How much do tree stems really respire?

Stem respiration by trees is a large but poorly understood part of the global carbon cycle.

Living, respiring tissues are found through much of tree stems and quantifying stem respiration accurately is difficult due to processes such as CO2 transport in sap flow and stem photosynthesis that decouple the respiration from its easily measured proxy, the CO2 escaping through the bark.This project will quantify the among-species variation and climate change responses in stem respiration in species from three major forest biomes.

Recent methodological advances have described approaches for continuous quantification of stem gas fluxes, sap flow and stem diameter using portable low-cost instruments allowing for measurements at an unprecedented scale and level of detail.The project is hosted by the University of Gothenburg with Gothenburg Botanical Garden and the University of Rwanda as collaborators.

Field measurements are planned during project years 1-2 (Rwanda) and 2-3 (Sweden). Growth chamber experiments are planned for years 1-4. A biochemical stem respiration model will be used to explore the implications of the findings starting from year 3.

Publication and conference participation are planned for years 2-4.The project will result in better process-knowledge of stem respiration that is urgently needed for more accurate tree- and ecosystem-scale respiration estimates and for improving the model predictions of climate change responses used for global policy decisions