نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه علوم و مهندسی جنگل، دانشکدة منابع طبیعی دانشگاه گیلان، صومعهسرا، ایران.
2 گروه جنگلداری، واحد خلخال، دانشگاه آزاد اسلامی، خلخال ایران.
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Introduction: Woody debris (coarse and fine woody debris) is a key component of forest ecosystems, playing an important role in carbon storage, nutrient cycling, and habitat provision. However, the effects of different forest management practices on the volume, decay dynamics, and carbon content of these stocks, particularly in the Hyrcanian forests of Iran, have rarely been investigated simultaneously and comparatively. This study aimed to assess and compare the volume, abundance, decay classes, biomass, and carbon content of fine woody debris (FWD: 2–10 cm diameter) and coarse woody debris (CWD: ≥10 cm diameter) in four stands with different management histories in the Nav Asalem forests of Gilan Province, northern Iran.
Method: Four forest stands were selected: (1) a shelterwood stand with 40 years since the last harvest, (2) a single-selection cutting stand with 10 years since the last harvest, (3) a single-selection cutting stand combined with salvage logging of windthrown trees, and (4) a conservation stand (no harvesting) as a control. Sampling was conducted using a systematic random grid of 100 × 100 m. Circular plots of 1000 m² were used for CWD, and concentric circular plots of 500 m² were used for FWD. For each sample plot, the diameter and length of each woody piece were measured, and its decay class (1 to 4) was recorded based on visual and tactile criteria. The volume of each piece was calculated using Huber's formula. To determine basic density, three wood samples per decay class per stand were collected, and their dry weight was determined after oven-drying at 105°C. Biomass was obtained by multiplying volume by basic density, and carbon content was estimated using a conversion factor of 0.5. Additionally, distance from the road, slope percentage, and a stand accessibility index were recorded.
Results: The frequency of fine woody debris (507 pieces per hectare) in the protected stand was significantly lower than that in the other stands. The frequency of coarse woody debris in the shelterwood and single-selection stands was significantly higher than that in the protected stand. The shelterwood and protected stands had the highest volumes of fine woody debris, with 4.61 and 4.47 m³ per hectare, respectively, while the protected stand had the highest volume of coarse woody debris, at 14.25 m³ per hectare. The protected stand exhibited the highest frequency of highly decayed woody debris (30.8%) and the lowest frequency of low-decay woody debris (15.5%). The shelterwood stand had the highest fine woody debris biomass (1062 kg per hectare), and the protected stand had the highest coarse woody debris biomass (3028 kg per hectare). The highest carbon content of fine woody debris was found in the shelterwood stand (531 kg per hectare), while the highest carbon content of coarse woody debris was observed in the protected stand (1989 kg per hectare). The forest accessibility index showed the strongest negative correlation with coarse woody debris volume. Additionally, fine woody debris volume had a significant positive correlation with slope gradient and distance from the road.
Conclusion: This study demonstrated that lower-intensity management practices with longer harvest cycles (such as the shelterwood method with a 40-year interval) can largely maintain the carbon storage capacity and natural decay dynamics of woody debris, allowing recovery to conditions close to those of the conservation stand. In contrast, repeated human disturbances (especially the combined harvesting of standing and windthrown trees) rapidly deplete these vital stocks and shift their dynamics toward fresh, fast-decomposing material. Forest accessibility was identified as the strongest determinant of woody debris quantity. It is recommended that forest management plans in the Hyrcanian region prioritize the preservation of areas with difficult access, avoid the complete removal of logging residues, and favor close-to-nature silvicultural practices to maintain carbon sequestration functionss and biodiversity.
کلیدواژهها [English]
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