PW Richards (http://ind.pn/OzMlyf ), the father of tropical ecology, proposed that Africa is the odd man out.
Tree diversity in equatorial Africa is much lower than in the Amazon. 50-75/ha vs >200 Equatorial SA. Parmentier et al (2007) and others discuss that area, drought, fire, contraction through history are primary reasons for low species diversity
He will present biotic arguments rather than abiotic arguments for the low diversity.
Small islands such as the Solomons have twice the tree species diversity of Central Africa
The total flora of Gabon is quite rich (> 6000 species). In a tropical forest flora about a third of the flora are trees (around 2000 tree species). A hectare contains about 1/10 of regional (Gamma) diversity, so we would expect about twice as many species per hectare than we see.\
He plots species accumulation curves for various tropical forests. Cameroon is no different to other tropical forests with similar climates. The problem is the per hectare diversity is much lower. Why?
He compares Gabon with the Peruvian Amazon. Lots more trees per hectare in Peru (mean 618) than Gabon (around 420). When you look at forest structure,
Much much lower diversity in small and large saplings, somewhat lower than small trees. Most diversity in African trees is in the large trees (at similar levels of diversity to the Amazon). The Amazon has most diversity in small trees. Gabonese forests have no middle storey and understorey.
Gabon has megafauna. Forest elephants are different from savanna elephants. They don’t knock over trees, they snap them to feed them. “In Africa you don’t need a machete to go through the forest, but you do need to be very careful”. Where there are no elephants the number of small saplings is indistuishable from the Amazon
How could he find an elephant free refuge to compare structure. They compared flat ground forests on slopes and tops of hills. But they found that the elephants go everywhere. Only one slope was so steep (36 degrees) that there was no elephant sign.
The peak height for trees pushed over by forests is 1-2 metres. Elephants are major filters on forest structure and diversity.
Yadvinder Malhi: the large trees are more abundant and live longer. Is there some sort of interaction where “weeding” of small plants enhances the lifetime of large trees?
There are two responses to herbivory: defence or tolerance (where you can bounce back)
John Terborgh: African forests are the most amazing and wonderful forest I have ever seen (and that is from a many who knows the Amazon forest better than anyone).
Andrew Balmford: How does the range contraction of Asian elephants (and forests in other parts of Africa).
Tree diversity in equatorial Africa is much lower than in the Amazon. 50-75/ha vs >200 Equatorial SA. Parmentier et al (2007) and others discuss that area, drought, fire, contraction through history are primary reasons for low species diversity
He will present biotic arguments rather than abiotic arguments for the low diversity.
Small islands such as the Solomons have twice the tree species diversity of Central Africa
The total flora of Gabon is quite rich (> 6000 species). In a tropical forest flora about a third of the flora are trees (around 2000 tree species). A hectare contains about 1/10 of regional (Gamma) diversity, so we would expect about twice as many species per hectare than we see.\
He plots species accumulation curves for various tropical forests. Cameroon is no different to other tropical forests with similar climates. The problem is the per hectare diversity is much lower. Why?
He compares Gabon with the Peruvian Amazon. Lots more trees per hectare in Peru (mean 618) than Gabon (around 420). When you look at forest structure,
Much much lower diversity in small and large saplings, somewhat lower than small trees. Most diversity in African trees is in the large trees (at similar levels of diversity to the Amazon). The Amazon has most diversity in small trees. Gabonese forests have no middle storey and understorey.
Gabon has megafauna. Forest elephants are different from savanna elephants. They don’t knock over trees, they snap them to feed them. “In Africa you don’t need a machete to go through the forest, but you do need to be very careful”. Where there are no elephants the number of small saplings is indistuishable from the Amazon
How could he find an elephant free refuge to compare structure. They compared flat ground forests on slopes and tops of hills. But they found that the elephants go everywhere. Only one slope was so steep (36 degrees) that there was no elephant sign.
The peak height for trees pushed over by forests is 1-2 metres. Elephants are major filters on forest structure and diversity.
Yadvinder Malhi: the large trees are more abundant and live longer. Is there some sort of interaction where “weeding” of small plants enhances the lifetime of large trees?
There are two responses to herbivory: defence or tolerance (where you can bounce back)
John Terborgh: African forests are the most amazing and wonderful forest I have ever seen (and that is from a many who knows the Amazon forest better than anyone).
Andrew Balmford: How does the range contraction of Asian elephants (and forests in other parts of Africa).