Spatial-temporal Evolution And Prediction Of Carbon Storage In Qilian Mountain National Park Based On Land Use Changes

The carbon storage of terrestrial ecosystems is an important part of the global carbon storage,which is significant to mitigate climate change and regulate the global carbon cycle.The Qilian Mountains National Park is an essential ecological security barrier in western China,playing a key role in carbon sequestration and oxygen release,wind and sand control,water conservation,biodiversity protection and other ecological functions.Since the 1970s,anthropogenic disturbances and significant climate changes have caused serious damage to its ecological environment.Therefore,exploring the spatial and temporal distribution characteristics of land use changes as well as carbon storage before and after the establishment of Qilian Mountain National Park is of scientific value for land use structure optimization,ecological carbon sink database construction and sustainable ecological management.Based on the scientific fact that land use changes and terrestrial ecosystem carbon storages are closely related,this study selects 1980,1990,2000,2010 and2018 as time nodes,using InVEST model to analyze the spatial and temporal characteristics of terrestrial ecosystem carbon storages on the basis of clarifying the land use changes and regional ecological patterns in Qilian Mountains National Park.Then,CA-Markov model was used to predict land use changes and carbon storage changes under natural development scenarios and ecological protection scenarios in2030.Finally,the carbon storages ecological function zoning were determined by Hotspot analysis,and countermeasures and management suggestions for increasing carbon storage in national parks were put forward.The main results are as follows:（1）From 1980 to 2018,the spatial and temporal pattern of land use in Qilian Mountains National Park changed significantly,and the regional ecological pattern tended to be fragmented.Grassland is the most dominant land use type,accounting for about 42.96%of the study area.The area of forest,water and build-up land increased,while the area of cropland,grassland and unused land decreased,with the largest increase of 77.07%for water and the largest decrease of 3.12%for unused land.The transformation of each land use type is frequent,and the area of land use that changed account for 11.77%of the total area of the national park,among which the transformation between forest and grassland,and their mutual transformation with cropland and unused land are more frequent.The long-term protection and management have made the overall landscape aggregation and diversity of the national park higher and the ecological function more stable,but the fragmentation of the overall landscape pattern has gradually deepened after 2000 and the ecological process is unstable.Forest,grassland and unused land tend to be fragmented,and the degree of concentration and contiguity of water and build-up land tends to increase.（2）From 1980 to 2018,carbon storage in Qilian Mountain National Park increased by 8.24×10~6t C,with an overall increase of 1.37%.The spatial distribution pattern of carbon storage is roughly the same,showing the overall spatial distribution characteristics of"low in the west and high in the east",which is directly related to the distribution of vegetation.The low carbon storage areas are mainly distributed in the west section and west of the middle section of national park,corresponding to unused land.The high values of carbon storage are mainly distributed in the east section and the east of the middle section,corresponding to forest.The median carbon storage is scattered in the western section of the study area,corresponding to water.The distribution of carbon storage has an obvious topographic effect,and the average carbon storage shows a trend of increasing and then decreasing with the rise of elevation and slope,with the maximum average carbon storage in the area with altitude of 2700-3700m,slope of 15°-25°and shady slope,which were respectively164.22 t/hm~2,124.98 t/hm~2and 126.53 t/hm~2.The changes of carbon storage are related to land use changes,as the positive evolution of ecosystem is the main reason for the increase of carbon storage.（3）The carbon storage service function in 2030 is stronger than that in 2018 no matter in the natural development scenario or ecological protection scenario,but the carbon storage increases differently in different scenarios.Under the natural development scenario,the carbon storage in Qilianshan National Park is 6.19×10~8t C and the carbon density is 123.40 t/hm~2;under the ecological protection scenario,the carbon storage in Qilianshan National Park is 6.55×10~8t C and the carbon density is130.63 t/hm~2,which means that the carbon storage increases more significantly under the ecological protection scenario,and grassland will be the most potential land use type with carbon sequestration.Overall,the establishment of the national park and the consolidation of ecological protection measures have contributed to the increase of carbon storage in Qilianshan National Park.