تعیین فاصلۀ بهینۀ زهکش‌های عرضی در مسیرهای چوبکشی به‌منظور انحراف رواناب (مطالعۀ موردی: جنگل خیرود)

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی کارشناسی ‌ارشد مهندسی جنگل، دانشکدۀ منابع طبیعی، دانشگاه تهران

2 استاد گروه جنگلداری و اقتصاد جنگل، دانشکدۀ منابع طبیعی، دانشگاه تهران

3 دانشیار گروه احیای مناطق خشک و کوهستانی، دانشکدۀ منابع طبیعی، دانشگاه تهران

چکیده

استفاده از ماشین‌آلات چوبکشی در مناطق پرشیب جنگل‌های شمال برای خروج چوب موجب افزایش وزن مخصوص ظاهری و کوبیدگی خاک و کاهش نفوذ آب در خاک مسیر چوبکشی، افزایش رواناب و هدررفت خاک می‌شود. این پژوهش با هدف تعیین فاصلۀ بهینۀ بین زهکش‌های عرضی در مسیرهای چوبکشی به‌منظور کاهش رواناب در پارسل‌های 315 و 316 بخش گرازبن جنگل خیرود انجام گرفت. در این پژوهش، نه پلات با طول‌های 20، 30 و 40 متر در شیب‌های طولی 15، 25 و 35 درصد مسیرهای چوبکشی نصب شدند. در خروجی هر پلات، یک مخزن برای جمع‌آوری رواناب مستقر شد. در هر پلات، متغیرهای جرم مخصوص ظاهری خشک، درصد رطوبت وزنی، درصد مادۀ آلی و بافت خاک و نیز در هر واقعۀ بارندگی، مقدار بارندگی روزانه و رواناب جمع‌شده در مخزن اندازه‌گیری شد. نتایج نشان داد که فاصلۀ بهینۀ زهکش‌های عرضی در مسیرهای چوبکشی برای کاهش رواناب 30 متر است و مناسب‌ترین شیب مسیر چوبکشی به‌منظور کاهش رواناب، شیب تا 25 درصد است. براساس نتایج، مقدار رواناب با طول پلات دارای رابطۀ معنی‌دار است. نتایج تحلیل رگرسیون نشان داد که مقدار بارندگی با رواناب در طول‌ها و شیب‌های مختلف پلات‌ها رابطۀ معنی‌دار دارد. از این‌رو برای کاهش رواناب در مسیرهای چوبکشی بهتر است تا حد امکان از ساخت این مسیرها در شیب‌های تند خودداری شود و بعد از عملیات چوبکشی، اقداماتی مانند ساخت زهکش‌های عرضی (با طول 30 متر و زاویۀ شیب 25-20 درصد) برای کاهش رواناب انجام گیرد.

کلیدواژه‌ها


عنوان مقاله [English]

Optimal distance among water diversion structures for mitigating runoff on the skid trails (case study: Kheyrud forest)

نویسندگان [English]

  • K. Fathi 1
  • M Jourgholami 2
  • S.A. Hosseini 2
  • Sh. Khalighi Sigaroodi 3
1 MSc Student of Forest Engineering, Faculty of Natural Resources, University of Tehran, I. R. Iran
2 Prof., Dept. of Forestry and Forest Economics, Faculty of Natural Resources, University of Tehran, I. R. Iran
3 3Associate Prof., Dept. of Reclamation of Arid and Mountainous Regions, Faculty of Natural Resources, University of Tehran, I. R. Iran
چکیده [English]

Using machinery wood extraction in steep slope in the Hyrcanian forests can increase the soil bulk density and soil compaction, decrease the infiltration water into soil of skid trail, which results in an increase runoff and soil loss and has detrimental effects on soil nutrients loss and sedimentation into the downstream infrastructure. The aim of this study was to investigate the optimal distance of water diversion in skid trails to mitigate sthe ediment and runoff in compartments 315 and 316 of Gorazbon district in Kheyrud forest. In this study, 9 plots with length of 20, 30 and 40 m and slope gradient of 15, 25 and 35% were established along the longitudinal slope of the skid trails. A tank was installed to collect runoff at the outlet of each plot. Also, runoff in each rain event as well as soil bulk density, moisture content, organic matter, and soil texture of the plots were measured. The results revealed that the optimal distance among water diversions in the skid trails to suppress the runoff was 30 m and the most appropriate slope for mitigating runoff on the skid trails was up to 25% slope gradient. Runoff had a significant relationship with plot length. The results showed that the amount of rainfall was significantly correlated with runoff at different lengths and slopes. Therefore, it should be avoided to plan the skid trails on steep slopes for mitigating runoff, and some engineering measures such as the installing water diversion structures (by length of 30 m and slope gradient of 20-25%) to decrease the runoff should be done.

کلیدواژه‌ها [English]

  • Skidding operation
  • Soil compaction
  • Water diversion structure
  • Soil physical properties
  • Kheyrud forest
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