Variation in the nutrient contents of leaves, bark, and wood of Persian oak trees (Quercus brantii) affected by decline

Tree decline is a physiological phenomenon resulting from climatic disturbances that involves damage to forest ecosystems. This study examined the effects of tree decline on nutrient concentrations in the leaves, bark, and wood of Persian oak (Quercus brantii) trees. Trees were categorized by decline severity (healthy, slight, moderate, and severe decline). Leaves were collected from the middle and outer parts of the crowns. Bark and wood samples were taken at breast height (1.3 m). The contents of Mg, Ca, P, Fe, K, and Na were analyzed by atomic absorption spectrophotometry and flame photometry. As decline severity increased, the concentrations of Mg, Ca, P, Fe, K, and Na in the foliage increased. However, the P and K in the bark and the P in the wood were lower in trees in the higher decline classes. Moreover, nutrient contents in the tissues examined varied across the different decline severities. The variations may have been due to defense mechanisms of the trees enhancing tolerance against induced stress. The results suggested that nutrient stoichiometry can reflect uptake in forest ecosystems and plant-environmental stress relationships.