ارزیابی تاثیر خصوصیات فیزیکی و شیمیایی خاک در شکل‌گیری و گسترش فرسایش خندقی (منطقه مورد مطالعه: حوضه آبخیز رودخانه شور)

یکی از فرایندهای فرساینده سطح زمین که به تغییر شکل این سطح و خسارت های شدید محیطی و اقتصادی منجر می شود، فرسایش خندقی است. بخش جنوب و جنوب شرقی حوضه شور مُهر تحت تاثیر فرسایش خندقی قرار گرفته است، از پیامدهای این نوع فرسایش می توان به بهم خوردن تعادل اکولوژیک منطقه و به خطر افتادن منابع زیستی اشاره کرد؛ به همین دلیل، مطالعه در مورد این پدیده در منطقه ضروری است. هدف از این پژوهش، ارزیابی تاثیر خصوصیات فیزیکی و شیمیایی خاک بر ایجاد و گسترش خندق در منطقه است. در این بررسی با بازدیدهای میدانی، ابتدا 42 خندق در منطقه شناسایی و با دستگاه (gps) موقعیت آنها ثبت شد. سپس به صورت تصادفی، پانزده نمونه خاک در مناطق خندقی و پنج نمونه در مناطق غیر خندقی در عمق 30-0 سانتی متر تهیه و در آزمایشگاه بررسی شد. از آزمون مقایسه میانگین دو جامعه آماری (t) در زبان برنامه نویسی r، برای بررسی نقش خصوصیات فیزیکی و شیمیایی در ایجاد و گسترش فرسایش خندقی استفاده شد. نتایج نشان داد که در بین خصوصیات فیزیکی خاک، درصد شن (0.001) اختلاف معنی داری در سطح پنج درصد در دو منطقه مورد بررسی داشت. همچنین در بین خصوصیات شیمیایی خاک، متغیرهای ph (0.0001779)، نسبت جذب سدیم (0.00995)، مواد خنثی شونده (0.01571)، سدیم محلول (0.02378)، منیزیم (0.03456) و پتاسیم (0.04593) توانستند اثر معنی داری در بین دو منطقه از خود نشان دهند و در نتیجه، در ایجاد فرسایش خندقی نقش موثرتری داشت.

analysis of soil properties in the formation and spread of gully erosion using r software in the shoor river (mehran) watershed of mohr city

1- introductiongully erosion is considered as a form of land degradation. occurrence of this type of erosion causes large areas of upper soil to be lost by gully and become potentially unusable, which ultimately leads to desertification of the area. environmental parameters that affect the potential of gully erosion include hydrological, climatic, topographic, ecological, geological and anthropological factors which have different consequences. shoor river watershed in mohr city (fars province), especially the sloping plains located in the east of the basin to chaho village, due to high fluctuations in rainfall in different periods, weakness or lack of vegetation and also due to human interventions such as overgrazing, plowing direction slope, movement of vehicles and agricultural machinery in fields and pastures, etc. is severely affected by gully erosion. the purpose of this study was to investigate the effect of physical and chemical properties of soil on the creation and spread of gully erosion in this region and to provide appropriate solutions to prevent the spread of this type of erosion in the region.2- methodologyin order to identify the natural features of the basin and collect theoretical issues, the basic topographic maps (scale 1: 25000) of the national mapping organization and the geological map (scale 1: 100000) of the geological survey of iran were used. digital elevation model (dem) and land use map were extracted from landsat 8 images in 30 by 30 dimensions. the mentioned maps were prepared in arcgis10.5 environment. then, by performing field visits, 15 gullies were selected and their location was recorded by gps, and then some soil samples were taken from each gully from a depth of 0-30 cm. in the continuation of the work, 5 points were selected from non-gully areas as areas that were not affected by ditch erosion and their location was recorded and soil samples were taken from a depth of 0-30 cm. soil samples collected from the basin were examined in the laboratory for physical and chemical properties. then r software was used for statistical analysis.3- results the results showed that there was no discrepancy between the studied variables in the two groups (a: gully areas, b: non-gully areas). the results of the physical properties showed that the normality of sand data in the gully and non-gully areas is confirmed by 0.880 and 0.484, respectively. also, the value of leven test (0.499) expresses the homogeneity of variance between the data of the two groups. finally, sand analysis was able to show a significant difference between the two areas (i.e., 0.001). the results of chemical properties showed that the variables ph (0.0001779), sar (0.00995), t.n.v (0.01571), na (0.02378), mg (0.0456, c and kc(0.04593) were able to show significant differences between the two regions. however, there is no significant difference between o.c (0.4666) and ec (0.2671).4- discussion & conclusions  geological conditions of the region showed that most of the gullies in quaternary sediments (young alluvial barracks and clay and silty zones), due to the presence of fine-grained sediments that have a weak and unstructured shape and the presence of soluble salts (gypsum, calcium and magnesium) in geological formations, have caused the formation of moat erosion. in the outlet part of the basin (south and southeast), a gully has been formed with a decreasing altitude, while in other parts of the basin despite the low height, no gully has been formed due to shallow soil depth or lack of upstream basin less sensitivity to gully erosion. also, the gully in the area were generally formed in poor pastures. factors of gully formation and expansion in the study area can be considered as climatic, hydrological, and topographic factors, plus soil characteristics, geological features, human factors, etc. among these factors, soil properties were investigated according to the purpose of the study. the results showed that among the physical properties of soil, only the percentage of sand has significant differences between gully and non-gully areas. regarding the effect of soil chemical properties on the formation and spread of gully erosion, it can be said that the variables of ph, sar, t.n.v, na, mg and k have played an effective role in this regard. according to the results of the present research, it is suggested to create and improve the native vegetation of the region, and due to the high production of surface runoff after sudden and heavy rains, it is possible to collect soil from the soil dams at the end of the gullies. finally, it is suggested to do more comprehensive research to study the gullies formed in the region by investigating the role of other influential factors and using random forest (rf) method in r software.