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پژوهش های فرسایش محیطی، جلد ۱۴، شماره ۲، صفحات ۱۰۶-۱۲۵
عنوان فارسی تحلیل زمین آماری مقاومت‌های فروروی و برشی خاک در منطقه فندقلوی اردبیل
چکیده فارسی مقاله
هدف از این پژوهش مطالعه تغییرات مکانی مقاومت فروروی (PR) و مقاومت برشی خاک (SS) در اراضی شیبدار منطقه فندقلوی اردبیل بود. نمونه­های خاک دست­خورده و دست­نخورده از سه کاربری جنگلی (20 نمونه)، مرتعی (23 نمونه) و زراعی (37 نمونه) به­هم چسبیده (ha 15) برای تعیین برخی متغیرهای فیزیکی و شیمیایی به­صورت شبکه­های تقریباً منظم m 50×50 از منطقه مذکور در تابستان 1402 برداشته ­شدند. متغیرهای PR و SS به­صورت درجا در محل به­ترتیب با استفاده از دستگاه­های فروسنج مخروطی عقربه­ای و پره برشی تعیین شد و همزمان رطوبت خاک مزرعه (FWC) در نمونه­های دست­نخورده اندازه­گیری شد. همچنین برخی ویژگی­های خاک مانند کربن آلی، شن، سیلت، رس، جرم مخصوص ظاهری و حقیقی و تخلخل کل تعیین گردید. از روش­های درون­یابی کریجینگ معمولی (OK) و وزن­دهی عکس فاصله (IDW) برای بررسی زمین­آماری متغیرهای خاک استفاده شد. همبستگی­های منفی و معنی­دار بین PR با سیلت و FWC و مثبت و معنی­دار بین SS با شن و کربن آلی مشاهده شد. متغیر PR دارای بیشترین تغییرپذیری (CV= 58.3 %) در اراضی مرتعی و متغیر سیلت دارای کمترین دامنه تأثیر (m 636) نسبت به سایر متغیرهای خاک بود لذا توصیه می­شود در مطالعات بعدی، فواصل نمونه­برداری خاک به­جای 50 متر، 636 متر در نظر گرفته شود. مدل نیم­تغییرنمای گوسی و کروی با وابستگی­ مکانی قوی و متوسط به­ترتیب برای PR و SS به­دست آمد. براساس آماره­های ریشه میانگین مربعات خطا (RMSE) و ضریب تطابق (CCC)، روش OK به­علت داشتن RMSE کمتر و CCC بیشتر در مقایسه با روش IDW دارای صحت بالاتری در برآورد PR بود، ولی در درون­یابی SS، روش IDW در مقایسه با روش OK دقیق­تر عمل نمود. نقشه تغییرات مکانی نشان داد بیشترین مقادیر PR و SS در کاربری مرتعی و کمترین مقادیر آن­ها در کاربری زراعی منطقه مورد مطالعه وجود داشت.
کلیدواژه‌های فارسی مقاله اراضی شیبدار، تغییرات مکانی، زمین آمار، مقاومت خاک، نیم‌تغییرنما.
عنوان انگلیسی Geostatistical Analysis of Soil Penetration Resistance and Shear Strength in Fandoghloo Region of Ardabil
چکیده انگلیسی مقاله 1- Introduction
Soil penetration resistance (PR) and soil shear strength (SS) are used to evaluate soil erodibility. Some soil properties such sand, silt, clay, bulk and particle density, total porosity, organic carbon and CaCO3 and also some land characteristics such as percentage and direction of slope, altitude, type and density of vegetation can affect SS and PR. For example, PR values exceed 2.5 MPa, while root elongation is significantly restricted. Most of soil properties have temporal and spatial variabilities. Therefore, it is necessary to use geostatistical methods to simultaneously use quantitative information and geographic location of variables. The forest, range and cultivated soils of Fandoghloo region of Ardabil are located in sloping lands and are subject to erosion. Therefore, it is necessary to know the state of spatial variability of soil SS and PR as two important indicators affected by compaction and also effective on soil erosion in the mentioned area. The main objectives of this research were: 1) Investigating the spatial variabilities and drawing maps of soil SS and PR in forest, range and cultivated lands of Fandoghloo region of Ardabil,  2) Investigating the correlations between soil SS and PR with other soil characteristics in the study area,  3) Determining semivariogram parameters such as semivariogram models, spatial dependence classes and effective range for soil variables, 4) Comparison of the accuracy of geostatistical methods (ordinary kriging (OK) and  inverse distance weighting (IDW)) in the interpolation of SS and PR.

2- Methodology
  This study was conducted in the forest, range and cultivated lands of Fandoghloo region of Ardabil located at the 25 km of Ardabil city, northwest of Iran (48° 32ʹ 45ʺ to 48° 33ʹ 5ʺ E and 38° 24ʹ 10ʺ to 38° 24ʹ 25ʺ N) at summer 2023. Totally, 80 geo-referenced samples were taken from 0-10 cm soil depth with 50×50 m intervals (15 ha) in cultivated (n=37), range (n=23) and forest (n=20) land uses. Sand, silt, clay, organic carbon (OC) and particle density (PD) were measured in the disturbed soil samples. Bulk density (BD) and field water content (FWC) were measured in the undisturbed soil samples taken by steal cylinders with 5 cm diameter and height. Total porosity was calculated using BD and PD. Soil penetration resistance (PR) was directly measured in the field at three replicates using a cone penetrometer. Soil shear strength (SS) was obtained using shear vane in saturation condition in the field at three replicates. The best fitted semivariograms model (Gaussian, spherical and exponential) was chosen by considering the minimum residual sum of square (RSS) and maximum determination coefficient (R2) for soil variables. Ordinary Kriging (OK) and inverse distance weighting (IDW) interpolation methods were used to analyze spatial variability of soil SS and PR. Spatial distribution maps of soil variables were provided by Arc GIS software. Normality test of data by Kolmogorov–Smirnov test and Pearson correlations were done using SPSS software. Figures were prepared using Excel software. The accuracy of OK and IDW methods in estimating soil SS and PR was evaluated by mean error (ME), mean absolute error (MAE), root mean square error (RMSE) and concordance correlation coefficient (CCC) criteria. The CCC indicates the degree to which pairs of the measured and estimated parameter value fall on the 45° line through the origin.

3- Results & Discussion
According to the results of coefficient of variation (CV) from the study area, the most variable (CV=58.3 %) soil indicator was PR in range land use, whereas the least variable (CV= 3.95 %) was PD in cultivated land use. The Pearson correlation coefficient (r value) indicated that there are significant correlations between OC with sand (r=0.59) and FWC (r=0.78) and between PR with SS (r=0.31). Also, significant correlations were found between PR with FWC (r=-0.45) and silt (r=-0.36) and between SS with OC (r=0.38), sand (r=0.48) and silt (r=-0.34). The spatial dependency classes of soil variables were determined according to the ratio of nugget variance to sill expressed in percentages: If the ratio was >25% and <75%, the variable was considered moderately spatially dependent; if the ratio was >75%, variable was considered weakly spatially dependent; and if the ratio was <25%, the variable was considered strongly spatially dependent. The strong spatial dependences with the effective ranges of 752 m was found for PR. The medium spatial dependences with the effective ranges of 787 m was obtained for SS. The silt and FWC variables had the least (636 m) and the highest (2282 m) effective range, respectively. The range of influence indicates the limit distance at which a sample point has influence over another points, that is, the maximum distance for correlation between two sampling point. The models of fitted semivariograms were Gaussian for PR and spherical for SS. The high values of CCC and low values of RMSE values indicated the more precision and high accuracy of OK compared with IDW interpolation method in estimating PR in the studied area. According to the RMSE and CCC values, IDW was better than OK to predict SS. Generally, the spatial maps showed that the highest values ​​of soil PR were observed in range land use and the lowest values ​​of soil SS were observed in cultivated land use of the study area.
4- Conclusions
Results showed that PR negatively related to the silt and FWC. Also, SS negatively related to the silt and positively related to the sand and OC. The strong spatial dependency was found for PR and medium spatial dependency was determined for SS in the studied area. The silt revealed the smallest effective range (636 m) among the studied variables. As a suggestion, for subsequent study, soil sampling distance could be taken as 636 m instead of 50 m in order to save time and minimize cost.

 
کلیدواژه‌های انگلیسی مقاله Geostatistics, Spatial variability, Soil resistance, Semivariogram, Sloped lands.
نویسندگان مقاله شکراله اصغری | Shokrollah Asghari
Department of Soil Sciences and Engineering, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran
گروه علوم و مهندسی خاک، دانشکده کشاورزی و منابع طبیعی، دانشگاه محقق اردبیلی، اردبیل

حسین شهاب آرخازلو | Hossain Shahab Arkhazloo
Department of Soil Sciences and Engineering, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran
گروه علوم و مهندسی خاک، دانشکده کشاورزی و منابع طبیعی، دانشگاه محقق اردبیلی، اردبیل

مهسا حسنپور کاشانی | Mahsa Hasanpour Kashani
Department of Water Engineering, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran
گروه مهندسی آب، دانشکده کشاورزی و منابع طبیعی، دانشگاه محقق اردبیلی، اردبیل

نشانی اینترنتی http://magazine.hormozgan.ac.ir/browse.php?a_code=A-10-671-3&slc_lang=fa&sid=1
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نوع مقاله منتشر شده مستخرج از پایان‌نامه / رساله / طرح پژوهشی
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