نوع مقاله : مقاله پژوهشی

نویسنده

• نازنین خاکی پور

گروه علوم و مهندسی خاک، واحد سوادکوه، دانشگاه آزاد اسلامی، سوادکوه، ایران

چکیده

تغییر کاربری اراضی یکی از مهم‌ترین معضلات کنونی کشور ما به ویژه در اراضی جنگل‌های هیرکانی شمال کشور است. در این مطالعه سعی شده است تاثیرات این تغییرات در درازمدت ( 50 ساله) بر برخی شاخص‌های فیزیکی، شیمیایی و زیستی خاک مورد ارزیابی قرار گیرد. بدین منظور سه کاربری جنگل طبیعی، چایکاری و شالیکاری تعیین و در هر کاربری 10 نقطه با شرایط یکسان از نظر شیب، درصد پوشش گیاهی و مدیریت انتخاب شدند و تجزیه‌های مختلف روی نمونه‌ها صورت گرفت . نتایج آماری در این مطالعه نشان داد، بر اثر تغییر کاربری اراضی از جنگل به چایکاری و شالیکاری میزان کربن آلی کاهش و در مقابل میزان pH و کربنات کلسیم افزایش یافته است. بر اثر تغییر کاربری اراضی جنگلی به دوکاربری دیگر به طور معنی‌داری شاخص‌های پایداری خاکدانه ها (MWD، GMD و WSA) کاهش یافته است و به تبع آن جرم مخصوص ظاهری خاک افزایش یافته است. این افزایش یک رخداد مخرب است، زیرا حاکی از تخریب ساختمان خاک است. میزان MWD در جنگل معادل 95/1 میلی متر، در اراضی چایکاری 2/1 میلی متر و در اراضی شالیکاری معادل 45/0 میلی‌متر متغیر بود. میزان کربن آلی ذره ای به عنوان یکی از شاخص‌های کیفیت خاک در اراضی جنگلی در حداکثر مقدار مشاهده شد. این تغییر علاوه بر کاهش مواد آلی ناشی از تردد بیش از حد ماشین‌آلات در اراضی شالیزاری نیز می باشد. نتایج نشان داد که میانگین تنفس میکروبی به عنوان شاخص زیستی خاک در جنگل طبیعی معادل 300 میلی گرم در روز در هر گرم خاک بوده و در دو کاربری چایکاری و شالیکاری به ترتیب معادل 200 و 120 میلی گرم بر گرم خاک در روز محاسبه شد که در هر سه کاربری اختلاف معنی‌داری (P<0.05) نشان داد. در مجموع نتایج نشان داد که تغییر کاربری اراضی در منطقه مورد مطالعه باعث تخریب اراضی و کاهش تقلیل کیفیت خاک شده است.

کلیدواژه‌ها

• تغییرکاربری اراضی
• کیفیت خاک
• شاخص های کیفیت
• تخریب اراضی
• تنفس میکروبی

موضوعات

• ارزیابی و تناسب اراضی

عنوان مقاله [English]

Variability of some soil quality indicators under different land uses in a part of Lahijan region, Gilan province

نویسنده [English]

• Nazanin Khakipour

Department of Soil Science, Savadkooh branch, Islamic Azad University, Savadkooh, Iran

چکیده [English]

Introduction
Soil is a dynamic natural system and interface between land, air, water, and life, which performs vital services for human sustenance. The increasing population growth has led to the excessive use of this natural resource to provide food, clothing and other human needs. This has led farmers in different parts of the world to improper exploitation of inferior and marginal lands such as pastures and forests located on sloping lands. However, on the one hand, these lands have low potential and on the other hand, they have a high potential for erosion. Soil quality is usually introduced as the ability of the soil to interact with the ecosystem maintain the productivity of the quality of different parts of the environment and thus improve the health of plants, animals and humans. The quality of soil and its importance for the development of sustainable agriculture are more important nowadays. Land use change is one of the most important current problems of our country, especially in the Hyrcanian forest lands in the north of the Iran. The objectives of this study were to evaluate the effects of land use change on some soil quality indicators in north of Iran.
Methods and Materials
A part area in the south of Lahijan was selected including 3 land uses: Natural Forest (NF), Tea plantation (TP) and paddy rice (PR) cultivation. In each land use 10 soil samples were collected at 0-20 cm depth and transferred to the laboratory. Undisturbed soils samples by core was taken for measurement of bulk density. A part of sample passed through the 4 mm sieve for measurement of aggregate stability and three indices comprised mean weight diameter: MWD, geometric mean diameter: GMD and water stable aggregates: WSA were calculated. Other soil properties such as pH, Calcium carbonate equivalent (CCE), soil organic matter (SOM), particulate organic carbon (POC), and soil respiration also measured.
Results and Discussion
The statistical results in this study showed that due to the change of land use from forest to tea and rice cultivation, the amount of organic carbon decreased, while the amount of pH and calcium carbonate increased. As a result of changing the use of forest land to other two land uses, the indicators of stability of soil aggregates (MWD, GMD and WSA) have significantly decreased, and as a result, the bulk density of the soil has increased. The amount of MWD was 1.95 mm in the forest, 1.2 mm in the tea plantation, and 0.45 mm in the rice cultivation. The amount of particulate organic carbon as one of the indicators of soil quality in forest lands was observed in the maximum amount. In addition to the reduction of particulate organic matter, this change is also caused by the excessive traffic of machines. Soil microbial respiration was analyzed as a soil biological indicator. The results showed that the average microbial respiration in the natural forest was equal to 300 mg C/ day.g soil, and in the two other land uses of tea and rice cultivation, it was calculated as 200 and 120 mg C/ day.g soil, respectively. Positive and significant relationship between SOM and MWD confirmed that soil organic matter had high contribution for soil aggregate formation and its stability.
Conclusion
This research was conducted to investigate the impacts of land use changes in the north of Iran in Gilan province on some soil quality indicators. The results of this research showed that the soil’s chemical, physical, and biological characteristics have shown significant differences due to land use change. In forest soils, the highest amount of organic carbon, and the lowest amount of pH was observed, which is due to the high accumulation of organic matter and high leaching of cations. Due to the degradation of organic carbon in the other two uses, the bulk density and aggregate stability indicators have decreased. The intense cultivation operations in the other two uses, especially in the paddy fields, have destroyed the soil structure. Also, more organic carbon in forest soils has led to more microbial respiration. In total, all soil quality indicators have decreased with the change in land use in the study area. Therefore, land conversion and especially deforestation in the studied region should be avoided. In total, the results showed that land use change in the study area has caused land degradation and reduced the soil quality and soil health indicators, and it is necessary to consider it in land use planning, land improvement, and sustainable land management.

کلیدواژه‌ها [English]

• Land use change
• Soil quality
• Soil quality indicators
• Land degradation
• Soil respiration