فهرست مطالب sedighe zarekia

Astragalus spp. are valuable in forage production, soil protection, etc. To evaluate the establishment and growth of herbaceous milkvetch, 10 genotypes, belonging to five species, including Astragalus vegetus. As.brevidens, As. brachyodontus, As. effusus and As. Cyclophyllus, were studied in Sanandaj in a randomized complete block design with three replications. Seed sowing was done in November 2018, and traits of plant establishment percentage, vigor, height and diameter of plant crown, number of branches per plant, average fresh and dry weight of the plant, and the ratio of dry to wet weight of the plant in 2019 and 2020 years was measured. According to the combined analysis of variance, the effects of genotype and year for all studied traits and the interaction of year × genotype were significant (p≤0.01) except for the percentage of establishment and the plant vigor for other traits. Results showed that seed germination, probably caused by seed dormancy or a stress tolerance mechanism, was gradual. In 2020, the mean of plant establishment was about 37%, the number of primary branches was 7.3, plant height and crown diameters were 35.2 and 35.9 cm, respectively, plant fresh and dry weight were 68.2 and 39.1g, and the dry to fresh weight ratio was 0.58. Results of principal component analysis (PCA) showed that two main components (PC1 and PC2) determined 80% of total variance and genotypes with high forage yield located in the third zone of bi-plot with a negative value of PC1 and mainly positive for PC2. In addition, the accession of As. effusus (West Azerbaijan) and three accessions of As. vegetus (Qazvin, Kurdistan and West Azerbaijan) in terms of adaptation and forage production are introduced as high forage yield and adaptable ones for rehabilitation of rangelands in Kurdistan and similar areas in the country.

The role of different species of Astragalus is important in soil and water conservation, genetic reserve, biodiversity, industrial and medicinal value, and forage production. The genus has been widely spread in different climates due to species diversity and adaptability. Astragalus has increased the vegetative potential of rangeland by increasing soil fertility. Herbaceous species of this genus are highly grazed due to their high protein content and low fiber. According to the reports of the Rangeland Technical Office, the amount of grazing pressure on rangeland is 2.2 times more than the grazing capacity. This amount has been reported up to seven times the grazing capacity in semi-steppe rangelands. Since a large area of rangelands with a rainfall of more than 250 mm has been changed to abandoned drylands, the soil has been exposed to erosion. It seems that more than one ton/ha of forage can be produced by cultivating herbaceous Astragalus in abandoned drylands and degraded rangelands. On the other hand, due to the special characteristics of Astragalus, such as the presence of wide and deep roots, and a relatively large canopy, it is possible to achieve water and soil protection and increase the diversity of species in these areas.

The effects of grazing rest on rangelands are different in different climates and knowledge of these effects is necessary to apply correct management. For this purpose, this study was carried out on the percent vegetation cover (PVC) and forage production (FP) of range species at the Nir Range Research Station in Yazd province as a model of steppe rangelands of Iran. In the study area, different grazing intensities were applied until the end of the grazing season of 2006 and from then on, the whole area was under exclusion. PVC and FP were measured in each of the experimental plots once in May 2007 and again seven years later in May 2014. The results of vegetation data analysis in 2007 showed that the heavy grazing intensity applied in the past caused the reduced PVC and FP of two desirable species i.e. Salsola rigida and Stipa barbata as well as increased PVC and FP of Launaea acanthodes and increased forage production of Scariola orientalis as undesirable species. The results of vegetation data analysis in 2014 showed that the lowest PVC and FP of S.rigida was recorded in the experimental plots under heavy grazing intensity. In other experimental plots, there was no significant difference in PVC and FP of this species (p>0.05). There was no significant difference between PVC and FP of other species and total species in different experimental plots (p>0.05). Thus, during the 7-year rest period, although the negative effect of grazing on S.barbata is resolved, it remains on S.rigida and the resulting degradation is not completely compensated during this period and needs more time. Therefore, S.barbata showed better resistance to grazing as compared with S.rigida. According to the results, if steppe rangelands are grazed heavily in the short-term, intermediate-term grazing rest could improve the vegetation to the previous state.

Rainfall storage with plant species planting is used for rehabilitation and improvement of rangelands, especially in arid areas. In this study the effect of rainfall storage treatments furrow, pitting and crescent pond on the establishment of Ferula tabasensis in Kalmand Bahadoran area of Yazd province was evaluated. This area is one of the habitats of the species studied. Seeds were planted at two season, early fall as autumn sowing and late winter as spring sowing. The research was a split plot design, based on randomized complete blocks with three replications. The main plot was planting time (spring and autumn) and sub plot was planting method (farrow, pitting and crescent pond). The seeds were planted in 2013 and 2014. The results showed that seed emergence rate in autumn were significantly higher than spring planting. Among the planting methods, the impact of the crescent pond method was slightly more than the other two methods. In general, planting methods caused more than 50% seed emergence. Although some of these seedlings were destroyed for various reasons, however, the establishment of about 30% of seedlings shows that the methods of rainwater harvesting in the establishment of cultivated plants have had a positive effect.