مجله مرتع
پیاپی 1 (بهار 1386)

Biodiversity is an important concept in ecology which gained more attention in recent years and its various aspects have been studied. One of its aspects is the relationship between diversity and forage production which has been studied by many researchers. This study attempt to look at this relationship for mountainous grassland and shrubland of Zagros in Iran. The sampling was done on random- systematic way using 1 m2 in grassland type and 4 m2 in shrubland both along 50 meters transects. In order to calculate diversity and evenness, three indices of McIntosh, Simpson, and Shannon were used. Species richness was calculated by counting the number of species within each plot and forage production was estimated by clipping. A regression analysis with Stepwise method was performed. The results indicated that there was no significant relationship between diversity and forage production grassland. In contrast, the relationship was significant in shrubland between forage production and diversity indices of Shannon and McIntosh. Using partial coefficient table there was more influence of McIntosh index compared to Shannon index.

Knowledge of animal forage requirement is necessary for determination of grazing capacity and making equilibrium between livestock and rangeland resources. Animal daily forage requirement depends on body size and forage quality. It is difficult to define a common animal unit in Iran as there are about 27 sheep breeds each with special body size and physiological features. So it is important to determine the body size of animal unit, daily metabolic energy, and the forage quality for proper management. In this study two herds of Hamadan Mehraban breed including 70 sheep (15 three years old ewes, 15 four years old ewes, 5 three years old rams, 5 four years old rams, 15 three months old and 15 six month old lambs) in three stages have been weighed. The daily forage requirement was determined by NRC (1985) tables and MAFF formula. In former, we found the daily metabolic energy requirement from the table according to the forage quality in two growth stages. The animal daily forage requirement was 1.56 and 2 kg for early and final growth stages. In latter, the daily metabolic energy requirement was calculated by fomula. The animal daily forage requirement was 1.83 and 2.34 kg for early and final growth stages.

Soil erosion is one of the imminent factors to soil and water resources of country. As since the role of vegetation cover on soil conservation in vary environmental situation is different, so in this research, two aspects of northwest and northeast from the highest upland of mountain watershed in northern Alborz (Javaherdeh) were chosen. Rangeland health and soil erosion have been evaluated by Dauben Maire and empirical PSIAC methods in two types of shrubland and grassland. In order to determine the influence of factors on soil erosion and rangeland health, data have been analyzed by multi regression and mean comparison between two habitats have been done by T-test method. The results showed that there is a strong significant relationship between soil erosion and rangeland health in both habitats. It also showed that soil erosion have significant correlation with vegetation cover and litter in grassland and also with vegetation cover and soil conservation in shrubland. Rangeland health also showed a significant correlation with slope, total vegetation cover and total range plant production in grassland and with cover percentage of perennial grass, shrub and basal area in shrubland. The rangeland health degree was not different between two habitats but the rate of soil erosion was significantly different in two areas.

Range condition assessment as an important recognition tool in range management has special rule to recognize how much range deviated, if employed indicators have ability to determine and separate differences in ecosystem and also to assess its function. This study aimed to determine the most important ecological indicators to achieve suitable indicators for rangeland health and condition assessment using rangeland health model. This study was carried out in three sites, long-term exclosure, mid-term exclosure, and critical area, of Saveh Rudshur rangeland. In each site 17 rangeland health indicators based on soil/site stability, hydrologic function and biological integrity were assessed. Results showed that in mid-term exclosure area indicators such as functional/structural groups, forage production, plant community composition and pattern, bare ground, wind erosion, soil surface resistance to erosion, and soil surface loss or degradation had the most influence on rangeland health with greatest effect of functional/structural groups. In long-term exclosure area plant mortality, functional/ structural groups, invasive plant, bare ground, wind erosion, pedestals and/or terracettes, soil surface resistance to erosion interred into the model as effective indicators. Among them, plant mortality had the most influence on rangeland health. In critical area some indicators like functional/ structural groups, invasive plant, bare ground, wind erosion, soil compaction, soil surface resistance to erosion, soil surface loss or degradation were important on rangeland health with greatest effect of functional/ structural group indicators. Finally this study showed that all three attributes are effective in rangeland health changes but biological integrity are more important.

It is important to know soil properties, particularly its chemical aspects, for the proper management of rangeland ecosystems. The aim of this study is to find the impacts of grazing on vegetation and some soil chemical properties, in three areas, the key, reference, and critical, located in rangelands of Kojour river basin in the southwestern of Noushahr, Iran. The vegetation cover data was collected from 20 1m x 1m quadrats in each area through random-systematic method in the early of grazing season. The soil data was sampled from two depths (0-10, 10-30 cm) before and after grazing. Some factors such as the organic carbon, the percentage of soil organic matters, total nitrogen, absorbable phosphorus and potassium, pH, and buffer density were measured. The results showed an inverse relationship between the grazing intensity and the amount of carbon, nitrogen, and soil organic matter, however, a direct relation exists between the grazing intensity and the amount of soil potassium, phosphorus, pH and the ratio of carbon to nitrogen. The result for vegetation data showed that more grasses and forbs present in the reference site and shrubs increased with an increase in grazing intensity. Reference site also had more species of palatability classes of I and II but more species of class III and unpalatable species were found in critical area.

Measurement of surface organic matter (SOM) and its mapping by traditional methods is so expensive and time consuming. Assessing the potential and efficiency of remote sensing techniques for SOM can solve these problems. In this study the relationship between soil spectral reflectance (17 spectral bands such as original bands of Landsat Enhanced Thematic Mapper plus ETM+, ratio bands and principal component analysis) and soil organic matter contents for 94 samples was investigated in rangelands of Mehr, Sabzevar, Iran. The samples were gathered using GPS from a random nested-systematic network. The rate of organic matter for each sample was estimated at the soil laboratory using wet oxidation method. The ETM+ data were orthorectified to omit the relief displacement errors using ground control points and digital elevation model with RMSe less than 10 meters. In addition to main bands, some suitable image processing such as vegetation and soil indices, rationing transformations, tasseled cap and PCA analysis were applied to produce arithmetic bands. The spectral number of each sample on the different bands was extracted and correlation between OM and spectral numbers was investigated. The results showed that there was significant relationship between greenness, moistness DVI, NDVI and SAVI against SOM (α=0.05). Multiple and stepwise regression models with excluding and including outliers (3Sd, 0.05, 0.01) were used to select the best fitted models. The results showed that there was no significant model in multiple regression model (α=0.01 and 0.05). But, the best fitted stepwise models in two cases of outliers were significant (α=0.01 and 0.05). The shortest variables between studied models were belonging to Stepwise models. This study showed that remote sensing data have relatively capability to estimate the soil organic matters in the study area.

The purpose of this study is to estimate the cover and mapping the rangeland vegetation cover percentage using Landsat 7 sensors, ETM+ digital data. So the ETM+ images of Chamestan mountain rangelands in Mazandaran Province were analyzed. First of all, the panchromatic band image was georeferenced to digital topographic map. Then the other bands images were registered to pan band. For field data collection stratified random sampling method was employed. In each sampling unit, 10 plots were located randomly on perimeter of a supposed circle with about 20 m radius and then percentage vegetation cover has been estimated on each plot. Then the average of 10 estimated covers has been considered for each sampling unit. For image processing, vegetation indices (VI), band fusion, band ratios and principle component analysis (PCA) were applied. The fused bands outcomes, along with the main bands imageries, VI, PCA, ratios results have been used to map the vegetation cover estimation and its percentage cover mapping. Stepwise regression has been established between percentage cover data gathered from each sampling units and DN of related pixels extracted from the images and the resulted model was used to estimate the vegetation cover percentage. Then the applied model to the images produced the map that states the vegetation cover percentage of the region. The map has been reclassified to reach categorized vegetation cover percentage map of the studied area. Finally the accuracy of the final map has been assessed by field controlling for the ground truths.

The accurate data is essential for proper designing of soil and water conservation structures. The development and/or recognition of accurate techniques based on available data is also necessary for engineers and managers, since the sediment measurement is not taken place in many watersheds. In the present study, an attempt has been made to assess the applicability of some erosion and sediment yield models viz. USLE, MUSLE-S, AOF, MUSLT, MUSLE-E, USLE-M and AUSLE in estimation of storm-wise sediment yield from standard plots in rangeland. For this propose, the entire input data were collected from three plots installed in Khosbijan Natural Resources Research Station in Arak township. The models’ estimates were then compared with observed sediment data for 12 storm events. The results of the evaluation verified the significant difference among models in estimation of erosivity index. Besides that, the significant correlation was recognized only between MUSLE-E and observed sediment data with correlation coefficient of 99.4%