Date of this Version
Final Report: JFSP Project No.: 05-2-1-88
The response of plants and animals in the pine forests of southern Florida to variation in fire and hydrological regimes remains inadequately described, hindering the ability of resource managers to manipulate fire and water to achieve desired ecological outcomes. In this study, we took advantage of natural variation in two measures of fire history (the number of days since last fire and the number of times an area had been burned during the previous ten years) and one measure of hydrology (water table elevation) to explore how plants, breeding birds, and wintering birds in slash-pine (Pinus elliottii var. densa) forests responded to variation in fire and water levels. At the largest spatial scale, considering samples taken from 441 points located across the range of slash pine in south Florida, variation in the structure and composition of the plant (72% of the explained variation) and both bird assemblages (73% and 80% of the explained variation in the breeding- and wintering-bird assemblages, respectively) is driven primarily by variation in water-table elevation, with the remainder explained by fire history. The relative importance of hydrology was also apparent when examining variation in plant and bird assemblages at a smaller spatial scale. Within study sites, local variation in water-table elevation drove variation in structure and composition of vegetation at 5 of 7 sites, of breeding-bird assemblages at 4 of 7 sites, and of wintering birds at 7 of 7 sites. However, the responses of individual components of vegetation and individual bird species at this smaller scale were not always concordant with patterns observed at the larger spatial scale. Indeed, the effects of variation in water-table elevation that emerged at the smaller scale often ran counter to the effects described at the larger scale. The within-site effects of fire, although generally less important than those associated with variation in water level, were more consistent with patterns described at the larger scale. At both scales of observation, areas burned more recently and frequently tended to contain short, sparse understories and had more standing dead trees, an important component of habitat for several bird species. As expected within a fire-dependent ecosystem, no bird species were associated with fire-suppressed conditions, although most species were able to tolerate fire-return intervals as long as 5 years without any significant effect on abundance.
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