Rick Van de Poll
Department of Environmental Studies
Soil temperature at 12.5, 25, 37.5, and 50 centimeters depth, bud burst in shrub layer plants, and free soil water depth was monitored in wetland, transitional and upland study plots between February 7 and may 29, 1997. The collected compared to the definitions of growing season promulgated by the 1987 and 1989 Federal Wetland Delineation Manuals, and the Proposed 1991 Revisions to the 1989 Manual. Monitored biotic activity was most strongly correlated to soil temperatures at 50 centimeters depth. Significant biotic activity in monitored shrubs was observed significantly before soil temperatures reached Biologic Zero. Sharp increases in biotic activity were observed after April 20, seventeen days before the 1987 manual's estimated start of growing season, ten days before the 1989 manual's estimate, and five days after the 1991 revision's estimate.