Jane Shuttleworth

Bulrushes often form extensive beds along lake and wetland shores where they provide erosion control, water quality, aquatic habitat and aesthetic benefits. Growing awareness of these benefits is leading to increased efforts by resource managers and homeowners to protect and restore bulrushes and other lakeshore vegetation. This paper explores techniques for bulrush revegetation utilizing rootstock. Because little published information exists on this topic, research efforts focused on interviewing resource managers, researchers and nursery owners who are pioneering efforts in this area. Their methods are compared to gain a better understanding of project successes and failures. Hardstem bulrush (Scirpus acutus) is the main species discussed in this paper as most restoration efforts have focused on this species.

Persons interviewed included aquatic plant biologists, fisheries biologists, and water resource managers from natural resource agencies in Minnesota and Wisconsin and a private nursery owner. The interviews were unstructured but followed an outline of topics including project planning and goals, selection of plant material source, rootstock collection and planting techniques, maintenance and monitoring.

 Bulrush Ecology

Under natural conditions, bulrush spreads vegetatively by underwater stems (called rhizomes or rootstock) or by the dispersal of floating clumps. Successful seedling establishment seems to require exposed mudflats that occur during drought cycles that occur naturally or are induced artificially with drawdown (Harris and Marshall 1963). This can be artificially induced by deliberate drawdown technique. While drawdown may be useful for bulrush establishment in wetland situations, it is not always a practical technique for lakes where it may interfere with other private and public shoreline uses and lake management objectives. In comparison, rootstock can planted in water depths without the need for drawdown and may require less time and maintenance for establishment compared to seed. Thus, utilization of rootstock seems a more practical method for lakeshore revegetation than seed.

 Hardstem bulrush is an emergent perennial that forms stout rhizomes and grows in water up to five feet deep in marshes, lakes, bogs and streams. Hardstem bulrush prefers firm, sandy to marly substrate with good water circulation in the root zone (Eggers and Reed 1987, J. Anderson personal communication). In deeper water, presumably where fewer species can grow, bulrush forms large monodominant stands. In shallower depths it often grows interspersed with other emergents. The beds form a self protecting unit against wind and wave action and from impacts from muskrats and other herbivores. The rootstocks provide an expansive carbohydrate energy storage and carbohydrate storage seems to occur best at shallower depths or in moist soil.

 Little information exists in the literature in regard to bulrush life history (S. Galatowitsch, J. Lillienthal, S. Nichols; personal communication). Available information suggests they follow a growth pattern typical of large emergent marsh plants described by Bernard (1989). Shoots begin rapid growth in early spring owing to photosynthesis and translocation of energy into the shoot from the rootstock. From late spring to mid-summer growth may slow, perhaps as a response to carbohydrate depletion from shoot production. At this time flowering may occur, further depleting carbohydrate storage. The early spring shoots reach maturity by mid-summer and begin translocation of carbohydrates to the rootstock. New rootstock develops and new shoots emerge from mid-summer until the onset of winter. Harris and Marshall (1963) reported an increase in hardstem bulrush seed production in response to drawdown indicating plants may expend more energy in vegetative than sexual reproduction under deep water conditions.

 Causes of Bulrush Decline

Many of the persons interviewed reported a decline in bulrush beds based on direct observation, review of historic photographs or conversations with local residents. However, no single cause of their decline was fronted. Rather, numerous human-induced factors seem to be operating which vary with each location and may interact together to further weaken the beds. These include artificial water level manipulation, water quality degradation, lakeshore and watershed development, boat traffic and removal by fishermen, boaters and swimmers (McFadden 1996; J. Lillienthal, S. Nichols personal communication). Natural disturbances, such as wind, wave action and ice shear can also damage or further stress the health of the beds (J. Lillienthal, S. Nichols; personal communication).

 Artificial water level manipulation may replace the natural drought cycle of lakes by maintaining stable water levels and not allowing bare mudflats for seedling establishment. In addition, authors have reported detrimental effects of prolonged stabilized water levels on most species of emergent aquatics (Harris and Marshall 1963). Watershed and shoreline development can also stress some wetland plants by increasing the amount of impervious surface in the watershed, resulting in greater runoff volumes over a shorter time period compared to natural conditions.

 Increased eutrophication from agricultural and other runoff may provide a competitive advantage to cattails and more nutrient-favoring species over bulrush. Increased eutrophication may also inhibit the natural dispersion of bulrush clumps broken off by muskrats, waves and other causes into shallow habitat as these areas become increasingly occupied by cattails and other species more competitive under eutrophic conditions (S. Nichols personal communication).

Deliberate removal of bulrushes by swimmers, fishermen, boaters and shoreline owners is another source of bulrush decline despite the fact that a permit to remove aquatic plants is required by law in some states.

 Stan Nichols ( personal communication) postulates bulrush beds may require a critical size to keep growing and to prosper, and these factors interact over time rather than at once to whittle down and destroy the beds. Monitoring of existing natural beds in regards to these disturbances would provide useful data on the status and decline of bulrush beds.

Most persons interviewed attempted bulrush establishment where they were known to occur historically. Local residents, DNR lake surveys and historic photographs were used to identify these locations. Ideal conditions for bulrush establishment include gently sloping shorelines, hard and sandy substrate and protection from wind and wave action. Some planting failures were caused by muskrat and cattle herbivory and removal by swimmers. The potential for these disturbances to occur and feasible methods for their control should also be part of site selection and project planning.

 Selection of Source Material

Three sources of plant material were used by the persons interviewed: commercial nursery stock, wild harvested stock and greenhouse propagation of rootstock grown from wild harvested seed. Collection of seed and rootstock from the wild requires a Department of Natural Resources (DNR) permit.

 All persons interviewed problems with the quality of commercially obtained rootstocks that are generally wild harvested (Galatowitsch, personal communication). Commercial stock was reported to frequently be undersized and of low vigorous. It often arrives in poor condition, indicating the need for a minimum time lag between harvesting and transplanting. In the most severe instances rootstock arrived mildewed, in another case it arrived frozen. However, one resource manager reported better success with material received earlier in the growing season (May) compared to a second shipment after the plants had already begun to develop shoots (T. Ebinger, personal communication). To ensure better control over nursery stock quality, seeds can be collected and greenhouse propagated for stock ( S. Galatowitsch personal communication). Nursery propagated stock requires an additional year of project planning to allow production of a crop of rootstock.

 Rootstock should come from well established beds located as close as possible to the restoration site to ensure use of genotype adapted to local conditions. Maintenance of a 200 mile radius from the project site is the standard "rule of thumb" for collection local genotypes in the Midwest (S. Galatowitsch personal communication). However, it is speculated, even within this radius, that ecotypes adapt to localized shallow or deep water level conditions (R. Kahl personal communication).

 Time, labor and efficient tools are the main logistical considerations after site selection when transplanting wild plants. Plants should be harvested and transplanted on the same day to avoid stressing plants. Harvested stock can be placed in large washtubs and occasionally splashed with water to prevent heat stress and drying out. Harvesting and transplanting is a time consuming and labor intensive process. Resource managers often assembled teams of volunteers from lake associations and other local clubs to assist. Planting events are an opportunity for education and to develop increased public interest and support for bulrush establishment and protection (J. Anderson personal communication).

 Rootstock is difficult to harvest and requires good tool to avoid bruising the rhizomes. Sand and gravel shovels or spades were more useful tools for harvesting than garden forks (J. Anderson personal communication). Most persons selected rootstocks in clumps of 3 to 5 stems for handling convenience, some clipped the stems 8 to 10 inches above the rootstock for easier handling. Others warn that cutting the shoots too short allows water to enter into the plant tissue, depleting oxygen and killing or severely stressing the plants (J. Lillienthal personal communication).Most persons interviewed collected rootstock in early May before initiation of shoot growth has begun to prevent stressing plants. Terry Ebinger also tried transplanting as late as mid-July. He clipped the leaves to transfer energy back into the rootstock and to stimulate root growth. He reported no difference in first year survivorship between the July and May transplants.

Planting techniques ranged from planting stock directly into the water to various methods of anchoring rootstock with geo-jute fiber, burlap bags and tires. Rootstock can easily be planted in the water with a shovel. It is easiest to plant in shallow water. However, plants may be vulnerable to wave action and ice shear if planted too close to shore. Therefore, it is recommended to plant rootstocks at a minimum depth of 18 to 20 inches out of the range of wave and ice action.

Rootstock planted into hard, sandy substrate with a shovel does not require anchoring (J. Lillienthal, R. Kahl, S. Galatowitsch; personal communication). Hardstem bulrush rootstock prefers hard substrate while softstem bulrush and river bulrush (Scirpus validus and S. fluviatilis, respectively) are tolerant of a wider range of substrate (J. Lillienthal, R. Kahl personal communication; Eggers and Reed 1987). However, sediments may be churned by wave action limiting photosynthesis and survivorship (R. Kahl personal communication).

 A more costly but promising commercial nursery technique is the bioengineering approach where nursery material is grown in coconut fiber blankets which are then rolled up and shipped (S. Nichols personal communication). Local seeds can be collected and sent to the nursery to ensure use of local genotype.

To minimize time and discomfort from working in cold water during spring transplanting, two resource managers devised a system of sewing rootstock at about one clump (3-5 stems) per square foot onto rolls of geo-jute, a decomposable fiber product. The jute can be rolled up like a carpet, transferred to the water, unrolled and weighted down with rocks. This method allows collection and planting in the same day (J. Anderson personal communication). Geo-jute is available from landscaping businesses and comes in various sizes, those interviewed used one-inch mesh that comes in 25 foot rolls three to four feet wide. Terry Ebinger used one layer of geo-jute with success. Jed Anderson quilted the rootstocks between two layers of geo-jute. A first attempt became uprooted and did not survive. The additional top layer of mesh may have acted as a trap for wave undercurrents, uprooting the plants. He tried this method again with better results, this time weighing the jute down more securely by placing rocks every 2-3 feet.

Burlap sacks sewn out of 12 inch squares were filled with peat, the rootstock and weighted with rocks (T. Ebinger personal communication). Initially the plants did well but the burlap mesh proved too fine to allow root growth, killing the plants. In another method, rootstock was planted inside tires fastened down with metal rods. This method was successful initially and protected plants from muskrat herbivore and wave action. However, the tires eventually silted in, smothering the plants. Increased water temperature inside the tires may also have contributed to plant mortality (T. Ebinger personal communication).

Use of wave breaking structures is encouraged at least during initial phases of establishment even though bulrush stands occur naturally in areas exposed to strong wind and wave action ( J. Lillienthal personal communication). In one case, the use of wave break structures could have contributed to planting success even in areas sheltered from wind and wave action by trapping algal blooms which can smother and kill plantings.

Wave breaks should be made of impermeable, sturdy material. Cost and allotment of sufficient time to install and maintain are important factors in selecting wave break techniques. The breaks must be well anchored yet easily removed before winter to prevent ice damage and causing a safety hazard to snowmobilers. Barriers made of tires held down by metal rods were successful but require maintenance and are heavy and time consuming to install. Plywood can be installed more easily than tires and is easier to remove. DOT silt fencing and snow fencing are suitable only in sheltered areas (J. Lillienthal personal communication), other found them too porous for effective buffering of wave action (S. Galatowitch personal communication).

 Evaluating Success

Many sucessful and unsuccessful techniques for bulrush establishment were identified in this paper. Most project failures appear explainable due to the following factors: poor site selection and substrate selection, low quality and/or damaged rootstock, inappropriate anchoring methods and substrate type, lack of protection against wind, wave and ice action and herbivores, removal by recreationists, and herbivory. Natural factors, such as storms or drought, can also negatively impact projects.

 More puzzling is the instance of several bulrush stands that established rapidly and vigorously in the first year only to die out in the following year. No project successes longer than one year were reported although several projects are now being monitored into their second year (J. Lillienthal, T. Ebinger), suggesting the initial causes of disturbance, which are complex and interact in cumulative ways, need better understanding as well as a better understanding of bulrush ecology.

 Researchers and resource managers emphasized projects should allow at least 3 and preferably 5 years of maintenance and monitoring of success. Some project managers were able to monitor the plants on a monthly basis from June through September in fixed plots. Due to budget and time constraints this is not always possible. Recognizing the importance of monitoring, recent projects have created volunteer teams from local clubs and residents to assist resource managers and researchers in evaluating project success.

 References

Anderson, J. 1997. Personal communication. Minnesota Department of Natural Resources.

Ebinger, T. Personal communication. Minnesota Department of Natural Resources.

Eggers, S. and D. Reed. 1987. Wetland Plants and Plant Communities of Minnesota and Wisconsin. US Army Corps of Engineers, St. Paul District. 201 pp.

Galatowitsch, S. 1997. Personal communication. University of Minnesota.

Galatowitch, S. and A. Van der Valk. 1994. Restoring prairie wetlands: an ecological approach. Iowa State University Press, Ames.

Harris, S. and W. Marshall. 1963. Ecology of Water level Manipulation on a Northern Marsh. Ecology 44 (2)

Kahl, R. 1997 Personal communication. Research Scientist, Wisconsin Department of Natural Resources.

Lillienthal, J.1997 Personal communication. Minnesota Department of Natural Resources.

McFadden, K. 1996. Design at the edge: art and science for lakeshore revegetation. Restoration and Reclamation Review 1(1)

Nichols, S. 1997. Personal communication. Wisconsin Geological and Natural History Survey.

Wakeman, B. 1997 Personal communication. Wisconsin Department of Natural Resources.

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