Wednesday, August 4, 2010

PS 57-105: Using species area curves to examine spatial scale of pine savanna understory vegetation

Monica R. Hamberg, University of South Florida

Background/Question/Methods

The understory of pine savannas are diverse and interesting habitats but little is known about the spatial scale of these habitats and how it changes over space. Species richness of an area can be studied in order to examine patchiness and other spatial parameters. This research can have important implications for land managers as well as community ecologists and biogeographers.

Research was conducted at the University of South Florida Ecological Area, an area greater than 300 hectares. This study was confined to sandhill habitat within the Ecological Area in which controlled burns have been conducted in partitioned burn plots and assigned burn regimes of every one, two, five, or seven years and also never burned.

Data were collected in two surveys, Spring & Fall 2009. Observations of species richness were taken at  1m x 1m quadrats every 30 meters along  transects running north & south in all burn plots.

Species richness can be obtained by creating Species Area Curves. Type IIIA and Type IIIB species area curves were created for all plots and the Ecological Area as a whole. Type IIIA curves are spatially explicit and examine change in richness with the size of plots. Type IIIB curves ignore spatial information and examine richness change with the number of plots. Type IIIB curves can also be used to examine and compare plots of the same burn regime. To date, Type IIIA curves have not been found in any  literature regarding species area curves.  

Results/Conclusions

Unburned plots exhibit steeper slopes and lower intercepts in the Species Area Curves than all other plots. This suggests that unburned plots always have fewer species but that these unburned areas acquire species at a faster rate. If it were possible to extrapolate to a larger scale of study, it is plausible  that there are more species in unburned areas, suggesting that fire and controlled burns may produce homogenous areas over time. These findings may have valuable implications in land management and controlled burn regimes.