Changes in tree species importance following harvesting disturbance in north Mississippi between 1967 and 1994This article is part of a larger document. View the larger document here.
We used continuous forest inventory data from the Forest Inventory and Analysis unit of the U.S. Department of Agriculture, Forest Service to study the impacts of timber harvesting on species composition and species importance in a 26-county region in north Mississippi. The region was 59 percent forested and contained 1 965 223 ha of timberland. There were 524 upland sample plots on a 4.8 by 4.8 km square grid. These were measured in 1967 and remeasured in 1977, 1987, and 1994. Across the period, only 110 plots had < 5 percent of basal area removed. In 1967, on these undisturbed plots, Pinus echinata Mill., Carya spp., Quercus falcata Michx., and Q. alba L. were the top four overstory ranking species in terms of basal area, accounting for 13.8, 12.7, 10.6, and 9.9 percent of basal area, respectively. Upon final remeasurement of these same undisturbed plots in 1994, Q. alba had become dominant and was followed by P. echinata, Q. falcata, and Liquidambar styraciflua L. In contrast, the total 1994 plot population, which included both disturbed and undisturbed plots, was strongly dominated by P. taeda L., which accounted for 22.4 percent of basal area. In stands that had > 75 percent of basal area removed, P. taeda accounted for > 50 percent of stand basal area. It appears that harvesting disturbance and management preferences has resulted in an alteration of the normal trajectory of species composition dynamics. P. taeda is now the dominant species and the dominant overstory softwood across the uplands of north Mississippi. This appears to be markedly different than what would occur naturally as evidenced by the dominance of Q. alba on the undisturbed plots. There were also noteworthy differences in understory species composition; most notably P. taeda was dominant on disturbed plots and Cornus florida L. was dominant on undisturbed plots.