Plasticity of leaf morphological traits impacted by livestock grazing on trees in Zagros semi-arid forest

The Zagros forest in West Iran is one of the most important livestock centers for animal husbandry. Overgrazing has depleted forest biodiversity, regeneration, and forest structure. We aimed to investigate the plasticity of the leaf traits under grazed and ungrazed treatments in semi-arid areas, Ilam. Therefore, three forest stands and three species as Amygdalus orientalis, Cerasus incana, and Acer monspessulanum were selected. The statistical analyses showed that leaf right vein (RV), leaf width (LW), blade length (BL), specific gravity (SG), wet weight of leaf (WWL), dry weight of leaf (DWL), and leaf internode length (LIN) (P < 0.05) significantly differed among two treatments. Furthermore, significant differences were determined in tree species as well as the interaction between trees × treatments in the measured traits. The Principle Components Analysis (PCA) presented a significant positive correlation among RV, LW, BL, WWL, DWL, and LIN. Consequently, the traits of grazed leaves were well separated from ungrazed. The traits in grazed leaves of C. incana, and A. monspessulanum were differentiated from another tree, so showing more similarities related to the measured traits. There was a negative correlation between leaf SG and other traits in ungrazed treatment. This was predictable due to correlation between SG and the leaf area in grazed trees. It was concluded that all leaf traits were impacted by the grazing and that in the long term this could influence the forest structure and survival. The results will help to better management of the forests and preservation of high-value trees.