Abrupt shifts in African savanna tree cover along a climatic gradient

作者：Favier Charly^*; Aleman Julie; Bremond Laurent; Dubois Marc A; Freycon Vincent; Yangakola Jean Michel

来源：Global Ecology and Biogeography, 2012, 21(8): 787-797.

DOI：10.1111/j.1466-8238.2011.00725.x

• Alternative stable states
• Central Tropical Africa
• patch dynamics systems
• phytogeographical classification
• remote sensing data
• savanna
• spatial scales
• tree cover

Aim To describe patterns of tree cover in savannas over a climatic gradient and a range of spatial scales and test if there are identifiable climate-related mean structures, if tree cover always increases with water availability and if there is a continuous trend or a stepwise trend in tree cover. Location Central Tropical Africa. Methods We compared a new analysis of satellite tree cover data with botanical, phytogeographical and environmental data. Results Along the climatic transect, six vegetation structures were distinguished according to their average tree cover, which can co-occur as mosaics. The resulting abrupt shifts in tree cover were not correlated to any shifts in either environmental variables or in tree species distributions. Main conclusions A strong contrast appears between fine-scale variability in tree cover and coarse-scale structural states that are stable over several degrees of latitude. While climate parameters and species pools display a continuous evolution along the climatic gradient, these stable structural states have discontinuous transitions, resulting in regions containing mosaics of alternative stable states. Soils appear to have little effect inside the climatic stable state domains but a strong action on the location of the transitions. This indicates that savannas are patch dynamics systems, prone to feedbacks stabilizing their coarse-scale structure over wide ranges of environmental conditions.

• 出版日期2012-8
• 单位中国地震局