Contrasting effects of low-severity fire on stemflow production between coexisting pine and oak trees.

As climate change intensifies, fires events are predicted to increase in forest ecosystems. Fire alters the ecosystem structure and consequently, the hydrological cycle. However, little is known about the impacts of forest fire on stemflow. A field experiment was conducted to evaluate the short-term response of stemflow production to low-severity fire in a coniferous and broadleaved mixed forest. Results demonstrated low-severity fire changed stemflow yield and had insignificant effect on the correlation between stemflow efficiency and rainfall or plant morphological variables. In unburned site Quercus acutissima and Pinus massoniana and in burned site Q. acutissima and P. massoniana, stemflow percentage averaged 3.86, 0.37, 1.20, and 0.47 %, whereas funneling ratio averaged 38.8, 4.2, 11.4, and 5.1, respectively. Fire substantially decreased the stemflow percentage and funneling ratio of Q. acutissima (P < 0.05) and slightly enhanced P. massoniana (P > 0.05). The responses of stemflow production to fire differed significantly between oak and pine trees. Fire made Q. acutissima become less effective in funneling rain to the forest ground, which is attributed to that the scaly bark was burned to highly furrowed bark that delivers less water to tree base. Burned P. massoniana was more productive in draining stemflow relative to unburned trees and is attributed to the bark which was still flaky regardless of. Additionally, the higher canopy openness allows more rain to funnel to the trunk. Stemflow efficiency was reduced in response to fire and limited the transfer of water and nutrients from canopy to soil and can reduce the competitiveness of Q. acutissima after fire disturbance.

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.