Leaf gas exchange and water relations in Polylepis tarapacana at extreme altitudes in the Bolivian Andes

摘要: Stress-induced restrictions to carbon balance, growth, and reproduction are the causes of tree-line formation at a global scale. We studied gas exchange water relations Polylepis tarapacana in field, considering possible effects stress limitations imposed on net photosynthetic rate (P N). Daily courses microclimatic variables, exchange, leaf potential were measured both dry-cold wet-warm seasons an altitude 4 300 m. Marked differences environmental conditions between resulted for mean potentials (−1.67 −1.02 MPa, respectively) conductances (33.5 58.9 mmol m−2 s−1, respectively), while P N (2.5 2.8 μmol not as evident. This may be related by deficit lower photon flux densities during dry wet seasons, respectively. Hence P. has coupled its characteristics extreme daily seasonal variations temperature availability high elevations.