黄土高原不同降水量区苹果园土壤干燥化效应及生产水足迹模拟

Simulation of soil desiccation effects and production water footprint of apple orchards in different precipitation areas of the Loess Plateau,China

为探明黄土高原地区旱作苹果园深层土壤干燥化效应和生产水足迹动态变化,选择半湿润区洛川和半干旱区米脂两个典型苹果种植区,采用WinEPIC模型定量模拟分析两个区域1980—2020年旱作苹果园0~15 m土壤水分动态变化和苹果生产水足迹演变规律。结果表明:洛川和米脂成龄果园年产量大致呈“S”型趋势变化,年均值分别为24.64和18.42 t·hm^(-2);年均蒸散量分别为623.82和458.97 mm,年均干旱胁迫日数分别为20.4和52.73 d,年均水分过耗量分别为167.94和121.15 mm。洛川1~25龄、米脂1~23龄果树土壤有效含水量下降趋势明显,土壤干燥化速率分别为64.6和68.03 mm·a^(-1);洛川和米脂深层土壤干层形成的时间为第13年和第7年,并分别于第23年和第22年后达到稳定,降水量高的地区形成和达到稳定土壤干层的时间较晚,如果土壤水分长期处于亏缺状态,最终会形成不可逆转的土壤干层。洛川和米脂苹果生产水足迹均呈前期低后期高的特征,年均生产水足迹值分别为0.187和0.194 m^(3)·kg^(-1)。苹果产量和生产水足迹受降水影响,在水资源短缺的黄土高原地区,为了苹果产业能够持续健康发展,建议苹果树最佳种植年限为23年左右,最多不应超过25年。

To clarify the desiccation effect of deep soil and water footprint of crop production in two typical dry-farming apple orchards on the Loess Plateau of China,with Luochuan County in semi-humid region and Mizhi County in semi-arid region as two typical apple planting areas,we used the WinEPIC model to quantitatively simulate and analyze the variations of soil moisture from 0 to 15 m and water footprint of apple production during 1980-2020.The results showed that annual yield of mature orchards in Luochuan and Mizhi followed an“S”curve,with the average annual values being 24.64 and 18.42 t·hm^(-2),respectively.The average annual evapotranspirations of Luochuan and Mizhi were 623.82 and 458.97 mm,the average annual drought stress days of Luochuan and Mizhi were 20.4 and 52.73 days,and the water overconsumption were 167.94 and 121.15 mm,respectively.The available soil water contents in Luochuan and Mizhi showed a sharp decline from 1 to 25 years old and from 1 to 23 years old,respectively,with average annual soil desiccation rates being 64.6 and 68.03 mm·a^(-1),respectively.The dry layer of deep soil for the orchards of Luochuan and Mizhi appeared at the 13 th and 7 th years,and would be stable after 23 and 22 years,respectively.The formation and stability time of the soil dry layer in the area with high precipita-tion was later than that with low precipitation.Long-term soil moisture deficit would result in irreversible soil dry layer.Water footprint of apple production in Luochuan and Mizhi were low in the early stage and high in the later stage,with the average annual values being 0.187 and 0.194 m^(3)·kg^(-1),respectively.Both apple yield and production water footprint were affected by precipitation.To ensure the sustainable and healthy development of apple industry,it was recommended that the optimal planting age of apple trees is about 23 years on the Loess Plateau where water sources is limited,and the maximum should not exceed 25 years.