Ecological planning beyond the birdbath    Before you start     Urban Wetlands    Marshes
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Wetland restoration

Swamps

Swamps are some of the most threatened wetlands. Retaining existing swamps or rehabilitating those that have ben drained are top priorities in wetland conservation. The hard wood swamp is the hardest to recreate. We rarely have time for a community to develop from seed. We have limited experience with predicting hydroperiod, water depth, substrate and nutrient cycling. Of course all of these are difficult to monitor due to the long time it takes forested wetlands to mature. Species in forested wetlands also have narrower tolerances for flooding and hydroperiod.

If possible, plant early successional species such as willow or poplar which create the microenvironment and soil conditions suitable for the invasion of swamp trees (ie red maple). Natural regeneration can only occur if there is a recent seed bank in the soil or a nearby source of swamp trees and if hydric conditions for seed germination have been recreated. If avail able, soil sections or topsoil from nearby swamp species destined to be destroyed may provide propagules for establishing an understory of swamp species. A number of species can be planted if natural regeneration seems promising.

There is little data on natural regeneration, the second phase of forest restoration. For this reason it is appropriate to focus on preservation and rehabilitation where conditions are right. The arrival of water at the time when trees are growing or seeds germinating is as important for swamps as is the length of time water stays (hydroperiod), and frequency and depth of inundation. One of the major problems is in controlling invasive plants and exotics until trees and shrubs become established. It may be necessary to plant ferns and forest perennials to shelter tree and shrub seedlings, as many weed and grass species outcompete tree saplings for nutrients, water and light in new sites.

Shallow rooted trees are prone to windfall. It is important that roots of swamp species penetrate compacted soils to reach the subsurface water table. In saturated soils water replaces the oxygen that would normally be found in soil. Tree roots are shallow in order to maximize oxygen uptake from the shallow zone of unsaturated or oxygenated soil perched above the water table. If soils are saturated during the growing season some species may die if they cannot survive the low oxygen levels. If ground water flow is disrupted or the water table drops, tree roots cannot reach water. The stress may result in death of smaller rooted trees, or even the forest itself. Nutrient depletion in the shallow soils may further restrict tree growth.

When linking a forested swamp it may be necessary to create an overstory which contributes to the microenvironment for a succession of understory species. Species with heavy seeds, need to be planted as they do not colonize new or isolated sites well.