Regeneration of woody plant species within riparian zones of headwater streams whose watersheds vary by dominant land cover

Abstract

Riparian vegetation, particularly along headwater streams, is important in controlling nutrient and pollutant runoff from terrestrial ecosystems, in maintaining stream bank stability, and in controlling in-stream temperatures. Previous research has indicated that riparian zones containing a high abundance and diversity of native plant species protect the stream ecosystem most effectively. Therefore, regeneration of native and diverse plant communities is vital for the prolonged protection of stream environments. This study was conducted to evaluate the potential impacts that different land covers have on regenerating woody plant communities along headwater streams in two adjacent watersheds of Hunterdon County, New Jersey. Twelve headwater streams and their subwatersheds were selected based on the predominant land covers within the subwatershed. The subwatersheds were divided into three groups (land-cover classes) to reflect a disturbance gradient. Agricultural and urban dominated (Ag_Urban) subwatersheds represented the most disturbed, followed by agriculturally dominated forest/wetland (Ag_Forest_Wetland), and forest/wetland dominated subwatersheds (Forest_Wetland) represented the least disturbed. Overall, there were no significant differences between the seedling communities' species richness, density, and diversity based on the dominant land cover classes. Species-specific responses were more informative compared to community level measures and tended to vary based on the land cover category. There were greater similarities between seedling and mature tree species dominance in the Forest_Wetland class compared to the other two classes where there was greater similarity in the dominance of the seedling and mature components of several shrub species. This and similar studies contribute to our understanding of how riparian vegetation communities potentially react to a diverse landscape.