s2ary
09-19-2007, 09:35 PM
3) Invasive Species Control
Scattered around the two properties are many different species of invasive plants. The most noteworthy species are Common Reed Phragmites australis, Purple Loostrife Lythrum salicaria, and Japanese Knotweed Polygonum cuspidatum. Most of the lesser known species are early colonizing shrub and lower canopy woody species and the final species is Japanese Black Pine Pinus thunbergii. Our control strategy can be summed up in three words, ‘Shade Them Out’. With the exception of the Japanese Black Pine all of the other invasive species are early colonizing species that compete poorly in mature forest settings.
In the proposed wetlands adjacent to the PISA Watershed all of the invasive plant species will be removed by excavating the area and composting their removed soils on site. During the establishment period of the riparian corridor these areas will be aggressively managed to control any invasive species reestablishment. As the area matures and the red maple swamp vegetation closes the upper layers of the canopy the threat of reestablishment from invasive species will be low.
The north watershed has an isolated Phragmites stand. This stand will be planted with woody wetland species and the height of the existing Phragmites will be maintained just above that of the establishing woody species. This manner of Phragmites height management stimulates a competitive response in the woody species encouraging them to grow straight and fast in order to occupy a space in the canopy.
The remaining upland areas adjacent to the wetland resources will be slowly managed over a period of years. At the end of this management period the site will have been taken by the hand and led from a late successional field or early New England Forest habitats into a young New England Forest with a closed canopy. As foresters, we feel strongly that other more aggressive woody invasive management techniques would seem to invite more invasives to the site at a future date. We prefer working with succession by utilizing the existing plant community as the fostering or nursery environment necessary to establish select bare root forest species. As the bare root forest species become established, the invasives are then selectively reduced. This process takes time, site succession works on geological time, but once the process is complete, the site will be stable and protected from future encroachments.
4) Integrated Low Impact Design Considerations
Another unique aspect of this project has been the ability to integrate the riparian corridor restoration needs with the site plan design. This has allowed the project to utilize every conceivable advantage to ensure the restoration’s success. These considerations come in two forms.
The abatement of thermal retention
As of lately there is a great deal of emphasis on global warming and thermal retention in the landscape. We believe that both concerns are real and in a small way related. Global warming is a complex issue that is way beyond the scope of this project, but thermal retention is not. All one needs to do is walk off of a parking lot and into a small group of trees to feel the remarkable difference in temperature, it is hard not to relate this to a more global scale.
In the site design plan we maximized the planting areas within the paved surfaces to shade the site as much as possible. We also modified the storm water treatment system to include dense plantings of red maples that will shade the contained water to maintain a cooler temperature during the infiltration process.
Treatment, Infiltration, and Utilization of Storm Water
Our storm water plan is based on treatment and utilization. Our plan will undergo the same treatment requirements as a standardized storm water plan and then we will use this water to establish and maintain an aquifer under and adjacent to the parking areas. The aquifer is not necessary for our restoration success, but it will aid in cooling and stabilizing the stream flows from the north sub watershed and help compensate for the loss of groundwater flows from the impervious areas of the watershed.
The water leaving the parking areas will enter living swale layouts where deep organic layers will promote percolation, quickly trapping sediments and heavy metals. After receiving treatment under a dense canopy the water will proceed into a system of underground infiltrators. When the filtration units are at maximum capacity the overflow water will be diverted to a modified retention basin. While the water is percolating through the underground infiltrators, the water temperature will be stabilized at approximately 55 degrees. The water will migrate out from the infiltrators and be further polished by filtration through a porous base. As the new groundwater works its way under the parking area it will enhance the existing groundwater supply stabilizing the aquifer at a larger capacity than the capacity prior to the project. Finally the clean water migrating from the parking area will discharge into the riparian corridor stabilizing both the flows and temperature of the stream flows.
As mentioned above, at times there will be flows in excess of the capacities of the infiltration system. These overflows will be directed to a modified retention basin. In the retention basin the water be held and allowed to infiltrate through deep organic soils into a porous base while being shaded by a dense red maple canopy. These waters will discharge as groundwater providing a stable hydrology for the lower riparian corridor region.
Scattered around the two properties are many different species of invasive plants. The most noteworthy species are Common Reed Phragmites australis, Purple Loostrife Lythrum salicaria, and Japanese Knotweed Polygonum cuspidatum. Most of the lesser known species are early colonizing shrub and lower canopy woody species and the final species is Japanese Black Pine Pinus thunbergii. Our control strategy can be summed up in three words, ‘Shade Them Out’. With the exception of the Japanese Black Pine all of the other invasive species are early colonizing species that compete poorly in mature forest settings.
In the proposed wetlands adjacent to the PISA Watershed all of the invasive plant species will be removed by excavating the area and composting their removed soils on site. During the establishment period of the riparian corridor these areas will be aggressively managed to control any invasive species reestablishment. As the area matures and the red maple swamp vegetation closes the upper layers of the canopy the threat of reestablishment from invasive species will be low.
The north watershed has an isolated Phragmites stand. This stand will be planted with woody wetland species and the height of the existing Phragmites will be maintained just above that of the establishing woody species. This manner of Phragmites height management stimulates a competitive response in the woody species encouraging them to grow straight and fast in order to occupy a space in the canopy.
The remaining upland areas adjacent to the wetland resources will be slowly managed over a period of years. At the end of this management period the site will have been taken by the hand and led from a late successional field or early New England Forest habitats into a young New England Forest with a closed canopy. As foresters, we feel strongly that other more aggressive woody invasive management techniques would seem to invite more invasives to the site at a future date. We prefer working with succession by utilizing the existing plant community as the fostering or nursery environment necessary to establish select bare root forest species. As the bare root forest species become established, the invasives are then selectively reduced. This process takes time, site succession works on geological time, but once the process is complete, the site will be stable and protected from future encroachments.
4) Integrated Low Impact Design Considerations
Another unique aspect of this project has been the ability to integrate the riparian corridor restoration needs with the site plan design. This has allowed the project to utilize every conceivable advantage to ensure the restoration’s success. These considerations come in two forms.
The abatement of thermal retention
As of lately there is a great deal of emphasis on global warming and thermal retention in the landscape. We believe that both concerns are real and in a small way related. Global warming is a complex issue that is way beyond the scope of this project, but thermal retention is not. All one needs to do is walk off of a parking lot and into a small group of trees to feel the remarkable difference in temperature, it is hard not to relate this to a more global scale.
In the site design plan we maximized the planting areas within the paved surfaces to shade the site as much as possible. We also modified the storm water treatment system to include dense plantings of red maples that will shade the contained water to maintain a cooler temperature during the infiltration process.
Treatment, Infiltration, and Utilization of Storm Water
Our storm water plan is based on treatment and utilization. Our plan will undergo the same treatment requirements as a standardized storm water plan and then we will use this water to establish and maintain an aquifer under and adjacent to the parking areas. The aquifer is not necessary for our restoration success, but it will aid in cooling and stabilizing the stream flows from the north sub watershed and help compensate for the loss of groundwater flows from the impervious areas of the watershed.
The water leaving the parking areas will enter living swale layouts where deep organic layers will promote percolation, quickly trapping sediments and heavy metals. After receiving treatment under a dense canopy the water will proceed into a system of underground infiltrators. When the filtration units are at maximum capacity the overflow water will be diverted to a modified retention basin. While the water is percolating through the underground infiltrators, the water temperature will be stabilized at approximately 55 degrees. The water will migrate out from the infiltrators and be further polished by filtration through a porous base. As the new groundwater works its way under the parking area it will enhance the existing groundwater supply stabilizing the aquifer at a larger capacity than the capacity prior to the project. Finally the clean water migrating from the parking area will discharge into the riparian corridor stabilizing both the flows and temperature of the stream flows.
As mentioned above, at times there will be flows in excess of the capacities of the infiltration system. These overflows will be directed to a modified retention basin. In the retention basin the water be held and allowed to infiltrate through deep organic soils into a porous base while being shaded by a dense red maple canopy. These waters will discharge as groundwater providing a stable hydrology for the lower riparian corridor region.