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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 energy to defence. However, it remains unclear how global change and nutrient enrichment will influence the competition between invasive species and co-occurring native species. Here, we tested whether nitrogen (N) and phosphorus (P) addition under elevated CO2 causes 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 (by 29.0%), whereas it increased the growth-related compounds in the leaf, including proteins (by 75.7%), minerals (by 9.6%) and total non-structural carbohydrates (by 8.5%). The increased concentrations of growth-related compounds were possibly associated with the increase in ribulose 1,5-bisphosphate carboxylase oxygenase content and mineral nutrition (magnesium, iron and calcium), all of which were higher in the invasive species than in the 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 suggests that invasive species respond more readily to produce growth-related compounds under an increased soil nutrient availability and elevated CO2., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permission@oup.com.)

Invasive plants rapidly spread in habitats with low soil phosphorus (P) availability and have triggered a sharp decline in the diversity of native species. However, no studies have explored how widespread invasive species acclimate to low soil P availability via changing foliar P fractions, especially under elevated atmospheric CO 2 concentrations ([CO 2 ]) and nitrogen (N) deposition. Here, an open-top chamber experiment was conducted to explore the effect of nutrient addition and elevated [CO 2 ] on leaf traits and foliar functional P fractions (i.e., Pi, metabolite P, lipid P, nucleic acid P, and residual P) of two aggressive invasive species (Mikania micranatha and Chromolaena odorata). We found that foliar N/P ratios were more than 20, and P addition significantly increased plant biomass. Both results indicated P-limited plant growth at our studied site. Elevated [CO 2 ], N and N + P addition greatly increased plant biomass, photosynthetic rates, and photosynthetic P-use efficiency (PPUE) in invasive species, but PPUE decreased with increasing P addition. Nitrogen addition slightly decreased the concentration of leaf total P, decreased foliar residual P, but increased metabolite P concentrations in invasive species. Similar changes in foliar P fractions were found under N + P addition. Phosphorus addition increased foliar P concentrations, which was strongly correlated with an increase in metabolite P concentrations in invasive species. Elevated [CO 2 ] alleviated these effects and increased PPUE. The present results suggest that future elevated [CO 2 ] and N deposition allow the invasive species to acclimate to low soil P availability and support their successful invasion by greatly reducing P allocation to non-metabolite foliar P fractions (i.e., nucleic acid P and residual P) to meet their demand of metabolite P for photosynthesis and exhibit a high PPUE., (© 2021 Scandinavian Plant Physiology Society.)

Rising atmospheric CO 2 concentration and nitrogen (N) deposition are changing terrestrial carbon (C) cycle; however, little has been known about such impacts in a heavy-metal-contaminated environment. This study conducted an open-top chamber experiment to explore the impacts of rising atmospheric CO 2 concentration and N deposition on the leaf litter and soil C cycle in cadmium (Cd)-contaminated environment. The experiment include five treatments: control, Cd (30 g ha -1  yr -1 ) addition, Cd addition under elevated CO 2 (700 ppm CO 2 ), Cd and N(100 kg ha -1  yr -1 ) additions, and Cd and N additions under elevated CO 2 , with three replicates per treatment. Leaf litter and soil C cycle were indexed by microbial biomass C concentration and the activities of four key C-degrading enzyme (β-glucosidase (BG), cellobiohydrolase (CBH), polyphenol oxidase (PPO), and peroxidase (POD)) in litter and soil. Results showed that, after one year treatment, Cd addition negatively affected the activities of all four C-degrading enzyme in litter and soil; while elevated CO 2 and N addition essentially alleviated these negative effects. Elevated CO 2 and N addition increased C-degrading enzyme activities more of the non-legume (i.e., Cinnamomum camphora) litter than those of the legume (i.e., Acacia auriculiformis) litter. Elevated CO 2 , N addition, and Cd addition all affected C-degrading enzyme activities via their effects on the microbial biomass C concentration and C and N availability of the litter and soil samples. We suggest that rising atmospheric CO 2 concentration and N deposition can offset the detrimental effect of Cd on the litter and soil C-degrading enzyme activities in forest ecosystems., (Published by Elsevier B.V.)