نوع مقاله : علمی - پژوهشی
نویسندگان
1 دانشجوی دکتری علوم زیستی جنگل، دانشکده منابع طبیعی، دانشگاه لرستان، خرمآباد، ایران
2 استاد، گروه جنگلداری، دانشکده منابع طبیعی دانشگاه لرستان، خرمآباد، ایران
3 دانشیار، گروه زیستشناسی، دانشکده علوم پایه دانشگاه لرستان، خرمآباد، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and Objective: Persian oak (Quercus brantii Lindl.), the flagship species of the Zagros forests, is facing a severe threat due to the phenomenon of oak decline. As a complex and multi-factorial process, decline leads to a progressive deterioration in tree health by disrupting water and nutrient uptake. This phenomenon is characterized by symptoms such as crown yellowing (chlorosis), branch dieback, and the emergence of epicormic shoots. Since decline influences nutrient dynamics within both soil and plant tissues, investigating nutrient resorption (specifically nitrogen, phosphorus, and potassium) between leaves and twigs in healthy versus declining trees serves as a key indicator for assessing tree vitality. Previous research has demonstrated that nutrient concentrations in healthy trees are significantly higher than in those affected by decline, a phenomenon that also directly impacts soil microbial communities and biogeochemical cycles. This study aimed to evaluate the impact of decline on nutrient resorption in Persian oak and its relationship with soil nutrient availability in the Chenar Begali region of Lorestan Province. The primary hypotheses included a direct link between nutrient resorption in plant tissues and soil properties, the correlation between nutrient concentrations and soil availability, and the significant impact of decline on resorption processes. The findings of this study can contribute significantly to understanding the mechanisms of decline and developing effective conservation strategies.
Material and Methods: The study area is located in Shorab Chenar Begali within the Dadabad forests of Lorestan Province (33° 20' 32" N, 48° 15' 40" E), covering an area of 60 hectares. According to the De Martonne aridity index, the region is characterized by a highly humid climate with significant microclimatic diversity, where different slope aspects exhibit distinct weather conditions. The soils are predominantly loamy-clay, derived from limestone parent materials. The average annual precipitation is 510 mm, with temperatures ranging from -14.60°C to 47.00°C. In this study, sampling was conducted on healthy and declining coppice-origin Persian oak trees across four dieback classes (healthy, low, moderate, and severe dieback). Sampling was performed using 10 rectangular plots (0.1 hectares each) through a selective random method. In each plot, four trees with homogeneous quantitative characteristics (diameter, height, and canopy cover) were selected. Leaf and twig samples were collected from four crown directions during two periods (April and December 2023). After oven-drying the samples at 65°C for 72 hours and grinding them into a fine powder, the concentrations of nitrogen, phosphorus, and potassium were measured at the laboratory of the Department of Forestry, Faculty of Natural Resources, Lorestan University. Data were analyzed using a two-way analysis of variance (ANOVA) at a 1% probability level, and mean comparisons were performed using Duncan's Multiple Range Test.
Results: The results of the two-way analysis of variance (ANOVA) revealed that the main effects of decline, plant tissue, and their interaction on nitrogen (N), phosphorus (P), and potassium (K) concentrations were significant at the 1% probability level during both the initial and final stages of the growing season. Tree decline significantly reduced the concentration of these elements in both leaves and twigs; the most substantial reduction in N was observed in twigs with over 50% dieback, while the greatest decrease in P occurred in leaves under similar dieback conditions. Furthermore, while K concentrations were significantly higher in twigs than in leaves, decline caused a 1.32 to 3.61-fold reduction in this parameter within damaged tissues. Nutrient resorption of N, P, and K decreased as the severity of decline increased, with higher concentrations recorded in twigs compared to leaves. Significant positive correlations were identified between leaf N resorption and soil pH, organic carbon, and soil N at the beginning of the growing season, whereas only the correlation with soil N persisted by the end of the period. Regression models further confirmed the influence of soil variables on nutrient resorption. These findings indicate that decline not only reduces nutrient concentrations but also impairs resorption efficiency, which could have critical implications for plant nutrition management under stress conditions.
Conclusion: This study demonstrates that decline leads to a marked reduction in nutrient concentrations within leaf and twig tissues, with concentrations dropping sharply as dieback severity intensifies. Decline also significantly impacted the net nutrient resorption of N, P, and K, causing a substantial decrease in resorption efficiency as the trees deteriorated. Varying climatic conditions, soil moisture deficits, and the translocation of nutrients from twigs to leaves are among the primary factors driving these changes.
کلیدواژهها [English]
)