Not all plant invasions are the same. Research by Oduor and colleagues in Ecology shows that sometimes invasive plants can assist each other when taking over territory. However, for this to happen, the soil conditions have to be right. The findings have important implications for ecosystem management and invasive species control.
Oduor and colleagues examined plant invasions in the light of two hypotheses. The stress-gradient hypothesis predicts that when soil lacks nutrients or water, plants are more likely to help each other out rather than compete. The other hypothesis was the invasional meltdown hypothesis. This proposes that the effects of invading species can compound and magnify their effects on native species.
Using a variety of plants grown in a greenhouse to simulate a plant invasion, the team found that invasive plants did indeed help each other in stressed conditions. Additionally, the native plants also aided the invaders, supporting both the stress-gradient and invasional meltdown hypotheses.
However, when grown in nutrient-rich soil, invasive plants performed poorly as they competed for the same resources. This suggests nutrient enrichment may not always benefit invasive species as previously thought. Water mattered too, with well-watered conditions favouring invasive plants over natives. Drought stress levelled the playing field between invasive and native species.
The findings suggest the need for a nuanced approach to invasive species control, including the need to prevent the establishment of multiple invasive species in nutrient-poor habitats.
Oduor, A. M. O., H. Yu, and Y. Liu. 2024. “Invasive Plant Species Support Each Other’s Growth in Low-Nutrient Conditions but Compete When Nutrients are Abundant.” Ecology e4401. https://doi.org/10.1002/ecy.4401
