مجله مرتع
سال پنجم شماره 2 (پیاپی 18، تابستان 1390)

Biodiversity of rangeland ecosystems directly affects plant species diversity and vegetationcharacteristics, which contributed to ecosystem stability against environmental and biological disturbances. Heavy livestock grazing is a destructive factor lead to elimination sensitive species and reduction of biological diversity. Grazing, affects the rangeland ecosystems by changing the frequency of key plant species which guarantee stability and ecosystem performances. This study has been conducted to investigate the effect of three different grazing intensities on the diversity and richness of plant species in the arid rangelands of Khonj area in Fars Province. Three sites include light, moderate and heavy grazing intensity were selected and sampling was performed using 90 plots (1 m2) along 18 transects. The list of species, canopy coverage and number of individuals per species were recorded for each sampling unit. To evaluating diversity and richness of plant species, Margalef and Menhing richness indices, and Simpson, Shannon and Hill N1 diversity indices were calculated. SPSS software was applied for data analysis and comparison of different indices of diversity and richness among study sites was performed by Tukey test. The results of Margalef richness index showed that there was no significant difference between light and moderate grazing sites, statistically Nevertheless, heavy grazing intensity had significantly different in comparison to light and moderate grazing ones. On theother hand, no significant difference observed among Menhing richness index of diff erent grazing categories (p<0.05). Results of calculations of diversity indices, for all of three Simpson, Shannon and Hill N1 showed that there were not significant difference (p<0.05) between light and moderate grazing intensities. However sever grazing sites were significantly different from two other ones. In general, in arid rangelands such as the studied sites, heavy grazing contributes to reduction in richness and diversity of plant species and affects the ecosystem stability and should be noticed by range managers.

Knowledge in range plant production provides appropriate information in rangelands function andhealth for ecosystem managers. Estimation of range plant production using morphological characteristics increases efficiency of sampling and required time. This study carried out in order to investigate the relationships between plant production and some morphological characteristics (canopy diameter, plant mean diameter, plant height, canopy cover basal area and primeter) of six plant species Stipa henckeriana, Bromus tomentellus, Astragalus effeusus, Astragalus caragana, Astragalus cyclophylus and Onobrychis gaoba considering numerous statistical models which executed in two levels of the plant species and life form. To do so, 30 individuals were randomly chosen in a steppicrangeland in the neighborhood of Zayanderood dam and then above characteristics were measured for each plant species separately. Three groups of statistical models including using only one characteristic (one dimensional model), those using several characteristics (two dimensional models) and multiple regressions were employed. Then selected significant models were validated in order to find best models. The results showed that there were significant relationships between plant production and each characteristic. Basal diameter, basal perimeter and mean canopy cover predicted more appropriately plant production and, conversely, the height as an independent variable did not have significant relationship with production. Furthermore, using two or more morphological characteristics in regression models increased plant production predictions ability compared to those models with one morphological characteristic. The results confirmed that 1) considering two or more characteristics as independent variables may enhance estimation efficiency of plant production 2) estimation of plant production in the normal morphological form is more accurate than in rosette plant such as A. effusus.

To investigate capability of IRS LISS III data for rangelands separation and land usemapping, images of Sorkh Abad area, Mazandaran province related to May 3rd 2007 wereanalyzed. There was not any radiometric noise in the images. Multispectral images were georeferenced to panchromatic band using fifteen control points (accuracy: 0.5 pixel). For image enhancement different image processing techniques such as false color composite (FCC), image ratio, principal component analysis (PCA) and vegetation index were carried out. Pixel base supervised classification was done by maximum likelihood and minimum distance algorithms. Accuracy assessment of maps was done based on ground truth map and error matrix. According to the results accuracy of land use map was 88.53%. Also accuracy of maximum likelihood algorithm (87.05%) was higher than minimum distance algorithm (82.56%). Finally it can be revealed that Liss III images have good potential for land use mapping in the study area.

The effect of grazing and succession stages on seed bank density and similarity between seed bank and above ground vegetation was investigated. The study was conducted in a salt marsh that contained both old and newly created and both grazed and ungrazed habitats. Two old salt marshes were selected to study the effect of grazing on seed bank. One of them was intensively grazed and the other one has never or only recently been grazed. Ten plots of 4m² were used in the new salt marsh and 80 plots (50 in grazed and 30 in ungrazed) in the old salt marshes. Soil samples were collected at two different depths (0-5, 5-10cm) in spring 2006. The soil samples were placedin thegreenhouse to allow viable seeds to germinate. Germination experiments lasted 6 months and all seedlings were identified and removed after identification. Above-ground vegetation composition was determined during the growing season in all plots of selected sites. Results indicated that no significant effect of grazing on seed bank.. According to results seed density and composition had more similarity o vegetation characteristics in early successional stages compared to higher stages. Seed density in soil seed bank was mostly composed of new colonizers during the succession stages while they disappear or decreased intensively and in late succession stage many species were disappeared. In conclusion, the importance of seed banks for conservation of species diversity in degrading rangelands was emphasized.

Increasing disorder in natural ecosystems has increased from growing the amount of carbon dioxide since the industrial revolution until now. Soil, is one of the main sources of stored carbon in hemisphere, and has an important role for balancing and sequestration of carbon dioxide. Considering the vast steppic areas of Iran, studying of carbon sequestration rate is important in these ecosystems. The steppic rangelands of Rudshur were selected as study area. Three treatments including long-term exclosure, medium-term exclosure, and grazed area were selected. Soil sampling was carried out from 0-30 cm depth of plant baseline and inter-distance between plants. Sixty soil samples were collected in each site. Soil samples were air dried and sieved (2 mm).. Measuring of inorganic carbon was done using Walkley-Black method. The results showed that the amount of carbon sequestration in plants vicinity and plants parts had significant differences (P<0.05). The results indicated that inorganic carbon around plants was more than bare soil area between plants in exclosures but it was reverse in the grazed sites. The average carbon sequestration in the medium-term exclosure was 22.45 ton/ha and it had significant differences with long-term exclosure (17.76 ton/ha) and grazed area (18.5 ton/ha) sites.

Proper and efficient management of range ecosystems requires adequate knowledge on grazing intensity and its effects on plant diversity. To compare the plant diversity at reference (RA), key (KA) and, critical (CA) areas of Khabr National Park and vicinities, this study was conducted on an area of 6000 hectares. Plant diversity was determined by using Shannon Index and species richness was determined by rarefaction method. To count species number in 3 locations of RA, KA, and CA, 120 plots of 1 by 0.5 m, and to estimate canopy cover, 120 plots of 2 by 1.5 were used by systematic-random sampling. Expected species richness were 32, 24, and 14 for these areas to provide inequalities of RA > KA > CA. The mean coefficients of Shannon Index was 1.97 in RA, 1.83 in KA, and 1.05 in CA, so diversities of RA and KA were not significant (p>0.05) and both of these areas were significantly different from CA (p<0.05). The species richness in CA was declined considerably due to overgrazing and improper seasonal grazing. Also the proportion of unpalatable species was increased in this area.

Astragalus cyclophyllus, is a perennial plant of leguminosae family which is very palatable forgrazing animals and valuable for apiculture. In the present study the chromosome characteristics and Karyotype of three accessions of Astragalus cyclophyllus were studied. The analysis of distinct mitotic, metaphasic chromosomes involved seed germination, pretreatment of tissue samples, fixation of cellular and chromosomal structures, hydrolyzation of samples, and chromosome staining. Samples were observed icroscopically for chromosome number and morphology which led to the preparation of Karyotype and ideogram of the accessions. The results of the chromosome count showed that all the A. cyclophyllus accessions were tetraploid with 32 chromosomes. This was in agreement with previous report on other Astragalus species containing 32 chromosomes in a tetraploid state. According to the Karyotypic characteristics and Karyotype classificationsfollowing Stebbins method, Hana and Dare Hoze accessions were classified in 2A class and the Sibak accession was classified in 1A class indicating more Karyotypic symmetry. By examining the chromosome length's variation coefficient parameters, the total form percentage, relative length of the shortest chromosome, intra-chromosomal asymmetry index, inter-chromosomal asymmetry index, and the difference of the relative length range, it was specified that the Hana accession had more inter-chromosome symmetry while the Sibak accession had more inter-chromosome symmetry. It is therefore concluded that accessions of this species contain considerable choromosomal variations.

Seed germination is one of the important stages of growth which is a basic requirement for determining optimum plant density in rangeland and farm. This property is affected by many biotic and abiotic factors including ability of genotypes to tolerate water stress imposed by environmental factors. The current research was conducted in germinator to find the behaviour of some Bromus inermis genotypes in relation to water stress at germination and initial growth stages. A split plot design based on randomized completely block design was performed. Genotypes included Alborz 303, Mazandaran 3151, Firouzkouh 3966 and Esfahan 200060. Water stress levels were -3,-6, -9 bars and distilled water. Properties of germination percentage, root & shoot lengths, seedling length, rootlet length to shoot length rate, seedling dry weight, seedling fresh weight, dry to fresh weight rate sprouting rate and seed vigor index were determined during the study. Results indicated that all of the properties, except dry weight to fresh weight ratio of seedling, were decreased due to increase of stress levels. The most decreased ratio was related to change of stress level from -3 to - 6 bar. Among different genotypes, Esfahan 200060 showed the highest germination percentage and had a meaningful preference to other genotypes. From assessed parameters, seedling length and seed index standard showed the most possible reaction to changing water potential. In this study, the best levels to assess resistance to drought were the -6 and -9 bars potentials.

This study aimed to determine vulnerability or persistence of Bromus tomentellus in response to grazing in Saral rangeland. To assess the effects of clipping (simulated grazing) on B. tomentellus, a 0.5 ha exclosure was established before 2007 growing season in Zardawan site. 160 plants were selected randomly inside of the exclosure in which 10 replications were allocated to each treatment.Clipping treatments included control, 25, 50 and 75 percent of annual growth. Clippings were conducted every month during three months of grazing season. Plant materials were air dried and weighted. At the end of growing season, the remaining above ground plant production were clipped except in control treatment and weighted to calculate the intensity of grazing. Vigor, mortality, plant maximum height, yield, and reproductive shoot number were observed or measured during 4 years of experiment. No mortality was observed among 60selected bunches. An in time Split plot design was employed to analysis the data. In quantitative characteristics Light removal of plant material significantly was higher than other treatments.(P ≤ 0.01). Generally it can be concluded that 40 to 50 percent of annual yield removal is safe for persistence and health of B. tomentellus in Saral and other areas with similar climate and soil conditions.

To investigate the forage yield and yield stability of 11 accessions of Elymus hispidus, a field experiment was laid out in a complete randomized block design with three replications, under two conditions (normal irrigation and dryland farming). The experiment was carried out in two years at the Islam Abad e Gharb research station, Kermanshah, Iran. The collection origin of accessions was Sabalan rangelands in Ardabil Province. Results showed highly significant differences (P<0.01) among the accessions and treatments. In addition, the accession×environment interaction effect was significant (P<0.01) for forage yield. Duncan’s Multiple Range Test (p<0.05) revealed that 890-5, 890-6 and 890-7 were superior accessions and cluster analysis classified them into thesame group. AMMI analysis showed that the first significant interaction principal component, explained 97.92% of the total interaction variance. Considering these results, the accessions 890-6, 890-15, 890-5, 890-9, 890-11, and 890-13 showed the highest stability. Stability analysis according to the coefficient of environmental variations(CVi), Wrick’s equivalence(Wi 2), stability variance(δi 2), coefficients of determination(r2) and regression coefficient(b) revealed that 890-5, 890-6, 890-11 and 890-13 had the highest stability among all accessions while 890-7 had the lowest stability. These results demonstrated that accessions 890-5 and 890-6, which had the best, forage yield and yield stability, were suitable for using in future breeding programs in Kermanshahclimate.

Salinity resistant plants are important biotic components of arid and semi arid ecosystems.Aeluropus littoralis is recognized a valuable rangeland plant. Most species of genus Aeluropus are considered halophyte species. Several studies have been done to investigate effects of salinity on halophyte seed germination but there is limited literatures on effect of seed glume compounds on germination at different levels of salinity. Therefore, to understand the mechanism of germination in Aeluropus littoralis and also to find the effect of seed coat on germination rate at different concentrations of salinity, an experiment was done in complete randomized factorial design with three replications. For this purpose, six salinity levels (50, 100, 150, 200, 300 and 400 mM) and two seed coat conditions (with glume and without glume) were applied. The results showed thatincrease salinity levels leads to decrease in germination properties in both seed coatconditions.Seed without glumewas affected more than glume ones. The salinity-glume intraction was also significant at 5 % probability. The result of chemical analysis of methanol extract of glumes through GC-MS, revealed the existence of allogibberelic acid,a derivative of GA3 phytohormon in glumes. This compound was considered as an important factor for germination differences between glume-containing and without glume seeds under different salt treatments.

Livestock exodus from Mazandaran forests is always a problem for natural resources decision makers in province and the country. Irregular grazing in forest lands of Mazandaran province has been resulted in deterioration of many of natural resources including forest lands. This study, with the aid of quality function approach such as Logit Regression Model investigated the effect of social-economic factors in livestock exodus from the Forest in Mazandaran province in 2009. Therefore, variables such as annual’s income of rancher, number of jobs, scale of family, experience of ranching, preservationimportance of natural resources, age of ranchers, participation in rangeland management projects, importance of preserving period and education of rancher were investigated. Results showed that variable of ranching experience had most elasticity in which by one percent increase in this variable, probability of livestock exodus will be increased to 0.389 percent. According to marginal effect statistic, with increasing one year to rancher experiences, probability of livestock exodus will be increased up to 0.029 units. Also with increasing every 1000 Rials in monthly income, exodus probability will be increased up to 0.00018 units. According to the results, by addition of every year to the education level, probability of livestock exodus will be increased to 0.021 units. On the other hand, by addition of every individual to the scale of family, exodus probability will be decreased about 0.049 units. Also variables of preservation importance of natural resources, participation in rangeland management projects and level of respecting of preserving period of rangelands positively and significantly will affect the willingness of rancher to exodus from the forest.