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  • 1
    Electronic Resource
    Electronic Resource
    Effects of available P and N:P ratios on non-symbiotic dinitrogen fixation in tallgrass prairie soils (1989)
    Springer
    Oecologia 79 (1989), S. 471-474 
    Details
    ISSN: 1432-1939
    Keywords: Cyanobacteria ; Fire ; Acetylene reduction ; Ash
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Prescribed burning is a major control over element cycles in Tallgrass prairie (Eastern Kansas, USA). In this paper we report potential effects of fire on nonsymbiotic nitrogen fixation. Fire resulted in additions of available P in ash, which may stimulate nitrogen fixation by terrestrial cyanobacteria. Cyanobacterial nitrogenase activity and biomass responded positively to additions of ash or P in laboratory assays using soil. Further assays in soil showed that cyanobacteria responded to changes in available N:available P ratio (aN:P) across a range of concentrations. Nitrogen fixation rate could be related empirically to aN:P via a log-linear relationship. Extrapolation of laboratory results to the field yielded a maximal estimate of 21 kg N ha-1 y-1. Results support arguments from the marine and terrestrial literature that P availability is central to regulation of ecosystem N budgets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378663
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  • 2
    Electronic Resource
    Electronic Resource
    Factors influencing ammonia volatilization from urea in soils of the shortgrass steppe (1988)
    Springer
    Journal of atmospheric chemistry 6 (1988), S. 323-340 
    Details
    ISSN: 1573-0662
    Keywords: Volatilization ; hydrolysis ; urea ; ammonia ; landscape ; water loss ; abiotic controls ; gas flux
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The effects of soil moisture, temperature, and humidity treatments on urea hydrolysis and NH3 volatilization were assessed in the laboratory. Field studies were conducted to determine seasonal NH3 losses from simulated urine patches applied to contrasting soils of a representative hillslope of the shortgrass steppe region in the North American Great Plains. Losses of NH3−N were most influenced by soil moisture. The effects of temperature and humidity on total, or temporal, losses of NH3 were dependent on soil moisture. Losses ranged from 18.5% under conditions of low-temperature/high-humidity/wet soil to 7.7% under conditions of high-temperature/low-humidity/dry soil. In contrast, urea hydrolysis was not affected by soil moisture. Losses of NH3−N from simulated urine applied to field plots ranged from 1.5% on footslope soils in summer to 14.1% on backslope (midslope) soils in summer, whereas losses were 8.1% on back-slope soils in winter. Factors such as soil texture, microbial activity, and plant productivity along a toposequence had larger effects than climatic variables on variation in the volatile losses of NH3−N from this grassland.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00051595
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  • 3
    Electronic Resource
    Electronic Resource
    Calculation of microbial growth efficiency from15N immobilization (1988)
    Springer
    Biogeochemistry 6 (1988), S. 239-243 
    Details
    ISSN: 1573-515X
    Keywords: grassland ; agroecosystems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Microbial growth rate was estimated by multiplying15N immobilization by an estimated microbial C:N ratio. This growth rate, in combination with measurements of respiration, was used to calculate growth efficiency. Growth rates and efficiencies were calculated for grassland and cultivated soils of three textures. Calculated efficiencies (Yc), assuming a microbial C: N ratio of 7, ranged from 32 to 54. Cultivated soils tended to have higher Yc values than did grassland soils. This calculation depends on several hard-to-verify assumptions, but yields numbers that should be of great interest in comparative studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02182998
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  • 4
    Electronic Resource
    Electronic Resource
    Microclimatic controls of nitrogen mineralization and nitrification in shortgrass steppe soils (1986)
    Springer
    Plant and soil 93 (1986), S. 347-357 
    Details
    ISSN: 1573-5036
    Keywords: Dew ; Grasslands ; Nitrification ; Nitrogen ; Semiarid ecosystems ; Soil texture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The depth distributions of rates of net nitrogen mineralization and nitrification were measured in a series of field and laboratory incubations. Field studies suggested that the highest rates of mineralization and nitrification occurred in the surface 2.5 cm such that forty to sixty percent of the N mineralization in 20-cm soil column occurred in the surface 2.5cm. Some upward nitrate movement occurred but laboratory studies suggested that surface rates were not an artifact of nitrate mobility alone. Microclimatic data indicate that either dew or upward movement and condensation of soil water vapor may drive biological activity at the soil surface. High rates of N mineralization even in dry horizons were sustained as long as water was stored within the 0-to 20-cm depth. High rates of nitrification were found in all incubations, and field measurements showed NO 3 − to be the predominant form of inorganic N, despite previous characterization of the shortgrass steppe as an NH 4 + -dominated system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02374285
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  • 5
    Electronic Resource
    Electronic Resource
    Grassland biogeochemistry: Links to atmospheric processes (1990)
    Springer
    Climatic change 17 (1990), S. 13-25 
    Details
    ISSN: 1573-1480
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Regional modeling is an essential step in scaling plot measurements of biogeochemical cycling to global scales for use in coupled atmosphere-biosphere studies. We present a model of carbon and nitrogen biogeochemistry for the U.S. Central Grasslands region based on laboratory, field, and modeling studies. Model simulations of the geography of C and N biogeochemistry adequately fit observed data. Model results show geographic patterns of cycling rates and element storage to be a complex function of the interaction of climatic and soil properties. The model also includes regional trace gas simulation, providing a link between studies of atmospheric geochemistry and ecosystem function. The model simulates nitrogenous trace gas emission rates as a function of N turnover and indicates that they are variable across the grasslands. We studied effects of changing climate using information from a global climate model. Simulations showed that increases in temperature and associated changes in precipitation caused increases in decomposition and long-term emission of Co2 from grassland soils. Nutrient release associated with the loss of soil organic matter caused increases in net primary production, demonstrating that nutrient interactions are a major control over vegetation response to climate change.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00148998
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  • 6
    Electronic Resource
    Electronic Resource
    Long- and short-term effects of fire on nitrogen cycling in tallgrass prairie (1994)
    Springer
    Biogeochemistry 24 (1994), S. 67-84 
    Details
    ISSN: 1573-515X
    Keywords: carbon ; fire ; immobilization ; mineralization ; nitrogen use efficiency ; soil organic matter ; tallgrass prairie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Fires in the tallgrass prairie are frequent and significantly alter nutrient cycling processes. We evaluated the short-term changes in plant production and microbial activity due to fire and the long-term consequences of annual burning on soil organic matter (SOM), plant production, and nutrient cycling using a combination of field, laboratory, and modeling studies. In the short-term, fire in the tallgrass prairie enhances microbial activity, increases both above-and belowground plant production, and increases nitrogen use efficiency (NUE). However, repeated annual burning results in greater inputs of lower quality plant residues causing a significant reduction in soil organic N, lower microbial biomass, lower N availability, and higher C:N ratios in SOM. Changes in amount and quality of below-ground inputs increased N immobilization and resulted in no net increases in N availability with burning. This response occurred rapidly (e.g., within two years) and persisted during 50 years of annual burning. Plant production at a long-term burned site was not adversely affected due to shifts in plant NUE and carbon allocation. Modeling results indicate that the tallgrass ecosystem responds to the combined changes in plant resource allocation and NUE. No single factor dominates the impact of fire on tallgrass plant production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02390180
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  • 7
    Electronic Resource
    Electronic Resource
    Rates and pathways of nitrous oxide production in a shortgrass steppe (1988)
    Springer
    Biogeochemistry 6 (1988), S. 45-58 
    Details
    ISSN: 1573-515X
    Keywords: N2O ; model ; annual emission ; long-term estimate ; N mineralization ; nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Most of the small external inputs of N to the Shortgrass steppe appear to be conserved. One pathway of loss is the emission of nitrous oxide, which we estimate to account for 2.5–9.0% of annual wet deposition inputs of N. These estimates were determined from an N2O emission model based on field data which describe the temporal variability of N2O produced from nitrification and denitrification from two slope positions. Soil water and temperature models were used to translate records of air temperature and precipitation between 1950 and 1984 into variables appropriate to drive the gas flux model, and annual N2O fluxes were estimated for that period. The mean annual fluxes were 80 g N ha−1 for a midslope location and 160 g N ha−1 for a swale. Fluxes were higher in wet years than in dry, ranging from 73 to 100 g N ha−1y−1at the midslope, but the variability was not high. N2O fluxes were also estimated from cattle urine patches and these fluxes while high within a urine patch, did not contribute significantly to a regional budget. Laboratory experiments using C2H2 to inhibit nitrifiers suggested that 60–80% of N2O was produced as a result of nitrification, with denitrification being less important, in contrast to our earlier findings to the contrary. Intrasite and intraseasonal variations in N2O flux were coupled to variations in mineral N dynamics, with high rates of N2O flux occurring with high rates of inorganic N turnover. We computed a mean flux of 104 g N ha−1 y−1 from the shortgrass landscape, and a flux of 2.6 × 109 g N y− from all shortgrass steppe (25 × 106 ha).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00002932
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  • 8
    Electronic Resource
    Electronic Resource
    Long term 15N studies in a catena of the shortgrass steppe (1996)
    Springer
    Biogeochemistry 32 (1996), S. 41-52 
    Details
    ISSN: 1573-515X
    Keywords: nitrogen ; particulate organic matter ; nutrient cycling ; grassland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A set of long term15N studies was initiated during the summers of 1981 and 1982 on the backslope and footslope, respectively, of a catena in the shortgrass steppe of northeastern Colorado. Microplots labeled with15N urea were sampled for15N and total N content in 1981 and 1982 and again in 1992. In November, 1982, 100% of the added N was recovered in the soil-plant system of the finer-textured footslope, compared to 39% in the coarser-textured backslope microplots. Ten years later,15N recovery of the applied N decreased at both topographic positions to 85% in the footslope and 29% in the backslope. Average losses since the time of application were 3.5 g N m−2yr−1 in the backslope and 0.8 g N m−2yr−1 in the footslope. In 1992, soil organic matter was physically fractionated into particulate (POM) and mineral associated (MAON) fractions and 21-day mineralization incubations were conducted to assess the relative amounts of15N that were in the slow, passive and active soil organic matter pools, respectively, of the two soils. Our findings confirm the assumptions that POM represents a large portion of the slow organic compartment and that the MAON represents a large fraction of the passive compartment defined in the Century model. The N located in the MAON had the lowest availability for plant uptake. Isotopic data were consistent with textural effects and with the Century model compartmentalization of soil organic N based on the residence time of the organic N.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00001531
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  • 9
    Electronic Resource
    Electronic Resource
    The role of cattle in the volatile loss of nitrogen from a shortgrass steppe (1986)
    Springer
    Biogeochemistry 2 (1986), S. 39-52 
    Details
    ISSN: 1573-515X
    Keywords: NH 0 3 volatilization ; denitrification ; grazing ; spatial heterogeneity ; translocation ; nitrification ; leaching ; urine ; feces ; 15N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The cycling and volatile loss of N derived from cattle urine at upland and lowland sites within the shortgrass steppe of eastern Colorado was studied, using15N-labelled urea as an N source. Losses of NH 0 3 were determined by direct measurement and by difference. Losses were higher from coarse (27% summer, 12% winter) than from fine textured (0–2%) soils. Immobilization and plant uptake of N accounted for significant amounts of added N. Extrapolating our plot measurements to a typical pasture, using spatially and temporally stratified urine deposition data, losses from upland sites were calculated to be 0.016 g N · m-2 · y-1, while losses from lowland sites were negligible. This resulted in an average loss of 0.011 g N · m-2 · y-1 for a pasture divided 70:30 between uplands and lowlands. The loss of urine N calculated assuming no spatial stratification would be sevenfold higher (0.076 g N · m-2 · y-1). Losses of NH 0 3 from urine, animal biomass removal, and NH2O loss totaled only 0.07 g N · m-2 · y-1 , or about 25% of wet deposition input. We calculated a potential loss of NH 0 3 from senescing vegetation of 0.26 g N · m-2 · y-1, an order of magnitude larger than all other losses combined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02186964
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  • 10
    Electronic Resource
    Electronic Resource
    Long- and short-term effects of fire on nitrogen cycling in tallgrass prairie (1994)
    Springer
    Biogeochemistry 24 (1994), S. 67-84 
    Details
    ISSN: 1573-515X
    Keywords: carbon ; fire ; immobilization ; mineralization ; nitrogen use efficiency ; soil organic matter ; tallgrass prairie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Fires in the tallgrass prairie are frequent and significantly alter nutrient cycling processes. We evaluated the short-term changes in plant production and microbial activity due to fire and the long-term consequences of annual burning on soil organic matter (SOM), plant production, and nutrient cycling using a combination of field, laboratory, and modeling studies. In the short-term, fire in the tallgrass prairie enhances microbial activity, increases both above-and belowground plant production, and increases nitrogen use efficiency (NUE). However, repeated annual burning results in greater inputs of lower quality plant residues causing a significant reduction in soil organic N, lower microbial biomass, lower N availability, and higher C:N ratios in SOM. Changes in amount and quality of below-ground inputs increased N immobilization and resulted in no net increases in N availability with burning. This response occurred rapidly (e.g., within two years) and persisted during 50 years of annual burning. Plant production at a long-term burned site was not adversely affected due to shifts in plant NUE and carbon allocation. Modeling results indicate that the tallgrass ecosystem responds to the combined changes in plant resource allocation and NUE. No single factor dominates the impact of fire on tallgrass plant production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00000002
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