Plant functional traits differ in adaptability and are predicted to be differentially affected by climate change

1. Climate change is testing the resilience of forests worldwide pushing
physiological tolerance to climatic extremes. Plant functional traits have
been shown to be adapted to climate, and have evolved patterns of trait
correlations (similar patterns of distribution) and coordinations
(mechanistic trade-off). We predicted that traits would differentiate
between populations associated with climatic gradients, suggestive of
adaptive variation, and correlated traits would adapt to future climate
scenarios in similar ways. 2. We measured genetically determined trait
variation and described patterns of correlation for seven traits:
photochemical reflectance index (PRI), normalized difference vegetation
index (NDVI), leaf size (LS), specific leaf area (SLA), δ13C (integrated
water use efficiency, WUE), nitrogen concentration (NCONC), and wood
density (WD). All measures were conducted in an experimental plantation on
960 trees sourced from 12 populations of a key forest canopy species in
southwestern Australia. 3. Significant differences were found between
populations for all traits. Narrow-sense heritability was significant for
five traits (0.15 to 0.21), indicating that natural selection can drive
differentiation; however, SLA (0.08) and PRI (0.11) were not significantly
heritable. Generalised additive models predicted trait values across the
landscape for current and future climatic conditions (>90%
variance). The percent change differed markedly among traits between
current and future predictions (differing as little as 1.5% (δ13C) or as
much as 30% (PRI)). Some trait correlations were predicted to break down
in the future (SLA:NCONC, δ13C:PRI, and NCONC:WD). 4. Synthesis: Our
results suggest that traits have contrasting genotypic patterns and will
be subjected to different climate selection pressures, which may lower the
working optimum for functional traits. Further, traits are independently
associated with different climate factors, indicating that some trait
correlations may be disrupted in the future. Genetic constraints and trait
correlations may limit the ability for functional traits to adapt to
climate change.