Vanessa Winchester assisting in core extraction © photo by A Jolly

Vanessa Winchester took her dendro-geomorphological skills to Berenty in May 2011 to investigate forest health, a subject of growing concern for the last 30 years. Clearly, if the lemurs are to survive they need a forest to survive in. There were five main questions to be answered: is climate change affecting the forest; is the water table dropping due to deforestation and soil loss in the Mandrare River headwaters; or are damaging floods eating away at the riverbank; or is increasing tourism or the introduction of non-local species affecting forest growth; or perhaps is it just that the forest trees are getting near the end of their life spans?

Dendrogeomorphology involves interpreting the history of trees in the context of their surrounding landscape. Vanessa together with Sahoby Marin Raharison (Forestry, University of Antananarivo, Madagascar) collected cores from the trunks of Tamarindus indica, Crataeva excelsa and Alluaudia procera. This part of the study has yet to be finalized. Sections from flood damaged, exposed tamarind roots were also collected. Analysis provided dates for flood years and locations of roots allowed estimation of riverbank erosion rates. Tree age was extrapolated from tree-growth rates/ring widths together with trunk circumferences. Interim results suggest that age, could be the problem with over 70% of the tamarind trees between 140 to 370 years old (tamarinds, the dominant trees in the forest, are commonly credited as having a life span of 200 years). Replacement with young seedlings is sparse since these do not thrive under a closed canopy and fast-growing invasive species are filling any gaps in the canopy left by fallen trees.

Read more about Vanessa on her Oxford home page:
Dr. Vanessa Winchester - School of Geography and the Environment, University of Oxford

Or contact her by email at: vanessa.winchester@geog.ox.ac.uk