Changes in leaf nutrients of healthy and withered trees in the forests of Garan (in Marivan) and Dezlei (in Sarvabad) in Kurdistan province

Most macronutrient accumulation occurs in tree leaves and there is a strong relationship between leaf nutrient change and tree decline. The aim of this study was to investigate the changes in leaf nutrients in healthy and withered trees in the forests of Marivan and Sarvabad county in Kurdistan province. For this purpose, Garan (Marivan) with declining trees were selected as unhealthy site, while Dezli (Sarvabad) was determined as a control site containing heathy trees. In both sites, trees were selected on the northern and southern slopes, where five healthy trees and five withered trees (totally, 30 trees including 10 trees in control and 20 trees in declining stands) were selected and numbered. 20 leaves were harvested from the four sides of a tree crown in the first week of August 2019 and 2020. The concentrations of nitrogen (N), phosphorus (P) and potassium (K) were measured using digestion method. Due to the normality of the data, one-way analysis of variance, Duncan and paired t-test were used to analyze these data. The results showed that the amount of N in the decline site was higher than that in the control site. In contrast, leaf P and K contents in tress of control was significantly higher that decline stands. and potassium elements, the amount of these elements in the control mass was higher than the decaying mass and had drought. The highest reduction of N and P were observed in withered trees in the northern and southern slopes and one-way analysis of variance test confirmed the significance of the difference between K (2019) and P (2020) in the six groups of studied trees. On the other hand, changes in leaf nutrients between 2019 and 2020 demonstrated a decreasing trend for N and P and an increasing trend for K, where the paired t-test confirmed the significant change in nutrients of tree leaves in two consecutive years. To improve P and K in decline trees, foliar application of these macronutrients could be suggested in a short-time period, and in the long run, susceptible ecosystems should be rehabilitated by reforestation with rainwater catchment system and protection systems.