STUDYING TRENDS IN BIOLOGICAL DIVERSITY IN ABANDONED AGRICULTURAL FIELDS: A GEOECOLOGICAL APPROACH

Geomorphological, Pedological, and Lithological controls on plant community composition and biodiversity are observable in many settings. The effect of Geomorphology is especially noticeable in mountainous regions and when comparing plant communities in different landscape positions, but also exists for small changes in slope angle or aspect. Soil and lithologic control on vegetation is readily noticeable in regions with large mineralogical and textural differences in the regolith or bedrock, but also exists where geologic variability is more subtle. To varying degrees, these geologic controls combine with climate and biological processes to explain the distribution of plant types and biodiversity in myriad geologic settings. Abandoned agricultural fields undergoing succession in similar climate, with different geological characteristics, provide ideal environments for studying the effects of geology on plant community establishment and biodiversity. As part of an inter-disciplinary project, the variability of soil moisture, pH, slope angle and aspect, available light, and soil nitrogen content values were determined for two abandoned agricultural fields in Southern Indiana. The variation in these properties relates to variation in the plant communities and biodiversity within and between the fields. Within an old field overlying limestone, certain areas are more variable in plant species richness than others. In contrast, within an old field of a highly dissected landscape with siltstone bedrock, the variability in biodiversity and in plant communities is more subtle. For each of these old fields, environmental factors are ranked according to their influence on plant biodiversity and community composition, and the spatial scales at which these factors operate are determined. Geologic settings have quantifiable impacts on these ecological relationships.