晋西黄土区不同水文年土壤水分特征及其主要影响因子分析

  目的  晋西黄土区生态环境脆弱，土壤水分是制约植被生长的重要因子。为深入了解该区域土壤水分年际变化，明确制约该区域土壤储水量的关键因子，探讨晋西黄土区不同植被类型在生长季节内土壤含水量的变化。  方法  以定位观测法为主，对人工刺槐Robinia pseudoacacia林、天然三角槭Acer buergerianum林和野艾蒿Artemisia lavandu-laefolia草地生长季(5?10月)内0~400 cm土壤含水量进行监测；在此基础上，根据含水量标准差对土壤进行活跃层划分，并通过生长季前后储水量的对比探究年际土壤储水量盈亏状况；测定了典型样地的土壤性质，并结合地形、不同水文年旱涝特征对土壤储水量的影响因子进行冗余分析。  结果  ①人工刺槐林、天然三角槭林和野艾蒿草地平均土壤含水量分别为8.36%~9.63%、10.01%~13.19%和15.43%~19.17%，野艾蒿草地表层土壤含水量显著高于人工刺槐林和天然三角槭林(P＜0.05)。②天然三角槭林土壤水分活跃层最深可达180 cm，人工刺槐林和野艾蒿草地土壤水分活跃层较浅；中等湿润年土壤水分活跃层最深，严重干旱年土壤水分活跃层次之，平水年土壤水分活跃层最浅。③严重干旱年，人工刺槐林、天然三角槭林和野艾蒿草地土壤水分亏缺土层深度分别为100~300、0~200和0~100 cm；平水年土壤水分的输入和输出达到平衡；中等湿润年0~200 cm土层水分得到不同程度补给，而200~400 cm土层的水分补给量接近于0。④不同深度土层土壤储水量受不同环境因子影响，其中植被类型和土壤容重是0~100 cm土层水分的主导因素，100~200 cm土层水分主要受容重和坡向控制，而不同水文年旱涝程度、土壤黏粒和粉粒含量是200~400 cm土层水分的主导因素。  结论  干旱水文年土壤水分亏缺严重，平水年及湿润年亏缺现象有所缓解，植被类型对土壤储水量影响最大。今后黄土高原地区的造林，不仅要考虑树种的耐旱能力，更应充分考虑地形、土质及生长季降水的分配情况带来的影响。图5表5参33

Characteristics of soil moisture and its main influencing factors in different hydrological years in western Shanxi loess region

  Objective  This study aims to investigate soil moisture variation of different vegetation types during the growing season in the loess region of western Shanxi Province, where the eco-environment is fragile and soil moisture is an important factor restricting the vegetation restoration.  Method  The soil moisture content of 0?400 cm soil layer in the growing season (May to October) in artificial forestland (Robinia pseudoacacia), natural forestland (Acer buergerianum) and grassland (Artemisia lavandulaefolia) was monitored by location observation method. On this basis, the soil active layer was divided according to the standard deviation of moisture content, and the annual soil water storage profit and loss were explored by comparing the water storage before and after the growing season. The soil properties of typical sample plots were measured, and the redundancy analysis of the factors affecting soil water storage capacity was carried out in combination with topography and characteristics of drought and flood in different hydrological years.  Result  (1) The soil moisture of the artificial forestland, the natural forestland, and the grassland ranged from 8.36% to 9.63%, 10.01% to 3.19% and 15.43% to 19.17%, respectively, and the surface soil moisture content of the grassland was significantly higher than that of the forestlands (P＜0.05). (2) The depth of soil water active layer in the natural forestland reached 180 cm, deeper than that of the artificial forestland and the grassland. The soil water active layer was the deepest in moderate humid years, shallower in severe drought years, and the shallowest in normal years. (3) In severe drought years, the depth of soil water deficit of the three types was 100?300, 0?200 and 0?100 cm, respectively. The input and output of soil moisture could keep balance in normal years. In moderate humid years, the moisture content in 0?200 cm soil layer was replenished to different degrees, while the moisture content in 200?400 cm soil layer was close to 0. (4) The soil moisture storage of different soil layers was affected by different environmental factors among which vegetation types and bulk density were the dominant factors of soil moisture in 0?100 cm soil layer, and the water content of 100?200 cm soil layer was mainly controlled by bulk density and slope aspect, while the degree of drought and flood in different hydrological years, the content of soil clay and silt were the dominant factors of soil moisture in 200?400 cm soil layer.  Conclusion  The soil water deficit is severe in drought years, and is alleviated in normal or wet years. Vegetation types have the greatest impact on soil moisture storage. In the future restoration of vegetation in the Loess Plateau, we should not only consider the drought tolerance of tree species, but also the impact of topography, soil properties, and precipitation distribution during the growing season. Ch, 5 fig. 5 tab. 33 ref.]