Climate change is most pronounced in high-elevation habitats than elsewhere, potentially causing important disruptions in plant community composition and dynamics through changes in plant interactions. We tested the effect of warming and rainfall manipulations on growth and physiological status of Arenaria tetraquetta, a cushion plant species in the Sierra Nevada Mountains in Spain, and assessed the consequences of experimental manipulations on its facilitation effects. We increased temperature using acrylic open-top chambers (OTC) and increased or decreased runoff water, expecting that warming would increase physiological rates, leading to greater growth in plants with OTCs. We expected that temperature and rainfall manipulations would change cushion growth patterns and the relationships with beneficiary species, as larger growth would decrease cushion compactness, weakening facilitation effects measured in terms of species and individuals inside the A. tetraquetta canopy.
Results/Conclusions
Our rainfall treatments did not have significant effects, but warming increased daylight temperature, enhancing photosynthetic rate and respiration. Warming increased canopy growth and led to larger leaves although it did not change other plant traits nor the facilitation effects of cushions. We conclude that global warming may change the physiology of alpine plants, offsetting allocation patterns. It is unlikely, however, that warming will significantly affect interaction intensity between facilitator and beneficiary species, as expected temperature changes may not be enough to alter in substantial ways the status quo of current interactions.