Ecology of Iranian Forest

  Specific leaf area ( the ratio of leaf area to dry mass) is one of the most important ecological variables can be viewed as the tradeoff between ecosystem mass balance and ecosystem energy balance. This variable is further particularly sensitive to changes in the external environment and in the internal functioning of the plant. In this research, we studied the effect of species and leaf position in the crown on SLA. Five sample trees of three oak species (Quercus brantii, Q. infectoria and Q. libani) were selected in Zagros collection of National Botanical Garden of Iran. For each of the species selected, 30 youngest fully expanded leaf (young leaf) as well as the oldest green and viable leaf (old leaf) were selected. Furthermore, 30 sun leaves and 30 shade leaves were selected from the half upper parts and half lower part of the crowns, respectively. The leaves were weighted (wet weight) and their areas were measured by leaf area meter in laboratory. The leaf samples were then dried at 70°C for 48h and weighted again (dry weight). The SLA of all kinds of sample leaves had significant differences among oak species. There only were significant differences between the SLA of the young and old leaves in Q. infectoria. Furthermore, the SLA of the sun and shade leaves showed significance differences in all studied species, so that the sun leaves had lower SLA than the shade leaves. This research proved the effect of environmental and inherent function of oak species on SLA.