فصلنامه تحقیقات مرتع و بیابان ایران
سال سیزدهم شماره 4 (پیاپی 25، زمستان 1385)

In order to comprehend magnesium, calcium, sodium, potassium, phosphorous, chloride, copper, iron, manganese and zinc content of dominant range plants (Agropyron intermedium, Bromus tomentellus, Hordeum bulbosum, Cousinia bakhtiarica andScariolla orientalis) speciesin Chaharmahal and Bakhtiari province was investigated. Samples were taken from five ungrazed areas during three stages of plant growth including growing, blooming, and seedling between 1997-2000 years. Concentrations of all above ions were determined by standard methods. The result showed that maximum concentration of magnesium and calcium in Scariolla orientalis, which amounts of means were 2.8 and 11.6 gr/kg, respectively. The highest concentration of sodium and potassium were found in Bromus tomentellus and Hordeum bulbosum respectively, with amount of 0.4 and 22.4 gr/kg. Maximum of phosphorus and chloride were observed in Hordeum bulbosum with amounts of3.1 and 5.4 gr/kg, respectively. Highest of copper and iron were 9.5 and 368 mg/kg, which belonged to Cousinia bakhtiarica and Scariolla orientalis respectively. Speciesof Agropyron intermedium contained39.3 mg/kg manganese and concentration of zinc in Scariolla orientalis was 18.6 mg/kg, which the amounts were the highest between species. This study showed which phosphorous, sodium, copper and zinc were insufficient for sheep grazing requirement in all species, but magnesium was insufficient only in Agropyron intermediumand Bromus tomentellus, also calcium concentration was lower than sheep requirement in Hordeum bulbosum. Therefore, mineral supplementation required to provide these mineral for grazing sheep and goats in spring and summer in range plants. Hence, potassium, chloride, iron and manganese provide the requirement of grazing sheep and goats, but chloride was over loaded and it was in the level of toxicity and unsafe for sheep and goats. Also different phenological stage showed that assessment factors were significantly different at growing, blooming and seedling stage of species. These factors must be considered when sheep and goats are grazing on natural pasture.

Rangelands have important role in economy of country because of providing forage for animals, soil and water conservation and other services giving to society. Therefore their careful management is necessary. To do this, main vegetative stepic regions of Qum province were selected. In each community a key area was determined to establish a permanent site, so eight key areas were selected in the whole province. In each site four parallel, 400 meter transects were established. Canopy cover and yield within 60 quadrates in two square meter areas, along each transect were measured each year. According to the results, Qum's rangelands contain poor vegetation composition with low cover percentage and yield. Desirable species were absent in vegetation composition and moderate and non-desirable species made major part of vegetation cover and yield. Most Qum's rangelands suffer from over grazing and should be recovered by a suitable management program. Results showed significant relationships (P<0.05) between canopy cover and forage yield of studied species during 6 years (1999-2004). However regression models calculated based on correlation between cover and yield varied due to seasonal condition in each year.

There are various factors that cause cantinous changes in the quality and quantity of natural resources which result in poor ranching, destructive flood, migration of villagers and nomads to large nearby cities and poverty of rural people. Identification of factors which are destructive to rangelands in Kermanshah Province was carried out to prevent destruction, to achieve optimal management and recognize priorities in planning. First of all, information and statistics concerning vegetation map and base map (from past to present) were obtained and analyzed. On the basis of Pabo Map and GIS, four different climatic regions of dry forest, warm semie-steppe. Cold semi-steppe and high mountainous were distinguished for Kermanshah Province. According to the survey conducted to explore the ecology of Kermanshah, index regions were identified using Pabo climatic Map. In any region, the vegetation of the range along with index of destruction of vegetation was studied. next step, questionnaires related to destructive factors to vegetation were filled by both experts and rural families and nomads and, then were assessed using the statistic method of regression and finally the frequency of different destructive factors to rangelands was calculated. The results indicated that in Kermanshah rangelands, changing the land use, the increase in the number of animals, and early grazing are the common factors of destruction respectively.

The pressure of livestock grazing and overall utilization of rangelands have caused vegetation and soil degradation in many natural rangelands of Iran. Grazing prevention is one of the rangelands rehabilitation methods, which is effective in renovation of rangelands. The effect of 24 years of grazing protection were studied on vegetation dynamics of Kuhrang region, in two years growing seasons (2003 and 2004). Parameters from rangelands characteristics were collected and analyzed. Results showed that after 24 years livestock exclusion in Kuhrang, total inside canopy cover was higher than outside (P<0.01). Grasses and forbs were higher inside than outside (P<0.01), but shrubs were not significantly different (P>0.05). Over half of inside canopy cover belonged to decreasers and increasers, which were little or negligible outside of exclosure and 95 percent of outside plant composition belonged to invaders. Most desirable species had greater inside cover than outside(P<0.01). Klucia odoratassima, Scorzonera calyculataand Delphinium cyphoplectrumhad greatest inside canopy cover, than other forbs. More than half of inside and 95 percent of outside cover referred to decreasers and increasers. Approximately 38 and 1.2 % of inside and outside forage production belonged to decreasers and increasers respectively. Regeneration was higher outside of exclosure in Astragalus adscendens, in first year. Litter was higher inside and bare soil outside the exclosure (P<0.01). Inside and outside range condition was good and very poor, respectively.

Study over vegetation on grazed and ungrazed rangelands is significant for range managemen, this the effects of 2-decade exclusion on vegetation of steppic rangelands in Nir range research station were studied. Three 7.5-hectare experimental plots were selected inside and outside of the exclosure. Exclosure site had not been grazed from 1986 to 2004. The adjacent site was continuously grazed at the same time. Cover estimated on quadrates and forage yield were measured by clipping and weighting method. Data were analyzed by t-test method. Results showed that cover, density and yield of Salsola rigida and Stipa barbata increased significantly inside exclosure (p<0.01), but it was not significantly different in Artemisia sieberi (p>0.05).Cover, density and yield of Scariola orientalis, Launaea acanthodes and Noaea mucronatawere greater in grazed area, but only the yield of first species, density of second species and cover and density of third species were significantly high (p<0.05). Two-decade protection from grazing showed that vegetation trend is very slow in arid rangelands.

Identification and measuring the effects of factors on forage resources capacity (FRC) were considered as the objective of this research in Bakkan region as the first nomad's settlement project. Four tribes with financial support of the government settled next to two villages in Bakkan. In nomadic production system (NPS), the FRC measured with system approach in three subsystems of rangeland, crop, and animal production systems. Three groups of factors that had an impact on energy flow in NPS were measured and identified. GIS with survey and deep interviews with the heads of the nomads groups and help of some current models were applied to show the measured and integrated factors in these groups. The results indicated that 151,151 and 87,274 animal units (AU) are the FRC in 2001 in Bakkan region during wet and drought years, respectively. The rangelands in Bakkan only produced 31.7% and 15.1% of FRC during wet and drought years respectively and the rest from croplands. The results based on proper use of factors showed that 6.2% of the rangelands are under good condition, 47.9% under fair and the rest (45.6%) are in poor and very poor condition. The trend of 50% of the rangeland is positive, but with steep slope, far from drinking water areas and the rest is negative. Nomads have to be familiar with the elements which have impact on FRC to estimate animal numbers equal to FRC in a sustainable management on rangeland and crop production.

This paper investigates the effects of plant growth on soil quality in Sagzi plain of Isfahan in order to evaluate the effects of agriculture on desertification processes in dry lands. Inappropriate crop management is the most effective factor which is related to soil and water salinization and this is one of the important processes of desertification. Is agriculture a positive or negative factor for reclamation of saline soils? To find an answer for this question, some improved and degraded factors of desertification in Sagzi plain of Isfahan were considered. Among those common agricultural products, which of them is more effective and which of them is less effective in soil reclamation? Treatments of Medicago, Wheat and Barley were selected and compared with derelict land that was independent variable in this experiment. In order to investigate the effects of those products, soils were considered that were allocated to cultivation of these products successively at least for 5 years. Then sampling was selected in every treatment with 5 reduplication, from the depth of 0-3, 30-60, 60-90, 90-120, 120-150 centimeter. The saline features and CaCo3, EC, OM,K+, Mg2+,Ca2+, Na+, Caso4, Cl-, SAR, HCo3-, So42- investigated in every treatments. Dunkan test was applied for comparison of soil features. The results of variance analysis showed that there is significant different between treatments in different depths. Dunkan is test showed that according to the overall scores for each factor, derelict lands are least decent treatment while Weat annual agro technical lands are the most suitable one. Then this is better that agricultural products that are appropriated with condition is cultivated.

Salinity is one of the factores affecting the reduction of soil biological potential and vegetation and finally desertification. Water is the most limiting factor for cultivation in arid and semi arid regions. Due to shortage of surface water resources, the pressure is exerted on under ground water resources. Meanwhile, over –exploitation of underground water resources and neglecting technical points in exploitation have caused the level of underground water to be dropped. This water level drop in addition to other factors causes the quality of water resources to be changed leading to increasing of salinity. This research has been carried out in kabootarkhan plain, kerman province. In order to study factors salinizing underground water resources in this basin, some baseline data were gathered. Then, sampling of profiles of soil profiles were done in the four soil units (arable lands, ferdowsi, agriculture station and kabootakhan) in the basin in three replications. The laboratory results and existing data were analyzed using SPSS software according to the randomized split-pot design. The results show that in appendage plain of the basin, irrigation with saline water resources in addition to soil texture have caused salinity to be occurred and in clay flat, irrigation has caused salinity to be declined due to the good soil texture and existence of natural drainage.

Based on a general model, estimated number of population density for ten years old Haloxylon plantation in Gonabad was 150 trees per hectar; therefore, six density treatments were selected around the estimated density; two density treatments over estimated number, two under it, and existing density as the control treatment. The treatments consisted of T1=120, T2=135, T3=150, T4=165, T5=180, and the existing density (control) T6=250 trees per hectar. The treatment have been compared in a Randomized Complete Block Design, with four replications, since the spring 1996. After thinning, height (H) and crown diameter (CD) of the remained trees were measured. This measurement was repeated during the growth period in ten years. A size index (SI) model of the form H ×CD2 was founded to distinguish the best among the 6 treatments. The growth percentage of H, CD, and SI, between first and the last measurement were calculated. The analysis of variance of the growth percents showed that there is significant difference between treatments. The highest growth belonged to T1 and lowest belonged to T6 (control). This result show that optimized population density for ten years old Haloxylon stands in Gonabad is 20 (and or 10)% less than the estimated number based on the general model.

Annual medics which have rapid growth rate, high forage yielding, various growing habits, form a tick growing cover which reduces run-off, soil erosion and increase soil moisture and soil fertility, therefore it may replace the wheat-fallow system. This study was conducted to achieve this purpose in Sanandaj Research Station of Kurdestan province at the altitude of 1340 m with average precipitation of 462 mm. A randomized complete block design with four replications and five different seed rates of 6, 8, 10, 12 and 14 kg/ha for Medicago rigidula were applied in two years. The data were collected and analyzed for forage yield of different rates. The results of combined analyses showed that increasing one kilogram seeds resulted in 67.5 kg/ha increase of forage production, we suggested that using 14 kg/ha seeds of Medicago rigidula is preferable.

In this research salt tolerance and physiological characteristics of Atriplex verrucifera ecotypes in Tabriz, Qazvin and Arak rangelands were investigated. This species due to bushy form, salt resistant, proper proteine percent, is one of the native plants and valuable in saline rangelands. These characteristics caused extensive use of this plant in rangelands reformation programs. The aim of this research paying attention to physiological parameters changes of salt resistant species ecotypes. Samples (soil and plant) of Atriplex verrucifera ecotypes were collected from Tabriz, Arak and Qazvin region and were analyzed. The experimental design was completely randomized design with 4 replications and 3 treatments (Tabriz, Arak and Qzvin). The studied parameters consisted of: water content relation, water potential, glycinebetaine,, proline, soluble sugars, starch, sodium, chlor, potassium, manganese, calcium, pH, Ec and soil texture. Results showed that rate of changes related water content, water potential, glycinebetaine, proline, soluble sugars, starch and ion accumulation in ecotypes were significant. Also in this research it was noted that salt resistant parameters in ecotypes dependent to climatic condition, soil chemical and physical characteristics. Results showed that Tabriz ecotype salt resistant parameters increased compared to others ecotypes.