Both nutrient environment and the composition of established (resident) or native plant communities might be expected to influence the success of invasive species.
The fluctuating resource hypothesis suggests that resource fluctuation usually increases resource availability, which will provide invasion opportunities for non-native species, and the resident communities will be more susceptible to invasion.
The biotic resistance hypothesis proposed that more species rich communities might be more resistant to invasion, due to greater competition for resources with greater native richness.
In a study published in Environmental and Experimental Botany, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) used the invader Chromolaena odorata to experimentally test whether the fluctuating resource hypothesis is contingent on resident plant origin and species richness by planting the invader and resident species at the same time.
The researchers created a series of artificial communities with resident plants from native (Mexico) and non-native (China) ranges, in order to test how invasion is influenced by resource fluctuation, species range (native vs. non-native range), richness and their interactive effects. They replicated within and across 3 levels of species richness (1, 2 and 4 resident species communities) for a total of 315 experimental mesocosms.
They found that resident origin, nutrient treatment and species richness of artificial community had significant effects on invasion success of C. odorata. The effect of nutrient fluctuation on invasion success of C. odorata was contingent on resident origin, and this effect was weaker in more species rich communities.
Moreover, the invasion success of C. odorata was negatively related with biomass of resident plants in communities, suggesting competition as a mechanism governing invader success.
"Our results suggest that the fluctuating resource hypothesis will apply only to resident communities with lower resource acquisition strategies, relative to the invader," said Dr. ZHENG Yulong, principal investigator of the study.
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