祁连山黑河上游不同退化草地土壤理化性质及养分和酶活性的变化规律

为了揭示草地退化过程中土壤理化性质及养分和酶的变化规律,在祁连山黑河上游俄博岭研究了4种草地土壤理化性质及养分和酶活性的变化规律.结果表明:未退化草地与退化草地、中度退化草地和重度退化草地比较,0~60 cm土层有机碳、有机碳密度、有机碳储量随退化程度加剧呈显著减少趋势;土壤理化特性的总孔隙度、团聚体、物理性粘粒、饱和蓄水量、田间持水量随土壤退化加剧呈减少趋势,同时CEC、碱解氮、速效磷、速效钾、脲酶、蔗糖酶、磷酸酶、多酚氧化酶、过氧化氢酶等养分和酶活性也随土壤退化加剧呈明显减少变化.随着土壤退化加剧,容重、物理性砂粒、石砾、pH值以及CaCO3含量均有明显的增长.4种草地0~60 cm土层孔隙度、团聚体、物理性粘粒、饱和蓄水量、田间持水量、土壤有机碳、速效氮磷钾和酶活性均值由大到小的变化顺序为:未退化草地轻度退化草地中度退化草地重度退化草地;容重、物理性砂粒、石砾、pH、CaCO3均值由小到大的变化顺序为:未退化草地轻度退化草地中度退化草地重度退化草地.不同层次孔隙度、团聚体、物理性粘粒、饱和蓄水量、田间持水量、土壤有机碳、速效氮磷钾和酶活性均值随着土层垂直深度的增加而递减,而容重、物理性砂粒、石砾、pH、CaCO3均值随着土层垂直深度的增加而递增.

Soil physicochemical properties and variations of nutrients and enzyme activity in the degrading grasslands in the upper reaches of the Heihe River,Qilian Mountains

In order to reveal the soil physical and chemical properties, as well as the variations of nutrients and enzyme activities, in the degrading grasslands in the upper reaches of the Heihe River, Qilian Mountains, by using field investigation and laboratory tests, four kinds of grass profile are studied. It is found that as compares with non-degraded grassland, the mild degraded grassland, moderate degraded grassland and severe degraded grassland, in the depth range of 0~60 cm, organic carbon content decreases 10%, 12% and 28%, respectively; organic carbon density decreases 11%, 21% and 31%, respectively; total porosity decreases 3%, 7%and 12%, respectively; aggregate decreases 19%, 28% and 39%, respectively; clay particle decreases 6%, 12% and 18%, respectively; saturated storage capacity decreases 3%, 7% and 12%, respectively; field capacity decreases 10%, 14% and 19%, respectively; CEC decreases 8%, 17% and 33%, respectively; alkali-hydrolyzable nitrogen decreases 10%, 22% and 36%, respectively; rapid available phosphorus decreases 15%, 25% and 46%, respectively; rapidly available potassium decreases 4%, 8% and 13%, respectively; urease decreases 5%, 19% and 34%, respectively; sucrose decreases 27%, 43% and 54%, respectively; phosphatase decreases 15%, 32% and 44%, respectively; polyphenol oxidase decreases 12%, 25% and 38%, respectively; catalase decreases 14%, 30% and 46%, respectively; bulk density increases 4.3%, 8.6% and 14.7%, respectively; sand increases 12.5%, 25% and 38.5%, respectively; gravel increases 18%, 39% and 63%, respectively; pH value increases 0.10, 0.21 and 0.28 units, respectively; CaCO₃ increases 3.9%, 8% and 12.1%, respectively. In the depth range of 0~60 cm, soil porosity, aggregate, clay particle, saturated storage capacity, field capacity, available NPK, soil organic carbon and enzyme activities decrease as: non-degraded grassland>mild degraded grassland>moderate degraded grassland>severe degraded grassland; bulk density, sand, gravel, pH value and CaCO₃ increase as: non-degraded grassland3 increase with depth.