Ghost of land-use past in the context of current land cover: evidence from salamander communities in streams of Blue Ridge and Piedmont ecoregions

Abstract

The Blue Ridge and Piedmont of the southeastern United States are rich in biodiversity and have undergone centuries of extensive deforestation and subsequent urbanization resulting in geomorphic landscape changes. To investigate the impacts of past and present land uses on stream salamander communities across both ecoregions, we surveyed streams associated with different land uses at the riparian zone and watershed. Using the USGS land-cover data set (2006) and aerial photographs (1940), we assessed the current and historical percent land cover (urban, agriculture, and forests) at local and landscape scales for each sampling site. Using percent land cover as predictors and diversity indices (species richness, Simpson’s index, and relative abundance) as response variables, we developed a stepwise multiple regression model and a redundancy analysis. Both analyses indicated the negative impacts of historical land uses, particularly row-crop agriculture, on stream salamander diversity and community structure rendering streams unsuitable for all but the most tolerant species. Legacy effects were prominent in the Piedmont where protected areas with agricultural history were species-deprived (70% decline) compared with stream habitats that had sustained a continuous forest cover through time. Our findings suggested that landscape processes resulting in historical forest cover loss may persist over 50 years during forest recovery.