I know that Peter Linder has evidence for grasslands being the dominant vegetation type in southern Afromontane areas and forests restricted to areas protected from fire (Meadows and Linder 1993).
In contrast White argues that in eg Malawi, forest should dominate and that grassland simply reflects a stage in the succession back to forest (eg, in Chapman and White 1970).
Does anyone know the current thinking on this for sub saharan Africa north of South Africa?
This is a pertinent question for not just Afromontane landscapes but most forest-grassland mosaics within South Africa. For SA its a question of time-frame and anthropogenic influences. How far do we need to go back in time to consider what is natural? Certainly at lower altitudes where burning regimes are suppressed, succession kicks in and it 'reverts' back to forest. This might be the same within Afromontane landscapes. A biome is limited by its 'niche' distribution, if the seed bank is available and conditions are favourable then there certainly is potential for forests to expand. In the Drakensberg system there is research looking at this dynamic: Craig Morris - could you add? I always think if a habitat needs to be heavily managed to be maintained, then is it naturally destined to remain static? But, I suppose the fact is that nothing is in a natural state, the natural migration of herbivores are suppressed and replaced by domestic stock meaning that we need to manage to a certain degree.
I agree with Yvette that asking what's 'natural' is perhaps not the most useful thing to ask as what was natural in the distant past (the ecological disturbances/drivers, mix of species, state of evolution of flora) is no longer present and is destined to change (quite markedly) in the future as the heavy hand of H. sapiens descends upon this earth. Depending on the environment, one might perhaps ask what is possible now is terms of fundamental and realised niches of forest and grasses, and how might this change in the future, e.g. CO2 might allow trees to expand into grassy areas but increasing human- and temperature-driven fires might hold forests in check. We have come to believe in our tools (esp. fire) for commanding and controlling mesic landscapes, but are perhaps deluded by the false (and elusive) elixir of stability and natural order of things which we presumed to have prevailed in the past, and thus be necessary to maintain. Looking back could be useful but the future looks even more intriguing.@ Yvette C Ehlers Smith
This recent study from our neck of the Afromontane woods could be relevant to your question of what is naturally possible:
Small fire refugia in the grassy matrix and the persistence of Afrotemperate forest in the Drakensberg mountains
https://www.nature.com/articles/s41598-017-06747-2
Hi Yvette and Craig, thanks both for your comments, much appreciated.
I agree with your thoughts re what is natural etc. I am familiar with the Adie et al paper and i like it. I am not so sure it applies in Nigeria (where I work) hence my question. Certainly seems that fire has likely played a role in grassland/forest dynamics since the Miocene and through Pleistocene but now more frequent fires are causing more extreme scenarios. Also grazing (at least in Nigeria) is changing the grassland composition. I would like to know to what extent montane grasslands in Nigeria were more forest dominated before the arrival of the Fulani ~ 16th/17th cent. Why I asked the questionis that we are writing a paper on edge effects, using data from our CTFS Forest Plot- want to link it in with the Adie paper.
I think Smarties can explain it all :-)
http://www.saeon.ac.za/enewsletter/archives/2018/october2018/doc01
These might be of interest:
Article The Significance of Fire for Afroalpine Ericaceous Vegetation
https://www.researchgate.net/project/FOR-2358-The-Mountain-Exile-Hypothesis-How-humans-benefited-and-re-shaped-African-high-altitude-ecosystems-during-Quaternary-climate-changes-Project-P1-Archaeology-and-Archeozoology-2
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