The mineralization/immobilization of nitrogen when organic sources are added to soil is represented in many simulation models as the outcome of decomposition of the added material and synthesis of soil organic matter. These models are able to capture the pattern of N release that is attributable to the N concentration of plant materials, or more generally the C:N ratio of the organic input. How...

The growing awareness that plants might use a variety of nitrogen (N) forms, both organic and inorganic, has raised questions about the role of resource partitioning in plant communities. It has been proposed that coexisting plant species might be able to partition a limited N pool, thereby avoiding competition for resources, through the uptake of different chemical forms of N. In this study, w...

Microbial communities and their associated enzyme activities affect the amount and chemical quality of carbon (C) in soils. Increasing nitrogen (N) deposition, particularly in N-rich tropical forests, is likely to change the composition and behavior of microbial communities and feed back on ecosystem structure and function. This study presents a novel assessment of mechanistic links between mic...

Human-induced increases in nitrogen (N) deposition are common across many terrestrial ecosystems worldwide. Greater N availability not only reduces biological diversity, but also affects the biogeochemical coupling of carbon (C) and N cycles in soil ecosystems. Soils are the largest active terrestrial C pool and N deposition effects on soil C sequestration or release could have global importanc...

The availability of inorganic N has been shown to be one of the major factors limiting primary productivity in high latitude ecosystems. The factors regulating the rate of transformation of organic N to nitrate and ammonium, however, remain poorly understood. The aim of this study was to investigate the nature of the soluble N pool in forest soils and to determine the relative rate of inorganic...

Micro–N pool dilution was used to quantify rates of gross N mineralization, consumption, and nitrification in bulk soil and in soil within 2 mm of root sections of Avena barbata (slender wild oats), an annual grass common to California oak woodland-savannas. Rates of gross N mineralization in rhizosphere soil (9.2 mg N kgd) were about ten times higher than in bulk soil (1.0 mg N kgd). Total bac...

Uncertainty in soil carbon (C) fluxes across different land-use transitions is an issue that needs to be addressed for the further deployment of perennial bioenergy crops. A large-scale short-rotation coppice (SRC) site with poplar (Populus) and willow (Salix) was established to examine the land-use transitions of arable and pasture to bioenergy. Soil C pools, output fluxes of soil CO 2, CH 4, ...

a function of time (Kirkham and Bartholomew, 1954, 1955; Hart et al., 1994b). This approach is currently An assumption inherent in isotope dilution methodologies is that preferred over tracer experiments to estimate reaction of homogeneous distribution of label. This assumption may not hold, rates because it is thought that inflating the product pool however, because of mass transfer limitation...

Nitrate immobilization into organic matter is thought to require catalysis by the enzymes of soil microorganisms. However, recent studies suggest that nitrate added to soil is immobilized rapidly and this process may include abiotic pathways. We amended living and sterilized soil with 15N-labeled nitrate and nitrite to investigate biotic and abiotic immobilization. We report rapid transformatio...

Soil is one of the most important carbon (C) and nitrogen (N) pools and plays a crucial role in ecosystem C and N cycling. Climate change profoundly affects soil C and N storage via changing C and N inputs and outputs. However, the influences of climate warming and changing precipitation regime on labile and recalcitrant fractions of soil organic C and N remain unclear. Here, we investigated so...