Selecting Populations for Non-Analogous Climate Conditions Using Universal Response Functions: The Case of Douglas-Fir in Central Europe

Abstract

Identifying populations within tree species potentially adapted to future climatic conditions is an important requirement for reforestation and assisted migration programmes. Such populations can be identified either by empirical response functions based on correlations of quantitative traits with climate variables or by climate envelope models that compare the climate of seed sources and potential growing areas. In the present study, we analyzed the intraspecific variation in climate growth response of Douglas-fir planted within the non-analogous climate conditions of Central and continental Europe. With data from 50 common garden trials, we developed Universal Response Functions (URF) for tree height and mean basal area and compared the growth performance of the selected best performing populations with that of populations identified through a climate envelope approach. Climate variables of the trial location were found to be stronger predictors of growth performance than climate variables of the population origin. Although the precipitation regime of the population sources varied strongly none of the precipitation related climate variables of population origin was found to be significant within the models. Overall, the URFs explained more than 88% of variation in growth performance. Populations identified by the URF models originate from western Cascades and coastal areas of Washington and Oregon and show significantly higher growth performance than populations identified by the climate envelope approach under both current and climate change scenarios. The URFs predict decreasing growth performance at low and middle elevations of the case study area, but increasing growth performance on high elevation sites. Our analysis suggests that population recommendations based on empirical approaches should be preferred and population selections by climate envelope models without considering climatic constrains of growth performance should be carefully appraised before transferring populations to planting locations with novel or dissimilar climate.

Varying selection differential throughout the climatic range of Norway spruce in Central Europe

“…). The effect of site climate on phenotypic variation was much larger than the effect of climate of population origins, as previously shown also for other conifers (Chakraborty et al., ; Wang et al., ). The observed effect of site climate suggests stronger climatic selection pressures at the colder end of the species distribution resulting in increasing tree height variation in colder and moister environments.…”

Plants adapted to warmer climate do not outperform regional plants during a natural heat wave

“…The strategy of assisted migration is based on the assumption that climate adaptation is the key driver of plant performance (Hewitt et al 2011;Sgr o et al 2011). Consequently, most practical recommendations rely on climatic models (Wang et al 2010;Iverson and McKenzie 2013;Ikeda et al 2014;Chakraborty et al 2015;Koralewski et al 2015;Yang et al 2015). Our results show that this can be misleading and that the translocation of warm-adapted ecotypes will not necessarily lead to an increase in performance in a warmer climate but that performance might even decrease, presumably because other adaptations to local or regional environmental conditions or biotic interactions play an even greater role than climate adaptation for the performance of the plants.…”

“…So far, most of the support for assisted migration comes from climate envelope models Hamann 2011, 2012) or from models connecting experimental data on plant performance with climate (Wang et al 2010;Iverson and McKenzie 2013;Ikeda et al 2014;Chakraborty et al 2015;Koralewski et al 2015;Yang et al 2015). However, the ultimate test of the effectivity of assisted migration is of course when plants adapted to the climate of another region outperform the local ones under climate change in a transplant experiment.…”

Genetic trials improve the transfer of Douglas‐fir distribution models across continents

“…In a recent study, we developed two universal response functions (URFs), that predict the intraspecific phenotypic variation of functional traits such as dominant tree height and basal area of the North American Douglas-fir Pseudotsuga menziesii for plantations in central Europe as a response to climatic drivers (Chakraborty et al 2015(Chakraborty et al , 2016. In URFs, the relationships between two functional traits (tree height and basal area) and the environmental variables are mathematically specified as causal relations allowing a mechanistic understanding of trait variation and species distribution although the model formulations are correlative and empirical in nature (Dormann et al 2012).…”