Stable isotopes and metabolite profiles as physiological markers for the drought stress sensitivity
Final Report Abstract
When assessing stable isotopes in different tissues for their suitability as markers for drought sensitivity of Douglas-fir provenances the following main conclusion can be drawn. During extreme dry and hot periods stable isotopes in tree rings give valuable information on the physiological background of growth changes by allowing to reconstruct stomatal responses and photosynthetic activity under extreme conditions. There was however no clear relation between the physiology- and growth-related drought sensitivity and the environmental conditions at the site of origin of the provenances. This makes a straightforward selection of the provenances from an assessment of the original growing conditions in North America impossible. It needs to be explored in more detail if mainly the frequency of climatic extremes at the site of origin determines drought resistance. We have also observed a trade-off between long-term growth performance under ‘average’ conditions and the response to extreme events. This trade-off needs to be taken into account for a sustainable and economically successful cultivation of Douglas-fir in future and thus site specific evaluations of the probability of extreme drought events in future will help to select the appropriate provenances. The totally different behaviour of some provenances to the extreme year 2003 at the two sites in the Rhine valley (Wiesloch and the valley site of the Freiburg transect) also calls for site specific assessment. Mainly drought avoidance strategies related to deeper rooting patterns might strongly depend on the soil type and depths of a given site and might mainly drive physiological responses of provenances in extreme years. Water uptake assessment with 18O and 2H water isotopologues would offer a useful tool to address this point in future.
Publications
- 2012. Tree ring isotopic composition, radial increment and height growth reveal provenance-specific reactions of Douglas-fir towards environmental parameters. Trees 27:37–52
Jansen K, Sohrt J, Kohnle U, Ensminger I, Gessler A
(See online at https://doi.org/10.1007/s00468-012-0765-9)
