Soil Respiration and Its Influencing Factors at Grazing and Fenced Typical Leymus chinensis Steppe,Nei Monggol
放牧与围栏羊草草原土壤呼吸作用及其影响因子

Based on two-year soil respiration observing data at fenced and grazing typical Leymus chinensis steppe, Nei Monggol by the enclosed chamber method, soil respiration and its relationships with various affecting factors were analyzed. The major results include: (1) The diurnal and seasonal dynamics of soil respiration are similar at fenced and grazing typical Leymus chinensis steppe, but soil respiration rate is larger at the fenced plots than that at the grazing plots, and their values were 219.18 mg x (m2 x h)(-1) and 111.27 mg x (m2 x h)(-1), respectively. The reason of soil respiration rate increasing in the fenced plots might be the increases of biomass in the belowground and soil water content. (2) Among the influencing factors on soil respiration, grazing decreases the effects of soil water content and relative humidity and increases the effect of photosynthetic rate, and has no significant effects on other factors. (3) At the fenced plots, the correlation of soil respiration rate with soil water content is largest, followed by photosynthetic rate, air temperature, relative humidity, air CO2 concentration, intercellular CO2 concentration, stomatal conductance and the lowest being photosynthetically active radiation. Soil water content and air temperature are the main environmental factors, and photosynthetic rate is the critical biotic factor. The affecting factors on soil respiration are the same at the fenced and grazing plots, however the importance of those influencing factors is changed quantitatively.