Remote Sensing Monitoring And Temporal And Spatial Analysis Of Forest Change Characteristics In Southwest China In Recent 20 Years

As the main body of terrestrial ecosystem,forest has a stable ecological environment and is considered as an ideal resource to mitigate climate change,maintain the sustainability of ecosystem services and promote economic diversity.Its changes will have a profound impact on the global natural environment and social and economic sustainable development,especially in the context of carbon peak neutralization,forest carbon fixation has become an important way to enhance the carbon sink capacity of ecosystems.Since the founding of the People’s Republic of China,China has experienced large-scale deforestation.Especially in the 21st century,the intensity of forest resources development and utilization has changed dramatically due to population growth,rapid economic development and national policies.Southwest China is located in the subtropical forest area of China.As the main distribution area of forest resources and timber production area,it provides a large amount of timber for China’s construction.So far,deforestation has basically stopped in the southwest and is gradually shifting from massive deforestation to artificial planting and natural recovery.Therefore,it is of great value to study the characteristics of forest change in southwest China,especially for the effective protection and planning of forest resources.The rapid development of Remote Sensing(RS)and Geographic Information System(GIS)technology has provided spatial and temporal dynamic data at multiple scales for land use change monitoring research,and has been widely used in forest change analysis.In order to accurately identify forest distribution,change and influencing factors in southwest China,based on collecting long time series of land cover data,global forest change(GFC)data,elevation data,vegetation index data,and socioeconomic statistics,this paper extracts forest change information from 2001 to 2019 in southwest China.Using landscape index and emerging hot spot analysis,the spatial and temporal dynamic processes of forest change in southwest China were analyzed.The main conclusions are as follows:(1)From the growth and decline of forest resources,the vegetation in southwest China is dense,and forest land is the main land cover type.From 2001 to 2019,forests have experienced a complex change from"first decrease then increase"to"dynamic balance".On the Google Earth Engine(GEE)platform,the overall accuracy of forest change data extracted from optical remote sensing GFC data in the southwest region is92.53%,and the Kappa coefficient is 0.81,indicating high reliability of data quality.From the change trend,2008 is a turning point.Before 2008,the annual loss rate increased significantly,and after 2008,the fluctuation decreased.Under the influence of the national policy to vigorously promote comprehensive control of desertification in karst areas and promote natural forest protection projects,vegetation gradually moves to artificial and natural recovery,during which the intensity of forest resources development and utilization remains at a high level.From the perspective of spatial distribution,the changes of forests are closely related to topography,and the forests at lower altitudes and gentle slopes are more likely to be damaged.In addition to the impact of national policies,the impact of human disturbance activities such as agricultural development and urbanization is also inseparable from the dynamic changes of forest resources.(2)From the characteristics of forest change patches,the forest loss patches in southwest China are mainly small patches with an average patch area of less than 1 ha.From 2001 to 2019,the average patch area has nearly doubled,from 0.34 ha to 0.61 ha,and the density of the edge of the patches has also increased.Due to human disturbance,the loss of low density(<0.01/100 km~2)and small scale(<1 ha)dominated the spatial distribution,with 41.7%and 32%of total loss area under 1 and 5 ha thresholds,respectively.This also increased the difficulty of forest monitoring and protection management.(3)From the analysis of emerging space-time hot spots,the spatial distribution of forest loss in southwest China is gradually spreading from southeast to the whole region.The emergence of new loss hot spots(large spatially aggregated forest loss patches)in Sichuan and Chongqing means that the forest in this area is undergoing dramatic changes.Loss hot spots are more concentrated in Guangxi,Yunnan and other places.Because of the large area of artificial forests and fast-growing forests,the harvest cycle of tree planting has a significant impact on forest change.Under the background of the increasing intensity of forest resources development and utilization,in the future,we should adhere to the concept of advancing with the time,formulate rational development policies,innovate forestry development mode,and promote the protection of forest ecological environment in the southwest region.