Seyed Mehrdad Kazemi; Hamidreza karimzadeh; Hosein Bashari; Mostafa Tarkesh Esfahani
Volume 25, Issue 4 , February 2019, , Pages 789-804
Abstract
Considering the role and importance of grazing on vegetation structural changes, thisstudy aimed to assess the effects of various grazing intensities on vegetation parameters in semi-steppe rangelands of Alavigeh, Isfahan. Three rangeland locations with relatively homogeneous ecological conditions ...
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Considering the role and importance of grazing on vegetation structural changes, thisstudy aimed to assess the effects of various grazing intensities on vegetation parameters in semi-steppe rangelands of Alavigeh, Isfahan. Three rangeland locations with relatively homogeneous ecological conditions and various long-term grazing intensities (light, moderate and heavy) were selected. Four perpendicular transects with 100 meters length (two parallel transects and tow transects perpendicular to the general slope of the area) were established in each site and vegetation parameters including vegetation cover, density and palatability class of the species were recorded in 10 plots. The Margalef richness index and Shannon-Vainer diversity and evenness indices of the plots were calculated. A one way ANOVA was used to compare the vegetation parameters in sites with various long term grazing intensities. According to the results, the sites with low and moderate grazing intensities had higher plant density and vegetation cover compared with site grazed heavily and these vegetation indices varied significantly between the sites (P< 0.05). The species composition of the light and moderate grazing areas mainly included class II species with 72% and 54%, respectively. The heavily grazed site was dominated by the species with low grazing palatability (69%). The plant diversity, richness and evenness indices of the sites with low and moderate grazing intensities varied significantly (p < 0.05). The log normal was the best fitted parametric model among species abundance models for the low and moderate grazed sites, indicating a stable vegetation community. Log series were fitted to diversity data in the heavy grazed site, indicating an unstable vegetation community. RDA analysis revealed that there was a distinct grazing gradient and three vegetation zones could be clearly separated with various vegetation compositions. Although vegetation condition is appropriate in the sites with low grazing intensity, also the vegetation regeneration can benefit from moderate grazing intensity. Biological considerations are required in the management of rangeland ecosystems in arid and semi-arid ecosystems due to the fragile nature of these ecosystems.
Ali Asghar Naghipour borj; Jamaladdin Khaeddin; Hosein Bashari; Majid iravani; Pejman Tahmasebi
Volume 23, Issue 3 , January 2017, , Pages 442-453
Abstract
The structure and composition of plant communities are mainly affected by fire and grazing, especially in arid and semiarid rangelands. This study aimed to investigate the role of fire and grazing on soil seed bank characteristics (density, diversity and species richness) in semi-steppe rangelands of ...
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The structure and composition of plant communities are mainly affected by fire and grazing, especially in arid and semiarid rangelands. This study aimed to investigate the role of fire and grazing on soil seed bank characteristics (density, diversity and species richness) in semi-steppe rangelands of Central Zagros. A stratified random sampling was used to collect the data from 12 sites with one and five years after the last fire, and with long term light and heavy grazing history. Soil samples were collected in the autumn by auger from 0-5 and 5-10 cm from the soil surface, and the samples were cultivated in the greenhouse. All the germinated seeds were identified and counted for a 6-month period. The results showed that the one year after fire treatment under both light and heavy grazing resulted to a significant decrease in density, richness, and diversity of the soil seed bank. The richness and diversity of soil seed bank in the five-year after fire treatment and under light grazing pressure increased significantly compared to its control site. According to the results, the soil seed bank in 5 to 10 cm from the soil surface did not vary statistically under fire and grazing pressure, indicating the role of soil depth in reducing the impact of fire and grazing. Overall, it can be concluded that the grazing management after a fire event has a key role in vegetation restoration through its effects on the soil seed bank.
bahram Gholi Nejad
Volume 22, Issue 2 , August 2015, , Pages 298-307
Abstract
This study was aimed to determine the variation of species diversity, richness and evenness of plant species under various managements (different range conditions) in five vegetation types. After determining vegetation types, range condition was measured applying the method of society for range management ...
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This study was aimed to determine the variation of species diversity, richness and evenness of plant species under various managements (different range conditions) in five vegetation types. After determining vegetation types, range condition was measured applying the method of society for range management (SRM). In order to assess species diversity, richness and evenness, canopy cover percentage and species density were determined along transects within plots. Species diversity was determined using Simpson index, Shannon-wiener function and Hill index(N1 and N2) and species richness was determined by Margalef, Minhinnick, Bootstrap and Jack-Knife methods and species evenness was measured using Simpson, Camargo, Smith-Wilson and Nay revised index. Mean comparison test (non-paired t-student test) was used to determine the relationship between species diversity, richness and species evenness under different conditions. The results showed that in various managements with changes in range condition, a trend of regular changes could be observed between vegetation cover and range condition. In other words, the value of estimated indices of species diversity and evenness was higher in good range condition as compared to the fair and poor range condition; however, the maximum value of species richness was related to good, fair, and poor conditions, respectively. Results of mean comparisons showed a significant difference between good and poor condition for most of the indices used in species diversity, richness and evenness, while there was no significant difference between good and moderate condition.
Naghmeh Gholami; Mansur Mesdaghi
Volume 18, Issue 4 , September 2012, , Pages 515-525
Abstract
In this research, the spatial patterns of shrubs were determined by using T-square distance method in protected and unprotected areas of Golestan National Park. The results indicated that the patterns of shrubs were clumped – regular and clumped – random in woodlands. There were numerous ...
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In this research, the spatial patterns of shrubs were determined by using T-square distance method in protected and unprotected areas of Golestan National Park. The results indicated that the patterns of shrubs were clumped – regular and clumped – random in woodlands. There were numerous species of shrubs in protected area and the canopy cover of grasses and forbs were much higher under the shrubs than that of unprotected area. So the richness and diversity of the species were higher than the unprotected area. The dominant species of unprotected area was Ephedra distachya and the grasses and forbs had less contribution in vegetation of the area. Bare soil and rocks were appeared more frequently.
Parvez Gholami; Jamshid Ghorbani; Maryam Shokri
Volume 18, Issue 4 , September 2012, , Pages 662-675
Abstract
Overgrazing can alter rangeland vegetation in different ways. In this study, we used diversity, species richness and plant functional groups as the alternative to assess the vegetation response to different grazing intensities. This was done under three grazing intensities (long-term exclosure as reference ...
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Overgrazing can alter rangeland vegetation in different ways. In this study, we used diversity, species richness and plant functional groups as the alternative to assess the vegetation response to different grazing intensities. This was done under three grazing intensities (long-term exclosure as reference area, key area, and critical area) in rangelands of Mahoor Mamasani in Fars province. Vegetation sampling was carried out by random-systematic method and measuring the cover of plant species. The results showed that species diversity and richness significantly decreased with an increase in grazing intensity. Also, the cover percentage of Gramineae، Papilionaceae، Primulaceae، Umbelliferae and Valerianaceae significantly showed a negative response to grazing intensity while a positive response was found for Cruciferae، Labiatae، Plantaginaceae and Malvaceae. Moreover, some functional groups such as annuals, therophytes and Gramineae were significantly reduced from reference area to key area. The other finding of this study showed that decreaser plants significantly had less cover in critical area whereas increaser plants had greater cover in critical area. Species with storage of seeds in soil seed bank significantly had greater cover in aboveground vegetation in reference area than those species absent from soil seed bank. Due to the damage of some vegetation indices under overgrazing, it is recommended to make some changes in rangeland management and utilization in order to restore vegetation
Golnaz Rokhfirooz; Jamshid Qorbani; Maryam Shokri; Zianab Jafarian
Volume 18, Issue 2 , September 2011, , Pages 322-335
Abstract
Evaluation of changes in rangeland ecosystem after rehabilitation and restoration projects is important to determine the positive or negative effects of these projects. Parts of species composition in rangelands are in the soil seed bank as living seeds which are a potential for regeneration. Management ...
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Evaluation of changes in rangeland ecosystem after rehabilitation and restoration projects is important to determine the positive or negative effects of these projects. Parts of species composition in rangelands are in the soil seed bank as living seeds which are a potential for regeneration. Management and environmental factors may change the soil seed bank. This Study was carried out in mountain rangelands in Kabir watershed in Mazandaran province. A restoration project was done in this area 7 years ago and this study aimed to assess the effect of this project on soil seed bank. Soil was sampled random-systematically in control and restoration sites (210 samples) from 0-5 and 5-10 cm depths. Then seed bank composition was identified after seed germination in greenhouse. The results of this study showed that there were 38 species in soil seed bank whereas 71 species were existent in vegetation. Only 16 species were common between seed bank and vegetation. We found greater species diversity and richness in vegetation than that of soil seed bank. Only 18 species were common in the soil seed bank of control and restoration sites. Seventeen species were restricted to the seed bank of restored site. Among common species between soil seed bank of two sites, the project significantly influenced the seed bank of two species. Also, the restoration project significantly increased the richness and diversity of soil seed bank. Some species were unique to the specific soil depth. The results of this study showed that the soil seed bank would be altered by restoration and rehabilitation project and this depended on vegetation change due to restoration, type of treatment and time since project was performed.