonium in soil, but it was much less effective than acetylene, and it seems unlikely that the amounts of ethylene produced in soils will be sufficient to cause significant inhibition of nitrification by soil microorganisms.
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    A simple gas chromatographic approach to evaluate CO2 release, N2O evolution, and O2 uptake from soil (1991)
    Springer
    Biology and fertility of soils 12 (1991), S. 1-4 
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    ISSN: 1432-0789
    Keywords: Microbial activity ; Gas chromatographic analysis ; Soil atmosphere ; N2O release ; CO2 evolution ; O2 uptake ; Denitrification ; Nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We have developed a simple method for the determination of gaseous compounds that reflect microbial activity in soil, as affected by factors such as the presence of an organic amendment (peat) or a variation in soil moisture. The method is based on a gas chromatographic analysis of the headspace of vials containing the soil under examination. A single gas chromatograph can detect up to 10 different gases. As expected, after peat was added to the soil, CO2 evolution and O2 uptake increased significantly. Positive relationships were found between the evolution of N2O, and soil moisture and the amount of peat added to the soil. Both the these variables influenced the CO2:O2 ratio. The results given by this method show high reproducibility.
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    Coupled nitrification-denitrification associated with liquid manure in a gel-stabilized model system (1991)
    Springer
    Biology and fertility of soils 12 (1991), S. 19-27 
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    ISSN: 1432-0789
    Keywords: Manure ; Nitrification ; Denitrification ; Silica gel ; Phospholipids ; Microbial biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Following the application of liquid manure to soil, the development of the two processes, nitrification and denitrification, was studied in a two-phase model system. A saturated mixture of manure and soil, stabilized with silica gel, was overlain by an aerobic soil phase. Profiles of the redox potential pH, inorganic N, dissolved organic C, nitrification and denitrification potentials, and phospholipid concentrations for an estimate of microbial biomass were measured during a 20-day period. NH 4 + diffusing into the aerobic soil was oxidized within 10 mm of the interface, but with only a small accumulation of NO 2 - and NO 3 - . It was estimated that N equivalent to approximately 70% of the NH 4 + originally present in the manure was lost through coupled nitrification-denitrification. The potentials for nitrification and denitrification increased 40-and 20-fold, respectively, around the interface. Maximum values were recorded after 14 days. Within 0–5 mm of the anaerobic zone, apparent generation times for NH 4 + -oxidizing bacteria of 1.1–1.8 days were estimated between day 1 and day 7. The phospholipid concentration profiles suggested that the biomass within 2 mm on either side of the interface was stimulated throughout the 20-day period.
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    Effects of organic manure on nitrification in arable soils (1991)
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    Biology and fertility of soils 12 (1991), S. 147-153 
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    ISSN: 1432-0789
    Keywords: Nitrification ; Integrated farming ; Conventional farming ; Ammonification ; Fluorescence antibody microscopy ; Nitrobacter spp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The production of nitrate by the process of nitrification is highly dependent on other N-transforming processes in the soil. Hence, changes in the type of N compound applied to enrich agricultural soils may affect the production of nitrate. The size and activity of the chemolithotrophic bacterial community were studied in an integrated farming system, with increased inputs of organic manure and reduced inputs of mineral nitrogenous fertilizer, versus conventional farming. The integrated farming had a positive effect on potential nitrifying activity, but not on the numbers of chemolithotrophic nitrifying bacteria as determined by a most probable number technique or by fluorescence antibody microscopy. Cells of the recently described nitrite-oxidizing species Nitrobacter hamburgensis and Nitrobacter vulgaris were just as common as the cells of the well known species Nitrobacter winogradskyi. It was concluded that nitrification is stimulated by integrated farming, presumably by an increased mineralization of ammonium which is not immediately consumed by the crop or immobilized in the heterotrophic microflora of the soil. Since nitrifying bacteria are involved in the production of NO and N2O, integrated farming with the application of manure may favour the production of noxious N-oxides.
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    Urea losses in flooded soils with established oxidized and reduced soil layers (1990)
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    Biology and fertility of soils 9 (1990), S. 283-287 
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    ISSN: 1432-0789
    Keywords: Nitrogen transformations ; Flooded soil ; Nitrogen loss ; Nitrification ; Dentitrification ; Urea ; NH3 volatilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Laboratory batch incubation experiments were conducted to determine in fate of urea-15N applied to floodwater of four rice soils with established oxidized and reduced soil layers. Diffusion-dependent urea hydrolysis was rapid in all soils, with rates ranging from 0.0107 to 0.0159 h-1 and a mean rate of 0.0131 h-1. Rapid loss of 53%–65% applied urea-15N occurred during the first 8 days after application, primarily by NH3 volatilization. At the end of 70 days, an additional 20%–30% of applied urea-15N was lost, primarily through nitrification-denitrification processes. The soil types showed significant differences in total applied urea-15 recovery. Conversion of urea-15N to N2-15N provided direct evidence of urea hydrolysis followed by nitrification-denitrification in flooded soils.
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    Paleolimnology of McNearney lake: an acidic lake in northern Michigan (1990)
    Springer
    Journal of paleolimnology 3 (1990), S. 13-34 
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    ISSN: 1573-0417
    Keywords: paleolimnology ; diatoms ; diatom-inferred pH ; trace metals ; sulfur ; lakewater chemistry ; seepage lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract McNearney Lake is an acidic (pH=4.4) lake in the Upper Peninsula of Michigan with low acid neutralizing capacity (ANC=-38 μeq L-1) and high SO inf4 sup2- and aluminium concentrations. Oligotrophy is indicated by high Secchi transparency and by low chlorophyll a, total phosphorus, and total nitrogen concentrations. The lake water is currently acidic because base cations are supplied to the lake water at a low rate and because SO inf4 sup2- from atmospheric deposition was not appreciably retained by the lake sediments or watershed and was present in the water column. This interdisciplinary paleolimnological study indicates that McNearney Lake is naturally acidic and has been so since at least 4000 years B.P., as determined from inferred-pH techniques based on contemporary diatom-pH relationships. Predicted pH values ranged from 4.7 to 5.0 over the 4000-year stratigraphy. Considerable shifts in species composition and abundance were observed in diatom stratigraphy, but present-day distributions indicate that all abundant taxa most frequently occur under acidic conditions, suggesting that factors other than pH are responsible for the shifts. The diatom-inferred pH technique as applied to McNearney Lake has too large an uncertainly and is not sensitive enough to determine the subtle recent changes in lakewater pH expected from changes in atmospheric deposition because: (1) McNearney Lake has the lowest pH in the contemporary diatom data set in the region and confidence intervals for pH predictions increase at the extremes of regressions; (2) other factors in addition to pH may be responsible for the diatom species distribution in the lake and in the entire northern Great Lakes region; (3) McNearney Lake has a well-buffered pH as a consequence of its low pH and high aluminium concentrations and is not expected to exhibit a large pH change as a result of changes in atmospheric deposition; and (4) atmospheric deposition in the region is modest and would not cause a pH shift large enough to be discernable in McNearney Lake. Elevated atmospheric deposition is indicated in recent sediments by Pb, V, and polycyclic aromatic hydrocarbon accumulation rates and to a lesser extent by those of Cu and Zn; however, these accumulation rates are substantially lower than those observed for acidified lakes in the northeastern United States. Although atmospheric loadings of materials associated with fossil fuel combustion have recently increased to McNearney Lake and apparently are continuing, the present study of the diatom subfossil record does not indicate a distinct, recent acidification (pH decrease).
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    Paleoecological investigation of recent lake acidification in the northern Great Lakes states (1990)
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    Journal of paleolimnology 4 (1990), S. 153-201 
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    ISSN: 1573-0417
    Keywords: lake acidification ; mid-western U.S.A. ; diatoms ; geochemistry ; pollen ; land use
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Paleoecological analyses of sediments from nine northern Great Lakes states (NGLS) lakes reveal small pH changes in seven of these lakes since 1860, four of these being declines. The largest diatom-inferred (DI) pH declines of 0.5 pH units were found in Brown L. and Denton L., Wisconsin. Two other lakes with suspected total alkalinity declines (based on an acidification model and on historical water chemistry, respectively), McNearney L., Michigan, and Camp 12 L., Wisconsin, have not acidified recently according to diatom-inference techniques. Many of the observed trends of increasing pH are coincident with logging; floristic composition of diatom assemblages also changed coincident with fisheries manipulations in some lakes, but these floristic trends did not affect DI pH. Sediment core profiles of Pb, S, and polycyclic aromatic hydrocarbons provide a record of atmospheric deposition of fossil fuel combustion products beginning around the turn of the century; onset is later and accumulation rates are smaller than for other northeastern study regions of the Paleoecological Investigation of Recent Lake Acidification (PIRLA) Project. The response of diatom species to lakewater pH in the NGLS region is very strong and similar to response in other regions. Overall, there is little paleoecological evidence that acidic deposition has caused significant acidification of lakes in the NGLS region.
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    Paleolimnology of three Jackman Sound Lakes, Southern Baffin Island, based on down-core diatom analyses (1990)
    Springer
    Journal of paleolimnology 4 (1990), S. 203-217 
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    ISSN: 1573-0417
    Keywords: diatoms ; Baffin Island ; North West territories ; emergence ; climatic change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Three lakes, informally named Lakes Inqua, Instaar and Mercer, from the Jackman Sound area in Southern Baffin Island were cored. The elevation of the three lakes are 36 m above high tide (aht), 10 m aht and 1 m aht. The cores from Lakes Inqua and Mercer penetrated the marine/lacustrine boundary; the core from Lake Instaar is estimated to have come within ca. 5 cm of this boundary. In addition, grab samples and water samples were retrieved from the lakes. The cores have been 14C dated (AMS). Emergence of the three lake basins from the sea occurred approximately 8650 BP (Lake Inqua), 8630 BP (Lake Instaar) and 7900 BP (Lake Mercer, averaged date). This suggests a very rapid rate (〉5 m/100 yrs) of glacio-isostatic rebound for this area. Down-core analyses of diatom assemblages indicate that the paleolimnology in the three lakes was similar. The diatom analyses suggest a change in climate between approximately 8000 and 6000 BP, which is also reflected in the marine record from the same area, and the onset of the neoglacial period around 4500 to 3800 BP. A decrease in diatom-inferred pH is evident in the lakes' development and can probably be related to the general change of the watershed vegetation with time.
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    Variability of sediment diatom assemblages in an upland, wind-stressed lake (Loch Fleet, Galloway, S.W. Scotland) (1990)
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    Journal of paleolimnology 4 (1990), S. 43-59 
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    ISSN: 1573-0417
    Keywords: diatoms ; concentrations ; accumulation rates ; variability ; acidification ; correspondence analysis ; cluster analysis ; surface sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The variability of diatom distribution in an acidified, upland wind-stressed lake (Loch Fleet, Galloway, S. W. Scotland) was assessed by analysis of 28 surface sediment samples and 11 cores. Correspondence analysis (CA) and cluster analysis were used to illustrate the variability of the surface sediment and core samples. There was reasonable uniformity of taxa in most of the surface sediment samples, although 7 samples, as indicated by both CA and cluster analyses were atypical. Most cores recorded clearly the acidification of the lake, although percentages of individual taxa varied up to 20% between cores. Two cores had old, preacidification diatom assemblages (of indeterminate age) close to the sediment surface. These old sediments were probably the source of the re-worked diatoms found in the atypical surface sediment assemblages. Diatom trends, as CA ordinations and pH profiles, were less variable than the surface sediment assemblages. It is argued that non-uniform sediment accumulation rates and diatom deposition cause variability in surface sediment diatom samples. This variability may be reduced in core profiles by homogenization during further resuspension/deposition cycles and burial. Cores, and the associated time component they offer, may be useful in assessing the variability of surface sediment assemblages.
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    A procedure for preparing large sets of diatom slides from sediment cores (1990)
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    Journal of paleolimnology 4 (1990), S. 87-90 
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    ISSN: 1573-0417
    Keywords: diatoms ; slide preparation ; light microscopy ; lake sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract A procedure is described for making diatom microscopy slides from large numbers of sediment samples, simultaneously. The method uses small sediment samples, small test tubes, small amounts of hydrogen peroxide, no decantings, no centrifuging, and it requires no washing-up of glassware. It is, therefore, fast, cheap, gentle to the diatoms and needs little fume cupboard space.
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    Baptiste Lake, Alberta — A late Holocene history of changes in a lake and its catchment in the southern Boreal forest (1990)
    Springer
    Journal of paleolimnology 4 (1990), S. 253-267 
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    ISSN: 1573-0417
    Keywords: palaeolimnolgy ; pollen ; diatoms ; pigments ; southern boreal forest ; fire ; Alberta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Palaeoenvioonmental investigations based upon sediment cores retrieved from Baptiste Lake, Alberta (longitude 114° 34′ W; latitude 54° 45′ N) show that the sedimentary record spans approximately 4600 years. The pollen record reflects the dynamic nature of the southern boreal forest. These dynamic changes are reflected in the lake record itself. Climate and vegetation do not appear to have changed significantly; however, the lake does appear to have responded to climate change, particularly during the last 1000 to 700 years when temperatures decreased to modern values. It is at this time that there is a marked change from laminated to unlaminated sediments suggesting a change from meromixis to one where complete circulation takes place. As a result monolimnetic nutrients are released into the epilimnion. Catchment perturbations have occurred with fire appearing most important. Sedimentation rates are high on average and irregular, due in part to the many inflowing streams, catchment topography and fire. Lake production has always been high. Carbonate bands occur in the core at irregular intervals and appear to originate biogenically. Peaks in the number of pyrite spherules suggest that deoxygenation of the water column occurs irregularly, and the intensity of anaerobic conditions again varies. The diatom record indicates a eutrophic lake with Stephanodiscus hantzschii the dominant species. The lake appears to have steadily become more eutrophic with time and a succession of species has occurred with Asterionella formosa being succeeded in turn by Stephanodiscus niagare, Cyclotella comta and finally, Melosira granulata. The appearance of Melosira granulata corresponds to the change from laminated to unlaminated sediments, and to then both autochthonous and allochthonous nutrient input.
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    Spatial pattern of recent sediment and diatom accumulation in a small, monomictic, eutrophic lake (1990)
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    Journal of paleolimnology 3 (1990), S. 143-160 
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    ISSN: 1573-0417
    Keywords: diatoms ; sediment accumulation pattern ; macrophytes ; relative accumulation rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Spatial variability of sediment and diatom deposition was assessed in a small monomictic, eutrophic lake in Northern Ireland (Lough Augher, Co. Tyrone) using measurements from 17 sediment cores. Loss-onignition profiles in water depths 〉6 m showed good repeatability, while littoral cores were more variable with localised profiles. Dry mass accumulation rates, derived by biostratigraphic correlation to a 210Pb dated master core, were variable and not correlated with water depth. Basin mean dry mass accumulation rate was 0.068 g cm-2 yr-1 (range 0.036–0.09) prior to 1900, and 0.19 g cm-2 yr-1 (range 0.11–0.3) after 1974. Post-1940 cumulative fluxes were estimated for dry mass (range 3.49–916 g cm-2) and diatoms (range 16.9–113.8×107 frustules cm-2). Cumulative dry mass was inversely correlated (r=−0.64) with distance from the inflow, indicating its localised influence. No variable was correlated with water depth except frustules of planktonic diatoms (r=0.66). However, high cumulative fluxes of diatoms and dry mass away from the inflow suggest that the expansion of the littoral macrophyte community may be responsible for decreased resuspension in shallow water, and together with increased sediment trapping, has enhanced sediment accumulation in shallow water over recent time periods.
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    Paleoecological investigation of recent lake acidification in the Adirondack Mountains, N.Y. (1990)
    Springer
    Journal of paleolimnology 3 (1990), S. 195-241 
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    ISSN: 1573-0417
    Keywords: acid deposition ; Adirondacks ; diatoms ; lake acidification ; paleoecology ; sediment chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Paleoecological analysis of the sediment record of 12 Adirondack lakes reveals that the 8 clearwater lakes with current pH 〈 5.5 and alkalinity 〈 10 μeq l-1 have acidified recently. The onset of this acidification occurred between 1920 and 1970. Loss of alkalinity, based on quanitative analysis of diatom assemblages, ranged from 2 to 35 μeq l-1. The acidification trends are substantiated by several lines of evidence including stratigraphies of diatom, chrysophyte, chironomid, and cladoceran remains, Ca:Ti and Mn:Ti ratios, sequentially extracted forms of Al, and historical fish data. Acidification trends appear to be continuing in some lakes, despite reductions in atmospheric sulfur loading that began in the early 1970s. The primary cause of the acidification trend is clearly increased atmospheric deposition of strong acids derived from the combustion of fossil fuels. Natural processes and watershed disturbances cannot account for the changes in water chemistry that have occurred, but they may play a role. Sediment core profiles of Pb, Cu, V, Zn, S, polycyclic aromatic hydrocarbons, magnetic particles, and coal and oil soot provide a clear record of increased atmospheric input of materials associated with the combustion of fossil fuels beginning in the late 1800s and early 1900s. The primary evidence for acidification occurs after that period, and the pattern of water chemistry response to increased acid inputs is consistent with current understanding of lake-watershed acidification processes.
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    A palaeoecological test of the land-use hypothesis for recent lake acidification in South-West Norway using hill-top lakes (1990)
    Springer
    Journal of paleolimnology 4 (1990), S. 69-85 
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    ISSN: 1573-0417
    Keywords: diatoms ; pollen ; chrysophytes ; heavy metals ; acidification ; land-use ; Norway ; pH changes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Lakes perched on hill-tops have very small catchments. Their water chemistry is largely influenced by the chemical composition of precipitation and by the underlying bedrock geology. They are ideal sites for testing the hypothesis that land-use and associated soil changes are a major cause of recent lake acidification. On this hypothesis, hill-top lakes in SW Norway are predicted not to show any recent lake acidification because, by their very nature, the chemistry of such lakes is little influenced by land-use or soil changes. Palaeolimnological analyses of diatoms and chrysophytes show that prior to ca. 1914 the two hill-top lakes investigated were naturally acid with reconstructed lake-pH values of at least 4.8–5.1. Since ca. 1914 lake pH values declined to ca. 4.5–4.7. These results contradict the land-use hypothesis. All the available palaeolimnological evidence (diatoms, chrysophytes, pollen, sediment geochemistry, carbonaceous particles) is consistent with the acid-deposition hypothesis. In the absence of any evidence to support the land-use hypothesis as a primary cause of recent lake acidification and in the light of several independent refutations, it is perhaps time to put the land-use hypothesis for recent lake acidification to rest.
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    Paleoecological investigations of recent lake acidification in northern Florida (1990)
    Springer
    Journal of paleolimnology 4 (1990), S. 103-137 
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    ISSN: 1573-0417
    Keywords: acidic deposition ; diatoms ; hydrology ; Florida ; paleoecology ; sediment chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Thirty-two northern Florida lakes were analyzed to construct a transfer function relating surface sediment diatom assemblages to lakewater pH (R 2 =0.89, s.e.=0.34). A paleoecological analysis of sediment cores from six of these lakes indicated that two have become more acidic in the last 50 years. The diatom inferred (DI) pH of L. Barco has declined between 0.56–0.82 in the 1900's and DI ANC (acid neutralizing capacity) by 28–46 μeq l-1. The DI pH of nearby L. Suggs has declined 0.91 pH units and its DI ANC by 19 μeq l-1. The timing of the inferred acidification is synchronous with known increases in emissions of sulfates and nitrates that are associated with acidic precipitation. Also, the increasing accumulation of substances related to emissions from the burning of fossil fuels (e.g., Pb, PAH) co-occurs with the lowering of DI pH in the sedimentary record. However, other processes may have accounted for or contributed to recent lake acidification. For instance, the drawdown of local water tables by human consumption may decrease the inseepage of ANC to seepage lakes. Such an effect would be synchronous with increasing depositions of sulfate. There is also clear evidence that Florida lakes are naturally acidic. Thus, paleoecological results indicate acidic deposition to be at certain contributor, but not necessarily the sole cause, of the recent further acidification of some naturally acidic Florida lakes.
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    URL: http://dx.doi.org/10.1007/BF00226320
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    Potential variation of nitrogen transformations in pinyon-juniper ecosystems resulting from burning (1990)
    Springer
    Biology and fertility of soils 10 (1990), S. 35-44 
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    ISSN: 1432-0789
    Keywords: Pinus edulis ; Juniperus osteosperma ; Carbon ; Nitrogen ; Nitrification ; Microbial N ; N immobilization ; Fire ecology ; Nitrifying bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Forest floor litter, duff, and underlying soils were assembled in laboratory microcosms representing pinyon, juniper, and interspace field conditions. Burning removed more than 95% of both N and C from the litter, with losses from the duff dependent on soil moisture conditions. No significant changes in total N or C were noted in the soil. Immediate increases were observed in soil NH inf4 sup+ , decreasing with depth and related to soil heating. The greatest increases were noted in both the pinyon and juniper soils that were dry at the time of the burn, with interspace soils exhibiting the least changes. Soil NH inf4 sup+ closely approximated the controls on day 90 after the burns in all treatments. Ninety days after the burn microbial biomass N was highest in the controls, followed by the wet and then the dry-burned soils, in both the pinyon and juniper microcosms. This was inversely related to the levels of accumulated NO inf3 sup- . Nitrifying bacteria populations were indirectly correlated to soil temperatures during the burn. Population levels 90 days after the burn showed increases in both the wet- and the dry-burn treatments, with those in the pinyon treatments exceeding those found in the nitial controls of pinyon soils.
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    Can acidification associated with nitrification increase available soil phosphate or reduce the rate of phosphate fixation? (1990)
    Springer
    Biology and fertility of soils 10 (1990), S. 145-151 
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    ISSN: 1432-0789
    Keywords: Nitrification ; Soil acidification ; Carbonate dissolution ; Available P ; Phosphate precipitation ; Intensive agriculture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary It is often proposed that soil acidification by microorganisms dissolves unavailable soil phosphates, especially crystalline Ca phosphates. Unavailable phosphates, it is suggested, could thus become available to crops. Microorganisms that oxidize one ammonium ion to one nitrate ion excrete two protons into the soil solution. In the present study, this universal biological process of soil acidification was used to measure, in neutral and calcareous soils, the effect of acidification on available soil phosphate and on the rate of phosphate fixation when water-soluble phosphate fertilizers are added to soils. During nitrification the Ca2+ and Mg2+ ion concentrations in soil solutions increase but the phosphate ion concentration remains constant. The excreted protons preferentially dissolve soil Ca and Mg carbonates. Soil Ca phosphates are not dissolved; they remain unavailable. When P fertilizers were applied, the rate of fixation of phosphate ions was not slowed down by acidification associated with nitrification. This biological acidification may have a long term effect, over many years, on the slow accumulation of available phosphate in soils under native grasslands, but it cannot have a significant effect on the availability of soil P under intensive agricultural practices.
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    URL: http://dx.doi.org/10.1007/BF00336251
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    Influence of pH on the release of NO and N2O from fertilized and unfertilized soil (1990)
    Springer
    Biology and fertility of soils 10 (1990), S. 139-144 
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    ISSN: 1432-0789
    Keywords: Denitrification ; Nitrification ; Chemodenitrification ; Ammonium ; Nitrite ; Nitrate ; Nitric oxide ; Nitrous oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary NO and N2O release rates were measured in an acidic forest soil (pH 4.0) and a slightly alkaline agricultural soil (pH 7.8) after the pH was adjusted to values ranging from pH 4.0 to 7.8. The total release of NO and N2O during 20 h of incubation was determined together with the net changes in the concentrations of NH 4 + , NO 2 − and NO 3 − in the soil. The release of NO and N2O increased after fertilization with NH 4 + and/or NO 3 − ; it strongly decreased with increasing pH in the acidic forest soil; and it increased when the pH of the alkaline agricultural soil was decreased to pH 6.5. However, there was no simple correlation between NO and N2O release or between these compounds and activities such as the NO 2 − accumulation, NO 3 − reduction, or NH 4 + oxidation. We suggest that soil pH exerts complex controls, e.g., on microbial populations or enzyme activities involved in nitrification and denitrification.
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    Fixation of dissolved silicate and sedimentation of biogenic silicate in the lower river Rhine during diatom blooms (1990)
    Springer
    Biogeochemistry 9 (1990), S. 175-185 
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    ISSN: 1573-515X
    Keywords: Silicate ; river Rhine ; diatoms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Concentrations of dissolved silicate and particulate biogenic silicate were measured in three branches of the lower river Rhine in The Netherlands in order to analyse the role of this element in the eutrophication of the river basin. Particulate silicate followed the seasonal development of the phytoplankton, which was dominated by diatoms. The concentration of dissolved silicate fell during blooms (〈 0.1 mg.l−1 ), but the amounts of biogenic silicate measured (∼ 1 mg.l−1) were insufficient to explain the seasonal decrease in the dissolved fraction; this indicates retention of silicate upstream. Some particulate biogenic silicate in river water settled in man-made sedimentation areas in the Rhine delta. The observations suggest that changes in silicate fixation in the Rhine may have contributed to the incidence of non-diatom phytoplankton blooms in receiving waters.
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    URL: http://dx.doi.org/10.1007/BF00692170
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    Detection of nitrification in a stagnohumic-gley soil (1989)
    Springer
    Biology and fertility of soils 8 (1989), S. 335-338 
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    ISSN: 1432-0789
    Keywords: Autotrophy ; Lime ; Lolium perenne ; Nitrate reductase ; Nitrification ; Stagnohumic gley
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Three different nitrification assays (short-term nitrifier activity, assimilatory nitrate reductase activity of Lolium perenne, and nitrate accumulation in the absence of plants) were performed either on soil from a naturally acidic stagnohumic-gley or on leaves from L. perenne grown in this soil. Before the investigation the soil was limed and fertilised in a manner consistent with established agricultural pasture improvement strategies. Short-term nitrifier activity was only detected in soils above pH 5.6. However, nitrate reductase activity and nitrate accumulation both showed a near linear increase between soil pH 3.8 and 6.8. These findings are attributed to the nature of the assays, each of which considers a different component of the soil nitrifier population.
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    Abiotic factors regulating nitrification in a Swedish arable soil (1989)
    Springer
    Biology and fertility of soils 8 (1989), S. 247-254 
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    ISSN: 1432-0789
    Keywords: Nitrification ; Abiotic factors ; Ammonium concentration ; Vmax of nitrification ; Michaelis-Menten constant for ammonium oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of temperature, water potential and ammonium concentrations were studied in field and laboratory experiments on arable soil. The two field experiments used different sampling intervals, one at daily (short-term) and the other at monthly (long-term) intervals. In the short-term field experiment, the numbers and activities of nitrifiers were assessed before and after natural rain or irrigation. The nitrifiers were apparently outcompeted by heterotrophs during the first days after wetting the soil. Potential nitrification was affected only slightly by changes in water potential, whereas the numbers of ammonium and nitrite oxidizers appeared more sensitive to these changes. The numbers of ammonium and nitrite oxidizers correlated strongly during the daily samplings. The potential nitrite-oxidation rates correlated with water potentials whereas the potential ammonium oxidation rates did not. Extractable ammonium decreased in proportion to increasing nitrate concentrations in both the rain-fed and the irrigated plots. In the long-term field experiments, the numbers of ammonium oxidizers correlated with water potentials but not with in situ temperature or with ammonium concentrations. The potential ammonium-oxidation rates correlated with water potentials and with ammonium-oxidizer numbers. The potential nitrite-oxidation rates correlated strongly with the potential ammonium-oxidation rates. The field experiments implied that nitrite oxidizers obtained substrate from ammonium oxidizers but also from nitrate reduction. In laboratory experiments nitrate accumulated at a Q 10 of about 2 and the V max for nitrification was observed at a water potential of −0.11 MPa (65% of water-holding capacity). The K m for ammonium oxidation at pH 8.2 was 1.72 mg l−1 soil water.
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    Long-term effects of different inorganic pollutants on nitrogen transformations in a sandy cambisol (1989)
    Springer
    Biology and fertility of soils 7 (1989), S. 254-258 
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    ISSN: 1432-0789
    Keywords: N-mineralisation ; Nitrification ; Arginine ammonification ; Inorganic pollutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Long-term effects of 12 inorganic pollutants on N transformations were studied in a sandy cambisol. As, Be, Br, Cd, Cr, F, Pb, Hg, Se, Sn, and V were added to the soil as inorganic salts in 1975 and 1976. Soil samples were taken in 1984 to determine total N mineralisation and nitrification. All pollutants except Se and Sn inhibited N mineralisation. The most toxic elements under investigation were Be and Hg. Nitrification was reduced to a lower degree than total N mineralisation. As, Be, Cd, Cr, F, Pb, Se, and Sn failed to inhibit this process at all. It is assumed that nitrifying bacteria became adapted to these pollutants in the course of time. The arginine-ammonification method was less sensitive in detecting the effects of pollutants on N transformation than the N mineralisation test.
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    Inhibition of nitrification in soil by heterocyclic nitrogen compounds (1989)
    Springer
    Biology and fertility of soils 8 (1989), S. 204-211 
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    ISSN: 1432-0789
    Keywords: Nitrification ; Heterocyclic N compounds ; Pyrazoles ; Triazoles ; Pyridines ; Thiadiazoles ; 2-Ethynylpyridine ; Nitrapyrin ; Etridiazole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The relationship between the structures of diverse heterocyclic nitrogen (N) compounds and the effectiveness of these compounds for the inhibition of nitrification in soil was studied by determining the effects of different amounts of 12 unsubstituted and 33 substituted heterocyclic N compounds on the production of (NO 2 − +NO 3 − )-N in soils incubated at 25 °C for 21 days after treatment with ammonium sulfate. The results showed that unsubstituted heterocyclic N compounds containing two adjacent ring N atoms inhibit nitrification in soil and that two of these compounds, pyrazole and 1,2,4-triazole, are potent inhibitors. They also showed that several substituted pyrazoles and thiadiazoles are good inhibitors of nitrification in soil (e.g., 3-methylpyrazole and 3,4-dichloro-1,2,5-thiadiazole).
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    Paleolimnological evidence for the recent acidification of Llyn Hir, Dyfed, Wales (1989)
    Springer
    Journal of paleolimnology 2 (1989), S. 245-262 
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    ISSN: 1573-0417
    Keywords: acidification ; diatoms ; sediment chemistry ; magnetic stratigraphy ; soot ; paleolimnology ; Wales
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract A variety of paleolimnological techniques, coupled with historical data on land-use and fisheries, are used to evaluate the magnitude, timing, and causes of acidification of Llyn Hir, a moorland lake in central Wales. pH reconstruction based on diatom analysis suggests a gradual decline in lakewater pH beginning ca. 1870 and intensifying in the mid-1930's, with a total decline of 1.1 pH units between 1870 and 1984. This pH decline correlates with increased sedimentary concentrations of carbonaceous particles, trace metals, and magnetic minerals, which indicate the local deposition of atmospherically transported products of fossil-fuel combustion. Pollen data and the historical record show no significant alterations in land-use or catchment vegetation, indicating that acidification of Llyn Hir is a result of the increased deposition of atmospheric pollutants, not of land-use and vegetation change.
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    Late Quaternary Palaeoenvironment of Spring Lake, Alberta, Canada (1989)
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    Journal of paleolimnology 2 (1989), S. 305-317 
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    ISSN: 1573-0417
    Keywords: Late Quaternary ; pollen ; diatoms ; pigments ; climatic change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Palaeoenvironmental investigations based upon sediment cores taken from Spring Lake in the Peace River District of Alberta, Canada (latitude 55° 31′ N; longitude 119° 35′ W) show that the sedimentary record spans the Holocene period. Chemical and diatom changes coincide with regional climatic change since deglaciation (about 11 000 yr. B.P.). Calcite laminations in the basal 3 metres of the cores are evident, and were probably formed through elevated water temperature although photosynthetic removal of CO2 undoubtedly contributed. The disappearance of the laminations, and concurrent decrease in calcite X-ray diffraction peaks ca. 5000 yr. B.P. may have been caused by a change from a partially meromictic to a dimictic lake as the climate changed. Benthic and alkaline diatoms dominate before 5000 yr. B.P., while the planktonic Stephanodiscus hantzschii dominated between 5100 and 4200 yr. B.P. probably owing to increased nutrient levels. From ca. 4200 yr. B.P. until the present, benthic Fragilaria spp. and more circumneutral diatoms were dominant. Palaeoproduction, as measured by chlorophyll derivates, was highest in the early developmental stages of the lake, decreased coinciding with a major disturbance of the sediments and lowered water levels, and then gradually increased again until present. Only during the earlier period of peak production does biogenic calcite formation appear more important than calcite deposition caused by high water temperatures.
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    Sediment chemistry and diatom stratigraphy of two high arctic isolation lakes, Truelove Lowland, Devon Island, N.W.T., Canada (1989)
    Springer
    Journal of paleolimnology 2 (1989), S. 207-225 
    Details
    ISSN: 1573-0417
    Keywords: diatoms ; trace elements ; rare earths ; isostasy ; environmental change ; multivariate analysis ; arctic lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Three sediment cores from two lakes, Fish Lake and Phalarope Lake, in Truelove Lowland, Devon Island, N.W.T. were analyzed for diatoms and chemical composition. Multivariate statistical techniques using a range of chemical variables successfully isolated three sediment groupings in the cores. Allochthonous and autochthonous chemical components in the sediments have been used to reconstruct paleoenvironmental conditions. The two lakes began approximately 10600 years ago as shallow marine lagoons that were isolated from the sea as a result of glacio-isostatic rebound. Based on the presence of distinctive diatom assemblages, the three stratigraphic zones are identified as a basal marine zone, an intermediate and transitional brackish/marine zone and an upper freshwater zone. Following isolation from the sea, the lakes were flushed with freshwater produced by snow and ice melt. In Fish Lake, the period of transition from marine to freshwater, which began approximately 7000 years ago, lasted approximately 800 years. In Phalarope Lake, which was isolated from the sea approximately 5000 years ago, flushing by fresh water was completed only within the last 300 years. Fe, Cr, and Mo in the sediments are associated with the isolation phase when lake sedimentation is sensitive to the presence of brackish water and erosion within the lake catchments. In particular, the precipitation of Mo as MoS2 reflects the presence of hypolimnetic anoxia associated with lake isolation. During the early post-isolation phase the response of lake biota to an influx of nutrients is reflected in an increase in biological silica and organic carbon in the lake sediments. On the other hand, the generally low organic content of the sediments indicates that sedimentation in these lakes has been largely determined by variations in non-biogenic factors through time. During the mid Holocene the progressive stabilization of surface materials within the lake catchments is marked by decreasing Cr, As and Na in the sediments. At the same time, an increase in allochthonous Mn and Fe is attributed to progressive soil development. During the last 2500 years the catchments have experienced decreased erosion resulting in a decrease in both allochthonous clastic input and lake productivity.
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    Paleolimnological reconstruction of recent acidity changes in four Sierra Nevada lakes (1989)
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    Journal of paleolimnology 2 (1989), S. 285-304 
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    ISSN: 1573-0417
    Keywords: acid rain ; biostratigraphy ; diatoms ; paleolimnology ; lake acidification ; Sierra Nevada
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We have completed a paleolimnological analysis of sediment cores from four lakes in the Sierra Nevada Range of California (USA). The diatom-inferred pH profile from Harriet Lake in Yosemite National Park (present pH=6.52) indicates no significant trends over the last 250 years. Inferred pH from Emerald Lake in Sequoia National Park (present pH=6.10) indicates a very small increase (〈0.1 pH unit) over the past 60 years and perhaps another small increase (ca. 0.15 pH unit) since 1976. Eastern Brook Lake in Inyo National Forest (present pH=7.06) shows evidence of both long-term alkalinification (ca. 0.3 pH unit over the last 200 years) and pH fluctuations since 1970. Lake 45 in King's Canyon National Park (present pH=5.16) appears to have acidified slightly (ca. 0.2 pH unit) over the last 60 years. Factors causing the observed trends are uncertain, but a role for acidic deposition cannot be ruled out.
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    Diatom, pollen, and geochemical evidence for the palaeosalinity of Medicine Lake, S. Dakota, during the late-Wisconsin and early Holocene (1989)
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    Journal of paleolimnology 2 (1989), S. 159-172 
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    ISSN: 1573-0417
    Keywords: diatoms ; pollen ; geochemistry ; salinity ; paleoclimate ; South Dakota
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Medicine Lake is a highly saline meromictic lake in eastern South Dakota. A lithostratigraphic and biostratigraphic study of the late-glacial and early post-glacial sediments shows that it was a relatively deep dilute freshwater lake during the period of the Picea pollen zone. When spruce forest changed to a Betula and then to a Quercus/Ulmus woodland in the early post-glacial period, the lake water became more concentrated but remained fresh. However, during the subsequent rapid transition to prairie in the early Holocene, when Gramineae, Ambrosia, and Artemisia dominated dry-land vegetation, the freshwater diatom flora was progressively replaced by a saline assemblage characterized by Cyclotella quillensis, Chaetoceros, and eventually Cyclotella caspia. The lake became permanently saline at about 9000 yr BP. A comparison of the fossil diatom assemblages with surface-sediment samples from a range of lakes in the Dakotas indicates that the change involved an increase in conductivity from about 500 μS cm−1 in the late-glacial period to 〉 10 000 μS cm−1 in the early Holocene. This rapid change is also marked by an abrupt increase in sulphate concentration in the sediment, the first appearance of bands of gypsum crystals, and the beginning of a well-laminated core sequence that continues through the remaining sediment record. Conditions of high salinity have prevailed to the present day.
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    Carbon and nitrogen mineralization in subarctic agricultural and forest soils (1988)
    Springer
    Biology and fertility of soils 6 (1988), S. 33-38 
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    ISSN: 1432-0789
    Keywords: Microbial activity ; Nitrification ; Taiga ; Tillage system ; Crop residue management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary C and N mineralization potentials were determined, in a 12-week laboratory incubation study, on soil samples obtained from recently cleared land which had been cropped to barley for 4 years (field soils) and from nearby undisturbed taiga (forest soils). Treatments for the cropped soils were conventional and no-tillage with and without crop residues removed. An average of about 3% of the total C was evolved as CO2 from the field soils compared with 〉 10% and 4% for the upper (Oie) and lower (Oa) forest-floor horizons, respectively. Significantly more C was mineralized from the Ap of the no-till treatment with residue left on the surface than from the other field Ap horizons. Both forest-floor horizons showed rather long lag periods for net mineralization compared with the field soils, but at the end of the incubation, more mineral N was recovered from the forest Oie despite a rather wide C:N ratio, than from the field soils. After 12 weeks about 115, 200 and 20 μg mineral N/g soil were recovered from the field Ap, the forest Oie and the forest Oa horizons, respectively. Very little C or N was mineralized from the B horizon of the forest or the field soils. Nitrification was rapid and virtually complete for the field soils but was negligible for both forest-floor O horizons.
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    The effect of fertilisation on soil nitrifier activity in experimental grassland plots (1988)
    Springer
    Biology and fertility of soils 5 (1988), S. 344-349 
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    ISSN: 1432-0789
    Keywords: Nitrification ; Deamination ; Grassland ; N fertilisers ; pH ; Denitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Soil nitrification was compared in soils from 89-year-old grassland experimental plots with diverse chemical characteristics. Measurements of NaClO3-inhibited short-term nitrifier activity (SNA) and deamination of 1,2-diamino-4-nitrobenzene were used to study nitrification and deamination activities, respectively, in soil from each of 12 plots. Using multiple regression analysis, an expression for the relationship between SNA, soil pH and fertiliser N additions was derived which indicated that both the frequency and the quantity of farmyard manure additions were important in determining the rate of nitrification. SNA was greatest where there were large and frequent additions of farmyard manure. In soil with pH below 5.2 SNA was very low or insignificant. The effect of (NH4)2SO4 additions could not be assessed because they acidified the soil. We suggest that additions of farmyard manure increase the potential for NO3 − leaching or for denitrification. Deaminase assays indicated that soils with a higher pH showed greater N mineralisation than soils with a lower pH, except at the low extreme. There was no obvious relationship between SNA and deaminase activity at higher levels of pH.
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    Seasonal, annual, and treatment-induced variation in available nitrogen pools and nitrogen-cycling processes in soils of two Douglas-fir stands (1988)
    Springer
    Biology and fertility of soils 6 (1988), S. 93-99 
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    ISSN: 1432-0789
    Keywords: Ammonium ; Nitrate ; N-mineralization ; Nitrification ; Fertilization ; Irrigation ; Forest ecosystems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Forest-floor and 0–10 cm depth mineral soil horizons in two stands of Douglas fir were sampled for available NH4 +-N and NO3 −-N, N-mineralization potentials, and nitrification potentials for 2 years. The plots in each stand were sampled for 1 year, treated with either ammonium sulfate, carbohydrate (sawdust-sucrose), irrigation, carbohydrate plus irrigation, or no treatment (control), and then sampled for 1 year following treatment. In general, the direction of change following the treatments was the same for both the forest-floor and the mineral soils. Fertilization increased the NH4 +-N and NO3 −-N pools, nitrification potential, and N-mineralization potential, while treatment with carbohydrate decreased all of these characteristics. Irrigation generally increased NH4 +-N pools, nitrification potential, and N-mineralization potential, but decreased these characteristics in the soil at one site. Irrigation plus carbohydrate gave similar results to those of carbohydrate alone. Treatments altered pool sizes and/or potentials, but did not reduce within-year variance in any of these characteristics. Distinct seasonal patterns occurred in all measurements, suggesting that control of short-term variation in N-transformation processes is by factors which are dynamic in nature.
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    URL: http://dx.doi.org/10.1007/BF00257656
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    Relationships between soil moisture content and nitrous oxide production during nitrification and denitrification (1988)
    Springer
    Biology and fertility of soils 6 (1988), S. 106-111 
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    ISSN: 1432-0789
    Keywords: Nitrification ; Denitrification ; Soil water content ; N2O production ; Acetylene ; Ammonium fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of soil water content [60%–100% water-holding capacity (WHC)] on N2O production during autotrophic nitrification and denitrification in a loam soil was studied in a laboratory experiment by selectively inhibiting nitrification with a low C2H2 concentration (2.1 Pa). Nitrifiers usually produced more N2O than denitrifiers. During an initial experimental period of 0–6 days the nitrifiers produced more N2O than the denitrifiers by a factor ranging from 1.4 to 16.5, depending on the water content and length of incubation. The highest N2O production rate by nitrifiers was observed at 90% WHC, when the soil had become partly anaerobic, as indicated by the high denitrification rate. At 100% WHC there were large gaseous losses from denitrification, while nitrification losses were smaller except for the first period of measurement, when there was still some O2 remaining in the soil. The use of 10 kPa C2H2 to inhibit reduction of N2O to N2 stimulated the denitrification process during prolonged incubation over several days; thus the method is unsuitable for long-term studies.
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    URL: http://dx.doi.org/10.1007/BF00257658
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    A method of selective inhibition to distinguish between nitrification and denitrification as sources of nitrous oxide in soil (1988)
    Springer
    Biology and fertility of soils 6 (1988), S. 112-119 
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    ISSN: 1432-0789
    Keywords: Denitrification ; Nitrification ; Selective inhibitors ; Nitrapyrin ; Acetylene ; Nitrous oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrapyrin and C2H2 were evaluated as nitrification inhibitors in soil to determine the relative contributions of denitrification and nitrification to total N2O production. In laboratory experiments nitrapyrin, or its solvent xylene, stimulated denitrification directly or indirectly and was therefore considered unsuitable. Low partial pressures of C2H2 (2.5–5.0 Pa) inhibited nitrification and had only a small effect on denitrification, which made it possible to estimate the contribution of denitrification. The contribution of nitrification was estimated by subtracting the denitrification value from total N2O production (samples without C2H2). The critical C2H2 concentrations needed to achieve inhibition of nitrification, without affecting the N2O reductase in denitrifiers, must be individually determined for each set of experimental conditions.
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    URL: http://dx.doi.org/10.1007/BF00257659
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    Carbon and nitrogen accretion and dynamics in volcanic ash deposits from different subarctic habitats (1988)
    Springer
    Biology and fertility of soils 7 (1988), S. 79-87 
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    ISSN: 1432-0789
    Keywords: Microbial biomass ; Mineralization ; Nitrification ; Subarctic ; Volcanic ash
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary C and N pool sizes and rates of mineralization were studied in volcanic-ash deposits found in different subarctic habitats in southwestern Alaska. Surface ash samples were taken from white-spruce, alder, and moist- and dry-tundra habitats and were analysed for total and microbial C and N. C and N dynamics were studied using a 28-day aerobic laboratory incubation, with weekly measurement of evolved CO2 and determination of inorganic-N pools initially and after 10 and 28 days. Total and microbial C and N and cumulative respired CO2 all followed a similar pattern among the different habitats, with the moist-tundra habitat having the highest values and the spruce site the lowest. The size of the microbial biomass C and N pool in the spruce habitat was among the lowest reported for any ecosystem. Little net N mineralization occurred in the spruce-forest and dry-tundra ash over 28 days. Ash from the moist-tundra habitat immobilized a significant amount of N during the first 10 days of incubation, yet showed a large net release of N after 28 days. In contrast, the ash from the alder site exhibited net mineralization after both periods, with N production after 28 days being about 3.5 times that after 10 days. In addition, the alder-habitat ash was the only soil that showed net nitrification. Rates of total C and N accretion in the tundra and alder habitats were rapid relative to rates found for primary successions. The results of this study show that habitat has a profound effect on C and N cycling in subarctic environments.
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    URL: http://dx.doi.org/10.1007/BF00260737
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    Influence of smoke exposure on soil enzyme activities and nitrification (1988)
    Springer
    Biology and fertility of soils 6 (1988), S. 341-346 
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    ISSN: 1432-0789
    Keywords: Nitrification ; Phosphatase ; Dehydrogenase ; Aerosol ; Soil thickness ; Soil enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Soil was exposed to red phosphorous/butyl rubber (RP/BR) aerosols at various relative humidities in a recirculating environmental wind tunnel. Soil microbial and enzymatic activities were measured immediately after exposure and periodically thereafter for 56 days. The nitrification potential was significantly reduced in soil amended with ammonium sulfate and exposed to RP/BR smoke, and could be related to a decline in soil pH. The rate of nitrate formation in unamended soil with time was also reduced, but by 57 days postexposure, concentrations were similat to those of unexposed controls in all but the thinnest soil lense. Soil dehydrogenase and phosphatase enzyme activities were sensitive to RP/BR smoke and in some treatments no activity was detected. The measured activities did not recover within the 56-day postexposure period and in some cases declined. Soil lense thickness was the greatest factor controlling the degree of RP/BR effects, indicating that injury to soil microbial and enzymatic activities may be surficial. Deposition of smoke particles increased with increasing relative humidity, which had a significant impact on the activities measured.
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    URL: http://dx.doi.org/10.1007/BF00261024
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    Paleoindication of acidification in Kleiner Arbersee (Federal Republic of Germany, Bavarian Forest) by chydorids, chrysophytes, and diatoms (1988)
    Springer
    Journal of paleolimnology 1 (1988), S. 149-157 
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    ISSN: 1573-0417
    Keywords: paleolimnology ; acidification ; diatoms ; chydorids ; scaled chrysophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract In a sediment core of Lake Kleiner Arbersee, located in the Bavarian Forest on gneiss bedrock and with spodosolic soils in the catchment, acidification was reconstructed using assemblages of chydorids, scaled chrysophytes, and diatoms as paleoindicators. All paleoindicators demonstrated acidification of Kleiner Arbersee. There were marked differences, however, in the extent of the indicated acidification: In lower layers, where scaled chrysophytes and chydorids clearly indicate beginning acidification, pH-decline inferred by diatoms lies within the standard deviation, and is statistically not significant until the 7 cm layer. We conclude that mallomonadaceans reflect the acidification of the water body and strongly respond to the lowest seasonal pH, as their indicated rate of acidification is higher than that of diatoms, which appear to more closely indicate the pH of the sediment/water interface, especially when the pH of the water column has dropped below ca. 5.5. Chydorids may additionally be influenced by proton release of dense Sphagnum-stands, which cover the littoral of Kleiner Arbersee completely.
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    URL: http://dx.doi.org/10.1007/BF00196071
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    A late-Glacial diatom and pigment history of Little Lake, New Brunswick with particular reference to the younger Dryas climatic oscillation (1988)
    Springer
    Journal of paleolimnology 1 (1988), S. 163-177 
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    ISSN: 1573-0417
    Keywords: palaeolimnology ; diatoms ; pigments ; climatic change New Brunswick ; younger Dryas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Diatom and pigment data are presented from a 6.39 m core from Little Lake, New Brunswick. From its inception to ca. 11.5k y.B.P., the lake was dominated by benthic alkaliphilic diatoms, predominantly Fragilaria spp, which are believed to have grown in the moat of a lake with extended periods of ice cover. Ice free summers apparently prevailed for up to 500 years (ca. 11.5–11k y.B.P.), during which time planktonic species — Cyclotella bodanica Eulenst. and C. stelligera Cl. & Grun. appeared for the first time. From ca. 11.–10k y.B.P. the lake was dominated by Fragilaria pinnata Ehr.v. pinnata, F. construens v. venter (Ehr.) Grun. and F. construens (Ehr.) Grun. The reappearance of these species, coincident with distinct changes in sediments, organic matter, pollen types and influx rates, is believed to represent the influence of the younger Dryas climatic cooling. Little Lake appears to have reverted to a period of only partial summer melting. The ca. 10k y.B.P. warming is marked by a Navicula/Cymbella/Cyclotella community, representing growth of both littoral and planktonic communities. Navicula was subsequently replaced by Eunotia and Tabellaria, and finally by a Pinnularia/Stauroneis/Eunotia community, in which Fragilaria pinnata v. pinnata and F. construens v. venter increase again. These two recent phases represent increasing growth of a littoral community, and some increase in littoral alkaliphilous elements. Trends in organic matter and pigment values are consistent with a gradual increase in biomass, particularly from ca. 10k y.B.P. Diatom growth is indicative of increasing littoral and benthic growth with time, but there is no indication that Little Lake was ever eutrophic.
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    Late Quaternary paleolimnology of Walker Lake, Nevada (1988)
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    Journal of paleolimnology 1 (1988), S. 249-267 
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    ISSN: 1573-0417
    Keywords: paleolimnology ; river diversion ; climate change ; pollen ; diatoms ; ostracodes ; brine shrimp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Diatoms, crustaceans, and pollen from sediment cores, in conjunction with dated shoreline tufas provide evidence for lake level and environmental fluctuations of Walker Lake in the late Quaternary. Large and rapid changes of lake chemistry and level apparently resulted from variations in the course and discharge of the Walker River. Paleolimnological evidence suggests that the basin contained a relatively deep and slightly saline to freshwater lake before ca. 30 000 years B.P. During the subsequent drawdown, the Walker River apparently shifted its course and flowed northward into the Carson Sink. As a result, Walker Lake shallowed and became saline. During the full glacial, cooler climates with more effective moisture supported a shallow brine lake in the basin even without the Walker River. As glacial climates waned after 15 000 years ago, Walker Lake became a playa. The Walker River returned to its basin 4700 years ago, filling it with fresh water in a few decades. Thereafter, salinity and depth increased as evaporation concentrated inflowing water, until by 3000 years ago Walker Lake was nearly 90 m deep, according to dated shoreline tufas. Lake levels fluctuated throughout this interval in response to variations in Sierra Nevada precipitation and local evaporation. A drought in the Sierras between 2400 and 2000 years ago reduced Walker Lake to a shallow, brine lake. Climate-controlled refilling of the lake beginning 2000 years ago required about one millennium to bring Walker lake near its historic level. Through time, lake basins in the complex Lake Lahontan system, fill and desiccate in response to climatic, tectonic and geomorphic events. Detailed, multidisciplinary paleolimnologic records from related subbasins are required to separate these processes before lake level history can be reliably used to interpret paleoclimatology.
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    The detection of Rhizosolenia (Bacillariophyceae) in sediment of Ontario lakes and implications for paleoecology (1988)
    Springer
    Journal of paleolimnology 1 (1988), S. 61-69 
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    ISSN: 1573-0417
    Keywords: Rhizosolenia ; paleoecology ; diatoms ; acidification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The detection of the freshwater genus Rhizosolenia (Bacillariophyceae) remains in sediments is affected by the oxidants used in the digestion procedures. The Rhizosolenia counts decrease from 30% H2O2〉50% HNO3〉50% chromic acid〉100% HNO3〉100% H2SO4. Rhizosolenia is mostly found in Ontario lakes with summer average pH ranging from 5.6 to 8.3, Gran alkalinity from 0.2 to 120 mg L−1 as CaCO3 and water colour from 4 to 105 Hazen units. Large Rhizosolenia populations are generally found in clear lakes, neutral pH and low alkalinity.
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    Diatoms from the Shelton Mastodon Site (1988)
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    Journal of paleolimnology 1 (1988), S. 193-199 
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    ISSN: 1573-0417
    Keywords: diatoms ; Mammut ; Michigan ; late Glacial
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract A fairly diverse and abundant diatom flora is associated with remains of Mammut americanum at the Shelton Mastodon Site in northern Oakland County, Michigan. The most abundant elements of this flora are species commonly recorded from late-glacial deposits in North America and Europe. The nearest modern analogues of this flora are assemblages deposited in small lakes in the high arctic and present day periglacial environments. Based on the diatoms present, the most probable depositional habitat was the margin of a moderately alkaline (pH〉7.0) and moderately productive pond which existed under arctic conditions.
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    Catchment disturbance inferred from paleolimnological studies of three contrasted sub-humid environments in Morocco (1988)
    Springer
    Journal of paleolimnology 1 (1988), S. 293-322 
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    ISSN: 1573-0417
    Keywords: catchment disturbance ; sediment cores ; magnetic minerals ; geochemistry ; pollen ; diatoms ; Morocco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Paleolimnological techniques for assessing recent drainage basin disturbance are evaluated in three Moroccan lakes with catchments contrasted in terms of land-use and vegetation. Rates of sediment accumulation in the two lakes with agricultural catchments were relatively high (〉1.6 cm yr-1) in the most recent past. Dilution effects prevented core dating by the 210Pb method alone and post-1953 chronologies were constructed by combining 210Pb and 137Cs data. The recent sediment accumulation rate at the currently least disturbed site, where natural Cedrus forest is still abundant, was relatively low (〈0.4 cm yr-1) but has increased since the mid-19th century. Magnetic, geochemical, pollen, and diatom studies of all three lake sediment cores linked with modern field survey data show that soil erosion in the most vegetationally disturbed catchment (Dayat-er-Roumi) has been high throughout the recent past and that intensity peaks are probably associated with wetland drainage operations beginning in the 1940's. At the partially forested site (Dayat Affougah), pre-1950's woodland clearance and other land-use changes are the likely cause of past major soil erosion episodes. The site currently dominated by natural Cedrus forest (Lac Azigza) shows only minor disturbance during the past c. 150 years although a major soil erosion episode occrred in the 17th century. Paleolimnological analysis has clearly demonstrated that major landscape change has occurred at all three sites. However, only at the two sites with catchment cultivation do previously accelerated soil erosion and lake sediment accumulation rates persist to the present. Information essential for formulation of appropriate management plans is presented and the importance of paleolimnology in assessing man-induced lake-catchment disturbance is stressed.
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    URL: http://dx.doi.org/10.1007/BF00184003
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    Estimation of pH optima and tolerances of diatoms in lake sediments by the methods of weighted averaging, least squares and maximum likelihood, and their use for the prediction of lake acidity (1988)
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    Journal of paleolimnology 1 (1988), S. 39-49 
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    ISSN: 1573-0417
    Keywords: weighted averaging ; least squares ; maximum likelihood ; diatoms ; acidification ; Finland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Ecological optima and tolerances with respect to autumn pH were estimated for 63 diatom taxa in 47 Finnish lakes. The methods used were weighted averaging (WA), least squares (LS) and maximum likelihood (ML), the two latter methods assuming the Gaussian response model. WA produces optimum estimates which are necessarily within the observed lake pH range, whereas there is no such restriction in ML and LS. When the most extreme estimates of ML and LS were excluded, a reasonably close agreement among the results of different estimation methods was observed. When the species with unrealistic optima were excluded, the tolerance estimates were also rather similar, although the ML estimates were systematically greater. The parameter estimates were used to predict the autumn pH of 34 other lakes by weighted averaging. The ML and LS estimates including the extreme optima produced inferior predictions. A good prediction was obtained, however, when prediction with these estimates was additionally scaled with inverse squared tolerances, or when the extreme values were removed (censored). Tolerance downweighting was perhaps more efficient, and when it was used, no additional improvement was gained by censoring. The WA estimates produced good predictions without any manipulations, but these predictions tended to be biased towards the centroid of the observed range of pH values. At best, the average bias in prediction, as measured by mean difference between predicted and observed pH, was 0.082 pH units and the standard deviation of the differences, measuring the average random prediction error, was 0.256 pH units.
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    URL: http://dx.doi.org/10.1007/BF00202192
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    The relationship between sedimentary diatom assemblages and lakewater pH in 35 Quebec lakes, Canada (1988)
    Springer
    Journal of paleolimnology 1 (1988), S. 23-38 
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    ISSN: 1573-0417
    Keywords: diatoms ; paleolimnology ; diatom-inferred pH ; acidification ; Quebec
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Surface sediment diatoms from 35 soft-water lakes in southern Quebec were studied to examine the relationship with lakewater pH. The lakes ranged in pH from 5.25 to 7.66. The species composition and the relative abundance of diatoms in the study lakes was found to be closely related to pH and/or factors closely associated with pH. Predictive models were developed to infer lakewater pH using simple linear regression equations of index alpha, index B, and multiple regressions using pH preference categories. Among the predictive models examined here, the multiple regression technique provided the highest correlation coefficient (r2=0.88) and the lowest standard error (±0.26 of a pH unit) in computing diatom-inferred pH. This model appears to be the most appropriate to reconstruct lake pH histories in Quebec region.
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    The post-glacial diatom history of Splan Lake, New Brunswick (1988)
    Springer
    Journal of paleolimnology 1 (1988), S. 51-60 
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    ISSN: 1573-0417
    Keywords: Palaeolimnology ; diatoms ; post-glacial climate ; younger Dryas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The first account is given of the postglacial history of a lake in eastern Canada. Splan Lake is a 4 ha lake situated in a hollow in Palaeozoic metasedimentary rock in southern New Brunswick. Diatoms were identified and counted in a 6.98 m core, from which five developmental phases were recognized. Initially Splan Lake supported a pioneer Fragilaria assemblage comparable to that in modern arctic and glacial moraine lakes. This is believed to represent growth in the moat of a partially ice covered lake. An embryonic limnic flora consisting of Cyclotella bodanica and C. stelligera appeared ca. 11 300 y.B.P., which was terminated by the younger Dryas cool interval — ca. 11 000–10 000 y.B.P. There appeared to be no autochthonous production in Splan Lake during this latter episode. Subsequently, a C. bodanica: C. Stelligera: Navicula community developed. From ca. 8 800–5 500 y.B.P. Asterionella ralfsii v. americana, Tabellaria spp. and large numbers of chrysophyte scales occurred together with Cyclotella spp. The ‘recent’ phase is dominated by Tabellaria, Frustulia, Fragilaria, Eunotia and Navicula. The lake evolved from alkaline to slightly acid, and from oligotrophic to mesotrophic following the younger Dryas. The flora developed from benthic/littoral to a predominantly littoral/limnic community over the same period, and with continued sedimentation, into a littoral/benthic diatom community.
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    Biogenic silica as an estimate of siliceous microfossil abundance in Great Lakes sediments (1988)
    Springer
    Biogeochemistry 6 (1988), S. 161-179 
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    ISSN: 1573-515X
    Keywords: biogenic silica ; diatoms ; Great Lakes ; sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Biogenic silica concentration (BSi) in sediment cores from the Great Lakes is evaluated as an estimate of siliceous microfossil abundance. A significant linear relationship was found between measured BSi and diatom valve abundance for sediment cores from the Bay of Quinte, Lake Ontario, Lake Erie, Lake Michigan and Lake Superior and between measured BSi and diatom biovolume for Lake Erie, Lake Michigan, and Lake Superior but not for Lake Ontario. Diatom silica predicted from diatom species abundance and an estimated silica content per cell in the Lake Erie cores accounted for 117% and 103% of measured BSi, respectively. By contrast, predicted diatom silica could only account for 28% of measured BSi in the Lake Michigan core and only 25% in the Lake Superior core. A few large diatoms with a large silica content per cell comprised a major portion of predicted diatom silica in all cores. The discrepancy between chemically measured BSi and the silica predicted from diatoms in the Lake Michigan and Lake Superior cores was partially due to the inability of the regression model, used to estimate diatom silica content, to account for different degrees of silicification in the diatom asemblages from the more dissolved silica rich Lake Michigan and Lake Superior.
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    Factors controlling nitrogen mineralization and nitrification in forest ecosystems in New Mexico (1987)
    Springer
    Biology and fertility of soils 5 (1987), S. 195-202 
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    ISSN: 1432-0789
    Keywords: Nitrogen mineralization ; Nitrification ; Organic quality ; New Mexico
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Forest floor and mineral soil from ponderosa-pine, Douglas-fir, aspen and spruce-fir ecosystems located along a rising gradient in New Mexico were tested with laboratory assays for factors controlling N mineralization and nitrification. We concluded that low pH in combination with factors associated with organic quality controlled N mineralization and almost completely limited nitrification in spruce-fir soils, while N mineralization in the forest floor of ponderosa-pine was limited by low nutrient availability (other than N). Organic quality of the substrate and temporal changes in organic quality appeared to control N-mineralization and nitrification processes in forest-floor and mineral soils from all other sites.
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    URL: http://dx.doi.org/10.1007/BF00256900
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    Active methanotrophs suppress nitrification in a humisol (1987)
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    Biology and fertility of soils 4 (1987), S. 205-212 
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    ISSN: 1432-0789
    Keywords: Nitrate production ; Nitrification ; Humisol ; Methane oxidation ; Methanotrophs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The coexistence of chemoautotrophic nitrifiers and methanotrophs in a cultivated humisol was investigated. Under laboratory conditions which supported the growth and activity of methanotrophs, the nitrifiers were partially or completely inhibited. The inhibition was related to a competition for available oxygen and a high assimilatory requirement for inorganic nitrogen by the Methanotrophs. Dissolved methane concentrations as high as 250 μM had no direct effect on the oxidation of ammonium. Simultaneous nitrification and methane oxidation was observed only if relatively high levels of ammonium and oxygen were maintained. Coupled nitrification-assimilatory/dissimilatory nitrate reduction resulted from the high oxygen demand of the actively growing methanotrophs. This study suggests that the potential competitive effects of methanotrophs may influence nitrification by chemoautotrophic nitrifiers in certain environmental systems.
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    Paleolimnological evidence for recent acidification of Big Moose Lake, Adirondack Mountains, N.Y. (USA) (1987)
    Springer
    Biogeochemistry 3 (1987), S. 267-296 
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    ISSN: 1573-515X
    Keywords: Adirondacks ; lake acidification ; acid precipitation ; paleolimnology ; diatoms ; chrysophytes ; chironomids ; geochemistry ; sulfur ; PAH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Big Moose L. has become significantly more acidic since the 1950s, based on paleolimnological analyses of sediment cores. Reconstruction of past lakewater pH using diatom assemblage data indicates that from prior to 1800 to ca. 1950, lakewater pH was about 5.8. After the mid-1950s, the inferred pH decreased steadily and relatively quickly to about 4.6. Alkalinity reconstructions indicate a decrease of about 30 μeq · l-1 during the same period. There was a major shift in diatom assemblage composition, including a nearly total loss of euplanktonic taxa. Chrysophyte scale assemblages and chironomid (midge larvae remains also changed in a pattern indicating decreasing lakewater pH starting in the 1950s. Accumulation rates of total Ca, exchangeable and oxide Al, and other metals suggest recent lake-watershed acidification. Cores were dated using210Pb, pollen, and charcoal. Indicators of watershed change (deposition rates of Ti, Si, Al) do not suggest any major erosional events resulting from fires or logging. Accumulation rates of materials associated with combustion of fossil fuels (polycyclic aromatic hydrocarbons, coal and oil soot particles, some trace metals, and sulfur) are low until the late 1800s-early 1900s and increase relatively rapidly until the 1920s–1930s. Peak rates occurred between the late 1940s and about 1970, when rates declined. The recent decrease in pH of Big Moose L. cannot be accounted for by natural acidification or processes associated with watershed disturbance. The magnitude, rate and timing of the recent pH and alkalinity decreases, and their relationship to indicators of coal and oil combustion, indicate that the most reasonable explanation for the recent acidification is increased atmospheric deposition of strong acids derived from combustion of fossil fuels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02185196
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    Electronic Resource
    Electronic Resource
    Gaseous nitrogen losses from fertilized soil during nitrification and denitrification using the acetylene blockage technique (1986)
    Springer
    Biology and fertility of soils 2 (1986), S. 65-70 
    Details
    ISSN: 1432-0789
    Keywords: Fertilized soil ; Nitrification ; Denitrification ; N2O production ; C2H2 blockage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A sandy soil amended with different forms and amounts of fertilizer nitrogen (urea, ammonium sulphate and potassium nitrate) was investigated in model experiments for N2O emission, which may be evolved during both oxidation of ammonia to nitrate and anaerobic respiration of nitrate. Since C2H2 inhibits both nitrification and the reduction of N2O to N2 during denitrification, the amount of N2O evolved in the presence and absence of C2H2 represents the nitrogen released through nitrification and denitrification. Results show that amounts of N2O-N lost from soils incubated anaerobically with 0.1% C2H2 and treated with potassium nitrate (23.1 µg N-NO 3 − /g dry soil) exceeded those from soils incubated in the presence of 20% oxygen and treated with even larger amounts of nitrogen as urea and ammonium sulphate. This indicates that nitrogen losses by denitrification may potentially be higher than those occurring through nitrification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00257581
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