PARENT SESSION
Poster Session 19: Biodiversity
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Converting Variable Area Plot Data to Fixed Area Estimates of Species Richness.
Fan, Weihong*,1, Waring, Richard2, 1 Richard Stockton College of New Jersey, Pomona, NJ2 Oregon State University, Corvallis, OR
ABSTRACT- With the objective of mapping tree species richness across the U.S.A. at a spatial resolution of 1000 km2, we drew upon Federal Inventory Analyses (FIA) surveys made across 66 forest ecoregions. The original surveys were conducted using prisms to estimate the basal area per acre of all tree species. Prism cruising is efficient but bias toward counting species of above average diameter. Recently, fixed area (1/6 acre) sampling has been introduced into the surveys in some states. To utilize the original, more extensive data acquired with prisms we compared estimates of tree richness on both fixed- and variable-area plots by selecting ecoregions where adequate samples were available (> 19 plots /1000 km2 of each type, and > 200 samples within an ecoregion). To estimate total tree richness in an 1000 km2 cell we derived logarithmic functions (r2 > 0.95) that define the average increase in species number with increasing number of plots and increasing number of trees counted on all plots within each cell from fixed area plots. These equations were applied to variable area plots with an adjustment factor as a function of tree basal area, which allow appropriate predictions of relative species richness of each 1000 km2 cell within ecoregions.
Key words: tree species richness, species area curve, species diversity, FIA database