Date of Award
Doctor of Philosophy (PhD)
Vegetation-environment relationships were studied in 40 plots located on the slopes and the floodplain within the University of North Dakota Forest River Biology Area in northeastern North Dakota. Three of these plots, each dominated by a different major tree species, were selected for a detailed study (May to October, 1971) of nutrient input by litterfall, throughfall, and stemflow.
Coverage values for 109 species of vascular plants and basal area, frequency, density, and mensuration data were determined for seven tree species. A total of 10 species of mosses and 15 of lichens are reported for the 40 plots.
Dominant (based on importance value) overstory species are Quercus macrocarpa. Tilia americana, and Fraxinus pennsylvanica var. subintegerrima. Subordinate overstory species include Ulmus americana . Acer nequndo. Populus tremuloides . and Betula papyrifera. Tree-ring analysis indicates the present forest is less than 100 years old.
Correlation analysis reveals that the basal area of trees and the number and coverage values of herbaceous species is higher on lower elevations and south exposures. Slope inclination, aspect, and elevation more strongly influence the distribution of the herbaceous element than they do trees and shrubs .
Principal component analysis and Swan-Dix-Wehrhahn ordination were used to group objectively the 40 stands into five abstract community types . Principal component analysis produced similar but more distinguishable groupings than the Swan-Dix-Wehrhahn method.
Environmental soil parameters measured for each horizon within the rooting zone include available water capacity; pH; specific conductivity; cation exchange capacity; percentage organic matter; water soluble calcium, magnesium, sodium, and potassium; replaceable calcium, magnesium, sodium, potassium, strontium, and manganese; available phosphorus; and EDTA-extractable copper, strontium, manganese, zinc, nickel, iron, lead, aluminum, and silicon.
Topographic and soil parameters were used for stepwise- elimination multiple regressions to develop predictive equations for the distribution of plant species. Based on results from multiple regression analysis, gradients for potential solar beam irradiation, available water capacity, elevation, linear aspect, slope, and replaceable potassium were established. Using coverage values, ecological modalities of selected species are demonstrated along the quantified gradients. Generally, trees show a bimodal, shrubs and herbs a unimodal distribution. The distribution of community types along these gradients are also shown. Relationships of stands in several bivariate combinations show patterns of community type distribution resembling those obtained by stand ordination. Whereas pronounced vegetation differences occur between slopes and floodplain, the vegetation pattern on the slopes is continuous and overlapping.
Interception of incident rainfall by the Tilia americana canopy (24.3%) was higher than by the Fraxinus pennsylvanica (12.3%) and Quercus macrocarpa (11.4%) canopies .
Input of calcium, magnesium, potassium, and phosphorus in net rainfall (throughfall plus stemflow) was greatest under the Tilia canopy. and the input of sodium and sulfate was greatest under the Fraxinus canopy.
Although seasonally variable, total litter production, ranging 2 from 247 to 265 g/m for the collecting period, was nearly the same in the three sites studied. Calcium levels were noticeably higher in woody litter, and magnesium, potassium, and phosphorus were higher in non- woody litter. The largest input of mineral elements occurred as follows: calcium, sodium, potassium, phosphorus, strontium, zinc, and copper in the site dominated by Tilia: manganese, iron, and aluminum in the Quercus site; and manganese in the Fraxinus site.
The combined total input by net rainfall and litterfall of calcium, potassium, magnesium, phosphorus, and sodium in kilograms per hectare in the three sites ranged from 39.8 to 68.4 , 22.5 to 37.6 , 8.8 to 9.9 , 5.6 to 10.6, and 17.5 to 20.8, respectively.
It is suggested that functional aspects on productivity and cycling in ecosystems be preceeded by well documented vegetation- environment relationships.
Wikum, Douglas A., "Vegetation of the Forest River Biology Area in Relation to Environmental Gradients and Some Patterns and Processes of Nutrient Cycling" (1972). Theses and Dissertations. 3608.