Browsing by Subject "fire frequency"

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    Data for fire regime shapes butterfly communities through changes in nectar resources in an Australian tropical savanna, 2019-2020
    (2023-08-03) Leone, Julia B; Larson, Diane L; Richards, Anna E; Schatz, Jon; Andersen, Alan N; jleone@fmr.org; Leone, Julia B
    We studied responses of butterflies, vegetation structure, and floral resources to fire regime at a long-term fire experiment near Darwin in the Australian tropical savanna. This dataset consists of data collected during the 2019/2020 wet season at 18 1-ha plots in three blocks, where each block contains six randomly assigned fire treatments. We measured butterfly, vegetation structure, and floral resources data, and collected fire regime data. These data are associated with Leone et al. (2023). Fire regime shapes butterfly communities through changes in nectar resources in an Australian tropical savanna. Ecosphere. Along with its associated paper, we hope these data will provide helpful information for those working in fire management, butterfly conservation, and biodiversity conservation more broadly.
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    Prescribed fire in oak savanna: Fire frequency effects on stand structure and dynamics
    (2001) Peterson, David W; Reich, Peter B
    Although it is well known that fire can exert strong control on stand structure, composition, and dynamics in savannas and woodlands, the relationship between fire frequency and stand structure has been characterized in few of the world's savanna and woodland ecosystems. To address this issue in temperate oak-dominated ecosystems, we studied the effects of fire frequency on stand structure and dynamics in oak savanna and woodland stands that had been burned 0–26 times in 32 yr, in the Anoka Sand Plain region of Minnesota (USA). Seedling densities declined with increasing fire frequency, but differentially, for northern pin oak (Quercus ellipsoidalis), black cherry (Prunus serotina), serviceberry (Amelanchier sp.), and red maple (Acer rubrum). Bur oak (Q. macrocarpa) seedling density was not sensitive to fire frequency. Frequent burning (at least three fires per decade) prevented development of a sapling layer and canopy ingrowth. Low-frequency burning (fewer than two fires per decade) produced stands with dense sapling thickets. Reductions in overstory density and basal area from 1984 to 1995 were observed for all stands burned two or more times during that period. Basal area declined by 4–7% per year, and density declined by 6–8% per year in stands burned four or more times. Mortality rates in burned stands were higher for northern pin oak (50%) than for bur oak (8%). Northern pin oak mortality was highest for small trees (< 20 cm dbh) and lowest for mature trees (30–40 cm dbh); mortality increased with fire frequency. Bur oak mortality declined with increasing fire frequency. Attempts to preserve and maintain savannas as a viable ecosystem type in this region will require a long-term commitment to restoration-based management, with prescribed fire as a central tool. Burn frequency treatments with four or more fires per decade produce similar reductions in stem density and stand basal area but may lead to unsustainable oak tree populations. Within this general range, fire frequencies at a decadal scale should be chosen to address other management objectives, including suppressing shrubs and promoting increased cover of grasses and other herbaceous species. Fire management with a long-term view may also require periodic respites to allow for new cohorts of mature oak trees.
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    Shocks to the system: Community assembly of the oak savanna in a 40-year fire frequency experiment
    (Ecological Society of America, 2012) Cavender-Bares, Jeannine; Reich, Peter B
    Fire is a major force driving the evolution of plants and the structure and function of ecosystems globally. It thus likely operates as an important environmental filter that selects for species that have evolved to tolerate and depend on fire. Across a 40-year experimental fire gradient from frequently burned open savanna to unburned dense woodland in Minnesota, USA, we examined the relationships among community assembly, evolutionary history, and functional trait composition. Close relatives had similar abundance patterns across the fire gradient, providing evidence for phylogenetic conservatism in fire adaptation and highlighting the importance of shared ancestry in predicting species responses to fire. Phylogenetic beta diversity was greatest between the most extreme fire treatments across the gradient, indicating that species in the most contrasting fire regimes were most distantly related. Fire strongly influenced diversity, co-occurrence patterns, and leaf trait means and variances within communities. The most frequently burned communities had the highest species richness, exhibited the most resource-conservative leaf traits, and spanned the greatest number of phylogenetic lineages but harbored more close relatives within those lineages than other communities. In contrast, unburned communities had the lowest species diversity, the most acquisitive leaf traits, and the fewest phylogenetic lineages, but close relatives co-occurred less frequently. The largest difference in abundance between treatments occurred within the Rosales, Asteraceae, Vitaceae, and the Poaceae; woody Rosales were strongly selected for in unburned communities, while composites and grasses of the Poaceae were strongly selected for under frequent burning. A major climatic perturbation of consecutive hot, dry summers in the late 1980s prompted a significant shift in the functional and phylogenetic composition of communities. Greater than expected turnover in species composition occurred following the drought years, and then again during the subsequent five-year rebound period. Just after the drought year, turnover was greatest among recently diverged taxa, whereas during the rebound period turnover was greater among taxa that diverged deep in the phylogeny. The drought years also caused a short-term shift in functional traits, including declines in specific leaf area and leaf nitrogen content and an increase in leaf length. These results indicate that the phylogenetic and functional trait composition of communities are responsive both to fire gradients and to shocks to the system, such as climatic perturbation.