黄土高原半干旱区不同密度山地苹果园水分生产力模拟

Water productivity of apple orchards with different planting densities in semi-arid mountain ous regions of Loess Plateau,Northwest China:A simulation study

采用修订WinEPIC模型，模拟研究了陕西延安和甘肃静宁1965--2009年7种不同密度处理山地苹果园产量和深层土壤水分效应．结果表明：各密度处理4～45年生果园产量均呈现初期快速增加，达到最大值后又逐年波动性降低趋势；果园密度越高，初期产量增加越快，后期产量随降水量年际波动越剧烈．各密度处理果园遭受干旱胁迫规律基本一致，即生长前期无干旱胁迫，随种植年限延长干旱胁迫波动性加剧，生长后期干旱胁迫日数与年降水量波动趋势相反．生长初期，各密度处理果园0～15m土层逐年土壤有效含水量均呈现波动性强烈降低趋势，延安和静宁分别在17～22年生和13～20年生之后土壤有效含水量维持在0～600mm的较低水平．各密度处理果园0—15nl土层土壤湿度剖面分布特征相似：均经历了土壤湿度逐年降低和土壤干层逐年加厚的干燥化过程，土壤稳定干层深度可达12ITI．基于0～15m土壤有效水分含量和4～45年果园产量模拟结果确定，延安和静宁果园适宜种植密度分别为650～800和550～700株．hm-2．

By adopting the revised WinEPIC model, a simulation study was conducted to investigate the responses of the apple yield and deeper soil moisture content to 7 planting densities in the apple orchards in Yan＇ an of Shaanxi and in Jingning of Gansu in 1965-2009. Under the 7 planting den- sities, the annual yields of the 4-45 years apple orchards increased rapidly at early growth stage, and then decreased with fluctuation after reached the maximum. The higher the planting density, the higher the annual yield was obtained at early growth stage, but the yield at late growth stage fluctuated dramatically with annual precipitation. The orchards with different planting densities had the similar soil water stress process, i. e. , no water stress at early growth stage, and water stress oc- curred and fluctuated dramatically with increasing planting years. The days of water stress at late growth stage changed oppositely to annual precipitation. At early growth stage, the soil available moisture content in 0-15 m layer under the 7 planting densities all decreased rapidly with strong fluctuation, ranged in a low level of 0-600 mm after 17-22 years in Yan＇ an and after 13-20 years in Jingning. The soil moisture content in 0-15 m layer changed similarly under different planting densities, i.e. , decreased gradually with the deepening of soil desiccation, and the stable depth of drying layer could reach 12 m. Considering the apple yield and the soil available moisture content in 0-15 m layer, the reasonable planting density of apple orchard was 650-800 plants ~ hm-2 in Yan＇ an and 550-700 plants ~ hm-2 in Jingning.