The Effect of Different Levels of Decline on Leaf and Seed Morphological Characteristics of Quercus brantii Lindl. in the Zagros forests - Kermanshah Province

In recent years, one of the environmental problems of the Zagros forests is oak trees decay, which is manifested in the form of dryness of trees. Such issue is a multidimensional, complex and national phenomenon in the Zagros forests.

In current study, the impact of canopy severity of dryness on characteristics of leaves and seeds of Quercus brantii was monitored in deteriorated forest areas in Veyleh district of Kermanshah province during 2019-2021. Sampling of leaves for three consecutive years in spring and summer from five fixed trees in each decay class was randomly done. Each time20 leaves (5 leaves in each crown direction) were transferred to the laboratory to measure leaf area, fresh and dry weight of leaves and moisture percentage. Also, 25 seeds were separated from the same trees in each direction of the canopy and the dimensions of the seeds, seed cup and weight of 100 seeds were determined. The research treatments included tree decay at four levels (healthy, top canopy dryness, canopy dryness less than 50%, canopy dryness more than 50%). Combined analyses of quantitative data using SPSS statistical software in a completely randomized design was carried out and mean data were compared with Duncan's method at 5% level for four levels of drought and three years of study.

There is a significant difference (p≤%1) between different levels of dryness for dry weight, fresh weight, leaf moisture content and all characteristics related to seeds, but for the average leaf area, there is no significant difference between different levels of oak tree dryness. The interaction of different levels of dryness with study years was significantly different (p≤%1) for the following traits: length, average diameter, cup thickness and weight of 100 seeds. Also, a significant difference is observed in the diameter of the seed cup mouth diameter (p≤%5) finally, the interaction of the year in dryness levels for the traits cup height, cup diameter and percentage of seed viability is not significant. The maximum dry weight of leaves is related to the surface of more than 50% of dryness and the minimum is for healthy trees, which shows a significant difference (p≤%5) with other levels of dryness. The highest fresh leaf weight is related to less than 50% dryness and the lowest is related to healthy trees which has a significant difference (p≤%5) with other levels. The highest percentage of leaf moisture is related to healthy trees and the lowest amount is related to trees with more than 50% dryness which does not show a significant difference with canopy dryness trees. The highest dry leaf weight is related to the surface with more than 50% of dryness and the lowest amount is related to healthy trees and has a significant difference (p≤%5) with other levels.

It seems that the reproductive and vegetative characteristics of oak trees are totally impressed by different classes of tree dryness. Also, different climatic conditions during different years have a significant impact on such characteristics. The results showed that the health status of the trees has a great effect on leaf weight. Dried up Oak trees have larger and heavier leaves than healthy trees. With increasing drying rate, the quantity and quality of seeds have decreased drastically but for the characteristics of the leaves, the changes are such that the trees try to maintain their viability and to some extent maintain their photosynthetic level. In this area, reduced rainfall and the presence of drought effects from previous years is a serious threat to the vitality and health of the under study forest.