Composition and structure of Tsuga caroliniana stands in the Southern Appalachian Mountains

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
Marcus Wind (Creator)
Western Carolina University (WCU )
Web Site:
Laura DeWald

Abstract: Tsuga caroliniana Engelm. (Carolina hemlock) is a foundation species, so it defines a stand and its specific traits control ecosystem dynamics. This study presents an investigation into the relationships between Tsuga caroliniana physiography, population, and community characteristics by describing them across the landscape where it is currently found in North Carolina and Tennessee. The three specific questions asked were: (1) Does the physiography where Tsuga caroliniana is found vary? (2) Do community density, size, and diversity of Tsuga caroliniana stands vary? (3) Is variation in Tsuga caroliniana age, density, and size related to the variation in physiography and/or community density, size, and diversity? To address these questions, twenty 0.05 ha plots were installed in Tsuga caroliniana stands at five different sites on National Forest lands in the southern Appalachian Mountains of North Carolina and Tennessee. Sampling included the physiographic variables (aspect, elevation, landform index, and terrain shape index) and community variables (summer and winter canopy density, canopy percentage evergreen, mean diameter at breast height, importance values, species richness, evenness, diversity, percent ground cover of shrubs, and stem density of all trees and snags) which were used to address whether there was variation between the study sites and if they were related to variations in Tsuga caroliniana age, density, and size. Variation among the variables were analyzed using ANOVA, the Tukey test was used to separate means for establishing patterns of deviation among sites and species, and regression analyses were used to examine relationships between Tsuga caroliniana and stand characteristics. At one site, Dobson’s Knob, stands were higher in elevation, faced a different direction, and were in shallower depressions compared to the other sites. Stands at Dobson’s Knob also had the lowest summer canopy density and overstory mean diameter, and the highest overstory mean Tsuga caroliniana diameter. Another site, Lost Cove, had lower overstory species richness and lower over- and understory diversity, but it had a high percent of older and larger Tsuga caroliniana stems. Patterns in variables measured at both the overstory and regeneration level were different. Species richness and diversity varied among sites for the overstory (p = 0.0054, and p = 0.0015) and regeneration levels (p = 0.0168, and p = 0.0011), but evenness did not (overstory: p = 0.1540; 0.70 ± 0.15, regeneration: p = 0.5577; 0.76 ± 0.46). The percentage of the live trees that were Tsuga caroliniana varied among sites at the overstory level (p = 0.0090), but not at the regeneration layer (p = 0.1080; 3.29 ± 5.53). The density of Acer rubrum varied from eight other species in the understory (p = 0.0611), but did not at the overstory level (p = 0.3690; 32.5 ± 24.8). With shrubs, species richness varied (p < 0.0001), but percentage ground cover did not (p = 0.7660, 20.70 ± 25.68). The best sites for the artificial regeneration of Tsuga caroliniana occur within an aspect range from north to northwest, an elevation range from 900 m to 950 m, and a TSI range from -0.6 to 0.2, and have Ericaceae shrubs in the understory, a LFI of one, and a summer canopy density around 90 percent. This research suggests that Tsuga caroliniana needs a more southerly exposure at higher elevations, and it adds to the body of evidence confirming the stress tolerant life history strategy of Tsuga caroliniana and the suppress effect on establishment of other species by Rhododendron maximum.

Additional Information

Language: English
Date: 2021
Carolina hemlock, Carolina hemlock stands, composition and structure, southern Appalachian Mountains, Tsuga caroliniana, Tsuga caroliniana stands
Carolina hemlock
Mountains -- Appalachian Region, Southern

Email this document to