黄土高原半干旱和半湿润地区刺槐林地生物量与土壤干燥化效应的模拟

Simulation of biomass and soil desiccation of Robinia pseudoacacia forestlands on semi-arid and semi-humid regions of China's Loess Plateau

黄土高原人工刺槐(Robinia pseudoacacia)林地深层土壤干燥化现象普遍发生,日益严峻地威胁着人工植被建设成效。分析和比较半干旱和半湿润地区刺槐林地生物量演变趋势、深层土壤干燥化发生规律和区域分布特征差异,能够为黄土高原因地制宜地营造刺槐林提供科学依据。在WinEPIC模型气象、土壤和作物参数数据库组建与模拟精度验证的基础上,应用WinEPIC模型模拟研究了1957-2001年黄土高原半湿润地区洛川和长武、半干旱地区延安和固原等地1-45年生刺槐林地生物量演变规律和深层土壤干燥化效应。结果表明:洛川、长武、延安和固原的刺槐林地连年净生产力模拟值在5-8年生时达到最大值后,随着降水量年际波动呈现出明显的波动性降低趋势,其平均值分别为5.33×103、4.56×103、4.03×103和3.35×103kg.hm-2.a-1;1-7年生刺槐林地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,洛川、长武、延安和固原刺槐林地年均土壤干燥化速率分别为164.3、165.7、187.1和190.0mm.a-1,8-45年生刺槐林地有效含水量在0-250mm的较低水平上随降水量变化而波动;1-9年生刺槐林地0-10m土层土壤湿度剖面分布变化剧烈,土壤湿度逐年降低且土壤干层逐年加厚,7-9年生时土壤干层厚度已经超过10m,8-45年生刺槐林地2-10m土层土壤湿度保持相对稳定的干燥化状态;洛川和长武刺槐林地水分生产力较高且相对稳定,刺槐林地生长期可以超过45年;而延安和固原刺槐林地水分生产力较低且稳定性差,刺槐林稳定生长期不超过40年。

Aims Deep soil desiccation so commonly occurs in black locust （Robinia pseudoacacia） forestlands of China＇s Loess Plateau that it increasingly counteracts artificial vegetation construction.We analyzed and compared black locust forestlands under different rainfall regions in the Loess Plateau in terms of biomass and incidence and regional distribution of deep soil desiccation in order to provide scientific foundations for constructing black locust forestlands according to local conditions of the Loess Plateau.Methods Based on datasets of weather,soil and crop parameters and simulation precision verification,we researched biomass and deep soil desiccation in the 1-to 45-year-old block of black locust forestlands of Luochuan and Changwu in the semi-humid region and Yan＇an and Guyuan in the semi-arid region of the Loess Plateau from 1957 to 2001 using the WinEPIC model.Important findings In Luochuan,Changwu,Yan＇an and Guyuan,simulated annual net productivities of the 1-to 45-year-old black locust forestlands averaged 5.33 × 103,4.56 × 103,4.03 × 103 and 3.35 × 103 kg.hm-2.a-1,respectively.Productivity peaked when forestlands were 5-to 8-year-old and then tended to decrease in a pattern that followed the fluctuation of annual rainfall.In 1-to 7-year-old forestlands,annual water consumptions were higher than annual rainfalls,which resulted in soil drying at 0-10 m depth;soil desiccation rates in Luochuan,Changwu,Yan＇an and Guyuan were 164.3,165.7,187.1 and 190.0 mm per year,respectively.In 8-to 45-year-old forestlands,the available water fluctuated at a low level within 0-250 mm as annual rainfalls varied.In 1-to 9-year-old forestlands,the 0-10 m soil humidity profiles sharply varied,with annual declines and thickening of dry soil layers.In 7-to 9-year-old forestlands dry soil layers exceeded 10 m thick,and in 8-to 45-year-old forestlands the dry soil layers had relatively stable water humidity.In forestlands of Luochuan and Changwu,the annual net productivities were high and relatively stable,and the growth periods of black locust could exceed 45 years.In forestlands of Yan＇an and Guyuan,the annual net productivities were low and instable,and stable growth periods did not exceed 40 years.