The reproductive response of an endemic bunchgrass indicates historical timing of a keystone process

Fill, Jennifer M.; Welch, Shane M.; Waldron, Jayme L.; Mousseau, Timothy A.

doi:10.1890/es12-00044.1

Cited by 47 publications

(48 citation statements)

References 43 publications

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“…Flowering by grasses also was suppressed by more intense fires. We note that flowering by little bluestem, like other savanna and prairie grasses in the southeastern United States, is strongly and positively associated with fires during the growing season (e.g., Streng et al 1993, Main and Barry 2002, Fill et al 2012, Shepherd et al 2012. In our study, average numbers of flowering culms (adjusted for pre-fire genet size) when no pine needles were present were about twice the number when pine needles were present.…”

Section: Effects Of Pyrogenic Fuels On Ground-layer Plants In Pine Samentioning

confidence: 43%

Pyrogenic fuels produced by savanna trees can engineer humid savannas

Platt

Ellair

Huffman

et al. 2016

Ecological Monographs

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Natural fires ignited by lightning strikes following droughts frequently are posited as the ecological mechanism maintaining discontinuous tree cover and grass‐dominated ground layers in savannas. Such fires, however, may not reliably maintain humid savannas. We propose that savanna trees producing pyrogenic shed leaves might engineer fire characteristics, affecting ground‐layer plants in ways that maintain humid savannas. We explored our hypothesis in a high‐rainfall, frequently burned pine savanna in which the dominant tree, longleaf pine (Pinus palustris), produces resinous needles that become highly flammable when shed and dried. We postulated that pyrogenic needles should have much greater influence on fire characteristics at ground level, and hence post‐fire responses of dominant shrubs and grasses, than other abundant fine fuels (shed oak leaves and grass culms). We further reasoned that these effects should increase with amounts of needles. We managed site conditions that affect fuels (time since fire, dominant vegetation), manipulated amounts of needles in ground‐layer plots, prescribed burned the plots, and measured fire characteristics at ground level. We also measured characteristics of ground‐layer oaks and grasses before, then 2 and 8 months after fires. We tested our hypotheses regarding effects of pyrogenic pine fuels on fire characteristics and vegetation regrowth and explored direct and indirect effects of fuels on fire characteristics and vegetation using a structural equation model. Pine needles influenced fire characteristics, elevating maximum temperature increases, durations of heating above 60°C, and fine fuel consumption considerably above measurements when fuels only included other savanna plants. Presence of pine needles depressed post‐fire numbers of oak stems and grass culms, especially in the interior of grass genets, as well as post‐fire flowering of grasses. The structural equation model indicated strong direct and indirect pathways from pine needles to post‐fire responses of oaks and grasses. The experimental field tests of hypotheses, bolstered by structural equation modeling, indicate pyrogenic fine fuels modify characteristics of prescribed fires at ground level, negatively affecting dominant ground‐layer oaks and grasses. Frequent fires fueled by pyrogenic needles should maintain humid savannas and generate spatial pyrodiversity that affects composition and dynamics of pine savanna ground‐layer vegetation.

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Section: Effects Of Pyrogenic Fuels On Ground-layer Plants In Pine Samentioning

confidence: 43%

Pyrogenic fuels produced by savanna trees can engineer humid savannas

Platt

Ellair

Huffman

et al. 2016

Ecological Monographs

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“…Prescribed fires were conducted in both sites in June 2017, within days of each other, when fire is known to stimulate wiregrass flowering (Clewell , Fill et al. ).…”

Section: Methodsmentioning

confidence: 99%

Pyrogenic flowering of Aristida beyrichiana following 50 years of fire exclusion

2019

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Fire-stimulated or pyrogenic flowering is one of many traits that enable plants in fire-prone ecosystems to persist or dominate following frequent fires. Obligate pyrogenic flowering has long been observed in wiregrass (Aristida beyrichiana), a foundation bunchgrass in frequently burned longleaf pine ecosystems in the southeastern United States. Widespread fire exclusion in this ecosystem has contributed to well-documented declines in plant and animal biodiversity prompting the need for restoration efforts. We studied the effect of fire reintroduction on the flowering of wiregrass in northern Florida, USA. Prescribed fires were ignited in a 50-yr unburned site and an adjacent frequently burned site in the summer of 2017. Wiregrass was measured eight months after the burns in both stands. As expected, the frequently burned stand had higher density, basal area, and percent flowering of wiregrass tussocks. Logistic regression revealed that wiregrass initiated flowering at significantly larger sizes in the long-unburned stand. Despite these differences, wiregrass size distributions were similar in both stands, with the long-unburned stand lacking tussocks in the largest (100+ cm 2 ) size class. We did not find differences in the number of flower culms per unit of mass between the two stands. Even though diminished in nearly every measure, the ability of wiregrass to flower after five decades of fire exclusion, and presumably no sexual reproduction, provides evidence of resilience of the dominant herb of these ecosystems.

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“…Wiregrass (Aristida stricta) the most common grass species of APAFR is well known to be finely tuned to flower and set seed only in response to transition time-of-year fires (Fill et al 2012). Rare species of plants and animals have likely been most affected by the changes in fire regimes over the past century.…”

Section: Plants and Animalsmentioning

confidence: 99%

“…Final Report Draft 9/18/2014 Fire History of Avon Park Air Force Rangepine savanna species show strong and varying responses to fire at different times of year (Streng et al 1993, Brewer and Platt 1994, Fill et al 2012). …”

Section: Introductionmentioning

confidence: 99%