|
Terrell's Island Open to the Public every day from Sunrise to Sunset. |
2008 and 2010 Terrell’s Island Vegetation Surveys
Andrew Sabai September 2010
In 2008 and 2010, aquatic plant surveys were conducted within the break wall at Terrell’s Island, Lake Butte des Morts using standard DNR point intercept methods of Hauxwell et al 2004. The 2008 survey was conducted July 13-15 and the 2010 survey was done August 23-25. Although over a month apart, results of occurrence should be similar. However, as would be expected biomass, reflected as rakefullness in this method, in August was greater than in July. No comparison should be drawn between the two years in rakefullness. Caution should be used when looking at the relative frequency of species between years; it does not necessarily equal changes in abundance. For example, wild celery made up 54.4% of the plant community in 2008, and 37.5% in 2010. This should not be taken as a loss of wild celery abundance, but a loss in its dominance in the community. In fact wild celery was found at 265 points in 2008 and 287 points in 2010, an increase of more than 9%.
Figure 1. 2008 vegetated sample points
2008 and 2010 Aquatic Vegetation Composition
Figure 4. Background: stiff arrowhead. Foreground: white water-lily (photo 7/7/2008)
Figures 5 and 6. Depth distribution of sample points
References Hauxwell, J., S. Knight, K. Wagner, and A. Mikulyuk. 2008. Recommended Baseline Monitoring of Aquatic Macrophytes in Wisconsin - Point-Intercept Sampling Method, Collection Protocol, Data Analyses and Applications. Wisconsin Department of Natural Resources, Madison WI. 26 pp.
Terrell’s Island Vegetation Survey Comparisons 1988-2010 Andrew Sabai September 2010
Vegetation surveys were completed at Terrell’s Island before and directly after break wall construction using transects. 1999-2001 used the methods of Deppe and Lathrop (1992). In 2008 and 2010 a point intercept method (Hauxwell et. al. 2008) was used for all navigable water within the break wall. The following data from 2008 and 2010 uses only those points that fall within the box in Fig. 1, making accurate comparisons of these surveys. Although different sampling techniques were used prior to 2008 both techniques should give comparable relative frequencies for each species. Data prior to 2008 from Cooke et al. 2005. Caution should be used when looking at the relative frequency of species between years; it does not necessarily equal changes in abundance of individual species.
Figure 1: Terrell’s Island. Green dots are 2008/2010 survey points. Only dots within the break wall and the box were used for comparison. Yellow lines represent the approximate locations of older transects. Red outlines designate the extent of wetland and aquatic vegetation.
References
G. D., Cooke, E. B. Welch, S. Peterson, S. A. Nichols. 2005. Restoration and Management of Lakes and Reservoirs, Third Edition. CRC Press, Boca Raton, FL. 616 pp. Deppe E. R., Lathrop R. C. 1992 A Comparison of Two Rake Sampling Techniques for Sampling Aquatic Macrophytes. Research/Management Findings Number 32 Bureau of Research, Department of Natural Resources, Madison WI. 5 pp. Hauxwell, J., S. Knight, K. Wagner, and A. Mikulyuk. 2008. Recommended Baseline Monitoring of Aquatic Macrophytes in Wisconsin - Point-Intercept Sampling Method, Collection Protocol, Data Analyses and Applications. Wisconsin Department of Natural Resources, Madison WI. 26 pp.
Conclusion |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
The reports deal with the composition of the plant community within the break wall, but there is a significant omission in them, and that is the area colonized by submerged vegetation. The average between 1975-79 was 128.6 acres of submergent vegetation. In 2008 I calculated 345 acres of submergent and floating leaf plants, a 168% increase in vegetation. In every other area there was either no change or a loss of vegetation from 75-79 to the 2008/2009 surveys. In fact if it were not for the increase of vegetation at Terrell's Island, Lake Butte des Morts would have had a 31% loss, but with Terrell's Island it experience a 9% gain. It is hugely important to the Upper Pool as a whole too, without a 42% loss, with a 27% loss. |
