%0 Journal Article
%T Carbon control on terrestrial ecosystem function across contrasting site productivities: the carbon connection revisited
%A Gregory S. Newman
%A John M. Stark
%A Nicholas C. Dove
%A Stephen C. Hart
%J Ecology - Wiley Online Library
%D 2019
%R https://doi.org/10.1002/ecy.2695
%X Understanding how altered soil organic carbon (SOC) availability affects microbial communities and their function is imperative in predicting impacts of global change on soil carbon (C) storage and ecosystem function. However, the response of soil microbial communities and their function to depleted C availability in situ is unclear. We evaluated the role of soil C inputs in controlling microbial biomass, community composition, physiology, and function by (1) experimentally excluding plant C inputs in situ for 9 yr in four temperate forest ecosystems along a productivity gradient in Oregon, USA; and (2) integrating these findings with published data from similar Cİ\exclusion studies into a global metaİ\analysis. Excluding plant C inputs for 9 yr resulted in a 13% decrease in SOC across the four Oregon sites and an overall shift in the microbial community composition, with a 45% decrease in the fungal : bacterial ratio and a 13% increase in Gramİ\positive : Gramİ\negative bacterial ratio. Although gross N mineralization decreased under C exclusion, decreases in gross N immobilization were greater, resulting in increased net N mineralization rates in all but the lowestİ\productivity site. Microbial biomass showed a variable response to C exclusion that was method dependent; however, we detected a 29% decrease in Cİ\use efficiency across the sites, with greater declines occurring in lessİ\productive sites. Although extracellular enzyme activity increased with C exclusion, C exclusion resulted in a 31% decrease in microbial respiration across all sites. Our metaİ\analyses of published data with similar Cİ\exclusion treatments were largely consistent with our experimental results, showing decreased SOC, fungal : bacterial ratios, and microbial respiration, and increased Gramİ\positive : Gramİ\negative bacterial ratio following exclusion of C inputs to soil. Effect sizes of SOC and respiration correlated negatively with the duration of C exclusion; however, there were immediate effects of C exclusion on microbial community composition and biomass that were unaltered by duration of treatment. Our fieldİ\based experimental results and analyses demonstrate unequivocally the dominant control of C availability on soil microbial biomass, community composition, and function, and provide additional insight into the mechanisms for these effects in forest ecosystems. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding
%U https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecy.2695