COMPARATIVE ANALYSIS OF URBAN AND RURAL FOREST FRAGMENT STRUCTURE AND DIVERSITY IN NORTHEASTERN INDIANA

摘要

Although it was once continuously forested, the land cover in northeastern Indiana is now dominated by agriculture, and sparsely occurring forest fragments now constitute only approximately 8 of the land cover. A majority of these forest fragments are privately owned and have a history of some form of active forest management. We conducted a systematic ecological survey of understory, midstory, and overstory plant species in three forests that have differing protection and management histories to compare the effects of these different histories. Historical aerial images of each forest were compared to gauge the canopy structure and to clarify the management history for the forests. The percentage of canopy cover and the floristic quality indices (FQI) each followed expected trends, whereby the highest FQI value and percentage of canopy cover occurred in the forest with the longest history of preservation. Lower values of species richness for the understory, midstory, and overstory strata, respectively, were found in the forest that has a history of overstory management and for which there is no defined protection status. The understory species were each generally limited to one of the forests, whereas the species composition of the midstory and overstory strata were much more similar among the three forests. Measurements of forest basal area and percentage of canopy cover provide some explanation of the distribution of understory and midstory species in nonmetric multidimensional scaling ordination plots. The amount of forest protection, measured by the time since disturbance and the percentage of canopy closure, influenced the richness of the understory and the FQI of a given plot. Furthermore, the location of a forest was an important factorin the relative occurrence of non-native species, the most rural forest having no non-native species.