Journal of Rangeland Science
Volume:2 Issue: 3, Spring 2012

Overgrazing, via harvesting of forage species and decrease the other herbs, is of progressive factors in biodiversity destroying. In order to investigate the animal grazing impacts on changing of plant structure and diversity, we selected the comparison between this effect with exclosure area, and proving of the excluded area effects on plant diversity; two sites of Kojour rangeland, Mazandran province, Iran. Four transects, 50 m were systematic-accidentally established on two different aspects including along of slope (two transects) and staple on steep slope side. Cover percentage was recorded by 10 plots 1m2 in each transect. Rangeland condition and trend was determined by 6-factor and Trending Balance methods, respectively. Diversity indices in each area, by analysing of vegetation parameters, were calculated using PAST software. Vegetation traits and bioindicators were analysed by independent T-test using SPSS software. The result showed that percentages of all life-forms in rangeland were different between the exclosure and grazing areas, especially, grasses and forbs were meaningfully remarked. Regarding to bioindicators, diversity-Shannon index and richness-Menhinick index values were higher in the exclosure area than open area (P<0.01). Dominance index in grazing area was significantly higher than exclosure area (P<0.05). Evenness index, however, has not punctual difference in both areas.

The study of the relationships of the plant species with the soil in a salty ecosystem would play a significant role in the ecologic programming and management of these inhabitants. The saline and alkaline rangelands of the Golestan province are areas that contain salty soil with high underground crusts. The areas are covered by halophyte plants such as Frankenia hirsuta. This species is a perennial plant from the Frankeniaceae family. They could absorb salt from soil and store it in their organs in order to reduce soil saltiness and restore slat of lands. Thus, in order to determine the percentage of sodium chloride of such species, sampling was taken in the flowering stage from two exclosure and grazing areas by six replications. Then, the percentage of Sodium Chloride (NaC1) was measured in the lab using the titration method. The statistical analyses and the comparisons of the means of the collected data were made by the use of T-test. The results showed significant difference for NaC1% of the phytomass of the species (P≤0.01). The average value of NaC1 was 2.13% and 1.37% for the exclosure and grazing area, respectively. In the other word, the highest and lowest values of NaC1% were obtained for exclosure and the grazing area, respectively. It was concluded that Frankenia hirsuta can take in the soil salt and by gathering or grazing, it could led to reduction of soil saltiness.

The use of metal-accumulating plants to clean the contaminated soil with toxic metals is the most rapidly developing component of phytoremediation as an environmentally friendly technology. Overcoming harsh soil conditions and accelerating the recovery of degraded soils remain a worldwide restoration challenge. This study evaluated the effect of different concentrations of Pb, Zn, Cu and Fe on the germination, growth and heavy metal uptake of Hordeum bulbosum L. Results obtained from the current research indicated that the plant gives dose-dependent responses to the contaminated soils. Reduction in germination, root and shoot height and biomass were significantly (P<0.05) different as compared to the control. Exposures of heavy metals in the treatment reduced the size of roots and shoots about 8.68% and 5.05% respectively as compared to the control. However, the concentration of heavy metals was increased at treatment four, the sizes of root and shoot are the same at two and three treatmens. Heavy metal concentrations were significantly higher in the root tissue than aboveground components and plant organs demonstrated a different affinity to take up heavy metals. In all the plant organs, the concentrations of heavy metals increased as the metal contents in the soil increased.

In order to study the variation for seed yield and its components, 200 accessions of alfalfa (Medicago sativa L.) were sown as drilled plots, using alpha designs/unreplicated with two repeated entries with in all of 10 blocks under dry land farming system in Kabodarahang Research Station, Hamadan, Iran, during 2010 to 2011. Data were analyzed for descriptive statistics, correlation, regression, path analysis, factor analysis and cluster analysis. Results showed considerable variation for all of traits. The best 20 entries were identified. Among them, Cody, Kerissary, Italian, Australian, Hamadani, Bami, Jirofti and Faridonshahr with average values of 900 to 1250 kg ha-1 forage yield and 85 to 107 kg ha-1 seed yield were introduced for breeding improved synthetic varieties. Results of correlation analysis showed that DM yield was positively correlated with node number, plant height, stem number, vegetation score, seed yield, and pod weight. Similarly, seed yield had positive correlation with pod weight, DM yield, vegetation score and plant height. Results of path analysis showed that DM yield and pod yield had higher direct and total effects on seed yield. Results of factor analysis were accounted for 77% of total variation for first five factors. Factor 1 which was accounted for 25% of variation was associated with DM yield, seed yield and pod yield. This factor was regarded as productive factor. Factor 2 accounted for 14% of variation was known as stem elongation factor, since it was included for plant height and node number. Based on ward cluster analysis method, 200 entries were divided into 5 groups. Accessions in cluster 4 were averaged well above the overall mean for DM and seed yield. The results of this study indicated that selection of variables in productivity factor (factor1 and cluster 4) could enable breeders to release the desirable increment in forage yield of alfalfa.

Increasing the concentration of atmospheric carbon dioxide is the main factor for the climatic change having some harmful consequences for the human health while there is no considerable effort for decreasing this accelerated global problem, yet. Kermanshah province located in the west of Iran has about 1,200,000 ha rangeland which is dominated by Astragalus spp as the more frequent shrub beingable for the carbon sequestration and more than 80%, its biomass has a key role in the carbon sinking into the soil layers. In order to investigate the effects of topographic factors on carbon sequestration, this study was conducted in the Bazan rangeland of Kermanshah province as the representative site. This site is characterized by the indigenous vegetation of rangeland. The maps including topography, vegetation and date layers were digitized by GIS (Arc GIS 9.1). In each homogeneous area of representative site, two or three linear parallel 30 m intervals were randomly established along the slope length and plant sampling for biomass was doneusing a quadrate plot (1×1 m) with 10 m plotting intervals. In addition, the highest rate (118.68 kg/ha) of sequestered carbon was observed in the altitude of 1900-2100 m above sea level in the northern direction while the lowest stored rate (39.13 kg/ha) was found in 1100-1300 m in the southern direction.

The superficial strata of ground have been perennially exposed to the action of natural agents such as heat, cold and water. However, grazing agent was not different from them when soils were investigated from temperate rangelands of Kashmir and caused the soil compaction, soil structure degradation and loss of soil organic C and C/N ratio. Soils from three grazing intensities were investigated for physio-chemical parameters. The results showed that soil bulk density was the lowest in Low Grazed (LG) areas and critical in Highly Grazed (HG) areas. The results revealed that C storage in 0–10 cm of soil layers was decreased linearly with the increase of stocking rates. However, total soil nitrogen content in HG is 1.26 times more than LG. Therefore, grazing is responsible for major changes in the physical and chemical properties of the topsoil which may further cause the spatial heterogeneity followed by regional ecological problems.

In this study, some habitat characteristics of Iranian rose (Hulthemia persica) were studied in Gonbad watershed in Hamedan providence, Iran. Soil samples were taken by a systematic randomized method at elevation 2000-2400 m above sea level. Samples were taken from 0-30 cm depth. In the laboratory, N, P, K% and organic matter (OC%), soil acidity (pH), conductivity (EC) and soil texture were determined. The collected data were analyzed and principal components analysis was performed on 14 variables using PC-ORD software. Results showed that these species are scattered in the height of 2100-2300 m above sea level with 15-65% slope in North, Northwest, Southeast and Southwest as spot bulks. Mean precipitation of this area is 227.5 mm. It’s vegetative, flowering and seed maturity stages occur in middle March, May and June, respectively. Plant roots permeate into the depth of 1.5 m and plant propagated by both seeds and rhizome. However, its seed has hard coat resulting in a difficulty in germinating so that the seed propagation is not sexual and it propagated normally by rhizomes. This species growth in the soil with EC=0.08-0.36, pH=7.30-7.98, limestone soil 0.50-19.5%, OC=1.09-0.27%, saturation (SP%)=18.3-38.2%, N=0.02-0.10 %, P=4.8-40.6 ppm, K=155-652 ppm, and the soil texture was clay to clay-loamy. Results of PCA analysis indicated that the first three axes explained total variation. The variables of SP, EC and slope were positively and silt and aspect were negatively correlated with the first axis. The variables of SP, pH and OC% were positively and sand and N% were negatively correlated with the second axis. Indicating that by increasing sand properties the pH values will decrease. There was also a negative correlation between vegetation coverage and slope (P<5%) suggesting land coverage reduction by increasing the slope. Height, slope and aspect had the highest influences on the species distribution. This plant as an invasive and non-palatable plant can form a type and be developed in the agriculture boundaries and pastures as a wide band.

Infiltration rate of water into the soil depends on the factors such as rock and litter cover, canopy cover, rainfall intensity, coarse material, land slope, soil texture and amount of initial soil moisture. The most important factors that are effective in the water infiltration rate of rangelands are livestock trampling and vegetation reduction due to the overgrazing. In present study, through drawing a curve of number dung distance from the fold, three areas were determined as heavy pressure grazing (A), fixed grazing (B) and without grazing (C). The soil samples were taken and soil density was determined. Results of analysis of variance showed a significant difference between soil densities in all three grazing zones (P<0.01). There were also significant differences between soil densities of patches and bare soil (P<0.01). Results showed significant differences of patches in the range of severe grazing and bare soil in the same range (P<0.01).

This study aims to assess the effect of grazing intensity on vegetation structure, soil nutrient concentrations and soil physical properties. The study was carried out in steppe rangelands of Saveh, Markazi province, Iran. Four sites with four grazing intensities including very high, high, moderate and non-grazed with the same ecological conditions were selected. To study various vegetation and soil parameters in each range site, a reference area was selected. Then, sampling was performed by randomized systematic method in reference areas. Vegetation characteristics, soil physical properties, bulk density, infiltration rate, soil texture and chemical constituents including nitrogen, phosphorus, potassium, pH, EC and organic carbon were measured. Principal component analysis was performed on a dataset with 22 variables to determine the effect of grazing intensity on vegetation structure and soil properties. Results indicated that the first three axes explained the total variation. The variables of potassium, phosphorous, bulk density, class I, class II, clay, field capacity, infiltration, Peganum harmala, Salsola laricina, Artemisia sieberi and perennial forbs had significant correlations with the first axes and explained a 74.27% variation. For the second components, silt, sand and perennial grasses were more important traits and explained a 15.5% variation. In non-grazed and moderate grazed sites, there were more canopy cover of both Artemisia sieberi and Salsola laricina, and for high grazing sites, there were plants of class III such as Noaea mucronata and Peganum harmala. The grazing intensity was associated with lower values of infiltration, clay percent and field capacity and higher values of bulk density, potassium, phosphorous and sand percent. Therefore, vegetation structure and soil properties were changed by the interaction between grazing intensity, soil properties and vegetation structure. The results suggested that excluding grazing livestock on the arid steppes has a great potential to restore vegetation and soil. Therefore, it must be encouraged as an alternative to stop further degradation and to combat desertification in arid and semi arid ecosystems.