Sheffer, E, Batterman, SA, Levin, SA et al. (1 more author) (2015) Biome-scale nitrogen fixation strategies selected by climatic constraints on nitrogen cycle. Nature Plants, 1. 15182. ISSN 2055-026X
Abstract
Dinitrogen fixation by plants (in symbiosis with root bacteria) is a major source of new nitrogen for land ecosystems 1. A long-standing puzzle 2 is that trees capable of nitrogen fixation are abundant in nitrogen-rich tropical forests, but absent or restricted to early successional stages in nitrogen-poor extra-tropical forests. This biome-scale pattern presents an evolutionary paradox 3, given that the physiological cost 4 of nitrogen fixation predicts the opposite pattern: fixers should be out-competed by non-fixers in nitrogen-rich conditions, but competitively superior in nitrogen-poor soils. Here we evaluate whether this paradox can be explained by the existence of different fixation strategies in tropical versus extra-tropical trees: facultative fixers (capable of downregulating fixation 5,6 by sanctioning mutualistic bacteria 7) are common in the tropics, whereas obligate fixers (less able to downregulate fixation) dominate at higher latitudes. Using a game-theoretic approach, we assess the ecological and evolutionary conditions under which these fixation strategies emerge, and examine their dependence on climate-driven differences in the nitrogen cycle. We show that in the tropics, transient soil nitrogen deficits following disturbance and rapid tree growth favour a facultative strategy and the coexistence of fixers and non-fixers. In contrast, sustained nitrogen deficits following disturbance in extra-tropical forests favour an obligate fixation strategy, and cause fixers to be excluded in late successional stages. We conclude that biome-scale differences in the abundance of nitrogen fixers can be explained by the interaction between individual plant strategies and climatic constraints on the nitrogen cycle over evolutionary time.
Metadata
Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2015, The Authors. This is an author produced version of a paper published in Nature Plants. Uploaded in accordance with the publisher's self-archiving policy. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Geography (Leeds) > Ecology & Global Change (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 16 Dec 2015 11:27 |
Last Modified: | 12 Jun 2016 12:00 |
Published Version: | http://dx.doi.org/10.1038/nplants.2015.182 |
Status: | Published |
Publisher: | Nature Publishing Group |
Identification Number: | https://doi.org/10.1038/nplants.2015.182 |