库布齐沙漠油蒿灌丛土壤呼吸速率时空变异特征研究

利用Li-840红外气体分析仪和Li-6400-09土壤呼吸气室组装而成的动态密闭土壤呼吸测定系统，于2006年生长季对内蒙古库布齐沙漠油蒿(Artemisia ordosica)生态系统2种不同类型土壤的土壤呼吸速率进行了野外测定，分析了日动态、季节动态及其对环境因子的响应，并阐述了油蒿灌丛空间异质性的特征.结果表明，油蒿灌丛的土壤呼吸速率日动态呈单峰曲线，在12:00左右有最大值.在适宜的水分和温度条件下，生长季里土壤呼吸速率在7～8月份出现最大值.土壤呼吸速率的季节动态与土壤含水量有显著的相关关系，表明水分是限制生长季干旱区灌丛土壤呼吸的最重要因子，分别可以解释油蒿冠幅下土壤和裸地的土壤呼吸速率2006年主要生长季节(5～9月)变化的75%和77%.油蒿灌丛土壤呼吸速率在空间尺度上存在着显著的异质性.油蒿冠幅覆盖下的土壤呼吸速率季节平均值为(155.58±15.20) mg·(m²·h)^-1，要显著地大于灌丛间裸地的数值(110.50±6.77) mg·(m²·h)^-1.2种不同类型土壤的土壤呼吸速率是由于根生物量的差异引起的，根生物量可以解释2006年生长季库布齐油蒿灌丛土壤呼吸速率空间异质性的43%.结果表明，在植被覆盖度异质性较大的灌丛生态系统中，要准确定量生态系统碳的释放时，必须充分考虑小尺度上土壤呼吸的空间异质性.

Temporal and Spatial Variations of Soil Respiration in an Artemisia ordosica Shrubland Ecosystem in Kubuqi Desert

Based on the dynamic measurements of soil respiration using a closed dynamic chamber and its related environmental factors in a desert shrubland ecosystem regularly during the growing season (May-September) of 2006, we studied the diurnal and seasonal variations of soil respiration of two different land cover soils and their responses to soil temperature, soil water content and biotic factors. The objective was to evaluate the temporal and spatial patterns of soil respiration and their responsible factors in Artemisia ordosica shrubland in Kubuqi Desert, Inner Mongolia, China. The diurnal variation of soil respiration showed an asymmetric single-peak pattern, with the peak value occurring around 12:00. Soil respiration fluctuated greatly during the growing season, reaching peak values in July-August. There was a significant linear relationship between soil respiration rate and soil water content at 10 cm depth. Most of the seasonal variation in soil respiration (75%-77%) could be explained by the variation in soil water content. The mean soil respiration under the shrub canopy was (155.58±15.20) mg·(m²·h)^-1, which was significantly higher than that for the bare ground between the shrubs (110.50±6.77) mg·(m²·h)^-1. The sensitivity of soil respiration to soil water content was also significantly higher for the soils under the canopy than for the bare ground soils. The spatial variation of soil respiration was caused mainly by the root biomass, which can be explained about 43% of heterogeneity. The results suggest that variation on a small time and space scales must be taken into consideration when estimating soil CO₂ efflux in the desert ecosystems.