Microbial Mediation of Different Fractions of the Carbon-Cycle Feedbacks to Long-Term Climate Change

Abstract

Investigating the effect of long-term elevated atmospheric CO2 (eCO2) and warming on soil organic carbon (SOC) and the microbial mechanisms underlying the change of SOC is pivotal to predict the SOC stability in farming soils in response to climate change. Using open-top chambers to mimic the rises of atmospheric CO2 concentration up to 700 ppm (eCO2) and temperature of 2℃ above surroundings (warming), a six-year experiment was carried out with maize grown in four major farming soils, i.e. Phaeozem, Kastanizem, Fluvisol and Acrisol, to examine SOC fractions and bacterial community diversity. We found that six-year of eCO2 did not increase SOC concentration in any soil, but changed the SOC distribution among fractions. Long-term eCO2 and warming decreased the fine particulate organic carbon (fPOC) concentration but increased the mineral-associated organic carbon (MOC) concentration in Phaeozem and Kastanizem. Meanwhile, fPOC and MOC showed opposite trends under long-term climate change. The PCoA showed the warming altered bacterial community composition in Kastanizem and Acrisol. The results indicated that long-term climate change might not alter SOC stock but affect the bacterial community to accelerate the C turnover rate among different SOC pools that regardless of soil type.

Keywords: Long-term climate change, SOC fractions, Bacterial community composition, fPOC, MOC