干旱区不同种植年限苜蓿人工草地土壤CO2排放的主要影响因素

采用静态箱-气象色谱法对干旱区不同种植年限苜蓿人工草地土壤系统、土壤-植被系统的CO2排放通量进行了测定，并对土壤 CO2排放通量的主要影响因素，包括土壤碳氮质量分数、土壤温度、气温、土壤水分体积分数、生物量进行了测定分析，从而得到了苜蓿生长季内CO2排放通量规律及影响土壤CO2排放的主要因素。结果表明：观测期内各个年限土壤-植被系统与土壤系统的CO2排放趋势基本一致，总体表现为4a〉5a〉8a〉3a〉1a，表现出“夏季高秋季低”的季节变化规律，具有明显的季节变化动态，各样地CO2通量在7月中旬达到最高排放通量；土壤CO2排放通量与0~20 cm土层内土壤有机碳质量分数、活性有机碳质量分数、土壤C：N及土壤全N质量分数都具有正相关关系，并且都达到了显著水平；土壤CO2排放通量与5 cm土壤温度和大气温度都有正相关关系，并且显著水平很高（P＜0.001）；土壤CO2排放通量与0~10 cm土壤水分体积分数之间没有显著的相关性（P〉0.05）；土壤CO2排放通量与地上部分生物量的大小有直接的正相关关系，并且CO2排放通量与地上生物量具有相同的变化趋势。

Main factors controlling soil C02 efflux from alfalfa fields of different standing ages in an arid region

In order to study its dynamic characteristics and the main influencing factors, CO2 emission fluxes both from soil and from soil-vegetation system were measured in alfalfa stands of various stand ages by using static chamber-GC technique in the meanwhile, the environmental factors such as the contents of soil carbon and nitrogen, soil temperature, air temperature, soil water content and aboveground biomass were also determined in the field. The same age pattern of CO2 emission flux was observed in soil-vegetation system and in soil system, that was： 4 a〉5 a〉8 a〉3 a〉1 a. The value of CO2 emission flux in summer was higher than that of in autumn, suggested that the seasonality was apparent. The maximum CO2 emission flux in each sample plot appeared in mid-July. The CO2 emission flux was positively correlated with soil organic carbon content, soil active organic carbon, soil C/N Ratio and soil total nitrogen of the depth 0-20 cm, and all tests reached statistical significance. The CO2 emission flux was also positively correlated with 0-5cm soil temperature and air temperature （P〈0.001）. No significant correlation between the CO2 emission flux and the 0-10 cm soil water content was observed was observed. The CO2 emission flux was positively correlated with the aboveground biomass, to be exact, they showed the same trend.