Fire has become a major disturbance agent in the forests of Southwest China

Abstract

Retrospective analysis of forest dynamics is indispensable for formulating forest management policies. However, such work is rarely performed at a regional scale in China, especially the southwest region that serves as an important carbon sink. Here, we employed annual Landsat images and LandTrendr to map stand-replacing forest disturbances and attribute them to anthropogenic, geological disaster, fire, and logging in the Sichuan province from 2001 to 2020. The results show that the Overall Accuracy (OA) of disturbance map reaches 90.5 % (±0.6 %) (95 % confidence interval) after unbiased estimation. An estimated 1.3 % (2910.0 ± 1274.1 km2) of the forest area has been disturbed as of 2020. Fire is the dominant factor that comprises 36 % of the total disturbance area, followed by geological disaster (30 %), anthropogenic (17 %), and logging (17 %). In contrast to geological disaster dropping rapidly over the last 20 years, fire increased by 58 %, while anthropogenic disturbance and logging tripled and doubled respectively. The spatial distribution of forest disturbances in Sichuan province is as expected, characterized by fire predominantly disturbing natural forests of western and southern after the implementation of the natural forest protection policy, most geological disaster occurring in northern areas adjacent to the plateau and basin, most logging occurring in southeastern planted forest areas, and most anthropogenic disturbance occurring in eastern flat basin area. Our results present a regional-scale pattern of Sichuan’s forest disturbance agents and their changes over time, which enhances our ability to accurately assess forest management, carbon dynamics, and potential disturbance risk mitigation in the region.

Keywords

• Forest disturbance
• LandTrendr
• Southwest China
• Random forest model
• Fire