Effect of the mixture within exposure scenarios
Most mass loss data points of exposure 0:100 distributed above while
most data points of exposures 25:75 and 50:50 distributed below the 1:1
line (Fig. 2a) resulting in a significant interaction between mixture
effect and exposure scenario (Table 2) and in a weak synergistic
relative mixture effect (RME: 0.04 – 0.30) in 0:100 exposure only (Fig.
4a). The relative individual performance differed between the two
species. In the case of alder, most data points of exposure 0:100
distributed above the 1:1 line (Fig. 2b), there was an interaction
between mixture effect and exposure scenario (Table 2) and a synergistic
effect (RIP: 0.05 – 0.77) occurring in exposure 0:100 only (Fig. 5a).
In the case of poplar, most data points of exposure 50:50 distributed
above the 1:1 line (Fig. 2c) with a weak synergistic effect (RIP:
0.02 – 0.16) occurring in exposure 50:50 only (Fig. 5b).
The relative mixture effect on decomposers was synergistic in exposure
0:100 (RME: 0.14 – 4.69) while in exposures 25:75 and 50:50 the effect
was additive (Fig. 4b). The synergistic effect found in exposure 0:100
was due to enhanced sporulation rates (RME: 0.81 – 12.82; Fig. 4f) and
fungal richness (RME: 0.18 – 1.11; Fig. 4h), while the effect on fungal
biomass was additive (Fig. 4d). In exposure 25:75 there was a
synergistic relative mixture effect on fungal richness (RME:
0.70 – 2.23). When all fungal variables were taken together, the effect
of the mixture on decomposers was additive for both species in all
exposure scenarios (Fig. 5c,d). However, while for alder the effect was
additive for all fungal variables (Fig. 5e,g,i), for poplar the effect
was additive for fungal biomass (Fig. 5f) but there was a strong
synergistic effect on sporulation rates (RIP: 0.37 – 54.47) and a
weaker one on richness (RIP: 0.26 – 2.42) in exposure 25:75 (Fig.
5h,j).
The effect of the mixture on detritivores (Fig. 4c) was additive in
exposures 0:100 and 50:50 and synergistic in exposure 25:75(RME:
0.63 – 4.02), where all three shredder variables had
higher-than-expected values (Fig. 4e,g,i), with effects stronger for
biomass (RME: 0.09 – 9.14) and abundance (RME: 0.01 – 3.99) than for
richness (RME: 0.08 – 0.64).
The relative mixture effect on the process of decomposition (mass loss,
decomposers, and detritivores) was synergistic within all exposure
scenarios (Fig. 6), with effects stronger in exposures 25:75 (RME:
0.31 ‑ 3.07) and 50:50 (RME: 0.39 – 1.87) than in exposure 0:100 (RME:
0.22 – 1.60).