بررسي تنوع زيستي محصولات زراعي و باغي استان اصفهان

Assessing Biodiversity of Agronomical and Horticultural Productions of Isfahan Province

شاخص‏هاي تنوع زيستي ابزاري نيرومند براي ارزيابي پايداري نظام هاي كشاورزي محسوب مي شوند. در اين تحقيق كه به منظور ارزيابي تنوع زيستي محصولات زراعي و باغي شهرستان هاي استان اصفهان و همچنين بررسي روابط موجود بين تنوع زيستي و عوامل اقليمي ‏اين استان صورت گرفت، سطح زير كشت، غناي گونه اي، يكنواختي، تنوع گونه اي و تنوع آلفا و بتاي محصولات زراعي و باغي محاسبه شده و مورد ارزيابي قرار گرفتند. بدين منظور، اطلاعات مربوط به سطح زير كشت گياهان زراعي و باغي شهرستان‏هاي مختلف استان اصفهان در سال زراعي 92-1391 از طريق اطلاعات سازمان جهاد كشاورزي استان و همچنين پرسشنامه‏هايي جمع‏آوري گرديد. محصولات زراعي به هشت گروه غلات، حبوبات، جاليزي، سبزيجات، علوفه اي، صنعتي و دارويي و محصولات باغي به دو گروه درختان ميوه معتدله و گرمسيري طبقه بندي شدند. تنوع آلفا و بتا نيز با استفاده از رابطه غناي گونه‏اي مساحت براي اقليم‏هاي مختلف استان محاسبه شد. نتايج نشان داد كه در گروه محصولات باغي، درختان ميوه معتدله (2/76 درصد) بيشترين و در گروه محصولات زراعي غلات (36/59 درصد) و گياهان دارويي (09/1 درصد) به ترتيب بيشترين و كمترين سطح زير كشت را دارا هستند. شهرستان هاي سميرم و برخوار و ميمه به ترتيب بيشترين و كمترين سطح زير كشت محصولات باغي را به خود اختصاص دادند. بيشترين سطح زير كشت محصولات زراعي در شهرستان اصفهان و كمترين آن در شهرستان خوروبيابانك مشاهده شد. شهرستان هاي كاشان، لنجان، و نطنز با 17 گونه گياهي، بيشترين و آران و بيدگل با سه گونه گياهي كمترين غناي گونه اي محصولات باغي استان را در برداشتند. بيشترين و كمترين شاخص يكنواختي محصولات باغي به ترتيب مربوط به شهرستان هاي اصفهان (83/0) و سميرم (192/0) بود. شهرستان هاي فلاورجان، خميني شهر، كاشان، نايين و نجف آباد داراي بيشترين شاخص يكنواختي در محصولات زراعي و شهرستان اصفهان كمترين ميزان اين شاخص را نشان داد. به طور ميانگين بيشترين و كمترين شاخص تنوع زيستي شانون- وينر در محصولات زراعي به ترتيب مربوط به گياهان علوفه اي (929/0) و جاليزي (442/0) بود. اين شاخص براي درختان معتدله بيش از دو برابر درختان گرمسيري گزارش شد. بيشترين و كمترين ميزان تنوع آلفا به ترتيب در شهرستان‏هاي واقع در اقليم‏هاي معتدل و بياباني گرم مشاهده شد. اقليم بياباني معتدل نيز بالاترين ميزان تنوع بتا را شامل شد.

Introduction Agricultural biodiversity has spatial, temporal and scale dimensions especially at agro-ecosystem levels. These agro-ecosystems that are used for agriculture are determined by three sets of factors: the genetic resources (biodiversity), the physical environment and the human management practices. Most agricultural areas can be returned to their natural landscape after subsequent generations. Studies on spatial patterns of species diversity are fundamental to biological conservation. Agricultural biodiversity is essential to satisfy basic human needs for food and livelihood security and it is active lymanaged by farmers and many components need human interference (Maguran, 1996). FAO estimates that 75% of crop varieties have been lost during the last 100 years. One third of the 6.500 domestic livestock races are endangered. The genetic erosion of crops and livestocks threatens food security. Plant diversity of usually evaluated by many indexes of which Shannon index is the most important ones. This index in agroecosystem rarely exists. Koocheki et al. (2004) and Nassiri Mahallati et al. (2005) in comprehensive surveys evaluated agrobiodiversity of agricultural systems at species variety and cropping systems for Iran and they found that the diversity at all levels have been declining due to introduction of new agricultural technology. In consideration to the lack of studies, this study was conducted in order to evaluate the biodiversity of agronomical and horticultural productions in Isfahan province and to assess relation of biodiversity and climate. Materials and methods This study was performed for Isfahan province in 2014. For this purpose, 24 regions of the province were selected. Planting area, species richness, species evenness and alpha and beta diversity of different agronomical and horticultural productions were determined. The information about agronomical and horticultural planting area for different regions of Isfahan was gathered. Agronomical crops were classified to seven groups; cereal, pulses, vegetable, forage, industrial crops and medicinal plants and horticultural plant classified into 2 groups; temperate and tropical fruits. The Shannon index was calculated based on the cultivated area as equation 1. For determination of distribution condition of the crops we used from evenness index. Alpha and beta diversity was calculated by spices richness- area equation for different climate of province. Results and discussion The result showed that tropical fruits (76.2%) and cereal (59.36%) showed the highest planting area and medicinal plants (1.09%) were included the lowest planting area in Isfahan province. Semirom and Borkharomeymeh regions had the highest and lowest horticultural planting area, respectively. The highest planting area of agronomical products was observed in Isfahan and the lowest amount of the trait was gained in Khorobiabanak. The highest species richness in horticultural plants was in Kashan, Lenjan and Natanz (17 species) regions and the lowest was obtained in Aranobidgol (with three species) regions, respectively. This condition was in line with climate of the regions. Ardestan and Isfahan regions were contained the highest (29 species) and Khorobiabanak had the lowest (11 species) species richness of agronomical plants. The highest and lowest species evenness of horticultural productions was gained in Isfahan (0.83) and Semirom (0.192), respectively. Felavarjan, Khomeinishahr, Kashan, Nain and Najafabad regions had the highest and Isfahan region was contained the lowest species evenness of agronomical productions. Many study demonstrated that there is a positive and high correlation between species evenness and diversity. This condition was true for our study. The forage and vine crop showed the highest (0.929) and lowest (0.442) Shannon indices, respectively. The lowest and highest alpha diversity were observed in moderate and desert-hot climates, respectively. It because that the planted crop in moderate climate was higher than desert-hot climate. Desert-moderate climate was obtained the highest beta diversity. Conclusion The results showed that tropical fruits and cereal were content the main planting area and medicinal plants were included the lowest planting area of Isfahan. The highest species richness in horticultural plants was in Kashan, Lenjan and Natanz regions. Ardestan and Isfahan regions were contained the highest and Khorobiabanak had the lowest species richness of agronomical plants. The highest and lowest species evenness of horticultural productions was gained in Isfahan and Semirom, respectively. The lowest and highest alpha diversity was observed in moderate and desert-hot climates, respectively. Desert-moderate climate was obtained the highest beta diversity.