عنوان مقاله [English]
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.
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.