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Adaptation du douglas (Pseudotsuga menziesii (MIRB.) FRANCO) aux changements climatiques : étude rétrospective basée sur l’analyse des cernes

Abstract : Forest response to the drought increase associated to the climatic warming relies on tree adaptive potential, i.e. the genetic variation and the heritability of adaptive traits involved in resistance to drought. In the first chapter, we identify easy-to-measure proxies of adaptive traits for resistance to drought. We compare the wood microdensity of dead and surviving trees after the 2003 heat wave in France. The most discriminating variables are the mean density of high and lowdensity segments, high-density proportion and coefficient of variation of the lowdensity segment. The wood of the surviving trees is always denser and more heterogeneous. If these adaptive traits are variable and heritable, then it is possible to select for improved resistance to drought in the breeding population as well as in natural regeneration. Our results also suggest that directional selection is going on in more or less water-stressed environments. The direction is variable according to the nature of the selection pressure in the different regions. In the Chapter II, we estimate the evolutionary potential to drought of the introduced Douglas-fir in France. This evolutionary potential relies on the magnitude of the genetic variation and of the heritability of the adaptive traits found in the first chapter. The heritability and the genetic variation are highly variable between provenances, sites and, to a much lower extent, between annual rings. Most variables have moderate to high heritability estimates for at least some provenances in some sites. Some traits tend to have generally higher heritability and genetic variation estimates. These are mostly variables of the density part of the annual ring. The variables having at the same time relatively high estimates of heritability and genetic variation are good candidates for becoming efficient selection traits for resistance to drought in tree breeding as well as in natural regeneration. The significant between-site variation suggests that the heritability estimates increase with site quality. The estimates are also significantly different between provenances with a strong provenance × site interaction. Conversely there is little significant between annual-ring variation. The chapter III takes advantage of the annual-ring variation to study the relationships between the genetic parameter estimates and climatic and soil variables. The heritability and genetic variation estimates of most variables significantly relates with most tested environmental variables. Very few variables never correlates with any environmental variable. The significant relationships are very variable between traits, provenances and sites. The most important predictors are temperature, evapotranspiration, and soil water reserve and water deficit. Rainfall marginally influences the genetic parameter estimates. Generally, the better the growing conditions, the higher the estimates. All components of the experimental trials affect the genetic parameters estimates. Thus, the choice of the plant material and of the experimental site strongly determines the genetic parameter estimates. The uncontrolled climatic variation may randomly affect the estimates.
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Submitted on : Wednesday, June 19, 2019 - 5:14:27 PM
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Manuela Ruiz Diaz Britez. Adaptation du douglas (Pseudotsuga menziesii (MIRB.) FRANCO) aux changements climatiques : étude rétrospective basée sur l’analyse des cernes. Climatologie. Institut agronomique, vétérinaire et forestier de France, 2016. Français. ⟨NNT : 2016IAVF0011⟩. ⟨tel-02160493⟩



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