Nitrogen and phosphorus addition promote invasion success of invasive species via increased growth and nutrient accumulation under elevated CO2

Abstract

In the context of the resource allocation hypothesis regarding the trade-off between growth and defence, compared with native species, invasive species generally allocate more energy to growth and less to defence. However, it remains unclear how global change and nutrient enrichment will influence competition between invasive species and co-occurring native species. Here, we tested whether: nitrogen (N) and phosphorus (P) addition under elevated CO2 cause invasive species (Mikania micrantha and Chromolaena odorata) to produce greater biomass, higher growth-related compounds, and lower defence-related compounds than native plants (Paederia scandens and Eupatorium chinense). We grew these native and invasive species with similar morphology with the addition of N and P under elevated CO2 in open-top chambers. The addition of N alone increased the relative growth rate (RGR) by 5.4% in invasive species, and its combination with P addition or elevated CO2 significantly increased the RGR of invasive species by 7.5% or 8.1%, respectively, and to a level higher than that of native species (by 14.4%, P < 0.01). Combined N + P addition under elevated CO2 decreased the amount of defence-related compounds in the leaf, including lipids (by 17.7%) and total structural carbohydrates (TSC, by 29.0%), whereas increased growth-related compounds in the leaf, including proteins (by 75.7%), minerals (by 9.6%), and total non-structural cabohydrates (TNC, by 8.5%). The increased concentrations of growth-related compounds were possibly associated with the increase in Rubisco content and mineral nutrition (magnesium, iron, and calcium), all of which were higher in invasive species than in native species. These results suggest that rising atmospheric CO2 concentration and N deposition combined with nutrient enrichment will increase the growth of invasive species more than that of native species. Our result also suggest that invasive species respond more readily to produce growth-related compounds under increased soil nutrient availability and elevated CO2.