An Ecological Analysis of the Sand Dune Complex in Point Beach State Forest, Two Rivers, Wisconsin

Abstract

1. A descriptive and interpretive analysis of the vegetation and physiographic and edaphic conditions of the open dune region and the series of forested Post-Nipissing beach ridges and sloughs at Point Beach State Forest, Two Rivers, Wisconsin, was made by means of qualitative and quantitative data. The open dunes were studied by quadrat sampling of vegetation and line-intercept analysis along transects from lake to forest margin. The tree, shrub, and herbaceous layers of the wooded ridges were sampled by series of nested quadrats. Soil profiles were analyzed in the open dunes and in forest areas. 2. Beach grass, sandreed grass, and dune-building shrubs are characteristic of the more exposed habitats with sandreed grass as the chief blowout colonizer. The widespread little bluestem association constitutes an important seral stage following stabilization of actively moving sand. Mat-forming woody plants also close over the open sand until both communities are overshadowed by a shrubby stratum of ground juniper along the forest margin. 3. Correlations between diverse dune environments and variations in ecological amplitude of the various dune species permit successful growth of some type of vegetation in each of the dune habitats. As the present foredune barrier to wind activity seems able to withstand high-level wave erosion, the open dune area may well be on its way to progressive plant succession and to stabilization. 4. While the forest vegetation exhibits a marked heterogeneity in every stratum, particularly the herbaceous, there is an over-all uniformity in that the same diversified vegetation occurs in a clumped, irregular, and sometimes discontinuous distribution throughout the forest. 5. Dominant trees in the young forest canopy (70-85 years old) are white pine, hemlock, paper birch, and red maple, while red pine, white cedar, and yellow birch are of secondary importance and red oak occurs as an understory tree. Both the occurrence and type of shrub and herbaceous vegetation correspond to the nature and density of the arborescent stratum. 6. Both field observations and historical evidence indicate that a long-established vegetation was destroyed by heavy cutting and fire within the last century. At present the entire forest seems to be in the same general secondary successional stage and shows signs of good recovery. 7. The slough vegetation is subject to irregular progressions and regressions correlated with precipitation and lake-level fluctuations within an over-all successional progression from open water through sedge and thicket stages to early trees. 8. At present the forest exhibits features of the pine-hemlock complex of sandy podzol soils and of the hemlock-red maple communities intermediate between bog and developed hemlock-hardwood forests. The climax could conceivably be some gradient pattern combining elements of both types. 9. Apart from some variations arising from different geographic locations and the greater age and taller formations of the southern shore dunes, the Point Beach area is similar to these dunes in beach-ridge origin, in processes of dune development and stabilization, in the characteristics of vegetation and soil, and in retrogressive stages resulting from windthrow, cutting, and fire.