典型岩溶洼地土壤水分的空间分布及影响因素

在桂西北典型岩溶洼地的旱季和雨季,用地统计学结合GIS方法研究了洼地表层(0—16cm)土壤水分的空间分布特征及其影响因素。结果表明:土壤含水量受前期降雨量的影响,且旱季土壤水分对降雨量的反应较雨季敏感。土壤水分均呈中等变异且变异系数随着平均含水量的增加而减少。土壤水分的半方差参数显示土壤水分空间变异及其主导因素随旱、雨季而不同。此外,不同取样区域及取样时段内土壤含水量高低差别明显,分布格局及空间变异程度各异,这主要与当地环境和人为因素的综合影响有关。旱、雨季土壤水分均与前期降雨导致的土壤平均含水量变化呈相反趋势,且不同土地利用方式下的土壤含水量不同。土壤含水量还与土壤有机碳含量呈显著正相关,此外,地势及裸岩率也是造成洼地土壤水分变异及其分布差异的重要因素。下一步应根据旱季和雨季土壤水分分布及影响因素的差异,在岩溶洼地采取有针对性地土壤水资源利用及其水分管理策略。

Research on spatial distribution and influencing factor of soil moisture in typical depression area of karst region

The characterization of the spatial variability, distribution and influencing factor of soil moisture is of paramount importance in many ecological processes and operational applications, especially in the karst area of China. In this study, soil moisture was measured with a portable T DR for a layer depth of 0-16 cm in a karst depression area of southwest China during the dry and rainy seasons of 2005, and the spatial variability, distribution and influencing factors of soil moisture content were investigated by using the geo-statistics and GIS method. The results indicated that the surface soil moisture content was influenced by the antecedent rainfall (the rainfall accumulation 10 days before the sampling time) and it was more sensitive to the antecedent rainfall in dry season than that in rainy season. The mean soil moisture content varied from 21.67% to 28.79% during the dry and rainy seasons. The soil moisture content showed middle variability, and the CV values decreased with the increasing mean soil moisture content either in dry or rainy season. The parameters of semi-variogram theoretical models of soil moisture content indicated that the spatial variability and its dominant influencing factor of soil moisture content both changed with the dry and rainy season. Similar results were also obtained from the pattern of soil moisture content, which generated by the ordinary kriging interpolation. The soil moisture content, its distribution and variability were always different at different sampling time and region. But, a similar pattern of the soil moisture content was observed on the whole in the two seasons, with drier zones always becoming drier and vice versa. Also, the distribution of soil moisture content showed mosaic pattern in dry season, compared with the strip or band pattern in rainy season, which were caused by the combined influence of environmental factors and human activities. What's more, the variability of soil moisture content by CV values decreased with the increasing mean soil moisture content due to the antecedent rainfall either in dry or rainy season. And the soil moisture content was different in different land use types. The abandoned field and orchard field always had relatively higher soil moisture content either in dry or rainy season, followed by the rehabilitated field and gazing field, and the cultivated field had relative lower soil moisture content. Furthermore, a significant positive correlation was found between the soil moisture content and the soil organic carbon. Altitude and bare-rock ratio were also important factors influencing the soil moisture content in the depression area. Therefore, rational strategies of soil water resource usage and management should be made according to the different spatial distributions and influencing factors of soil moisture content in dry and rainy season in the depression area of karst region.