Strong pulse effects of precipitation events on soil microbial respiration in temperate forests

Precipitation is a critical factor triggering soil biogeochemical processes in arid and semi-arid regions. In this study, we selected soils from two temperate forests-a mature natural forest and a degraded secondary forest in a semi-arid region. We investigated the pulse effects of simulated precipitation (to reach 55% soil water-holding capacity) on the soil microbial respiration rate (R-s). We performed high-intensity measurements (at 5-min intervals for 48 h) to determine the maximum value of R-s (RS-max), the time to reach RS-max ( RS-max), and the duration of the pulse effect (from the start to the end of 1/2R(s-max)). The responses of R-s to simulated precipitation were rapid and strong. Rs-max was significantly higher in degraded secondary forest (18.69 mu g C g soil(-1) h(-1)) than in mature natural forest (7.94 mu g C g soil(-1) h(-1)). In contrast, the duration of the pulse effect and RS-max, were significantly lower in degraded secondary forest than in mature natural forest Furthermore, the accumulative microbial respiration per gram of soil (AR(S-soc)) did not differ significantly between degraded secondary forest and mature natural forest, but the accumulative microbial respiration per gram of soil organic C (A(Rs-soc)) was significantly higher in degraded secondary forest than in mature natural forest. Soil microbial biomass, soil nutrient, and litter nitrogen content were strongly correlated with the duration of the pulse effect and TRs-max Soil physical structure, pH, and litter nitrogen content were strongly correlated with RS-max and AR(S-soc), Our results indicate that the responses of soil microbial respiration to simulated precipitation are rapid and strong and that microbial respiration rate per gram C can be used to precisely determine the precipitation pulse of different soil samples as well as the effects of changing precipitation patterns on soil C content under various scenarios of global climate change. (C) 2016 Elsevier B.V. All rights reserved.