Woody plant cover trends and potential drivers in the Horqin temperate steppe, northeast China: Remote sensing-based computation and modeling

Abstract

The Horqin temperate steppe is the largest grassland in northern China. With the combined disturbance of multiple potential drivers, the native herbaceous vegetation has degraded with different intensity, and woody plants have transformed into the dominant vegetation in this area. On the one hand, woody plants play an important role in sand control, food/timber product provision, etc. On the other hand, this transformation process significantly affects the steppe ecosystem structure and function. It is necessary to clarify the patterns and determinants of woody plant cover changes. In view of the lack of high spatio-temporal resolution remote sensing data for woody cover. Here, based on high-resolution satellite images and the random forest model, the study reports the annual mean woody plant cover of the Horqin temperate steppe is 17.55 % over the past 35 years, and the significant increase area is approximately 43.7 % of the total area. Analysis of the boosted regression tree model showed potential drivers were mainly attributed to climate change (i.e., mean annual temperature, mean annual wind speed, and annual precipitation) and grazing intensity, with the cumulative contribution approaching 70 %. Furthermore, large-scale and high-density afforestation could also be responsible for the increase in woody plant cover. Against the background of frequent climate extremes, maintaining and improving steppe productivity, avoiding regional climate deterioration caused by blind afforestation, and developing a reasonable grazing management policy is the urgently needed to ensure the relative ecological stability of semi-arid temperate steppes and to achieve relatively sustainable development of the regional agro-pastoral economy.