U.S. Joint Fire Science Program


Date of this Version


Document Type



Final Report: JFSP Project Number 11-3-1-22


US government work.


The effects of edge on ecosystems is well documented on animal and plant species, as well as a number of ecosystem attributes. A substantial determinant of ecological edge effects is the effect of edge on microclimate parameters such as temperature and humidity. These effects have been described in detail in upland communities, but not in wetland forests. Of particular interest is whether hydrologic influence trumps edge effect; in other words, does the influence of inundation create a hydrologic “switch” that overwhelms edge effect? In a landscape with numerous wetland forest patches subject to seasonal hydrologic fluctuations, I measured microclimate in relation to edge distance during drought and inundation to determine the relative influence of edge effect on microclimate under contrasting hydrologic conditions. I also tested whether the occurrence of wildfire in the study area two years prior had lasting influence on edge-related microclimate. Predictions of edge effect on microclimate were observed in both wet and dry conditions, and in patches that were burned as well as unburned patches. While evidence did not indicate the presence of a hydrologic “switch” controlling the influence of edge, a stronger edge effect occurred during dry conditions than during inundation. Also, while sites experienced relatively little difference in edge influence on microclimate from fire after two years of recovery, the influence of edge effect under dry conditions compared to inundation was greatly magnified in burned patches compared to unburned patches. These findings suggest that under scenarios of warmer, drier conditions, the edge effects seen in this study could be increasingly important in providing refugia for humidity-sensitive plant species. Additionally, the gradient of sizes in which these measurements were taken may allow variably-sized cypress domes to be used as proxies for varying scenarios of future altered climate in seasonallyinundated wetlands.