Sensitivity of woody carbon stocks to bark investment strategy in Neotropical savannas and forests

Abstract. Fire frequencies are changing in Neotropical savannas and forests as a result of forest fragmentation and increasing drought. Such changes in fire regime and climate are hypothesized to destabilize tropical carbon storage, but there has been little consideration of the widespread variability in tree fire tolerance strategies. To test how aboveground carbon stocks change with fire frequency and composition of plants with different fire tolerance strategies, we update the Ecosystem Demography model 2 (ED2) with (i) a fire survivorship module based on tree bark thickness (a key fire-tolerance trait across woody plants in savannas and forests), and (ii) plant functional types representative of trees in the region. With these updates, the model is better able to predict how fire frequency affects population demography and aboveground woody carbon. Simulations illustrate that the high survival rate of thick-barked, large trees reduces carbon losses with increasing fire frequency, with high investment in bark being particularly important in reducing losses in the wettest sites. Additionally, in landscapes that frequently burn, bark investment can broaden the range of climate and fire conditions under which savannas occur by reducing the range of conditions leading to either complete tree loss or complete grass loss. These results highlight that tropical vegetation dynamics depend not only on rainfall and changing fire frequencies but also on tree fire survival strategy. Further, our results indicate that fire survival strategy is fundamentally important in regulating tree size demography in ecosystems exposed to fire, which increases the preservation of aboveground carbon stocks and the coexistence of different plant functional groups.

[1]  W. Bond,et al.  Fire frequency filters species by bark traits in a savanna–forest mosaic , 2017 .

[2]  Douglas Sheil,et al.  Convergence of bark investment according to fire and climate structures ecosystem vulnerability to future change. , 2017, Ecology letters.

[3]  R. Pringle,et al.  Woody plant biomass and carbon exchange depend on elephant‐fire interactions across a productivity gradient in African savanna , 2017 .

[4]  David Medvigy,et al.  Diversity in plant hydraulic traits explains seasonal and inter-annual variations of vegetation dynamics in seasonally dry tropical forests. , 2016, The New phytologist.

[5]  Xingli Giam,et al.  Trade‐offs between savanna woody plant diversity and carbon storage in the Brazilian Cerrado , 2016, Global change biology.

[6]  D. Medvigy,et al.  Climate, soil organic layer, and nitrogen jointly drive forest development after fire in the North American boreal zone , 2016 .

[7]  Julieta A Rosell,et al.  Bark thickness across the angiosperms: more than just fire. , 2016, The New phytologist.

[8]  Victor Brovkin,et al.  Multiple stable states of tree cover in a global land surface model due to a fire‐vegetation feedback , 2016 .

[9]  A. Arneth,et al.  The effect of fire on tree–grass coexistence in savannas: a simulation study , 2016 .

[10]  W. Hoffmann,et al.  Shifts in functional traits elevate risk of fire‐driven tree dieback in tropical savanna and forest biomes , 2016, Global change biology.

[11]  Atul K. Jain,et al.  The dominant role of semi-arid ecosystems in the trend and variability of the land CO2 sink , 2015, Science.

[12]  Matthew F. McCabe,et al.  Recent reversal in loss of global terrestrial biomass , 2015 .

[13]  J. Pausas.  Bark thickness and fire regime , 2015 .

[14]  Benjamin Smith,et al.  A stand-alone tree demography and landscape structure module for Earth system models: integration with inventory data from temperate and boreal forests , 2014 .

[15]  Victor Brovkin,et al.  Forests, savannas, and grasslands: bridging the knowledge gap between ecology and Dynamic Global Vegetation Models , 2014 .

[16]  E. Davidson,et al.  Abrupt increases in Amazonian tree mortality due to drought–fire interactions , 2014, Proceedings of the National Academy of Sciences.

[17]  W. Hoffmann,et al.  Carbon accumulation and nitrogen pool recovery during transitions from savanna to forest in central Brazil. , 2014, Ecology.

[18]  F. Rovero,et al.  Large trees drive forest aboveground biomass variation in moist lowland forests across the tropics , 2013 .

[19]  J. Pausas,et al.  Fire drives functional thresholds on the savanna-forest transition. , 2013, Ecology.

[20]  Benjamin Smith,et al.  A stand‐alone tree demography and landscape structure module for Earth system models , 2013 .

[21]  Peter J. Clarke,et al.  Costs and benefits of relative bark thickness in relation to fire damage: a savanna/forest contrast , 2013 .

[22]  K. Mckinley,et al.  Fuels or microclimate? Understanding the drivers of fire feedbacks at savanna–forest boundaries , 2012 .

[23]  S. Gotsch,et al.  Ecological thresholds at the savanna-forest boundary: how plant traits, resources and fire govern the distribution of tropical biomes. , 2012, Ecology letters.

[24]  B. Bolker,et al.  Fire‐induced tree mortality in a neotropical forest: the roles of bark traits, tree size, wood density and fire behavior , 2012 .

[25]  David Medvigy,et al.  Predicting ecosystem dynamics at regional scales: an evaluation of a terrestrial biosphere model for the forests of northeastern North America , 2012, Philosophical Transactions of the Royal Society B: Biological Sciences.

[26]  S. Levin,et al.  The Global Extent and Determinants of Savanna and Forest as Alternative Biome States , 2011, Science.

[27]  R. B. Jackson,et al.  A Large and Persistent Carbon Sink in the World’s Forests , 2011, Science.

[28]  S. Levin,et al.  Tree cover in sub-Saharan Africa: rainfall and fire constrain forest and savanna as alternative stable states. , 2011, Ecology.

[29]  J. Randerson,et al.  Global fire emissions and the contribution of deforestation, savanna, forest, agricultural, and peat fires (1997-2009) , 2010 .

[30]  F. Woodward,et al.  Terrestrial Gross Carbon Dioxide Uptake: Global Distribution and Covariation with Climate , 2010, Science.

[31]  Sandy P. Harrison,et al.  The influence of vegetation, fire spread and fire behaviour on biomass burning and trace gas emissions: results from a process-based model , 2010 .

[32]  R. B. Jackson,et al.  CO 2 emissions from forest loss , 2009 .

[33]  S. Higgins,et al.  Impacts of climate change on the vegetation of Africa: an adaptive dynamic vegetation modelling approach , 2009 .

[34]  W. Hoffmann,et al.  Differences in growth patterns between co-occurring forest and savanna trees affect the forest-savanna boundary , 2009 .

[35]  S. Gotsch,et al.  Tree topkill, not mortality, governs the dynamics of savanna-forest boundaries under frequent fire in central Brazil. , 2009, Ecology.

[36]  S. Wofsy,et al.  Mechanistic scaling of ecosystem function and dynamics in space and time: Ecosystem Demography model version 2 , 2009 .

[37]  D. Roy,et al.  What limits fire? An examination of drivers of burnt area in Southern Africa , 2009 .

[38]  G. Dangelmayr,et al.  Do Fires in Savannas Consume Woody Biomass? A Comment on Approaches to Modeling Savanna Dynamics , 2008, The American Naturalist.

[39]  R. Betts,et al.  Climate Change, Deforestation, and the Fate of the Amazon , 2008, Science.

[40]  Simon Scheiter,et al.  Effects of four decades of fire manipulation on woody vegetation structure in Savanna. , 2007, Ecology.

[41]  Hisashi Sato,et al.  SEIB–DGVM: A new Dynamic Global Vegetation Model using a spatially explicit individual-based approach , 2007 .

[42]  Benjamin Smith,et al.  Implementing plant hydraulic architecture within the LPJ Dynamic Global Vegetation Model , 2006 .

[43]  E. Wood,et al.  Development of a 50-Year High-Resolution Global Dataset of Meteorological Forcings for Land Surface Modeling , 2006 .

[44]  Samuel Alleaume,et al.  Sensitivity of African biomes to changes in the precipitation regime , 2006 .

[45]  Wolfgang Lucht,et al.  Terrestrial biosphere carbon storage under alternative climate projections , 2006 .

[46]  F. Woodward,et al.  The global distribution of ecosystems in a world without fire. , 2004, The New phytologist.

[47]  K. Oleson,et al.  A dynamic global vegetation model for use with climate models: concepts and description of simulated vegetation dynamics , 2003 .

[48]  F. Woodward,et al.  Global response of terrestrial ecosystem structure and function to CO2 and climate change: results from six dynamic global vegetation models , 2001 .

[49]  S. Higgins,et al.  Fire, resprouting and variability: a recipe for grass–tree coexistence in savanna , 2000 .

[50]  J. Kauffman,et al.  Deforestation, Fire Susceptibility, and Potential Tree Responses to Fire in the Eastern Amazon , 1990 .

[51]  D. Burslem,et al.  Variation in tropical forest growth rates: combined effects of functional group composition and resource availability , 2003 .