喀斯特地区土壤水分随降雨的动态变化研究——以贵阳市花溪区为例

Study on the dynamic change of soil moisture in karst area:A case of Huaxi district in Guiyang City

土壤水分是喀斯特地区植被恢复和生态环境建设的关键性限制因素。选取贵阳市花溪区为研究对象，基于2013年和2015年土壤水分定位监测数据，分析了研究区土壤水分的动态变化规律。结果表明：（1）土壤剖面水分的垂直变化具有明显层次；基于标准差和变异系数两个指标，采用聚类分析将2013年和2015年研究区土壤水分垂直变化层次分为活跃层（0～10cm），次活跃层（10～30cm）和相对稳定层（30～100cm）。（2）土壤水分的动态变化主要受降雨与蒸散作用的综合影响；10～30cm土层由于没有与外部环境直接接触受其影响相对降低，同时降雨的入渗与蒸散作用的减弱，使该层次土壤水分分布范围广、停留时间长，较能准确地反映其受降雨和蒸发的影响。（3）土壤水分的动态变化具有明显季节性；2013年和2015年春季（3-5月）和冬季（12-2月）为土壤水分的补给期，夏季（6-8月）和秋季（9-11月）为土壤水分的消耗期。

Huaxi district is located in the south of Guiyang City in Guizhou Province. It bestrides an area be- tween E106°27′-106°52′and N26°11r-26°34′, with a land area of 958.56 km2 and a population size of 4.9× 10^5. Soils are predominated by yellow and lime soils. The area is characterized by humid subtropical mon- soonal plateau climate, with the average annual temperature of 14. 9 ℃, the average annual rainfall of 1,178.3 mm, annual sunshine time of about 1,278 h, the average annual relative humidity of 78% and frost- free period of about 270 d. 94% of the landmass is karst landform, represented by low hills and lowlands. In order to explore the dynamic change of soil moisture with rainfall, we used Excel 9.003, SPSS software and the cluster analysis method to analyze the relationship Between the soil moisture and precipitation in the stud- y area. Results show that, （1） The vertical change in soil moisture content is significant at depth in 2013 and 2015, which can be divided into active layer （0-10 cm）, sub-active layer （10-30 cm） and relatively stable layer （30-100 cm）; （2） The dynamic change of soil moisture is mainly affected by rainfall and evaportran- spiration, which can be accurately reflected by the above relationship at the 10-30 cm deep soil layer; （3） The dynamic change of soil moisture has an obvious character of seasonal fluctuation, of which the spring and winter can be identified as the soil water recharge period, while the soil moisture consumption takes place in summer and autumn. The main reasons for the change of soil moisture in karst area are the result of the interaction of rainfall and soil evaporation, plant transpiration and vegetation consumption.