Vegetation-environment relationships were studied in forest stands located on slopes and a floodplain in northeastern North Dakota. Coverage values of all vascular plants and basal area, frequency, density, and mensuration data for tree species were obtained. A total of 109 species of vascular plants, 10 of mosses, and 15 of lichens are reported for the 40 plots studied. The three most important (based on importance value) overstory species are Quercus macrocarpa, Tilia americana, and Fraxinus pennsylvanica var. subintegerrima. Less important overstory species include Ulmus americana, Acer negundo, Populus tremuloides, and Betula papyri/era. Tree-ring analysis indicates that the present forest is less than 100 yr old. Correlation analyses were made between community characteristics of vegetation and the topographic parameters, slope inclination, aspect, and elevation. Principal component analysis and Swan-Dix-Wehrhahn ordination were used to establish five abstract community types.Environmental soil parameters measured for each soil horizon within the rooting zone include available water capacity; pH; electrical conductivity; cation exchange capacity; percentage organic matter; replaceable Ca, Mg, K, Na, Sr, and Mn; available P; and, EDTAextractable AI, Cu, Fe, Mn, Ni, Pb, Si, Sr, and Zn. Topographic and soil parameters were used for stepwise elimination multiple regressions to develop predictive equations for the distribution of plant species.Correlation analysis reveals that the basal area of trees and number and coverage values of herbaceous species is highest on lower elevations and south exposures. Whereas pronounced vegetation differences occur between slopes and the floodplain, the vegetation patterns on the slopes are continuous and overlapping. Based on the results from multiple regression analysis, gradients for potential solar beam irradiation, available water capacity, elevation, linear aspect, slope inclination, and replaceable K were established. By use of coverage values, ecological modalities of selected species are demonstrated along quantified gradients. Relationships of plots in several bivariate combinations show patterns of community type resembling those obtained by stand ordination.
