Journal of Rangeland
Year:2008 | Volume:2 | Issue:2|Papers Count:11

The current study was carried to find distribution pattern of Zygophyllum eurypterum Ephedra strobilceae , Haloxylon aphyllum and Cornulaca monocantha in Poshtkouh rangelands in Yazd province using distance and quadrat indices. To do this, in a 20 ha area, 4 transects with a length of 400 m were established based on random-systematic method. Vegetation sampling was performed along each of transects .in 30 points. In each point, its distance to nearest plant, distance between mentioned plant and its nearest neighbor, and distance between the point and second plant was measured. Using these measurements, distance indices including; Eberhart, Hopkins and Holgate were calculated. To use quadrat indices, in each of abovementioned 30 points, quadrats with different sizes (according to plant kinds) were established and number of plants within quadrats were counted. Regarding obtained data from quadrats, indices of variance/mean, Morisita and standard Morisita indices were calculated. Results showed that Z. eurypterum, H aphyllum and C. monocantha distribution pattern was random, while E. strobilceae distribution pattern follows a clumped pattern. Also, it was cleared that the accuracy of distance methods was higher than quadrat methods and resulted to more reliable results in determination of plants distribution pattern.

Drought-resistant plants are very important in improvement and development of rangelands. Annual medics are important in restoration of rangelands but little is known about their resistant to drought stress. This study was done to investigate the drought tolerance of snail medic (M scutellata Mill) in germination stage. Polyethylene glycol (PEG 6000) was used to make different levels (-0.2, -0.4, -0.6, -0.8, Mpa) of drought stresses. Measurement of germination factors (percentage, rate and uniformity of germination) was done in petri dish and also the seedling growth (length, dry weight of radicle and hypocotyle) was recorded in paper towel. Results showed that percentage, rate and uniformity of germination and also the length and dry weight of radicle and hypocotyle decreased as the osmotic potential in germination stage increased. We found that in potentials of -0.2, -0.4, -0.6, -0.8, Mpa, germination percentage decreased in relation to control up to 8, 18, 48 and 100%. It can be concluded that this species has a relative tolerance to the drought stress. Results of this study can be useful for rangeland managers who are interested to improve vegetation.

This study originally aimed to assess the relationship between vegetation and environmental factors (climatic and physiographic) in order to find the most effective factors separating vegetation types in Rineh Rangeland. Random Equal-stratified sampling procedure was used for vegetation sampling. 10-20 quadrates were randomly sampled in each homogenous unit. Floristic list, density and canopy cover percentage were determined in each quadrate. Elevation, slop and aspect were physiographical factors. Mean minimum temperature, mean maximum temperature, mean daily temperature, mean relative humidity, month and annual precipitation and freezing days were selected for analysis. Any gaps in the data were estimated by correlation and normal ratio methods. In order to find effective analysis, a range of methods were used including both classification included CA and TWINSPANM classification and ordination techniques (PCA, DCA, and CCA). The TWINSPAN classification of the 75 samples sites have resulted in ten groups. Using PCA 99.348 % of variance was accounted using the first three principal components. DCA axis 1 showed significant correlations with climatic factors and elevation, this suggest that DCA axis 1 represented climatic and elevation factors gradients. CCA analysis explained 16% of the cumulative variances. This result suggest that other factors affect vegetation such as soil and biological factors then should be studied in future researches.

The protection of species diversity is one of the objects of ecosystem management and species diversity has correlation with ecosystem characteristics. Measuring diversity may interpret the species distribution in rangelands and also to help for management recommendation according to the ecosystem dynamics. In this research, we investigate the diversity of medicinal plants in Chaharbagh rural rangelands located in the south of Gorgan, Golestan province. Sampling was done using 90 plots located on 5 transects with random-systematic method. After the identification of medicinal plants, their density in each plot was recorded. Then their family, life span and biological form were determined. Shannon-wiener, Simpson and McIntosh diversity indices were used to determine the diversity. Results showed that the study area has a medium diversity of medicinal plants and species like Gallium verum, Achillea millefolium, Cynodon dactylon and Euphorbia rigida were the most abundant.

Determination of forage quality of rangeland plants is one of the fundamental factors for evaluation of grazing capacity and management of rangelands. Acid detergent fiber (ADF), crude fiber (CF), crude protein (CP), metabolic energy (ME) and dry matter digestibility (DMD) are some of the important factors determining the forage quality. The present study was conducted to evaluate the forage quality of Camphorosma monspeliaca and Echinophora platyloba in Doto-tangsayad of Chaharmahal and Bakhtiari Province. The study area is located in the north east of Shahrekord. During the study, samples were collected from species of C. monspeliaca and E. platyloba with four replications in three phonological stages. The quality indices of acid ADF, CF, CP, ME and DMD were measured at three stages of vegetative growth, flowering and seed ripening (maturity). First, data of quality indices were examined by SPSS software for normality then, these indices were compare at three stages of vegetative growth, flowering and seed ripening for these species by applying one way ANOVA. The results showed that forage quality of these species were higher in vegetative growth than of flowering and seed ripening. Also there was a significant difference between two species in different phonological stages. Better forage quality was found in C. monspeliaca because of greater CPo.

Optimum sample size and the method of sampling for annual yield measurement are very important in measuring the standing crop in rangelands. For this purpose, a key area was selected in the Nir range research station as an indicator of steppic rangelands of Yazd province. Sampling was done using 150 plots (2 m2) on 5 transects where sample points had 25 m intervals. Forage yield were measured by clipping and then weighting in mid-May 2004. Optimum sample size was determined by graphic method based on the biomass data on 10 to 150 plots. Results showed that estimation of total forage yield is possible with clipping and weighting method on 30 quadrates of 2 m2. More accurate estimation for individual species biomass was found with 100 quadrates of 2 m2 and considering 20% CV. This shows that even with 20% CV estimating the annual biomass of individual plants in steppic rangeland of Yazd using clipping method is expensive and time-consuming. To overcome this problem double sampling is recommended with clipping 25 plots out of 1000 plots.

Exclosure is one the most popular tools for rangeland conservation and preventing the rangeland degradation. A total of 87 ranchers were interviewed in this study in Sari. Effective factors influencing the observance of rangeland exclosure and differences between various groups were analyzed using legit regression estimation and X2 test. Results showed that there is a significant difference between groups regarding to the observance of exclosure period. The duration of utilization, monthly income and numbers of livestock were known as the most effective factors. The duration of utilization was the most elastic such that the probability of regarding exclosure period would increase by 0.283 percent while utilization time increase one percent. In other words, regarding exclosure period would increase by 0.013 units if the time of utilization increases. One Rial increase in monthly income and per mutton added to the herd would lead to increase in probability of regarding pasture enclosure period by the amount of 1.979 x 10-7 and 0.008 units.

In this research the ability of artificial neural networks (ANN) method was studied in estimation of daily potential evapotranspiration (ETp) of grass reference crop and then compared with Penman-Monteith method. We used clamatic data for a 5-years period of Ekbatan station in Hamadan. The input data for ANN were maximum and minimum temperature, maximum and minimum relative humidity, wind speed and sunny hours and ETp were set as output data. The best ANN architecturewas selected on the basis of minimizing the root mean square error (RMSE). The architecture of one hidden layer with one processing element gave the least RMSE of 0.7 mm/day and determinationco efficient of 0.84. Whereas, the RMSE and determination coefficient of Penman-Mantieth were 1.2  mm/day and 0.84 respectively. Based on these results, it could be concluded that the ANN predicted ETp better than Penman-Mantieth method. The sensitivity analysis also showed that the minimum temperature and maximum relative humidity had the most and the least effect on input respectively.