Secondary forest on bauxite in Bahia: methods and protocol

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Dary Rigueira, Brazilian ecologist at the Universidad Federal da Bahia, Salvador. Dary and myself designed a survey protocol that we hope will suggest suitable species for restoration

Dary Rigueira and myself designed a sample protocol for characterising the vegetation growing on disturbed sites on bauxite. We are hoping that by contrasting sites of different ages and disturbance histories we will be able to identify patterns which point to what determines the assemblages of species growing at a site and help us identify species which may be suitable for the rehabilitation of mined sites.  Our 44 study plots are between 3 and 20 years of age since deforestation and in which deforestation had been accompanied by top soil removal or burning and conversion to pasture or simply allowed to recover.

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A site two years after deforestation and topsoil removal. We also sampled 6- and 12-year old sites with this combination of treatments

At each site we make a number of observations about the vegetation, leaf litter and the soil. These include the height of the canopy, diameter of the trees composing the canopy, presence or absence of key plants such as bromeliads or mosses, identity of all the plants, compaction of the soil at three depths and many more. In total over twenty observations together with pictures of the understory, leaf-litter and root mat (see below):

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Patch of fifteen year old secondary forest floor with the leaf-litter removed so that we can see the all-important root mat. This site was cleared of trees and then allowed to regrow without being burnt or converted to pasture

As well as visual observation we are using a penetrometer to measure the compaction of the soil at different depths and collecting herbarium samples of any plants that we cannot readily identify in the field.  Measuring the compaction of the soil is important as this has a very big impact on soil health and can take a very long-time to recover. I have visited sites compacted by livestock in the 1950’s where you can still see the impact on the soil. It would therefore be safe to assume that this may play an important role in determining what will regenerate at a site. Taking herbarium specimens enables us to identify the material in the Kew Herbarium where we have over 7 million reference collections to compare them to and so ensure a very high quality of identification.

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