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Carbon cost of plant nitrogen acquisition: A mechanistic, globally applicable model of plant nitrogen uptake, retranslocation, and fixation
Author(s) -
Fisher J. B.,
Sitch S.,
Malhi Y.,
Fisher R. A.,
Huntingford C.,
Tan S.Y.
Publication year - 2010
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2009gb003621
Subject(s) - nitrogen , human fertilization , nitrogen fixation , nutrient , biosphere , biomass (ecology) , environmental science , carbon fibers , agronomy , atmospheric sciences , replicate , botany , chemistry , soil science , biology , ecology , mathematics , physics , organic chemistry , composite number , statistics , algorithm
Nitrogen (N) generally limits plant growth and controls biosphere responses to climate change. We introduce a new mathematical model of plant N acquisition, called Fixation and Uptake of Nitrogen (FUN), based on active and passive soil N uptake, leaf N retranslocation, and biological N fixation. This model is unified under the theoretical framework of carbon (C) cost economics, or resource optimization. FUN specifies C allocated to N acquisition as well as remaining C for growth, or N‐limitation to growth. We test the model with data from a wide range of sites (observed versus predicted N uptake r 2 is 0.89, and RMSE is 0.003 kg N m −2 ·yr −1 ). Four model tests are performed: (1) fixers versus nonfixers under primary succession; (2) response to N fertilization; (3) response to CO 2 fertilization; and (4) changes in vegetation C from potential soil N trajectories for five DGVMs (HYLAND, LPJ, ORCHIDEE, SDGVM, and TRIFFID) under four IPCC scenarios. Nonfixers surpass the productivity of fixers after ∼150–180 years in this scenario. FUN replicates the N uptake response in the experimental N fertilization from a modeled N fertilization. However, FUN cannot replicate the N uptake response in the experimental CO 2 fertilization from a modeled CO 2 fertilization; nonetheless, the correct response is obtained when differences in root biomass are included. Finally, N‐limitation decreases biomass by 50 Pg C on average globally for the DGVMs. We propose this model as being suitable for inclusion in the new generation of Earth system models that aim to describe the global N cycle.