Evaluation of vegetation control techniques in large managed wetlands in Maritime Canada Mark Gloutney, Ducks Unlimited Canada, P.O. Box 430, Amherst, Nova Scotia, B4H 3Z5, Canada E-mail:
[email protected] Colin MacKinnon, Canadian Wildlife Service, 17 Waterfowl lane, Sackville, NB, E4L 1G6, Canada E-mail:
[email protected] Extended Abstract: Ducks Unlimited Canada and Eastern Habitat Joint Venture partners manage 21,827 ha of large wetlands in the Maritime Provinces. These large managed wetlands are essential in provision of pairing and brood rearing habitat for waterfowl in the Maritimes. Both of these factors have been identified as key waterfowl limiting factors in updated Eastern Habitat Joint Venture Implementation plans. Over time the extent of emergent vegetation within many of these large managed wetlands has increased, reducing their value to breeding and staging waterfowl, as well as restricting recreational activities. Many management techniques have been implemented but detailed assessments of longevity of vegetation control and waterfowl responses have been limited. The issue is future complicated by the fact that emergent vegetation can be either rooted or form floating mats The preferred management techniques involve flooding emergent vegetation to depths of 20 -30 cm above normal operating levels. This management technique is not always possible and is often limited by the elevation of the dykes, and the impacts of flooding adjacent lands and infra-structure or where the emergent vegetation are in floating mats. A review of management options identified four potential alternative management techniques. For rooted emergent vegetation the techniques include summer and winter mowing. For floating mats, the techniques include physical removal and mechanically breaking up the floating mats. The purpose of this project is to evaluate the cost effectiveness and waterfowl responses to these selected alternative vegetation management techniques.
The study was conducted on two wetlands within the Tintramar National Wildlife Area. These treatment wetlands had approximately 85 – 90% coverage by emergent vegetation. Control wetlands for the waterfowl surveys were managed wetlands with approximately 50% emergent vegetation. Waterfowl surveys prior to vegetation management revealed that there were more waterfowl (n = 590) and broods (n = 39) on control wetlands with desirable interspersion then on wetlands with 90% emergent cover (waterfowl n= 220, broods n = 8). Waterfowl surveys will continue in summer 2009. Summer mowing required a minimum of 60 cm of water to float the mower and costs $1,800/acre. There was no observed regrowth of emergent vegetation in the summer or fall following mowing. Options for winter mowing over ice were assessed and the preferred option selected was using a forestry crew with spacing saws. Based on pilot tests the costs are expected to be in the range of $250/acre. Floating mats were removed from Front Lake creating 5 openings in the emergent vegetation. Waterfowl were observed in these openings during fall staging period. Mats were easily cut with a chain saw and were then easily moved to areas where the excavator could remove them. Costs were $5,335/acre. Costs were higher then expected due to lower water levels in Front Lake which resulted in double casting of material. We anticipate that costs where material needs to be handled only once will be in the range of $3,200/acre.
Waterfowl and vegetation responses to the treatments will be conducted in the 2009 growing season and will be included in the poster when presented. Discussion will be developed to correspond to these results.
