Study On The Suitable Distribution Mechanism And Response Of The Kobresia Meadow In The Three-Rivers Source Region

The Three-Rivers Source Region is in the Qinghai-Tibet plateau,considering the grassland ecological system in the area of the complexity and sensitivity and its great value of ecosystem services,it is quite important that comprehensively evaluate the ecological service value of the region for the maintenance of the ecological environment in the region and the substainable development of the region.As the main grassland types of alpine meadow in the source region of Sanjiangyuan is not only the Kobresia vegetation,natural grassland in the area of the main dominant species,also is the main nutritional source area of grazing livestock protection in Sanjiangyun Region.In recent years,in the background of global climate warming,90% of the natural grassland in the source area of the Three-Rivers Source Region began to be degraded.The “Black Soil Type” degraded grassland is the change of community structure and Kobresia vegetation.So,the investigation is based on MaxEnt and the spatial analyst function of ArcGIS software.Through field investigation and collection of the actual geographical distribution information and environmental variables data of the alpine meadow in the Three-Rivers Source Region,studied on the geographical distribution of the source region of Sanjiangyuan is affected genus Kobresia dominated environments variables revealed genus Kobresia suitability distribution in the Three-Rivers Source Region,understood the genus Kobresia grassland distribution changes in response to ecological planning and policy responses in this area.At the same time,combined with IPCC in the future climate data in 4 different RCPs climate scenarios,analyze the area of genus Kobresia suitability distribution of decadal variation,the main conclusions are as follows:(1)Based on the MaxEnt model,imitated genus Kobresia suitable distribution combined the existing geographic distribution data with environment variables data model.The AUC value is above 0.8,which shows that the simulation precision is very high.According to the classification criteria,suitable distribution simulation results will be divided non viable region,low viable region and high viable region,analyzed the dominant environmental variables affecting the distribution.There are 43 reasons that affected the genus Kobresia suitability distribution in this region.Though the Jackknife of MaxEnt model,displayed elevation,precipitation variation,precipitation in March,precipitation in April,minimum temperature in April,and in May which be main environment variables.The contribution of altitude to be model reaches 39% and it plays a decisive role in the distribution of genus Kobresia.The threshold values of these 6 environmental variables display that the altitude of genus Kobresia in the Three-Rivers Source Region is in 3500-4000 m,and its coefficient of precipitation is in 86-100,and the most suitable precipitation is in March and April.April and May is the most suitable for its growth distribution.(2)According to suitable area,imitate the genus Kobresia suitable distribution from 2005-2014 in the Three-Rivers Source Reguion.From the source of Sanjiangyuan,it displays the trend of gradual decrease from East to West,the area of suitable distribution in east is large,the non viable region in West is large,this is consistent with the gradual rise of the East and West,from the source area of Sanjiangyuan,it further illustrates that the altitude is the main factor affecting the distribution of vegetation of genus Kobresia.At the same time,the high viable region and the main three rivers of the Three-Rivers Source Region are coincided.(3)Extracting data from 1988-2014,the year 2005 is divided into two periods: from 1988-2004,and from the year of 2005 to 2014,for “Sanjiangyuan source area ecological protection project planning” before and after the implementation of Kobresia vegetation distribution comparison.The results show that after the implementation of ecological protection project genus Kobresia in the area,high suitable region has been a significant increase in the rate of 0.1×104km2,this shows that the implementation of the ecological protection policy in the densely populated areas in eastern China has effectively improved the ecological environment in the eastern region of Sanjiangyuan.However,there is also an increase in the area of the western region,the range is 0.46×104km2.Also from another aspect,the omission of the source of ecological protective works,the neglect of the ecological environment in the western region,the ecological environment is deteriorating.(4)The Sanjiangyuan Source Region of 4 future climate scenarios,the simulation results of 2041-2060 and 2061-2080 two period of genus Kobresia suitable distribution area displays that the overall distribution is consistent with the current distribution pattern,the spatial distribution pattern of eastern fitness area is higher than that of the western area.With the increase of RCPs value,in the area of high viable region also increased.Under the RCP 8.5 scenario,the high viable region also increase obviously.From the future 2050s-2070 s climate change,in response to the general trend of genus Kobresia distribution to climate change show that that the area of low viable region is decreasing and the non viable region and high viable region area increased.This shows that the climate environment of the eastern area of Sanjiangyuan source changes to Kobresia vegetation growth,but the western region is still not suitable for the growth of distribution area increased range of Kobresia vegetation.Therefore,it is necessary to adjust the ecological protection strategy of Sanjiangyuan source protection area in a timely manner.In order to ensure the improvement of the ecological environment in the western region,we should strengthen the ecological protection work in the eastern region.(5)The essay is focus on the barycenter transfer of genus Kobresia suitable region,the result shows that the barycenter transfer of genus Kobresia ranges to high altitude areas in north-western areas according to the law of the distribution of species caused by global warming.The future 4 climate scenarios,regardless of how RCPs changes,Kobresia vegetation shifted the direction consistent,have shown the first transfer to the northwest to the southeast,after the transfer.When transferring to the northwest,there is little difference in the transfer distance between the 4 climate scenarios,when transferring to the southeast,the RCOs6.0 transfer distance is larger.