Effects of clear-cutting and fire on the succession of tree species in northern lower Michigan.

Abstract

Following clear-cutting and fire, the change in species composition through time is the process of succession. This study follows the change in tree species abundance and distribution after fire by examining two experimental burn plots (burned 1948 and 1980) and a plot from the surrounding forest that was burned by natural fires in 1911; all plots were clear-cut shortly before burning. Tree taxa within each plot were censused, categorized by age class and characterized as either shade-tolerant or shade-intolerant. In addition, species diversity indices were calculated for both the adult trees separately and all individuals collectively for each plot. Canopy cover was also measured. We found a dominance of shade-intolerant adult trees in the 1980 burnplot, and a dominace of shade-tolerant seedlings in the understory. In the 1948 plot we found that there was no statistically discernible difference in the distribution of shade-intolerant and shade-tolerant taxa for the adult trees, but a dominance of shade-tolerant species in the understory. Shade-tolerant adults and seedlings dominated the 1911 plot. This suggests that there are stages to succession: shade-intolerant species (early successional) are more suited for colonization of open spaces following a disturbance; however, these taxa are not able to reproduce and are replaced by shade-tolerant species (late successional). This provides further evidence for the facilitation model suggested by Connell and Slayter (1977). We also found that species diversity increased as years after fire increased for the adults and peaked in the 1948 plot when all individuals were considered. Finally, we found that canopy cover increased from the 1980 plot to the 1911 plot.