放牧与围栏羊草草原土壤呼吸作用及其影响因子

基于静态箱式法连续2a的测定资料,比较分析了内蒙古典型羊草草原放牧与围栏样地土壤呼吸作用及其与各影响因子的关系.结果表明:①围栏内外土壤呼吸作用日、季动态差异不大,但围栏样地土壤呼吸速率明显高于放牧样地,其平均值分别是219.18 mg·(m²·h)^-1和111.27 mg·(m²·h)^-1,围栏样地土壤呼吸作用的升高可能与地下生物量增加和土壤水分改善有关;②对影响土壤呼吸作用的因子分析表明,放牧使土壤水分和相对湿度的影响明显降低,而对气温、大气CO₂浓度和光合有效辐射的影响并不大,且放牧使羊草净光合速率的影响明显增加,而对气孔导度和胞间CO₂浓度影响不大;③围栏样地土壤呼吸作用与各影响因子的相关性从大到小依次为土壤水分、净光合速率、气温、相对湿度、大气CO₂浓度、胞间CO₂浓度、气孔导度和光合有效辐射,其中土壤水分和气温是影响土壤呼吸作用的主要环境因子,净光合速率是主要的生物因子.尽管放牧改变了土壤呼吸速率,但土壤呼吸作用各影响因子的排列顺序基本上没有改变,只是发生了量的变化.

Soil Respiration and Its Influencing Factors at Grazing and Fenced Typical Leymus chinensis Steppe,Nei Monggol

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.