Authors: George and Elizabeth Churcher
As the clock of life ticks onward, we reflect on many things. Sometimes our thoughts are all encompassing, spanning years, while other times, they focus on the moment. On occasion, we rehearse the momentous milestones in our lives but, more often, we review the smaller, everyday happenings. When we think in terms of landscape, this same concept applies. As we undertake our day to day tasks at our home, we observe and consider the landscape immediately around us but when we drive along our beautiful country roads in the Tweed area, we become aware of the larger landscape — the forests, the fields and the wetlands. If we cast our eye to an even larger scale, we find ourselves examining the Great Lakes-St. Lawrence Forest biome. Yes, we live in the picturesque region which occupies the Great Lakes basin and extends along the St. Lawrence River eastward to the Gaspe.
Biomes are large life zones, characterized by distinctive plant and animal communities and are determined by geology, hydrology and the regional climate. There are four biomes in Ontario. In addition to the biome where we live, we marvel at the beauty and life-sustaining potential of the Boreal Forest which occupies the area directly north of our Great Lakes-St. Lawrence Forest. Still further north, the Northern Transition Zone reaches to the northern boundary of Ontario, then stretches further and eventually merges with the Tundra biome at the tree-line in the Canadian north. Turning in a more southerly direction, we encounter the Eastern Deciduous or Carolinian Forest of Southwestern Ontario. The Carolinian Forest is continuous with the Eastern Deciduous Forest biome of the Eastern United States. Unfortunately, most of the Carolinian Forest is gone from Ontario — only remnants remain.
The Great Lakes-St. Lawrence Forest, where we live, is characterized by a mix of deciduous and coniferous trees. As is true of all biomes, our broad region is composed of ecosystems: different forest subtypes, meadows, lakes, rivers, streams and wetlands such as swamps, bogs, fens and vernal pools. We can look at each of these as specific habitats for various species of plants and animals. — And, of course, within many of these, there are more refined habitat specifications: some fish, for example, prefer deeper water while others favour the shallows, amid vegetation.
At the local level, ecosystems are essential to the maintenance of the diversity of life. They can be very small, like the community of animals living under a rotting log on the forest floor, the life depending on an aging snag or the organisms surviving in a pool of water.
Until more recently, one of the least appreciated ecosystems has been the Vernal Pool. Vernal pools are temporary bodies of water found in lowland areas in woodlands. They result largely from snowmelt and seasonal flooding and have no inlets or outlets — no streams feed them. Melting snow or an abundance of Spring and early Summer rain can result in the water table reaching the surface where these pools are formed, so the water in them is sitting on top of saturated soil. Even though Vernal Pools, sometimes existing into mid-summer, gradually dry up, they, just like all other ecosystems, are essential to the lives of many organisms.
The impetus for the scientific study of Vernal Pools happened in the 1980s when it was realized that amphibian populations were in decline worldwide. Because of their vital importance to amphibian populations, Vernal Pools came into sharp focus.
In our local area, Vernal Pools provide breeding habitat for such frog species as Northern Chorus Frogs, Spring Peepers, Gray Tree Frogs and Wood Frogs. Mole salamanders, who live most of their lives underground, migrate to Vernal Pools on warm, rainy Spring nights to mate and lay their eggs, just as the frogs and American Toads do. The group of Mole salamanders includes such species as the Spotted Salamander (pictured) and the Blue-Spotted Salamander. Vernal Pools have a great advantage for the reproduction of amphibians: they contain no fish, as they are not stream-fed, so the eggs and larvae of frogs and salamanders are safe from fish predators.
Other inhabitants who live and breed in Vernal Pools include various water beetles, caddisflies and dragonflies. Fairy Shrimp also take advantage of the temporary water supply. Their eggs, which were laid last year, hatch and the shrimp, who lead brief, ephemeral lives, mate and lay a new batch of eggs before the pools dry up in the summer.
Vernal Pools are beneficial to more than the animals. The moisture that they contribute to the soil creates favourable conditions for many plants such as Red Maple, Buttonbush, Cardinal Flower, willows, alders, Jack-in-the-Pulpit, various ferns and many more. As you explore our area in the next few weeks, checking out the Vernal Pools, look closely at their fringes, especially when they are situated at the edges of woodlands. It is quite possible that you will discover plant communities made up of many of the plant species mentioned here.
Vernal pools make vital contributions to the biodiversity of our area and throughout northeastern North America — contributions which merge seamlessly with those of all the other ecosystems in the Great Lakes-St. Lawrence Forest biome. As you drive along the back roads in the Tweed area throughout this season of awakenings, take time to appreciate every habitat, even the pools that are with us for such a short period of time. Celebrate with us the life that they support through their brief presence in our midst.
Previously published in the Tweed News on April 12, 2017.