مجله مرتع
سال دوم شماره 1 (پیاپی 5، بهار 1387)

The aim of this research was to investigate the relationship between litter quality and soil characteristics (carbon, nitrogen, potassium and phosphorous) in three range species, Artemisia sieberi, Artemisia aucheri and Acantholimon sp. Soil and litter sampling was done at the end of growing season (autumn 2004) after identification of the sites of these species in Vard-Avard. Sampling was conducted in the key area of each site based on randome-systemic method. Number of determined plots was based on the characteristics of the studied sites. The results showed in Acantholimon sp. litter the characteristics of C, N and P were greater than the other species. But in generally Artemisia sieberi litter quality was the best.

In this study, the replacement of different range sites and their relationship with soil properties was investigated. For this purpose, according to teh elevation and aspect three sites were selected including shrubland, grass-shrubland and grassland. The measured soil factors were calcium, magnesium, Phosphors, Potassium, lime, ammonium, nitrate, organic matter, PH, EC, bulk density, moisture and soil texture. Also, the vegetation cover in each site in the key area was measured. Detrened correspondence analysis (DCA) was used to achieve the relationship between soil and vegetation. The result showed that some changes which have in the performance of range ecosystems are the result of decrease in nutrirional elements; this issue has resulted in the distinction of the sites of grassland, shrubland and grass-shrubland. In fertile grasslands with reduction of nutrients, first, grasses will replace the forbs and in the next stage, the grasses are replaced by shrubs. This trend is accompanied by decease of organic substance, humidity and potassium, and ultimately the pH and sand rate will increase in the shrubland.

In order to investigate the effect of long-term exclosure on ecological indicators, the long-term exclosure of Rudshur in steppe rangelands was selected. Then, three functional attributes of rangeland health (soil/site stability, hydrologic function, and biotic integrity) were evaluated using rangeland health model. In this study 17 ecological indicators were used. Result showed that long-term exclosure was evaluated as moderate category in comparison to reference area. Based on rangeland health model, moderate category illustrate that the rangeland has been destroyed and its potential for forage production was reduced, but the rangeland has the capacity to reach the threshold health. Also if the Ranger continues to have this system of management, the rangeland health will be less than ecological threshold line. Processes such as lack of livestock grazing, small herbivore and ant colonies activities have caused that the health of long-term exclosure to be at risk category.

Vegetation is affected mostly by climatic factors, therefore a knowledge of relationship between vegetation and these factors shows the distribution of plant communities and it is important step for management of the summer range ecosystems. The present study was carried out in summer rangelands of Behshahr to find the relations between vegetation and climatic factors. According to aerial photos, topographic maps and field surveys; five plant communities were separated by the floristic-physiognomic method. In each community, samples were taken based on random-systematic method. After selecting key areas, plot shape and size was determined using statistical and minimal area methods. Importance value of species, temperature and precipitation data was recorded in each community. The relations between dominant plants of communities and climatic data were determined using ANOVA and ordination techniques. The results show that response of the plant communities to climatic factors was different. Bushy tree community (Rosa iberica) with more humidity and less thermal requirement was independent to other communities and grasses (Festuca ovina, Stipa barbata) due to compatibility with drier conditions were in separated group. Shrubs distribution (Acantholimon pterostegium, Onobrychis cornuta) with medium range of temperature and precipitation showed a group.

Determination of range suitability for different purposes is essential for sustainable development. In this study for determining of rangeland suitability for camel grazing, three sub-models including production model, water model (quantity, quality and distance) and erosion sensibility model were made for final model. FAO (1991) method (recommended for land capability evaluation) was used for suitability classification. The study was conducted in Halvan region in Yazd province. According to the results, 24.1% of area is moderately suitable (S2), 55.4% is marginally suitable (S3), and 20.5% was classified as non suitable (N) for camel grazing. Water distance and accessibility to water, extensive erosion and low available forage is a most declining factor for suitability. Water quality is a limiting factor in part of study area, too.

During the last two decades remote sensing scientists have studied the role of resulting vegetation indices through the satellite data in evaluating the natural resources, These indices have shown high correlations with vegetation parameters. The aim of this study was to evaluate the potentials of spectral indices of MODIS sensor for estimating Semirom and Brojen pastures plant production. Different preprocessings including geometric correction were applied using topographic maps of 1:250000 and the RMSe was 0.8 pixels. Also the atmospheric correction was applied through the dark object subtraction. Field data collection was conducted on the vast areas of about 800,000 ha during the June 2005. The vegetation units with similar floristic-physiognomic-ecologic compositions were considered as an exclusive vegetation type and were sampled with stratified random sampling. The plant production was measured using double sampling method. For this study the June 2005 MODIS data was analyzed. Various vegetation indices were examined on the image and the resulting images were classified to 7 pasture production groups. Finally the produced maps and the sampled points were controlled for their accuracies. The results confirmed the high correlations of used SWIR bands with field data (R2 = 0.85). Also the NDVI, SAVI and RVI plus other similar vegetation indices which employ red or NIR bands had relatively intermediate correlations with pasture data (R2 = 0.6). Overall, the findings of this study prove that the pasture plant production can be estimated using SWIR bands of the MODIS sensor.

In the arid regions, drought and high temperatures occur frequently during late spring and early summer. Vicia peregrina L. is an important legume in arid mediterranean ecosystems which have been grazed by small ruminants mainly sheep and goats. Vicia Seed quality is affected by drought during seed development and maturation and loss of vigor seeds in species my be reducing re-sown forage in arid ecosystems. Therefore, effects of osmotic solution of polyethylene glycol (PEG) on deteriorated seed Percent of germination and seed vigor of Vicia peregrina L. seed were studied. Experiments were conducted in 2007 at agriculture college of university of shiraz. Pods were harvested when the lowest pods were brown in dry land and control(non stressed). because delaying seed harvest of bitter vetch may increase seed losses due to pod shattering. At the final harvesting, germination percentage, hard seeds, shoot length and root length and seedling dry weight at 14 days after planting in standard germination tests were evaluated using different laboratory tests. Germination counts daily after planting was used to calculate the mean time germination (MTG). The results showed that drought stress decreased the seed vigor and osmotic solution had significant effects on seed vigor of Vicia peregrina L. Priming with solutions of PEG had the maximum enhancing effects on germination percentage, shoot and root length and dry weight.

During precipitation event, an area of land is prone to rainfall, but precipitation measuring is only accomplished in few points. So estimating of precipitation in other points can be done in several methods such as: correlation method, normal ratio method, and representative stations and inverse distance method. According to the principle of existing spatial structure among point rainfalls, the less distance between tow points, the less difference in precipitation received by them. The purpose of this research is to find the relationship between distance of two points and depth of precipitation. Then it is possible to estimate the precipitation in points without rain gauges via this relationship. To display this relationship existing rain gauge data in Daryacheh Namak Watershed were used. In this research distances among any rain gauge from others are calculated. Then variations between their monthly precipitations are calculated. Maximum and minimum of the variations are upper and lower limits of variations respectively. The best curve is fitted between variation limits and distance between two points. These equations are calculated at 3 levels of likelihood (80, 90, and 95%) and results are displayed in curves and equations. Using results of this research, it is possible to estimate the depths of precipitation in pointes without gauges by having the data of other rain gauges and the distance from the points to rain gauges. For example: if monthly precipitation in a rain gauge station is "X mm" and other point is "L km" far from this station, this point can receive precipitation between "X + Y1" to "X + Y2". In which "Y1" and "Y2" are the upper and lower limits of difference respectively. By calculating the average the upper and lower limits the monthly precipitation of that point can be estimated. To promote the likelihood, estimation precipitation in the point is possible by many rain gauges data and then calculating the average of results.