Size Dependency of Post-Disturbance Recovery of Multi-Stemmed Resprouting Trees

Schafer, Jennifer L.; Just, Michael G.

doi:10.1371/journal.pone.0105600

Cited by 20 publications

(25 citation statements)

References 54 publications

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“…Fires top-kill genets, blocking growth into the overstory (e.g., Hoffmann et al 2009, Ellair and Platt 2013, Werner and Prior 2013. Top-killed plants survive via resprouting meristems located below heat-killed portions of the plants, typically at/below ground level on underground storage organs (Bellingham and Sparrow 2000, Drewa et al 2002, Hoffman and Moreira 2002, Maurin et al 2014, Schafer and Just 2014. Our study indicates that recurrent fires fueled by pyrogenic pine fuels not only maintain the fire trap, but depress genets by effects on bud banks on underground structures.…”

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

confidence: 72%

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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: 72%

“…, Maurin et al. , Schafer and Just ). Our study indicates that recurrent fires fueled by pyrogenic pine fuels not only maintain the fire trap, but depress genets by effects on bud banks on underground structures.…”

Section: Discussionmentioning

confidence: 99%

Pyrogenic fuels produced by savanna trees can engineer humid savannas

Platt

Ellair

Huffman

et al. 2016

Ecological Monographs

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“…Allocation patterns to above-and below-ground biomass may be the critical determinant of whether a species is likely to conform to the persistence model (Tomlinson et al 2012(Tomlinson et al , 2013, as in long-leaf pine savanna (Grady & Hoffmann 2012;Schafer & Just 2014), Brazilian cerrado (Hoffmann & Solbrig 2003) and here, with the example of the non-eucalypts T. ferdinandiana and P. careya under LDS. Escape heights for these populations lie somewhere between the upper limit of the prediction interval around the stable persistence equilibrium and maximum potential height of the species (Table 1).…”

Section: Case Study Results and Discussionmentioning

confidence: 98%

Defining the fire trap: Extension of the persistence equilibrium model in mesic savannas

et al. 2017

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Mesic savannas are dominated by trees that are strong resprouters caught in a frequent fire trap. Persistence within this fire trap has been described by a resprout curve of SizeNext~f(Pre-fire size), defined by the Michaelis-Menten function. A key feature of this resprout curve is a stable persistence equilibrium that represents the size of individual plants upon which a population will converge over successive inter-fire time steps under a given fire regime. Here, we contend that such a resprout curve does not adequately describe resprout tree dynamics in frequently burnt mesic savannas because it is constrained to an asymptote. We propose a new framework for modelling the resprout curve, which recognizes that local environmental stochasticity and growth patterns can interact to change the growth response function entirely, and thus more readily reflect the range of feasible resprout responses. Importantly, we define an unstable equilibrium representing the size above which individuals have escaped the fire trap and explore mechanisms that can shift an individual from persistence to escape. Through a case study from northern Australia, we confirm that our framework provides a simple yet practical approach to defining these critical aspects of savanna tree growth dynamics: persistence and escape.

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“…Survival of these trees was generally consistent with those from an earlier study where 58 permanently marked sub-adult eucalypts were followed for six years . Where a resprouting sub-adult tree initially produced multiple stems after the complete loss of above ground biomass, the maximum height of those stems was sufficient to accurately assess recovery and persistence of the individual (Werner and Franklin 2010, P. A. Werner, unpublished data), as was the case in a study of six woody species in a pine savanna in North Carolina (Schafer and Just 2014).…”

Section: Parameterization Of Transition Matricesmentioning

confidence: 99%

Savanna canopy trees under fire: long‐term persistence and transient dynamics from a stage‐based matrix population model

Werner

Peacock

2019

Ecosphere

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Fire is a major disturbance driving the dynamics of the world's savannas. Almost all fires are set by humans who are increasingly altering fire timing and frequency on every continent. The world's largest protected areas of savannas are found in monsoonal northern Australia. These include relatively intact, tall, open forests where traditional indigenous fire regimes have been largely replaced in the past half century by contemporary patterns with trees experiencing fire as often as three out of five years. Eucalypt canopy trees form the basic structure of these savannas and changes to the canopy due to fire regimes cascade to affect other plants and animals. In this study, we used data from nearly three decades of field studies on the effects of fire on individual trees to define eight life‐history stages and to calculate transition rates among stages. We developed a stage‐based matrix population model that explicitly considers how fire season and understory influence growth, survival, and recruitment for each life‐history stage. Long‐term population growth rates and transient population dynamics were calculated under five different fire regimes, each in two understory types, using both deterministic and stochastic simulations of seasonal timing of fires. We found that fire was necessary for long‐term persistence of eucalypt canopy tree populations but, under annual fires, most populations did not survive. Population persistence was highly dependent on fire regime (fire season and frequency) and understory type. A stochastic model tended to yield higher population growth rates than the deterministic model with regular, periodic fires, even under the same long‐term frequency of fires. Transient population dynamics over 100 yr also depended on fire regime and understory, with implications for savanna physiognomy and management. Model predictions were tested in an independent data set from a 21‐yr longitudinal field study in Kakadu National Park. This study is a novel and integrative contribution to our understanding of fire in savanna biomes regarding the potential for long‐term persistence and transient dynamics of savanna canopy tree populations. The model is relatively simple, generalizable, and adaptable for further investigations of the population dynamics of savanna trees under fire.

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Size Dependency of Post-Disturbance Recovery of Multi-Stemmed Resprouting Trees

Cited by 20 publications

References 54 publications

Pyrogenic fuels produced by savanna trees can engineer humid savannas

Pyrogenic fuels produced by savanna trees can engineer humid savannas

Defining the fire trap: Extension of the persistence equilibrium model in mesic savannas

Savanna canopy trees under fire: long‐term persistence and transient dynamics from a stage‐based matrix population model

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