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Elevated CO2 and warming cause interactive effects on soil carbon and shifts in carbon use by bacteria

Carrillo, Yolima, Dijkstra, Feike, LeCain, Dan, Blumenthal, Dana, Pendall, Elise
Ecology letters 2018 v.21 no.11 pp. 1639-1648
arid lands, bacteria, carbon, carbon dioxide, carbon dioxide enrichment, carbon sinks, climate change, fungi, grasslands, isotope labeling, prediction, soil
Accurate predictions of soil C feedbacks to climate change depend on an improved understanding of responses of soil C pools and C use by soil microbial groups. We assessed soil and microbial C in a 7‐year manipulation of CO₂ and warming in a semi‐arid grassland. Continuous field isotopic labelling under elevated CO₂ further allowed us to study the dynamics of the existing C (Old C) in soil and microbes as affected by warming. Warming reduced soil C under elevated CO₂ but had no impact under ambient CO₂. Loss of soil C under warming and elevated CO₂ was attributed to increased proportional loss of Old C. Warming also reduced the proportion of Old C in microbes, specifically the bacteria, but not the fungi. These findings highlight that warming impacts are C pool and microbial taxa dependent and demonstrate interactive effects of warming and atmospheric CO₂ on soil C.