Use of lidar for monitoring vegetation growth dynamics in reclaimed mine lands in Kentucky

Abstract

Surface coal mining in the Appalachian region has led to a significant forest disturbance over time. Evaluating the effectiveness of current reclamation practices in promoting vegetation growth on reclaimed mine sites is a key to understanding how much vegetation has changed in those sites since reclamation. This study employed statewide airborne lidar data to assess changes in lidar vegetation structural metrics on reclaimed mine lands in the Lower Levisa Watershed of Eastern Kentucky between 2011 and 2019 and compare vegetation growth at various reclaimed sites reclaimed in different decades. Eighteen inactive surface mines were selected for the study and categorized into four groups based on the release of their reclamation bonds in different decades. Lidar point cloud data were processed in ArcGIS Pro using filtering and segmentation algorithms to calculate various vegetation attributes from the point clouds, including maximum vegetation height (H_max), mean height (H_mean), standard deviation of height (H_SD), canopy cover (CC), and height percentiles (10, 50 and 75), which were represented as lidar metrics. The process of generating the lidar metrics involved creating Digital Elevation Models (DEMs) and Digital Surface Models (DSMs), calculating Canopy Height Models (CHMs), creating LAS height metrics and generating point statistics rasters to derive these metrics. Change maps for each metric were visually assessed over time, and circular plots with a radius of 12 m were established within each site for further statistical analysis. Significant changes in lidar vegetation metrics were observed between 2011 and 2019 with significant differences among sites reclaimed at different time periods. There was an overall increase in H_mean from 2011 to 2019, with values ranging from 2.4 to 3.8 m. Sites reclaimed in the 1980s experienced an average decrease in canopy cover of −0.5%, while those from the 1990s, 2000s, and 2010s demonstrated increases of 4.9%, 10.1%, and 18.1%, respectively, suggesting that canopy growth rates are higher in younger sites compared to older ones. Vertical variability of the vegetation also increased over time, as indicated by increasing H_SD values. Utilizing statewide airborne lidar data allowed for a comprehensive and detailed assessment of vegetation dynamics on reclaimed mine lands. The findings of this study serve as a foundation for future research endeavors focused on vegetation recovery assessment and success in reclaimed mine lands using lidar data.