Assessment of two contrasting French Douglas-fir (Pseudotsuga menziesii) seed orchards: potential for adaptation to climate change
Résumé
Douglas-fir is the second most planted species in France. Eight seed orchards were established in France between 1978 and 1989 to ensure seed production. The progeny of one of the orchards (California – from the southern part of the natural range) has shown differences in phenology and Juvenile growth compared to the other orchards (from the northern part of the natural range). The study aims to assess the value of this genetic diversity (between orchards) in the context of climate change. Two experiments comparing the progeny from the California and Luzette orchards, either pure or mixed on a tree-by-tree basis, were measured between 2020 and 2023 for bud break and with automatic dendrometers. The results from four years of contrasting climates show that the progeny from the two orchards seem to have different strategies in response to drought, depending on its timing and intensity, without concluding a better tolerance. The progeny from the California orchard experiences increased competition in mixtures due to its inferior juvenile growth, while allowing for the establishment of a high-quality stand in pure plots. This study expands knowledge on the drought adaptation potential of French Douglas-fir genetic resources and helps define the limits of their use.
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