小型红壤坡面土壤含水率时空特性研究

Spatial-temporal Characteristics of Soil Moisture on Small Red Soil Slope

为了探索小型红壤坡面土壤含水率的时空分布规律,在桂林市雁山镇平均坡度14°、坡长12 m、宽度5 m的红壤坡面布设14个观测点,分别对0~60 cm土深的6个土层进行了为期1 a的土壤含水率观测,并用统计学方法及时间稳定性概念进行了分析。结果表明,随着土壤深度的增加,各土层平均土壤含水率总体逐步上升,各土层含水率变异系数的均值总体逐步减小,各土层的含水率更加均匀;随着平均含水率的增加,各土层含水率的波动幅度先增大后减小;不同坡位的土壤含水率在干湿2季表现出不同的特点,湿季0~10 cm土层的含水率为下坡位>中坡位>上坡位,其余土层均表现为上坡位>中坡位>下坡位,干季0~10 cm土层含水率沿坡位的变化特点与湿季相同,而其余土层未表现出相同的规律。在时间特性上,红壤坡面土壤含水率与降雨量及降雨频次的关系密切,气温和空气湿度也是影响含水率的重要因素;随着土层的加深,土壤含水率的时间稳定性增强;除0~10、40~50 cm土层外,全序列所得时稳最强点对土壤平均含水率的代表性优于其他序列,干季序列所得各点的时间稳定性指数与全序列更为接近,同时干季序列所得时稳最强点对土壤平均含水率的代表性也明显优于湿季序列;植被根系对含水率的时间稳定性有一定影响,40~50 cm土层植被根系最多,使得全序列所得时稳最强点对所在土层平均含水率的代表性较差。

In order to explore the spatial-temporal distribution characteristics of soil mois^re content in small red soil slope, 14 observation points were set on a slope with the average gradients of 14~, lengths of 12 m, width of 5 m. Soil moisture was observed and analyzed using the statistical method and the concept of temporal stability. The results indicated that with the increasing of soil depth, the average soil moisture had a trend of rising, however, the variation coefficient of average moisture each soil layer gradually reduced which made soil moisture more uniform. Along with the increase of the average soil moisture, the fluctuations of each soil layer increased at the beginning and then decreased. The soil moisture of different slope positions in the wet and dry seasons exhibited different characteristics. In wet season, soil moisture in 0-10 cm soil layer was that lower slope〉middle slope〉up- per slope and the remaining layers were all that upper slope〉middle slope〉lower slope. While in dry season, soil moisture in 0-10 cm layer was same as that in wet season. On temporal characteristic, soil moisture was closely related to rainfall and rainfall frequency, in addition, air temperature and air humidity were also key factors to af- fect soil moisture. With the deepening of the soil layer, time stability of soil moisture enhanced. Except 0-10 cm and 40-50 cm layer, the most time stable points, which were calculated by full time sequence, were more repre- sentative than others. The indexes of temporal stability （1TS） in dry season were closer to that in full time se- quence and at the same time, the most time stable point to the average soil moisture representation in the dry sea- son sequence was significantly better than that in the wet season sequence. Vegetation root system had an impact on the stability of the moisture of the time which was dense in 50 cm layer that made the most time stable point to the average soil moisture representation relatively poor.