Journal of Rangeland Science
Volume:3 Issue: 1, Aut 2012

This research was conducted to investigate the relationships between soil (organic matter, potassium, phosphorous, sodium, fine gravel, soil texture, EC, lime, gypsum, nitrogen) and environmental (elevation, slope) factors with distribution of vegetation types in rangelands of Sabzdasht, located in Bafgh, Yazd province at 2012. For this purpose, four vegetation types were selected as follows: Artemisia sieberi; Artemisia sieberi, Stipa barbata, Eurotia ceratoides; Dorema ammoniacum, Artemisia sieberi, Eurotia ceratoides; and Hammada salicornica. Minimal area was determined using nested plots. Afterward, vegetation factors were measured and five soil profiles were dug randomly in minimal area. In each profile, data for depths of 0-10 and 10-80 cm were recorded. Principal component analysis was applied to analyze the data. Results showed that soil texture, potassium, phosphorous, EC and lime had the most impact on variation and distribution of vegetation types.

Recognizing the herbaceous plant species diversity could use as an important indicator applied for the rangeland and forests management. Considering the presence of vegetation and animal husbandry in Zagros region, Iran, being aware of the diversity and richness of plant species is necessary to management or the destructed vegetation restoration. In order to study the effect of aspect and elevation on species diversity of herbaceous plants 160 four m2 quadrates were sampled via transect method in the Dasht e Zahab in Kermanshah, Iran. In each quadrate a list herbaceous species plants, altitude and aspect were recorded. After the inventory, the plant diversity indices were calculated and compared in three elevation classes (low: <800 m, moderate: 800 to 1200 m and high: >1200 m) and four aspect classes (North, South, East and West) using Shannon-Wiener diversity and Margalef richness indices. One-way ANOVA was used to investigate the effect of independent variables (altitude and aspects) on dependent variable (species diversity and richness). The results showed a significant effect of aspect and altitude on the diversity and richness of herbaceous plants (P<0.05). The maximum and minimum diversity and species richness were observed on the northern aspect coupled with middle elevation and on the southern aspect with low elevation, respectively.

Subalpine ecosystems are highly fragile as compared to biological and environmental factors. Landslide is one of the ruinous upshots of this ecosystem. One of the impressionable areas in the cause of natural factor is Masoleh watershed in western Alborz Mt, (Iran). In order to landslide hazard zonation, landslide index and frequency ratio method based on twelve causative factors such as slope, slope aspect, land use, lithology, distance from faults, distance from road, distance from stream, rainfall, range condition, Stream Power Index (SPI), Component Topographic Index (CTI) and elevation Receiver Operator Characteristic (ROC) curve analysis method was also used to evaluate the model. The results showed that geological, physiographical and grassland conditions have an important role in landslide area. Overgrazing, grazing in forth of season, early grazing, late term egression, and excess livestock are considered as direct affecting factors on vegetation, so that they have simultaneous role to make the landslide risk. The verification results via ROC curve showed that the landslide index model (85%) performed slightly better than the frequency ratio model (82%). It was concluded that managers and protectors of this ecosystem can inhibit and conserve the landslide by decreasing the amount of livestock, and short-term exclosure on critical area, and biomechanical dams in landslide-occurred area.

Rangeland health assessment provides qualitative information on ecosystem attributes. We examined changes in rangeland health in the Zagros semi-arid rangelands of Iran at fixed sites between 2001 and 2011, over the 10-year period. The rangeland fragments significantly declines in the quality of the vegetation, and changes in plant species were driven largely by seasonality, and to a lesser extent, amount of rainfall. Three indices of rangelands health (composition, function and stability) developed using site-based vegetation and landscape data. The results indicated that the majority of sites had intermediate values of the three indices, and few sites had either very low or very high values. The indices of composition and function were strongly correlated with the subjective ratings applied to each site at each measurement period. The results of this study highlight the difficulty of detecting change over extensive areas of rangeland, and of separating management induced effects from climatic effects in an environment which experiences wide spatial and temporal variation in rainfall. Results showed that soil surface resistance decrease and water flow pattern degradation were the most important causes in rangeland health decrease. Although, Chalghafa rangelands have enough rain falls to support habitation, humans had degraded the landscape. Moderate grazing is the best way to use the grazing land without severe reduction in abundance and biomass of species.

Abstract. Eurotia ceratoides (L.) C. A. Mey is an important plant species in semi-arid lands in Iran. New approaches are required to determine the distribution of this plant species. For this reason, geographical distributions of Eurotia ceratoides were assessed using three different models including: Multiple Discriminant Analysis (MDA), Ecological Niche Factor Analysis (ENFA) and Logistic Regression (LR). The study area was located in northeast rangelands of Semnan, Iran. Sampling was performed in each vegetation type using randomized-systematic method. Vegetation data in addition to environmental factor's data such as topography and soil were prepared. The MDA and LR methods were performed with SPSS software as predictive modelling methods based on presence and absence data. The ENFA model was performed by the means of necessary statistical analysis in Biomapper (Version 4.0) software only by presence data. The plant predictive mapping needs the maps of all effective factors based on model parameters. Mapping of soil characteristics was done by geo-statistical method. The accuracy of the predicted map was tested with the actual vegetation map. Predictive maps of E. ceratoides (based on the LR and MDA methods) with Kappa coefficients as 0.56 and 0.64 had a good accordance with actual vegetation map prepared for the study area. Kappa coefficient of potential habitat map (based on ENFA method) of E. ceratoides was 0.85; hence, it had a very good accordance. The results obtained by all methods showed that this species is distributed in the rangeland with pH as 7.8-8, EC as 0.17-0.26 dc/m and silty-sandy texture in 1600-2200 m elevation. Organic matter in the depth of 20-80 cm and pH in the depth of 0-20 cm did not significantly influence the differences. Minimum sampling is needed using these methods which provide worth while data about the presence of the plant species in the other places.

Biological invasions form a major threat to the provision of ecosystems products and services and can affect ecosystems across a wide spectrum of bioclimatic conditions. Therefore, it is important to systematically monitor the spread of species over broad regions. It has long been recognized that remote sensing and geographical information system could contribute to this capacity. This paper aims to investigate the efficiency of Landsat TM images in identifying and classifying invasive species Cirsium arvense and Stachys byzanthina in Vazroud rangelands of Iran. For optimizing results, the Cos(t) model was used for atmospheric correction on the image. Then multiple vegetation indices, by extracting the digital mean of pixels related to training samples of the corrected image, were calculated. A supervised algorithm using minimum distance of mean was used as a classification technique for evaluation against ground truth map. The results indicated that NDVI, Ratio, RVI, TVI and NRVI were the most suitable indices for the discrimination of Cirsium arvense species. The best indices for the Stachys byzanthina species were DVI, NDVI, PVI 1, PVI 2, RVI and WDVI. Of all the indices analyzed, DVI and WDVI were able to discriminate both species but with varying degrees of separation.

Medicago spp. is the most important forage crop in many regions of the world. Annual medics have distinct advantages over perennial Medicago. These species have faster growth rate in cultivation year, higher crude protein percentage, tolerance to pests and more vigorous seedlings. Morphological and physical aspects of pod and seeds of annual medics play a major role in the tolerance of the plants to over grazing and establishing in different type of rangelands i.e., plants with small seeds can establish better in heavy grazed rangelands, spiny pods establish better in dense compact clay soil, hard seeds increase seed bank of the soil and maintain the pasture for the next years. In order to study the variation in seeds and pods morphological traits of five annual Medicago spp. seeds of 50 accessions of M. rigidula,M. polymorpha, M. orbicularis, M. radiata and M. minima, provided from natural resources gene bank of Iran, were sown in pots. Data were collected for size of the seeds, spins and pods, number of seeds per pod, levels of hardseededness and elevation of the seed origin. Results showed that M. rigidula 1000-seed weight had the most variation. Largest seeds were 17 times bigger than the smallest one in this species. M. polymorpha showed the most variation in the elevation of seed origin (upper=2280 m, lower=5 m above sea level). M. radiata showed the most variation in the amount of hard seeds. M. rigidula showed the least amount of hard seeds (mean=59.93). M. radiata had the largest pods. M. radiata and M. orbicularis showed the highest variation in pod size. M. polymorpha showed the highest variation of spine length. The correlation between 1000-seed weight and the elevation of seed origin was positive and significant for M. polymorpha and negative and significant for M. orbicularis. Based on Ward clustering method, the five species were grouped into two clusters in a dendrogram. First cluster included M. minima and M. polymorpha and the second cluster included M. rigidula, M. orbicularis, and M. radiata. This result indicated that it may possible of interspecific hybridization between species of the same cluster.

Several studies have been performed to evaluate the desertification in Iran and other countries which led to present national and regional models. One of them is IMDPA model. This model was used as a case study in Taraz Nahid, Saveh, Iran. In this study, five factors including climate, soil, vegetation, irrigation, and socioeconomic ones were evaluated. According to the region conditions for each criterion, several indices were considered. Based on the selected indices for each criterion, the qualitative maps were developed from geometric mean of indices for each criterion and finally, the desertification intensity map was prepared from the geometric mean. The final desertification map shows the balanced (moderate) and intense (severe) classes of desertification process in the region. According to the performed evaluations, the soil texture index with the average value of 3.75 (very severe class) and vegetation conditions with the average value of 2.9 were more effective indices in the region desertification. Also, the desertification quantitative intensity value (DM=2.31) was calculated for the entire study region that showed the moderate class for this region.