Abstract: Aims Relatively few studies so far have assessed how ongoing global warming will affect the photosynthetic performance of dryland plant species. We evaluated the effects of warming on the photosynthetic rates of 10 species with contrasting functional attributes, and whether their functional traits modulated photosynthetic responses to warming.
Methods A common garden experiment was conducted over 2 years with distinct environmental conditions (drier vs. wetter year). The experiment was designed as a randomized block design with two treatments: warming (control vs. ~2.9°C temperature increase) and species (Agropyron cristatum, Festuca ovina, Lygeum spartum, Medicago sativa, Plantago lanceolata, Psoralea bituminosa, Sanguisorba minor, Hedysarum coronarium, Dorycnium pentaphyllum and Phlomis herba-venti). We linked functional traits measurements with temporal variations in photosynthetic responses to warming.
Important findings In the drier year, warming increased photosynthetic rates at the beginning of the growing season, suggesting a modification in the growing period (earlier spring). In the wetter year, functional traits modulated photosynthetic responses to warming. Larger species with shorter leaves (e.g. M. sativa) had higher photosynthetic rates under warming compared to smaller species with larger leaves (e.g. F. ovina). Our results highlight the importance of (i) studying photosynthetic responses along different years and (ii) considering functional traits when evaluating photosynthetic responses to climate change, particularly in stressful environments such as drylands.

Key words: photosynthesis, climate change, Mediterranean, functional traits, open top chambers