西北半干旱区林地土壤水分动态研究

Study on the Dynamic Situation of Soil Moisture on Forest Land of Semi-arid Area in North-western China

研究结果表明,影响半干旱区林地土壤水分的主要因素为降水量及树种适宜性。土壤有效水日益降低,土层不断干化,其程度与林木生长发育状况呈负相关。林分对土壤水的消耗量大于自然补偿量,灌木林适应性较乔木强,生育状况较乔木好。对土壤水的消耗和干化程度亦较乔木严重。各土层含水量随降水而波动,波动幅变随深度增加而变小,林地土壤含水高峰在9～4月,低峰在7～8月。西北半干旱区造林应选择抗旱灌木,发展聚流灌溉,降低造林密度,除个别树种外,成林密度在200株(丛)/亩以下。

Main factors which influence soil moisture of forest land of semiarid area are precipitation and suitability of trees;Quantity of effective soil water decreases and soil layer becomes drier and drier increasingly The degree of variation has negative relatio with the situation of forest growing Soil water exhausted by trees is more than natural precipitation Shrubs are more suitable and grow better than arbors and also exhaust much more soil water, so the degree of dryness of dryness of the soil under shrubs is more serious than that under arbors the quantity of water in different soil layers varies with the rainfall and range of variation decreases with the increasing of depth; the peak quantity of soil water on forest land is from September to April and the lowest is in July through August.From above conclusions the author suggests that drought-resistant shrubs should be selected for plantation,forestation irrigated by surface runoff be developed and the plant density be lowered Except for some special trees,the forest density should be under 200 tufts per mu.