مجله مرتع
سال ششم شماره 3 (پیاپی 23، پاییز 1391)

This research was conducted to study impacts of various grazing intensities on aerial and belowground biomass and dimensional characteristics of three important grass species in Chahar Bagh mountain grasslands in Golestan Province. Samples of three palatable and indicator grass species including Bromus tomentellus, Stipa barbata and Festuca ovina were selected in three sites of no grazing, moderate grazing and heavy grazing. Five parallel 100 m transects were established and 2 random points were determined on them and then 10 nearest plants to the points were selected. In next step, dimensional characteristics, above and belowground biomass of three grasses were measured. ANOVA test and Duncan test were used to compare dimensions and biomass parameters of plant ¬species. Results indicated significant differences ¬of above and blow ground biomass among the three species in all sites; as such high and low level of aboveground biomass belong to B. tomentellus with 46.95 and 1.86 gr for no grazing and heavy grazing sites respectively. The maximum and minimum belowground biomass of B. tomentellus was allocated to the no grazing and heavy grazing areas with 64.12 and 2.6 gr respectively. Also the results showed that long-term excessive livestock grazing on the study area lead to 12.75 and 31.3 cm declining of root depth and height of Br. tomentellus in relation to no grazing area. In other hand no grazing site compared to heavy grazing site, the canopy cover of B. tomentellus, F.ovina and S. barbata declined about 103,185.42 and 48.22 square cm which leads changing ecosystem structural characteristics and plant community dynamics. Considering to the changes of growth characteristics of B. tomentellus and F.ovina species, it seems that the high changes in characteristics of these species are related to palatability and preference value of this species.

Some range restoration activities, such as interseeding forage plants within the pits (Kopekari), lead to small scale disturbance of soil surface and rangeland vegetation, which may subsequently provide spaces for invasive plants. This research was aimed to investigate the effects of local disturbance, created by a Kopekari project, on the plant species diversity and richness, in Kranakh rangelands, Germeh, Northern Khorasan Province. In autumn 2009, a forage perennial grass (Agropyron desertorum, had been sown under the canopy of four rangelands shrubs (Astragalus gossypinus Fisch., Acantholimon ptereostegium Bunge, Artemisia kopetdaghensis Krasch., and Salsola arbusculiformis Brob.), under straw or stone mulches, or in open areas. Three years later (spring-summer 2011) species diversity was simultaneously assessed within the Kopekari pits or in the adjacent undisturbed areas. Plant sampling was conducted via a systematic-randomized design, in which species abundances were counted within 180 quadrates. Results indicated higher plant diversity (Shannon) within kopekari pits under the canopy of shrubs as compared with those in open areas (2.53 vs. 2.35). Straw mulch could preserve the plant diversity but the stone mulch had a negative effect. The effects of shrubs were also variable, Acantholimon increased (0.69 vs. 0.6), Astragalus decreased, but Artemisia and Salsola showed similar diversity (Simpson) under the canopies as compared with the control treatments. In conclusion, using straw mulches or seeding under the canopy of cushion-like shrub species is useful for restoration of plant diversity, at the Kopekari projects.

This study has been performed in order to determine the effect of clipping intensities of important perennial grasses on the forage production. These experiments have been conducted at the exclosure of Saraliabad Gorgan rangelands. For clipping intensity 25, 50, 75 percent and control (without harvest) have been applied as main factors. In each clipping treatments, 10 individual plant of each species were assessed as replications. Results were analyzed by SAS software in split plot statistical design base on randomize complete design with ten replications at four years (2006 to 2011). The results indicated that there were significant differences between years, intensities of clipping (exception Bromus tomentellus) and their interactions (P<0.01). Generally Agropyron intermedium, Agropyron trichophorum and Poa angustifolia are sensitive to low rainfall and drought, therefore the forage production of these species reduced from 46 to 57% particularly in first year of drought. On the other hand, Festuca ovina showed more resistance and clipping intensities had not significant effect on forage production in dry years. Koeleria cristata and B. tomentellus clipping increased forage production (5 to 33% compare to control treatment) in years with high precipitation and reduced forage production in dry years (4 to 49% compared to control treatment. According to the results of clipping intensities have been determined 60% for F. ovina. In dry years the results showed no grazing for both A. intermedium and A. trichophorum and light grazing (25%) for P. angustifolia but in wet years any limitation of grazing for both A. intermedium and A. trichophorum and light grazing for P. angustifolia have been suggested. No limitation of grazing have been determined for both K. cristata and B. tomentellus in wet years but for dry years clipping intensities estimated 50% and 25% respectively.

In order to investigate the efficiency of biological fertilizers, mycorrhiza and sinorhizobium and nitrogen chemical fertilizer on growth of annual medic (Medicago scutellata), an experiment was conducted in the research farm of faculty of agriculture in Shahrood University of Technology. The experiment was carried out during growing seasons of 2010-2011, as a factorial experiment based on randomized completely block design. The factors were nitrogen fertilizer (0, 75 and 125 kg/ha), mycorrhiza (without inoculation and inoculation of Glomus intraradices) and sinorhizobium (without inoculation and with inoculation of Sinorhizobium meliloti) in four replications. The results indicated that effects of mycorrhiza, sinorhizobium and their interactions were significant on shoot dry weight, pod number and pod dry weight and dual inoculation mycorrhiza and sinorhizobium increased shoot dry weight and pod numbers 27.68 and 30.11 percent compared to control respectively. The interactions of nitrogen fertilizer, mycorrhiza and sinorhizobium were significant on shoot dry weight, root dry weight, pod dry weight, pod numbers and stem lengths. Highest results were obtained with 125 kg/ha nitrogen fertilizer, mycorrhiza and sinorhizobium inoculation. The results showed that shoot dry weight in mycorrhiza and sinorhizobium treatment associated with the application of 75 kg nitrogen fertilizer were equivalent to 125 kg of nitrogen fertilizer. Nitrogen fertilizer decreased percentage of root colonization 37.71 percent compared to control. Therefore to avoid the negative effects of high amount of chemical fertilizers on soil microorganisms, inoculation with mycorrhiza and sinorhizobium can be used to reduce application of chemical nitrogen fertilizers.

This research has been conducted to evaluate digestibility, degradability of dry matter and protein contents of two rangeland species, Phloem pratensis and Paspalum dilitatum by Nylon Bags and Gas Production methods. A randomized complete design with three fistulated sheeps with three replications and two treatments were used to conduct the research. The data were analyzed by dependent t-test and GLM. According to the results, crude protein was significantly different between P.dilitatum (13.8%) and P.pratensis (8.6%), while Neutral Detergent Fiber (NDF) and Acid Detergent Fiber (ADF) did not show significant differences. Digestibility and degradability of dry matter and Protein in P.dilitatum was more than P. pratensis in the all incubation times by Nylon Bags and Gas Production methods. Nylon Bags and Gas Production Methods indicated a high correlation with degradability of dry matter and Protein, (93%) and (95%) respectively, and showed that the Gas Production Method could be supersede to Nylon Bags Method for degradability of forage. The results revealed that quality of P.dilitatum with crude protein (13.8%), degradability of dry matter (84.32%) and protein (93.14%) is more than P. pratensis with crude protein (8.6%), degradability of dry matter (62.7%) and protein (78.5%) statistically. Moreover, the two species could provide some part of livestock ration.

Balancing livestock nutritional requirements and rangeland nutritional contents is a key to achieve a sound management in rangeland ecosystem. This study aimed to evaluate Nodooshan goat daily forage requirements. The weight of adult livestock in this goat breed has been estimated as 30 kg. Forage quality of the dominant species including Artemisia sieberi, Salsola kerneri, Aelienia subaphylla & Eurotia ceratoides were measured in vegetative, flowering and seed ripening stages. Metabolisable Energy (ME) of collected samples were measured and variance analysis was conducted. Mean comparison tests were conducted using Duncan's method. The results suggested that the ME contents of studied species were significantly different (α= 0.1 %) in various phenological stages, hence the required forage quantity varies accordingly. Daily forage requirement of this breed was estimated 60 percent more than it's calculated amount by NRC table and MAFF equation due to inappropriate environmental conditions of the studied rangelands. The daily ME for this animal was calculated 9.54 and 8.64 MJ based on NRC table and MAF equation respectively. Considering forage quality of the studied rangeland species and the Nodooshan goat energy requirements based on NRC table and MAF equation, the required daily forages varies respectively2.26 to 2.04 kg in the vegetative stages, 2.91 to 2.64 kg in the flowering stages and 4.38 and 3.97 kg in the seed ripening stages. According to the results, the studied rangeland species in vegetative and flowering stages can provide the energy requirements of the livestock but they need supplements in seed ripening stages because of low quality and low intake of dried forages.

In order to compare the distance methods of density measurement, a field study selected in Karsang located on the north-western area of Shahrekord (ChaharMahal and Bakhtiari province) to 32,000 m2 (200×160) and divided into eight sections of 4000 m2 (100×40).There was one transect with100 meters length in each area that we identified 10 points randomly within 10 meters of each other. The distance methods density measurement included nearest neighbor, closest individual, Third closest individual, Random pairs, Point center quarter, Angle order, wandering quarter and Variable area transec. Selected species were Astragalus effuses, Eryngium billardieri, Astragalus rodoseminus and Astragalus verus. Hopkines and Eberhardt indices were used to determine of distribution pattern in plants. In order to verify the obtained density, the relative difference of estimated density in each method to control group was calculated (Density estimation error in each method). Also Duncan’s mean separation test was used to compare the accuracy of methods and using standard deviation and measurement time, the method efficiencies were calculated. The results showed that the variable transect, nearest neighbor and closest person methods are more effective considering the time as a Indicator and Third closest individual and Nearest neighbor are higher than other methods considering accuracy criterion. Finally, if the selected criterion is precision, we can clearly take the Variable area transect as the most efficient.

Zygophyllum atriplicoides is one of the dominant shrubs species in Iranian deserts due to its adaptation to dry condition. This research aimed to study Z. atriplicoides bioclimatic zones, using some advanced multivariate statistical methods in Isfahan province. Sixty eight climate variables were selected using of the data of 38 synoptic and climatology stations in Isfahan and neighbors provinces. Factor analysis was used to decrease the matrix dimensions from 68 to 4 factors. According to the results, cooling temperature, precipitation, the number of cloudy days per year and wind were responsible for 34.45, 29.43, 11.79 and 9.07 percent of measured data variances respectively. In other words, these factors were responsible for 84.74 percent of changes. According to hierarchical cluster analysis (Ward), six climatological zones were determined in the province and the most bioclimatic variables on the species distribution were selected by overlying the vegetation map with factor and bioclimatic classification maps According to the result, temperature and precipitation were the most important climate elements on Z. atriplicoides distribution pattern.

Present study with the aim of evaluating the changes in vegetation cover as a consequence of 29-years grazing exclosure (1983-2011) was conducted in Shahid Hamzavi (Ghorogh Hana) rangeland research station, located at Hana city, Semirom, Isfahan province. This study was conducted in order to understanding negative and positive effects of grazing exclosure in this area and evaluates its effects as a restoration management. Sampling was conducted using 1×1.5 m square quadrates which located at 5m intervals along each transect. Within each quadrate, crown cover, density, yield, reproduction and percent litter were determined. For determination of rangeland condition, four-factor procedure and in order to determination of rangeland trend scoring method were used. After ensuring normality distribution of data, independent t-test was used to compare the vegetation cover properties between grazing exclosure region and control sites. Results showed that due to exclusion, crown cover percent, yield and percent litter increased by 1.61-, 3.23- and 4.34-fold, respectively, and rangeland condition changed from very poor to medium status. Mean density of shrubs, perennial grasses and perennial broad-leaves decreased as 44, 6.2 and 16 percent respectively. Mean reproduction of Eurotia ceratoides and Bromus tomentellus increased about 13.6- and 21.5-folds compared to control site, respectively. All changes were statistically significant. Crown cover percent and yield of various growth forms significantly increased compared to control site. Also, diversity significantly decreased as a result of grazing exclosure. Generally, it can be stated that exclusion by creating positive changes in vegetation cover, plays an important role in improving rangeland condition. However, long-term exclosure is not recommended for this type of vegetation since in addition to loss of resources, diversity decreases and plant species lose their palatability especially E. ceratoides as it becomes a woody shrub.

Appropriate and efficient management practices on rangeland ecosystems require adequate information about the grazing density and its impact on rangelands species diversity. For investigating the effects of livestock grazing on change and reduction of rangeland species diversity and comparison of that with exclosure area, and also to investigate the positive effects of exclosure in regards to protect rangeland species diversity, two rangeland sites with different management practices as grazed and ungrazed (exclosure) areas were selected in Qushchy ghat in 45 km north of Urmia. Using minimal area method, a quadrate of 1m2 was selected. Samples were collected from 40 homogeneous sites at inside and outside of the exclosure based on four slope classes (2-8%, 8-12%, 12-20% and 20-30%) along the slopes with randomized-systematic method on 4 transects with the length of 50 meters. List of all existing species with frequency values, canopy cover, litter, gravels and bare soil, and other information were recorded. Moreover, in the middle of each transect a profile of soil was considered and soil samples were collected from the depth of 0-30 cm. Using similarity and evenness indices inside and outside of the exclosure were compared. Mean comparison was conducted using Duncan's test at the level of 5%. To determine the factors affecting changes in species diversity a test of principal component analysis (PCA) was conducted. Results of field observation show that, 96 species were distributed on the study area. From those in ungrazed (exclosure) areas 46 and in grazed area 37 and 13 species were common in both sites. The mean values of Shannon and Briloein indices were 3.48 and 3.26 for inside, and 2.99 and 2.84 for outside of exclosure, respectively. Moreover, the results of the analysis of species frequency on both sites showed that the ungrazed areas have high numerical indices values for richness, evenness and species diversity. Results of the mean comparison indicate that canopy cover; density and litter in inside of the exclosure were higher than the outside of exclosure as 23.6, 3.52 and 3.73% respectively. On the other hand, the amount of gravel cover and bare soil were decreased as 16.2 and 11.24%, respectively. Results of principal components analysis showed that among the investigated factors canopy cover, litter, gravel cover, percent of alkaline saturation, bare soil, Potassium, percent of sand, silt and clay have the greatest effect on species diversity.