0 avis
Pathways of savannization in a mesic African savanna-forest mosaic
Archive ouverte
Edité par CCSD -
Abstract Typically, savannas experience frequent fires, which limit tree cover and promote flammable grass accumulation, whereas forests and thickets form dense canopies that exclude fires by reducing C4-grass fuel loads and creating a humid microclimate. However, extreme fires occasionally burn into these closed canopy systems. Although these are known to cause tree mortality and can make repeat fires more likely, the long-term consequences of an extreme fire event for closed canopy vegetation structure and potential savannization remain largely unknown. Here, we analysed whether an extreme fire event could, alone, alter species composition, vegetation structure, and fire regimes of closed canopy ecosystems in a natural savanna-forest-thicket mosaic, or whether successive fires after an initial extreme fire event were necessary to trigger a biome transition between these alternative stable states. We found that forests that only burned once recovered, whereas those that burned again following an initial extreme fire event underwent a transition from closed-canopy forests to open, grassy systems. Thickets had lower levels of tree mortality following fires than forests, although repeat fires also led to a transition towards open grassy systems, structurally resembling savannas. Our results suggest that while extreme fires set the stage for a biome transition, subsequent fires are necessary for grass composition to resemble neighbouring savanna grass communities, ultimately resulting in a savanna fire regime. Savannization, following extreme fire events, is possible in natural mosaic ecosystems where open and closed canopy vegetation types represent alternative stable states.
Consulter en ligne
Suggestions
Du même auteur
