For Africa’s valuable mahoganies, it’s the soil, stupid

Authors say results could have major impacts on ’green’ certification programs

A study by a scientist from the New York-based Wildlife Conservation Society has revealed how Africa’s giant mahoganies, the ancient trees driving the tropical logging industry, require specialized, poorly understood soil conditions – results that could have huge implications on how Africa’s tropical forests are managed.

The study, appearing in the latest issue of the journal Ecology, looked at four mahogany species in Dznagha-Sangha Dense Forest Reserve, a 1,700 square-mile region in Central African Republic. The authors found that that three of the four species required specialized soils – those with a particular combination of plant nutrients – and were restricted to these sites within the forest. Previous analyses of soils with respect to the distribution of these and other tropical tree species have looked at things like topography to infer soil conditions, completely missing the importance and complexity of soil chemistry.

According to the lead author of study, WCS Conservationists Dr. Jefferson Hall, the results could have far-reaching impacts on how forests are managed and maintained by logging regimes.

“In practical terms, regenerating these high value species, could be the difference between justifying reuse of a given forest for timber production, or converting it for other uses, such as agriculture,” said the study’s lead author, Dr. Jefferson Hall, a WCS conservationist.
Hall also believes the implications of this study on “green” certified timber, which require regeneration of harvested tree species, are huge. Hall said that the tradition throughout West and Central Africa has been one of mahogany “mining,” and that their subsequent lack of regeneration has caused loggers to simply move on to other species, which in turn has led to deforestation. The early stages of this vicious cycle are evident even in the most remote forests of Africa. Knowing and taking into account the regeneration requirements of these species when writing management plans will vastly improve the prospects for long-term management, Hall added.

The authors said that failure to really look at the importance of soil with regards to plant diversity has been largely ignored.

“Understanding how a tropical forest maintains its diversity is extremely important for conservation biologists,” said Hall. “One cannot hope to manage and protect a species within forests if one does not understand the processes that control their distribution.”