Warming and nitrogen deposition have contrasting effect on the invasive Taraxacum officinale in the high-alpine of central Chile

Global warming and the increase in nitrogen depositions are part of the global changes induced during the last centuries on the planet by human activities. High-elevation environments have been suggested as one of the most sensitive habitats to the effects of these global changes and that any climatic modification that ameliorates the prevailing stressful conditions that characterize alpine habitats should increase the ecophysiological performance of plant species inhabiting this habitat. Thus, we hypothesized that increases in the environmental temperature and nitrogen deposition should have positive effects on the photosynthetic efficiency and some fitness components of a plant species growing at very high elevations. During two growing seasons we assessed the effect of warming and soil nitrogen addition on the ecophysiological performance of Taraxacum officinale at 3600 m in the Andes of central Chile. Individuals were exposed to 4 treatments: (1) warming, (2) nitrogen addition, (3) warming + nitrogen addition, and (4) control. For individuals growing on each treatment we registered the fluorescence of chlorophyll a (Fv/ Fm, ΦPS II, ETR, qP and NPQ) as well as the number of flowers and leaves produced by each experimental individual. While warming decreased the photosynthetic efficiency of T. officinale, nitrogen addition increased it. Both, photosynthetic performance and flowers and leaves production of individuals with warming plus nitrogen addition did not differ from control plants. Our results suggest that responses to different components of global change are more complex than expected and may act in opposite directions.  
FONDECYT 1060710 and P05-002-F ICM.