An inventory of seasonal forest ponds on the Quabbin reservoir watershed, Massachusetts

Northeastern Naturalist, 1998 by Brooks, Robert T, Stone, Janice, Lyons, Paul

ABSTRACT - Seasonal forest ponds are unique habitats, and are the principal breeding habitat for some amphibians and invertebrates. An inventory of these habitats on the Quabbin Reservoir (Swift River) watershed (48,500 ha) in central Massachusetts identified and mapped 430 ponds. Two-thirds of the ponds (n = 286) were less than 0.05 ha in surface area and only 14 percent of the ponds (n = 60) were larger than 0.1 ha. The ponds were significantly clustered in spatial distribution. The surface area and spatial distribution of ponds suggest that they may exhibit attributes of biological islands. Pond-breeding fauna with limited dispersal abilities may occur as metapopulations. The actual effects of pond surface area and the spatial distribution of ponds on pond fauna have not been adequately studied. The ponds now occur in a predominantly forested landscape, but from 1750 until early in the 20th century, the landscape was largely agricultural with scattered woodlots or fragmented forests. The effects of land-use change on the composition, relative density, and reproductive success of pond fauna are unknown. The inventory was conducted to provide information to develop studies to investigate the effects of pond size, location, and forest history on pond fauna.

INTRODUCTION

Seasonal forest ponds, of both fall (autumnal) and spring (vernal) origin, are technically described as seasonally to semi-permanently flooded, scrub-shrub or forested palustrine wetlands (Cowardin et al. 1979) and are characterized as occurring in isolated, confined basins with no permanent hydrological connection to a stream or other permanent water body (Massachusetts Division of Fisheries and Wildlife 1988). The terminology, "seasonal forest pond," while awkward, best describes these habitats. According to Cowardin et al. (1979), the proper Water Regime Modifer for most ponds is the longer "seasonally flooded," rather than "temporarily flooded," denoting only brief periods during the growing season. Most ponds are of autumnal origin so "vernal" is inappropriate and can be misleading as their fall origin provides habitats for the fall-breeding marbled salamander (Ambystoma opacum). To avoid this dichotomy, we simply describe the ponds by where they occur, in forests, which avoids having to determine when each pond is typically reflooded. Finally, we are unaware of any accepted size standards that separate puddles from pools from ponds, so we chose to use ponds.

Seasonal forest ponds are important habitat for a diverse vertebrate and invertebrate fauna (Wilbur 1972, Wiggins et al. 1980, Williams 1987), several of which are listed as species of concern in some states in New England (DeGraaf and Rudis 1983). In Massachusetts, mole salamanders (Ambystoma spp.), wood frogs (Rana sylvatica Le Conte), and fairy shrimp (Anostraca, Eubranchipus spp.) are classified as obligate vernal pool species and used as indicators for the certification of vernal pools (Massachusetts Division of Fisheries and Wildlife 1988, Colburn 1991). These species are theorized to have evolved adaptations to the daily (temperature, 02 concentration) and annual (hydroperiod) stress of seasonal forest ponds because these habitats provide an important benefit as a refuge from fish predation of their eggs and larvae (Wiggins et al. 1980, Williams 1987). The ponds are unique biological habitats that deserve consideration in land-use and forest-management decisions.

Seasonal forest ponds occur as temporally discrete patches within a forest environment (Ebert and Balko 1982, 1987, Gibbs 1993). The spatial and temporal distributions of these ponds suggest that they may function as biological islands (Friday 1987, March and Bass 1995), at least for less mobile fauna or those with strong breeding-site fidelity, and that these species may be distributed as metapopulations (Blaustein and Margalit 1996, Dorn and Brandl 1991, Gill 1978, Wahlberg et al. 1996).

We report the results of an inventory of seasonal forest ponds in a representative watershed in central Massachusetts. The inventory was conducted as the first phase of a long-term study of the composition and reproductive success of seasonal forest pond fauna as affected by the spatial distribution of ponds, pond surface area, short- and long-term land-use history of pond catchments, and forest management practices in pond catchments.

FIELD-SITE DESCRIPTION

The watershed of the Quabbin Reservoir is located in central Massachusetts, USA. Twenty percent of the watershed is currently covered by the reservoir, created in 1939 by damming the Swift River. The reservoir and 55 percent of the upland watershed are administered and managed by the Metropolitan District Commission (MDC) as part of the water-supply system for the metropolitan Boston area.

The Quabbin watershed is approximately 48,500 ha in extent (O'Connor et al. 1995). It consists principally of glacially sculpted valleys between several gneiss domes (Gay and Yuretich 1996). The topography of the eastern portion of the watershed is irregular with moderate slopes, while the western portion is characterized by two well defined, steeply sloped ranges oriented north and south through the length of the watershed (O'Connor et al. 1995). Glacial till deposits constitute the surficial geology of the uplands and the valley bottoms and lowlands are generally filled with stratified glacial outwash deposits.