Forest Vegetation and Soil Patterns Across Glade-forest Ecotones in the Knobs Region of Northeastern Kentucky, USA

Abstract

The Crooked Creek Barrens Preserve in the northeastern Knobs region of Kentucky contains an aggregation of species-rich grass and forb-dominated glade openings surrounded by secondary forest. Encroachment of woody species and invasion by non-native species threaten the rare forbs and sedges of the glades. The locations of these plant assemblages are commonly known to correspond to the unique properties of their underlying soils, yet few studies consider how soil factors may influence habitat conservation or restoration. This study describes vegetation and soil properties across the glade-edge-forest transition of three individual glade openings. Juniperus virginiana was the most abundant woody species within the glade openings. Juniperus virginana, Quercus stellata, Fraxinus americana and Cercis canadensis co-dominated the edge-forest boundary. Glade surface soils had dramatically higher pH (2 units) and lower extractable soil P (50% less) than forest soils. Also, total soil N content and net mineralization rates were significantly lower in glades than in forest or edge soils. The highly erodable nature of alkaline shale sediments appears to have contributed to the current location and extent of the glade openings. These findings suggest that management efforts to enhance rare plant habitat by expanding the glade openings should be accompanied by monitoring of soil changes following clearing. Further study should assess whether glade species of conservation concern are restricted to the nutrient-poor alkaline soils within extant glade openings or if they readily colonize the more nutrient-rich habitat of the cleared edge.