围栏禁牧对毛乌素沙地土壤理化特征的影响

Effects of continuous grazing and livestock exclusion on soil properties in a degraded Mu Us sandy grassland,Inner Mongolia,northern China

过度放牧导致干旱半干旱区毛乌素沙地草地严重退化。通过禁牧措施排除放牧干扰,使草地自然恢复,作为一种低投入的措施在世界各国退化草地生态系统恢复中得到广泛采用。文中对毛乌素沙地三种不同管理类型(持续放牧、围栏5年和围栏16年)土壤理化性状进行了研究,研究结果显示:围栏禁牧5年对0～30cm土壤颗粒组成和容重没有显著影响;围栏禁牧16年0～10cm土壤容重显著小于持续放牧区,而极细沙、粉粒和粘粒含量显著高于持续放牧区;围栏5年显著增加了0～5cm土壤有机碳,而0～30cm的全氮均没有显著增加。围栏16年土壤有机碳较放牧区在0～5cm、5～10cm、10～30cm分别显著增加了231%、81%、55%;全氮含量的变化趋势与之相同。结果表明,围栏5年对土壤粘粉粒、全氮含量的恢复基本没有效果;围栏16年能显著增加表层土壤粘粉粒含量和有机碳、全氮,但土壤碳、氮水平还是在比较低的水平(有机碳:4.30g.kg-1;全氮:0.74g.kg-1),即长期禁牧可以逐渐改善土壤质地和提高土壤肥力。研究结果为半干旱退化沙质草地生态系统的恢复、重建及管理提供科学依据。

Overgrazing by domestic livestock has greatly degraded many arid and semiarid grassland ecosystems around the world,and it does in the Mu Us sandy grassland.Exclusion has been applied as a main measure for revegetation all over the world,which may be an effective,financially economical and natural way to restore.In this paper,we examined three grazing management treatments： continuous year-long livestock grazing（grazing）,grazing excluded for 5 years（5-yr exclosure） and grazing excluded for 16 years（15-yr exclosure）,analyzed the effects of grazing exclusion on soil physical and chemical properties.The results as follows： The 5-yr exclosure had no discernible influence on soil particle size distribution and bulk density in 0～30 cm soil layer as compared with continuous grazing.The 16-yr exclosure increased the proportion of very fine sand（0.1-0.05mm）,silt（0.05-0.002mm） and clay（〈 0.002mm）,and decreased bulk density in 0～10 cm.The 5-yr exclosure enhanced soil organic carbon concentration（SOC） in 0～5 cm,and had no effect on total nitrogen accumulation in 0～30 cm.SOC increased significantly by 231%,81% and 55%,respectively,in the 0-5,5-10 and 10-30cm soil layers in 16-yr exclosure as compared with grazing treatment.The 16-yr exclosure effects on total N followed the same trend as SOC.The results suggested that soil chemical and physical properties can be improved with the implementation of protecting from grazing.