Patterns of Plant Species Richness in a Wet Slash-Pine (Pinus elliottii) Savanna

Brewer, J. Stephen

doi:10.2307/2997219

Cited by 32 publications

(43 citation statements)

References 19 publications

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“…Slash pine stems greater than 1.5 m tall serve as effective perches for animal‐dispersed seeds of trees, shrubs, and vines (Hinman, Brewer, & Ashley, ). As a result, dense woody thickets form at the base of pines, which have substantially lower plant species richness due to losses of herbaceous species (Brewer, ). Greater seedling establishment of woody species beneath pines is not related to more favorable environmental differences near pines, but rather is limited by seed dispersal (Brewer, ; Hinman et al., ).…”

Section: Methodsmentioning

confidence: 99%

Stochastic losses of fire‐dependent endemic herbs revealed by a 65‐year chronosequence of dispersal‐limited woody plant encroachment

Brewer

2017

Ecology and Evolution

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The factors responsible for maintaining diverse groundcover plant communities of high conservation value in frequently burned wet pine savannas are poorly understood. While most management involves manipulating extrinsic factors important in maintaining species diversity (e.g., fire regimes), most ecological theory (e.g., niche theory and neutral theory) examines how traits exhibited by the species promote species coexistence. Furthermore, although many ecologists focus on processes that maintain local species diversity, conservation biologists have argued that other indices (e.g., phylogenetic diversity) are better for evaluating assemblages in terms of their conservation value. I used a null model that employed beta‐diversity calculations based on Raup–Crick distances to test for deterministic herbaceous species losses associated with a 65‐year chronosequence of woody species encroachment within each of three localities. I quantified conservation value of assemblages by measuring taxonomic distinctness, endemism, and floristic quality of plots with and without woody encroachment. Reductions in herb species richness per plot attributable to woody encroachment were largely stochastic, as indicated by a lack of change in the mean or variance in beta‐diversity caused by woody encroachment in the savannas studied here. Taxonomic distinctness, endemism, and floristic quality (when summed across all species) were all greater in areas that had not experienced woody encroachment. However, when corrected for local species richness, only average endemism and floristic quality of assemblages inclusive of herbs and woody plants were greater in areas that had not experienced woody encroachment, due to the more restricted ranges and habitat requirements of herbs. Results suggest that frequent fires maintain diverse assemblages of fire‐dependent herb species endemic to the region. The stochastic loss of plant species, irrespective of their taxonomic distinctness, to woody encroachment suggests that the relevance of niche partitioning or phylogenetic diversity to the management of biodiversity in wet pine savannas is minimal.

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Section: Methodsmentioning

confidence: 99%

Stochastic losses of fire‐dependent endemic herbs revealed by a 65‐year chronosequence of dispersal‐limited woody plant encroachment

Brewer

2017

Ecology and Evolution

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“…Huston (1994) proposed that high fire frequencies promote high species richness in savannas by preventing competitive exclusion of grasses and forbs by woody plants. Furthermore, understory plant community composition and diversity in savannas often varies across gradients in understory light and soil resources associated with spatial variability in overstory tree cover (Bray 1958;Belsky et al 1989;Vetaas 1992;Scholes and Archer 1997;McPherson 1997;Brewer 1998). Thus, high plant community heterogeneity and overall species richness may be observed in savannas with intermediate and spatially variable tree canopy cover (Leach and Givnish 1999) due to high plant resource heterogeneity.…”

Section: Introductionmentioning

confidence: 95%

Fire frequency and tree canopy structure influence plant species diversity in a forest-grassland ecotone

2007

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Disturbances and environmental heterogeneity are two factors thought to influence plant species diversity, but their effects are still poorly understood in many ecosystems. We surveyed understory vegetation and measured tree canopy cover on permanent plots spanning an experimental fire frequency gradient to test fire frequency and tree canopy effects on plant species richness and community heterogeneity within a mosaic of grassland, oak savanna, oak woodland, and forest communities. Species richness was assessed for all vascular plant species and for three plant functional groups: grasses, forbs, and woody plants. Understory species richness and community heterogeneity were maximized at biennial fire frequencies, consistent with predictions of the intermediate disturbance hypothesis. However, overstory tree species richness was highest in unburned units and declined with increasing fire frequency. Maximum species richness was observed in unburned units for woody species, with biennial fires for forbs, and with near-annual fires for grasses. Savannas and woodlands with intermediate and spatially variable tree canopy cover had greater species richness and community heterogeneity than old-field grasslands or closed-canopy forests. Functional group species richness was positively correlated with functional group cover. Our results suggest that annual to biennial fire frequencies prevent shrubs and trees from competitively excluding grasses and prairie forbs, while spatially variable shading from overstory trees reduces grass dominance and provides a wider range of habitat conditions. Hence, high species richness in savannas is due to both high sample point species richness and high community heterogeneity among sample points, which are maintained by intermediate fire frequencies and variable tree canopy cover.

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“…P. elliottii is a fast-growing tree species originally from Florida, USA that was introduced to Brazil in 1936 (Kronka et al, 2005). It is native from pine Flatwoods, a kind of wet savanna where arboreal stratum is composed mostly by pine trees that are capable of change light availability to the assemblages of the lowers strata (Brewer, 1998). When the pine plantations started, some stands of native vegetation were maintained, where the plant community has changed considerably in its structure over the last decades, suffering an increase in biomass after suppression of fire and cattle grazing.…”

Section: Study Areamentioning

confidence: 99%

Can native vegetation recover after slash pine cultivation in the Brazilian Savanna?

Abreu

Assis

Frison

et al. 2011

Forest Ecology and Management

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Patterns of Plant Species Richness in a Wet Slash-Pine (Pinus elliottii) Savanna

Cited by 32 publications

References 19 publications

Stochastic losses of fire‐dependent endemic herbs revealed by a 65‐year chronosequence of dispersal‐limited woody plant encroachment

Stochastic losses of fire‐dependent endemic herbs revealed by a 65‐year chronosequence of dispersal‐limited woody plant encroachment

Fire frequency and tree canopy structure influence plant species diversity in a forest-grassland ecotone

Can native vegetation recover after slash pine cultivation in the Brazilian Savanna?

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