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Increasing plant use of organic nitrogen with elevation is reflected in nitrogen uptake rates and ecosystem δ 15 N
Author(s) -
Averill Colin,
Finzi Adrien
Publication year - 2011
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/10-0746.1
Subject(s) - nitrogen , ecosystem , ecology , environmental science , nitrogen cycle , elevation (ballistics) , environmental chemistry , chemistry , biology , mathematics , organic chemistry , geometry
It is hypothesized that decreasing mean annual temperature and rates of nitrogen (N) cycling causes plants to switch from inorganic to organic forms of N as the primary mode of N nutrition. To test this hypothesis, we conducted field experiments and collected natural‐abundance δ 15 N signatures of foliage, soils, and ectomycorrhizal sporocarps along a steep elevation–climate gradient in the White Mountains, New Hampshire, USA. Here we show that with increasing elevation organic forms of N became the dominant source of N taken up by hardwood and coniferous tree species based on dual‐labeled glycine uptake analysis, an important confirmation of an emerging theory for the biogeochemistry of the N cycle. Variation in natural abundance foliar δ 15 N with elevation was also consistent with increasing organic N uptake, though a simple, mass balance model demonstrated that the uptake of δ 15 N depleted inorganic N, rather than fractionation upon transfer of N from mycorrhizal fungi, best explains variations in foliar δ 15 N with elevation.