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  • 1
    Electronic Resource
    Electronic Resource
    Nitrogen storage (communication arising) UV-B radiation and soil microbial communities (2003)
    [s.l.] : Nature Publishing Group
    Nature 423 (2003), S. 137-138 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Soil microorganisms regulate the supply of nitrogen to plants and so are important controllers of plant productivity and ecosystem carbon sequestration. Johnson et al. report that exposure of a subarctic heath ecosystem to increased ultraviolet-B (UV-B) irradiation causes a drastic decline in ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/423137a
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  • 2
    Electronic Resource
    Electronic Resource
    High rates of nitrification and nitrate turnover in undisturbed coniferous forests (1997)
    [s.l.] : Nature Publishing Group
    Nature 385 (1997), S. 61-64 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Studies examining nitrogen retention in forest ecosystems have focused on net nitrification, net mineralization, microbial assimilation of ammonium (NHJ), and plant uptake; however, microbial assimilation of NO has been largely ignored. Early studies showed that soil microbial communities prefer NH ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/385061a0
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  • 3
    Electronic Resource
    Electronic Resource
    Transferring soils from high- to low-elevation forests increases nitrogen cycling rates: climate change implications (1999)
    Oxford, UK : Blackwell Science, Ltd
    Global change biology 5 (1999), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: We assessed the potential impact of global warming resulting from a doubling of preindustrial atmospheric CO2 on soil net N transformations by transferring intact soil cores (0–15 cm) from a high-elevation old-growth forest to a forest about 800 m lower in elevation in the central Oregon Cascade Mountains, USA. The lower elevation site had mean annual air and soil (10-cm mineral soil depth) temperatures about 2.4 and 3.9 °C higher than the high-elevation site, respectively. Annual rates of soil net N mineralization and nitrification more than doubled in soil transferred to the low-elevation site (17.2–36.0 kg N ha–1 and 5.0–10.7 kg NO3––N ha–1, respectively). Leaching of inorganic N from the surface soil (in the absence of plant uptake) also increased. The reciprocal treatment (transferring soil cores from the low- to the high-elevation site) resulted in decreases of about 70, 80, and 65% in annual rates of net N mineralization, nitrification, and inorganic N leaching, respectively. Laboratory incubations of soils under conditions of similar temperature and soil water potential suggest that the quality of soil organic matter is higher at the high-elevation site. Similar in situ rates of soil net N transformations between the two sites occurred because the lower temperature counteracts the effects of greater substrate quantity and quality at the high elevation site. Our results support the hypothesis that high-elevation, old-growth forest soils in the central Cascades have higher C and N storage than their low-elevation analogues primarily because low temperatures limit net C and N mineralization rates at higher elevations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.1998.00196.x
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  • 4
    Electronic Resource
    Electronic Resource
    Modeling Ecological Restoration Effects on Ponderosa Pine Forest Structure (2001)
    Boston, MA, USA : Blackwell Science Inc
    Restoration ecology 9 (2001), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: FIRESUM, an ecological process model incorporating surface fire disturbance, was modified for use in southwestern ponderosa pine ecosystems. The model was used to determine changes in forest structure over time and then applied to simulate changes in aboveground biomass and nitrogen storage since exclusion of the natural frequent fire regime in an unharvested Arizona forest. Dendroecological reconstruction of forest structure in 1876, prior to Euro-American settlement, was used to initialize the model; projections were validated with forest measurements in 1992. Biomass allocations shifted from herbaceous plants to trees, and nitrogen was increasingly retained in living and dead tree biomass over the 116-year period (1876–1992). Forest conditions in 1992 were substantially degraded compared to reference presettlement conditions: old-growth trees were dying at accelerated rates, herbaceous production was reduced nearly 90%, and the entire stand was highly susceptible to high-intensity wildfire. Following an experiment initiated in 1993 to test ecological restoration treatments, future changes were modeled for the next century. Future forest structure remained within the natural presettlement range of variability under the full restoration treatment, in which forest biomass structure was thinned to emulate presettlement conditions and repeated low-intensity fire was reintroduced. Simulation of the control treatment indicated continuation of exceptionally high tree density, probably culminating in stand-replacing ecosystem change through high-intensity wildfire or tree mortality from pathogens. Intermediate results were observed in the partial restoration treatment (tree thinning only); the open forest structure and high herbaceous productivity found immediately after treatment were gradually degraded as dense tree cover reestablished in the absence of fire. Modeling results support comprehensive restorative management as a long-term approach to conservation of key indigenous ecosystem characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1526-100X.2001.94011.x
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  • 5
    Electronic Resource
    Electronic Resource
    Water and Nutrient Outflow Following the Ecological Restoration of a Ponderosa Pine-Bunchgrass Ecosystem (1999)
    Boston, MA, USA : Blackwell Science Inc
    Restoration ecology 7 (1999), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In the late 1800s, fire suppression, livestock grazing, and a wet and warm climate led to an irruption of pine regeneration in Pinus ponderosa Laws. (ponderosa pine) forests of the southwestern United States. Pines invaded bunchgrass openings, causing stand structure changes that increased the number of stand-replacing fires. Ecological restoration, via thinning and prescribed burning, is being used to decrease the risk of stand-replacing fires and ameliorate other effects of pine invasion. The effects of aboveground restoration on belowground processes are poorly understood. We used a hydrologic model and soil water nutrient concentrations, measured monthly below the rooting zone, to estimate restoration effects on nutrient losses by leaching from a mature ponderosa pine forest near Flagstaff, Arizona. Replicated restoration treatments included thinning to pre-1880 stand densities (partial restoration), thinning plus forest floor fuel reduction followed by a prescribed burn (complete restoration), and an untreated control. Water outflow occurred only between January and May and was lowest from the control (47 and 28 mm in 1995 and 1996) and highest from the partial restoration treatment (67 and 59 mm in 1995 and 1996). The concentrations (typically 〈0.10 mg/ L) and estimated annual losses (〈0.02 kg/ha) of NH4+-N, PO43−-P, and organic P were similar among treatments. Nitrate and organic N concentrations were as high as 0.80 mg N/L; however, these concentrations and estimated annual losses (〈0.13 kg N/ha) were similar among treatments. Our results suggest that restoration will not enhance nutrient loss by leaching or alter stream chemistry in ponderosa pine forests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1526-100X.1999.72018.x
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  • 6
    Electronic Resource
    Electronic Resource
    Call in Spanish the Consumers' View (1990)
    Cambridge : Cambridge University Press
    Recall 2 (1990), S. 10-12 
    Details
    ISSN: 0958-3440
    Source: Cambridge Journals Digital Archives
    Topics: Linguistics and Literary Studies , Computer Science
    Notes: In any language-teaching institution the teaching staff can legitimately be seen as consumers of the various teaching aids which are commercially available, ranging from the staple diet of books, set texts, secondary reading, to video material, slides, computer software, etc. Another way of interpreting the principle of consumership is that the students are the ultimate beneficiaries of the materials we use in our teaching. The extent to which our students benefit from our teaching is largely dependent on the materials that we have at our disposal. ‘Bad materials = bad teaching’ is a rather simplistic way of looking at this issue, but one which has a lot to commend itself in my view. Would we change our teaching methods if our students made constructive criticism? In a recent temporary teaching post I held as Visiting Associate Professor at the University of Kentucky, I was struck by the importance given across the board in the USA to official student surveys carried out by the college administration based on the professors' performance, the results of which can be crucial in the securement of tenure. The attitude in the UK (at least in the universities) is totally at odds with this particular sense of consumership, and one can imagine the degree of resistance that a plan to introduce a similar system of student assessment of lecturers might meet in this country, most obviously because students are not consumers in this country in quite the same sense that they are in the USA. Although the student assessment system itself clearly has its pitfalls there are some positive things to be gained from surveys of this kind, in that they can be very informative about student response to courses, teaching methods, etc., and can lead the way to improved teacher-student relations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1017/S0958344000002354
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  • 7
    Electronic Resource
    Electronic Resource
    Community-level physiological profiles of bacteria and fungi: plate type and incubation temperature influences on contrasting soils (2003)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 44 (2003), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Temperature sensitivity of community-level physiological profiles (CLPPs) was examined for two semiarid soils from the southwestern United States using five different C-substrate profile microtiter plates (Biolog GN2, GP2, ECO, SFN2, and SFP2) incubated at five different temperature regimes. The CLPPs produced from all plate types were relatively unaffected by these contrasting incubation temperature regimes. Our results demonstrate the ability to detect CLPP differences between similar soils with differing physiological parameters, and these differences are relatively insensitive to incubation temperature. Our study also highlights the importance of using both bacterial and fungal plate types when investigating microbial community differences by CLPP. Nevertheless, it is unclear whether or not the differences in CLPPs generated using these plates reflect actual functional differences in the microbial communities from these soils in situ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0168-6496(03)00068-0
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  • 8
    Electronic Resource
    Electronic Resource
    Restoration and Canopy-Type Effects on Soil Respiration in a Ponderosa Pine–Bunchgrass Ecosystem (1998)
    Springer
    Soil Science Society of America journal 62 (1998), S. 1062-1072 
    Details
    ISSN: 1435-0661
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Pinus ponderosa Douglas ex P. Lawson & Lawson)-bunchgrass ecosystems of the western USA, fire exclusion by Euro-American settlers facilitated pine invasion of grassy openings, increased forest floor detritus, and shifted the disturbance regime toward stand-replacing fires, motivating ecological restoration through thinning and prescribed burning. We used in situ soil respiration over a 2-yr period to assess belowground responses to pine invasion and restoration in a ponderosa pine-bunchgrass ecosystem near Flagstaff, AZ. Replicated restoration treatments were: (i) partial restoration—thinning to presettlement conditions; (ii) complete restoration—removing trees and forest floor material to presettlement conditions, native grass litter addition, and prescribed burning; and (iii) control. Within treatments, we sampled beneath different canopy types to assess the effects of pine invasion into grassy openings on soil respiration. Growing season soil respiration was greater in the complete restoration (346 ± 24 g CO2−C m–2) and control (350 ± 8 g CO2−C m–2) than the partial restoration (301 ± 5 g CO2−C m–2) in 1995. In 1996, the complete (364 ± 17 g CO2−C m–2) and partial (328 ± 7 g CO2−C m–2) restoration treatments had greater growing season respiration rates than the control (302 ± 13 g CO2−C m–2). Results suggest that restoration effects on soil respiration depend on interannual soil water patterns and may not significantly alter regional C cycles. Soil respiration from grassy openings was 15% greater than from soil beneath presettlement of postsettlement pines in 1995 and 1996. A lack of active management will decrease belowground catabolism if pines continue to expand at the expense of grassy openings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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  • 9
    Electronic Resource
    Electronic Resource
    Forest floor-mineral soil interactions in the internal nitrogen cycle of an old-growth forest (1991)
    Springer
    Biogeochemistry 12 (1991), S. 103-127 
    Details
    ISSN: 1573-515X
    Keywords: fungal translocation ; microbial biomass ; 15N ; N leaching ; N mineralizaton ; nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Seasonal patterns and annual rates of N inputs, outputs, and internal cycling were determined for an old-growth mixed-conifer forest floor in the Sierra Nevada Mountains of California. Rates of net N mineralization within the forest floor, and plant N-uptake and leaching of inorganic N from the forest floor were 13, 10, and 9 kg-N ha-1 yr-1, respectively. The Mediterranean-type climate appeared to have a significant effect on N cycling within this forest, such that all N-process and flow rates showed distrinct seasonal patterns. We estimated the forest floor supplies less than one-third of the total aboveground plant N-uptake in this forest. The rate of net nitrification within the forest floor was always low (1 kg-NO3 --N ha-1 30d-1). Mean residence times for organic matter and N in the forest floor were 13 and 34 years, respectively, suggesting that this forest floor layer is a site of net N immobilization within this ecosystem. We examined the influence of the forest floor on mineral soil N dynamics by injecting small amounts of15N-enriched (NH4)2SO4 solutions into the surface mineral soil with the forest floor present (+FF) or removed (-FF). K2SO4-extractable NO3 --N, total inorganic-N, and total-N pool sizes in the mineral soil were initially increased after forest floor removal (after 4 months), but NO3 --N and total inorganic-N were not significantly different thereafter. Microbial biomass-N and K2SO4-extractable total-N pool sizes were also found to be larger in mineral soils without a forest floor after 1 and 1.3 years, respectively. Total15N-recovery was greater in the +FF treatment compared to the -FF treatment after 1-year (about 50% and 35%, respectively) but did not differ after 1.3 years (both about 35%), suggesting that the forest floor delays but does not prevent the N-loss from the surface mineral soil of this forest. We estimated using our15N data that fungal translocation from the mineral soil to the forest floor may be as large as 9 kg-N ha-1 yr-1 (similar in magnitude to other N flows in this forest), and may account for all of the observed absolute increase of N in litter during the early stages of decomposition at this site. Our results suggest that the forest floor acts both as a source and sink for N in the mineral soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00001809
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  • 10
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    Changes in belowground biodiversity during ecosystem development (2019)
    National Academy of Sciences
    Details
    Publication Date: 2019-03-15
    Description: Belowground organisms play critical roles in maintaining multiple ecosystem processes, including plant productivity, decomposition, and nutrient cycling. Despite their importance, however, we have a limited understanding of how and why belowground biodiversity (bacteria, fungi, protists, and invertebrates) may change as soils develop over centuries to millennia (pedogenesis). Moreover, it is unclear whether belowground biodiversity changes during pedogenesis are similar to the patterns observed for aboveground plant diversity. Here we evaluated the roles of resource availability, nutrient stoichiometry, and soil abiotic factors in driving belowground biodiversity across 16 soil chronosequences (from centuries to millennia) spanning a wide range of globally distributed ecosystem types. Changes in belowground biodiversity during pedogenesis followed two main patterns. In lower-productivity ecosystems (i.e., drier and colder), increases in belowground biodiversity tracked increases in plant cover. In more productive ecosystems (i.e., wetter and warmer), increased acidification during pedogenesis was associated with declines in belowground biodiversity. Changes in the diversity of bacteria, fungi, protists, and invertebrates with pedogenesis were strongly and positively correlated worldwide, highlighting that belowground biodiversity shares similar ecological drivers as soils and ecosystems develop. In general, temporal changes in aboveground plant diversity and belowground biodiversity were not correlated, challenging the common perception that belowground biodiversity should follow similar patterns to those of plant diversity during ecosystem development. Taken together, our findings provide evidence that ecological patterns in belowground biodiversity are predictable across major globally distributed ecosystem types and suggest that shifts in plant cover and soil acidification during ecosystem development are associated with changes in belowground biodiversity over centuries to millennia.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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