Spatial And Temporal Change Of Vegetation Coverage And Ecological Security Patterns In Key Areas In Xilingol League

Grassland is the largest terrestrial ecosystem and an important ecological barrier in China.It plays many important ecological functions,such as windbreak and sand fixation,water and soil conservation,water conservation and biodiversity maintenance.As an important component of grassland ecosystem pattern,grassland vegetation is the most vital ecological factor in grassland environment and the resource carrier for the survival and development of grassland people.Over the years,grassland vegetation has experienced endless vicissitudes and frost baptism while protecting green,resisting wind and sand,nurturing life and carrying civilization.Especially in recent years,the global climate warming and the impact of human activities have intensified,and the grassland ecological landscape has changed dramatically.Vegetation degradation,grassland desertification and their related effects are very prominent,which has become an important bottleneck restricting the sustainable development of regional and even national economy and society.Taking the change of vegetation cover as the breakthrough point,the research on the dynamics and protection of vegetation restoration is helpful to further understand the evolution law of grassland ecosystem.It is of great scientific value and practical significance to enrich and develop the theory of grassland ecological restoration and to effectively guide grassland ecological protection,vegetation construction and regional sustainable development.Based on the long time series remote sensing data of vegetation cover in Xilinguole League,supported by GIS,remote sensing technology and structural equation model,and combined with field investigation,the vegetation cover in Xilinguole League was analyzed from multi-time and multi-angle by using the theories and methods of cartography and geographic information system,landscape ecology,land evaluation and management,geostatistics and other disciplines.Based on the spatial-temporal variation and restoration dynamics of degree,the influencing factors of spatial differences and their mechanism were quantitatively analyzed.Based on this,the key ecological units with strategic significance for regional vegetation restoration and ecological security were simulated and identified.The ecological security of key ecological areas was evaluated by coupling natural and human disturbances,and the ecological security pattern and strategies for vegetation restoration were put forward.Vegetation restoration and grassland ecosystem management under the influence of human activities provide scientific basis.The main results obtained are as follows:(1)Xilingol League is dominated by natural vegetation.From 1981 to 2006,the regional vegetation coverage tended to decline as a whole.During the study period,the degree of vegetation restoration varies greatly in space,the vegetation in the East tends to improve,and the vegetation in the West tends to degenerate.On the whole,the area of vegetation degradation is larger than that of improvement.(2)From 1961 to 2000,the annual precipitation in 93.76%of the study area showed an increasing trend,which played a positive role in the increase of vegetation coverage.The most obvious rainfall area for vegetation improvement was 200-250mm.From 1961 to 1998,the annual average temperature increased slightly with the years.93.8%of the regional average temperature was positively correlated with vegetation coverage.From 1998 to 2010,the vegetation in the 900-1200m elevation distribution area improved significantly,and the vegetation coverage in the 0-3-degree gradient distribution area changed significantly.Under the same gradient conditions,the frequency of vegetation degradation units was higher.(3)At the level of 2000-2010 and each county,annual precipitation,annual mean temperature variation,average elevation,average gradient and maximum cultivated area are the dominant factors affecting the average change of vegetation coverage,which jointly explain 96%of the change of vegetation coverage,and the direct effect of annual average precipitation on vegetation restoration is the greatest;average elevation,average gradient,annual average precipitation and annual average temperature are the main factors affecting the average change of vegetation coverage.Equivalent variability and annual average livestock carrying capacity are the main factors affecting the spatial variability of vegetation coverage.The interpretation degree is 0.89.The variation coefficient of average elevation has the greatest effect on the spatial variability of vegetation coverage,followed by the variation coefficient of annual average precipitation.(4)From 1981 to 2006,the spatial drift of the center of gravity in the best vegetation coverage area(over 0.8 vegetation coverage)was large,showing obvious instability and fluctuation.The largest proportion of the best vegetation coverage unit was 33%(1996)and the smallest was 6%(2000)during the period of historical study.With the progress of time,the proportion of the best vegetation coverage space showed a downward trend.(5)According to the optimal distribution and frequency of vegetation cover units,the distribution of key ecological units for vegetation restoration was determined.The key area of Vegetation Ecology in the study area was 20794 km2,accounting for 10.38%.Through the analysis of spatial obstruction of key ecological units,the ecological functional areas of vegetation restoration in the whole region were delineated.(6)Taking into account the factors of physical geography,social and economic development and their differences,the ecological security evaluation model of key ecological areas was constructed from the perspectives of landscape pattern stability,ecological vulnerability and human disturbance.The ecological security pattern was determined,and the strategies of vegetation restoration and ecological protection were put forward.