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Modelling the demand for new nitrogen fixation by terrestrial ecosystems

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Title: Modelling the demand for new nitrogen fixation by terrestrial ecosystems
Authors: Xu-Ri
Prentice, IC
Item Type: Journal Article
Abstract: Continual input of reactive nitrogen (N) is required to support the natural turnover of N in terrestrial ecosystems. This “N demand” can be satisfied in various ways, including biological N fixation (BNF) (the dominant pathway under natural conditions), lightning-induced abiotic N fixation, N uptake from sedimentary substrates, and N deposition from natural and anthropogenic sources. We estimated the global new N fixation demand (NNF), i.e. the total new N input required to sustain net primary production (NPP) in nonagricultural terrestrial ecosystems regardless of its origin, using a N-enabled global dynamic vegetation model (DyNLPJ). DyN-LPJ does not explicitly simulate BNF; rather, it estimates total NNF using a mass balance criterion and assumes that this demand is met from one source or another. The model was run in steady state and then in transient mode driven by recent changes in CO2 concentration and climate. A range of values for key stoichiometric parameters was considered, based on recently published analyses. Modelled NPP and C : N ratios of litter and soil organic matter were consistent with independent estimates. Modelled geographic patterns of ecosystem NNF were similar to other analyses, but actual estimated values exceeded recent estimates of global BNF. The results were sensitive to a few key parameters: the fraction of litter carbon respired to CO2 during decomposition and plant-type-specific C : N ratios of litter and soil. The modelled annual NNF increased by about 15 % during the course of the transient run, mainly due to increasing CO2 concentration. The model did not overestimate recent terrestrial carbon uptake, suggesting that the increase in NNF demand has so far been met. Rising CO2 is further increasing the NNF demand, while the future capacity of N sources to support this is unknown.
Issue Date: 12-Apr-2017
Date of Acceptance: 27-Feb-2017
URI: http://hdl.handle.net/10044/1/54664
DOI: https://dx.doi.org/10.5194/bg-14-2003-2017
ISSN: 1726-4170
Publisher: Copernicus Publications
Start Page: 2003
End Page: 2017
Journal / Book Title: Biogeosciences
Volume: 14
Issue: 7
Copyright Statement: © Author(s) 2017. CC Attribution 3.0 License.
Sponsor/Funder: AXA Research Fund
Funder's Grant Number: AXA Chair Programme in Biosphere and Climate Impacts
Keywords: Science & Technology
Life Sciences & Biomedicine
Physical Sciences
Ecology
Geosciences, Multidisciplinary
Environmental Sciences & Ecology
Geology
NET PRIMARY PRODUCTIVITY
CARBON SEQUESTRATION
GLOBAL VEGETATION
ELEVATED CO2
FOREST PRODUCTIVITY
CLIMATE-CHANGE
N-2 FIXATION
SOIL
PATTERNS
DEPOSITION
04 Earth Sciences
05 Environmental Sciences
06 Biological Sciences
Meteorology & Atmospheric Sciences
Publication Status: Published
Appears in Collections:Department of Life Sciences
Faculty of Natural Sciences