بررسی تأثیر آتش سوزی بر پایداری خاکدانه ها، عوارض قابل مشاهده سطحی و پوشش گیاهی در مقیاس های مختلف در جنگل های سواحل جنوب غربی دریای مازندران

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری دانشکده کشاورزی گروه خاکشناسی دانشگاه شهرکرد

2 دانشیار گروه خاکشناسی دانشکده کشاورزی دانشگاه شهرکرد

3 استاد گروه خاکشناسی دانشکده کشاورزی دانشگاه شهرکرد

4 استادیار دانشکده کشاورزی و منابع طبیعی دانشگاه اردکان

چکیده

سابقه و هدف: تخریب اراضی جنگلی در اثر آتش سوزی یکی از بزرگترین مشکلات زیست محیطی شمال کشور است که به طور معنی داری پوشش گیاهی و عوارض قابل مشاهده سطح خاک را تغییر داده و بنابراین بر میزان پایداری خاکدانه ها در برابر نیروهای فرساینده تأثیرگذار می باشد. با داشتن اطلاعات کامل از میزان پایداری خاکدانه ها در مقیاس خرد و نوع عوارض مرتبط با فرسایش خاک در مقیاس های کرت و حوضه آبخیز بهتر می توان در مورد خطر فرسایش در منطقه قضاوت کرد. این پژوهش با هدف بررسی تأثیر آتش سوزی بر پایداری خاکدانه ها، عوارض قابل مشاهده سطحی و ویژگی های پوشش گیاهی در مقیاس های خرد، کرت و حوضه آبخیز در بخش هایی از اراضی جنگلی واقع در شمال غرب استان گیلان انجام گرفت.
مواد و روش ها: در قطعاتی در داخل محدوده 15 ناحیه آسیب دیده در اثر آتش سوزی و 15 منطقه نسوخته مجاور آنها، در پنج واحد ژئومورفولوژی مختلف، شاخص های پایداری خاکدانه ها در مقیاس خرد و اشکال میکروتوپوگرافی فرسایش و درصد لاشبرگ در مقیاس کرت اندازه گیری شدند. همچنین برخی ویژگی های پوشش گیاهی، شاخص تراکم آبراهه ها و برخی از اشکال مورفودینامیکی فرسایش مورد بررسی قرار گرفتند.
یافته ها: نتایج آنالیز واریانس نشان داد که شاخص های پایداری خاکدانه ها، درصد لاشبرگ و شاخص تراکم آبراهه ها اختلاف معنی داری بین نقاط آتش سوزی و شاهد (داخل گروه ها) داشتند. در بین واحدهای ژئومورفولوژی (بین گروه ها) نیز تنها از نظر درصد لاشبرگ اختلاف معنی دار وجود داشت. نتایج همچنین مشخص کرد که حدود چهار تا پنج سال طول کشید تا میزان شاخص های پایداری خاکدانه ها و تراکم آبراهه ها به شرایط قبل از آتش سوزی برسد. همچنین افزایش شدت آتش سوزی از کم به زیاد و تغییر نوع آتش سوزی از سطحی به تاجی بیشترین تأثیر را بر میانگین وزنی قطر خاکدانه ها داشت. نتایج بررسی اشکال میکروتوپوگرافی فرسایش در مقیاس کرت نشان داد که برخی از آنها در نقاط آتش سوزی نسبت به شاهد دچار تغییر شده بودند. در مقیاس حوضه آبخیز نیز شیارها، لغزش های رخ داده و خندق ها بیشتر در نواحی آتش سوزی وجود داشتند. ضرایب همبستگی ایجاد شده بین ویژگی های مربوط به مقیاس های مختلف مشخص کرد که همبستگی معنی داری بین برخی ویژگی های اندازه گیری شده در مقیاس های مختلف وجود دارد.
نتیجه گیری: از شاخص های پایداری خاکدانه ها می توان در مقیاس خرد به عنوان یک معیار ارزیابی مفید در بررسی میزان قدرت شکل گیری اشکال مختلف میکروتوپوگرافی و مورفودینامیکی فرسایش خاک در مقیاس های کرت و حوضه آبخیز استفاده کرد. نتایج این بررسی می تواند در ارزیابی خطر فرسایش خاک های اراضی جنگلی و مدیریت جنگل به کار رود.

کلیدواژه‌ها


عنوان مقاله [English]

Study the effect of fire on aggregate stability, surface visible features and vegetation cover at the different scales in forests of south western coastal zone of the Caspian Sea

نویسندگان [English]

  • ali akbarzadeh 1
  • Shoja Ghorbani Dashtaki 2
  • Mehdi Naderi Khorasgani 2
  • Jahangard Mohammadi 3
  • Ruhollah Taghizadeh Mehrjardi 4
1 Ph.D. Student, Faculty of Agriculture, Department of Soil Science, Shahrekord University
2 Associate Professor, Department of Soil Science, Faculty of Agriculture, Shahrekord University
3 Professor, Department of Soil Science, Faculty of Agriculture, Shahrekord University
4 Assistant Professor, Faculty of Agriculture and Natural Resources, Ardakan University
چکیده [English]

Background and Objectives: Degradation of forest lands by fire is one of the major bioenvironmental problems in northern Iran that significantly changes the vegetation attributes and visible features at the soil surface and therefore, affects aggregate stability against erosive forces. The complete information from aggregate stability at the micro scale and type of features related to soil erosion at the plot and watershed scales leads to a perfect judgment about erosion risk in an area. The objective of this study was to evaluate the effect of fire on aggregate stability, surface visible features and vegetation cover at the micro, plot and watershed scales in some parts of forest lands in west northern zone of the Guilan province.
Material and Methods: In parcels separated in 15 fire-affected forests and 15 unburned forests adjacent to the fire-affected forests, in five geomorphological units, aggregate stability indices at the micro scale and microtopographic erosion features and litter percentage at the plot scale were measured. In addition, some vegetation attributes, drainage density index, and the presence of some morphodynamics features of soil erosion were evaluated at the watershed scale.
Results: The results of analysis of variance showed that all aggregate stability indices as well as litter percentage and drainage density had significant differences within subjects (within burned and unburned forests). Among studied parameters, only litter percentage showed significant differences between subjects (geomorphological units). Results also revealed that the time reversibility for aggregate stability indices and drainage density to condition before fire was about four to five years. Also, increasing the fire severity from low to high and changing of fire type from surface to canopy had the most effect on mean weight diameter of aggregates. Assessment of microtopographical erosion features at the plot scale revealed that some of them had variations in burned sites compared with the control sites. At the watershed scale, the rills, gullies and landslides were more abundant in the burned sites than the unburned sites. The correlation coefficients between measured properties related to different scales showed that there were significant correlations between some of them at the various scales.
Conclusion: The soil aggregate stability indices are very useful to evaluate the power of formation of many microtopographic and morphodynamics features of soil erosion at the plot and watershed scales. The results of this study can be used for assessment of soil erosion risk in forest lands and can be useful for management of woodlands.

کلیدواژه‌ها [English]

  • Aggregate stability
  • Drainage density
  • Gully
  • Landslide
  • Rill
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