黄土丘陵区不同林龄乔灌林地土壤水分及持水性能研究

Study on Characters of Soil Water Content and Water Conservation of Arbor and Shrub Lands With Different Forest Ages in the Loess Hilly-gullied Region

土壤水分是黄土丘陵区生态恢复过程中的主要制约因素,对该区典型流域不同林龄主要乔灌林地土壤容重、水分特征和持水能力的分析结果表明,表层土壤容重表现出天然灌木林<乔木林<人工灌木林<果园,且容重随林龄的增加而减小,即20a>25a>30a。下层土壤容重与表层变化规律相似。土壤总孔隙度与土壤容重和非活性孔度变化规律相反,与土壤活性孔度和土壤孔隙比变化基本一致。0-50cm土层土壤含水量变化顺序为果园>刺槐>柠条>狼牙刺,50-500cm土层则是刺槐林地最小,灌木林地在50-200cm土层的变动幅度较大,200-350cm土层柠条小于狼牙刺,350-500cm土层狼牙刺则小于柠条,主要受人工林种植密度和人为干扰措施影响。苹果园经过隔坡梯田整地措施,其林下0-500cm土层土壤水分含量最高。该区提倡"灌木先行"的植被恢复措施是必要的。表层土壤总持水量随林龄增加而增加,土壤总持水量变化顺序为天然灌木林地>乔木林地>人工灌木林地,有效持水量却表现出与总持水量相反的变化趋势,容重越低,土壤有效持水性越强。20-40cm土层及40-60cm土层的持水特性表现出与表层土壤相似的规律。

Soil water content is the main restrict factor in the ecological restoration process of the loess region.Studied on the characters of soil water content and water conservation of the main arbor and shrub lands with different forest ages in the typical watershed,the results showed that the order of the bulk density of the upper layer was natural shrub lands〈arbor lands〈artificial shrub lands〈orchards and bulk density increased with the increased forest ages,it showed that 20 a〉25 a〉30 a.Bulk density of the lower soil layer had the similar law.The total porosity had the opposite law with bulk density and non-capillary porosity while had the similar law with capillary porosity and ratio of porosity.The order of soil water content of 0-50 cm soil layer was orchards〉 Robinia pseudoacacia 〉Caragana Korshinskii〉 Sophora davidii and the soil water content of Robinia pseudoacacia was the lowest in the 50-500 cm soil depth.Shrub lands changed heavily in 50-200 cm depth,while the soil water content of Sophora davidii was more than Caragana Korshinskii from 200-350 cm depth but less than that from 350-500 cm depth.The main reason was grow density and artificial disturb measures.Orchards had the highest soil water content because of terrace tillage measures.So advocate shrub first was necessary in this region.The total water conservation of upper soil layer increased with forest ages and the change order was natural shrub lands〉arbor lands〉artificial shrub but the available water conservation had the opposite change trends.While the lower bulk density was,the higher available water conservation was and the 20-60 cm soil layer had the similar laws with the upper soil layer.