بررسی عوامل موثر بر پراکنش و تولید میوه گلابی وحشی (Pyrus syriaca Boiss) در استان آذربایجان غربی

Background and objectives: Non-wood forest products constitute an integral component of forest ecosystems and are closely associated with the socioeconomic conditions of forest-dependent communities. In the Zagros region, these products have long contributed to household income and subsistence. Wild pear (Pyrus syriaca Boiss), as a native species, holds high economic, nutritional, and medicinal value. The present study examines the key ecological determinants governing the distribution and fruit yield of wild pear, with the aim of identifying suitable habitats for its establishment and expansion in degraded or sparsely forested landscapes. Owing to the limited number of studies conducted on this species, this research provides valuable insights for habitat suitability assessment and sustainable resource management.
 
Methodology: To study the wild pear (Pyrus syriaca Boiss.), five natural habitats were selected in Marmisho, Darreh-Khan, Perdanan, Mirabad, and Aslanik, located in West Azerbaijan Province, Iran. Within each selected habitat, forest stands of 2 hectares were delineated and subjected to a full inventory.  Climatic data, including mean annual precipitation, mean annual temperature, and maximum temperature of the warmest month, were obtained from the nearest meteorological stations. Quantitative tree characteristics such as diameter at breast height (DBH), total height, crown cover area, number of sprouts, tree origin, health status, and crown symmetry were recorded through 100% enumeration within each 2-hectare plot. For soil analysis, three composite soil samples (collected from the beginning, middle, and end of each stand) were taken from a depth of 0–30 cm and transferred to the soil laboratory for analysis. Soil texture was determined using the Bouyoucos hydrometer method; soil pH was measured potentiometrically; organic carbon content was determined using the Walkley–Black method; total nitrogen by the Kjeldahl method; and available potassium by ammonium acetate extraction followed by flame photometry. Fruit production was estimated by randomly selecting 20 individual wild pear trees along transects within each habitat. Subsequently, one tree was designated as a sampling unit for fruit yield estimation for every three selected trees. The total number of fruits per sampled tree was determined through visual enumeration, while mean fruit weight was calculated by weighing 30 randomly collected fruits. Fruit yield per tree was then estimated based on the product of fruit number and mean fruit weight. In each stand, 20 wild pear trees were randomly selected to estimate fruit yield. The number of fruits per tree was visually counted, and the average fruit weight was determined from 30 randomly sampled fruits. Based on these measurements, the total fruit production per tree was calculated. To analyze the relationship between DBH, total height, and crown cover, regression analysis was applied. Differences in quantitative traits and fruit yield across sites were assessed using the non-parametric Kruskal–Wallis test. In addition, principal component analysis (PCA) was employed to identify the most important soil factors influencing fruit production. For statistical analysis, data derived from the investigated stands and soil samples were compiled and analyzed using SPSS software. Prior to analysis, quantitative variables were examined for normality using the Kolmogorov–Smirnov test. Following confirmation of normality, one-way analysis of variance (ANOVA) was performed, and Duncan’s multiple range test was applied to compare and classify the mean values of the measured variables across the studied habitats. Regression analyses were conducted to assess the relationships among diameter at breast height (DBH), total tree height, and crown area. Qualitative variables were analyzed using the non-parametric Kruskal–Wallis test. Furthermore, principal component analysis (PCA) was employed to identify the most influential soil-related factors affecting fruit production.
Results: Among the studied sites, the highest mean diameter at breast height (DBH) was recorded in Mirabad (21.8 cm), while the lowest value was observed in Pardanan (10.78 cm). The maximum DBH was measured in Mirabad (45 cm) and the minimum in Aslanik (5.7 cm). In terms of tree height, the highest mean was obtained in Mirabad (22.6 m), whereas the lowest was found in Aslanik (3.49 m). The tallest tree was recorded in Darreh-Khan (14.6 m), and the shortest in Aslanik and Marmisho (1.7 m). Regarding crown cover, Mirabad exhibited the highest mean value (76.5 m²) and Aslanik the lowest (3.77 m²). The maximum crown cover was recorded in both Darre-Khan and Mirabad (31 m²), while the minimum was found in Darreh-Khan (0.07 m²) (Table 2). Overall, the results indicated that there were significant differences among the sites in DBH, total height, and mean crown diameter. The average fruit yield per tree was calculated as 86.4 kg in Mirabad, 63.5 kg in Darre-Khan, 46.7 kg in Pardanan, 51.7 kg in Marmisho, and 9.33 kg in Aslanik. The highest fruit production was obtained in Mirabad, whereas the lowest yield was recorded in Aslanik.
Conclusion: Based on the results obtained from the five studied regions, wild pear trees exhibited a high level of adaptability to a wide range of physiographic conditions, including elevation and slope. The species was distributed across slopes ranging from 0 to 45% and elevations between 1,300 and 1,760 m above sea level, occurring under various aspects, including northern, southern, and eastern exposures. In terms of soil conditions, wild pear demonstrated good adaptability to sites with diverse soil physicochemical properties. In areas with higher potassium content (Dareh-Khan and Marmisho regions), superior performance was observed in terms of fruit size and mean fruit yield per tree. With respect to climatic adaptability, this species was well adapted to semi-humid to humid climatic conditions. Furthermore, the evaluated growth characteristics, including diameter at breast height (DBH), tree height, crown area, and sprout grouping, indicated favorable growth conditions across the studied regions.