جستجوی مقالات مرتبط با کلیدواژه « beta diversity » در نشریات گروه « اکولوژی »

Choosing management strategies are influencing the vegetation characteristics and plant diversity in rangelands. We have studied the effects of three management treatments including overgrazing, exclusure, and exclusure with restoration operations on vegetation characteristics of plant cover, composition, and diversity in Kiasar Chardange summer rangelands. In each management treatment, three random transects with the length of 50 m were established in the pasture and in five random plots of one square meter nested in the transects, the percentage of canopy cover, the composition of three palatability classes were recorded and the indices of plant diversity, plant evenness, species richness were calculated. For comparing the effects of different treatments on vegetation characteristics and diversity indices, an analysis of variance with equal subsamples was performed. Nonmetric multidimensional scaling was used to interpret the scattered patterns of plant compositions in relation to different management treatments. The results showed that all diversity, evenness, and richness indices were significantly different in three management treatments (p<0.05) The exclusure with restoration treatment had the highest indices of Simpson diversity (0.74), Shannon-Weiner diversity (2.12), Margalov richness (1.44), Mehnick (1.04), alpha diversity (6.13), and beta diversity (20.87). In contrast, the overgrazed site had the lowest values. The Camargo (0.77) and Smith-Wilson (0.87) evenness indices had the highest values for exclusure and the lowest values for exclusure with restoration treatments. Our findings could be a road map for future planning in similar sites. For rehabilitation of rangelands and improving plant diversity, restoration treatments in exclusures are recommended.

One of the main objectives of organic agriculture is low negative effect on the environment and according to this issue, maintaining biodiversity is one of the key responsibilities of this agriculture system. Disuse of chemical fertilizers and using mechanization with less intensity caused significant increase in biodiversity in organic agriculture. Insect's diversity can help in biological control of pests, pollination and biological control of weeds and diseases. This study was performed based on the key role of insects in ecosystem function, especially in organic agro-ecosystems and effective factors for biodiversity of them and also with respect to the high potential for progressing of organic agriculture in Iran. The purpose of the study was to identify different families of insects in conventional and organic fields for wheat and potato crops in Fariman city. The study was carried out in wheat and potato fields at Fariman city in 2012. In order to collect insects, we used a sweet net with a diameter of 50 cm in 10 different regions of the fields. Sampling was performed after 45, 75 and 105 days after planting. Sampling was conducted which it covers total farm area. Shannon-weaver index, Simpsons reciprocal and Margalef indexes were used to calculate the insect’s biodiversity and Pielou and Simpson were used to calculate the species evenness. Relative frequency (pi) was used to determination of dominant species in each agro-ecosystem and the species with the highest relative frequency was considered as dominant species. In order to compare the alpha and beta diversity between two organic and conventional systems, we fitted the power function for species richness as a dependent variable and sampling number as an independent variable. The results of the wheat farm showed that the total number of collected insects’ families during the growing season in the organic farm was higher than the conventional farm (2047 number of insects from 41 families vs. 1928 from 34 families, respectively). From total families, 32 families were the same in both organic and conventional wheat systems and 9 families were collected from the only organic farm. Two families were observed only on the conventional farm. Species richness was the same in both organic and conventional at first stage of sampling, but in the organic system, it was higher at the second and third stage of sampling. Insects’ diversity in the conventional farm was higher than organic based on obtained values for alpha diversity. Calculated beta diversity in the organic system was higher than conventional. In fact, beta diversity is the increasing rate of the species richness per increasing of sampling number and the high value of beta diversity in the organic system indicates that species richness and biodiversity of the organic system were higher than conventional at total farm area. In potato organic and conventional farms, 435 insects (from 18 families) and 787 insects (from 22 families) were collected, respectively. From total trapped families, 15 families were the same in both organic and conventional systems, 7 families only were in conventional farm and three families observed only in the organic farm. Therefore, species diversity in conventional system was higher in comparison with the organic system in the potato crop. Two families were introduced as dominant species in the organic farm with a relative frequency of 17% and 15.6%, respectively and Miridae family was dominant species in the conventional farm as 27.8% of relative frequency. Alpha diversity in conventional system was higher than organic. Beta diversity in conventional system was higher in 45 and 75 days after planting, but it was lower in 105 days after planting than organic. In total, the results showed that alpha and beta diversity were higher in conventional than organic. It seems that the reason for higher biodiversity in conventional compared to organic was related to failure to comply with the organic principles in potato farm. It can be concluded that the move towards organic agriculture, in addition to preserving and enhancing biodiversity in agricultural ecosystems, has led to a reduction in using chemical pesticides and, as a result, the reduction of environmental pollution will be followed by the sustainability of agricultural production.

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.
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.
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.

Measuring the diversity of plant functional types, identifying their characteristics, and their classification will help to identification of woodland germination capacity and implementing appropriate range management programs. The study was designed to measure the species diversity and to identify plant functional types in three adjacent ecological sites in Shimbar or Shirin Bahar region. During winter, spring and summer since 2013 to 2014, the data regarding the percentage of species coverage were taken from 106 plots using stratified random sampling method in the south facing slopes, north facing slopes and the wetland. Species diversity (Alpha diversity) and habitat diversity (Beta diversity) were measured using PAST and SDR softwares. According to the Shannon-Wiener and Simpson indices the greatest species diversity were found in the wetland, south slopes and north slopes respectively. Species richness was higher in northern slope than northern slopes and the lowest in wetland. For classifying and determining response of vegetation to environmental factors and identifying plant functional types, about 66 resistance to disturbance characters were measured and subjected to clustering by Ward method in R software. The annual and perennial species were classified into 21 and trees and shrubs to 8 classes.

To beautify and improve landscape of Mashhad metropolitan city, weed situation of Khorshid Park was studied. Thirty weed species belonging to 15 plants families formed the relatively diverse weed communities established on plains and hillsides of the park most of which belonged to Asteraceae, Poaceae and Fabaceae families, respectively. Sixteen of which (53%) were annuals, 37% were perennials and 10% were biennials. the richness of the plain weed community with 26 species was more than hillsides with 20 species. Weed community in hillside weed was highly uniform while uniformity of weed community in plains was less than hillsides showing signs of dominance at the beginning of the season. The Logarithmic distribution model of species showed the habitats are not relatively demolished, The similarity between weed communities of plains and hillsides was less than the similarity between seasonal weed communities of each habitat indicating more adaption of weeds to habitat conditions. The less similarity was obtained between spring weeds of both habitats while the most similarity was observed between summer weed communities. This survey proved that plains are threatened by noxious weed species such as Acroptilon repens L., Cynodon dactylon L., Hordeum murinum L., Bromus tectorum L. and Setaria viridis L. while hillsides menaced by Acroptilon repens L., Alhagi camelorum Fisch., Cirsium arvense and Xanthium strumarium L.