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A nested-intensity design for surveying plant diversity.
Barnett, David1, Stohlgren, Thomas1,2, 1 2
ABSTRACT- We tested a nested-intensity design for the inventory of vegetation diversity using three sample designs: a 1000-m2 multiple-scale plot (n = 8), a 100-m2 multiple-scale Intensive plot (n = 15), and a 100-m2 single scale Extensive plot (n = 28). We assessed local and regional heterogeneity of plant species diversity in aspen stands in a Southern Colorado mountain range. As expected, the large Modified-Whittaker plot recorded greater species richness per plot than the other techniques (p < 0.001), but also captured locally rare species missed by the smaller plots. The Intensive plots extended the environmental gradient sampled (17 unique species), and improved species-area calculations. The Extensive plots further expand the gradient sampled (18 unique species), and located species-rich areas otherwise undetected. Multiple linear regressions were able to predict the slope of species-area curves (adj R2 = 0.643, p < 0.001) at the Extensive plots, species rich locations have steeper species-area curves and identifying might require monitoring and further sampling. Species accumulation curves based on the extensive, single scale plot techniques might be very misleading. A combination of techniques greatly improves our understanding of native and exotic plant diversity patterns.
KEY WORDS: diversity, inventory, heterogeneity