Ecosystem classification and succession of northeast Indiana
A multi-factor ecosystem classification of the Bluffton Till Plain has been created to characterize and organize ecosystem units within the Framework for Hierarchical Ecosystem Classification, which is used in forests throughout the eastern United States. Through examination of relationships between potential natural vegetation, soil, and landform characteristics, the Bluffton Till Plain has been organized into 3 ecological land-types (ELT) and 12 ecological land-type phases (ELTP). Nine herbaceous plant communities were described in the region, and they have been used to indicate site characteristics distinctive of each ELTP. Plant communities were found to be strongly related to landform topography, soil horizon depths, and soil texture through a process that identified communities with cluster analysis and related them to site characteristics with Classification and Regression Tree analysis. Ecological land-types were found to differ in their successional trends, with the greatest difference between ELTPs in mesic upland sites and wet-depressional sites. Upland sites follow the acknowledged trend of oak-hickory communities shifting to a beech-maple community dominated by Acer saccharum; while upland depressional sites follow trends that indicate Acer saccharinum dominance through time. Additional research concerning the effect of fragmentation on woody species' successional trends shows that sites located in small forests (<10 ha) do not differ significantly from those located in large forests (>10 ha). This project illustrates the importance of site characteristics and disturbance history on plant species community composition, and the ability to use the relationships between sites and vegetation in constructing an ecosystem classification.