نسبت لایه‌بندی ماده آلی خاک و پایداری خاکدانه‌ها تحت تأثیر آتش‌سوزی در مراتع نیمه استپی چهارمحال و بختیاری

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجوی سابق کارشناسی ارشد، گروه خاکشناسی دانشگاه شهرکرد

2 استاد گروه خاکشناسی دانشگاه شهرکرد

3 استادیار گروه مرتع و آبخیزداری دانشکده منابع طبیعی و علوم زمین دانشگاه شهرکرد

چکیده

نسبت لایه‌بندیماده آلی خاک و پایداری خاکدانه­ها را می‌توان به عنوان شاخص‌های کیفیت خاک تحت شرایط مختلف از جمله آتش­سوزی پوشش گیاهی مراتع محسوب کرد. هدف از این پژوهش، بررسی تأثیر آتش‌سوزی پوشش گیاهی بر نسبت لایه­بندی ماده آلی خاک، پایداری خاکدانه­ها و توزیع ماده آلی در خاکدانه­های ریز و درشت در مراتع نیمه استپی کرسنک واقع در استان چهارمحال و بختیاری بود. بدین‌ منظور، مراتعی با تاریخچه‌ی آتش‌سوزی متفاوت که طی سال‌های 1387، 1388 و 1389 به ترتیب 3، 2 و 1 سال پیش از مطالعه دچار آتش‌سوزی شده بودند، انتخاب گردید. نمونه­برداری از دو عمق سطحی (10-0 سانتی­متر) و زیر سطحی (25-15 سانتی­متر)، مربوط به هر نقطه دچار آتش­سوزی و نقطه مجاور آن که دچار آتش نشده بود (شاهد) در 9 تکرار (مجموعاً 108 نمونه) انجام شد. سپس تأثیر آتش‌سوزی بر نسبت لایه­بندی ویژگی­های ذکر شده با آزمون t مستقل مورد بررسی قرار گرفت. نتایج نشان داد ماده آلی خاک و میانگین وزنی قطر خاکدانه‌ها (MWD) در نمونه‌های سطحی تیمارهای 1 و 2 سال پس از آتش‌سوزی در مقایسه با شاهد به صورت معنی­دار کاهش یافت. همچنین، ماده آلی ذره‌ای (POM) در نمونه‌های سطحی در تمام سال‌های مورد مطالعه در مناطق سوخته شده به طور معنی­داری کمتر از مناطق شاهد مجاور بود. تأثیر آتش‌سوزی بر نسبت لایه‌بندی ماده آلی خاک در تیمارهای 1 و 2 سال پس از آتش­سوزی در مقایسه با مناطق شاهد معنی‌دار بوده و به ترتیب 26 و 22 درصد کاهش یافت. ماده آلی بخش درشت در لایه سطحی و زیر سطحی تیمار 1 سال پس از آتش‌سوزی در مقایسه با شاهد کاهش معنی­دار داشت. در حالی که، ماده آلی بخش ریز در لایه زیر سطحی تیمار 1 سال پس از آتش‌سوزی نسبت به شاهد افزایش معنی­دار نشان داد. یافته‌های این پژوهش نشان داد که تأثیر آتش‌سوزی بر ویژگی‌های فیزیکی و شیمیایی خاک، در لایه سطحی به دلیل شدت­ بیشتر آتش­سوزی، نسبت به لایه زیر سطحی بیشتر بود. افزون بر آن، آتش­سوزی باعث کاهش ماده آلی خاک و همچنین پایداری خاکدانه­ها و در نتیجه افت (تنزل) کیفیت خاک اراضی مرتعی مورد مطالعه گردید. 

کلیدواژه‌ها


عنوان مقاله [English]

Stratification Ratio of Soil Organic Matter and Aggregate Stability under Fire in Semi-steppe Rangelands in Chaharmahal and akhtiari

نویسندگان [English]

  • J. Heidary 1
  • Sh. Ghorbani Dashtaki 2
  • F. Raiesi 2
  • P. Tahmasebi 3
1 Former MSc Student, Shahrekord University. Soil Science Department
2 Assistant Professor, Shahrekord University. Soil Science Department
3 Assistant Professor, Shahrekord University. Rangeland and Watershed Management Department, Faculty of Natural Resource and Earth Science
چکیده [English]

Stratification ratio of soil organic matter and aggregate stability are considered as indicators of soil quality under different conditions such as burning rangeland vegetation. The objective of this study was toinvestigate the impact of fire on stratification ratio of soil organic matter and aggregate stability and distribution of organic matter in two macro and micro fractions in semi-steppe rangeland of Karsanak region in Chaharmahal and Bakhtiari province. Several sites which were affected by fire three, two, and one years before this study (i.e. 2008, 2009, and 2010, respectively) were chosen. Since the soil samples were taken from two depths (0-10 cm and 15-25 cm) of each site with 9 replications, the numbers of soil samples for laboratoryanalysis were 108. Independent t-test (P= 5%) was used to assess the difference between the measured properties at the burned and control sites. The results showed that the soil organic matter and mean weight diameter of aggregates (MWD) in the surface layer decreased significantly in 1 and 2 years after fire. Particulate organic matter (POM) significantly decreased in surface layer of the burned areas compared with the control areas. The effects of fire on stratification ratio of soil organic matter in 1- and 2-years after fire were significant compared with control areas, and stratification of soil organic matter decreased 26% and 22 percent in 1 and 2 years after fire, respectively.Stratification ratio of aggregate stability was lower in all burned areas compared with control areas, but the differences were not significant. Macro organic matter of both surface and subsurface layers in 1 year after fire was significantly reduced compared with the control,while, micro organic matter of subsurface layer showed significant increase. The study results showed that theeffect of fire on physical and chemical soil properties in the surface layer were more than subsurface layer, because of higher-severity fire in surface layer. Furthermore, due to reduction of organic matter and aggregate stability after fire, rangeland soil quality decreased.

کلیدواژه‌ها [English]

  • Carbon Cycle
  • Soil structure
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