Comparing morphological vs ecophysiological traits
The PCA constructed only from morphological traits separated species
according to leaf structure (PC1: C, N, C:N, LDMC, LT) and plant size
(PC2: width, height, LA, Root.w, Figure 2a,c). The PCA with only
ecophysiological traits separated species based mainly on their gas
exchange (PC1: E, WUEintr, WUEinst, GS,
R) and water use strategy (PC2: δ13C,
δ18O, GS, depth, Figure 2b,d). The second axes of both
PCAs (i.e. describing size/ water use strategy) correlated with species’
frequency response to transplantation (χ2(1) = 12.3, p
< 0.001 and χ2(1) = 9.1, p = 0.003) and did
so as described above for the full trait PCA (i.e. small species with
prolific water use decreasing at warmer sites; Figure 1b,c). The second
axis of the ecophysiological PCA describing water use strategy
(χ2(1) = 4.54, p = 0.03) also predicted species cover
change but it was the first axis of the morphological PCA describing
leaf structural traits that was associated with cover change
(χ2(1) = 7.81, p = 0.005; species with thick,
nitrogen-rich leaves reducing in cover, Figure S11c,d). The amount of
variation in the cover or frequency response explained by the LMMs did
not depend on whether all traits, only morphological traits, or only
ecophysiological traits were included (Table S3).
The two PCAs correlated significantly with each other (RV = 0.37, p =
0.01, Figure S14), even though most of the pairwise correlations between
morphological and ecophysiological traits were non-significant (Figure
S15). Using only size-related morphological traits or only
ecophysiological traits resulted in a similar ranking of the winning and
losing species (Figure 4), whereas the ranking based on leaf structural
traits was different (Table S7).