3.1 Biomass Production
Species biomass was best explained by the full model (𝛿AIC =
7.31) including site, species, an interaction between site and species,
an interaction between climate and soil, and a three-way interaction
between climate, species and soil (F35, 133 =
11.22, p < 0.001). Prevalence of interactions across all
explanatory factors reveal highly contingent biomass dynamics. Lower
species-specific biomass was observed at Bayreuth (350 m) than at Fendt
(550 m) and Stubai (1850 m) (TukeyHSD, p < 0.001, p =
0.016 respectively). All species produced more biomass at Fendt (550 m)
compared to Graswang (850 m), Esterberg (1300 m), Furka (2440 m)
(TukeyHSD, all p < 0.001) and Stubai (1850 m) (TukeyHSD, p =
0.021). Lower species-specific biomass occurred at Furka (2440 m) than
at Stubai (1850 m) (TukeyHSD, p = 0.006). Species differed in biomass
production across all climates except Esterberg (1300 m), with no
species consistently producing the most biomass across all sites
(Fig. 3 ).
Individual biomass was best explained by the model including climate,
soil, an interaction between climate and species, as well as an
interaction between soil and species (F20, 148 =
11.22, p < 0.001). This contrasts with the best-performing
model explaining community biomass, which was the full model.
Interestingly, community biomass hierarchies were generally conserved
when measured using individual-level biomass (unlike at the species
level). Lower individual biomass was measured at Bayreuth (350 m) than
at Fendt (550 m) and Esterberg (1300 m) (TukeyHSD, both p <
0.001), while higher individual biomass was recorded at Fendt (550 m)
than Graswang (850 m), Stubai (1850 m), and Furka (2440 m) (TukeyHSD, p
< 0.001, p = 0.006, p < 0.001 respectively). Higher
individual biomass was measured at Esterberg (1300 m) than Graswang (850
m) and Furka (2440 m) (TukeyHSD, both p < 0.001), while Stubai
(1850 m) had higher individual biomass than Furka (2440 m) (TukeyHSD, p
= 0.001). Individual biomass production differed by species. Different
dominance hierarchies were observed when the number of individuals was
accounted for than when biomass was pooled at the species level in all
sites but Esterberg (1300 m). While species-level biomass was not
affected by soil type (F1, 167 = 0.34, p =
0.562), individual biomass was, with reference soil having a higher
individual biomass across all climates than local soil
(F1, 167 = 14.85, p < 0.001).
Interestingly, the higher individual biomass corresponded to the
reference soil also having a higher root biomass and lower survival when
compared to the local soil (F1, 58 = 7.698, p =
0.007; F1, 58 = 15.68, p < 0.001
respectively). This revealed an interesting survival dependent positive
relationship between the individual biomass and the species biomass in
each community (Fig. 4 ).