石漠化地区不同种植年限李树土壤呼吸月动态变化研究

选取桂林恭城县国家可持续发展试验示范区石漠化治理过程中不同种植年限李树样地土壤为研究对象，对土壤呼吸进行以月为周期的监测，结果表明:（1）不同种植年限李树土壤呼吸速率的变化趋势随月份变化基本保持一致，呈现多峰形，而从季节尺度上看，随着春夏秋冬四季的交替，土壤呼吸速率逐渐下降；（2）李树种植年限在不同程度上对土壤呼吸速率均有影响，2 a，5 a和20 a的土壤呼吸速率年均值分别为48.56 mgC·（m2·h）-1、45.63 mgC·（m2·h）-1、41.64 mgC·（m2·h）-1，其中幼龄期（2 a）和盛果期（5 a）土壤呼吸速率较高，高的土壤呼吸速率反映了较快的有机代谢和物质循环，是为了满足植物在生长初期所需的碳源及养分，而20 a李树处于生长老龄期，其已维持了一个较稳定的地下生态系统，土壤呼吸作用降低；（3）在雨热同期（4-8月）时，土壤温度和土壤含水量之间呈极显著负相关关系（P<0.01），土壤温度和土壤呼吸速率之间呈极显著负相关关系（P<0.01），而土壤含水量与土壤呼吸速率呈极显著正相关关系（P<0.01），这主要是由于土壤呼吸在时间尺度上存在滞后效应。 

Study on the monthly dynamic change of soil respiration rate of plum trees with different planting ages in rocky desertification area

Soil respiration is the main process of soil carbon emission and an important factor affecting the dynamic change of soil carbon pool and atmospheric carbon pool. The amount of soil respiration determines the source and sink of soil carbon pool to a certain extent. It is of great significance to understand the mechanism of soil organic carbon accumulation, via studying the dynamic changes of soil respiration in fruit trees with different planting ages in karst areas. In this study, the soils samples of plum trees with different planting ages (i.e. 2 a, 5 a and 20 a, respectively) in the process of rocky desertification control in Gongcheng county, Guilin were selected as the research objects. The soil respiration rates were monitored on a monthly basis by using alkali absorption method from which the influencing factors were investigated and the data were analyzed by one-way analysis of variance (ANOVA) method. The results show that， (1) In a year time, the soil temperature and soil water content show a completely opposite seasonal trend, the change of soil respiration rate of the plum trees with different ages is basically consistent with the change of month, showing a multi-peak shape. On a seasonal scale, the soil respiration rate decreased gradually with the alternation of spring, summer, autumn and winter; (2) The planting ages of the plum trees have influence on soil respiration rate to different extents. The soil respiration rates of 2 a, 5 a and 20 a are 48.56 mgC·(m2·h)-1,45.63 mgC·(m2·h)-1 and 41.64 mgC·(m2·h)-1, respectively. This may be attributed to the higher soil respiration rate of the trees in their young stages (2 a) and full fruiting period (5 a), who require more carbon sources and nutrients for plant growth than the older ones（20 a）. The higher respiration rate reflects higher organic metabolism and material circulation. Compared the plum trees of 2 a and 5 a, the underground ecosystem of the 20 a tree is relatively stable; and the soil respiration rate of the latter slightly decreases； (3) In the same period of high soil heat and high rainfall from April to August, there is a significant negative correlation between soil temperature and soil water content (P < 0.01), a significant negative correlation between soil temperature and soil respiration rate (P < 0.01), and a significant positive correlation between soil water content and soil respiration rate (P < 0.01), which are mainly caused by the lag effect of soil respiration on time scale.