Vegetation Invasive Species Naturescaping
Aquatic Plant Policy - download pdf
Vegetation of Devils Lake by Bob Storer, former Devils Lake Water Improvement District (DLWID) manager.
Aquatic plants are a natural element of lake ecosystems and serve many important functions, including:
1) providing oxygen;
2) stabilizing shorelines and bottom sediments;
3) providing habitat for fish, amphibians, invertebrates, birds, and mammals;
4) reducing nutrients through uptake; and preventing algal blooms.
Devils Lake has a long history of aquatic plant problems. Macrophytes (large vascular aquatic plants) obtain their nutrients from bottom sediments. Aquatic plants will always be a management issue for Devils Lake due to the fact that the lake is very shallow and has an abundance of rich nutrients in the bottom sediments. Devils Lake has also been plagued over the years with several invasive or non-native plant species. Invasive nonnative weeds are plants that have been introduced to this region through human activities, and due to aggressive growth patterns and lack of natural enemies in this region, spread rapidly into native plant habitats. This can reduce habitat diversity, food, and shelter for many fish and wildlife species, and the ability of the natural environment to perform a wide variety of important ecological functions.
Two of the most aggressive nonnative aquatic plant species that have been present in Devils Lake include: Eurasian watermilfoil (Myriophyllum spicatum) and Brazilian elodea (Egeria densa). Eurasian watermilfoil reproduces vegetatively. Its invasiveness stems from its ability to regrow from tiny fragments. This exotic species has been known to grow up to 20 feet in length! In the years following the introduction of grass carp there was a drastic change in plant community composition in Devils Lake. Brazilian elodea invaded the lake and completely displaced Eurasian watermilfoil.
It is interesting to note that Devils Lake has had native varieties of both of these species. The native species typically are not as aggressive as non-natives and are known for remaining in a relatively balanced setting. Other native species known to have recently inhabited the lake include: Coontail (Ceratophyllum demersum), Waterweed or common elodea (Elodea canadensis), Water celery (Vallisneria americana), and several species of pondweeds (Potamogeton spp.).
Submerged and floating-leaved plants are rooted in the lake bed with their foliage either suspended below the surface, floating upon it, or both. Pondweeds are a large, variable genera composed of primarily submergent and floating-leaved plants. The stems arise from fibrous roots and are flexible. Pondweeds will often have radically different submergent and floating leaves on the same plant. Underwater leaves are thin and delicate, and floating leaves are tough, leathery, and oval in shape. The flowers are usually in oblong or ball-like species that may be above or just below the water's surface. The habitats of various species of pondweeds vary, but typically pondweeds are found in lakes to a depth of 12 to 15 feet. Pondweeds are an important food source for many waterfowl species. They may also pose a nuisance by forming dense growth, curtailing the recreational uses of lakes.
The Devils Lake Water Improvement District (DLWID) contracted with researchers from Portland State University during 1995-1996 to conduct a revegetation and water quality study. This revegetation study was conducted to determine whether a revegetated lakebed is more resistant to invasion and establishment of Brazilian elodea than an unvegetated lake bed. Grass carp exclosures were established in the northwest arm of the lake in May 1995.
Four planting treatments were applied to the exclosures:
1) Sago pondweed (Potamogeton pectinatus)
2) Water celery (Vallisneria americana)
3) Sago pondweed plus water celery, and
4) a control with no planting
The revegetation study indicated that the lake bed will become quickly revegetated if grass carp are removed from the lake. A number of native species colonized the grass carp exclosures. Planting the exclosures did not result in establishment of the planted species. Rather, "volunteer" species dominated the exclosures. Brazilian elodea, when introduced into the exclosures, did not become established. Eurasian watermilfoil did establish in one exclosure as a volunteer species.
A stand of low-growing waterwort (Elatine sp.) was present within the exclosures in 1995. Waterwort was even found outside the exclosures, suggesting that it is relatively unpalatable for grass carp. Other species commonly found in the exclosures included: Najas spp., Nitella spp., and Calitriche spp.
Year-to-year changes in the composition of the macrophyte community in the exclosures indicated that plant community composition is highly dynamic in the short-term, and that development of a stable plant community after grass carp removal may require several years. We do know now that too many grass carp were introduced into Devils Lake. As a result, the complete eradication of all the submersed aquatic plants has occurred. This has subsequently led to the drastic decline in the warmwater fishery and the drastic increase in the frequency and severity of algal blooms. So where do we go from here? The lake is out of balance once again, and I believe we need to re-establish a balanced population of native aquatic plants. This in terms of lake and watershed management techniques is easier said than done. We also need to develop and permanently install warning signs at all public boat launch areas around the lake. These signs would help to educate and alert boaters about the problems associated with nonnative aquatic plant species. For example, Eurasian watermilfoil is commonly spread by careless boaters who do not remove milfoil fragments from their boat or trailer when leaving an infested lake. Aquatic plant management should be approached in an integrated manner to ensure balance of uses and protection of natural resources - there are no quick fixes.
There are four types of aquatic plant control techniques: physical, chemical, mechanical, and biological. Each technique has its advantages and disadvantages. The most effective long-term control of aquatic plants assesses a variety of control measures in combination with source controls of sediment and nutrients. Controlling watershed sources through the use of best management practices (BMPs) is essential to the long-term health and sustainability of a lake ecosystem.
A lake cannot be all things to all people. Dependent upon where you live and how you use the lake may very well determine how you will view and accept or tolerate certain types of plants in various locations throughout the lake. A bass fisher welcomes a diverse plant community to provide structure and habitat for the fishery. A water-skier or sailboat owner may not. There are some aquatic plants and emergent species that only grow in the nearshore areas such as pondlilies and yellow iris and several submergent species that typically grow relatively low in relation to the bottom. These include: waterweed or elodea, bushy pondweed or naiad, and nitella spp. These species might be ideally suited in Devils Lake. They have the potential to provide the plant benefit without significantly impacting the recreational uses of the lake. Only time may perhaps tell what will become of the aquatic plant community composition in Devils Lake. I believe we must continue to educate, monitor, and evaluate.
In some respects, the future aquatic plant composition will not be up to us. On the other hand, we contribute to the problem and we must begin to change our behaviors. Simple things we all can do:
maintain your on-site septic system
cover up exposed soil areas
reduce the amount of fertilizer use on lawns and gardens and
maintain or replant a native vegetative buffer along the lake shoreline.
Species (Knotweed, Purple Loosestrife, etc.)
Devils Lake and its watershed have been invaded by several plant and animal species that are not native to this area. An introduced species does not always bring with it the biological controls that kept it from becoming a nuisance in its native habitat. Purple loosestrife is an invasive plant that could potentially take over Devils Lake. Volunteers are needed to pull it out of the ground. Click here for more information about purple loosestrife.
Environmentally Friendly Lawn Care
The Department of Environmental Quality (DEQ) sponsors a website with information about how to have a great-looking lawn without using chemical fertilizers and weed killers. The DEQ Healthy Lawns, Healthy Families site at www.healthylawns.org includes information about how our lawn care habits influence water quality and tips on how to practice natural lawn care. Misuse and overuse of pesticides and chemical fertilizers on the lawn can lead to lawn problems, and the chemicals themselves are often washed off the lawn by rain, headed for the storm drain and ultimately to Oregon's rivers and lakes. Once in the river or lake, the chemicals can cause problems for fish.
The Northwest Coalition for Alternatives to Pesticides has a website at www.pesticide.org.
Master Gardeners - Oregon State University Extension Service in Newport
Master Gardeners hold an annual plant sale at the Lincoln County Fair Grounds around the third Saturday in May. Call 541-574-6534 for information about becoming a Master Gardener or for help with your yard or visit http://extension.oregonstate.edu/lincoln/index.php
Naturescaping is a term used to describe planting a plot of land so that it is environmentally friendly to people and wildlife. Landscaping with native plants means reduced maintenance, little or no fertilizing, and less watering, clipping, mowing and weeding over time. Four easy steps to preserve wildlife in your area include providing food, water, cover, and places to raise young. The Oregon Department of Fish and Wildlife publishes a book, "Naturescaping, a Place for Wildlife." Plant lists and sample landscaping plans are included in the book. For more information visit www.dfw.state.or.us/NS/.
can be seen at Holmes Road Park located off West Devils Lake Road. Several
with help from the Watershed Group and the Master Gardeners http://extension.oregonstate.edu/mg/,
have planted a garden using a diversity of native plants. Shoreline plants
areas from erosion are featured. An interpretive display is planned for the
future. Visit often to see the improvements.
Another website about gardening is http://eesc.orst.edu/agcomwebfile/garden/enews/index.html.
Certified Community Wildlife Habitats (CWH)
National Wildlife Federation
By creating sustainable landscapes that avoid pesticides, chemical fertilizers and excess watering, Community Wildlife Habitat projects benefit the entire community: people, plants and wildlife. For more information on how to turn a community into a welcoming place for wildlife, visit
Rain gardens are a way for homeowners as well as businesses to participate in the reduction of polluted runoff, simply by planting a specialized garden. Rain Gardens are an infiltration technique - water is captured in a garden that features native plantings, and the water has a chance to slowly filter into the ground rather than run off into the storm sewer. It is a popular way to reduce nonpoint source pollution and has been popular along the East Coast for a number of years. http://dnr.wi.gov/org/water/wm/nps/rg/index.htm
Grape (Gary M. Stolz, USFWS), Holmes Road Park Naturescaping (R. Erickson)
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P.O. Box 36
Lincoln City, OR 97367