부산대학교 도서관

Description and classification of natural communities are critical for both theoretical and applied vegetation science, including conservation planning and restoration. The US National Vegetation Classification (USNVC) is a hierarchical system for documentation of natural vegetation within the US. Our goal was to employ an approach consistent with USNVC standards to revise the Associations within the Dry-Mesic Loamy Longleaf Pine Woodland Group (G009), which contains subxeric and mesic longleaf pine (Pinus palustris Mill.) vegetation. We asked: (1) What are the vegetation types that constitute G009 longleaf pine woodlands? and (2) How does species composition of these types vary with soil properties and geography? Beginning with the existing USNVC, based primarily on best professional judgment of vegetation scientists and existing literature, we employed quantitative methods with plot-based vegetation data. We used hierarchical clustering with flexible β on 325 vegetation plots that span the range of variation within G009 longleaf pine woodlands. Misclassified plots were reassigned using silhouette width and fuzzy clustering. Thereafter, clusters were mapped onto existing USNVC Associations based on floristics, environmental conditions, and geography, or new Associations were described. Our analytical framework resulted in identification of 29 vegetation types that span NC, SC, GA, FL, and AL. Of these, 22 were mapped to existing Associations, while seven represented new types. Key environmental variables that relate to compositional differences across Associations include soil texture, soil moisture, soil base cations, and geographic position along north-south and near coast-inland gradients. We documented geographic gradients in community composition that reflect the turnover of dominant taxa, high levels of local endemism and restricted-range taxa, and broad-scale edaphic gradients. Our classification is an improvement on the previous scheme as it provides more detailed information on environmental conditions, geographic extent, and diagnostic taxa for each type, and it describes distinctive, previously unrecognized types. [ABSTRACT FROM AUTHOR]