New PNAS paper: Floristic evidence for alternative biome states in tropical Africa

This is just out in PNAS, and shows that African savannas have a very distinct tree flora compared to nearby forests, based on a huge dataset of floristic inventories. This provides a new line of evidence that savannas and forests are alternative states in many climatic and edaphic conditions.

Why does that matter? Well, if you can have either forest or savanna in a particular location, then for one thing, you might want to think carefully about what your target for restoring the ecosystem might be. Secondly, the general idea of alternative stable states is an important, but disputed concept in savanna ecology. Most of the evidence for alt. states comes from models, or the bi-modal distribution of e.g. tree cover in some parts of climate space. Neither of these are proof that alt stable states exists, in the latter case because lots of process can give rise to bimodal distributions even in the absence of stabilising feedbacks at each state. This paper presents a new line of evidence to support the hypothesis of alt. stable states, using the floristic composition. It shows two distinct floristic states that co-occurr under the same climate and soil conditions.

The paper involved many of the people who are part of the SEOSAW partnership. it was led by Dr Julie Aleman, and you can see an interesting write up of the implications of the paper for restoration projects here: “The state of mature ecosystems must be taken into account before launching massive reforestation plans in sub-Saharan Africa, according to geo-ecologist Julie Aleman, a visiting researcher in the geography department of Université de Montréal.”

Full paper is here.