فصلنامه تحقیقات مرتع و بیابان ایران
سال نوزدهم شماره 3 (پیاپی 48، پاییز 1391)

This research was aimed to investigate the relationships between dominant rangeland species and environmental factors in the Rineh rangelands located on the southern slope of Damavand Mountain. Stratified random sampling method was applied and the study area was classified to 37 sample units based upon elevation, slop and aspect. In the study area, 750 plots 1m2 and 75 plots 25m2 were established. One hundred and fifty soil samples were dug at the depth of 0-30 cm and 16 soil properties including pH, CaCo3, bulk density, particle density, total phosphorus, total nitrogen, absorbed potassium, organic matter, saturation moisture, soil texture, field capacity, permanent wilting point, available water capacity and water holding capacity were measured in laboratory. After collecting the climate data, 16 climate factors including average relative humidity, average rainfall, average temperature, average minimum temperature, average maximum temperature in spring, summer and annual as well as annual frost days were selected to reconstruct the missing data. IRS images including red and near-infrared bands and PAN band as well as combined bands derived from RVI, NDVI, and PCA were selected. Regression equation was developed for each species using logistic regression. Results indicated that most of the factors including slop, aspect, average minimum temperature in spring, number of frost days, average daily temperature in summer, and most of the soil factors were entered in regression models. Also, satellite data were used as effective tools in showing the presence of plant species.

In this study, five rangeland species including Festuca rubra, Astragalus glocucantus, Astragalus flocoffus, Acantolimon erinaceum and Acantophyllum sordidum were selected at three phenological stages of vegetative growth, flowering and seeding. These species are almost palatable and important in rangelands of Jashlobar, Semnan. For each phenological stage, three replications and for each replication, five species were collected. Plant samples were analyzed to determine N percentage as well as acid detergent fiber (ADF). Crude protein (CP), dry matter digestibility (DMD) and metabolizable energy (ME), were estimated based upon N percentage and acid detergent fiber (ADF)., Split-plot design was applied for data analysis in a randomized complete design with 3 replications and 15 treatments for each location. After collecting the data, combined analysis of variance was used in order to investigate the changes of forage quality index. According to the results, chemical composition of plants showed significant changes and phenological stages had a significant effect on forage quality. With the advance of growth, CP, DMD and ME decreased while ADF content increased. Obtained results are applicable for estimating daily required forage for grazing livestock and determining appropriate time for livestock entry to the rangeland.

Determination of allowable use of the key species of rangelands is necessary to calculate the rangeland capacity. Actual rangeland capacity could be determined through having the exact values of this factor for rangeland species and the destruction of vegetation, soil and water loss on rangelands can be avoided. In this research, Artemisia aucheri, Bromus tomentellus, Kochia prostrata, Asperula glomerata and Buffonia koelzii were investigated as the key species of Arak Enjedan rangelands. A key area of one hectare was selected in Arak Enjedan rangelands and was fenced in the first year of the study. Then, 40 individuals were selected from each species and harvesting intensities of 25, 50, 75% and control treatment were implemented. Harvesting was done by a clipper monthly during grazing season for 4 years. The influence of harvesting was investigated in the second to fifth years through the study of changes in phenological characteristics, forage and seed production, vitality, and mortality and other characteristics of plant species. Results showed that increasing the harvesting intensity caused problems and decline of vital abilities of all species especially, As. glomerata and Br. tomentellus that are more palatable species. According to the results, an allowable use of 25% is recommended for Br. tomentellus and As. Glomerata while for Ar. aucheri, Ko. prostrata and Bu. Koelzii an allowable use of 50% was obtained with the least negative effects on plant characteristics. Results of the analysis of variance for forage production data were significant for all of the studied species in %1 level of probability.

Due to uncontrollable natural regeneration of invasive and non-native species of Prosopis juliflora in the coastal areas in south of the country, effects of the species on soil properties under canopy cover were investigated. This study was conducted in Hormozgan province, in different sites including Bandar Abbas, Ghaleghazi, Minab and Sirik. In each region, the species were randomly selected in one hectare of land and then the soil under and outside the canopy cover were sampled from two depths, 0-15 and 15-30 cm. pH, EC, saturation percentage, soluble calcium and magnesium, chlorine, HCO3-, SO42-, potassium, organic carbon, total nitrogen and available phosphorus phosphorus were measured in laboratory. Results of this research showed that there were significant differences in some soil properties such as pH, EC, and organic carbon in depth of 0-15 centimeter. It is worth noting that changes in soil properties under canopy cover were not similar in all regions. This may be due to the establishment period of the species in different regions, habitat conditions, the occurrence of rainy and drought periods and the density and diversity of native species. Some soil properties did not differ statistically beneath and outside the canopy of this species but it seems that the trend of these changes has not been stable. It is emphasized that the role of Prosopis juliflora in connection with the change in density and diversity of natural vegetation beneath the canopy cover could not conclusively be attributed only to changes in soil.

Knowledge on floristic composition is one of the most important factors in management of rangeland utilization. Improper utilization of rangelands and lack of attention to the ecological potential of range habitats is the main reason for rangeland degradation. In this study, floristic composition and canopy cover of the species of reference area (exclosure), key area (with mid grazing) and critical area (with over grazing) were considered and three areas were compared together. Ranking of the canopy cover percentage was performed through Van-der-Maarel method and counting the number of the species was carried out using a systematic-random method. According to the obtained results, three relations were obtained as follows: Major biological forms: Therophyte> Hemicriptophyt> Chamophyte> Geophyte> Phanerophyte; Dominant growth form: Herb> shrub> grass> tree; Vegetation ranking based on canopy coverer: reference> key> critical area. In the critical area, due to over grazing and out of grazing season, canopy cover was strongly reduced and plant palatability decreased.

This research was performed in Isfahan and Tehran Provinces. The races considered in Tehran province were Zandi Sheep and native goat. Naeini Sheep and native goat were also studied in Isfahan province. To feed livestock, rangelands (winter range and summer range), aftermath of farms and handy hay were used. Using of aftermath and handy hay was done in all flocks. The usage duration of hay, aftermath and rangelands in Tehran province was different among the flocks considered in this study due to different flocks and different years as they differed from 65 to 120, 100 to 180 and 90 to 245 days respectively. The usage duration of hay, aftermath and rangelands in Isfahan province also differed from 85 to 100, 30 to 240 and 90 to 245 days respectively. In both provinces, the forage of rangelands and hay were used simultaneously to compensate the shortage of forage in rangelands. Livestock products in the flocks were milk, cheese, curd, butter, wool and fuzz. The amount of Per capita production was different per head. In Tehran province, sheep suck differed from 25 to 120 days in the flocks considered here. In Isfahan province the milk of sheep was used by lambs hence there was no sheep suck. Curd production was just done in one flock which approximately produced 0.5kg curd per a head of sheep annually. Wool harvest was performed in all flocks. Per capita production of wool differed from 800 to 900gr per a head of sheep. Cheese production was done through the milk of sheep and goat and its amount for sheep and goat differed from 2 to 7.7 and 4.5 to 12kg respectively. The average of wool and fuzz production in Isfahan province differed from 500 to 800 and 200 to 250gr in different flocks respectively. In this province, cheese produced from the milk of goat and differed from 90 to 1200gr related to the duration of suck in different flocks. The amount of curd production also differed from 150 to 1500gr per a head of goat. The amount of milk production in goat differed from 3 to 10kg related to the duration of suck. The sale of lamb and goat was the main source of rancher's income. The sale weight of lamb and goat differed in various ages. Average weight of lamb and goat were different as below: The average weight in 3, 3 to 6 and more than 6-year-old lambs of Naeini and Zandi races was 28.8, 34.8 and 32.6kg respectively. Average weight in less than 3, 3 to 6 and more than 6-year-old goats of native races in Isfahan and Tehran was 23.8, 23.8 and 24.7 kg respectively. There was a significant difference between the weight of lambs and goats. There was a significant difference between the weight of Naeini and Zandi sheep. The results showed that the most economic age of livestock in both Naeini and Zandi races were 3 to 6- year-old. Weights of 3 to 6-year-old lambs in Naeini and Zandi races were 29.6 and 39.8 kg respectively. The weight of 3 to 6-year-old goats in native races of Isfahan and Varamin were 20.8 and 30.4 kg, respectively.

In this study, species of Salsola rigida, Seidlitzia rosmarinus, Atriplex canescens and Anabasis setifera were investigated to identify appropriate species for planting together with Haloxylon ammodendron. This research was aimed to use spaces among shrub species and to enhance the ecosystems in which H. Ammodendron species are distributed. The study was performed in a randomized complete blocks design with three replications and six treatments at research station of natural resources of Semnan. The measured traits were included annual growth (measuring the thickest branch, flowering branch and the length of horizontal branches), forage yield and seedling establishment. Results of analysis of variance showed that there were no significant differences among blocks. A significant difference was observed for seedling establishment at 1% level of probability. High growth and canopy cover of H. ammodendron significantly differed with other species. A. setifera, S. rosmarinus and A.canescens were respectively in the best position in term of number of sub-branches. This feature is important in controlling erosion and resistance to grazing. H. ammodendron, S. rigida and S. rosmarinus showed suitable condition in terms of forage yield. No significant differences were observed for seedling establishment. Maximum number of the established species were recorded for A.canescens, S.rigida, N.schoberi, A.setifera, S.rosmarinus and H.ammodendron, respectively.

Detailed studies of vegetation in desert areas are almost difficult due to the limitations and conditions of the areas. Remote sensing technology with numerous capabilities can be used as an efficient method in the areas. This study was aimed to determine an appropriate vegetation index to assess vegetation changes in the desert area of West Karkheh over a period of 18 years using satellite images of TM (1991) and ASTER (2008). After measuring the canopy cover, geometric and atmospheric corrections, different methods of detection and classification were applied on the images with maximum likelihood method. Results showed that PVI2 index was the best indicator to produce vegetation changes map during the study. So based on this index, final map of desertification was produced in the three classes with no changes and rehabilitation. The results showed that canopy cover increased up to 17.5% of the total area during the study period due to the implementation of desertification projects in some parts of the region and combined cultivation. These changes were classified in two classes of rehabilitation (69.8%) and desertification (30.2%).

In mountainous rangelands, there is a complex combination of factors such as topography, vegetation growth stages and water distribution which affect grazing distribution. This research was conducted to investigate the effect of topography on vegetation of summer rangelands of Vaz, Mazandaran province. Five utilization units were selected on the basis of field survey and identifying homogenous grazing units. Key areas were obtained in each unit and sampling was done randomly. Size of the quadrates was 1m2 and the number was calculated by statistical method. In each quadrate, yield was measured by clip and weigh method and utilization rate was determined using height to weight ratio (based on dry weight). Vegetation cover percentage was also recorded. Finally, comparison of plant characteristics in utilization units was performed by SPSS in a completely randomized design with unequal replications. Then, correlation coefficient between each of the independent variables (slope, aspect and height) and dependent variables (yield, canopy cover percentage and utilization) was determined. Also, the most effective factor and interaction effects of independent variables were obtained by stepwise multiple regression analysis. Results showed that slope and aspect had the most correlation with livestock utilization respectively, but no relationship was found for elevation while it affected yield and canopy cover.

Knowledge of the plant distribution pattern in each region is of principles and fundamentals of vegetation survey and measurement that plays an important role in the selection of management approaches. A study was performed to determine the distribution pattern of three dominant species of Artemisi aaucheri, Kelussiao doratissima and Prangos ferulaceae in Dyshmuk region in northwestern Kohgilouyeh and Boyer Ahmad province. One hundred quadrates of 2×2 m were randomly located along six transects of 100-m length and the number of each species was recorded. Using this information, the most appropriate and accurate quadrate-based distribution indices (Green and standard Morisitat indices) were calculated. According to the results, Kelussia odoratissima and Prangos ferulaceae showed a random distribution pattern while distribution pattern of Artemisia aucheri was uniform to random.

This research was aimed to study the autecology of Asthenatherum forsskalii as a desert and range species (Vahl) Nevski in arid and super-arid deserts of Masileh, Isfahan province. This range species is psammophyte and belongs to the Poaceae family with numerous aerial branches growing in desert sandy dunes. In order to study the autecology of the species, its habitats in the desert sandy dunes of Aran & Bidgol were determined. After determining the habitats, ecological characteristics such as elevation range, topography, climate, soil, companion species, presence in the vegetation cover, root system, phenology and propagation of the mentioned species were all studied. Results showed that the habitats were distributed in the form of spots scattered across the sandy plains and slopes of active sand dunes. This desert plant grows in an altitude range of 780 to 1150 meters above sea level with an average annual rainfall fluctuating between 80 and 120 mm. Its mean annual temperature is about 19.1 °C. The species is widespread on light-textured sandy soils with pH and EC (Electrical conductivity) of 7.5-8.5 and 0.34-5.1 ds/m, respectively. A. forsskalii has a fibrous root system with a length over up to 6 meters. All its fibrous roots are covered with sand particles. Average canopy cover is 4.2%. Average density is 11,875 to 32,500 species per hectare and it has a frequency of about 72%. Vegetative growth begins in late February and its inflorescence emerges in the second half of May and the seeds appear in late June. Summer dormancy starts from late July and continues up to mid-September. Revival of the species is possible via seeds and formation of adventitious roots in the basal area. The most important companion species in the habitats of A. forsskalii are grasslands of Cyperus eremicus and various species of genus Calligonum L.. According to the results, A. forsskalii is a psammophyte desert species which in addition to soil conservation and stabilization in sand dunes, plays an important role in providing required forage for livestock in winter rangelands.

Desertification is a multifactorial phenomenon and relates to different aspects. Thus, this concept can be studied around multiple axes in natural resources and environment. Nowadays, the rapid growth and huge population in environments and ecological areas are of the most important concerns that have attracted the attention of experts and planners to the concept of desertification or combat desertification. On the one hand, astounding growth of metropolises and unbridled industrial development have led to adverse outcomes for the residents. Moreover, land is a limited resource and the situation will get worse over time in many countries due to the exponential growth of population and extensive use of land and with regard to the fact that only 5 million km2 of the earth has remained for sustainable utilization in future. There are many issues surrounding population supporting capacity based upon the quality of the land in order to maintain the sustainability of resources and environment. The purpose of this article was to estimate population supporting capacity of Tehran and Alborz on the basis of the potential of land units through the method introduced by Central Department of Agriculture of USA. This is the first step to determine the extent of land degradation and detection of man-made desertification. In the current situation, it is obvious that a demographic development of Alborz and Tehran provinces has led to instability in the environment and desertification. Based on the results, classes 1, 4 and 9 of the land quality covered 20.38, 14.93, and 37.44 percent of the surface area, respectively. These three classes could be accounted for 81.9% of population supporting capacity according to the potential of production. Our results showed that lands of the study area were exposed to desertification classified as very high risk (38.55 % of the total area), high risk (25.06 % of the total are), moderate risk (23 % of the total area), and low risk (13% of the total area). Accordingly, it was found that the current population of Tehran province was 5 times higher than the optimal population. This ratio also reaches 4.7 times in high-density areas such as Tehran, Karaj, Shahriar and Robat Karim.

Appropriate utilization of plant species in rangelands is one of the principles of sustainable production in rangeland ecosystems that leads to continuous and economic utilization of rangelands. In order to achieve stability and continuity of production in steppe rangeland, this study was performed to investigate the effect of different harvesting intensities on forage production and vitality of Stipa arabica at Isfahan Soh site, during 2007 to 2010. Treatments in each block were included four grazing intensities of 25, 50 and 75% and control (no harvest). In each treatment, 10 individuals of species were used as replications evaluated on each of the dependent variables. A factorial experiment in a completely randomized design with ten replications and four years was used to analyze the data. Data analysis was performed by SAS software. Results showed that forage production of Stipa arabica did not differ statistically in response to different harvesting intensities, and up to 75 percent of the species could be harvested, but heavy harvesting intensity decreased the vigor and vitality of the species during the examined years. Harvesting intensities were significant at 1% level of probability and production rate decreased gradually over the 4 years. According to the results, a harvesting intensity of 50% is recommended for Stipa arabica in the region so that health and vitality of this species is preserved during the harvesting years.

This research was conducted at Homand Absard research station, 70km east of Tehran, to study the establishment and survival of 10 accessions of Elytrigia libanoticus L. The experiment began in 2003 and continued until 2006. Of each accession, 25 individuals were cultivated on 13-meter lines at 50cm intervals. Cultivation lines were 75cm apart. Vigor, survival, forage and seed yield as well as growth parameters were recorded annually. The aim of the study was to determine the best accessions in view of survival and establishment. Obtained data in different years were analyzed with IRRISTAT software. Afterward, interaction effects of accessions and environment and additive main effects of the collected data were calculated using AMMI method in a randomized complete block design (RCBD). Mean comparisons were performed using Duncan's Multiple Range Test at 5% level. According to the results, there were significant differences among studied accessions at 1% level of probability during the study. Accession No. 10627 was identified as the best one while accessions 10624, 10628 and 10633 showed the lowest survival respectively.

Nowadays, water resources scarcity has become one of the most important issues in arid and semi arid regions including Iran which makes it necessary to optimize the utilization of the limited resources. This research surveyed the variations of EC, TDS, Cl-, SO4--, Na+ for an eleven-year period base on the data collected from selected wells of Semnan Plain. In order to select the appropriate model to fit to experimental variogram, Residual Mean Square Error was used. Several geostatistical approaches such as simple kriging, ordinary kriging, simple cokriging, and ordinary cokriging as well as other deterministic interpolation methods including Inverse Distance Weighing (IDW) with different powers were considered. Then, validation approach and Mean Absolute Error (MAE) criteria were considered to determine the most appropriate interpolation technique. Meanwhile, cokriging method was selected as the fit method for qualitative parameters which illustrated the variations of groundwater quality in almost 67% of the cases. Comparison of quality parameters of spatial zoning maps showed that the rate of these parameters was developing in the core shape to the selected wells 15 and 13 and also, it had an increasing trend in plain boundaries for an eleven-year period. But there were no significant changes in the centers of plains. According to the results, lithology, unsustainable harvesting of wells, increased evaporation and thus reduced level of ground water and inappropriate methods of irrigation and agriculture were identified as the most effective factors.