准噶尔盆地两种荒漠群落土壤呼吸速率对人工降水的响应

通过野外定位观测准噶尔盆地荒漠植物群落(假木贼群落和盐穗木群落)在不同人工模拟降水强度下的土壤呼吸、土壤温度和湿度动态,探讨了荒漠群落土壤呼吸速率对降水后土壤增湿的响应.结果发现两种荒漠植物群落的土壤呼吸速率均出现了模拟降水后10min减小、随后逐渐增加、达到最大值后再次衰减的现象.降水处理的土壤呼吸速率最大值出现滞后于对照处理,且呼吸速率最大值及最大值后的递减速率普遍高于对照.降水后土壤呼吸速率变化受温度和土壤湿度共同影响,降水后10min土壤呼吸速率的减小与土壤湿度最大值同步,呼吸速率最大值出现时间与地表温度一致,在降水后180～300min.2类群落3种降水处理间的土壤呼吸速率在模拟降水后(0～450min时段)均未达到显著差异.假木贼群落以5mm降水处理的平均土壤呼吸速率最大,盐穗木群落则以2.5mm 处理最大.土壤呼吸速率对模拟降水的响应受降水量、降水前土壤湿润状况、土壤质地等多种因素影响.

Responses of soil respiration to artificial rainfall in two desert communities in Junngar Basin

In the arid and semiarid regions, discrete precipitation pulses are important triggers for biological activity. Soil biogeochemical processes in these water-limited systems are closely linked to episodic rainfall events, and the relationship between microbial activity and the amount and timing of rainfall has important implications for carbon balance of the whole-system. In this paper the influence of rainfall on soil respiration was determined in field of natural deserts with Anabasis aphylla and Halostachys caspica in the western Junngar Basin, Xinjiang. The amount of rainfall was controlled at 5 mm and 2.5 mm with a control treatment (0 mm precipitation), respectively. A pattern of soil respiration rate after rainfall, that is, a decline followed by a subsequent increase which was followed by another decline was observed. Maximum soil respiration occurred at the 5 mm and 2.5 mm treatments lagged behind that for control treatment. The maximum rate and the declining respiration rate thereafter were higher at the 5 mm and 2.5 mm treatments than that at the 0 mm treatment. Soil respiration was influenced by temperature and soil moisture following rainfall. It was shown that the first decline of soil respiration coincide with wettest soil moisture at the 10th minute after rainfall, and the largest soil respiration occurred simultaneously with soil surface temperature at the 180th or 300th minute. The difference of soil respiration in three rainfall treatments was not significant for the two communities during 0-450 minutes following rainfall simulation. The average rate of soil respiration at the 5 mm treatment was largest in the Anabasis aphylla community, while that at the 2.5 mm treatment was largest in the Halostachys caspica community. The response of soil respiration to rainfall simulation is dependent on rainfall size, antecedent soil moisture condition and soil texture and so on.