Global effect of the mixture across exposure scenarios
There were no significant differences between expected and observed
values of mass loss (Fig. 2a) and the relative mixture effect was
additive across exposure scenarios (Fig. 3a). Most data points of alder
distributed below (Fig. 2b) while most data points of poplar distributed
above the 1:1 line (Fig. 2c), resulting in a significant interaction
between mixture effect and exposure scenario (Table 2). Despite a
significant difference between mass loss of poplar in the mixture and as
single species (F1,66=5.17, p <0.05;
Table 2), the relative individual performance was additive for both
species (Fig. 3d,f).
Sporulation rates and fungal richness were significantly higher
(F1,19>6.75, p <0.05; Fig.
2g,j; Table 2), while fungal biomass was significantly lower
(F1,34=5.26, p <0.05; Table 2, Fig. 2d)
in the mixture than the average of the single species. Overall, the
relative mixture effect on decomposers was synergistic (RME:
0.91 – 4.64) across exposure scenarios (Fig. 3a), due to increased
sporulation rates (RME: 2.51 – 14.44) and richness (RME: 0.56 – 1.90)
while the effect on biomass was additive (Fig. 3b). For alder, there
were no significant differences between expected and observed values of
any of the fungal variables (Fig. 2e,h,k). For poplar, sporulation rates
and richness were significantly higher
(F1,40>4.75, p<0.05; Table 2,
Fig. 2i,l) while fungal biomass was significantly lower
(F1,52=7.36, p<0.01; Table 2, Fig. 2f) in the
mixture than as single species. When all three fungal variables were
considered together, the relative individual performance on decomposers
was synergistic for both species (Fig. 3d,f), weaker for alder (RIP:
0.09 – 2.81) and stronger for poplar (RIP: 1.17 – 18.23). However, the
effect on each of the fungal variables differed between the two species.
In the case of alder, there was a huge variation in the deviation
between observed and expected values of fungal biomass, with a
synergistic effect for sporulation rates only (Fig. 3e) while in the
case of poplar there was a huge variation in the deviation between
observed and expected values of sporulation rates with additive effects
for all three fungal variables (Fig. 3g).
Most data points of shredder colonisation were distributed above the 1:1
line (Fig. 2m,n,o) resulting in a synergistic relative mixture effect
(RME: 0.48 – 1.37) on detritivores across exposure scenarios (Fig. 3a),
due to increased shredder biomass (RME: 0.66 – 2.98) and abundance
(RME: 0.23 – 1.35) while the effect on richness was additive (Fig. 3c).
The relative mixture effect on the process of decomposition (Fig. 6) was
globally synergistic across exposure scenarios (RME: 0.70 – 1.79due to
the increased decomposer and detritivore colonisation.