Eric Heitzman

Changes in plant species composition along an elevation gradient in an old-growth bottomland hardwood Pinus taeda forest in southern Arkansas1

Abstract Grell, A. G. (Arkansas Forest Resources Center, School of Forest Resources, University of Arkansas-Monticello, Monticello, AR 71656-3468), M. G. Shelton (USDA Forest Service, Southern Research Station, Monticello, AR 71656-3516), and E. Heitzman (Arkansas Forest Resources Center, School of Forest Resources, University of Arkansas-Monticello, Monticello, AR 71656-3468). Changes in plant species composition along an elevation gradient in an old-growth bottomland hardwood-Pinus taeda forest in southern Arkansas. J. Torrey Bot. Soc. 132: 72–89. 2005.—Old-growth bottomland hardwood-Pinus taeda L. forests are rare in Arkansas, and the complex relationships between plant communities and environmental conditions have not been well described in these forests. To investigate these relationships, a digital elevation model was developed for a 16.2 ha old-growth bottomland hardwood-Pinus taeda forest in southern Arkansas. Overstory trees, saplings, seedlings, and herbaceous plants were analyzed in three 0.5 m elevation classes and by using indirect gradient analysis. Information was also collected on site factors (canopy cover, forest floor litter cover, and elevation), soil physical factors (bulk density and soil texture), soil moisture, and soil chemical factors (pH, electrical conductivity, organic matter, N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, and Na). Importance values for 35% of seedling species, 30% of overstory species, 22% of herbaceous species, and 8% of sapling species differed significantly by elevation class. Significant differences by elevation in species diversity, richness, and evenness were identified in the seedling stratum, while only sapling evenness differed by elevation. Seventy-four percent of the environmental characteristics produced significant differences by elevation except for soil texture (sand, silt, and clay), September soil moisture content, Mn, and Cu. Seventy percent of environmental variables were significantly correlated with elevation. Dominant environmental influences on species composition in all strata included elevation as well as many other correlated variables such as Fe, forest floor litter cover, bulk density, and Na. Results from this study suggest that differences in vegetation were primarily the result of subtle elevational variations. Restoration or management of these forests should carefully consider microtopographical influences.

Stand Dynamics of an Old-Growth Eastern Hemlock-Hardwood Forest in West Virginia

ABSTRACT: Cathedral State Park (CSP) is a 54-ha, old-growth, eastern hemlock-hardwood forest located in the central Appalachian Mountains of West Virginia. Hemlock woolly adelgid (HWA) (Adelges tsugae Annand) is an exotic insect that currently threatens eastern hemlock (Tsuga canadensis (L.) Carr.) in its native range, and was found in CSP in 2002. In 2006, field plots established in 2000 were re-measured to assess adelgid-induced changes to forest structure and species composition. The herbaceous plant community was also measured during the 2006 growing season to describe how the ground flora has changed since it was originally surveyed in 1965. In addition, characteristics of snags and downed dead wood in CSP were compared to published data on 25 old-growth hemlock-hardwood stands in the eastern United States. From 2000 to 2006, little HWA-induced change occurred in CSP. Density and basal area of overstory hemlock did not change, while snag density and basal area decreased over time. However, more than 10% of measured overstory hemlock trees were infested with HWA, with plot infestations ranging from 0 to 93% of stems. CSP had 1.5 times the volume of downed dead logs compared to other old-growth hemlock-hardwood stands. This study serves as a reference of forest structure and species composition in CSP prior to HWA-induced mortality.