EFFECTS OF DRAINAGE DITCHES ON VEGETATION PATTERNS IN ABANDONED AGRICULTURAL PEATLANDS IN CENTRAL NEW-YORK

Drainage ditches and ground-water gradients in abandoned agricultural sapric peatlands (mucklands) produce distinctive vegetation patterns. Ditches in abandoned mucklands were ineffective in creating ground-wat er depression in adjacent soil, while ditches in a newly-cleared muckl and were effective in doing so. Upon abandonment, drainage ditches are subject to bank erosion and sedimentation. Coupled with years of soil subsidence and an altered hydrologic regime, ditches lose effectivene ss in draining and function merely as small-scale topographic depressi ons, providing linear zones of seasonally high water levels. Species a re distributed on abandoned mucklands in association with soil moistur e conditions induced by topographic variation at both small (i.e., dit ches) and larger (i.e., site-wide) spatial scales. Vegetation that is usually restricted to moist or saturated soils had greater cover close r to or within drainage ditches or in other topographically low areas, while species with low fidelity to saturated soil dominated the remai ning drier areas. Some shrub species had slightly greater stem densiti es either within or immediately adjacent to ditches, resulting in a '' parallel'' distribution (i.e., illustrating ditch-fidelity). Species h aving higher affinity to lower soil moisture conditions, such as quaki ng aspen (Populus tremuloides), showed significantly greater stem dens ity in areas farther away from ditches. Ground-water levels are of pri mary importance in affecting distribution patterns on naturally revege tating, abandoned agricultural mucklands. The accuracy of the wetland indicator status for woody and herbaceous species encountered on these abandoned mucklands is supported quantitatively by direct gradient an alysis. The functioning of existing drainage ditch systems should be a ssessed prior to any mitigation or restoration activities.