克氏针茅(Stipa krylovii)草原土壤呼吸及其影响因子

Daily and seasonal dynamics of soil respiration and their environmental controlling factors in Stipa krylovii steppe

基于LI6400-09便携式光合作用测量系统的土壤呼吸观测系统对内蒙古克氏针茅(Stipakrylovii)草原2005年5月至9月的土壤呼吸作用的测定结果,研究了克氏针茅草原土壤呼吸速率的日、生长季动态及其控制因子。结果表明,在生长季节,克氏针茅草原土壤呼吸速率的日季动态均呈单峰型变化;日最大值和最小值分别出现在10:00～13:00和凌晨4:00左右;生长季日均最大值(0.14mgCO2m-2s-1)出现在6月份,日均最小值(0.03mgCO2m-2s-1)出现在8月份。在日尺度上,随着生长期的变化,控制土壤呼吸作用的环境因子有所不同;在生长初期和末期土壤呼吸速率的限制因子主要为总辐射,而在生长中期,控制因子则为气温和土壤含水量。在整个生长季的尺度上,极显著影响土壤呼吸作用的环境因子则为土壤含水量(0～10cm、10～20cm、20～30cm)、总辐射和气温。约有72%的土壤呼吸作用生长季变异是由表层土壤含水量和总辐射共同决定的,其中0～10cm土壤含水量是影响克氏针茅草原土壤呼吸作用在生长季节变化的主导环境因子,可以单独解释土壤呼吸作用变异的51%。

Soil respiration was measured by using a Li6400-09 soil respiration chamber from May to September 2005 in Stipa krylovii steppe,Inner Mongolia.Environmental variables including air temperature,total radiation,soil temperature and soil water content were also measured during the same period.Our results showed that daily variations of soil respiration could be characterized by a mono-peak pattern.The highest soil respiration rates occurred in between 10：00am and 13：00 pm,and the lowest at about 4：00 am.Seasonal changes of soil respiration can also be described by a mono-peak pattern with the highest（0.14mgCO2m-2s-1）in June and the lowest（0.03mgCO2m-2s-1）in August.While air temperature,soil water content,and total radiation determined both daily and seasonal changes of soil respiration,we found a significant correlation in the seasonal changes that can be modeled as R=0.011W1-0.005W2＋6.117×10-5D＋0.038（R2=0.72 P〈0.001）,where R is the soil respiration rate,D is the radiation,and W1,W2 are soil water contents in the depth of 0-10,10-20 respectively.The soil water content at the 0-10 cm depth was found a dominating factor that can account for 51% of the seasonal variation of soil respiration.