Abstract
Trees’ total amount of nonstructural carbohydrate (NSC) stores
and the proportion of these stores residing as insoluble starch
are vital traits for individuals living in variable environments.
However, our understanding of how stores vary in response to
environmental stress is poorly understood as the genetic component of
storage is rarely accounted for in studies. Here, we quantified
variation in NSC traits in branch samples taken from over 600 clonally
transplanted black cottonwood (Populus trichocarpa) trees grown
in two common gardens. We found heritable variation in both total NSC
stores and the proportion of stores in starch
(H2TNC = 0.19,
H2PropStarch = 0.31), indicating a
substantial genetic component of variation. In addition, we found high
amounts of plasticity in both traits in response to cold temperatures
and significant genotype-by-environment (GxE) interactions in the total
amount of NSC stored (54% of P is GxE). This finding of high GxE
indicates extensive variation across trees in their response to
environment, which may explain why previous studies of carbohydrate
stores’ responses to stress have failed to converge on a consistent
pattern. Overall, we found high amounts of environmental and genetic
variation in NSC storage concentrations, which may bolster species
against future climate change.