Physiological and morphological leaf trait variations in two Apennine plant species in response to different altitudes

Morphological and physiological traits of Crepis pygmaea L. subsp. pygmaea and Isatis apennina Ten. ex Grande growing at different altitudes in the Gran Sasso Massif (Abruzzo, Italy) were analyzed. The two populations of C. pygmaea and I. apennina growing at the highest altitude (C (p2) and I (p2) at 2,310 m a.s.l. and 2,350 m a.s.l., respectively) had a lower leaf mass area (LMA) than the two populations growing at the lowest altitude (C (p1) and I (p1) at 2,250 m a.s.l. and 2,310 m a.s.l., respectively). Leaf tissue density (LTD) had the same LMA trend, decreasing 23 and 10% in C. pygmaea and I. apennina, respectively, from the highest to the lowest altitude. C. pygmaea and I. apennina had the highest photosynthetic rates (P (N)) in July decreasing on an average 17 and 30%, respectively, in August and 50 and 38%, respectively, in September. Leaf respiration (R) in I (p1) and I (p2) had the same trend as C (p1) and C (p2), showing the highest rates in September. Global warming could drive C. pygmaea and I. apennina toward higher altitudes in the Gran Sasso Massif. Nevertheless, C. pygmaea with the higher plasticity index (PI) both at physiological and at morphological levels (0.50 and 0.35, respectively) might have a competitive advantage over I. apennina over the long term.