Ecology, Evolution, and Dynamics of Savanna-Forest Transitions

savanna-forest ecotone


One of the greatest challenges in tropical plant ecology is the need to understand and predict how the extent of tropical forest will respond to changes in climate, fire regimes, and anthropogenic disturbance. Natural savanna-forest boundaries mark the natural limit to the distribution of tropical forest, and are therefore an ideal system for understanding the processes that control the distribution of these biomes. With our collaborators in Brazil, we are studying the effects of fire, resource availability and plant species traits on the dynamics and distribution of savanna and forest in the Cerrado of Brazil 

 




 




Vegetation-Fire Feedbacks

Positive feedbacks between vegetation and fire play a key role in the dynamics of savanna-forest boundaries. We are particularly interested in understanding how plant traits and climate mediate the intensity of this feedback.







Comparative studies of savanna and forest woody plants

We have been using comparative approaches to understand the origin and ecology of savanna trees and shrubs. We are particularly interested in understanding how natural selection has shaped their morphology, physiology, and ecology in ways that define the unique properties of savanna ecosystems.

Savanna tree species
















Miconia pohliana
, a savanna tree species                       
          Miconia cuspidata, a forest tree species


Check out our publications about savanna-forest transitions

2012

Hoffmann, W.A., Jaconis,S.Y, Geiger, E.L., Gotsch, S.G., Franco, A.C. (2012)  Fuels or microclimate? Understanding the drivers of fire feedbacks at savanna-forest boundaries. Austral Ecology, 37:634-643.

Hoffmann, W.A., Geiger, E.L., Gotsch, S., Rossatto, D.R., Silva, L.C.R., Lau, O.L., Haridasan, M., & Franco, A.C. (2012) Ecological thresholds at the savanna-forest boundary: How plant traits, resources and fire govern the distribution of tropical biomes. Ecology Letters, 15:759-768.

2011

Ratnam, J., Bond, W.J., Fensham, R.J., Hoffmann, W.A., Archibald, S., Lehmann, C.E.R.,  Andersen, M.T., Higgins,S.I., Sankaran, M. (2011) When is a "forest" a savanna, and why does it matter? Global Ecology and Biogeography, 20:653-660.

Lehmann, C.E.R.. Archibald, S.,Hoffmann, W.A. and Bond, W.J. (2011) Deciphering the distribution of the savanna biome. New Phytologist, 19: 197-209.

Geiger, E.L., Gotsch, S.G., do Vale, G.D., Haridasan, M., Franco, A.C., & Hoffmann, W.A. (2011) Distinct roles of savanna and forest tree species in regeneration following fire suppression in a Brazilian savanna. Journal of Vegetation Science, 22:312-321.

2010

Silva, L.C.R., Haridasan, M., Sternberg, L.S.L., Franco, A.C., & Hoffmann, W.A. Not all forests are expanding over central Brazilian savannas. Plant and Soil, 333: 431-442.

Gotsch, S.G., Geiger, E.L., Franco, A.C., Goldstein, G., Meinzer, F.C., Hoffmann, W.A. (2010) Allocation to leaf area and sapwood area affects water relations of co-occurring savanna and forest trees. Oecologia, 163:291-301.

2009

Zhang, Y.-J., Meinzer, F.C., Hao, G-Y., Scholz, F.G., Bucci, S.J., Giraldo, J.P., Cao, K-F., Franco, A.C., Hoffmann, W.A., and Goldstein, G. (2009) Size-dependent mortality in a Neotropical savanna tree: the role of height-related adjustments in hydraulic architecture and carbon allocation Plant Cell and Environment, 32:1456-1466.

Rossatto, D.R., Hoffmann, W.A., Franco, A.C. (2009) Differences in growth patterns between co-occurring forest and savanna species affect the forest-savanna boundary. Functional Ecology, 23: 689-698.

Rossatto, D.R., Hoffmann, W.A., Franco, A.C. (2009) Stomatal characteristics of congeneric savanna and forest species growing in a transitional region of central Brazil. Acta Botanica Brasilica 23:499-508.

Hoffmann, W.A., Franco, A.C. (2009) The importance of evolutionary history in studies of plant physiological ecology: examples from cerrados and forests of central Brazil. Special issue of Brazilian Journal of Plant Physiology, 20:247-256

Hoffmann, W.A., R. Adasme, M. Haridasan,  M. Carvalho, E. L. Geiger, M. A. B. Pereira, S. G. Gotsch, and A. C. Franco (2009). Tree topkill, not mortality, governs the dynamics of alternate stable states at savanna-forest boundaries under frequent fire in central Brazil.  Ecology 90:1326-1337.

2008

Silva, L.C.R, L. Sternberg, M. Haridasan, W. Hoffmann, F. Miralles-Wilhelm. A. C Franco (2008)  Expansion of gallery forests into central Brazilian savannas. Global Change Biology, 14, 2108-2118.

Hao, G.-Y. Hoffmann, W.A. Scholz, F.G. Bucci, S.J. Meinzer, F.C. Franco, A.C. Cao, K.-F. Goldstein, G. (2008)  Stem and leaf hydraulics of congeneric tree species from adjacent tropical savanna and forest ecosystems. Oecologia 155:405-415.

Hoffmann, W.A. and M. Haridasan (2008) The invasive grass, Melinis minutiflora, inhibits tree regeneration in a Neotropical Savanna. Austral Ecology 33:29-36.

2005

Hoffmann, W.A., Silva, E.R., Machado, G.C., Bucci, S.J., Scholz, F.G., Goldstein, G., Meinzer, F.C.  2005. Seasonal leaf dynamics across a tree density gradient in a Brazilian savanna.  Oecologia, 145: 307-316.

Hoffmann, W.A., Franco, A.C., Moreira, M.Z., Haridasan, M.  2005. Specific leaf area explains differences in leaf traits between congeneric savanna and forest trees. Functional Ecology  19: 932-940.

Hoffmann, W.A. 2005. Ecologia comparativa de especies lenhosas de cerrado e de mata (Comparative ecology of savanna and forest woody plants). Pp. 155- 166 in A. Scariot, J. M. Felfili, and J. C. Sousa-Silva (eds.) Cerrado: Ecologia, Biodiversidade e Conservacao, Ministerio do Meio Ambiente, Brasilia, Brazil.

2004

Hoffmann, W.A., Orthen, B. and Franco, A.C. 2004. Constraints to seedling success of savanna and forest trees across the savanna-forest boundary.  Oecologia 140:252-260.

Hoffmann, W.A., Lucatelli, V. M. P. C., Silva, F. J., Azeuedo, I. N. C., Marinho, M. da S., Albuquerque, A. M. S., Lopes, A. de O., Moreira, S. P. 2004. Impact of the invasive grass Melinis minutiflora at the savanna-forest ecotone in the Brazilian Cerrado. Diversity and Distributions, 10: 99-103.

2003

Hoffmann, W.A., B. Orthen, and P.K.V. Nascimento. 2003. Comparative fire ecology of tropical savanna and forest trees. Functional Ecology, 17: 720-726

Hoffmann, W.A., W. Schroeder and R.B. Jackson. 2003. Regional feedbacks among climate, fire, and tropical deforestation. Journal of Geophysical Research - Atmospheres, 108, DOI: 2003JD003494.

Hoffmann, W.A. and A.C. Franco. 2003. Comparative growth analysis of tropical savanna and forest trees using phylogenetically-independent contrasts. Journal of Ecology, 91: 475-484.

2002

Hoffmann, W. A., W. Schroeder, and R. B. Jackson. 2002. Positive feedbacks of fire, climate, and vegetation change and the conversion of tropical savannas. Geophysical Research Letters, 15: doi: 10.1029/2002GL015424

2000

Hoffmann, W. A. 2000.  Post-establishment seedling success of savanna and forest species in the Brazilian Cerrado. Biotropica, 32(1):62-69

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