Elevated CO2, temperature and nitrogen levels impact growth and development of invasive weeds in the Mediterranean region.
BACKGROUND: Invasive plant species present a serious threat to the environment, as well as human and animal health. An interaction may exist between the climatic changes and invasive plant species. In this 2-year study, we investigated the effects of warming, CO2 and nitrogen application on the biomass, growth and leaf tissue nitrogen concentration of three invasive weed species. Treatments were: (i) simulated (elevated) CO2 (approximately 800-900 ppm); (ii) warming or high temperature (day/night 25/15°C); (iii) simulated (elevated) CO2 combined with high temperature (CO2 = approximately 800-900 ppm; temperature day/night 25/15°C); and (iv) control conditions (CO2 = approximately 400-450 ppm; temperature day/night 20/10°C). The doses of nitrogen were: (i) 0 kg ha-1 (control; low); (ii) 60 kg ha-1 (medium); and (iii) 120 kg ha-1 (high). RESULTS: Elevated CO2 and elevated CO2 combined with high temperature improved biomass and the growth of the tested invasive weed species: Lactuca serriola L., Hordeum murinum L. and Bromus tectorum L. Nitrogen application had little effect on grasses, whereas the broadleaved weed mostly had a positive response to nitrogen application. Invasive weed species were generally negatively or neutrally affected by warming. CONCLUSION: The results of the present study demonstrate that nitrogen fertilization under different climatic conditions improved few of the parameters, whereas elevated CO2 promoted most of the growth parameters of invasive weeds. Overall, is it concluded that these weeds will be more invasive under climate change conditions.