Climate seasonality, fire and global patterns of tree cover

Bucini, Gabriela; Beckage, Brian; Gross, Louis J.

doi:10.21425/f59233610

Cited by 8 publications

(10 citation statements)

References 46 publications

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“…The histograms in (c) show multimodal patterns of both observed and simulated tree cover, which indicate alternative stable states. The low density of tree cover values just below 10% in the simulated results is explained by the absence of effect of fire below this value (see Figure 1c) et al, 2011; e.g., Bucini et al, 2017; but see Wuyts, Champneys, & House, 2017), which hampers the inference of temporal dynamics.…”

Section: Discussionmentioning

confidence: 78%

“…We found an important effect of rainfall variability on fire‐driven alternative stable states. It is known that in wet areas on the one hand, occasional dry periods enhance fire‐prone conditions; in dry areas on the other hand, occasional wet periods stimulate fuel build‐up for fires in dry periods (Archibald, Nickless, Govender, Scholes, & Lehsten, ; Archibald, Roy, van Wilgen, & Scholes, ; Bucini, Beckage, & Gross, ; Van der Werf, Randerson, Giglio, Gobron, & Dolman, ). However, we found that seasonal and interannual rainfall variability affect fire regimes in different ways with contrasting implications for forest‐savanna stability.…”

Section: Discussionmentioning

confidence: 99%

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Resilience of tropical tree cover: The roles of climate, fire, and herbivory

Staal

Nes

Hantson

et al. 2018

Global Change Biology

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Fires and herbivores shape tropical vegetation structure, but their effects on the stability of tree cover in different climates remain elusive. Here, we integrate empirical and theoretical approaches to determine the effects of climate on fire- and herbivore-driven forest-savanna shifts. We analyzed time series of remotely sensed tree cover and fire observations with estimates of herbivore pressure across the tropics to quantify the fire-tree cover and herbivore-tree cover feedbacks along climatic gradients. From these empirical results, we developed a spatially explicit, stochastic fire-vegetation model that accounts for herbivore pressure. We find emergent alternative stable states in tree cover with hysteresis across rainfall conditions. Whereas the herbivore-tree cover feedback can maintain low tree cover below 1,100 mm mean annual rainfall, the fire-tree cover feedback can maintain low tree cover at higher rainfall levels. Interestingly, the rainfall range where fire-driven alternative vegetation states can be found depends strongly on rainfall variability. Both higher seasonal and interannual variability in rainfall increase fire frequency, but only seasonality expands the distribution of fire-maintained savannas into wetter climates. The strength of the fire-tree cover feedback depends on the spatial configuration of tree cover: Landscapes with clustered low tree-cover areas are more susceptible to cross a tipping point of fire-driven forest loss than landscapes with scattered deforested patches. Our study shows how feedbacks involving fire, herbivores, and the spatial structure of tree cover explain the resilience of tree cover across climates.

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Section: Discussionmentioning

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Resilience of tropical tree cover: The roles of climate, fire, and herbivory

Staal

Nes

Hantson

et al. 2018

Global Change Biology

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“…Therefore, achieving a better understanding of the effects of PV on tree cover is highly relevant in the context of on‐going climate change. Existing analyses of the effects of PV have mostly focused on PV at seasonal time‐scales using simplistic climatic indices derived from monthly rainfall data (Bucini, Beckage, & Gross, ; Holmgren, Hirota, van Nes, & Scheffer, ; Lehmann et al, ; Staal, Dekker, Xu, & van Nes, ; Staver et al, ; Zemp et al, ; Zeng, Chen, Piao, Rabin, & Shen, ) while relatively few studies have investigated the importance of PV at daily (Good & Caylor, ; Kulmatiski & Beard, ) or inter‐annual (Holmgren et al, ) time‐scales. Moreover, the collinearity and interaction between PV components, MAP and other environmental drivers were not well characterized in previous analyses, which can bias the reported effects and contribution of PV to spatial variations in tree cover.…”

Section: Introductionmentioning

confidence: 99%

Tree cover shows strong sensitivity to precipitation variability across the global tropics

Medvigy

Trugman

et al. 2018

Global Ecol Biogeogr

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Aim Vegetation is sensitive to mean annual precipitation (MAP), but the sensitivity of vegetation to precipitation variability (PV) is less clear. Tropical ecosystems are likely to experience increased PV in the future. Here we assessed the importance, magnitude and mechanism of PV effects on tree cover in the context of covarying environmental drivers such as fire, temperature and soil properties. Location Tropical land. Time period 2000–2010. Major taxa studied Trees. Methods We compiled climate, soil and remotely‐sensed tree cover data over tropical land. We then comprehensively assessed the contribution of PV at different time‐scales to tropical tree cover variations and estimated the sensitivity of tree cover to PV changes by conducting rolling‐window regression and variance decomposition analyses. We further adopted a mechanistic modelling approach to test whether water competition between trees and grasses can explain the observed effect of PV. Results We find that PV contributes 33–56% to the total explained spatial variation (65–79%) in tree cover. The contribution of PV depends on MAP and is highest under intermediate MAP (500–1,500 mm). Tree cover generally increases with rainy day frequency and wet season length but shows mixed responses to inter‐annual PV. Based on the estimated sensitivity, tropical tree cover can decrease by 3–5% overall and by up to 20% in Amazonia under a 20% decrease in rainy days. Mechanistic modelling analysis reproduced the continental differences in tree cover along an MAP gradient. Main conclusions Under intermediate rainfall regimes (500–1,500 mm), PV can be a more important determinant of tropical tree cover than conventionally proposed drivers such as MAP and fire. The effect of PV likely results from the sensitivity of tree–grass competition to the temporal distribution of water resources. These results show that climate variability can strongly shape the biosphere.

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“…We found that the effect of rainfall variability on fire occurrence, however, varies along the rainfall gradient. It is known that in wet areas on the one hand, occasional dry periods enhance fire-prone conditions; in dry areas on the other hand, occasional wet periods stimulate fuel build-up for fires in dry periods (Van der Werf et al, 2008;Archibald et al, 2009;Archibald et al, 2010;Bucini et al, 2017). However, seasonal and inter-annual rainfall variability affect fire regimes in different ways with contrasting implications for forest-savanna stability.…”

Section: Discussionmentioning

confidence: 99%

“…The model occupies a promising niche that could stimulate new insights in tropical fire-vegetation dynamics because it bridges a gap between observations and theory. On the observational side the work on tropical tree cover that indicates alternative stable states has so far been mostly based on static patterns instead of dynamic ones (Hirota et al, 2011;Staver et al, 2011b;Holmgren et al, 2013;Bucini et al, 2017; but see Wuyts et al, 2017), which hampers the inference of temporal dynamics.…”

Section: Discussionmentioning

confidence: 99%

Resilience of tropical forest and savanna: bridging theory and observation

Staal¹

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Climate seasonality, fire and global patterns of tree cover

Cited by 8 publications

References 46 publications

Resilience of tropical tree cover: The roles of climate, fire, and herbivory

Resilience of tropical tree cover: The roles of climate, fire, and herbivory

Tree cover shows strong sensitivity to precipitation variability across the global tropics

Resilience of tropical forest and savanna: bridging theory and observation

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