降雨量改变对常绿阔叶林干旱和湿润季节土壤呼吸的影响

通过野外原位试验,研究降雨量改变对华西雨屏区常绿阔叶林干旱和湿润季节土壤呼吸速率的影响。采用LI-8100土壤碳通量分析系统(LI-COR Inc.,USA)测定干旱和湿润季节对照(CK)、增雨10%(LA)、增雨5%(TA)、减雨10%(LR)、减雨20%(MR)、减雨50%(HR)6个处理水平的土壤呼吸速率,并通过回归方程分析温度和湿度与土壤呼吸速率间的关系。结果表明:湿润季节土壤呼吸速率高于干旱季节,HR处理对干旱季节土壤呼吸速率影响较大,而LA处理对湿润季节土壤呼吸速率的影响较大。TA和LR处理使土壤呼吸的温度敏感性增加,而HR、LA和MR处理使土壤呼吸的温度敏感性降低,干旱季节Q10值高于湿润季节。各处理湿润季节土壤微生物量碳氮含量显著高于干旱季节,HR、MR和LA处理减少土壤微生物生物量碳、氮的含量,而TA和LR处理增加土壤微生物生物量碳、氮的含量。与湿润季节相比,干旱季节土壤水分对土壤呼吸速率的影响较大;而与土壤温度相比,土壤水分对土壤呼吸速率的影响较小。在降雨量改变的背景下,华西雨屏区常绿阔叶林无论是干旱还是湿润季节,适当增雨和减雨都会促进土壤呼吸速率,而较高量的增雨和减雨会抑制土壤呼吸速率。

Effects of precipitation variations on soil respiration in an evergreen broad-leaved forest during dry and wet seasons

Our objective was to explore the effects of precipitation variations on soil respiration and its temperature sensitivity in an evergreen broad-leaved forest during the dry and wet seasons in western China affected by monsoons. Six treatments: CK (a control), LA (low water addition), TA (trace water addition), LR (low water reduction), MR (medium water reduction), and HR (high water reduction) were established in an evergreen broad-leaved forest. The LI-8100 (LI-COR Inc., USA) Automated Soil CO₂ Flux System was used to measure soil respiration rates during the dry (December 2013 to February 2014) and wet (July to September 2014) seasons of the evergreen broad-leaved forest. The results were as follows: the soil respiration rate was higher in the wet than dry season. HR treatment had a greater impact on the soil respiration rate during the dry season, similarly to LA in the wet season. LR and TA treatments increased the temperature sensitivity of soil respiration, whereas LA, MR, and HR decreased the temperature sensitivity of soil respiration, and the Q₁₀ value was higher in the wet than in the dry season. HR, MR, and LA treatments decreased the carbon and nitrogen contents in soil microbial biomass, and LR and TA increased the contents of soil microbial biomass carbon and nitrogen. The contents of carbon and nitrogen in microbial biomass in different treatments were significantly higher in the wet than in the dry season. Compared with the wet season, in the dry season, soil moisture had a greater impact on the soil respiration rate; and compared with soil temperature, soil moisture had little effect on the soil respiration rate. Considering that the amount of precipitation varies, appropriate water addition and reduction could promote the soil respiration rate, whereas higher amounts of water addition and reduction could inhibit the soil respiration rate during the dry and wet seasons, respectively, of the evergreen broad-leaved forest in western China.