Land Cover Change And Its Ecological Effects In China Based On Fusion Of Multi-source Remote Sensing Product

In recent decades,land cover in China has undergone rapid changes and has become a global hotspot for land cover change.The remote sensing-based land cover datasets provides the basis for the study of land change in China.However,due to differences in sensor types,interpretation flags,and thresholds,the comparability between datasets is poor and cannot provide a clear picture of land cover change trends in China.In addition,land cover change also affects different aspects of the ecological environment.However,studies have focused on the effects of land cover change on single elements of the ecological environment,and there is a lack of comparative analysis of multiple ecological and environmental effects with comparable data sources.Therefore,clarifying the trends of land cover change and its multiple ecological effects in China can better provide a basis for ecological environmental protection,rational development and utilization of land resources,and sustainable social development.This study used multi-source remote sensing and land cover datasets,based on likelihood assessment,consistency analysis,data fusion,and neighborhood analysis,to produce a dataset of land cover fraction in China and further analyze the data consistency and ecological effects of land cover change in China,so as to answer the basic scientific question that“What ecological effects can land cover change in China produce?”The main conclusions are as follows.（1）The data consistency of land cover change in China is low.Under different data sources,the area proportion of forests in China ranged from 9.37%to 28.46%,and the area proportion of grasslands ranged from 15.60%to 48.04%.The distribution and changes of each land cover type in the Medium Resolution Imaging Spectrometer land cover dataset（MCD12Q1）were significantly different from other datasets,especially the distribution of grassland.The areas with concentrated distribution of a single land cover type tend to have higher consistency among datasets,with higher consistency for cropland than for forest,grassland and bare ground.In the consistency of land cover change in China,the proportion of different land cover change regions in the four data sets exceeded 85.28%.The consistency was highest for the increase in built-up land,and the consistency for the decrease in forest was lower than that for the increase in forest.（2）From 2001 to 2018,the area of forest increased and the area of grassland and shrub,cropland and bare land decreased in China.The data comparison showed that the global 30 m land cover remote sensing data product Globeland30 had the highest category similarity and overall accuracy,and European Space Agency land cover dataset（ESACCI）had the highest category accuracy.The highest fraction consistency was found for bare land,and the lowest fraction consistency was found for grassland.The China land cover fraction product-China-LCF_MCD-ESAwas formed through data fusion,which was verified by the data to improve the accuracy of MCD12Q1 and ESACCI data,for example,the correlation coefficient（R²）between the global forest change dataset（Hansen-GFC）and MCD12Q1 could be improved from 0.43 to 0.49.The apparent increase in forest area only accounted for 4.0%of the total forest area,mainly distributed in northeast China;about61.7%of the area of grassland and shrub decreased,and these areas were relatively concentrated in northeast and south China;the area of cropland increased significantly（3.2%）was about equal to the area of decreased significantly（3.0%）,and the increased cropland area was mainly in northwest China;the change of bare land was not obvious,and the significantly increased bare land area only accounted for 0.66%of the total bare land area.（3）The multiple ecological effects resulting from land cover change in China are spatially heterogeneous and irreversible.The conversion of cropland to grassland and shrub has a negative greenness effect（-0.017）and a negative carbon sequestration effect（-0.015 kg C/m²）,and the conversion of forest to grass irrigation has a negative greenness effect（-0.01）and a warming effect（0.079°C）.The negative greenness effect of converting forest to grassland and shrub was stronger with a greater change in forest fraction（slope-0.004）,and the weaker the effect of converting more cropland to grassland and shrub on vegetation carbon sequestration（slope-0.056）.Ecological effects vary widely in magnitude across different climates and altitudes.Therefore,many of the ecological effects of land cover change are irreversible and the rage of ecological effects caused by land cover change is regional.Precipitation distribution is the main driver of the spatial heterogeneity of ecological effects of land cover change.