ARE ECOPHYSIOLOGICAL RESPONSES INFLUENCED BY CROWN POSITION IN CORK-OAK

Montados and dehesas of Quercus ilex and Quercus suber occupy large ar eas in the Iberian Peninsula and are characterized by a low-density tr ee cover. The variability of responses within tree canopies in such op en stands has been little studied. We investigated the variation of st omatal conductance within the crown of a cork-oak (Q suber L), by stud ying its diurnal and seasonal courses at two different heights and fou r directions within the canopy. Height did not strongly affect leaf re sponse, as a consequence of the crown structure. Differences were foun d in microclimatic conditions and maximum stomatal conductance among d irections. However, overall daily stomatal conductance was similar amo ng different crown sections, suggesting that leaves develop different mechanisms to accomodate the microclimatic constraints which affect th e particular position they occupy in the crown of cork-oak.