PARENT SESSION
Oral Session # 62: Biodiversity I.
Presiding: P Baker
Thursday, August 7. 8:00 AM to 11:30 AM, SITCC Meeting Room 100.
Fine-scale species-area relationships of the vascular flora of the Southeast.
Fridley, Jason*,1, Gramling, Joel1, Jobe, R1, Kaplan, Jessica1, McKnight, Meghan1, Senft, Amanda1, Vandermast, David1, Peet, Robert1, 1 University of North Carolina at Chapel Hill, Chapel Hill, NC
ABSTRACT- Species-area relationships at fine scales (0.1 ha and below) have been neglected by ecologists, both for lack of appropriate data and the perception that they are unrepresentative of larger-scale diversity patterns. We reassessed the meaning and importance of fine-scale species-area relationships using the extensive database of the Carolina Vegetation Survey (NC and SC, USA), including over 1300 plots with values of floristic richness at each of 6 areas regularly spaced on a log-10 scale, from 0.01 to 1000 m2. Contrary to the expectation that the standard Arrhenius function does not fit fine-scale data, our data closely fit a straight line in log(species) vs. log(area) space (as opposed to semi-log space), and log-log slope (z) values fell within a narrow range (0.2-0.4) despite a 30-fold range in 0.1 ha richness. Variation in z between plots was largely a function of richness at the smallest scale (0.01 m2), which was itself influenced by vegetation type, edaphic gradients, and, most importantly, mean size of individuals. When the slope of each area-richness transition was examined separately, the 0.1 to 1 m2 transition consistently had the highest rate of species accumulation, with each subsequent transition accumulating slightly fewer species in log-log space. When estimates of state, continental, and global levels of floristic richness were added to our results, a Preston-type triphasic curve emerged. We suggest that 1) fine scale species-area relationships are remarkably consistent and are indicative of small-scale individual density patterns; 2) triphasic species-area curves should be expected from fine scales to the globe; and 3) the first inflection point of the triphasic curve, where the density constraint disappears, is commonly above the 0.1 ha scale in floristic data.
Key words: species-area curve, diversity, vegetation, nested sampling