Spatiotemporal Dynamic Characteristics of Land Use in the Typical Watershed of Wenchuan Earthquake-Affected Areas—A Case Study in the Longxi River Basin

Major earthquakes cause serious damage to ecosystem structure and function through their huge destructive force and subsequent geohazards. Understanding the characteristics of post-earthquake land use change is of great interest to assess the effects of ecological restoration in earthquake-affected areas. However, little is known about the consequences of land use change on a small scale due to incomplete, non-comprehensive, and sparse research data. Here, we used remote-sensing images to study the land use change characteristics of the Longxi River before and after the Wenchuan earthquake by calculating the land use dynamics degree, transition matrix, and gravity center of the Longxi River Basin from 2005 to 2015. The Wenchuan earthquake disaster did not affect the main dominance of forests. Grassland, the second dominant land type, was replaced by geohazard-induced unutilized land after the earthquake. Compared with pre-earthquake in 2005, the areas of cultivated land, forest, grassland, and water area decreased, while those of construction land and unutilized land increased in 2015. The single land use dynamic degree and spatial dynamic change degree show the highest transition intensity of other land use types to unutilized land between 2005 and 2009. However, the degrees of all land use types decreased between 2009 and 2015. Both banks of the lower reach of the Longxi River had high and developing comprehensive indexes of land use degrees during the study period. The gravity centers of grassland, construction land, water, and cultivated land changed from north to south, while forest and unutilized land had the opposite pattern. Our results provide useful information for ecological restoration, ecological security, and soil-erosion control in earthquake-affected areas.