Vernal pools are temporary wetlands that annually fill with water in the winter and early spring and then become dry when the weather turns warmer, although some pools may not completely evaporate in a wet summer. When pools periodically dry, predatory fish cannot survive, and this results in a protected breeding environment for all sorts of critters. Vernal pools are excellent habitats for many amphibians and invertebrates to complete part of their life cycles.
Creatures found at the Pardon Gray pool include wood frogs, spotted salamanders, marble salamanders, and fairy shrimp. These species require the protected waters of a vernal pool to survive. Other local species may use the vernal pool but can survive in nearby wetland habitats. These include spring peepers, gray tree frogs, green frogs, leopard frogs, pickerel frogs, red-spotted salamanders, several species of turtles, dragonflies, and whirligig beetle larvae. Vernal pools also supply drinking water for other wildlife. When in proximity to other pools, vernal pools enable amphibians and reptiles to pass from one wetland to another.
Vernal pools are reproductive hatcheries for terrestrial amphibians. Though most of us do not encounter these creatures as we trek through the woods, several thousand wood frogs use a moderate-sized vernal pool to breed before returning to the forest. The nutrients and energy from decaying vegetation on the pool floor nourish the frogs and salamanders of the nearby woods. The complexity of these food webs within the pools maintains a balance that enables a sufficient number of individuals of each species to survive and maintain the population in future years.
Each fall as leaves drop into the pool, bacteria and fungi begin the decaying process at the base of the food chain. Zooplankton feed on the bacteria and fungi, and a variety of insect larvae feed on the leaves, a process continued by adult insect forms, snails, and small crustaceans. The leaves also provide food for hatching tadpoles. These creatures in turn become food for predaceous diving beetles, dragon and damsel flies, and water scorpions. Salamander larvae join the list of pool carnivores. Joining the food web nearer the top of the chains are turtles, snakes, wading birds, and raccoon.
The presence of vernal pools at Pardon Gray Preserve is important to maintaining the biodiversity on both a local and global scale.
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]]>The 65-acre meadow alongside Main Road may be the most valuable wildlife habitat of Pardon Gray Preserve. Grasslands and open fields are disappearing in the Northeast due to the diminishing number of farms and expanding human development. This trend endangers the survival of eastern grassland nesting birds, along with the grasslands’ associated flora and fauna.
For thousands of years, open fields and scrublands were widespread across New England. Giovanni da Verrazano’s log from his 1524 exploration of Narragansett Bay described fields that “extend for 25 to 30 leagues; they are open and free of any obstacles or trees.” The 16th century landscape included a vast system of coastal salt marshes. Millions of beaver dams flooded woodlands to create “beaver meadows.” Native Americans burned woody vegetation surrounding their villages to create fields for farming, hunting, and wild berries. After European settlement, as much as two-thirds of New England forests were cleared for villages and farms, creating additional fields and meadows.
As development of Rhode Island expanded in the mid-1800s, this panorama of open fields began to disappear, and large grasslands are now scarce. Preserving the grassland at Pardon Gray Preserve is a primary goal of Tiverton Land Trust stewardship of the property. Two underlying conditions make meadows difficult to sustain. The first condition is natural: the default biome in New England is northern hardwood forest. Without beavers, haying, or pasturing, most land will eventually become forest.
The second condition is human-caused: the introduction of alien plant species that, in only a few years, can turn grassland into a thicket of plants foreign to our native ecosystems. Invasive species—because they didn’t evolve here—have few natural controls, and they disrupt the natural food web. The complex system of native plants and animals can break down and lead to disintegration of a natural community. The Tiverton Land Trust has worked hard to sustain the grassland habitat at Pardon Gray Preserve by planting native grasses and employing a late-season mowing regimen, after bird nesting.
An on-going experiment with a local beef farmer is also showing promising results. Pasturing livestock is a traditional activity that sustains grasslands and can coexist with ground nesting birds. However, normal grazing does little to stem the spread of alien plants because the animals avoid unfamiliar vegetation in favor of their usual forage. Restricting livestock to small grazing areas and using a daily “rotational” method causes grazing animals to be less selective. Each day the herd is moved to a different enclosure, and this creates a competitive urge to rush into the new area and graze aggressively, ahead of their herd mates. This “mob psychology” results in consumption of invasive plants, a more desirable control than herbicides. The hooved feet of grazing animals periodically trample the soil, keeping it from becoming compacted, and distribute nature’s best fertilizer.
Vast grasslands once stretched across the American Great Plains, with millions of acres of productive tall grass prairies. That ecosystem had its own rotational grazing—gigantic herds of American bison. While Pardon Gray’s operation is microscopic in comparison, the Tiverton Land Trust utilizes a similar natural method of sustaining its grassland, which supports local agriculture and helps preserve an important part of Tiverton’s farming history.
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