بررسی تأثیر چرای دام بر مؤلفه‎های تنوع گیاهی مراتع نیمه‌خشک کشور

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجوی دکترایدانشجوی کارشناسی ارشد مرتعداری، دانشکدۀ منابع طبیعی، دانشگاه تربیت مدرس مرتع، دانشگاه شهرکرد

2 دانشیار گروه مرتعداری، دانشکدۀ منابع طبیعی، دانشگاه تربیت مدرس

3 استادیار گروه مرتع و آبخیزداری، دانشکدۀ کشاورزی، دانشگاه ایلام

چکیده

چرای شدید دام یکی از مخرب‎ترین عوامل در عرصۀ مراتع نیمه­خشک کشور است که باعث کاهش تنوع و از بین رفتن برخی از گیاهان حساس به چرا می‏گردد. از طرف دیگر با توجه به تغییرپذیری الگوی پراکنش گونه‎های گیاهی در مقیاس‌های مختلف، لزوم استفاده از مقیاس در ارزیابی‎های تنوع ضروی است. بنابراین این تحقیق با استفاده از روش تقسیم‏بندی افزایشی به بررسی تأثیر چرای دام روی مؤلفه‎های تنوع در مقیاس‌های گوناگون در مراتع غرب کشور در ایلام می­پردازد. بدین منظور نمونه‎برداری از 40 پلات 4 مترمربعی در 8 سایت مرتعی شامل 4 سایت قرق و چهار سایت در حال چرا انجام گرفت. بر اساس روش تقسیم‎بندی افزایشی کل تنوع به مؤلفه‏های افزایشی درون و بین نمونه‎ها (پلات و سایت) تقسیم‎بندی گردید. نتایج نشان داد که تنوع بین سایت (بتا2) دارای بیشترین سهم از تنوع کل بود که نشان دهندۀ تفاوت در ترکیب بین سایت‎ها و اهمیت این مقیاس برای امور حفاظتی است. همچنین اعمال قرق سبب افزایش تنوع گونه‎ای در سطح پلات (آلفا 1 و بتا1) گردید، در حالی که سبب کاهش تنوع گونه‎ای در مقیاس‌ سایت (تنوع بین سایت‎ها یا بتا2) شد. بنابراین الزاماً قرق کردن مراتع منجر به افزایش تنوع به­ویژه در سطوح وسیع­تر نخواهد شد. همچنین قرق دراز مدت می‎تواند منجر به افزایش یکنواختی و افزایش رقابت بین گیاهان شده و در نهایت تنوع گونه‏ای را کاهش دهد.

کلیدواژه‌ها


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