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The role of stoichiometric flexibility in modelling forest ecosystem responses to nitrogen fertilization
Author(s) -
Meyerholt Johannes,
Zaehle Sönke
Publication year - 2015
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.13547
Subject(s) - ecosystem , primary production , nitrogen , productivity , flexibility (engineering) , environmental science , atmospheric sciences , vegetation (pathology) , carbon cycle , human fertilization , forest ecology , nitrogen cycle , ecology , agronomy , chemistry , biology , mathematics , physics , statistics , medicine , macroeconomics , organic chemistry , pathology , economics
Summary The response of the forest carbon (C) balance to changes in nitrogen (N) deposition is uncertain, partly owing to diverging representations of N cycle processes in dynamic global vegetation models ( DGVM s). Here, we examined how different assumptions about the degree of flexibility of the ecosystem's C : N ratios contribute to this uncertainty, and which of these assumptions best correspond to the available data. We applied these assumptions within the framework of a DGVM and compared the results to responses in net primary productivity ( NPP ), leaf N concentration, and ecosystem N partitioning, observed at 22 forest N fertilization experiments. Employing flexible ecosystem pool C : N ratios generally resulted in the most convincing model–data agreement with respect to production and foliar N responses. An intermediate degree of stoichiometric flexibility in vegetation, where wood C : N ratio changes were decoupled from leaf and root C : N ratio changes, led to consistent simulation of production and N cycle responses to N addition. Assuming fixed C : N ratios or scaling leaf N concentration changes to other tissues, commonly assumed by DGVM s, was not supported by reported data. Between the tested assumptions, the simulated changes in ecosystem C storage relative to changes in C assimilation varied by up to 20%.