云南干热河谷微地形改造对土壤水分动态的影响

通过定位观测和对比试验,对云南干热河谷典型地段改造后微地形土壤水分动态变化规律进行初步研究.结果表明:土壤水分的季节动态变化主要取决于降水量的大小及年内分配,通常分为土壤水分缓慢失墒期、土壤水分积累期、土壤水分缓慢消耗期和土壤水分稳定期等4个时期.雨季,水平沟、水平台的土壤水分季节动态变幅较自然坡面大.改造微地形等高水平上各层次的年平均含水率比自然坡面高,变异系数比自然坡面小,各微地形土壤含水量的变幅随土层深度增加而减小,均可分为土壤水分弱利用层、土壤水分利用层、补充调节层等3个作用层.雨季土壤水分的消退以表层最快,向下呈递减趋势.微地形改造后,雨后土壤水分的消退变缓,土壤水分在土壤中停留的时间增加,有利于植物的吸收利用.干热河谷地区微地形改造后明显改善了土壤水分环境.图3表4参16

Effect of reconstructed micro-slope on soil moisture dynamics in Yunnan dry-hot river valley

A preliminary research on the soil water dynamics of reconstructed micro-slope in typical slope in Yunnan dry-hot river valley was conducted by positioning observation and comparative tests. The results show that the seasonal dynamic changes of soil moisture were determined by the amount of rainfall and its distributions within the year. It was usually divided into four stages: evaporation stage before rainy season,wetting stage during rainy season,the stability stage in post-rainy season,and the stability stage in the winter. The soil moisture variety range of the contour trench and contour terrace in wetting stage during rainy stage was much greater than that of the natural slope. On the same high level, the yearly average soil moisture of all soil layers was much greater than that of the natural slope, and the coefficient of variation of soil moisture was smaller than that of the natural slope, the soil moisture variety range of micro-slope decreased with the increase in depth. The soil profile could be divided into three layers:active layer (c_v>0.30), less active (0.16c_v0.30) and stable layer (c_v0.16).Soil moisture lost very quickly on soil surface, it decreased with the increase in depth. Reconstructing micro-slope decreased the loss of soil moisture and increased the stagnation of moisture in soil, which was good for plants absorption of water. Reconstructing micro-slope obviously improved the soil humidity environment in dry-hot river valley.Ch,3 fig.4 tab.16 ref.]