水热因子对退化草原羊草恢复演替群落土壤呼吸的影响

 对内蒙古锡林郭勒白音锡勒牧场退化恢复羊草（Leymus chinensis）草原生态系统土壤呼吸作用的主要影响因子分析表明，环境因子对土壤呼吸作用的影响程度依次表现为：土壤水分>温度；水分对土壤呼吸作用的影响可分成3段，即<7.5%、7.5%～18.4%和>18.4%。当0～10cm土壤含水量＜7.5%时，土壤温度是土壤呼吸作用的主导控制因子，土壤呼吸作用与5cm土壤温度呈幂函数关系；而当0～10cm土壤含水量＞7.5%时，土壤呼吸作用受土壤水分和土壤温度的共同作用。研究还表明：在植物生长季内，当土壤水分接近羊草草原土壤萎蔫系数6.0%时所测得土壤呼吸作用为植被在干旱胁迫下的土壤呼吸作用，而当土壤水分大于羊草草原土壤萎蔫系数6.0%时，土壤呼吸作用的增加主要是由于植物生长及其引起的根系活动和微生物数量、组成及其活性共同影响的，进而可以解释不同水分条件下土壤及植物根系在土壤呼吸作用中的不同贡献，为建立土壤呼吸作用模型及正确地理解陆地碳收支及其固碳潜力提供依据。

EFFECTS OF HEAT AND WATER FACTORS ON SOIL RESPIRATION OF RESTORING LEYMUS CHINENSIS STEPPE IN DEGRADED LAND

The carbon cycle of restoring steppe in degraded land is one of the important parts of the global terrestrial carbon cycle. The study of soil respiration in restoring steppe plays a very important role in accurately evaluating the carbon budget of restoring steppe and its function in the global carbon budget. As we know, temperature and soil water content are two important environmental factors in understanding the soil respiration process in terrestrial ecosystems. To quantify their allocation and the relationship between soil respiration and temperature and soil moisture, we conducted field experiments to investigate soil respiration from June to September 2001. The effects of heat and water factors on soil respiration of restoring Leymus chinensis steppe in degraded land was studied at Baiyinxile pasture (43°55′N, 116°31′E, with an altitude of about 1 200 m) in Inner Mongolia. This region, un-grazed in June, has a typical temperate and semi-arid climate and the community structure of the vegetation consisted mainly of two species, Leymus chinensis and Stipa grandis; the soil type was classified as chestnut. Daily variation was investigated by taking measurements once an hour from 6∶00 to 19∶00 every ten days during the whole growing season using an enclosed chamber method. The results indicated that environmental factors affecting soil respiration ranged as soil water content > temperature, and the soil water content in the upper 10 cm of the soil was of real significance in all of the environmental factors. We analyzed the relationship between daily average soil respiration rate (6∶00-19∶00) and daily average soil water content (%) using the partial correlation analysis of the SPSS and the coefficients showed that soil water content of 7.5% and 18.4% were two thresholds affecting the soil respiration rate. Soil water content could be divided into three levels: <7.5%, 7.5%-18.4% and >18.4% based on their effects on soil respiration. When soil water content was less than 7.5%, soil temperature was the dominant factor of soil respiration. Soil respiration (Rs) could be expressed as an exponential relationship with soil temperature (t) at the depth of 5 cm and their relationship was Rs=4.07t1.098 (w<7.5%, R2=0.49, n=80, p7.5%, R2=0.81, n=69,