Management Experiments on Lake Erie Flowering Rush
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Bowling Green State University ScholarWorks@BGSU Honors Projects Honors College Spring 4-29-2013 Management Experiments on Lake Erie Flowering Rush Alyssa Dietz Follow this and additional works at: https://scholarworks.bgsu.edu/honorsprojects Repository Citation Dietz, Alyssa, "Management Experiments on Lake Erie Flowering Rush" (2013). Honors Projects. 19. https://scholarworks.bgsu.edu/honorsprojects/19 This work is brought to you for free and open access by the Honors College at ScholarWorks@BGSU. It has been accepted for inclusion in Honors Projects by an authorized administrator of ScholarWorks@BGSU. 1 Management Experiments on Lake Erie Flowering Rush Alyssa Dietz HONORS PROJECT Submitted to the University Honors Program at Bowling Green State University in partial fulfillment of the requirements for graduation with UNIVERSITY HONORS April 29 th , 2013 Advisors: Dr. Helen J. Michaels, Department of Biological Sciences Dr. Enrique Gomezdelcampo, Department of Environment and Sustainability 2 Summary: The issue of invasive species has been a major concern for many Great Lakes ecosystems over the past several decades. Since the first noted invasive animal, the sea lamprey, these fresh water ecosystems have been invaded by over 180 different plants and animals that create over $100 million worth of damage a year (Rosaen et al . 2012). Because the five Great Lakes, along with their rivers, streams, and wetlands are such an interconnected series, the introduction of any invasive species to one of the Great Lakes, such as Lake Erie, means that invaders are likely to spread to all other freshwater ecosystems in the area (Rosaen et al . 2012). With the various ways that many introduced species can alter the nutrient availability, habitat quality, and species richness, many wildlife managers are continuing to develop management strategies that remove or greatly limit the further spread of invasive species. Of major concern are invading aquatic plants whose ranges continue to expand. The purpose of this study was to understand the response of an invasive aquatic plant, Butomus umbellatus L. in Lake Erie wetlands to the combined management strategies of clipping and flooding. These strategies are hoped to be shared with local wetlands managers in better hopes of limiting the impacts and concerns that this invasive has created in local ecosystems. Introduction: Given their diverse morphology, invasive macrophytes, or aquatic plants, have the potential to alter community complexity, change oxygen levels within aquatic systems, and facilitate in the invasion of other exotic species (Schultz and Dibble 2012). Though significantly detrimental to native ecosystems, macrophytes receive very little attention compared to the issues of invasive aquatic animals. One particularly understudied species found in Lake Erie is 3 Butomus umbellatus , commonly known as flowering rush. Originally introduced from Europe for aquatic gardens, B. umbellatus has now spread throughout along the northern United States and Canadian border (Brown and Eckert 2005 ) (Figure 1). Figure 1. The Invasive Range of B. umbellatus spans most of the U.S./Canadian border. Characterized by triangular leaves, B. umbellatus is not a true rush, but is rather a single species belonging to the p lant family Butomaceae ( Brown and Eckert 2005). Though little is known about its specific origin and impacts, the reproduction and life history of B. umbellatus are well known. B. umbellatus has three methods of reproduction and can reproduce sexually or asexually. B. umbellatus can reproduce sexual ly through seed, but there is som e argument over the viability of seeds produced by Nort h American populations ( Kliber and Eckert 2005 ) (Picture 1). It is thought that most populations in this region reproduce dominantly via asexual methods through rhizomes (Picture 2) and vegetative prop agules (Picture 3) (Brown and Eckert 2005 ; Parkinson et al . 2010). These vegetative propagules are pieces of rhizomes that break off from adult plants and form roots while floating. When marsh water levels drop, the vegetative 4 propagules are likely able to establish quickly, potentially giving B. umbellatus a great advantage over smaller native seedlings. Picture 1. Flower of B. umebllatus produce seeds Picture 2. Below ground rhizomes through sexual reproduction. allow for asexual reproduction. Picture 3 . Vegetative propagule growth on the rhizome of an established plants are produced by asexual reproduction. 5 As an invasive, B. umbellatus can alter native vegetation and macroinvertebrate communities (Shultz and Dibble 2012). In Canadian areas, B. umebellatus has begun to threaten native populations of Zizania aquatica (wild rice). With further spread throughout the Great Lakes Region, Canada has designated B. umbellatus as a “principal invasive alien” (White et al . 1993 in Brown and Eckert 2005). In the United States, B. umbellatus has been found in Lake Erie wetlands since the early twentieth century (Brown and Eckert 2005). One particular regional population is located at Ottawa National Wildlife Refuge (ONWR) in Oak Harbor, Ohio. ONWR is a diked wetland ecosystem manager by altering flooding levels necessary for habitat for native shorebird populations. As pilot studies have demonstrated, B. umbellatus is capable of changing macroinvertebrate community richness, greatly reducing this vital food resource for local fish and bird populations (Dietz, unpublished data). With such an impact to the major taxa of the region, ONWR and other local wetland refuges have begun to implement management strategies to control B. umbellatus . Most strategies to remove B. umbellatus have had minimal success in restoring invaded marshes. Common strategies include manually digging out plants, cutting, and the application of herbicides (Parkinson et al . 2010). Digging plants has had mixed results due to the further spread of B. umbellatus after disturbances to the rhizomes (Parkinson et al . 2010). In addition, the application of herbicides has proven inefficient due to the thin emergent leaves of B. umbellatus that reduce the chance of chemicals adhering to the plant (Parkinson et al . 2010). Applied chemicals could wash away and potentially alter the chemical composition of water where they could impact non-target species, such as amphibians. These inefficiencies in current management strategies of B. umbellatus have caused many wildlife managers to search for new ways to successfully manage or eradicate the invasive species. 6 Some of the effective treatments developed for the removal of other aquatic plants include inundation (flooding) and clipping (Kercher and Zedler 2004). Clipping removes leaves and stem tissue critical for photosynthesis and the transportation of oxygen to roots, limiting the future growth of the plant (Mayence et al . 2010). The inclusion of secondary clipping treatments is believed to further limit the development of plants. This second cutting is intended to remove additional growth material after the plant has used its carbohydrate and nutrient reserves but before new leaves have begun to conduct photosynthesis and begin to restore the resources that it took to grow them. Inundation limits both light levels for photosynthesis and oxygen for root respiration. As water depth increases, both of these vital environmental conditions decrease, reducing growth and plant survival (Kercher and Zedler 2004). While some programs treating B. umbellatus with clipping have had little impact on the eradication of the species, a combination of inundation and clipping may be a more effective method in preventing the species’ spread into more southern wetlands (Parkinson et al . 2010). Previously conducted pilot studies investigating the impact of flooding levels alone have suggested that B. umbellatus tended to have lower biomass in higher water depths (Dietz, unpublished data). To develop better management strategies of B. umbellatus in Lake Erie wetlands, this experiment investigated the effects of these alternative management strategies of clipping and inundation through the following experimental questions: 1) How does flooding effect the development and growth of B. umbellatus ? and 2) Do combined treatments of flooding and clipping effectively reduce the growth of B. umbellatus ? Materials and Methods: 7 Two hundred B. umbellatus plants were collected from Ottawa National Wildlife Refuge (ONWR) in Oak Harbor, Ohio in late October 2012. Twenty-four hours following collection, all plants were washed to remove algae and herbivorous invertebrates that could damage the leaves. Senescing leaves were trimmed before the plants were planted in natural clay based cat litter with no chemical additives (Special Kitty Natural Clay Cat Litter). Cat litter was chosen because of its similarity in composition to the clay-based soils of natural marshes. After washing, all plants were vernalized for eleven weeks in a growth chamber at Bowling Green State University. All plants were stored at 8 ˚C with 8 hour photoperiods and were watered every two days to maintain at least one to two inches of standing water throughout dormancy. After eleven weeks of vernalization, plants were placed in the Bowling Green State University greenhouse under supplemental lighting in order to break dormancy. After emergence in early February 2013, plants were again washed and senesced or dead leaves were removed before planting in 11 cm (4.5 in) clear plastic pots containing 300 g of 100% dry clay. Rhizomes of larger plants that