Lewis F. Ohmann

Contrasting Vegetation Responses Following Two Forest Fires in Northeastern Minnesota

Abstract: Response of Pinus banksiana Lamb, forest communities during the first growing season following a spring fire (three communities) was contrasted with response following a summer fire (two communities) in northeastern Minnesota. Differences in both quantity and quality of vegetation were related to degree of destruction of the forest floor. The spring fire destroyed the litter layer, but left much of the cool, moist lower layers intact, protecting the plant reproductive structures within them. The summer fire consumed virtually all of the warmer, drier forest floor and most of the associated reproductive structures. Reproduction following the spring fire developed vegetatively and prolifically, while that following the summer fire developed primarily from seed and was less abundant. The summer fire also liberated more nutrients from

Biomass distribution of unmanaged upland forests in Minnesota

Abstract A floristic analysis of natural and logged upland forest communities previously identified 12 forest and one non-forest community-types within the Boundary Waters Canoe Area Wilderness of Minnesota. Data collected for the floristic analysis were applied to biomass estimation equations to produce estimates by species for stands within each community-type. Total above-ground biomass was 4 t ha −1 in the non-forest community-type, and ranged from 121 t ha −1 in the jack pine-oak type to 268 t ha −1 in the red pine type. Highest biomass occurred in community-types with long-lived tree species; however, all community-types have similar mean annual biomass increments. Biomass distribution by vegetative strata within and among the community-types was examined. Distribution of biomass among undergrowth strata varied significantly with community-type. Total undergrowth biomass, however, had a narrow range from 1.9 to 4.4 t ha −1 because the biomass for the different strata summed in a compensatory manner. Biomass among vegetative strata were related; an increase in biomass of the tree stratum was related to reduced biomass of lower strata. Such relationships were not sufficient to fully explain variation in biomass of those strata among community-types. Significant differences in biomass among community-types, and the lack of differences among random assignments of the same communities into 12 groups, suggest that the original floristic classification provided a valid basis to compare ecosystem properties.

Vegetative characteristics of five forest types across a Lake States sulfate disposition gradient.

The report presents the vegetative characteristics of the five forest types that comprised the study plots established to test the hypothesis that the wet sulfate deposition gradient across the Lake States is reflected in the amount of accumulated sulfur in soil and tree tissue, which in turn is reflected in tree growth.