IMPACT OF PALEO-HYDROLOGY ON THE DISTRIBUTIONS OF NATURAL COMMUNITIES AT A BIOLOGICALLY DIVERSE NATURAL AREA IN NORTHEASTERN INDIANA

The upper Wabash River Valley and some of its tributaries were repeatedly scoured by large, landscape-altering outbursts of meltwater during deglaciation, carving what some early geologists likened to a “miniature scabland” into the exhumed carbonate bedrock. Today, the region is better known as the “Wabash Klintar”. World renowned for its exposures of Silurian pinnacle reefs, the region also features deep gorges, hanging valleys, many waterfalls, exhumed bedrock valleys and paleokarst, and a variety of scoured bedrock and glacial surfaces at different elevations—all indicative of a disequilibrium landscape that continues to be affected by a torrid pace of stream incision. Not surprisingly, natural areas in the region are characterized by great biological diversity, including a large number of calciphiles, among them several regionally rare and disjunct plants and community types.

Kokiwanee Nature Preserve is emblematic of the relationship between drainage history and biological diversity in the upper Wabash Valley region. At just 56 ha, this compact preserve perched on the side of the Salamonie River gorge hosts close to 500 plant species—nearly a quarter of the entire number known in Indiana—within a remarkably wide range of geologically-defined habitats that result directly or indirectly from past and present drainage events and groundwater processes. Among these are mesic till plain forests on undissected glaciated uplands; poorly-drained flatwoods associated with abandoned high-level glacial drainages; diversified cove forests and riparian wetlands in modern ravines; dry-mesic calcareous forests on rich limestone bluffs (a disjunct community type from the Ohio River); calcareous fens produced by groundwater discharging from an exhumed, gravel-filled buried valley; seepage swamps and marshes fed by upwelling of old, mineralized groundwater from bedrock aquifers; hanging fens and petrified moss gardens associated with calcareous bluff seepage; xeric bluff-top limestone glades; and several types of terrace forests that range from dry to hydric. The concentration of diverse, geologically-driven micro-environments and the legacy of human land use create pronounced ecotones between the various community types, making them sometimes difficult to characterize.