mohammadreza najibzadeh

In this research, the preference value of rangeland species in Sahand rangelands of East Azarbayjan province was studied for four years (2007-2010). The preference index method was used for this purpose. After determining the amount of production and consumption of each species selected in the grazing season (June, July, August, and September) and calculating the share of each species in the forage production of the region and livestock feed, and calculating the preference index, the data analyzed in split-plot design based on the completely randomized design in SAS software. The results showed that the effect of the year in three species, the effect of the month in four species, and the interaction of year and four species at (p≤0.01) were significant on the preference index. The preference index is a very important factor in determining the preference value of plant species for livestock. The species of Festuca rubra, Tanacetum chiliophyllum, with an average preference index of 1.4 to 1.6 during four-year, has a relative preference and is a relatively benign species and was placed in the palatable class I. Tanacetum chiliophyllum, with the highest average preference index, was ranked first among all herbaceous species. The species of Bromus tomentellus, Festuca ovina, Alopecorus textilis with an average preference index of 0.7 to 1.2 were of moderate preference and were classified as moderate in palatability and classified in the palatability class II.  Astragalus aureus, with an average preference index of about 0.3, had a relative preference, and this species was almost non-chewed and ranked in the palatable class III. Overall, the results of this study showed that the preference value of Festuca rubra and Tanacetum chiliophyllum was more than the other species, and the sheep preferred the forbs, followed by grasses and shrubs for sheep grazing.

Due to the decreasing trend of rangelands, many native species are vulnerable and even at risk of extinction. Therefore, seed preservation and propagation of native species of rangelands and recognition of the characteristics of grazing, drought tolerance and their production potential are very beneficial. In this study, the five species of Festuca ovina, Festuca rubra, Bromus tomentellus, Alopecurus textilis and Thymus kotschyanus, which are the key species of Sahand Rangelands in Eastern Azerbaijan province, were studied. Treatments in each block included four grazing intensities, namely 25%, 50%, 75% and the control (no harvesting). The harvest was performed during the growing season and at the beginning of the grazing season for four years (2007-2010). Results of statistical analysis showed that the effect of harvesting intensity, year and intensity by year interaction were significant for forage production of F. rubra, B. tomentellus and A. textilis (p<0.01). However, the effect of year and intensity for T.kotschyanus and the effect of year for F. ovina were not significant. Results showed that forage production of species was different in years. Higher forage production in 75% harvest intensity was obtained in B. tomentellus, F. rubra and A. textilis with average values of 15.8, 18.1 and 16.7 g/p, respectively. In latter species, forage production was much affected by climate changes rather than the harvest intensity. The highest forage production of F. ovina was obtained in light harvest. Increasing the harvest intensity may decline plant vitality. It was recommended that allowable grazing intensity of Sahand rangeland might be 25% up to 50% harvesting intensity for preserving these species.

Acantholimon gilliatii, Astragalus aharicusand A. neo-mobayenii are the endemic species with one population in East Azarbaijan. Previous observations of researchers have shown that survival of these species at risk and their distribution is being limited. In this study, topographic, climatic and soil characteristics were investigated in habitats of these species. Also, coverage, height density and phenology of the study species were determined by using 10 plots in each area with random method during 2013 and 2014. The habitat of A. gilliatii is very limited in the southern slopes of the Mishodagh Mountain, with a slope of 15-30 %, an altitude of 2010 m, loam-sandy soil and cold semi-humid climate. Also, the habitat of A. aharicus is very limited in the southwestern slopes of the Kasabeh Mountain, with a slope of more than 60 %, an altitude of 1750 m, loam-clay calcareous soil and semi-arid climate. The habitat of A. neo-mobayenii is patchy in the northern slopes of the Mishodagh Mountain, with a slope of 60-70 %, an altitude of 1800 m, loam-sandy soil and cold semi-humid climate. It seems that droughts and heavy livestock grazing have resulted in limiting the populations of the study species. Therefore, adopting measures such as protecting the habitat of these species, investigation of the factors affecting the regeneration of these plants as well as pest control are essential to avoid the removal of these species from the natural arena.