cktimes.ca Archives for Ecowrappin'
Ecowrappin'
It's the Pits
Tuesday, December 24, 2002
Restoration work is very important to our environment, ecosystems, habitats and flora and fauna. Planting trees has always been a popular restoration activity for environmental groups, nature clubs, schools and some government agencies. Planting a tree is a good thing and we should all appreciate the efforts put forth by groups and individuals to plant trees.Tree plantations are found throughout our local area and range in size from just a half acre corner on a farm to many acres on a larger scale. Typically a plantation of any decent size is planted by a mechanical planter sowing rows of seedlings. By far the most common species planted are silver maples (acer saccharinum) and green ashes (fraxinus pennsylvanica), but sometimes other species are included such as black walnut (juglans nigra) and red oak (quercus rubra). The more recent trend is to plant only native species but in the past some non-natives were planted also including black locust (robinia pseudoacacia). Including these non-natives is now considered unacceptable in our efforts to restore natural forest habitat.
Because most plantation sites are abandoned or retired farmland, which has been leveled by many years of plowing and cultivation, the sites are usually very flat and easily accommodate the tractor and planter. Although common, flat plantations of silver maples and green ashes are not considered to be very effective forest restorations. They lack the floral diversity of a natural forest and the flat surface creates an unnatural hydrology situation. When it rains, the water spreads over the soil evenly and so the entire site is equally moist and then the entire site dries out at the same rate until it is all dry again. Many plants cannot grow under such conditions and that's why the silver maples and green ashes are planted. These two species can grow in a variety of soil conditions but even so, these plantations do not make good forests.
So, how do we do a better job of forest restoration? How do we restore a site to accommodate the vast diversity of species of flora and fauna that is found in a natural forest?
A new forest restoration strategy has been developed and is now being implemented by the Nature Conservancy of Canada at Clear Creek Forest. The concept was developed by John Ambrose and Gerry Waldren and represents a very impressive effort to emulate Mother Nature and her old growth forests.
A close inspection of the features of an old growth forest, such as its topography and hydrology have resulted in the "pits and mounds" concept for forest restoration. "Pits and mounds" describes the naturally undulating surface of the old growth forest. It is the result of tall, mature trees being blown over by strong winds. When a tree blows over, the roots rip out of the ground on one side taking a pile of soil with them, which creates a pit. The soil taken with the roots creates a pile or mound beside the pit, especially after the roots have rotted away. Obviously, this takes a very long time (centuries) for a forest to naturally develop the pit and mound, old growth feature. The result is that the pits hold rainwater and the mounds offer a dryer site. Moisture is retained over a longer period of time because of the bowl-like pits. The surrounding soil, including the mounds, wicks moisture from the water-filled pits, thereby allowing a greater diversity of plants to find the perfect site to germinate. Species that require a wetter site grow at the edge of the pit and species that like a dryer location grow on the mounds. This is one of the reasons our natural forests are so diverse with up to 30 or 40 species of trees and numerous species of herbs and shrubs. The diversity of flora results in a diversity of wildlife and a complex old growth ecosystem is the result.
At Clear Creek, the NCC has created pits and mounds at three sites, an 11 acre field, a 30 acre field and this year, a 40 acre field. A large payloader with a bulldozer blade is used to make the pits and mounds. It's an impressive site looking somewhat like a war zone with all the big holes and piles of dirt. The pits are one to two feet deep and the mounds are two to three feet high. When the first field was completed in 2000 (the eleven acre field), it rained that night. The next day the pits were all filled with water and a new forest restoration technique was born in Canada. We learned later that a similar concept was being tried in the Carolinas, but Clear Creek was the first site in Canada.
The first night after that rain, just 24 hours later, the water-filled pits were full of frogs. Mathis Natvik was there to hear the incredible chorus of frog song. Mathis has also witnessed deer, turkeys and other wildlife visiting the fields of pits and mounds.
A variety of trees and shrubs have been planted in these fields and it is believed that a greater variety of plants will expand into these fields from the surrounding forest. The result is a diverse forest habitat, probably centuries ahead of its time. Conservationists will be watching closely as these pit and mound fields develop and grow into new forests.
The NCC should be congratulated for using the innovative forest restoration technique, the "Pits and Mounds" at Clear Creek Forest.
