Topographic slope steepness and anthropogenic pressure interact to shape the distribution of tree cover in China

Abstract

Tree cover in China has undergone massive changes through deforestation, reforestation, and afforestation during the last 60 years. This study investigates the distribution of tree cover in the eastern part of China in 2010, and how it is related to climate, topography, and anthropogenic pressure. We use random forest modeling of remote sensing data for tree cover, together with data for topography, climate, and anthropogenic pressure. Our results show that 2,136,000 km2 had tree cover ≥25% in the eastern part of China in 2010 and that the areas with high tree cover were mainly distributed in north-eastern, southern, and south-central China. The variable that best explains the distribution of tree cover is actual evapotranspiration followed by slope and population density. The association between slope and tree cover increases as population density rises, suggesting that the association may be influenced by anthropogenic land use intensity and that slopes act as refugees for forests. Our study emphasizes the need to pay attention to the association between slope and tree cover and especially to the anthropogenic factors that, entirely or to some extent, drive this association.