Last week, during the Netherlands Annual Ecology Meeting, Peter van der Sleen won the Best Paper Award of the Netherlands Ecological Research Network (NERN). This award is for papers on ecological or evolutionary topics written by PhD candidates of a Dutch or Belgian institute. Peter wrote his paper, that was published in Nature Geoscience, when he was a PhD student at the Forest Ecology and Forest Management group.
In their prize winning paper No growth stimulation of tropical trees by 150 years of CO2 fertilization but water-use efficiency increased, Peter van der Sleen and his colleagues conclude that “the widespread assumption of a CO2-induced stimulation of tropical tree growth may not be valid.” Amongst the co-authors are Mart Vlam, Frans Bongers and Pieter Zuidema. The paper is evaluated by independent reviewers, who qualified it as ‘Excellent work overall, very solid and intriguing, challenging, no negative points’.
Summary of the paper: The biomass of undisturbed tropical forests has likely increased in the past few decades, probably as a result of accelerated tree growth. Higher CO2 levels are expected to raise plant photosynthetic rates and enhance water-use efficiency, that is, the ratio of carbon assimilation through photosynthesis to water loss through transpiration. However, there is no evidence that these physiological responses do indeed stimulate tree growth in tropical forests. Here we present measurements of stable carbon isotopes and growth rings in the wood of 1,100 trees from Bolivia, Cameroon and Thailand. Measurements of carbon isotope fractions in the wood indicate that intrinsic water-use efficiency in both understorey and canopy trees increased by 30–35% over the past 150 years as atmospheric CO2 concentrations increased. However, we found no evidence for the suggested concurrent acceleration of individual tree growth when analysing the width of growth rings. We conclude that the widespread assumption of a CO2-induced stimulation of tropical tree growth may not be valid. We conclude that the widespread assumption of a CO2-induced stimulation of tropical tree growth may not be valid.