Introduction

Predictions of how tropical forests respond to climate change are needed over timescales of decades and centuries. However, our ability to assess changes over long timescales is limited by the amount of time we have been able to observe systems. Relating spatial variation in ecological variables to environmental gradients provides a space-for-time substitution potentially providing insights into these longer-term responses.

Methods

The aboveground carbon stocks, rate of aboveground wood production and carbon residence time was assessed in 590 forest plots located across the tropical rainforest biome. Spatial variation in these variables was related to environmental variation.

Results

Carbon stocks declined with increasing daytime temperature, with the rate of decline steepening in the hottest forests. Carbon stocks also increased with dry season precipitation. Thus carbon stocks were lowest in the hottest and driest forests.

Implications

Our estimate thermal sensitivity of tropical forests is lower than some studies using inter-annual variation, but lies within the range of temperature sensitivities of CMIP5 models. Many areas of South American forest are expected to reduce in carbon stocks under moderate future warming, even after accounting for CO2 fertilisation.