Sample collection
We collected branch samples from two Department of Energy (DOE) common gardens in Oregon, USA in January of 2017. The gardens are located near Clatskanie, Oregon (46.12˚N, 123.27˚W; MAT = 10.4oC, MAP = 1,545 mm) and Corvallis, Oregon (44.56˚N, 123.26˚W; MAT = 11.2oC, MAP = 1,030 mm) respectively, which represent contrasting environments with similar daylength patterns (Figure 2A). Each garden contains the same 1,000+ unique genotypes, collected as branch cuttings from individuals located in 19 native populations (Figure 1). These cuttings were replicated clonally 3 times each and planted out in three randomized replicates in 2009, for a total of approximately 3,000 trees in each garden. The collection of each accession is described in Slavov et al. (2012) and their full genomic sequences are available on phytozome (Evans et al., 2014). In the winter of 2013-2014, all replicates in Corvallis and one replicate in Clatskanie were coppiced (aboveground biomass harvested) (Figure 1).
We sampled from a subset of the total 3,000 individuals per garden due to the high cost of NSC analysis in both time and lab disposables. In order to parse heritable variation, we aimed to sample all of the replicates of the same three to five genotypes from each population across the two gardens (Table S1). However, some populations had high mortality, leading us to eventually exclude the two latitudinally extreme populations from the final analysis of plasticity due to lack of replication (Kitimat & Tahoe). In all we sampled 245 individuals representing 64 unique genotypes (Table S1). To this dataset, we added samples collected across a genomically diverse set of individuals in Corvallis that added substantially to the number of genotypes measured per each population (Table S1). These additional samples provided much more power for parsing within versus among population variation, a requisite step for assessing local adaptation. The result was a total of 551 individuals from 392 unique genotypes sampled in Corvallis and 65 individuals from 64 unique genotypes sampled in Clatskanie (Table S1). We accounted for uneven replicate and within population sampling in our models described below.
We collected branch wood samples from coppiced replicates between January 6th and January 11th 2017, between 7 A.M. and 4 P.M. using pruning shears. We took all branch samples as 2cm segments from the previous growing season’s growth segment (2015) of coppiced replicates as it was accessible across all individuals. All samples were kept on dry ice during field collection, then shipped overnight to Cambridge, MA and stored at -80OC. In total, we collected and processed 616 branch samples (Figure 1). We collected additional stem and root tissue during this time period and included aspects of this work in the discussion for comparison (Blumstein et al., 2020)(Table S2). Non-coppiced trees in Clatskanie had an average diameter at breast height (DBH) in 2016 of 155.2 ± 46.9 mm, while coppiced trees averaged 84.0 ± 28.0 mm. DBH in Corvallis across all coppiced replicates in 2016 was 44.4 ± 14.9 mm.