SOIL MICROBES COMPETE EFFECTIVELY WITH PLANTS FOR ORGANIC-NITROGEN INPUTS TO TEMPERATE GRASSLANDS

作者：Richard D. Bardgett, Tania C. Streeter, Roland A. Bol · 发表于：Ecology · 年份：2003 · DOI：10.1890/0012-9658(2003)084[1277:smcewp]2.0.co;2 · 被引用次数：390 · 研究领域：Soil Carbon and Nitrogen Dynamics、Legume Nitrogen Fixing Symbiosis、Plant nutrient uptake and metabolism

Although agricultural grassland soils have inherently high rates of net nitrogen (N) mineralization, they often have soil concentrations of soluble organic N that are comparable to inorganic N. We set out to examine in situ the significance of organic N for plant nutrition in grasslands of differing management intensity and soil fertility. Using in situ dual-labeling techniques (glycine-2-13C-15N) we measured preferential uptake of amino-acid N vs. inorganic N [(15NH4)2SO4] in early and late season in low-productivity Agrostis capillaris–Festuca ovina grassland and in agriculturally improved, high-productivity Lolium perenne-dominated grassland. The dominant soluble-N form differed greatly between grasslands. Inorganic N (especially nitrate N) dominated the soluble N pool of the highly productive improved grassland whereas amino acid N was the dominant soluble N form in the low-productivity unimproved grassland. There was no difference in the amount of 15N taken up by plants from the two N forms in either grassland. However, our data indicate that amino-acid N was taken up directly by plants of both grasslands and that more N was captured in this way by plants of low-productivity grassland where amino acids were the dominant soluble N form in soil. Our data from both grasslands also indicate significant microbial competition for added 15N from both N sources, but especially in the low-productivity grassland where the bulk of 15N added was sequestered by the microbial biomass....