Short- and long-term growth response to multiple drought episodes:
evidence of genetic adaptation in a conifer species
Abstract
Drought tolerance of tree species is a concern in the context of climate
change, and tree ring analyses can be used to assess past growth
response(s) to drought events. In this study we applied this approach to
1,281 individuals with known pedigree in long-term genetic test
plantations of lodgepole pine in western Canada. We assessed resistance,
resilience and recovery metrics, and analyzed their causal relationships
with long-term growth and susceptibility to disease through structural
equation modeling. We found that trees with low short-term resilience to
drought events also experienced severe reductions in long-term growth.
Narrow-sense heritability of drought tolerance metrics was low for
short-term responses at specific sites, but a new long-term decline
index for families showed moderate genetic heritability (h ̵̂^2 of
0.15 to 0.30 ± 0.03). We also detected evidence of local adaptation,
with trees from lower elevation showing better drought adaptation. We
conclude that selection of genotypes for drought tolerance is possible,
and that other species or populations could be screened using this
method. We also note that the new long-term decline index developed in
this study shows a higher degree of genetic control than other metrices,
and may therefore be of broader interest in dendrochronological
research.