Results

Averaged across the harvest time and soil treatments, invasive plant species tended to produce higher total biomass (+102.5%) than native plants species (marginally significant effect of invasion status; Table 1; Figure 2A). Total biomass production was significantly increased over time (+88.0%) (significant effect of harvest time; Table 1 & Fig. 2A), and the increase in total biomass was significantly stronger for invasive plant species (+112.1%) than for native plant species (+49.0%) (significant effect of invasion status × harvest time; Table 1 & Figs. 2A & S1) over time. But root mass fraction was significantly decreased over time (-3.3%) of the plants (significant effect of harvest time; Table 1 & Fig. 2B), and this effect were stronger on native plant species than on invasive plant species, the decrease in root mass fraction of native plant species (-17.0%) over time, but increased of invasive plant species (+11.8%) (significant effect of invasion status × harvest time; Table 1 & Figs. 2B & S1) over time. The presence of soil microbes significantly decreased the root mass fraction (-13.6%) of the plants (significant effect of soil; Table 1 & Figs. 2B & S2).
For total biomass of the plants, we found a marginally significant three-way interaction of the invasion status, harvest time and soil microbes treatments (marginally significant effect of plant invasion status × harvest time × soil; Table 1 & Fig. 2A). Specifically, the presence of soil microbes decreased the total biomass of invasive plant species when at second harvest (-14.5%), however, under the other three combinations of harvest time and invasion status treatments, it tended to increase total biomass (first & invasive: +4.1 %; first & native: +7.3%; second & native: +2.7%).
Separate analyses of the main and interactive effects of plant invasion status, soil, harvest time treatments on total biomass found that significant differences in invasion status on Sphagneticola ,Paspalum , and Solidago (Table S3; Figs. 2a-1 to a-3), and significant differences in harvest time on Sphagneticola andPaspalum (Table S3; Figs. 2a-1 & a-2). Significant interactions between invasion status and soil treatments, and significant interactions between invasion status and harvest time treatments were found in Paspalum (Table S3; Fig. 2a-2). Significant interactions between invasion status and harvest time treatments were found inSolidago and Alternanthera , respectively (Table S3; Figs. 2a-3 & a-4). In addition, significant three-way interaction was found in Paspalum (Table S3; Fig. 2a-2).
Separate analyses of the main and interactive effects of plant invasion status, soil, harvest time treatments on root mass fraction found that significant differences in invasion status on Sphagneticola ,Paspalum , and Alternanthera (Figs. 2b-1, b-2 & b-4), and marginally significant differences in invasion status on Solidago(Table S4; Fig. 2b-3). Significant differences in harvest time onPaspalum (Fig. 2b-2), and marginally significant differences in harvest time on Sphagneticola , Solidago andAlternanthera , respectively (Table S4; Figs. 2b-1, b-3 & b-4). Soil treatment had a significant effect on three congeneric pairs of invasive and native plant species (Table S4; Figs. 2b-1 to b-3). Significant interactions between invasion status and harvest time were found in Paspalum and Alternanthera (Table S4; Fig. 2b-3 & b-4). Significant interactions and marginally significant interactions between invasion status and soil treatments was found inPaspalum and Solidago , respectively (Table S4; Fig. 2b-2 & b-3). But only significant interactions between soil and harvest time treatments was found in Solidago (Table S4; Fig. 2b-3). In addition, two significant three-way interaction were found inPaspalum , and Solidago (Table S4; Fig. 2b-2 & b-3).