نوع مقاله : مقاله کامل علمی پژوهشی
نویسندگان
1 دانشگاه ایلام
2 دکتری علوم زیستی جنگل، محقق بخش تحقیقات جنگلها، مراتع و آبخیزداری، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان ایلام، سازمان
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Abstract
Background and objectives: Environmental gradients and landform changes, through gradual alterations in abiotic factors, influence the distribution and density of species and are important for the spatial distribution of plant species diversity. Topographic factors (elevation, slope, slope aspect) directly and indirectly affect the establishment, regeneration, and diversity of plant communities and are among the most important factors influencing biodiversity and ecosystem properties. The present study was conducted with the aim of comparing species and functional diversity indices in relation to physiographic factors in the Miantang forests of Sirwan, Ilam province.
Materials and methods: For this purpose, 40 sample plots measuring 30 × 30 meters were randomly established in the aforementioned forests across northern and southern aspects with two different canopy cover density levels. In addition, biodiversity indices including taxonomic diversity (Shannon–Wiener, Simpson, evenness, and species richness indices) and functional diversity (community-weighted mean for each trait, functional dispersion, and Rao’s quadratic entropy) were calculated. To measure functional diversity, in addition to species abundance, the functional traits of trees—including leaf nitrogen and phosphorus content, specific leaf area, leaf dry matter content, leaf carbon content, wood density, and tree height—were quantified. To assess the effects of topographic characteristics, variables such as elevation, aspect, and slope percentage were also calculated.
Results: The study revealed that functional diversity indices (functional dispersion, Rao's index) and community-weighted means of leaf phosphorus, nitrogen, carbon, wood density, and tree height were significantly influenced by slope aspect. Species evenness was highest in northern aspects. Rao's index, functional dispersion, and community-weighted mean of leaf phosphorus were greater in southern aspects and low-density stands. In contrast, community-weighted means of leaf nitrogen, carbon, wood density, and tree height were higher in northern aspects. PCA results based on functional traits indicated that southern sites (with both high and low densities) were characterized by higher specific leaf area and leaf phosphorus, while northern sites (with both densities) exhibited higher wood density, leaf carbon, and nitrogen. This pattern highlights the key role of slope aspect in separating communities based on functional traits.
Conclusion: Significant differences in functional diversity patterns between northern and southern slopes underscore the key role of slope aspect and stand density in shaping the structure of Zagros forest communities. Higher functional richness in southern slopes is likely due to greater solar radiation, while higher evenness in northern slopes may result from cooler and more humid conditions. Accordingly, slope aspect can serve as an efficient criterion for sustainable management and restoration planning in Zagros forests.
کلیدواژه‌ها [English]
)