LEAF AREA AND PHOTOSYNTHETIC EFFICIENCY OF DOMINANT WOODY SPECIES IN MOUNTAINOUS SEMI-ARID AREAS OF ETHIOPIA

Abstract

Examining physiological response of trees and shrubs to ecological variables is necessary to choose species for fast rehabilitation via enrichment planting. However, the ecophysiological study on woody plants in the rehabilitating ecosystems is scanty. This study was, therefore, designed to evaluate the photosynthetic efficiency and leaf area response of five dominantly growing plant species: Acacia seyal delile, Acacia lahai Steud. & Hochst. exBenth, Olea europaea ssp. Cuspidata L., Dodonaea angustifolia L.f. and Becium grandiflorum (Lam.) Pic.ser in Maineteba exclosure at three altitudinal ranges at Maineteba exclosure, Tigrai. Diurnal photochemical efficiency of PSII (Fv/Fm) of each species was measured from leaves of actively growing branches. A Systematic sampling method was applied to collect leaf area. Our results showed that photosynthetic efficiency ranged from 0.73 in the species A. lahai and D. angustifolia to 0.801 in O. europaea ssp. Cuspidata indicating they were under tolerable stress. The leaf area of the experimental plants was significantly different (P=0.001), perhaps due to either genetic or altitudinal variations (P=0.001). The interaction of altitudinal and species variations was significantly different (P=0.004). Leaf area of O. europaea ssp. Cuspidata significantly decreased (P=0.001) with increasing altitude maintaining optimal Fv/Fm in both upper and lower altitudinal ranges. However, others’ leaf area relaxed in the middle altitude indicating they were more stressed by higher evapotranspiration in the lower altitude than solar radiation did. Based on the morpho-physiological parameters considered, O. europaea ssp. Cuspidata and A. seyal were the best performing woody species and can be recommended for enrichment planting in the rehabilitating drylands.