Impact of global warming on tropical forest soils Soil microorganisms in tropical forests play a key role in the ecosystem’s carbon cycle. However, scientists are concerned that these microorganisms may be adversely affected by increased global temperatures, causing uncertainty in global carbon cycle models. Climate Change and Environment © Aleksandar Mijatovic, Shutterstock The EU-funded project TROPICALCARBON (Tropical forest soil carbon storage and microbial diversity under climatic warming) directly addressed this uncertainty towards future temperature changes using different approaches. The aim was to determine how soil chemistry and biology (in the form of functional biodiversity) regulate soil carbon storage under climatic warming. Researchers studied the effect of temperature on microbial diversity along a 3.4 km elevation gradient in the Peruvian Andes. They showed how temperature effects on the nitrogen cycle are closely linked to soil microbial metabolism by measuring changes in extracellular enzymes along this elevation gradient. Further investigation revealed that certain carbon degrading extracellular enzymes produced by microbial communities along this elevation gradient showed different temperature responses at different elevations. Such temperature-adaptive responses of enzymes support the idea that microbial communities can adapt to temperature change, regulating their metabolic rates (or enzymatic rates) with consequences for carbon storage. These findings were included in a collaborative global soil study, which found that ‘adaptive’ responses of microbial respiration rates were greater in soil from colder sites and in soils with high carbon-to-nitrogen ratios. The project also found evidence that temperature was directly driving both the diversity and the community composition and plants and soil microbial communities along this gradient. Soil translocation experiments were also conducted, whereby 50 cm deep soil monoliths were reciprocally transplanted between 4 sites along the gradient. It was found that carbon chemistry played a fundamental role in determining the rate of decomposition under warming. It was also shown that temperature-adaptive soil carbon recycling responses occur through changes in the composition of soil microorganisms. TROPICALCARBON also investigated short-term warming responses of lowland tropical forests in Panama. The analyses of soil microbial respiration and physiology demonstrated how phosphorus could play a pivotal role in regulating the stability of deep (below 50 cm) stores of soil carbon in tropical forest. Keywords Tropical forest, soil microorganisms, carbon cycle, TROPICALCARBON, climatic warming
