Cross-ecosystem comparisons of in situ plant uptake of amino acid-N and NH₄⁺

Abstract

Plant and microbial use of nitrogen (N) can be simultaneously mutualistic and competitive, particularly in ecosystems dominated by mycorrhizal fungi. Our goal was to quantify plant uptake of organic and inorganic N across a broad latitudinal gradient of forest ecosystems that varied with respect to overstory taxon, edaphic characteristics, and dominant mycorrhizal association. Using ^l3C and ^l5N, we observed in situ the cycling dynamics of NH₄⁺ and glycine through various soil pools and fine roots over 14 days. Recovery of ^l5N as soil N varied with respect to N form, forest type, and sampling period; however, there were similarities in the cycling dynamics of glycine and NH₄⁺ among all forest types. Microbial immobilization of ^l5N was immediately apparent for both treatments and represented the largest sink (~25%) for ^l5N among extractable soil N pools during the first 24 h. In contrast, fine roots were a relatively small sink (

Citation

McFarland, Jack W.; Ruess, Roger W.; Kielland, Knut; Pregitzer, Kurt; Hendrick, Ronald; Allen, Michael. 2010. Cross-ecosystem comparisons of in situ plant uptake of amino acid-N and NH₄⁺. Ecosystems. 13: 177-193.