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PUBLISHED ONLINE: 23 DECEMBER 2012 | DOI: http://www.nature.com/doifinder/10.1038/nclimate1781
Web End =10.1038/NCLIMATE1781
Biogeochemical plantsoil microbe feedback in response to climate warming in peatlands
Luca Bragazza1,2,3*, Julien Parisod1,2, Alexandre Buttler1,2,4 and Richard D. Bardgett5
Peatlands act as global sinks of atmospheric carbon (C) through the accumulation of organic matter1, primarily made up of decay-resistant litter of peat mosses2. However, climate warming has been shown to promote vascular plant growth in peatlands, especially ericaceous shrubs3. A change in vegetation cover is in turn expected to modify aboveground/below-ground interactions4, but the biogeochemical mechanisms involved remain unknown. Here, by selecting peatlands at different altitudes to simulate a natural gradient of soil temperature, we show that the expansion of ericaceous shrubs with warming is associated with an increase of polyphenol content in both plant litter and pore water. In turn, this retards the release of nitrogen (N) from decomposing litter, increases the amount of dissolved organic N and reduces N immobilization by soil microbes. A decrease of soil water content with increasing temperature promotes the growth of fungi, which feeds back positively on ericaceous shrubs by facilitating the symbiotic acquisition of dissolved organic N. We also observed a higher release of labile C from vascular plant roots at higher soil temperatures, which promotes the microbial investment in C-degrading enzymes. Our data suggest that climate-induced changes in plant cover can reduce the productivity of peat mosses and potentially prime the decomposition of organic matter by affecting the stoichiometry of soil enzymatic activity.
Northern peatlands have played an important role in global C cycling during the Holocene epoch owing to their capacity to store atmospheric carbon dioxide (CO2) and to emit methane (CH4).
At present, peatlands are estimated to contain about 300400 Pg C, corresponding to about 30% of the global soil C pool, despite covering only 3% of the land surface1. Peatlands act as long-term sinks of atmospheric CO2 through the accumulation of peat, that is, partially decomposed plant litter. Hydrological conditions that favour soil waterlogging, combined with the dominance of vegetation that produces decay-resistant litter, hamper microbial litter decomposition so that a net accumulation of organic matter takes place. As a result, any environmental change that removes a constraint on organic matter decomposition, including alteration of feedback between above-ground and...