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INTRODUCTION

For the winter 2001 class of Restoration Ecology (EHUF 473), our group worked to restore three plots in the Union Bay Natural Area on the east side of the University of Washington campus.  Each plot will be restored to a different target community: Puget Sound prairie, Garry oak woodland, and seasonal freshwater wetland.  This report details the environmental conditions and the steps taken to restore each plot as well as recommendations for future management.

Group Members

Emily Griswold
Cortney Jensen
Suzie Karl
Jessica Raaum
Chris Regan

Site History

Human Activities
A brief history is beneficial in understanding the processes and conditions found at the site. Before the construction of the Hiram Chittenden Locks in 1916 the Union Bay Natural Area was known simply as Union Bay. With the completion of the Locks and the subsequent lowering of water level in Lake Washington, Union Bay became a mud flat and cattail marsh. In 1926, the city of Seattle began garbage disposal and fill operations in this area. During the 1950's Sanitary landfill methods were instituted, consisting of covering the garbage daily with a layer of earth. Following the discontinuation of dumping in '65 the site was capped and seeded with non-native grasses, clover and legumes (Ewing 2001, Duffield 2001). 

Following the final capping of the landfill, plans began for the development of "outdoor environmental laboratories and a center to study plant growth under varying stresses" (Union Bay Planning Committee 1994).  In 1972, recommendations were made to preserve the Union Bay shoreline in its natural condition for its educational, recreational, wildlife habitat, and aesthetic values.  In 1991, under the guidance of professor Kern Ewing, restoration projects began to be implemented on the site.  Over the past decade, numerous class, research, and volunteer projects have been undertaken on the site to restore native plant communities and combat weed infestations.

Soil
Late Pleistocene glaciers formed Lake Washington. The retreat of the Vashon Ice Flow deposited layers of gravel, sand and clay, which became the floor of Union Bay (Kruckeberg 1991).  Sediments and peat accumulated in the bay over the next millennium and a half, reaching up to 125 feet in some places (Ewing 2001, Dunn 1960).  The garbage dumped on the site reaches thickness between 15 and 50 feet (Jones and Jones 1975). Capping the garbage are stratified layers of gravel, compacted sand, and an impermeable layer of clay. The entire site is subsiding under the weight of the adjacent parking lot and decomposition of the buried refuse. However this subsidence is uneven, giving the site a rolling topography and leading to the formation of seasonal ponds in the low spots.

Vegetation
The original vegetation on the site was "a marshy emergent wetland" (Union Bay Planning Committee 1994).  Landfill operations covered almost the entire original extent of the wetland and created upland growing conditions.  The most common upland plant community in the Puget Sound area is coniferous forest dominated by Douglas-fir, western hemlock, and western red cedar (Franklin and Dyrness 1973).  The unusual soil conditions on the site have not been conducive to the normal succession of alder and big leaf maple to an eventual conifer climax.  The shallow, compacted layers of fill soil become waterlogged in the winter and extremely dry in the summer.  Cottonwoods, willows, and other native wetland plants thrive in the seasonal ponds, but pasture grasses dominate most of the upland areas.  Apple trees, hawthorn trees, and Himalayan blackberries have also successfully colonized upland areas.

South Puget Sound prairies are a rare native grass dominated system in lowland western Washington.  The unusual dominance of grasses at the Union Bay Natural Area has led land managers to decide to use this prairie community as the target for restoration.  Prairies are often associated with Garry oak woodlands in the South Puget Sound (Franklin and Dyrness 1973).  The wide tolerance range of Garry oaks to drought and winter flooding, has led to the decision to use oak woodlands as an additional target community in the Natural Area.

Project Goals

The goals of the 1994 Management Plan for the Union Bay Natural Area include:

1. maintaining and restoring biodiversity and ecosystem functions,
2. increasing wildlife habitat,
3. increasing the research and teaching on the site, and
4. increasing the area's service to the public (Union Bay Planning Committee 1994). 

These broad goals have been used to guide the restoration activities at the Natural Area and this restoration ecology class project.  Our group project has helped the Center for Urban Horticulture to achieve these goals.  We have increased habitat diversity by working on the restoration of three different plant communities: South Puget Sound prairie, Garry oak woodland, and seasonal freshwater wetland.  In each of these community restorations we have planted native plants to increase plant diversity and restore ecosystem functions.  We have also taken measures to remove and suppress invasive non-native plant species.  Furthermore, by setting up experiments in our plots, we are performing valuable research that will be used to inform future restoration projects on the site.

Because the Union Bay Natural Area is one of the few large open spaces in Seattle, increasing the area's service to the public is an important goal in the Management Plan.  By providing interpretive signs along Wahkiakum Lane, our group is enhancing the public's educational experience in the Natural Area.