Document Type : Research article
Authors
1
Associate Prof., Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran
2
Prof., Research Division of Forest, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran
3
Researcher, Research Division of Forest, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran
4
Ph.D, of Forestry, Faculty of Agriculture and Natural Resources, Urmia University, Urmia, Iran
5
Assitant Prof., Research Division of Forests, Rangelands and Watershed Management, Kohgiluyeh and Boyerahmad Agricultural and Natural Resources Research and Education Center
Abstract
Background and Objectives: Brant`s oak (Quercus brantii Lindl.), the dominant tree species in Zagros forests, has experienced decline of varying intensity. Investigating nutrient concentrations in tree leaves helps study physiological responses to environmental stresses. This research examines changes in leaf nutrients of healthy and unhealthy oak trees in Kohgiluyeh and Boyer-Ahmad forests over two consecutive years (2020-2021), amid increasing oak decline in Iran's South Zagros forests.
Methodology: Trees were selected from two 1-ha sites: Sarabtaveh (control) and Sisakht (declined area). In the declined plot, five healthy and five unhealthy trees were chosen; in the control plot, five healthy trees were selected. Leaf samples were collected at the end of the growing season in 2020 and 2021 from the middle crown across four geographic directions (five leaves per direction), yielding 20 leaves as a composite sample per tree. Essential elements and micronutrients were extracted via digestion and measured using atomic absorption. Treatments were compared using two-way ANOVA and Duncan's mean separation test in R software.
Results: Nitrogen (1-1.6%), potassium (0.2-1%), and phosphorus (0.1-0.2%) concentrations varied across plots. Sampling year significantly affected most elements except magnesium. Nitrogen decreased in the second year across all stands, significantly so in unhealthy trees of the declined area. Phosphorus showed interannual fluctuations but no significant differences. Potassium increased slightly in year two but showed no significant differences. Iron, zinc, and manganese were significantly higher in 2021 than 2020 across stands. Nitrogen, phosphorus, and potassium were higher in the declined area than the control during both years. Manganese, copper, and zinc were highest in control healthy trees, intermediate in declined unhealthy trees, and lowest in declined healthy trees.
Conclusion: Significant changes in most leaf elements between declining and healthy trees indicate that oak decline, characterized by reduced nitrogen and phosphorus and increased potassium, iron, zinc, and manganese, affects nutrient absorption. Leaf nutrient measurements reflect absorption dynamics and plant-environment stress relationships in forest ecosystems. Observed changes likely stem from trees' defense mechanisms enhancing stress tolerance. Better understanding of decline effects on tree nutrition can inform strategies to minimize oak decline damage.
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