The impact of light quality and leaf wetness on photosynthesis in north-west Andean tropical montane cloud forest

Abstract

Photosynthesis was limited by low-intensity photosynthetically active radiation (PAR) and leaf wetness in a lower montane cloud forest (LMCF) of Cauca, Colombia. Mean PAR intensity remained below the saturation level for leaf-scale net photosynthesis (P n ) throughout the solar day during the wet season and for most of the solar day during the dry season. PAR represented a smaller fraction of total solar radiation (K↓) in LMCF than in lowland rain forest (LRF). In LMCF trees and shrubs, mean PAR-saturated P n ranged from 4.3–10.6 μmol C m −2 s −1 at 1450 m, and from 3.5–10.2 μmol C m −2 s −1 at 2150 m. P n was reduced by abaxial wetness in leaves of some trees and shrubs, and eliminated in others. This study indicates that persistent cloudiness and interception of cloud water by leaves limit LMCF productivity.