Using Floristic Analysis and Dendrochronology to Plan Ecological Restoration within a Forest-Prairie Ecotone

摘要

The limestone bluffs of the central Mississippi River Valley represent a significant portion of the remaining intermingled xeric hill prairie-savanna-woodland systems of the Midwest where different cover types may co-occur at very fine scales. Efforts to restore these landscapes would benefit from a data-driven tool to delineate existing vegetation cover characteristics and reconcile these with desired management outcomes on a spatially explicit basis. This study employed hierarchical cluster analysis and nonmetric multidimensional scaling in combination with indicator species analysis and dendrochronological methods to examine the structure, composition, and temporal community patterns of the forest-prairie gradient in the Mississippi River Bluffs of Jersey County, Illinois. Four distinct community types were identified on the gradient: (1) a woodland community dominated by Juniperus virginiana, Carya glabra, Quercus stellata, and Lonicera maackh; (2) open oak woodland with high exposed soil and overstory of Acer saccharum, Q. velutina, and Q. muehlenbergii; (3) a hill prairie community with grass coverage as the sole indicator; and (4) a transitioning community with 14 significant indicators and a trajectory advancing toward mesophytic forest composition. These data, within context with stem age, historical documents, and drought data, reveal the role of historical disturbances in temporal patterns of forest-prairie dynamics and provide a resolution in greater detail than previous studies of forest and nonnative invasive shrub encroachment. Pairing management activities to stand conditions, as informed by understanding drivers of ecosystem change, provides continuity with historical disturbance regimes and an objective basis for restoration activities and targets.