Laser Remote Sensing of Canopy Habitat Heterogeneity as a Predictor of Bird Species Richness

Habitat heterogeneity has long been recognized as a fundamental variable indicative of species diversity, in terms of both richness and abundance. Satellite remote sensing data sets can be useful for quantifying habitat heterogeneity across a range of spatial scales. Past remote sensing analyses of species diversity have largely been limited to correlative studies based on the use of vegetation indices or derived land cover maps. A relatively new form of laser remote sensing (lidar) provides another means to acquire information on habitat heterogeneity. Here we examine the efficacy of lidar metrics of canopy structural diversity as predictors of bird species richness and abundance in the temperate forests of Maryland. Canopy height, topography and the vertical distribution of biomass were derived from lidar imagery of the Patuxent National Wildlife Refuge and compared to bird survey data collected at referenced grid locations. The vertical distribution of canopy elements was found to be the strongest predictor of both total richness and abundance. Species richness was predicted best when stratified by guilds dominated by forest, scrub, suburban and wetland species, with similar lidar variables selected as primary predictors across guilds. Generalized linear and additive models, as well as binary hierarchical regression trees produced similar results. The lidar metrics were consistently better predictors than traditional remotely sensed variables such as canopy cover, suggesting that lidar provides a valuable resource for biodiversity research applications. Recently available global lidar data sets permit extension of this analysis to broader spatial scales for which biodiversity observations exist.