نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه علوم و مهندسی جنگل، دانشکده علوم جنگل، دانشگاه علوم کشاورزی و منابع طبیعی گرگان، گرگان، ایران

2 بخش معاونت فنی، اداره جنگلداری و جنگلکاری، اداره کل منابع طبیعی و آبخیزداری استان البرز، کرج، ایران

چکیده

سابقه و هدف:
با توجه به اهمیت جاده های جنگلی و اثرهای مثبت و منفی آنها بر اکوسیستم جنگل، در این پژوهش به بررسی اثرهای جاده جنگلی بر سنجه های تنوع گونهای مرتبط با درختان و درختچه ها در جنگل های شهرستان پاسارگاد، پرداخته شد.
مواد و روشها:
پس از بررسی های میدانی، تعداد 30 پالت 400 مترمربعی (20متر×20متر) در امتداد جاده جنگلی درجه سه با فاصله طولی 100 متر در فاصله های 20 - 0 متری، 60 - 40 متری و 100 - 80 متری عمود بر دو طرف جاده پیاده گردید و گونه های درختی و درختچه ای موجود در آنها برداشت شد. سپس با استفاده از نرم افزارهای مربوطه، سنجه  های تنوع، غنا و یکنواختی گونه ای محاسبه گردید و میانگین هر سنجه در فاصله های مشابه اندازه گیری شد. اثر فاصله از جاده روی سنجه های تنوع، غنا و یکنواختی با استفاده از آنالیز واریانس یکطرفه در قالب رویه ANOVA Way One تعیین گردید و از آزمون دانکن نیز بهمنظور مقایسه چندگانه میانگین استفاده شد.
نتایج و بحث:
نتایج آماربرداری از درختان در منطقه مورد مطالعه نشان داد که گونه تنگرس بیشترین و گونه ارملک (ریش بز) کمترین مقدار فراوانی را در پالت ها دارند. با توجه به نتایج بهدست آمده، میانگین مقادیر سنجه های تنوع، غنا و یکنواختی در فاصله های مختلف از جاده اختالف معنیداری را نشان ندادند. همچنین نتایج تجزیه واریانس نشان داد که بین مقادیر سنجه های تنوع گونه ای بیان شده در فاصله های مختلف از جاده، اختلاف معنی داری در سطح اطمینان 95 درصد وجود ندارد.
نتیجه گیری:
رقابت نوری یکی از عاملهای تأثیرگذار بر استقرار درختان و درختچه ها میباشد. در منطقه مورد مطالعه به دلیل فاصله های زیاد درختان از یکدیگر، رقابت نوری وجود ندارد و بنابراین وجود جاده در این شرایط نمیتواند تأثیری بر رقابت نوری درختان داشته باشد.از طرفی نتایج نشان میدهد با افزایش فاصله از جاده، تراکم پایه های درختی و درختچه ای و همچنین سنجه های تنوع گونه ای اختلاف معنی داری را نشان نمیدهند. جاده های جنگلی درجه سه به دلیل نوع کاربرد و محدود بودن زیرسازی و روسازی و اکتفا به عملیات خاکبرداری و خاکریزی در آنها، در فصلهای محدودی از سال قابل استفاده هستند و اثرهای منفی عاملهای بیرونی نظیر حضور انسان محدود میشود. بنابراین افزایش فاصله از جاده جنگلی درجه سه در منطقه مورد مطالعه، تأثیری بر غنا، تنوع و یکنواختی گونه های درختی و درختچه ای ندارد.

کلیدواژه‌ها

عنوان مقاله [English]

Influence of forest road on tree and shrub biodiversity indices in Irano-Turanian forests (case study: Pasargad forests)

نویسندگان [English]

  • Mohammad Hasan Naseri 1
  • Mohammad Rostamian 2

1 Department of Forest Science and Engineering, Faculty of Forest Science, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran

2 Technical Deputy, Department of Forestry and Afforestation, Alborz Natural Resources Office, Karaj, Iran

چکیده [English]

Introduction:
Considering the importance of forest roads and their positive and negative effects on the forest ecosystem, in this study, the effects of a forest road on species diversity indices related to trees and shrubs in forests of Pasargad city were investigated.
Material and methods:
After field surveys, 30 plots of 400 square meters (20×20 m) were placed on both sides of the road perpendicular along the third-grade forest road with a distance of 100 meters in 0 to 20, 40 to 60 and 80 to 100 m intervals and the species of trees and shrubs were investigated. Then, richness and uniformity indices were calculated and the mean of each index was measured at similar intervals. Then, in SPSS software, the data were normalized by the Kolmogorov-Smirnov test as well as homogeneity analysis of variance using Leven's test. The effect of distance from the road on diversity, richness, and uniformity was determined using a one-way ANOVA method, and Duncan's test was also used to compare the multiple means.
Results and discussion:
The results of the census of the trees in the study area showed that Amygdalus lycioides species had the highest and Ephedra foliate species had the least abundance in the plots. According to the results, the mean values of diversity, richness, and uniformity indices at different distances from the road showed no significant difference. Also, analysis of variance for values of diversity, richness, and evenness indices at specified intervals showed that there was no significant difference in the 95% confidence level between the values of these indices at different distances from the road.
Conclusion:
Light competition is one of the factors affecting the establishment of trees and shrubs. There was no light competition in the study area due to the long distances between trees and, therefore, the presence of roads in these conditions wouldn’t affect the light competition. On the other hand, the results showed that with increasing distance from the road, there were no significant differences between the density of trees and shrubs and species diversity indices. Third-grade forest roads are used during limited seasons of the year due to limited infrastructure and pavement, and so the adverse effects of human presence would be limited. Therefore, increasing the distance from third-grade forest road in the study area did not affect the richness, diversity, and evenness of tree and shrubs species.

کلیدواژه‌ها [English]

  • Forest ecosystem
  • Forest road
  • Species diversity
  • Species richness
  • Species uniformity

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