PARENT SESSION
Poster Session # 14: Forest Ecology.
Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
The influence of ericaceous shrubs on forest floor and soil properties in the southern Appalachians.
Clinton, Barton1, Horton, Jonathan2, Nilsen, Erik2, 3, Walker, John2, Beier, Colin4, 1 USDA Forest Service Southern Research Station, Otto, NC, USA2 Department of Biology, Blacksburg, VA, USA3 Botany Department, Honolulu, HI, USA4 Institute of Arctic Biology, Fairbanks, AK, USA
ABSTRACT- In the southern Appalachians, evergreen shrub-dominated understories interfere with woody seedling establishment. Several sources of inhibition have been studied including influences of soil and forest floor properties. In this study we examined how soil and forest floor properties vary along gradients of evergreen shrub basal area (BA). On three sites, we established transects that transitioned between open understories and understories with varying densities of Rhododendron maximum (rosebay rhododendron) and Kalmia latifolia (mountain laurel). The three sites were a mid-elevation ridge (DF), a low-elevation cove (BF), and a high-elevation southwest-facing slope (WS). A total of 60 2 x 2 m plots were randomly established along transects on each site. For each plot we quantified soil chemical properties and forest floor mass, carbon, and nitrogen as they related to evergreen shrub presence and BA. On sites occupied by mountain laurel, humus and litter C increased and soil pH decreased with increasing mountain laurel BA at DF, but little or no differences in soil cations were found. Across all sites with rhododendron, soil Al was in greater supply and soil P was in shorter supply. On BF and WS, litter and humus depth and mass, and humus C increased with increasing rhododendron BA. On WS, humus N and litter C increased, as well. However, litter N and soil pH decreased. Across all sites, approximately 80% more C and 30% more N was contained within humus beneath rhododendron, and approximately 75% more C and 20% more N in litter compared to the other two understory conditions examined. There were no differences in litter bulk density across sites; however, humus bulk density was significantly lower by nearly 50% beneath rhododendron. These results help characterize spatial heterogeneity in forest floor and soil prperties across differing understory conditions that could potentially explain variation in seedling success.
Key words: kalmia latifolia, rhododendron maximum, forest floor, southern appalachians