Controls on nitrogen cycling in terrestrial ecosystems : a synthetic analysis of literature data
MetadataShow full item record
KeywordAmmonium; N assimilation; N immobilization; N-15 isotope dilution; N mineralization; Nitrate; Nitrification; Soil carbon; Soil nitrogen; Soil organic matter; Soil pH
Isotope pool dilution studies are increasingly reported in the soils and ecology literature as a means of measuring gross rates of nitrogen (N) mineralization, nitrification, and inorganic N assimilation in soils. We assembled data on soil characteristics and gross rates from 100 studies conducted in forest, shrubland, grassland, and agricultural systems to answer the following questions: What factors appear to be the major drivers for production and consumption of inorganic N as measured by isotope dilution studies? Do rates or the relationships between drivers and rates differ among ecosystem types? Across a wide range of ecosystems, gross N mineralization is positively correlated with microbial biomass and soil C and N concentrations, while soil C:N ratio exerts a negative effect on N mineralization only after adjusting for differences in soil C. Nitrification is a log-linear function of N mineralization, increasing rapidly at low mineralization rates but changing only slightly at high mineralization rates. In contrast, NH4+ assimilation by soil microbes increases nearly linearly over the full range of mineralization rates. As a result, nitrification is proportionately more important as a fate for NH4+ at low mineralization rates than at high mineralization rates. Gross nitrification rates show no relationship to soil pH, with some of the fastest nitrification rates occurring below pH 5 in soils with high N mineralization rates. Differences in soil organic matter (SOM) composition and concentration among ecosystem types influence the production and fate of mineralized N. Soil organic matter from grasslands appears to be inherently more productive of ammonium than SOM from wooded sites, and SOM from deciduous forests is more so than SOM in coniferous forests, but differences appear to result primarily from differing C:N ratios of organic matter. Because of the central importance of SOM characteristics and concentrations in regulating rates, soil organic matter depletion in agricultural systems appears to be an important determinant of gross process rates and the proportion of NH4+ that is nitrified. Addition of 15N appears to stimulate NH4+ consumption more than NO3− consumption processes; however, the magnitude of the stimulation may provide useful information regarding the factors limiting microbial N transformations.
Author Posting. © Ecological Society of America, 2005. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Monographs 75 (2005): 139–157, doi:10.1890/04-0988.
Showing items related by title, author, creator and subject.
Cole, Marci L.; Kroeger, Kevin D.; McClelland, James W.; Valiela, Ivan (2005-07-18)Eutrophication is a major agent of change affecting freshwater, estuarine, and marine systems. It is largely driven by transportation of nitrogen from natural and anthropogenic sources. Research is needed to quantify ...
Phosphate availability and the ultimate control of new nitrogen input by nitrogen fixation in the tropical Pacific Ocean Moutin, T.; Karl, David M.; Duhamel, Solange; Rimmelin, P.; Raimbault, P.; Van Mooy, Benjamin A. S.; Claustre, Hervé (Copernicus Publications on behalf of the European Geosciences Union, 2008-01-29)Due to the low atmospheric input of phosphate into the open ocean, it is one of the key nutrients that could ultimately control primary production and carbon export into the deep ocean. The observed trend over the last 20 ...
Iron availability limits the ocean nitrogen inventory stabilizing feedbacks between marine denitrification and nitrogen fixation Moore, J. Keith; Doney, Scott C. (American Geophysical Union, 2007-04-04)Recent upward revisions in key sink/source terms for fixed nitrogen (N) in the oceans imply a short residence time and strong negative feedbacks involving denitrification and N fixation to prevent large swings in the ocean ...