蓝田、长安人工林地土层含水量研究

根据蓝田孟村杨树林和梧桐林、长安县韦曲镇南杨树林地与西安市南郊麦地土壤含水量的测定，研究了0～600cm土壤含水量的变化和土壤干层特点与分布。实验表明，蓝田、长安地区在正常降雨年份人工林地土壤含水量从地表向地下呈现由高到低再到高的变化：12龄杨树林、14龄梧桐林、13龄和10龄杨树林地180～360cm深度范围内土壤含水量平均为9．5％、9．3％、9．0和9．2％，发育了明显的土壤干层：麦地土层含水量较梧桐林和杨树林地明显高，无土壤干化的显示；在丰水年蓝田、长安地区人工林土层含水量与正常降雨年份林地土壤含水量显著不同，12龄杨树林、14龄梧桐林、13龄和10龄杨树林地180～360cm深度范围内土壤含水量平均为22．5％、23．2％、22．5％和22．4％，土壤干层消失。这表明在降水量增加的条件下，土壤干层中的水分完全有可能恢复。土壤干层的发育会影响植物的正常生长，植被类型，植树造林和生态环境恢复，因此土壤干层水分恢复有重要意义。

Soil Moisture Content under Artificial Forests in Lantian and Chang'an Regions

Based on the determination of soil moisture under the artificial forests in Mengcun Village of the Lantian region, Weiqu of the Chang'an region and south suburbs of Xi'an, in this paper the change of soil moisture contents at depth of 0-6 m and the characteristics and distribution of dried layer of soil are studied. The experiments show that, in the years with normal precipitation, the soil moisture contents under the artificial forests change from high values to low ones and then to high ones again in the Lantian and Chang'an regions. The soil moisture contents at soil depth of 180-360 cm under the forests of 12-year-old Populus sp., 14-year-old phoenix trees, 13-year-old and 10-year-old Populus sp. are 9.5%, 9.3%, 9.0% and 9.2% respectively, and the dried layer of soil is formed. Soil moisture content in wheat fields is higher than that under the artificial forests, and the dried layer of soil does not be developed. In the rainy years, the soil moisture contents at depth of 180-350 cm under the artificial forests are different from that in the years with normal precipitation, they are 22.5%, 23.2%, 22.5% and 22.4% under the forests of 12-year-old Populus sp., 14-year-old phoenix trees, 13-year-old and 10-year-old Populus sp respectively, and the dried layer of soil disappears. The study result reveals that the dried layer of soil can be returned to normal in rainy years. Dried layer of soil can impact the normal growth of plants and the types of vegetation, so restoration of soil moisture content is significant for afforestation and ecological environment regeneration.