نوع مقاله : مقاله پژوهشی
نویسندگان
1 استادیار گروه مرتع و آبخیزداری، دانشکده کشاورزی و منابع طبیعی دانشگاه ارومیه، ایران
2 دانشیار پژوهشی، بخش تحقیقات مرتع، موسسه تحقیقات جنگلها و مراتع کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران
چکیده
این تحقیق به‌‌منظور مطالعه تغییرات تنوع گونهای در مراتع کوهستانی چهار باغ استان گلستان در پنج سایت با مدیریت متفاوت شامل بدون چرا (قرق)، چرای متوسط (کلید) و بحرانی (حریم روستا، حریم آبشخور و اطراف آغل) انجام شد. با برداشت داده‌‌های پوشش گیاهی، شاخصهای تنوع عددی و پارامتری محاسبه شد. نتایج آنالیز واریانس یک‌‌طرفه نشان داد که سایتهای قرق و کلید از لحاظ شاخص تنوع شانون (به‌‌ترتیب 6/2 و 1/2) در مقایسه با سایتهای بحرانی در وضعیت بهتری قرار دارند، اما از لحاظ شاخص غنای مارگالف تفاوتی بین سایت‌‌ها مشاهده نشد. بالاتر قرار گرفتن منحنی درجه‌‌بندی تنوع سایت کلید، بیانگر بیشتر بودن تنوع آن نسبت به سایت قرق است. به‌طوری‌که با برازش مدل‌‌های توزیع فراوانی مشخص شد که سایت قرق و کلید با مدل‌‌های سری لوگ (جوامع پایدار) و سایتهای بحرانی با مدل سری هندسی (جوامع ناپایدار) در سطح 05/0 برازش و ارتباط دارد. رسم منحنی فراوانی- رتبه گونهای نشان داد که سایتهای با چرای زیاد دارای گونه‌‌های نادر و غالب با تعداد زیاد است که بیانگر اثر فشار چراست، اما در سایت متوسط و قرق یکنواختی بالایی در عرصه حاکم است. نتایج کلی نشان داد که اعمال چرای متوسط، سبب حفظ تنوع گیاهی شده و قرق اثر چندانی در افزایش تنوع گیاهی مراتع نداشته است که این بر لزوم توجه به اعمال چرای متوسط در عرصه صحه می‌‌گذارد. در بین سایتهای بحرانی، سایت حریم روستا در وضعیت بدتری قرار گرفته و پیشنهاد می‌‌شود به‌‌دلیل نقش مؤثر اثبات شده چرای متوسط در منطقه، برای احیای سایتهای با شدت چرای بالا به‌ویژه حریم روستا، شدت چرای دام کاهش یابد. البته کاهش تراکم دام در نقاط بحرانی از طریق افزایش تعداد آبشخورها و محل‌‌های استراحت دام در عرصه از روش‌‌های کمک کننده به کاهش آسیب به تنوع گیاهی سایتهای بحرانی خواهد بود.
کلیدواژه‌ها
عنوان مقاله [English]
Evaluation of species diversity indices in Chaharbagh rangelands of Golestan province
نویسندگان [English]
- Esmaeil Sheidai Karkaj 1
- Javad Motamedi 2
1 Assistant Professor, Department of Range and Watershed Management, Faculty of Agriculture and Natural Resources, Urmia University, Urmia, Iran
2 Associate Professor, Rangeland Research Division, Research Institute of Forests and Rangelands, Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran
چکیده [English]
This study was conducted to study species diversity changes in Chaharbagh mountain rangelands of Golestan province in five different managed sites, including non-grazing (enclosure), intermediate grazing (key), and critical (village vicinity, watering point, and pen area). Numerical and parametric diversity indexes were calculated by collecting vegetation data. One-way ANOVA results showed that exclusion and key sites were better for the Shannon diversity index (2.6 and 2.1, respectively) than critical sites; however, no differences were found in the Margalef richness index. A higher ranking of diversity site of the key site indicates that it is more diverse than the restricted site. By fitting the frequency distribution models, it was determined that the exclusion and key site were related to the log series models (stable communities), and the critical sites were related to the geometric series model (unstable communities) at the 0.05 level. Frequency-rank curve plotting indicated that high grazing sites had rare and dominant species with high numbers indicating the effect of grazing pressure; however, moderate sites and high grazing sites have high evenness. Overall, the results showed that moderate grazing preserved the vegetation diversity, and exclusion had no significant effect on increasing vegetation diversity in rangelands. This result confirms the need to pay attention to moderate grazing in the field. Among the critical sites, the village privacy site is in a worse situation, and livestock grazing intensity should be reduced due to the proven effective role of medium grazing in the region to rehabilitate sites with high grazing intensity, especially in rural areas. Reducing livestock density in critical areas by increasing the number of water sources and rest areas in the field will be one of the methods to help reduce damage to plant diversity of critical sites.
کلیدواژه‌ها [English]
- Livestock grazing
- plant diversity indices
- distributive model
- rank- abundance curve
- Chaharbagh rangelands
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