Warming persistently stimulates respiration from an arable soil over a decade, regardless of reduced summer precipitation

Abstract

Climate change factors alter soil microbial biomass and respiration, which represent two key parameters of carbon (C) cycling in soils. While these interrelations are increasingly well described for soils in natural ecosystems, long-term studies conducted in temperate agricultural ecosystems do rarely exist. Here we used the ‘Hohenheim Climate Change Experiment (HoCC)’ to describe the response of microbial biomass and respiration to interacting effects of climate change factors. We were interested in whether effects would be season specific, and if ultimately, climate change factors would affect the total soil organic carbon (SOC) content in the arable soil. The HoCC experiment is an agroecosystem where soils were permanently warmed for one decade, and summer precipitation amount and frequency were reduced. We found that soil respiration was not affected by reduced summer precipitation, but strongly increased by warming. This increase was not season specific and persisted over the years. Further, warming continuously enhanced labile C availability, while microbial biomass did not differ between warmed and ambient temperature soils. Therefore, soil respiration stimulated by warming was independent of microbial biomass, and accordingly, we found an increase of the metabolic quotient. Despite the warming induced increase in soil respiration, no indications for a loss in SOC content of the arable soil was detected. These results suggest that in an arable soil with overall low SOC content, the persisting stimulation of respiration due to warming is driven by an agroecosystem specific labile C pool dynamic.