ارزیابی تنوع زیستی کشاورزی در بوم‏نظام‏های باغچه‏ای برخی مناطق استان خراسان رضوی

امروزه ویژگی‏هایی نظیر سطوح بالای تنوع زیستی کشاورزی،کارایی بالای چرخه مواد غذایی و همچنین کارکردهای متنوع بوم‌شناختی و اقتصادی اجتماعی، باغچه‏ها را به الگویی مناسب برای دستیابی به مدلی پایدار در تولید محصولات کشاورزی تبدیل کرده است. با توجه به اینکه تاکنون مطالعات کمتری در رابطه با این ویژگی‏ها در باغچه‏های مناطق خشک و نیمه خشک انجام شده است، هدف از انجام این مطالعه، بررسی ساختار تنوع‏ زیستی‏کشاورزی با تاکید بر تنوع کارکردی و شناخت عوامل موثر بر آن‌ها در باغچه‏های استان خراسان رضوی (شهرستان‏های مشهد، قوچان و نیشابور) بود که داده‏ها و اطلاعات مورد نیاز آن از طریق مطالعات میدانی و تکمیل پرسش‌نامه در سال 1391 استخراج گردید. نتایج نشان داد که شهرستان نیشابور با داشتن شاخص تنوع زیستی شانون 1.88 بالاترین سطح تنوع گونه‏ای را دارا بود، این در حالی است که بالاترین میزان تنوع کارکردی در باغچه‏های شهرستان قوچان مشاهده شد. همچنین نتایج نشان داد که بیش از 79 درصد از تغییرات شاخص تنوع شانون ناشی از تغییر شاخص غنای گونه‏ای می‏باشد، این در حالی است که نتایج حاصل از برازش مدل خطی چندگانه با استفاده از رگرسیون گام‏به‏گام نشان داد که تغییرات صفات مختلفی همچون شاخص غنای گونه‏ای، مساحت منزل و جمعیت خانوار، 84 درصد از تغییرات شاخص تنوع کارکردی شانون را موجب می‏شوند. باغچه‏های شهرستان‏های مشهد، قوچان و نیشابور به‌طور میانگین با 8.1 تن ترسیب کربن در هکتار نقش مهمی در تعدیل شرایط حاصل از افزایش غلظت گاز دی‏اکسیدکربن بر عهده داشتند و مشخص شد که با فاصله گرفتن از مسیرهای آسفالته میزان ترسیب کربن (کیلوگرم در مترمربع) توسط گونه‏های درختی در باغچه‏ها کاهش می‏یابد.

Assessing Agrobiodiversity in Home Garden Ecosystems of some Regions in Khorasan Razavi Province

Introduction  Characteristics such as the high levels of agrobiodiversity, the efficiency of the nutrition, and also variety in ecological and socioeconomic functions have altered home gardens into the appropriate model for achieving a sustainable agricultural system. So far, fewer studies in relation to these features have been done in home gardens of dry and semiarid regions. Protection of diversity with a particular emphasis on agricultural biodiversity is fundamental to sustainable development in food production and hence food security. Expansion of industrial agriculture in the form of monoculture for the purpose of maximizing the yield with the aid of highyielding varieties and intensive use of inputs has hampered the ecological functions of food production systems worldwide. This problem can be overcome by the application of a wide array of ecological agriculture practices, of which food production in home gardens is only one of them. This environmentally sound practice is an old system of land use almost in all parts of the world with a wide range of dimensions. A combination of different plants, from herbs to trees and in cases with poultry and other lowweight animals, provides a complex sustainable system of food production. This type of subsistence food production is based on local knowledge and normally is part of the residential area or, to the, low input. Food produced in this system is consumed locally, and women are the main element in both production and marketing. Exchanges of experience and knowledge, seed, and also tools, and labors are very common in neighboring communities. The purpose of the present study was to investigate the agrobiodiversity of home gardens in an arid environment of Khorasan Razavi Province.Materials and MethodsData collection for this study was based on the fieldwork with the distribution of questioners. For this purpose, 17 villages from 3 highly populated counties of Mashhad/ Quchan and Nyshabour were selected, and 164 questioners were distributed with a facetoface procedure. After the collection and validation of data, only 136 questionnaires were selected, data were extracted, and finally, an analysis was carried out. Afterward, the Shannon biodiversity index, Simpson index, and species richness were calculated. The amount of carbon sequestered was also calculated by an equation referred to in the literature. For the calculation of biodiversity indices, the area under cultivation of each species was used. Based on the available previous studies, seven basic functions for home gardens were assigned.Results and DiscussionResults showed the highest Shannon index of species diversity equal to 1.88 for the county of Neishabour; however, the highest functional diversity was found in Quchan. More the 79 percent of changes in the Shannon index are caused by changes in species richness. Stepwise regression analysis revealed that changes in species richness, home area, and household population were the factors that caused 84 percent of changes in functional diversity. Home gardens in these three counties sequester 8.1 tons of carbon dioxide per hectare, and this amount showed a decreasing trend where the distance from the vehicle roads was increased.ConclusionIt was revealed that with taking distance from the main roads, the amount of carbon dioxide (kg per m2) decreased by tree species.AcknowledgmentsThe authors acknowledge the financial support of this project (grant number 2/19719) by the Vice President for Research and Technology, Ferdowsi University of Mashhad, Iran.