Short‐Term Responses of Wetland Vegetation After Liming of an Adirondack Watershed

Abstract

Watershed liming has been suggested as a long—term mitigation strategy for lake acidity, particularly in areas subject to high levels of acidic deposition.However, virtually no information has been available on the impacts of liming on wetland vegetation. In 1989, 1100 Mg of limestone (83.5% CaCO3) were aerially applied to 48% (100 ha) of the Woods Lake watershed in the west—central Adirondack region of New York as part of the first comprehensive watershed liming study in North America. We inventoried wetland vegetation in 1.0—m2 plots before liming and during the subsequent 2 yr. Within this period liming influenced the cover, frequency, or importance values of only 6 of 64 wetland taxa. The cover of Sphagnum spp. and of the cespitose sedge Carex interior decreased in control relative to limed plots, and cover of the rhizomatous sedge Cladium mariscoides increased nearly threefold in limed areas. These two sedges, which are relatively tall, are characteristic of more calcareous habitats. Cover of the grass Muhlenbergia uniflora, cover and importance value of the sundew Drosera intermedia, and frequency of the forb Hypericum canadense were adversely affected or inhibited by lime. It is unclear whether liming directly inhibited the growth of these three small—statured species, or whether the adverse effects of lime were mediated through shifts in competitive interactions with other species. The limited responses that we observed to liming, along with changes that occurred in control plots over the study period, may indicate that in the short term watershed liming was no more of a perturbation than the environmental factors responsible for natural annual variation in wetland communities.