黄土高原3个不同降水量地点油松林地水分生产力与土壤干燥化效应模拟

Simulation of Water-limiting Biomass Productivity of Chinese Pine Plantations and the Soil Desiccation Effect in 3 Sites with Different Annual Precipitation on Loess Plateau

应用WinEPIC模型模拟1957—2001年期间黄土高原半湿润区洛川、半干旱区延安和半干旱偏旱区榆林油松林地水分生产力演变规律和深层土壤干燥化效应。模拟结果表明:洛川、延安和榆林油松林地逐年生物量模拟值在9～17年生达到最大值(平均值分别为4.29,3.62和2.73t.hm-2),之后随降水量年际波动呈现出明显的波动性降低趋势;1～22年生期间油松林地平均年耗水量高于同期年降水量,导致林地0～10m土层土壤强烈干燥化,逐月土壤有效含水量波动性降低,洛川14～20年生、延安9～20年生和榆林6～19年生期间是油松林地土壤强烈干燥化阶段,年均土壤干燥化速度分别为176,111和69mm,此后油松林地土壤有效含水量在0～150mm范围内的较低水平上随降水量变化而波动;洛川、延安和榆林油松林地0～10m土层土壤湿度剖面分布变化剧烈,土壤湿度逐年降低,土壤干层逐年加厚,分别从15,10,6年生开始土壤干层厚度超过3m,在19年生时均已超过10m,20年生以后2～10m土层土壤湿度保持相对稳定的干燥化状态;洛川、延安和榆林油松林地水分生产力和土壤干燥化效应区域差异显著,林地土壤水分可持续利用年限约30年。

WinEPIC model was used to simulate water productivity and deep soil desiccation of Chinese pine（Pinus tabulaeformis）plantations of Luochuan,a semi-humid region,Yanan,a semi-arid region,and Yulin,a semi-arid prone drought region of the loess plateau in China during 1957-2001.The results showed as the following：in Luochuan,Yanan and Yulin,simulated annual biomass of the 1-45-year-old Chinese pine plantations averaged 4.29,3.62 and 2.73 t.hm-2,respectively.Productivity peaked when plantations were 9-17-year-old and then tended to decrease obviously in a pattern that followed the fluctuation of annual rainfall.In 1-22-year-old Chinese pine plantations,average annual water consumptions were higher than annual rainfalls,which resulted in soil drying in 0-10 m depth.The faster soil desiccation occurred in the period of 14-20-year-old plantations of Luochuan,9-20-year-old plantations of Yanan and 6-19-year-old plantations of Yulin.Soil desiccation rates in Luochuan,Yanan and Yulin were 176,111 and 69 mm per year,respectively.After that the monthly available water in 0-10 m soil layers fluctuated at a low level in a range of 0-150 mm as annual rainfalls varied in the three sites.The 0-10 m soil humidity profiles sharply varied,with annual declining the humidity and thickening dry soil layers.Dry soil layers exceeded 3 m thick in 15-year-old plantation of Luochuan,10-year-old plantation of Yanan,and 3-year-old plantation of Yulin.In 19-year-old plantations of the three sites,dry soil layers already exceeded 10 m thick,and in 20-45-year-old plantations the dry soil layers were relatively stable of low humidity in 2-10 m soil layers.There were significant differences in water productivities and soil desiccation effects in the plantations between the three sites,and the soil water could be sustainably used by the Chinese pine plantations on the three sites for about 30 years.