PARENT SESSION
Oral Session #74: Spatial Ecology: Models and Methods. Presiding: C. Loehle.
Friday, August 10, 2001. 8:00 AM to 11:30 AM. Hall of Ideas E.
The spatial scaling of rare plant distributions.
Kunin, William1, Hartley, Stephen1, Lennon, Jack1, 1
ABSTRACT- The measurement of species abundance or rarity depends greatly upon the spatial scale of analysis. Species distributions measured at different scales of resolution reflect biologically different aspects of abundance, from geographic range down to local density or population size. It would be valuable to be able to describe and predict abundance across a range of scales. Earlier work suggested that this may be possible, especially where species have approximately fractal distributions. To test such notions, we have combined national database information with detailed field surveys to examine the distributions of 12 rare or scarce British plant species over scales ranging from 10's of km down to 10's of cm. Surveys were performed on progressive subsamples of areas occupied by each species at progressively finer scales. We found that species distributions displayed consistent (but not precisely fractal) scaling properties over ranges of scales, suggesting that cross-scale extrapolations may be possible. However, there appears to be an abrupt discontinuity in scaling behavior at intermediate scales. This scaling shift may either reflect the "footprint" of human land use patterns, or it may indicate a hierarchical set of processes acting on species at different sets of scales.
KEY WORDS: spatial scale, species distributions, fractals , rarity