ANALYZING VEGETATIVE COVER OF THE BOIS BRULE RIVER WATERSHED RE-VISITED IN NORTHWESTERN WISCONSIN, PART II: VEGETATION AND LAND COVER CHANGES (1852 TO 2017)*

摘要

The vascular plants of the Bois Brule River watershed are listed, and over 160 years of change in plant communities observed is described. The watershed covers approximately 51,300 ha in northwestern Wisconsin, primarily in Douglas County with a shortarm extending eastward into Bayfield County. The Bois Brule River travels southwest to the northeast 71 km from its headwaters and drains into Lake Superior. The diverse landscape supports boreal forest, northern mesic forest, northern wet-mesic forest,pine barrens, and other forested and non-forested communities. Five generalized changes in the watershed were noted: (i) the pine barrens community declined by more than 95%, (ii) the northern wet-mesic forest (dominated by Thuja occidentalis) immediately surrounding the river has been reduced to a narrow band, (iii) the large complex of conifer wetlands is greatly reduced, (iv) northern hardwood swamp (dominated by Fraxinus nigra), Alnus incana thickets, and the boreal forest in the lower reaches of the forest have been reduced and converted largely to timber production, and (v) old growth forest has been reduced to less than 1 % of its pre-EuroAmerican settlement extent. A total of 839 vascular plant species have been documented in the watershed, 747 of them during our survey. Additionally, we documented 233 species new to the watershed, of which 53 are new county records and 13 are listed as endangered, threatened, or special concern in Wisconsin. This study has shown that the Bois Brule River watershed harbors a diverse assemblage of plants and is worth further conservation action. It is recommended that additional survey work continue in the future to inform and guide land managers.