PARENT SESSION
Poster Session 37: Forest Ecology.
Thursday, August 5 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.
Additive partitioning of diversity through spatial scales and short temporal span across the Shawnee National Forest, Illinois.
Chandy, Shibi*,1, Gibson, David1, Robertson, Philip1, 1 Southern Illinois University, Carbondale, Illinois, USA
ABSTRACT- We examined the spatial and temporal partitioning of diversity in 367 permanent plots established in ten Research Natural Areas (RNAs), in the Shawnee National Forest of southern Illinois. Diversity (richness, Shannon's and Simpson's indices) was partitioned across spatial scales i.e. within- and among-plots, among-RNAs and between two physiographic regions for three strata of vegetation (trees, saplings, herbs), and with a subset of 67 plots that were resampled seven years later to assess short-term temporal changes. This approach provided a through understanding of the contribution of each spatial scale to regional diversity in the different strata. For all the strata, the highest contribution to diversity (seen with all three indices) was at the two largest scales, i.e. among RNAs and between the two physiographic regions. However, richness was always lower than expected at the plot level for all strata. When the scales of analysis were compared in terms of their percentage contribution to total diversity, Simpson's and Shannon's index were highest at the within-plot scale. The percent contribution identified using Shannon's index however, was higher among-plots and among-RNAs when compared to Simpson's index for all the strata indicating that the more common species are found at these scales. This trend was also seen in the tree and sapling strata in the plots that were resampled after 7-8 years. There was a loss of ≥16% of the herb species in this short time period across the region, but the partitioning of diversity at each scale did not change. Partitioning of diversity for the herb strata was otherwise the same as observed in the tree and sapling strata. Overall, this study indicates that the largest contribution to diversity occurs at the largest scales but, large proportions of common species are found at the smallest scales.
Key words: partitioning, diversity , scales