Effects Of Different Grazing Systems On Grassland And Its Soil Anti-scourability On The Northern Slope Of The Tianshan Mountains

Grassland ecosystems not only provide humans with the necessary means of production,but also play an important role in water conservation,soil and water conservation,windbreak and sand fixation,climate regulation,and carbon cycle.As one of the main ways for humans to use grassland,grazing activities mainly affect the grassland ecosystem through the feeding,trampling and excretion of livestock.This resulted in a series of problems such as grassland degradation and increased soil erosion.Xinjiang is one of the five major pastoral areas in our country.Due to its unique climate and topography,grassland types are diverse and widely distributed,which provides an important material basis and guarantee for the development of livestock production in the region.But at the same time,there are problems such as lower grassland primary productivity,deterioration of grassland ecological environment,and serious soil erosion.The west Baiyanggou watershed is located in the middle and low mountains of the northern slope of the Tianshan Mountains.It serves as a water source conservation area for the Urumqi River system and is also one of the main pastures and summer resorts in Urumqi.It has played a key role in animal husbandry,soil and water conservation,sand fixation and wind protection,and climate regulation in the region.To investigate the impact of grazing activities on grassland ecosystems,this study took the west Baiyanggou watershed on the northern slope of the Tianshan Mountains as a study area to investigate and analyze the effects of three different grazing systems on grassland vegetation and soil.Using field water scouring method,using surface runoff sediment yield as index and bare land as reference object,the dynamic characteristics of runoff sediment yield,total sand yield and soil erosion resistance of different grazing pastures were studied.The principal component analysis method and the grey correlation method were used to evaluate and analyze soil Anti-scourability and its main influencing factors of different grazing systems in order to provide a theoretical basis for the optimal management of forage resources and soil and water conservation on the northern slope of the Tianshan Mountains.This study mainly draws the following conclusions:(1)In the pastures with three different grazing systems,with the increase of grazing intensity and frequency,the vegetation height and coverage of continuous grazing pastures were significantly lower than that of forbidding grazing pastures and seasonal grazing pastures(P<0.05);Aboveground biomass is expressed as seasonal grazing pastures(263 g/m2)> forbidden grazing pastures(250 g/m2)> continuous grazing pastures(162 g/m2),of which free grazing pastures are significantly lower than forbidden grazing and seasonal grazing pastures(P<0.05);The root density of vegetation is: forbidden pasture(0.012 g/cm3)> seasonal pasture(0.009 g/cm3)> continuous pasture(0.006 g/cm3),the root density of forbidden pasture is significantly higher than that of seasonal pasture and continuous grazing pastures(P<0.05).(2)In pastures with different grazing systems,the soil bulk density and compactness of forbidden pastures are significantly lower than that of seasonal pastures and continuous pastures(P<0.05);With the increase of grazing intensity and frequency,the soil moisture content showed a decreasing trend,of which that of the forbidden pasture and seasonal grazing pastures was significantly higher than of continuous grazing pastures(P<0.05);The soil organic matter in the forbidden pasture is significantly higher than that of the seasonal pasture and continuous pasture(P<0.05);The soil mechanical composition in the study area is mainly composed of sand and silt.The clay content is extremely low.With the increase of grazing intensity,the sand content of the soil showed a significant increasing trend(P<0.05),while the soil silt showed In the opposite trend,the soil clay increased with grazing intensity,but the difference was not significant(P<0.05).(3)With the increase of water discharge,the sediment yield per unit time and the total runoff sediment yield show an increasing trend,the initial sediment yield is the largest under each water discharge;With the continuation of time,the sediment yields all show a declining trend.Among them,bare land and continuous grazing pastures have higher initial sand yields than seasonal grazing pastures and forbidding pastures,the amount of sand production tends to be flat late,and the rate of decrease in sand production and the trend is slower.(4)The best indicators for evaluating the erosion resistance of the surface soil of the pastures with different grazing systems are grassland vegetation characteristics,soil organic matter and slope,the comprehensive index of soil erosion resistance is forbidden grazing pasture(2.356)> seasonal grazing pasture(2.131)> continuous grazing pasture(2.06).(5)The gray correlation analysis results show that the strength of the soil impact resistance is the result of the combined action of various influencing factors,among them,the four indicator factors of soil bulk density(0.791),slope(0.789),root density(0.757),and powder content(0.755)have a greater impact on the soil Anti-scourability in the region.(6)Fencing,grazing prohibition and seasonal grazing in the study area can significantly improve grassland vegetation characteristics and soil structure and quality,reduce soil erosion,and enhance soil Anti-scourability.