PARENT SESSION
Oral Session #75: Plant Communities: Vegetation Analysis. Presiding: J. Fralish.
Friday, August 10, 2001. 8:00 AM to 12:00 PM. Hall of Ideas F.

The robustness of physiologically based functional groups in Florida scrub.

Foster, Tammy¹, Brooks, J. Renee², ^{1 2}

ABSTRACT- In order for functional groups of species to be useful for scaling or modeling activities, they need to meet two criteria: (1) an easy-to-measure morphological indicator of function and (2) the groupings need to be temporally and spatially robust. In this study, we examined whether physiologically based functional groups of twelve Florida scrub species adhered to the aforementioned criteria. Cluster analysis was used to group scrub species in a fire-maintained plot based on their physiological function. These functional groupings were then compared to morphological groupings based on either life form or leaf characteristics (specific leaf area and leaf thickness). Although some trends existed between the physiological responses and leaf characteristics (e.g. variation in leaf thickness explained 31.9% of the variation in ¹³C (p = 0.089)), there was no agreement between the two groupings. However, life form classifications were good indicators of physiological function. Data were collected in the same fire-maintained plot for two consecutive years, to determine the temporal robustness of the functional groupings. For both years evergreen trees, vines, palmetto, and shrubs clustered into distinct groups. Data were also collected on a subset of species at three sites to determine spatial robustness. Long-term gas exchange measurements (¹³C and %N) were found to be spatially robust, while instantaneous measurements (A_max, g_max, dark respiration) were not.

KEY WORDS: functional, group, physiology, Florida