The Drought Impact on the Climate Benefit of Carbon Sequestration

Increases in atmospheric CO2 have resulted in significant changes in global climate and ecosystem processes. It is well known that the terrestrial biosphere fixes large quantities of carbon from the atmosphere. Still, less certain is whether soil and terrestrial vegetation can mediate the increase in CO2 and for how long. Carbon storage largely depends on water constraints, and climate models predict drier future conditions, particularly in the Mediterranean. Although droughts are associated with reductions in photosynthetic rates, their effect on the role of forests in climate change mitigation is still unclear. The Drought Impact on the Climate Benefit of Carbon Sequestration project aims to advance understanding of the impact of soil moisture on forests-avoided warming and for how long it occurs by achieving three objectives: i) simulate the effect of drought on the global terrestrial biosphere C cycle under global warming scenarios, ii) develop a mechanistic model based on experimental observations to represent the carbon cycle dynamics under drought conditions in a Mediterranean forest, and iii) compare the warming produced by CO2 emissions and that avoided by Mediterranean forests under drought scenarios. These objectives will permit answering whether the climate benefit of C sequestration is sensitive to drought conditions on a global and local (Mediterranean) scale and whether Mediterranean forests mantain their offset CO2 emissions under these conditions. The above will be carried out by linking photosynthesis, storage and respiration processes through the combination of Transit Time, Carbon Sequestration, and the Climate Benefit of Sequestration concepts with measurements from a unique long-term drought experiment, the compartmental system approach and global carbon cycle models. This project will result in relevant scientific contributions and a valuable and comprehensible tool to enhance policy-oriented discussion on nature-based climate mitigation.