Abstract
Few studies have evaluated the relative importance of various factors in
the invasion process of exotic plants in freshwater ecosystems due to
the difficulty of observing numerous factors simultaneously. In this
study, to explore how various biotic and abiotic factors determine the
overall invasion extent of all exotic plants and the invasion extent of
different life-form exotic plants as well as assess their relative
importance, we surveyed 236 exotic aquatic plant communities using 2267
fine quadrats in China’s freshwater ecosystems. We found that
competition from native plants was the most vital factor determining the
mean biomass of all exotic plants and biomass of submerged plantCabomba caroliniana , while competition from co-occurring exotics
was the most important for biomass of emergent plant Alternanthera
philoxeroides and free-floating plant Eichhornia crassipes . The
population biomass of different exotic species responded differently to
climate change. Water eutrophication could accelerate the invasion of
exotic plants by directly favoring them and indirectly weakening the
resistance of native plants. Water depth, habitat size, herbivory, and
anthropogenic disturbance had relatively weak impacts on the biomass of
exotic plants. Moreover, some factors have different modes of influence
on different exotic plants. Our study suggested interspecific
competition plays a more important role in the population spread of
exotic plants than climate and abiotic environment once the plants have
successfully established, implying that biodiversity conservation and
vegetation restoration were the fundamental methods to control invasion.
In addition, our study highlights the importance of studying the overall
invasion extent of all exotic plants and interactions among invaders in
multi-invader communities.