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.