小兴安岭典型温带森林土壤呼吸对强降雨的响应

森林土壤呼吸是全球碳循环的重要组成部分,其对降雨格局的变化如何响应,是当前全球变化研究中的热点问题。本研究以小兴安岭地区原始温带森林(云冷杉红松林)为研究对象,使用SF-3000土壤气体通量自动测量系统,对雨季不同时期4次强降雨前后的土壤呼吸速率、土壤呼吸的组分和相关环境因子进行了连续观测。结果表明:1)土壤温度和含水量协同影响土壤呼吸强度。降雨是影响甚至改变控制土壤呼吸(Rs)的关键环境因子,强降雨使土壤含水量激增,并对土壤温度也有不同程度的影响。雨季初期强降雨对Rs的扰动作用相对较小,雨季中期强降雨可抑制Rs,在雨季结束后强降雨可促进Rs。2)在雨季不同时期的强降雨均不同程度的影响了土壤异养呼吸(Rh)与土壤呼吸的比例(Rh/Rs),相对于土壤自养呼吸(Ra),短时极强降雨对Rh的抑制作用更强。3)加入水分修正系数c的Rs与T5、W5指数关系模型可更好的表征土壤含水量和土壤温度对土壤呼吸的影响,不同雨季时期的强降雨均对土壤的温度敏感系数(Q10)有着显著的影响。强降雨使得土壤对水分的敏感性降低,处于雨季不同时期的土壤水分敏感性表现为:在雨季的开始和结束后,土壤呼吸的水分敏感性较高,而雨季中期的水分敏感性较低。 

Effect of strongrainfalls on soil respiration in a typical temperate forest in Lesser Xing' an Mountains,northeast China

Forest soil respiration is an important component of ecosystem carbon cycle. Under the context of global climate change, extreme climate events present a high﹣rate tendency. How the change affects soil respiration in the forest ecosystem has attracted more and more attention. In order to investigate the response of soil respiration to strong rainfalls during different periods of the wet season, we used SF﹣3000 automated soil flux system to monitor different components of soil respiration in a typical temperate forest (spruce﹣fir﹣Korean pine forest) in Lesser Xing' an Mountains, northeast China. Environmental factors were also measured simultaneously. The results showed that, 1) soil respiration (Rs) was influenced by soil temperature and soil water content. The strong rainfalls altered the determining factors that control Rs. Soil water content was stimulated greatly by strong rainfalls. During the early period of wet season, Rs was merely disturbed by strong rainfalls, whereas it decreased Rs during the wet season and increased Rs after the wet season. 2) The influences of strong rainfalls on heterotrophic respiration/soil respiration (Rh/Rs) varied during different periods of the wet season. Compared to autotrophic respiration (Ra), strong rainfalls greatly inhibited Rh. 3) The relationship between Rs and soil temperature at 5 cm depth ( T5 ) as well as soil water content at 5 cm depth ( W5 ) could be better explained by an exponential equation which contains soil moisture parameter c. Strong rainfalls had varying effects on temperature sensitivities of Rs ( Q10 ) during different periods of the wet season. The soil moisture sensitivity of Rs was decreased after rainfall. The moisture sensitivities ( c) during different periods of the wet season were characterized as follow:wet season < early wet season < after the wet season.