N2-fixing tropical legume evolution: a contributor to enhanced weathering through the Cenozoic?
Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK [email protected]
School of Geography and Priestley International Centre for Climate, University of Leeds, Leeds LS2 9JT, UK.
Smithsonian Tropical Research Institute, Balboa, Ancon, Panama.
Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA.
Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
- Published Article
Proceedings of The Royal Society B Biological Sciences
The Royal Society
- Publication Date
Aug 16, 2017
Fossil and phylogenetic evidence indicates legume-rich modern tropical forests replaced Late Cretaceous palm-dominated tropical forests across four continents during the early Cenozoic (58-42 Ma). Tropical legume trees can transform ecosystems via their ability to fix dinitrogen (N2) and higher leaf N compared with non-legumes (35-65%), but it is unclear how their evolutionary rise contributed to silicate weathering, the long-term sink for atmospheric carbon dioxide (CO2). Here we hypothesize that the increasing abundance of N2-fixing legumes in tropical forests amplified silicate weathering rates by increased input of fixed nitrogen (N) to terrestrial ecosystems via interrelated mechanisms including increasing microbial respiration and soil acidification, and stimulating forest net primary productivity. We suggest the high CO2 early Cenozoic atmosphere further amplified legume weathering. Evolution of legumes with high weathering rates was probably driven by their high demand for phosphorus and micronutrients required for N2-fixation and nodule formation.
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The corresponding record at NLM can be accessed at https://www.ncbi.nlm.nih.gov/pubmed/28814651