4.1 Effects of species diversity on invasion by P. kansuensis
Species richness in the area invaded by P. kansuensis was lower
than that of the non-invaded area after removing the P.
kansuensis population, which agreed with previous reports on how
greater species diversity or species richness can effectively resist
invasion by invasive species (Marvier and Smith, 1997), but the
difference between the invaded and non-invaded sites was small. In
contrast, the invaded area had a greater canopy cover, which means that
the communities with low species diversities are more conducive to
invasion by P. kansuensis . It is possible that species-rich
communities are more likely to contain species with stronger competitive
abilities, which allow them to effectively discourage invasive species
(El-Barougy et al., 2020). The results are also related to the root
hemiparasitic characteristics of P. kansuensis . Another reason
might be that a community with higher species diversity has a stronger
ability to compete for light, which makes it unfavorable for P.
kansuensis survival and growth. Some
researchers believe that invasion is a probabilistic process and that a
community that contains native species will have a higher plant
diversity level. They suggest that this improves the ability of a
community to efficiently resist invasive plants (Tilman, 1999; Fargione
et al., 2003; Fargione and Tilman, 2005). A further reason could be that
communities with high species diversities reduce the likelihood of
successful invasions by filling niche spaces with different resident
species that jointly and efficiently use local resources
(HilleRisLambers et al., 2012; El-Barougy et al., 2020). For example, a
field study on Rhinanthus alectorolophus showed that the presence
of R. alectorolophus increased total aboveground biomass in low
diversity plots, but had no effect on total aboveground biomass in high
diversity plots (Joshi et al., 2000).