Stomatal Distribution and Post-fire Recovery: Intra- and Interspecific Variation in Plants of the Pyrogenic Florida Scrub, 2023-2024

Premise of the study: Amphistomy is the presence of stomata on both leaf surfaces. This distribution of stomata can increase photosynthesis, but is relatively infrequent, which is often attributed to high costs such as water loss. This study takes place in the Florida scrub- a hot, dry, shrub-dominated habitat that naturally experiences fire. However, decades of anthropogenic suppression and the reintroduction of controlled burns has created varied fire regimes across the region. In this study, we investigated the links between amphistomy and fire by determining (1) how common the trait is in this habitat, and (2) within-species variation before and after experimental fire, and across a time-since-fire gradient (0.25 - 50 years).  Methods: We (1) surveyed 116 plant species across scrub habitats for amphistomy presence, and  (2) experimentally and observationally investigated intraspecific variation in stomatal traits in response to fire for two post-fire resprouting species of palmetto, Serenoa repens and Sabal etonia (Arecaceae).  Key results: Amphistomy was present in 62.9% of all surveyed species and 85.7% of post-fire obligate reseeders, suggesting amphistomy may be beneficial in this group and in the Florida scrub conditions. The stomatal ratio (upper/total stomatal density) was generally stable in response to fire. Stomatal density decreased following fire in S. etonia, with both species experiencing high variation in the post-fire years.  Conclusions: Amphistomy is common in this habitat and relatively stable within species in response to fire, while stomatal density responds plastically during postfire regrowth.