Classification Of Oak Ecosystems In Southeastern Michigan.

Abstract

An ecological multifactor approach was used to classify oak ecosystems in an area of approximately 19,000 km$\sp{2}$ in southeastern Michigan. Eleven upland and one wetland ecosystems were identified in the field using reconnaissance, plot sampling, and test mapping. Each ecosystem was a characteristic combination of physiography, soil, and climax vegetation (overstory and ground cover vegetation). The classification approach relied to a great extent on physiographic and soil variables so that it could be used in disturbed areas. Black oak (Quercus velutina Lam.), white oak (Quercus alba L.), and red oak (Quercus rubra L.) were the most abundant species found in the upland ecosystems. Red oak occurred on dry-mesic to mesic sites and black oak was restricted to dry sites. White oak had a large ecological amplitude occurring on dry to mesic sites. Swamp oak (Quercus bicolor Willd.) and bur oak (Quercus macrocarpa Michx.) were characteristic of the wetland ecosystem. Canonical variates analysis was used to examine the distinctness of the upland ecosystems. Discriminant analyses were conducted to compare the error rates of different ecosystem components. The misclassification rates using all ecosystem components (physiography, soil, ecological species groups, and overstory vegetation) were the lowest: 19.6% in highly dissected terrain and 34.3% in flat to gently rolling topography. Thirteen ecological species groups were developed by using 68 herbaceous and shrub species. A continuum of groups from very dry to wet sites were identified. Some groups had a relatively broad range of soil moisture and fertility, whereas others were relatively narrow in their requirements. Nine groups were judged useful to help identify ecosystem types in the field. The vigor of oak and hickory trees of the upland oak ecosystems was estimated. Four individual tree characteristics were used: crown condition, epicormic branching, crown ratio, and periodic basal area increment. Tree vigor was generally lower in dry ecosystems with coarse-textured soils compared to moist ecosystems with fine-textured soils. Tree mortality was low in all ecosystems. In the event of a major insect or disease outbreak, low vigor trees will probably sustain more damage than healthy, vigorous trees.