Spatiotemporal evolutionary characteristics of vegetation restoration after historical earthquake landslides from 1985 to 2020: A case study of Tianshui City, China

Earthquakes occurring in mountainous regions have the potential to trigger a significant proliferation of landslides, greatly change the landforms, and exert a long-term impact on vegetation. Since the resurrection of ancient landslides has shown an upward trend in recent years, exploring the vegetation restoration and landslide activity of historical seismic landslides can prevent the occurrence of disasters in the future. In this study, we offer a novel calculation method for the evaluation of vegetation restoration of historical seismic landslides. There were 469 landslides in our study area that encompassed a total area of 87.70 km². Based on the 30-m resolution normalized difference vegetation index (NDVI) data of the Tianshui City area from 1985 to 2020, which was used to quantify the vegetation restoration and landslide activity in the landslide area, we adopted the indicators of vegetation cover and vegetation restoration rate. In our analysis, the NDVI and FVC of the landslide area showed a fluctuating increase, the vegetation recovery rate of the landslide area using both VRR_M and VRR_N calculations demonstrated an increasing trend, and the number of active landslides decreased. However, the results of the VRR_N calculation more accurately assessed the vegetation recovery of the landslide area in the long term, and proved that recovery was superior in 1990. The restoration of vegetation was affected by regional precipitation, altitude, human activities, and disaster activities; and landslides in the study area recovered least in 1990–1995 and most in 2005–2020. The present study of vegetation restoration for a disaster area provides a reference for the restoration, utilization, planning, and related research of landslide disasters in the region.