Dynamic interactions between CO2 efflu, sap flow and internal CO2 concentration in tree stems: implications towards the assessment of actual stem respiration

In order to verify whether forests are net sinks of CO2, it is necessary to accurately quantify the photosynthesis (CO2 uptake) and respiration (CO2 release) by trees. The objective of the Ph.D. was to perform fundamental research on dynamics in respiration of tree stems. It became clear that measurements of stem CO2 efflux with cuvettes, which have been used as a measure of stem respiration in numerous studies, do not reflect the actual respiration of the stem because also factors other than respiration affect the stem CO2 efflux. To obtain better insight in the processes that influence CO2 efflux, the internal CO2 concentration in tree stems was measured. Recently developed sensors that allow continuous monitoring of internal CO2 concentration were tested and applied. First, experiments were conducted in growth chambers under controlled environmental conditions and then in the field under natural weather conditions. The experiments revealed that because of a large resistance for radial CO2 diffusion, some respired CO2 does not diffuse out of the stem, but is internally stored or transported with the transpiration stream. This implies that besides measurements of CO2 efflux, also measurements of internal CO2 concentration and sap flow are indispensable for quantifying the stem respiration. Another part of respired CO2 can be re-fixed by stem photosynthesis under light. In order to quantify the actual stem respiration, stem photosynthesis needs to be avoided by shielding the stem from sunlight. It was furthermore demonstrated that stem respiration is not solely dependent on temperature, as is often claimed, but also on the water status of the stem. If we want to model stem respiration accurately, both temperature and stem water status need to be considered as driving variables.

Author dc:creator

• Saveyn, An

Contributors dc:contributor

• Lemeur, R

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

und

Identifier

https://biblio.ugent.be/publication/467865
http://doi.org/1854/8237
https://biblio.ugent.be/publication/467865/file/1880228

OAI identifier oai:identifier

oai:archive.ugent.be:467865