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بررسی نقش تغییر کاربری اراضی بر برخی از خصوصیات فیزیکی، شیمیایی و فرسایش‌پذیری خاک | ||
| پژوهش های جغرافیای طبیعی | ||
| مقاله 8، دوره 42، شماره 4 - شماره پیاپی 406595، اسفند 1389، صفحه 111-123 اصل مقاله (515.93 K) | ||
| نویسندگان | ||
| کریم سلیمانی1؛ علی آزموده2 | ||
| 1دانشیار مرکز GIS، دانشگاه علوم کشاورزی و منابع طبیعی ساری | ||
| 2دانشجوی ارشد آبخیزداری، دانشگاه علوم کشاورزی و منابع طبیعی ساری | ||
| چکیده | ||
| تغییر کاربری جنگل به اراضی کشاورزی، عموماً تأثیر جدّی بر میزان ماده آلی و دیگر ویژگی‌های فیزیکی و شیمیایی خاک می‌گذارد. این پژوهش با هدف بررسی نقش تغییر کاربری جنگل بر برخی از خصوصیات فیزیکی و شیمیایی خاک و در ادامه شناخت شماری از متغیرهای مؤثر خاک بر شاخص فرسایش‌پذیری در بخشی از حوضه آبخیز برنجستانک صورت گرفته است. بدین منظور سه کاربری جنگل، زراعت دیم (گندم) و باغ مورد بررسی قرار گرفت. نمونه‌های خاک از دو لایه سطحی 10-0 و 20-10 سانتی‌متر در قالب طرح بلوک کاملاً تصادفی برداشته و مقایسه شد. نتایج نشان از آن داشتند که میزان ماده آلی در اراضی زراعی و باغ، به ترتیب 24/44 و 45/45 درصد در لایه 10-0 سانتی‌متر، و 69/42 و 43 درصد در لایه 20-10 سانتی‌متر کمتر از اراضی جنگلی بوده است. حداکثر نیتروژن کل در لایه 10-0 سانتی‌متر در کاربری جنگل به میزان 303/0 درصد و حداقل آن در لایه 20-10 سانتی‌متر در اراضی باغ به میزان 190/0 درصد مشاهده شد که کاهشی معادل با 32/37 درصد را نشان می‌دهد. وزن مخصوص ظاهری و اسیدیته خاک طی تغییر کاربری جنگل افزایش یافت. این در حالی است که تغییر کاربری جنگل به اراضی زراعی و باغ تأثیر مشخص و معنی‌داری بر درصد ذرات رس و سیلت نداشت و تنها در لایه 10-0 سانتی‌متر تفاوت معنی‌داری از لحاظ درصد ذرات شن مشاهده شد. نتایج نشان داد که فرسایش‌پذیری خاک به دلیل کاهش پوشش گیاهی پایا، ماده آلی خاک، تخریب ساختمان خاک و پایداری خاکدانه‌ها طی تغییر کاربری جنگل، افزایشی حدود دو برابر داشته است. همچنین متغیرهای رس، ماده آلی و نیتروژن کل دارای همبستگی معنی‌دار منفی؛ و در مقابل، درصد سیلت و شن ریز نیز دارای ارتباط معنی‌دار مثبت با میزان فرسایش‌پذیری‌اند. | ||
| کلیدواژه‌ها | ||
| تغییر کاربری اراضی؛ حوضه برنجستانک؛ خاک؛ فرسایش‌پذیری؛ ماده آلی. | ||
| عنوان مقاله [English] | ||
| Investigation of Land Use Change Effects on some Physical and Chemical Properties, as well as the Soil Erodibility | ||
| نویسندگان [English] | ||
| Karim Solaimani1؛ A. Azmoudeh2 | ||
| چکیده [English] | ||
| Introduction Different land-uses are being changed every day by the man, all over the world. Nowadays the increase of population and request for agricultural products causes natural vegetation such as transferring forests to farmlands. Rapid population growth in northern Iran requires additional farmlands for food production leading to clear cutting of forests and converting to the agricultural land. Land-use changes, mainly through conversion of natural vegetation may influence many natural phenomena and ecological processes and leading to a remarkable change in soil properties. There is a considerable concern that land-use changes can lead to an alteration of the soil organic carbon. Conversion of natural vegetation to agricultural land uses leads to a significant decrease of soil organic matter (SOM) content and conversely, reversion of cultivated land to natural vegetation can reliably replenish SOM and return lost soil carbon via increased soil carbon storage. Understanding the effects of land use and land cover changes on soil properties include many implications for devising land management strategies for identifying sustainable practices in each region with the intention of land degradation, sustainable development of agriculture and environmental protection. Therefore this study has been conducted to assess the impact of conversion of native forests into cultivated land (Wheat) and garden (Orange) on some soil properties and soil erodibility and investigate the effects of some soil properties on soil erodibility in northern Iran. Materials and Methods The study has been conducted in the Berenjestanak watershed of Mazandaran. The altitudinal range of the study site is between 153 and 777.2 m above sea level with a mean annual precipitation of 905 mm. Most precipitations are during the winter and spring seasons (November–May), and means annual temperature ranges from 16°C. Soil samples were taken at two depth of 0-10 and 10- 20 cm to characterize the physical and chemical properties, in particular soil texture, soil organic carbon, total N, bulk density, PH and EC. Soil erodibility measured by Wischmeier method. One-way Analysis of Variance (ANOVA) (SPSS 15) was used to compare the effects of land- use changes to selected physical and chemical properties and soil erodibility. The DUNCAN procedure was conducted to compare soil properties mean at P < 0.05. Pearson correlation coefficients were performed for response and explanatory relationships between soil erodibility with selected soil properties in three given land-uses. Results and Discussion The Conclusions show that land-use changes lead to significant changes in soil properties and its erodibility. Soils under three land-use types in the north of Iran have been shown to differ markedly in their contents of soil organic carbon, total N, bulk density, sand, and PH and soil erodibility. The organic carbon and total nitrogen content of the natural forest situation were significantly higher than the organic carbon and total nitrogen content of the garden and cultivated land. These results confirm the conclusions from several other experiments that have also shown a decrease in soil organic carbon and total nitrogen after cultivation. The bulk density of the soils was at the lowest level in areas under natural forest and the highest in cultivated areas of wheat. The result showed that land-use affected the measured content of sand in 0-10 cm of soil, but did not have a significant interactive effect on clay and silt contents. Also reduction of the permanent vegetation, loss of SOM, destruction of soil structure and the soil stability in the process of these alterations on the forest areas were caused increasing the soil erodibility 2 times more than the forest conditions soil. The correlation matrix revealed that soil organic carbon, total N and clay showed negative correlation with soil erodiblity, while silt and fine sand showed positive correlation whit soil erodibility. Conclusion Overall results indicated that conversion of natural forest and cultivation in the given area caused a degraded the soil properties, great decrease in soil quality and made the surface too sensitive for soil erosion. In conclusion, when these systems are converted for agriculture without proper practices of securing organic matter and soil stability, they are easily threatened. Therefore, conservation and good management after natural forest removal and reforesting can go some way to provide a solution to the problems of soil degradation, nutrient depletion as well as improving the soil quality | ||
| کلیدواژه‌ها [English] | ||
| Brenjestanak basin, Erodibility organic material, land use change, soil | ||
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