DESIGN AT THE EDGE: ART AND SCIENCE FOR LAKESHORE REVEGETATION
Kathryn McFadden
INTRODUCTION
Removal of wetland fringe vegetation along lakeshores has had a major impact on
the ecological health of lakes in northern Minnesota and elsewhere. Devegetation
during development and the subsequent addition of fertilized and closely mowed
turfgrass lawns to the water's edge has resulted in land losses through
shoreline erosion, increased sediment and nutrient loading into the lakes. Lake
water quality suffers as water transparency decreases, algal blooms are more
frequent due to higher nutrient levels, and fish and wildlife habitat suffers.
As boat traffic and use of the more recently introduced jet ski increases, the
shoreline is at even more risk of erosion as wave impacts exacerbate shoreline
vegetation losses and make reestablishment of the littoral wetland fringe even
more difficult. Change over time in shoreline soil composition from the import
of sand for artificial beaches complicates restoration efforts.
These clear
consequences of lakeshore disturbance point to the necessity of working toward
revegetation of these areas, both on the site scale in which the quality of
vegetated shoreland landscapes can be demonstrated, and at the landscape scale.
Procedures to successfully revegetate such areas have been slow to develop.
Previous work on shoreline revegetation has used various structures, primarily
floating booms or biodegrading mats or rolls that function to reduce wave impact
in the restoration area. These procedures have been successful, but are of an
expense outside the realm of most homeowners, lake associations or even local
governments and, as such, are not practicable over large or small areas of
privately held property.
Cultural factors also influence acceptance and success
of lakeshore revegetation efforts. A strong ethic of "neatness", defined
culturally as mown turfgrass, transfers from the suburbs to lake property. In
this tradition, "natural" or undisturbed vegetation is considered weedy. In a
similar vein, the presence of the sandy beach mentioned above is another part of
the stereotypically "proper" presentation of these properties as well as a
desired amenity on any lake, whether or not this would naturally occur. "Mucky"
lake bottoms and the presence of vegetation in the water are undesirable and a
deterrent to swimming, a primary land use on vacation property. These long
standing cultural values have been resistant to change, not necessarily because
of the resistance of these landowners intrinsically, but simply because the
ecological information related to these issues has not been generally understood
by the public.
The goals of the Big Sandy Lake Shoreland Revegetation Project
are be as follows. First, that this project will add to available information
on shoreland revegetation and contribute to increased success in this area.
Second, we hope to develop methods to minimize wave impact and erosion on newly
revegetated sites and thereby increase plant survival, in ways that are
accessible to the average landowner. This should increase participation in
revegetation of private lakeshores. Third, to increase public awareness of the
consequences of devegetation during development and demonstrate revegetation as
an aesthetically pleasing alternative to the misplaced turf lawn. We would like
to demonstrate the landscape value of an undisturbed, "selectively disturbed" or
"edited", natural site, making the point that mature birch and pine cannot be
quickly "restored".
BIG SANDY LAKE
Located 30 miles west of Duluth, Minnesota,
Big Sandy Lake is approximately 9,000 acres in area. The Big Sandy Lake
Shoreland Revegetation Project was initiated in the late Fall of 1995 by the Big
Sandy Lake Association which contacted the University of Minnesota and the
Minnesota Board of Water and Soil Resources in Duluth for advice on shoreland
revegetation. This active and very informed group of residents had already
produced a videotape on lakeshore ecology, visually documenting problems such as
severe erosion on construction sites, decreased water clarity, increased algae
bloom and loss of previously extensive beds of emergent vegetation on Big Sandy
Lake.
Dr. Susan Galatowitsch, University of Minnesota, working together with
Jean Pitt at the Minnesota Extension Service and Barbara Liukonnen of the
Minnesota Board of Water and Soil Resources submitted a proposal to the
Minnesota Pollution Control Agency in late 1994. The first year budget
submitted for staffing, materials and expenses was approximately $33,000.
Between January of 1995 and March of 1996 demonstration site selection, design,
planting plans, plant ordering, harvesting and greenhouse propagation were
accomplished, as well as environmental monitoring design and implementation and
landowner information/education were achieved. In the second year beginning in
April, 1996 demonstration site vegetation installation, monitoring of
revegetation success, continuing environmental monitoring, extension education
and project documentation will be accomplished ending in June, 1997 with the
final report.
The Big Sandy Lake Association obtained seven volunteer
landowners for the project. Of these seven, three were eliminated from the
research portion of the study for the following reasons: structural needs (i.e.
severe erosion necessitating major grading), high fetch coupled with pollution
and very high wave impact as a result of an adjacent boat fueling station, or
largely intact upland and aquatic vegetation. The latter site provides an
"editing" site; an example of good management practices on a site before it
drastic disturbance and to demonstrate the landscape quality of a "natural"
lakeshore site.
The four study sites vary in the degree of devegetation and the
composition of horizontal structure in terms of relative amounts of upland, wet
meadow, and emergent vegetation zone within each study area. They are similar
in terms of all being relatively protected sites, and of a generally southerly
aspect. Lake bottom soils vary from sandy to fine, with varying levels of
organic matter and existing aquatic vegetation.
THE DESIGN COMPONENT
Early in the research process the extent of the "people factor" was strongly felt.
Landowners wanted to know what this revegetation was going to look like, a
question not generally encountered in the process of a scientific research
project. It was clear that owner acceptance and appreciation of the visual
aspect of the restoration was critical to long term vegetation survival. The
properties would very likely be "un-revegetated" after study completion without
this kind of "investment" in the project by the property owners.
In response,
Dr. Galatowitsch realized that this project needed a strong visual design
strategy, and that the design would be integral to the success of the project.
Julie Bargmann, a faculty member in the Department of Landscape Architecture at
the University joined the project in the late Spring of 1995. This writer, a
graduate student in landscape architecture was then brought on as project
designer under Ms. Bargmann's direct supervision. Art and science thus met.
From a design perspective, the importance of integrating the study area with the
site as a whole is essential. Plant composition, form and placement of the
revegetation design must exist in relationship to the individual site itself and
the individuals that inhabit each place. Detailed interviews with landowners
were conducted in order to learn exactly how they use their property so that
these uses and desires would be maintained in the design. For example, one
landowner told of how his grandchildren like to use the slope to the lake for
sledding in the winter, an important factor to take into design consideration
and something that might only emerge in a June encounter after long conversation
and careful questions. This seemingly small piece of information about the
personal side of a property had a decided effect on the final placement of the
study area and spurred a recommendation to relocate a dock structure to
accommodate it. Other examples of important design considerations were existing
perennial gardens, dock and boat space and upland storage of these in winter,
and the amount of mown turf needed for specific activities.
A site design was
developed which addresses both the study need for comparability between sites
for data collection and flexibility to account for differing proportions of
upland, wet meadow or emergent vegetation zones as well as differing private
land uses. This need for similarity in the service of research again accentuates
the marriage of art and science in this project. The challenge is to create
sites which will provide strong research data validity and are also distinctive,
interesting and cohesive landscapes.
REVEGETATION
Planting will be begun on the
study sites in June of 1996 as the lake level stabilizes. Plant species used to
revegetate these lakeshores are native to the sites and the area surrounding Big
Sandy Lake. As this information had not been cataloged previously, several
sources were brought together to form a comprehensive plant list for the area;
DNR Lake Survey Reports, University of Minnesota Herbarium (Aitkin County Flora,
Savanna State Forest Flora and Savanna State Forest Flora-Big Sandy Lake),
Ownbey and Morley "Vascular Plants of Minnesota", inventory and specimen
collection on each study site and corresponding reference site, and personal
observation. This resulted in an original list of approximately 500 plants.
Plant inventories of each study site were performed in Summer, 1995 to obtain
common species and vertical structure found on demonstration and reference sites
were performed. Revision and refinement of inventories coupled with the
composite lists through the summer of 1995 produced a final list approximately
50 species, and specific plant lists for each study site. In the interest of
minimal disturbance on the existing sites and development of soil binding root
mass over the course of the first season, plants as opposed to seed mixes will
be used and soils will not be amended.
In addition to species requirements,
concerns regarding local genotypes were also addressed through limiting plant
acquisition to a 100 mile radius of Big Sandy Lake with preference to Aitkin
County growers. Because the demand for these plant species is not common in the
retail nursery business, some difficulty has been experienced in acquiring some
species, particularly aquatics. In response to anticipated supply problems,
several species have been cultivated at the University of Minnesota greenhouses
for the project.
THE AQUATIC GARDEN
The design consists of three overlapping
plant matrices; an upland, wet meadow and aquatic matrix. These matrices
consist of the same plant species for each site though in different proportions
as mentioned above. For example, within the upland matrix are a blend of woody
species, forbs, graminoids and ferns such as Rosa acicularis, Amalanchier
laevis, Ranunculus septentrionalis, Aster spp., Carex pensylvanica, Onoclea
sensibilis and Thelypteris palustris. In the wet meadow Impatiens capensis,
Iris versicolor, Viola spp., Carex lacustris and C. scoparia, Calamagrostis
canadensis, Scirpus atrovirons and Onoclea sensibilis make up the matrix. In
the emergent zone are Sagittaria latifolia, Potamogeton richardsonii and P.
pectinatus, Sparganium eurycarpum, Vallisneria americana, and Scirpus validus
Within each matrix are "color patches" -concentrated plantings of one species
per patch, three to five patches per matrix-that are unique to each site. These
species include Aquilegia canadensis, Aronia melanocarpa and Uvularia
grandiflora in the upland, Eupatorium purpureum, Caltha palustris and Stachys
palustris in the wet meadow, and Acorus calamus, Brasenia schreberi and Nymphaea
oderata in the emergent zone.
The aquatic garden planting is knit together by a
wave breaking structure consisting of a series of modular fence sections in a
pattern of connected 'v's which connect the upland through the aquatic zone. The
structure also serves to house environmental monitoring equipment as well.
Additional posts placed between structure sections in the water will measure
wave height. A second set of structure posts and monitoring posts without
actual fence sections are sited adjacent to these, serving as the control site.
A primary concern in designing these gardens and wave breaking structures was
the creation of a system of revegetation that would be manageable by the
landowner both physically and economically. Large equipment for installation and
removal should not be required. It is also a goal of the project that the fence
structures are attractive amenities during plant establishment and become
available to other landowners as the plants in these initial sites become
established.
PROJECT ASSESSMENT: MONITORING
Design of monitoring equipment and
initial environmental monitoring has been done by Pat Lawton, a University
student in biological sciences. It is planned that long term monitoring will be
conducted by "Wave Watchers", a volunteer program of Big Sandy Lake residents.
The need for local monitoring of environmental conditions is crucial to project
success, especially in terms of severe weather data which can be generated
suddenly and with little warning.
Monitoring stations installed in the Fall of
1995 have provided baseline soil and water data. Control and reference site
monitoring will provide comparison data related to lake changes due to
revegetation. Wave conditions, suspended solids, soil erosion and sediment
measurement will contribute increased understanding about the role of
environmental conditions on plant mortality. Survivorship and growth of
installed vegetation, central to this study, will be measured periodically over
the first summer (1996) by the researchers, and further data will be obtained
the following spring on overwintering survival, critical for long term
restoration.
EDUCATION
Detailed and ongoing information support to landowners
regarding lake ecology and native plant communities are seen as another
essential factor in addressing lake water quality issues. Minnesota Extension
Service staff will be coordinating this informational support. The Big Sandy
Lake Shoreland Revegetation Project has received notice via a Minnesota
Extension Service videotape segment which was broadcast by satellite to viewers
in 19 states. In addition, there are plans to develop an Internet resource for
information on lakeshore revegetation, local and regional newspapers have
reported on the project, and the slide collection from the project will be made
available in print form as a reference for shoreland owners.
Plans for development of an Internet resource for information on lakeshore revegetation
are in process, and the slide collection from the project will be made available
in print form as a reference for shoreland owners.
CRITIQUE
In critique, I
think that the goals stated in then introduction to this paper are valuable and
attainable ones. At the same time it needs clarification that it is not an
expectation of this study to impact water quality on Big Sandy Lake. As this is
a lake with many miles of shoreline, we do not expect that restoration of the
vegetation on four, or even 20, 75-100 foot lot fronts would measurably improve
water quality on the lake as a whole. We can, however, because of the current
understanding of the ecological function of both littoral and upland intact
vegetation, envision such an impact in the future if achievement of methods for
successful plant establishment were coupled with a public awareness and
commitment to large scale revegetation. On a regional or even larger landscape
scale, there is the potential to improve the ecology of freshwater lake
environments and protect this valuable landscape resource.
REFERENCES FOR PLANT MATERIALS
Ownbey and Morley, "Vascular Plants of Minnesota: A Checklist and Atlas"
University of Minnesota Herbarium, Aitkin County flora
University of Minnesota Herbarium, Savanna State Forest flora
University of Minnesota Herbarium, Savanna State Forest flora (Big Sandy Lake)
MN. Department of Natural Resources, Lake Survey Reports (1990, 1982, 1975, 1956, 1947, 1939)
Nurnberger, Patience Kidd, "Results of the Investigation of Big Sandy Lake (Summer 1927)"
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