荒漠草原灌丛转变过程土壤呼吸动态变化及其影响因素研究

探析荒漠草原向灌丛转变过程土壤呼吸动态及其影响因素，对确定干旱半干旱生态系统碳“源”/“汇”状态具有重要意义。本研究以宁夏东部荒漠草原-灌丛镶嵌体为研究对象，选取荒漠草地、草地边缘、灌丛边缘、灌丛地为研究样地，开展各样地微生境(植丛与空斑)下土壤呼吸(Rs)及相关土壤性质研究，结果表明：随着荒漠草原向灌丛地转变，土壤呼吸日动态与季节动态呈上升趋势，季节动态在7月达到峰值(P<0.05)，灌丛地显著高出荒漠草地42.4%；土壤温度为转变过程土壤呼吸日动态的主要影响因子，温度和水分共同影响(R²介于0.44~0.80)土壤呼吸季节动态；回归分析和主成分分析表明，土壤呼吸与全碳、全氮、微生物生物量碳、生物量氮、土壤有机碳呈显著负相关(P<0.01)，与硝态氮呈显著正相关(P<0.05)。综上，近30年灌丛转变过程促使土壤二氧化碳通量增加，加速荒漠草原有机碳养分消耗。

Dynamics and Influencing Factors of Soil Respiration in the Transition Process of Desert Grassland to Shrubland

The analysis of soil respiration dynamics and its influencing factors in the desert grassland-shrubland transition is important to determine the carbon "source"/"sink" status of arid and semi-arid ecosystems. In this study,desert grassland,grassland edge,shrubland edge,and shrubland were selected as research sites in a typical mosaic land of desert grassland and shrubland in eastern Ningxia. Soil respiration (Rs),soil moisture and temperature dynamics,and other soil properties were investigated and analyzed in micro-habitats (vegetation patch and bare interspace) of each site. The results showed that with the transition process from desert grassland to shrubland,the daily and seasonal Rs gradually increased,with a peak of seasonal Rs in July,while Rs in shrubland was significantly 42.4% higher than that in desert grassland (P<0.05). Soil temperature was the main factor of the daily Rs dynamics during the transition,and temperature and water content jointly influenced (0.44 < R² < 0.80) the seasonal Rs dynamics. Furthermore,regression and principal component analysis showed that soil respiration flux was significantly negatively correlated with total carbon,total nitrogen,microbial biomass carbon,microbial biomass nitrogen,and soil organic carbon (P<0.01),and significantly positively correlated with NO^-₃-N (P<0.05). The results indicated that the process of shrub introduction in the past 30 years has increased soil carbon dioxide flux emission,and has been accelerating the combined release of inorganic carbon and nitrogen.