نوع مقاله : مقاله کامل علمی پژوهشی
نویسندگان
1 دانش‌آموخته کارشناسی‌ارشد، گروه جنگل‌شناسی و اکولوژی جنگل، دانشگاه علوم کشاورزی و منابع طبیعی گرگان، گرگان، ایران.
2 دانشیار، گروه جنگل‌شناسی و اکولوژی جنگل، دانشگاه علوم کشاورزی و منابع طبیعی گرگان، گرگان، ایران.
3 استاد ، گروه جنگل‌شناسی و اکولوژی جنگل، دانشگاه علوم کشاورزی و منابع طبیعی گرگان، گرگان، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and objectives: Earthworms, as one of the most prominent biological groups in soil, play a crucial role in enhancing its physical, chemical, and biological properties, thereby influencing subterranean biomass and biogeochemical cycles. By modifying soil porosity and decomposing organic matter, they contribute significantly to improving ecosystem functionality. Their abundance is influenced by environmental factors such as moisture and litter quality. In forested areas, differences between natural and planted stands, particularly in forest plains like Shast-Kalateh, have a notable impact on earthworm populations. Moreover, seasonal variations in climate and soil characteristics can significantly affect the distribution patterns and biomass of these organisms. This study aimed to examine the effects of natural and planted forest stands on earthworm density and biomass across different seasons in six forest stands within the Shast-Kalateh forestry plan.
Materials and methods: In this study, two natural forest stands, specifically the Productive and Low-yielding Persian Ironwood-Hornbeam, were selected alongside four reforested stands—Arizona cypress, Caucasian alder, Chestnut-leaved oak, and a mixed Chestnut-leaved oak-Caucasian elm forest—in district one. The selection ensured similarity in topographic conditions such as slope, aspect, and altitude above sea level across all stands. Monthly, 30 soil samples were collected from each forest type using a cylinder with a cross-section of 81 cm² and a depth of 30 cm. Earthworms were manually sorted from these samples, subsequently oven-dried at 60°C, and weighed with a precision of 0.001 grams. Simultaneously, surface soil samples (0 to 10 cm depth) were obtained to assess various physical and chemical characteristics, including moisture content, bulk density, acidity, nitrogen levels, and organic carbon content, as well as phosphorus and potassium concentrations.
Results: The results revealed a notable disparity in both the average number (1.46) and biomass (0.2) of earthworms between natural forest stands and artificially planted areas. Across all seasons, the average biomass of earthworms exhibited a decrease in the following order: spring (0.26), winter (0.14), Autumn (0.13) and summer (0.05). Intriguingly, the winter season emerged as particularly conducive to earthworm activity in the plains of Shastakalate forest. Notably, the highest number (1.7) and biomass (0.81) of earthworms were consistently observed in the artificial planting Oak stand in the depth of 0-10 cm. This underscores its success in creating optimal soil conditions for earthworms. The findings highlight the seasonal dynamics and depth preferences of earthworms in response to varying environmental conditions. Furthermore, the population of earthworms in the studied area exhibited a strong correlation with specific soil characteristics, with acidity, moisture levels, and the carbon-nitrogen ratio identified as the most influential factors. These results contribute valuable insights into the intricate interplay between earthworm dynamics and key soil attributes, emphasizing the importance of considering both natural and artificial environments in silvicultural practices
Conclusion: According to the findings of this study, the density and biomass of earthworms were higher in natural forest stands compared to planted stands, indicating more favorable living conditions in the former. Among the planted stands, however, the Chestnut-leaved oak stand demonstrated the highest earthworm density and biomass at a soil depth of 0–10 cm, making it the most successful in creating optimal soil conditions for earthworm activity. Seasonal changes also significantly influenced earthworm biomass, with winter in the Shast-Kalateh forest plain identified as a particularly favorable period for their activity. These findings underscore the importance of soil and forest stand management in enhancing ecosystem health.
کلیدواژه‌ها [English]
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