Previous studies have showed that the interactions between Nitrogen availability and atmospheric CO₂ concentration are critical to predicting the competitive consequences among invasive and native species in an increasingly eutrophic biosphere. However, little effort has been made to understand the interactive effects of these factors on invasive plants, especially in terms of functional traits.

Dr. LEI Yanbao and his colleagues of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study to explore the effects of CO₂ enrichment, N deposition, and their interactions on a subtropical invader Eupatorium adenophorum and its native congener E. stoechadosmum in terms of growth and ecophysiological traits relating to energy gain and cost.

In the study, invasive Eupatorium adenophorum and native congener E. stoechadosmum were compared at ambient and elevated atmospheric carbon dioxide (CO₂) concentrations combined with three levels of nitrogen (N; reduced, control and increased) in terms of growth, energy gain, and cost.

Their study found that invasive E. adenophorum adopted a quicker-return energy-use strategy, i.e. higher photosynthetic energy-use efficiency and shorter payback time compared with native E. stoechadosmum. There were strong synergistic effects for elevated CO₂ and N deposition, which exerted greater enhancement of growth for the invader relative to the native congener. Reducing N availability by applying sugar eliminated the advantages of the invader at both CO₂ levels.

Their results indicated that CO₂ enrichment and N deposition may exacerbate E. adenophorum's invasion success in the future and that manipulating soil N availability may be a feasible tool for managing its invasion impacts.

The study entitled “Synergistic interactions of CO₂enrichment and nitrogen deposition promote growth and ecophysiological advantages of invadingEupatorium adenophorumin Southwest China” has been published online in Planta, 236 (4):1205-1213, DOI: 10.1007/s00425-012-1678-y