بررسی تاثیر پخش سیلاب بر پوشش گیاهی و تنوع گونه‌ای در حوضه آبخیز آب‌بید سربیشه گتوند در استان خوزستان

فرسایش آبی یکی از مهم‌ترین انواع تخریب اراضی در اغلب نقاط ایران است که سبب از بین رفتن خاک حاصلخیز شده است. در این راستا اجرای اصولی پروژه‌های آبخیزداری و اقدامات بیولوژیکی، به‌ویژه استفاده از پوشش گیاهی بومی در بخش‌هایی از آبخیز که وضعیت فرسایشی ضعیف و متوسطی دارد، می‌تواند فرسایش خاک را مدیریت نماید. پایش شاخص‌های تنوع‌زیستی در این مناطق می تواند سبب آشکارسازی اثر سازه‌های آبخیزداری بر رویش‌های بومی بعد از گذشت حدود بیست سال شود. هدف از این پژوهش مستندسازی و آنالیز پوشش گیاهی منطقه بوده که سبب آشنایی بهتر با گونه‌های خودرو و اثر پخش سیلاب بر رویش‌های بومی با استفاده از شاخص‌های پوشش گیاهی می‌شود. در این پژوهش آنالیز پوشش گیاهی در منطقه آبخوان آب‌بید-سربیشه در استان خوزستان با استفاده از شاخص‌های تنوع زیستی صورت گرفت. طی بازدیدهای صحرایی از سازه­های احداث شده در ایستگاه دو قطعه یک هکتاری در محل پخش سیلاب و شاهد در نظر گرفته شد. سپس به‌صورت تصادفی تعداد 30 پلات در بستر پخش سیلاب و 30 پلات در خارج آن زده شد. در فصل رویش درصد پوشش زنده گونه­ها، درصد زمین لخت، لاشبرگ و خاشاک، ثبت شد. همچنین تمام گونه­های گیاهی تا حد زیرگونه و واریته شناسایی شدند. در نهایت شاخص­های تعداد گونه، درصد پوشش و تنوع گونه­ای محاسبه شدند. پیمایش میدانی سبب شناسایی 40 گونه گیاهی متعلق به 16 تیره در این منطقه شد. 90 درصد گونه‌ها‌ دارای شکل رویشی تروفیت هستند. همچنین بین میانگین همه شاخص‌های پوشش گیاهی در  پلات‌های  بستر پخش سیلاب با پلات‌های خارج از بستر اختلاف معنی‌داری در سطح یک درصد وجود دارد. در بستر پخش سیلاب تعداد گونه‌، درصد پوشش، شاخص سیمپسون و شاخص شانون مقدار بیشتری نسبت به منطقه شاهد دارند، که بیانگر نقش موثر عملیات پخش سیلاب در منطقه است.

vegetation and species diversity in the floodplain of the abbid sarbisheh-gotvand watershed in khuzestan province

introduction water erosion is one of the most important challenges of land degradation in most parts of iran، leading to the loss of fertile topsoil. this phenomenon، occurring through two distinct processes، includes the disintegration of the soil bed due to raindrop impact and the transport of these disintegrated particles، as well as surface erosion and the washing of nutrients and various pollutants by runoff، resulting in numerous environmental problems. one of the principled solutions in this regard is the implementation of watershed management projects. in this regard، the principled implementation of watershed management projects and biological measures، especially the use of native vegetation cover in parts of the watershed that have low and moderate erosion، can effectively control soil erosion. on the other hand، measuring species diversity indices is widely used in plant research and environmental assessments as an important indicator in determining the status of an ecosystem. therefore، monitoring and measuring biodiversity indicators in these areas can reveal the effect of watershed management structures on native vegetation after nearly twenty years. the purpose of this research is to document and analyze the vegetation of the region، providing a better understanding of the list of wild species and the impact of flood spread on native vegetation using vegetation indicators.materials and methods in this study، vegetation analysis was carried out in the abbid-sarbisheh aquifer zone located in gotvand county، khuzestan province، using biodiversity indicators. based on field surveys of the structures constructed at the station، two one-hectare plots were considered in the floodplain and control areas. since the vegetation was similar in terms of species composition، 30 plots were randomly planted in the floodplain and 30 plots outside it. ten soil samples were collected using a soil auger and after removing debris from depths of 0 to 30 and 30 to 60 cm from a one-hectare sample plot of the flood area and the control area  and sent to the soil laboratory for chemical and physical soil tests، acidity، electrical conductivity، percentage of organic matter and elements p، k، fe، zn، mn، cu. meteorological statistics (temperature and precipitation) were obtained from the dezful synoptic station، which was closest to the region، for the research year، and the ambrothermal curve was prepared in excel. considering the climatic conditions of khuzestan province، during the appropriate growing season، the percentage of live cover of species، the percentage of bare ground، litter، and debris were recorded. also، after pressing and drying the specimens and pasting them onto the herbarium sheet، all plant species were identified to the subspecies and variety level. then، the indices of species number، percentage of cover، and species diversity (simpson and shannon) were calculated using past 2.17 software. vegetation cover in the plots was statistically compared using an independent t-test.results and discussion within the flood-spreading regions، a survey identified 40 plant species belonging to 16 families in this area. 90% of the species had a therophyte or annual and short-lived vegetative form. in this area، 40 plant species belonging to 16 families were identified. of these، the families astraceae، fabaceae، and poaceae have the highest number of species in the regions. perennial shrubs and herbaceous plants constitute a small percentage of the area's cover (10%). in the plots studied، perennial and shrub species such as convolvulus reticulatus and onobrychis gypsicola were rarely seen، but were seen as spots in some places next to the native shrub species ziziphus spina-christi and ziziphus nummularia and the cultivated trees and shrubs eucalyptus camaldulensis and prosopis juliflora. two species exclusive to iran، a type of chamomile، anthemis austro-iranica، and onobrychis gypsicola، were also observed scattered in the floodplains. the results of statistical analysis also showed that there is a significant difference at the 1% level between the average of all shannon، simpson indices، percentage of cover، and number of plant species in plots in the floodplain area and plots outside the floodplain. in the floodplain، the number of species، percentage of cover، simpson index، and shannon index are higher than in the control area، which indicates the effective role of floodplain operations in the area. conclusionsoil data analysis in the floodplain shows that the soil texture in the floodplain area is heavier due to a higher clay content، which is probably due to seasonal flood sediments، and for this reason، it can be concluded that it has better conditions for water retention than the control area. in this region، summer and spring are warm to hot، and autumn and winter are moderate. atmospheric precipitation، like in other dry regions، has an inappropriate temporal and spatial distribution. in such extreme climatic conditions، the management of surface water resources، especially seasonal floods، has been one of the most fundamental and essential activities in the region. the watershed management structures constructed in the region and، subsequently، the floodplain spread over recent decades have gradually created suitable conditions for the presence of plant species in the region by changing the bed. increased species richness and their uniform distribution are the components that have led to the improvement of simpson and shannon diversity indices in the flood spreading area compared to the control. floodplain operations have an effective role in restoring vegetation and species diversity and can be implemented as a model in other regions of the khuzestan plain with similar conditions. despite the emergence of vegetation following floodplains، these regions are still very fragile، and the diversity of vegetation is dependent on rainfall due to the dominance of short-lived species. therefore، in addition to preventing destruction، purposeful fencing and grazing management in the region should also be considered.