PARENT SESSION
Poster Session # 21: Biogeography, Biodiversity, Populations, and Genetics.
Thursday, August 7 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Nested versus non-nested characterization of vegetation composition and species richness at multiple spatial scales.
Wentworth, Thomas*,1, White, Peter2, Wheeler, Brooke2, Taverna, Kristin2, Kuppinger, Dane2, Jacobs, Lee Anne2, Fridley, Jason2, Peet, Robert2, 1 North Carolina State University, Raleigh, NC2 University of North Carolina, Chapel Hill, NC
ABSTRACT- The importance of characterizing vegetation composition and species richness at multiple spatial scales is increasingly recognized by ecologists, but there is no consensus as to whether variation with scale is best characterized by subplots arranged in a design that is nested or non-nested. Many crucial aspects of biodiversity management and research may depend on this design choice. The fundamental difference between these designs is in how they are influenced by spatial autocorrelation structure and in how well they allow characterization of change in vegetation structure with change in grain of observation. We compared nested and non-nested designs for characterizing species richness (as species-area and species-accumulation curves) of vascular plants using data collected by the Carolina Vegetation Survey in 0.04 ha plots. If the goal is to provide a strategy to inventory all species in a large plot, neither design presents a clear advantage. Although either design can be used to examine species-area relationships, the nested design constrains the result to the desired monotonic response for each replicate. The non-nested design is superior when the goal is to find as many species as possible within a specific subsample of a larger target area. The nested design offers a means to interpret underlying spatial patterns of richness that the non-nested design does not. Only the nested design is appropriate if the goal is to assess changes in species composition with changing grain size of observation, because the non-nested design confounds the influence of grain with that of extent. We also explored the complex question of which design allows more effective extrapolation of richness to larger spatial extent. We conclude that the nested design is equivalent or superior to the non-nested design for most applications and should be the standard method for multi-scale inventories.
Key words: species-accumulation curves, non-nested inventory design, species-area curves, nested inventory design