Effects of the biotic and abiotic factors on invasions of
different plants
The biomass of A. philoxeroides and E. crassipes decreased
as the performance of co-occurring exotic plants
(Pexotic_quadrat ) increased, but the biomass ofC. caroliniana was not affected byPexotic_quadrat (Fig. 3A). As the richness
(Rnative_quadrat ) and performance
(Pnative_quadrat ) of native plants increased,
the biomass of A. philoxeroides , E. crassipes , andC. caroliniana all increased (Fig. 3B, C). The best-fit SEMs
revealed that the Rnative_quadrat andPnative_quadrat affected the biomass of three
plants in different ways. Pnative_quadrataffected the biomass of A. philoxeroides and E. crassipesdirectly and indirectly by negatively influencing thePexotic_quadrat , whereas, it only had a direct
effect on the biomass of C. caroliniana ;Rnative_quadrat had direct and indirect effects
on the biomass of A. philoxeroides and E. crassipes , but
only an indirect effect on the biomass of C. caroliniana . (Fig.
4B-D). None of the three plants showed a decrease in biomass as
defoliation increased (Fig. 3D), which suggests that herbivory does not
control the invasion of aquatic plants.
As T increased, the biomass of A. philoxeroides increased,
but the biomass of E. crassipes decreased (Fig. 3E). T not
only had a direct positive effect on the biomass of A.
philoxeroides , but also had indirect effects on the latter by
negatively influencing the Rnative_quadrat and
positively influencing the Pexotic_quadrat (Fig.
4B). Whereas, high T increased the biomass of E. crassipesonly by indirectly reducing the Rnative_quadratand Pexotic_quadrat (Fig. 4C). The biomass ofA. philoxeroides and C. caroliniana increased with the
increased Nwater (Fig. 3F). HighNwater could directly increase the biomass ofC. caroliniana and indirectly by reducing theRnative_quadrat , while it only increased the
biomass of A. philoxeroides indirectly by reducing theRnative_quadrat (Fig. 4B, D).Nwater also affected the biomass of E.
crassipes by negatively influencing theRnative_quadrat (Fig. 4C), even though
regression analysis showed no significant correlation betweenNwater and the biomass of E. crassipes (P
> 0.05). Similarly, although the relationships between theHquadrat and the biomass of E. crassipes ,A. philoxeroides and C. caroliniana were not significant
(Fig. 3G), SEMs showed that Hquadrat could affect
the biomass of A. philoxeroides and C. caroliniana by
influencing the Pexotic_quadrat andRnative_quadrat positively or negatively (Fig.
4B, D).