降雨对不同密度栓皮栎林土壤温湿度及水分运移的影响1）

以黄河小浪底库区3种密度栓皮栎林为研究对象，运用稳定同位素技术，结合大气、土壤温湿度及土壤水分氘同位素（δD）值，探讨不同季节降雨对土壤剖面温度、水分动态及运移的影响。结果表明，降雨前后高密度林分土壤温度均最高，且下层土壤具保温效果。土壤湿度随密度增大而增加，且低密度林分下层湿度大，而中高密度林分表层湿度大。雨前土壤水分δD值与枯落物δD值变化趋势相同，均随密度增大而减小。低密度林分，降雨在枯落物及土壤表层滞留时间较短，均可较快入渗到深层土壤，随后涵养在上层水分以活塞流形式下渗。且前期降水较多时，混合水可侧向流动补给壤中流。中高密度林分，在前期土壤湿度较大的雨季和旱季初期，降雨也可较快入渗到深层，除高密度林分在前期降雨较多的雨季下渗到中层。而前期降雨较少时，降雨在中高密度林分的枯落物及表层土壤滞留时间较长。表明土壤湿度低时，中密度林分土壤可较好的蓄积水分，而高密度林分在湿度低或高时均能较好的调控土壤水分。此外，在前期降水充足和高强度降雨后，降雨在低中密度林分均可通过优先流形式快速入渗，补给深层土壤。泉水和地下水δD值没有明显改变，可为干旱季节植被生长提供重要水源。

Effects of Seasonal Rainfall on Soil Temperature,Moisture and Water Movement in Different Density Stands of Quercus variabilis

By using stable isotope techniques , three density stands of Quercus variabilis in the Yellow River Xiaolangdi reservoir were chosen to investigate the δD of soil water , temperature and moisture of both air and soil in order to study the effect of seasonal rainfall on soil temperature , moisture and water movement .The soil temperature of high density stand was the highest before and after all the four rainfall events , and the subsoil had insulation effect .The soil moisture increased with the increase of stand density , and the subsoil moisture were higher in the low density stand , whereas the upper layer of soil were higher in the middle and high density stand .The variation trend of soil water δD and litter δD were the same before the rainfall, which decreased with the increase of stand density .In the low density stand, the residence time of rainfall were shorter in the litter and the soil surface , so they could quickly infiltrate into the deeper soil layer , then the conserved water in upper layer slowly infiltrated to the deep soil through the piston flow .Furthermore, the mixed water could form in-terflow through the lateral flow after previous plentiful rainfall events .In the medium and high density stands , in the middle and late of rainy season and the early dry season when previous soil moisture was higher , the rainfall could also rapidly in-filtrated to the deeper soil .An exception was that the water infiltrated to the middle soil layer in the high density stand in the middle of rainy season with high soil moisture .However , in the prior low soil moisture condition , the residence time of rainfall was shorter in the litter and the soil surface , which indicated that the medium density stand could better store soil water in the low humidity conditions , and the high density stand could regulate the soil moisture in the low or high environ-ment.After prior plentiful or high intensity rainfall , the preferential flows could rapidly infiltrated and supplied to deeper soil water in the low and medium density stand .The δD of spring and ground water did not change obviously , two water sources could supply water for plant in the dry season .