Abstract
AbstractStanding dead trees, or snags, are an important habitat element for many animal species. In many ecosystems, fire is a primary driver of snag population dynamics because it can both create and consume snags. The objective of this study was to examine how variation in two key components of the fire regime—fire-return interval and season of burn—affected population dynamics of snags. Using a factorial design, we exposed 1 ha plots, located within larger burn units in a south Florida slash pine (Pinus elliottii var. densa Little and Dorman) forest, to prescribed fire applied at two intervals (approximately 3-year intervals vs. approximately 6-year intervals) and during two seasons (wet season vs. dry season) over a 12- to 13-year period. We found no consistent effect of fire season or frequency on the density of lightly to moderately decayed or heavily decayed snags, suggesting that variation in these elements of the fire regime at the scale we considered is relatively unimportant in the dynamics of snag populations. However, our confidence in these findings is limited by small sample sizes, potentially confounding effects of unmeasured variation in fire behavior and effects (e.g., intensity, severity, synergy with drought cycles) and wide variation in responses within a treatment level. The generalizing of our findings is also limited by the narrow range of treatment levels considered. Future experiments incorporating a wider range of fire regimes and directly quantifying fire intensity would prove useful in identifying more clearly the role of fire in shaping the dynamics of snag populations.
Highlights
Standing dead trees, or snags, may proceed through many stages of decay before toppling or decaying completely
Not all snags are useful to cavity-nesting birds, with many species showing a distinct preference for excavating nest cavities in snags of a certain decay state (Runde and Capen 1987)
In recognition of the importance of snags for cavity-nesting birds and other wildlife, management plans for public lands often identify desired densities of snags for different forest types. Achieving these goals requires that land managers understand the factors that shape snag population dynamics; in particular, managers need to understand the causes of variation in recruitment to the population of standing dead trees, decay rate, and mortality
Summary
Snags, may proceed through many stages of decay before toppling or decaying completely. In pine forests of the southeastern United States, several bat species rely on cavities in snags as roost sites, and many other mammals use cavities as dens (Loeb 1993). In recognition of the importance of snags for cavity-nesting birds and other wildlife, management plans for public lands often identify desired densities of snags for different forest types. Achieving these goals requires that land managers understand the factors that shape snag population dynamics; in particular, managers need to understand the causes of variation in recruitment to the population of standing dead trees, decay rate, and mortality (i.e., falling or decaying to the point that they can no longer be used as nest sites)
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