川西北高寒沙化草地围栏禁牧时段和恢复过程的耦合机理研究

Coupling Mechanism of Grazing Exclusion Period and Recovery Processes in Alpine Desertification Grassland in Northwest Sichuan

川西北沙化草地在围栏禁牧生态恢复过程中,土壤中有机质、全氮、水解性氮变化特征,研究对象为:未修复沙化草地、围栏禁牧生态恢复时间分别为5年、10年的沙化草地,研究其不同围栏禁牧时间沙化草地0~40 cm土层土壤中有机质、全氮、水解性氮的变化。其结果表明,随着围栏禁牧时间的增长,各土层土壤有机质、全氮含量均增加,植被盖度、高度均极显著提高,其中,增加幅度较大的是0~20 cm土层。围栏禁牧10年,沙化草地土壤有机质、全氮含量比未修复沙化草地分别增长34.05%、27.89%,均显著高于未修复沙化草地;各土层土壤水解性氮含量却呈现先减少后增加的特征,其中,0~20 cm土层,围栏禁牧5年沙化草地较未修复沙化草地水解性氮含量减少了23.80%,围栏禁牧10年沙化草地较围栏禁牧5年沙化草地水解性氮含量增加了24.19%;20~40 cm土层,围栏禁牧5年沙化草地较未修复沙化草地水解性氮含量减少了31.49%,围栏禁牧10年沙化草地较围栏禁牧5年沙化草地水解性氮含量增加了1.13%。

In the process of ecological restoration of grazing exclusion desertification grassland in northest Sichuan,the variation characteristics of soil organic matter,total nitrogen and hydrolytic nitrogen in 0−40 cm soil layer of unrestored sandy land,and grazing exclusion grassland with ecological restoration time of 5 and 10 years respectively were studied.The results showed that with the increase of grazing exclusion time,the vegetation coverage and height increased significantly,and the contents of soil organic matter and total nitrogen in each soil layer increased,especially in 0−20 cm soil layer.After 10 years of grazing exclusion,the contents of soil organic matter and total nitrogen in sandy land increased by 34.05%and 27.89%respectively,which were significantly higher than those in unrestored desertification grassland.However,the content of soil hydrolytic nitrogen in each soil layer decreased at first and then increased.In 0−20 cm soil layer,the hydrolytic nitrogen content of the fenced desertification grassland with 5-year grazing exclusion decreased by 23.80%compared with that of the unrestored desertification grassland.Compared with 5-year grazing exclusion sandy grassland,the hydrolytic nitrogen increases by 24.19%in 10-year grazing exclusion sandy grassland.In the soil layer of 20−40 cm,the hydrolytic nitrogen content of sandy grassland with 5-year grazing exclusion decreased by 31.49%compared with that of the unrestored desertification grassland,and the hydrolytic nitrogen content of desertification grassland with 10-year grazing exclusion increased by 1.13%compared with that of the 5-year grazing exclusion desertification grassland.