LiDAR-based classification of sagebrush community types

Sagebrush (Artemisia spp.) communities constitute the largest temperate semidesert in North America and provide important rangelands for livestock and habitat for wildlife. Remote sensing methods might provide an efficient method to monitor sagebrush communities. This study used airborne LiDAR and field data to measure vegetation heights in five different community types at the Reynolds Creek Experimental Watershed, southwestern Idaho: herbaceous-dominated, low sagebrush (Artemisia arbuscula) -dominated, big sagebrush (Artemisia tridentata spp.) -dominated, bitterbrush (Purshia tridentata) -dominated, and other vegetation community types. The objectives were 1) to quantify the correlation between field-measured and airborne LiDAR-derived shrub heights, and 2) to determine if airborne LiDAR-derived mean vegetation heights can be used to classify the five community types. The dominant vegetation type and vegetation heights were measured in 3 × 3 m field plots. The LiDAR point cloud data were converted into a raster format to generate a maximum vegetation height map in 3-m raster cells. The regression relationship between field-based and airborne LiDAR-derived shrub heights was significant (R²=0.77; P value <0.001). An analysis of variance test with all pairwise post hoc comparisons indicated that LiDAR-derived vegetation heights were significantly different among all vegetation community types (all P values <0.01), except for herbaceous-dominated communities compared to low sagebrush-dominated communities. Although LiDAR measurements consistently underestimated vegetation heights in all community types, shrub heights at some locations were overestimated due to adjacent taller vegetation. We recommend for future studies a smaller rasterized pixel size that is consistent with the target vegetation canopy diameter.