Litter inputs exert greater influence over soil respiration and its temperature sensitivity than roots in a coniferous forest in north-south transition zone.

The changes in carbon inputs of litter and roots to forest soils caused by climate change will result in a serious cascade effect on soil respiration and its temperature sensitivity (Q10). To differentiate and quantify the effects of surface litter and living roots on soil respiration and Q10, and further explore the role of abiotic factors and microbial properties on soil respiration and Q10, a short-term (two years) detritus input and removal treatment experiment was conducted in a coniferous forest of central China. Soil temperature, soil moisture, C/N, microbial biomass and community composition were analyzed to explore the drive mechanisms of soil respiration and Q10 in response to carbon inputs. The results showed that litter addition increased soil respiration by 22 %, while litter or roots removal did not affect soil respiration, which might be ascribed to the "priming effects" mediated by fresh plant litter. We also found that litter addition increased Q10, while litter removal decreased Q10. Litter addition significantly enhanced the microbial biomass for any single functional group and altered soil microbial community composition. Structural equation model further proved that microbial biomass and community composition exerted stronger impacts on Q10 than do soil abiotic factors. Soil moisture, microbial biomass and community structure were main factors in predicting soil respiration. The study highlights the important role of litter inputs compared with living roots in carbon cycling in short-term and deepens our understanding on the complex relationships among soil respiration, soil micro-environment and microbial community composition.

Assessment of the bioactive compounds, antioxidant and antibacterial activities of Isodon rubescens as affected by drying methods.

The influence of natural drying (ND), hot-air drying (HD), vacuum drying (VD), infrared drying (ID) and freeze drying (FD) on bioactive compounds and bioactivities of Isodon rubescens (Hemsl.) was investigated in this study. The results showed that different drying methods resulted in the differences in bioactive compositions' content, antioxidant and antibacterial activities of extracts from I. rubescens. FD sample possessed the highest content of total phenolics, total flavonoids and several main phenolic compounds, as well as the stronger antioxidant and antibacterial activities, followed by ND, HD and VD, the lowest for ID samples. For this reason, freeze drying would seem to be more advisable for the drying I. rubescens, and future studies could focus on the quality evaluation and optimising various drying parameters.