Response Of Grassland Plant Communities And Soil To Grazing Duration In Mongolia

Mongolia is a country of grassland animal husbandry.With the continuous improvement of national economic development and foreign investment,as well as the impact of global climate and environment changes,the degradation and desertification of grassland are increasingly prominent,and the sustainable development of grassland animal husbandly is facing unprecedented challenges.To clear the degree and influence law of grazing on grassland and to reveal the interaction of grass-soil-livestock has profound significance not only for Mongolia grassland animal husbandry production and the improvement of grassland utilization economic benefits,but also for sustainable economic and social development of Mongolia and Inner Mongolia grassland pastoral area.This study analyzed and discussed the current situation of grassland utilization in Mongolia,in order to promote the sustainable development of grassland animal husbandry and grassland ecological environment protection,meanwhile provide data support and theoretical support for the reasonable development and utilization of grassland and the formulation of basic national policies in Mongolia.The study was applied in Bayanzhurihe SuMu in Khubsugul province,Mongolia via using a two-factor,three grazing mode(whole year grazing,summer grazing and enclosed grazing prohibition)experiment design.Three sites were picked on flat ground and sloping filed,separately.From August 2014 to August 2016,the study measured plant groups,community characteristics,community material content and soil physical and chemical properties of each experimental site,then all the data was analyzed by variance analysis,correlation analysis,dual screening and stepwise regression and optimal parent sequence correlation analysis.The results were as follows:1)The sensitivity of different plant groups is different according to the duration of grazing utilization and the intensity of grazing utilization.On flat experiment site,the aboveground biomass of legume and forbs reduced by 65%to 75%due to grazing,meanwhile moss was formed.On slope experiment site,three was no Cyperaceae but the biomass of Gramineae increased dramatically.No matter on flat or sloping land,the aboveground biomass of grassland plant community decreased in the order of enclosed grazing prohibition,summer grazing and whole year long grazing.2)In plant community material content,crude protein,crude fat and crude ash was positively related to acid washing fiber,however,water content,metabolic energy,total digestible nutrient,nitrogen free extract was negatively related to acid washing fiber.Water content,metabolic energy,total digestible nutrient,nitrogen free extract had positive correlation with neutral detergent fiber.Crude fiber had not correlation with other indexes.3)The in vitro digestibility of forage community decreased with the increase of annual utilization.Under the conditions of different utilization duration,the in vitro digestibility of herbage showed that the whole year long grazing was greater than the summer grazing,and the enclosed grazing was the smallest.In other word,longer grazing duration is conducive to the increase of the in vitro digestibility of herbage.The digestibility of grass in flat area is higher than that in sloping field.4)The correlation between soil physical and chemical properties is weak.Only soil organic matter and conductivity have significant correlation.Soil pH value and soil conductivity increased with the extension of grazing duration.The total nitrogen content of soil in 0-1 Ocm and 10-20cm soil layers showed a decreasing trend with the extension of grazing duration.The soil rapidly available phosphorus increased with the increase of grazing duration.The soil available potassium increased by grazing,especially in summer.5)Plant groups influenced the community characteristics,in which the regression relationship between species number and plant groups was weak.Crude protein,crude fiber,crude ash,acid washing fiber,nitrogen free extract,total digestible nutrients and metabolic energy were affected by Gramineae,Cyperaceae,Compositae,annual and biennials,moss and forbs.Gramineae,Compositae,moss and forbs had a greater impact on in vitro digestibility.6)Summer grazing is beneficial to the sustainable use of grasslands,and grazing on flat grasslands(relative to slopes)also has a positive effect on grasslands protection.Grassland management should be carried out properly in the process of utilization,which is mainly to conduct in-depth research and attention on species composition,soil physical and chemical properties of grassland community.Consider of the current situation of grassland utilization in Mongolia,it is urgent to introduce and popularize the system of grazing in different areas,such as the system of rotation grazing and timely grazing prohibition.