Journal of Rangeland
Year:2016 | Volume:9 | Issue:4 |Papers Count:14

Drought is one of the most important factors limiting the production of plant species in south Iran. The objective of this study was to evaluate the effects of drought stress and seed hydro-priming on some morphological and physiological traits of Cymbopogon olivieri. A completely randomized design was used with four levels of drought stresses (25, 50, 75 and 100 percentage of filed capacity) and hydro-priming (0 or control, 24, 48 and 72 hours) in four replications and 50 seeds per replication. Seeds were cultivated in plastic pots in greenhouse condition. All pots were irrigated with distilled water. Some morphological and physiological traits of the species were measured after a period of 40 days. Analysis of variance and mean comparison tests were used to evaluate the differences between the treatments. According to the results, increasing the drought stress caused a significant decrease in the measured morphological and physiological traits of C. olivieri. The highest morphological and physiological traits of the species including photosynthesis attributes, transpiration, leaves water contents, chlorophyll a and ab were identified in the seeds treated by hydro-priming for 48 and 72 hours under moderate drought conditions (25 and 50 percentage of filed capacity).

The purpose of this study was to assess the logistic regression model capability to map the spatial distribution of plant species in Taleghan Miany rangelands. Systematic-random sampling method was used to collect vegetation and environmental data (such as topography and soil factors). Three transects with 150 m lengths were established in each sampling unit and the vegetation cover percentage were determined in 15 plots along each transect. Soil samples were collected from the two sampling plots in each transect randomly. Geo-statistical methods were used to produce the environmental maps. Topographic maps were also produced using digital elevation model. Species distribution models were prepared using logistic regressions equations in Geographic Information System (GIS). Kappa index (k) was used to evaluate the agreement between prediction models and field data. According to the results, kappa index obtained for Agropyron intermedium habitat model was 0.83. The calculated Kappa for Stipa barbata and Astragalus gossypinus habitat models were 0.79 and 0.80 respectively. This index for Thymus kotschyanus habitat was 0.68. This study indicated that logistic regression model could predict the habitat suitability of the four studied species appropriately. The produced logistic regression model for predicting Agropyron intermedium habitat was more efficient because this species has more specific habitat requirements. The results of this study can be used in rehabilitation, conservation and management programs in rangeland ecosystems.

GIS and satellite images have widely been used in natural resources assessment and management. Vegetation cover can be measured using remote sensing indices. The objective of present study was to investigate the application of AWiFS satellite images to measure vegetation cover percentage in Semirom- Isfahan province. Vegetation cover percentage was measured in 150 plots with size of 100 m2 each in 2009. Linear regression between field data and remote sensing vegetation indices was used to produce vegetation cover in the study area. Vegetation cover models were produced using different indices. According to the results, SAVI index had the highest correlation with field data (r = 0.74) and it was used to produce vegetation cover percentage map. Study area vegetation cover was classified in four classes: <20%, 20-30%, 30-40% and >40% using SAVI index. The produced vegetation map indicates that most of the region had low vegetation cover (<20% and 20-30%). The correlations of other measured vegetation indices including NDVI, PVI, RVI, TSAVI and MSAVI with vegetation cover percentage were 0.64, 0.69, 0.71, 0.72 and 0.70 respectively.

Plant growth and reproduction can be reduced by severe livestock grazing pressure. In contrast, rangeland shrubs and mycorrhiza fungi may both provide soil moisture and nutrients for their coexisting plants. We tested the simultaneous effects of grazing and shrub canopies on the coexistent relationship between mycorrhiza and Bromus kopetdaghensis, in Baharkish rangelands, Quchan, Iran, during summer 2013. Plant and 40 soil samples were collected from understory of two shrubs (Astragalus mesedensis and Acantholimon erinaceum) and the adjacent open areas; in a grazing and/or an enclosure site. Furthermore, effects of shoot clipping were tested on the colonization rate under the glasshouse conditions. Root painting method was conducted based on Philips & Heyman, colonization rate based on Glovannetti & Mosse, and spore counting via the sucrose gradient method. Results indicated that colonization rate and spore numbers were significantly reduced both under the livestock grazing in the field (35%) and 27 % in the hand clipping treatments. Shrub canopies did not have any significant effect on the spore number and colonization rates under the high grazing pressure, whereas under the enclosure site, their colonization rate was reduced to 24% and their spores increased by 25%. In conclusions, high livestock grazing pressure has definite negative effects on the symbiosis, whereas the effects of shrub canopies are more complicated and varies depending on the grazing intensity and shrub species. This study found higher colonization rate with mycorrhiza for Astragalus spp compared to Acantholimon erinaceum.

Evaluating the effects of different grazing intensities on soil physical and chemical properties is required to achieve appropriate management plans. This study was conducted in three rural areas in Sabalan mountain rangelands. A random systematic sampling method was used to collect soil samples along 600 meters transects. Six composite and 18 intact soil samples were collected using soil sampling cylinders within two depths including 0-15 and 15-30 cm from soil surface. According to the results, soil humidity percent, porosity, particle density, texture, and mean weight diameter were among soil physical charatersitics that were significantly affected by grazing in the study area. Soil organic matter, nitrogen, phosphorus, potassium, pH and EC were also affected by severe grazing pressure. Continuing heavy grazing leads to destruction of soil structure, hence controling grazing intensity is very important to avoid irreversible and inappropriate changes in soil characteristics.

Species diversity differs in various spatial and temporal scales in response to different biotic and abiotic conditions. The aim of this study was to investigate the effects of grazing impact on species diversity components in local and regional scales in Ilam province. Vegetation sampling was carried out using 40 plots of 2´2 m2 (20 plots in exclosure and 20 plots in grazed area) in local scale and 8 sites (4 sites within exclusion and 4 sites within grazed area) in regional scales. Plant species richness (gr) partitioned into additive component among plots (a1), between plots (b1) and between sites (b2). We used the PARTITION software for analysis of species diversity components in different scales. According to the results, 72 plant species were observed in exclosure and 60 species in grazed area from a total of 89 recorded plant species. Additive partitioning of plant species diversity showed that, in two regions, observed plant species components (a1 and b1) was smaller than expected values in local scale, and in regional scale and observed plant species components (b2) was greater than the expected value. Species diversity among plot (a1) in exclosure area was significantly greater than the grazed area, but there was no significant trend for species diversity between plots (b1) and sites (b2), indicating non-random patterns of plant species. The beta diversity, with respect to more contribution to total species diversity, was more important diversity component in regional scale. This study showed that some components are more sensitive to grazing, so we suggest using these indices in vegetation management studies.

The present research was aimed to assess the potential seed dispersal of plant species by different-sized herbivores of hare (Lepus capensis), Persian gazelle (Gazelle subguttrosa) and wild goat (Capra aegagrus) in rangeland habitats of Kolah-Ghazi National Park in Esfahan. Ten freshly pellet groups (dung sample) of herbivore species were randomly collected in each of selected habitat sites during spring and autumn growing seasons (April to June and October to November). Seed content of dung samples were determined in greenhouse germination experiments over a period of 8 months. In total, 1637 seedlings from 60 plant species (19, 43 and 45 seed species in dung samples of cape hare, Persian gazelle and wild goat, respectively), mainly annual with attractive inflorescence and small seeds were recorded in dung samples of the three herbivore species. Seed content found in the all herbivores dungs were differed significantly, in addition, numbers of dispersed seedlings were correlated to herbivores size. However, the observed differences in dung seed density of herbivore species was not related to their sizes; so the highest and the least number of seeds were recorded in dung samples of wild goat and Persian gazelle, respectively. Given that most of plant species recorded in the Park regenerate by seeds, and that seeds of different plant species dispersed by herbivore species, seed dispersal via dung of different-sized herbivores may play an important role in vegetation conservation and dynamics of these rangelands habitats, only if required environmental factors met. While increasing knowledge of plant seed dispersal, results of the present research can be specially applied in managing country's protected ecosystems and rangeland habitats.

Stream morphometric characteristics affect the distribution of plant species. Vegetation characteristics affect the hydrological and erosion processes in watershed basins. This study aimed to evaluate the correlation of vegetation characteristics with some morphometric characteristics including valley width, valley depth, channel width, channel depth, channel slope, valley width/ valley depth, channel width/ channel depth, valley width/ channel width, valley depth/ channel depth, (valley width/ valley depth)/ (channel width/ channel depth) in a relatively homogeneous streams derived from Hydro-geomorphic classification. According to the results, the correlation between vegetation cover percentage and valley width, channel width, valley depth/channel depth, channel width/channel depth, valley width variables were 0.62, 0.60, 0.60, 0.50, 0.44 respectively (p˂0.01). The correlation between the (valley width/valley depth)/(channel width/channel depth) variable and vegetation cover percentage was negatively significant (p˂0.01). The vegetation cover percentage had also a negative significant correlation with stream channel gradient (p˂0.05). Medium and large sizes streams had more vegetation cover compared to small streams and their vegetation cover percentage varied significantly (p˂0.05). According to the Principal Component Analysis (PCA), the correlation between the valley width and channel width factors with first ordination axis were 0.48 and 0.44 respectively. The correlations between valley width/valley depth and valley width/channel width variables with second PCA axis were 0.51 and 0.51 respectively. Also the CCA test showed that the correlation coefficient between first species axis with channel depth and channel width factors were 0.63 and 0.41 respectively. The correlations of these two variables with first environmental axis of CCA were 0.81 and 0.53 respectively. This study highlights the effects of piedmont stream geomorphic characteristics on vegetation cover percentage and presence or absence of plant species in the study area.

This study aimed to investigate the effects of some environmental factors on the distribution of Ferula gummosa and Ferula ovina in Shilander rangelands- Zanjan province. Two Ferula habitats were selected and their environmental characteristics were compared with control sites (no Ferula species present). Three transects with 150 meters lengths were established in each site and data were collected along the transects in seven plots of 4 m2 (with 20 meters interval each). Composite soil samples from 0-30 cm of soil surface were collected from the starting point, middle and end part of the established transects and analyzed in soil laboratory. Slope percentage and direction, and elevation from sea level for all plots were also recorded. Canonical Correspondence Analysis (CCA) and Redundancy Analysis (RDA) were used to explore the relationships of Ferula species with environmental variables. According to the results, slope direction and degree, gravel and silt percentage, neutralizing substance percentage and soil saturation percentage were identified as the most important factors in characterizing Ferula species habitats. Comparing the environmental characteristics of Ferula habitats with control sites revealed that sand percentage, slope, silt percentage and elevation from sea level were different statistically between these sites (p˂ 0.05). Logistic regression analysis indicated that soil pH (p˂ 0.01) and neutralizing substance percentage (p˂ 0.05) were the most important discriminating factors in Ferula habitats with the control sites.

This study was conducted with two aims, including the study of various rangeland managing effects on soil carbon sequestration and another purpose was studying of difference between the used methods of reporting the amount of soil carbon. Different approaches to calculation and presentation of carbon include using carbon concentration parameter (gr C/kg soil); Carbon mass parameter based on constant depth (ton C/ ha) and carbon mass based on equivalent depth (ton C/ ha). However some scientific reasons show, the approach of carbon mass based on equivalent depth; due to fluctuation of calculation depth effect on the role of bulk density changes that by applied its role can estimate the actual soil carbon in an equivalent depth. By soil sampling from shallow depth in five kinds of rangeland utilization and management (including of pen area, rural, enclosure, key area (moderate grazing) and watering place); the amount of carbon was calculated according to the above-mentioned methods then statistical analysis was used. The results of means comparison showed that base on first methods home range, enclosure and key area with the amount of 37.80, 27.30 and 22.92 gr c/ kg soil have the highest carbon while conflicting results were obtained base on equivalent soil mass. To resolve this prevalent inconsistency in numerous studies, equivalent soil mass were calculated and its result showed that pen site have the highest carbon mass 108.64 ton per hectare in equivalent depth. Overall results in this study area, the conventional methods that are used for calculating organic matter Due to the unequal soil masses are not accurately expressing about differences in soil mass. For the evaluation of reliable storage of soil organic matter and nutrients; comparison soil masses should be equivalent. However, the validity of these findings is recommended to be tested in other sites for achieving practical results.