内蒙古羊草草原呼吸的影响因素分析和区分

利用静态暗箱-气相色谱法在植物生长旺季测算了内蒙古锡林河流域羊草草原的土壤微生物呼吸、土壤呼吸和生态系统呼吸。地温和水分是植物生长旺季呼吸最重要的影响因素。地温在水分条件适宜的情况下可以解释CO₂通量的部分变化(R² = 0.376~0.655)。土壤水分含量也可以解释土壤呼吸和生态系统呼吸的部分变化(R² = 0.314~0.583)，但基本不能解释土壤微生物呼吸的变化(R² = 0.063)。即使在较高温度下，较低的土壤水分含量(≤ 5%) 也会显著的抑制CO₂排放。长期干旱后降雨使CO₂通量在高温下迅速增大。基于5 cm地温和0~10 cm土壤水分含量的双变量模型可以解释CO₂通量约70%的变化。观测期间，土壤呼吸占生态系统呼吸的比例介于47.3%~72.4%之间，平均为59.4%；根呼吸占土壤呼吸的比例介于11.7%~51.7%之间，平均为20.5%。由于植物体去除引起的土壤水分含量上升可能使我们对土壤呼吸占生态系统呼吸比例的估计略微偏高，根呼吸占土壤呼吸的比例略微偏低。

Analysis of Affecting Factors and Partitioning of Respiration in a Leymus chinensis Steppe in Inner Mongolia

Using a static opaque chamber method, the rates of soil microbial respiration, soil respiration, and ecosystem respiration were measured through continuous in-situ experiments in semiarid Leymus chinensis steppe in Xilin River Basin of Inner Mongolia, China. Soil temperature and moisture are the most important factors affecting CO₂ flux. Soil temperature was the main factor influencing respiration rates. Exponential models based on soil temperature can explain large percent of CO₂ efflux variations (R² = 0.375-0.655) excluding data of low soil water conditions. Soil moisture can also effectively explain some variations of soil and ecosystem respiration (R² = 0.314-0.583), but it can not explain much of variation of soil microbial respiration (R² = 0.063). Low soil water content (≤5%) inhibited CO₂ efflux though soil temperature was high. Rewetting the soil after a long drought resulted in substantial increases in CO₂ flux at high temperature. Bi-variable models based on soil temperature at 5 cm depth and soil water content at 0-10 cm depth can explain about 70% of variations of CO₂ effluxes. The contribution of soil respiration to ecosystem respiration averaged 59.4%, ranging from 47.3% to 72.4%; the contribution of root respiration to soil respiration averaged 20.5% , ranging from 11.7% to 51.7% . The contribution of soil to ecosystem respiration was a little overestimated and root to soil respiration underestimated because of increased soil water content that occurred as a result of plant removal.