Which traits determine shifts in the abundance of tree species in a fire‐prone savanna?

Higgins, Steven I.; Bond, William J.; Combrink, Henri; Craine, Joseph M.; February, Edmund C.; Govender, Navashni; Lannas, Kathryn; Moncreiff, Glenn R.; Trollope, W.S.W.

doi:10.1111/j.1365-2745.2012.02026.x

Cited by 56 publications

(50 citation statements)

References 52 publications

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“…Because of the contrasting allocation patterns, lanky plants have been hypothesized to be associated with relatively less intense fires than corky plants (Vines 1968;Gignoux, Clobert & Menaut 1997). However, while previous studies have demonstrated the importance of each strategy to fire-escape Higgins et al 2012;Lawes, Midgley & Clarke 2013), none have directly linked their success to the prevailing type of consumer control in savannas.…”

Section: Introductionmentioning

confidence: 87%

“…Higgins et al 2012), and there is overwhelming evidence that bark thickness is the main protective bark trait in tropical ecosystems (Pinard & Huffman 1997;Hoffmann et al 2009;Lawes et al 2011a;Brando et al 2012). Although the main path by which African savanna plants escape fire seems to be related to the lanky strategy (Lawes, Midgley & Clarke 2013), the interspecific variability of bark traits may also be important in predicting species abundances at local and regional scales (Higgins et al 2012). Differences between ecozones could have a phylogenetic basis as the two zones share very few clades (Tables S4 and S6).…”

Section: Discussionmentioning

confidence: 99%

“…We have focused on bark thickness as a stem insulation mechanism, despite the fact that there are other stem traits that may also be relevant in reducing heat transfer, such as bark density and porosity (Lawes et al 2011b), bark moisture (Midgley, Lawes & Chamaill e-Jammes 2010;Lawes et al 2011b;Brando et al 2012;Higgins et al 2012) and stem-specific density (Brando et al 2012). In isolation, these The analyses correspond to plants with overlapping range sizes between afrotropical and neotropical savannas (see Fig.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, the rainfall regime strongly controls C 4 grass productivity (Fay et al 2003;Sankaran et al 2005) and is an important factor affecting the flammability of savannas (Higgins, Bond & Trollope 2000). This variability of factors and the wide distribution of the savanna biome results in savannas around the globe being subject to different disturbance regimes and hosting woody floras with distinct fire-escape strategies (Bond & van Wilgen 1996;Archibald & Bond 2003;Hoffmann et al 2009;Lawes et al 2011a;Higgins et al 2012). There are two main strategies by which woody plants escape from fire in savannas (Gignoux, Clobert & Menaut 1997).…”

Section: Introductionmentioning

confidence: 99%

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The lanky and the corky: fire‐escape strategies in savanna woody species

2013

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Summary1. Fire and herbivory are the main disturbances shaping the structure of savannas. In these ecosystems, the key strategies by which woody plants escape fire are either early height growth (the lanky strategy) or early bark growth (the corky strategy). We hypothesize that the dominance of each strategy in different savannas depends on the prevailing disturbance regimes. Given the importance of herbivory in afrotropical savanna, we expect woody plants in these savannas to be taller and have thinner barks (the lanky strategy) than plants in neotropical savanna where fire tends to be more intense (the corky strategy). 2. We compiled data on bark thickness and stem height in relation to stem diameter for afrotropical and neotropical savanna woody species and tested for differences in the allometric relationship between these two savannas with a general linear mixed model (GLMM). 3. Fire intensities were higher in neotropical than in afrotropical savannas. Afrotropical savanna plants were taller and had thinner barks for a given diameter than neotropical savanna plants -supporting our hypothesis that because of the contrasting disturbance regimes, the lanky strategy is more adaptive in afrotropical savannas, whereas the corky strategy is more adaptive in neotropical savannas. 4. Synthesis. While the lanky strategy is more associated with heavily browsed and fuel-controlled savannas, the corky strategy is associated with lightly browsed savannas that experience more intense fires. Because the relative role of disturbances varies across the globe, we suggest that the heightbark-diameter scheme is a powerful framework for understanding the ecology of many savannas.

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Section: Introductionmentioning

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The lanky and the corky: fire‐escape strategies in savanna woody species

2013

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“…), but the concept of the fire‐resistance threshold is easily applied to height‐determined fire tolerance in African trees (see Comparison to African savannas; Higgins et al. , ).…”

Section: Quantifying Nutrient Limitation Of Savanna–forest Biome Tranmentioning

confidence: 99%

Nutrient limitation in tropical savannas across multiple scales and mechanisms

Pellegrini

2016

Ecology

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Nutrients have been hypothesized to influence the distribution of the savanna biome through two possible mechanisms. Low nutrient availability may restrict growth rates of trees, thereby allowing for intermittent fires to maintain low tree cover; alternatively, nutrient deficiency may even place an absolute constraint on the ability of forests to form, independent of fire. However, we have little understanding of the scales at which nutrient limitation operates, what nutrients are limiting, and the mechanisms that influence how nutrient limitation regulates savanna–forest transitions. Here, I review literature, synthesize existing data, and present a simple calculation of nutrient demand to evaluate how nutrient limitation may regulate the distribution of the savanna biome. The literature primarily supports the hypothesis that nutrients may interact dynamically with fire to restrict the transition of savanna into forest. A compilation of indirect metrics of nutrient limitation suggest that nitrogen and phosphorus are both in short supply and may limit plants. Nutrient demand calculations provided a number of insights. First, trees required high rates of nitrogen and phosphorus supply relative to empirically determined inputs. Second, nutrient demand increased as landscapes approached the transition point between savanna and forest. Third, the potential for fire‐driven nutrient losses remained high throughout transitions, which may exaggerate limitation and could be a key feedback stabilizing the savanna biome. Fourth, nutrient limitation varied between functional groups, with fast‐growing forest species having substantially greater nutrient demand and a higher susceptibility to fire‐driven nutrient losses. Finally, African savanna trees required substantially larger amounts of nutrients supplied at greater rates, although this varied across plant functional groups. In summary, the ability of nutrients to control transitions emerges at individual and landscape scales, and is regulated through different mechanisms based on spatial (differences in underlying geology), temporal (stage in biome transition) and biological (species traits and community composition) variability.

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Sensitivity of global terrestrial carbon cycle dynamics to variability in satellite‐observed burned area

Poulter

Cadule

Cheiney

et al. 2015

Global Biogeochemical Cycles

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Fire plays an important role in terrestrial ecosystems by regulating biogeochemistry, biogeography, and energy budgets, yet despite the importance of fire as an integral ecosystem process, significant advances remain to improve its prognostic representation in carbon cycle models. To recommend and to help prioritize model improvements, this study investigates the sensitivity of a coupled global biogeography and biogeochemistry model, LPJ, to observed burned area measured by three independent satellite-derived products, GFED v3.1, L3JRC, and GlobCarbon. Model variables are compared with benchmarks that include pantropical aboveground biomass, global tree cover, and CO 2 and CO trace gas concentrations. Depending on prescribed burned area product, global aboveground carbon stocks varied by 300 Pg C, and woody cover ranged from 50 to 73 Mkm 2 . Tree cover and biomass were both reduced linearly with increasing burned area, i.e., at regional scales, a 10% reduction in tree cover per 1000 km 2 , and 0.04-to-0.40 Mg C reduction per 1000 km 2 . In boreal regions, satellite burned area improved simulated tree cover and biomass distributions, but in savanna regions, model-data correlations decreased. Global net biome production was relatively insensitive to burned area, and the long-term land carbon sink was robust,~2.5 Pg C yr À1, suggesting that feedbacks from ecosystem respiration compensated for reductions in fuel consumption via fire. CO 2 transport provided further evidence that heterotrophic respiration compensated any emission reductions in the absence of fire, with minor differences in modeled CO 2 fluxes among burned area products. CO was a more sensitive indicator for evaluating fire emissions, with MODIS-GFED burned area producing CO concentrations largely in agreement with independent observations in high latitudes. This study illustrates how ensembles of burned area data sets can be used to diagnose model structures and parameters for further improvement and also highlights the importance in considering uncertainties and variability in observed burned area data products for model applications.

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Which traits determine shifts in the abundance of tree species in a fire‐prone savanna?

Cited by 56 publications

References 52 publications

The lanky and the corky: fire‐escape strategies in savanna woody species

The lanky and the corky: fire‐escape strategies in savanna woody species

Nutrient limitation in tropical savannas across multiple scales and mechanisms

Sensitivity of global terrestrial carbon cycle dynamics to variability in satellite‐observed burned area

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