بررسی اثر جهات جغرافیایی و فاصله از قشر نمکی پلایا بر ترکیب و تنوع گونه‌ای (مطالعه موردی: پلایای سیرجان)

نویسنده

دانشگاه تحصیلات تکمیلی صنعتی و فناوری پیشرفته

چکیده

اثر عوامل محیطی بر شاخص‌های تنوع و غنای گونه‌ای در اکوسیستم‌های شکنندۀ اطراف پلایا‌ها کمتر مورد توجه قرار گرفته است. بنابراین این پژوهش به‌منظور بررسی اثر جهت جغرافیایی و فاصله از قشر نمکی پلایا بر شاخص‌های ترکیب و تنوع گونه‌ای در پلایای سیرجان واقع در استان کرمان انجام شد. انتخاب فواصل ده، هزار و دوهزار متری در چهار جهت جغرافیایی اصلی اطراف قشر نمک (شمال، جنوب، شرق و غرب) با استفاده از دستگاه موقعیت‌یاب GPS و پیمایش صحرایی به‌عمل آمد. در امتدادی عمود بر جهت، نمونه‌برداری پوشش گیاهی در هر لاین فاصله به کمک رلوه (با ابعادی معادل روش حداقل سطح) در اوایل اردیبهشت 1395، با سه تکرار به‌صورت سیستماتیک انجام شد. پس از تعیین شاخص‌های تنوع هر واحد نمونه در نرم‌افزارهای PAST و BIO-DAP، تجزیه و تحلیل آماری داده‌ها به‌صورت تجزیۀ واریانس (ANOVA) و مقایسۀ میانگین‌ها با آزمون چنددامنه‌ای دانکن انجام شد. نتایج نشان داد اثر اصلی متغیرهای جهت جغرافیایی و فاصله از پلایا و نیز اثر متقابل آن‌ها بر تمامی شاخص‌های تنوع و غنای گونه‌ای، معنی‌دار بود. در تمامی جهت‌های جغرافیایی در فواصل 10 متری از قشر نمکی پلایا به‌دلیل غالبیت تک‌بعدی گونه گیاهی Halocnemum strobilaceum و عدم حضور پررنگ سایر گونه‌های گیاهی، شاخص‌های چیرگی (دی و برگر) و یکنواختی جاکارد حداکثر و شاخص‌های غنا (منهینگ، مارگارف و فیشر) و تنوع (شانون‌ـ وینر، سیمسون) حداقل بود. به‌علت حضور بالای سایر گونه‌های گیاهی همراه با گیاه شورروی Halocnemum strobilaceum در فاصلۀ هزار متری از قشر نمکی در همۀ جهت‌ها (به‌استثنای جهت غرب) تمامی شاخص‌های غنا و تنوع برعکس شاخص‌های چیرگی و یکنواختی افزایش معنی‌داری داشت و این وضعیت در فاصلۀ دوهزار متری در اکثر شاخص‌ها حفظ شد. با توجه به توسعۀ پهنای نوار تک‌گونۀ گیاهی Halocnemum strobilaceum با تنوع گونه‌ای بسیار پایین، جمعیتی ضعیف و غیریکنواخت با افزایش فاصله از پلایا در سمت غرب، احتمال گسترش خطر بیابان‌زایی و تخریب سرزمین در این جهت بیشتر از سایر جهت‌هاست.

کلیدواژه‌ها


عنوان مقاله [English]

The effect of geographical directions and distance from Playa salt layer on the composition and diversity of plant species (Case Study: Sirjan Playa)

نویسنده [English]

  • Sedigheh Mohamadi
چکیده [English]

It has been paid less attention to effect of environmental factors on species richness and diversity indices in fragile ecosystems around Playa. Therefore this study was conducted to evaluate the effect of geographical directions and distance from Playa salt layer on the composition and species diversity in Sirjan Playa, Kerman Province, Iran. Determination of intervals 10, 1000 and 2000 meters in four main geographical aspects surrounding salt crust (North, South, East and West), were done using GPS positioning and field operation. Along the perpendicular direction, sampling of vegetation in each distanc by relevee (with dimensions equal to minimum level) in early May 2016 with three replications was carried out systematically. After determining the diversity of each unit in the software PAST and BIO-DAP, statistical analysis of data for analysis of variance (ANOVA) and mean comparison with Duncan's multiple range test was performed by SPSS software.The results showed that the main effects and interaction of geographical directions and distance from playa salt layer on all indicators of species diversity and richness were significant. In all directions at intervals of 10 meters of salt crust due to the dominance of one-dimensional of Halocnemum strobilaceum plant species and the absence of other plant species, dominance index and uniformity index of Jaccard were maximum and cotroversially richness (Menhing, Margarf and Fisher) and diversity (Shannon - Wiener, Simpson) were minimal. Due to the presence of other plant species with Halocnemum strobilaceum in 1000 meter of distance of all directions (except for the west), all the richness and diversity on the contrary of dominance and uniformity indicators increased significantly and the situation in most indicators were kept at a distance of 2000 meters. According to the development of a single plant species (Halocnemum strobilaceum) strip with very low species diversity and non-uniformly with increasing distance from center of playa in the west, likely to spread the risk of desertification and land degradation in this direction than in other directions.
 

کلیدواژه‌ها [English]

  • Aspects
  • Playa
  • Halophyte
  • Species richness
  • Kerman
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