Journal of Rangeland
Year:2012 | Volume:5 | Issue:4 (20)|Papers Count:14

Direct biomass measurements such as clipping method is difficult, destructive and time consuming. This research was performed to study possibility of Sphaerocoma aucheri forage production using some vegetative traits (such as cover characteristics including its area mean diameter, small diameter, large diameter and height of the plants). Dry forage production and some independent variables were randomly collected, from 50 plants of S. aucheri in a 4 years enclosure sites in Hormozgan province. After eliminating the outlier data and conducting normal test, multi variables regression in SPSS package was used to analyses data. The results showed that 77% changes in dry biomass of the species can satisfactory be estimated using canopy cover data The coefficient of cover area and constant index in regression model were 3.192 and 6.283 respectively. Validated model revealed that Sphaerocoma aucheri dry forage can be estimated properly measuring canopy cover of the species.

In this research, the effects of some topography and soil factors influencing vegetation structure have been studied in Chal Kabud basin located in the northern slope of Oshtorankouh. It enjoys the greatest altitude variations, a rich diversity of plant species as well as topographical features. Nineteen altitudinal classes were identified by 100 m altitudinal interval. In each altitudinal class, 4 transects (2 vertical and 2 horizontal) each with 200 m length were established and 8 quadrates were sampled alongside each transect. In selected classes along the homogenous units, soil profile was dig and some edaphic parameters were measured. Vegetation characteristics and grazing intensity of all units also were studied. Fourteen vegetation classes were classified by TWINSPAN and plant species as well as sampling sites were analyzed and grouped by Dterended Correspondence Analysis (DCA) to 4 and 6 similar categories, respectively. In order to study the effects of environmental factors on vegetation, Canonical Correspondence Analysis (CCA) were applied and correlation among each environmental factor and plant species were measured. CCA results showed that edapic factors were the most effective factors on distribution and establishment of plant species in the study area and altitude, slope and grazing intensity were among the next important factors respectively

Eurotia ceratoides (L.) C.A.M. is a perennial and palatable range plant species with high grazing value. This species rarely dominate the rangelands and is mostly growing with other species. Ecological-niche factor analysis (ENFA) is a multivariate approach to study geographic distribution of species on a large scale using “presence” data of the species. This method was used to map potential habitat of E. ceratoides in North East of Semnan province. The presence points of the species were considered as appropriate places for its growth. Habitat characteristics of the species such as Soil & Physiography were identified. Fifteen quadrates were placed at an interval of 50 m along three 750 m transects in each vegetation type. Soil samples were taken from 0-20 cm and 20-80 cm in starting and ending points of each transect. The exact geogerafic position of E. ceratoides plants along the transects were recorded by global position system (GPS) then actual vegetation map of the studied area was produced. The essential data layers were imported to appropriate model and statistical analysis were performed by Biomapper software to map potential habitat of this species. According to the results, 15000 hectares (about 20 percent of the study area) was recognized as potential habitat of E. ceratoides. Accuracy of the model was tested using Boyce index which was about 93.2 percent. The model was verified using kappa statistics and the calculated kappa index was about 0.85. Habitat characteristics of the species revealed that E. ceratoides, is distributed in sites with 7.8-8 pH, 0.17-0.26 EC ds/m, silty-sandy texture and in 1600-2200 meters elevation from sea level.

There is a divergent of views about the relationship between vegetation and soil characteristics in different habitats. In addition, there are limited studies about the relationship between soil seed bank and soil characteristics. This study aimed to investigate the relationship between three edaphic factors (texture, EC and organic matter) with vegetation and of soil seed bank composition. Therefore, 50 plots (2 × 2m) were established on a salt-marsh site in spring. Soil samples were collected (from two different depths (0-5 and 5-10cm) to determine the composition of seed bank and perform soil chemical and physical analysis. In addition, the composition of above-ground vegetation was estimated in the growing season. Soil seed bank composition was determined in the greenhouse through a seed germination experiment. Multivariate analysis (ordination) and step-wise regression were performed to analyze the data. The results showed that EC and organic matter had a significant effect on the vegetation distribution, while these effects were less pronounced for soil seed bank composition. The cover of dominant species was affected by soil texture but edaphic factors had no significant effects on the soil seed composition and the seed density of dominant species.

In range management practices it is impotant to understnd growing and production of key speceis as well as changes in their preference values according to seasons and habitat characteristics. The aim of this study is comparison of preference values of Festuca ovina species at different times and different regions of semi- steppic rangeland of Iran in 2006 to 2009. Random sampling with one square meter frames was emplyed to study vegetation during different growing monthes. Preference index method was used to determine the preference value of F. ovina. To calculate preference index, the ratio of the species in the diet and in the species composition were used. To compare preference value in different places and times randomized complete design with combined analysis in year and place was conducted. The results showed that among the studied sites and between the months are significant difference at α=0.05. Changes in preference values of F. ovina indicated that value of preference of this species increased until August and then decreased in September.

Seed availability is essential for biological reclamation projects. Proper seed harvesting time is an important factor to ensure maximum seed viability and to avoid collecting immature or dehiscent seeds. This study aimed to investigate the optimal seed harvesting time of three range plants including Cymbopogon olivieri, Stipa parviflora and Stipa barbata in Yazd province during growing season of 2007. Seeds were collected periodically from physiological maturation time to seed shatter stage. At each collected time 400 seeds were dried and were used in 4 replications for viability test. The experiment lasted for 21 days in completely randomized design. Treatments included species and different harvesting times (four times for S. parviflora, six times for C. olivieri and three times for S. barbata). Duncan mean separation test was performed by SAS program to analysis the data. According to the results, different harvesting times in all three species had significant differences (p≤0.01). Seeds of S. parviflora collected on May 24 had highest germination percentage (93%) and the least occurred on June 7 (63%). Seventy percent of C. olivieri seeds collected on May 11 were germinate seven percent seed of collected S. barbata on June 13 were germinated showing highest germination percentage for treatments. Collected seeds of C. olivieri and S. barbata had minimum germination percentage on June 8 (28%) and June 6 (25%), respectively.

Change detection in plant production, canopy cover and importance value of dominant plant life forms during growing season can assist range managers to select appropriate management practices. This research carried out during 2008-2009 in Nodushan rangelands in Yazd province. Random sampling with one m2 plots was used to determine importance values of available plant life forms including grasses, shrubs and forbs. The measurements were conducted in early, mid and late stages of growing season. According to the results, shrubs had higher importance value than grasses and forbs during the growing season. The importance value of shrubs was increased during growing season but this index was decreased for grasses and forbs. Canopy cover and forage yield of all studied plant life forms had significant correlation during growing season (P<0.05) and R square value were 0.84, 0.78 and 0.67 for forbs, shrubs and grasses respectively. Therefore in spite of minor changes of importance value during growing season, significant relationships between plant cover and production justifies the estimation of range production from vegetation cover data.

The aim of this study was to investigate the effects of animal grazing on plant community composition and diversity. Some diversity indices in three grazing treatments (exclosure, moderate grazing and high grazing pressure were compared in steppic rangelands of Borojen, Chaharmahal & Bakhtiari province. Random-systematic sampling method was used and plant species cover were estimated. The a, b, Chanon and Simpson indices of all studied sites were calculated and then compared using one-way analysis of variance. Moreover, the Non metric-multidimensional scaling and Multi-Response Permutation Procedures were used to reveal changes occurred by animal grazing treatments in plant community composition. The results revealed that, although livestock grazing decreased the numerical values of Chanon, Simpson andα diversity, b diversity increased under heavy grazing. A higher b diversity in heavy grazing may be interpreted as providing favorable condition for unpalatable plant species growth which provides more heterogeneity for plant community. Furthermore, results showed that grazing was the main factor responsible for changes in plant community composition. The results indicated that though the exclosure may be an ideal management option, the short-time exclosure (moderate grazing pressure) is also likely to restore plant community composition and diversity.

Satellite images are currently used as a fast and low-cost tool for rangeland assessment. In this study, 10 vegetation indices from different groups were calculated using spectral bands. The correlation of these vegetation indices with canopy cover was then measured for three vegetation types in Semirom region-Isfahan. The percentage of canopy cover and other earth surface components such as litter, rock, gravel, stone and bare ground were determined using step-point method. Ten random points were selected in each vegetation type and four 150 meters transects in two perpendicular direction were established from each point, therefore 6000 points were studied per rangeland type. Ten different groups of vegetation indices including slope-based, distance-based and plant–water sensitive indices extracted from IRS-P6 satellite data (AWiFS sensor) were evaluated against total ground cover. The results indicated that vegetation indices have higher relationships within vegetation types based on their characteristics but the correlation for each vegetation index was not consistent among different types. Considering all photosynthetic vegetation cover, the correlation between these factors and vegetation indices were much higher than degraded sites due to greater reflectance from bare soil and less photosynthetic area. In general, the results indicate that each vegetation index is appropriate for mapping a specific vegetation type and we should consider this issue in mapping and monitoring vegetation cover.

Rangelands are the main food supply for the livestock of nomads in Iran. The nomadic of Iran leads to a self- dependent lifestyle by livestock on rangelands. The proportion of contribution of rangelands in household’s income of nomadic life is yet to be determined. So the results of this study seem to be of great importance regarding the recognition of the fundamental role of rangelands in the nomadic economy. In this study the number of livestocks, pure and impure income, livestock expenditures and income of nomadic pastoralists, other incomes from rangeland products, forage utilization as well as other livestocks requirements of the utilizers were studied. The data of this study have been collected through questionnaire filled out by 50 randomly chosen nomads’ pastoralists from Homian basin in Koohdasht town in Lorestan province. To analyse the results one - way ANOVA and the mean comparison of multi dimension DUNCAN test have been used. Based on the results, the rangeland share in nomads' income proved to be over 70 percent of their stockbreeding income and the findings is an indication of economical reliance of nomadic pastoralists on rangelands.