How do tropical forests respond to climate change?

The forests have then tempered climate change to some extent. Dr Pieter Zuidema of Wageningen University is studying whether the increased growth rate of tropical trees began earlier and possible causes of the growth spurt. This should lead to better predictions of how tropical forests will respond to climate changes in the future.

Zuidema is doing his research in the Department of Forest Ecology and Forest Management of Wageningen University. 'Using growth ring measurements, isotope analysis and simulation models, we are trying to reconstruct the historical growth of tropical trees', said Zuidema. 'I am glad that our department has so much expertise on growth rings and tree growth models. That has given my project a flying start.'

The research is being done in forested regions of Bolivia, Cameroon and Thailand.  Drill cores and stem discs are being collected from 15 tree species and 1,500 individual trees. The work is being carried out by three PhD students, a post-doc and an analyst. 'The field work is now in full swing.  One of my PhD students just returned from Thailand with 600 drill cores, each packaged individually in McDonalds straws. On the trip back, customs was pretty interested in those too! Another PhD student reported that he had already ruined three Swedish increment borers on the hard Cameroonian trees. It's a tough material.'

Using the growth-ring analysis, Zuidema is seeking gradual changes in ring thickness. The analyses of stable isotopes are used to reconstruct variations in the climate in the past and to determine the physiological response of trees to increased Co2 concentrations. 'We are about to recruit a post-doc to develop tree growth models. The models should help us explain the recent growth spurt of tropical trees.  With those insights, we should be better able predict how tropical trees will respond to climate changes in the future.'