黑河中游荒漠绿洲区土地利用的土壤养分效应

土地利用影响地表覆被状况和生态过程,关系到土壤肥力与土壤碳库功能"源-汇"关系的改变。黑河中游甘州区和临泽县是我国西北干旱区典型的荒漠绿洲区,以土壤表层(0-20 cm)养分变化为对象,利用2011-2012年甘州区和临泽县的土壤野外调查数据和该区全国第二次土壤普查数据,对两时期土壤表层养分(土壤有机质、全氮、全磷、全钾及pH值)的变化特征进行比较研究。结果表明:研究区土壤有机质、全磷含量分别降低了3.54%和12.5%;而全氮、全钾和pH值分别增加了74.4%、98.2%和4.9%。全国第二次土壤普查时期,荒漠、耕地与草地三者在各土壤养分上没有显著差异,但林地在土壤有机质、全氮、全钾上显著高于前三者。2011-2012年,耕地土壤的全磷、全氮与其它土地利用存在显著差异。土地利用的保持和改变对土壤养分变化有着重要影响,耕地的长期耕作使得土壤有机质含量降低4.94%,全氮增加86.93%,全磷减少5.02%,土壤碱性增强;荒漠植被的自然演替使土壤有机质含量增加66.21%,全氮增加71.70%,全磷含量减少37.33%,土壤碱性变弱。所以,耕地扩张及其长期耕作活动将导致地力退化并有盐碱化风险,而荒漠等自然生态系统保护有利于土壤肥力的改善和土壤固碳功能的发挥。

Effects of land use on soil nutrient in oasis-desert ecotone in the middle reach of the Heihe River

Land uses have significant impacts on the changes of land surface covers and ecological processes. Land use type is closely related to the soil fertility and soil carbon pool function. The Ganzhou District and Linze County of Gansu Province, as the typical oasis-desert ecotones, is located in the middle of Heihe River Basin in northwest arid region of China. The topsoil samples were took from the 0-20 cm depth land surface. The topsoil was sampled at Ganzhou District and Linze County during 2011-2012. The soil nutrients were tested in the laboratory including soil organic matter, total nitrogen, total phosphorus, total potassium and pH. We compared the sampled soil nutrients with the national secondary soil survey data in 1980s which have the similar parameters of soil nutrient and pH.The results showed that the soil organic matter and total phosphorus decreased by 3.54% and 12.5%, respectively, during 2011-2012 in comparison to 1980s. Whereas, the soil total nitrogen, soil total potassium and pH increased by 74.4%, 98.2%, and 4.9%. There had no significant differences of soil nutrients among the desert, cropland and meadow in 1980s. However, the soil nutrients of forest were significantly higher than those of the above three land uses such as soil organic matter, soil total nitrogen and soil total potassium. During the period of 2011-2012, the soil total phosphorus, soil total nitrogen of cropland were significantly different from those of the forest, meadow and desert. The results indicated that the long-term farming activity of cropland reduced soil organic matter by 4.94% and soil total phosphorus by 5.02%, but increased soil total nitrogen by 86.93% and made soil more alkaline. The results also showed that the desert can increase of soil organic matter and soil total nitrogen by 86.93% and 71.70% whereas decrease the soil total phosphorus and soil alkalinity as well. Therefore, the cropland expansion and long-term farming activities can lead to the soil fertility degradation coupling with the risk of salinization. However some natural ecological systems, such as the desert, are favor to improve the soil fertility and soil carbon sequestration.