جستجوی مقالات مرتبط با کلیدواژه « اکوسیستم های مرتعی » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

 The germination and establishment of plants resistant to drought is one of the most important and effective aspects of rangeland improvement. Investigating changes in rangeland species' morphological and physiological characteristics under different pretreatments under laboratory, greenhouse, and field conditions is necessary. As a result, elite and promising species can be selected, and improvement efforts can be evaluated favorably.

 This study investigated the effect of different pretreatments on the germination and establishment of Sanguisorba minor and Elymus hispidus under drought stress. In this regard, the effect of priming treatments with distilled water, polyethylene glycol, potassium nitrate, and silver nanoparticles was studied to improve germination characteristics and establishment of species under agricultural capacity. The experiment was conducted as a factorial in a randomized complete block design in four replications. To conduct the research, 168 pots were used, and ten seeds were planted in each pot. The measured attributes included the percentage and velocity of seedling appearance from the soil, establishment and survival, length and weight of root and stem, vigor, proline, carotenoid, soluble sugar, total chlorophyll, catalase, and superoxide dismutase enzymes. After sampling the studied traits in the greenhouse and obtaining the results in the laboratory, variance and data analysis in SPSS software. A comparison of mean data with Duncan's multiple range tests at a 5% level for the studied traits was performed on both species.

 The results showed that drought stress significantly differs in characteristics, such as the dry weight of aerial parts or the length of plant roots. The mutual effects of priming and stress were significant on the traits of emergence from the soil, speed of emergence, establishment, survival, and dry weight of aerial parts. Still, it affected several other traits as well. The application of silver nanoparticles had positive or negative effects on seeds' vegetative characteristics, and seedlings grown from the seeds of the studied plants did not show significant changes to characteristics such as plant root length under different priming treatments at a specific moisture level. Some characteristics, including ability, had significant changes due to humidity levels varying up to 20 percent. The positive effects of polyethylene treatment and the negative effects of high nanoparticle concentration were evident. Applying polyethylene glycol and potassium nitrate in E. hispidus and polyethylene glycol and silver nanoparticles at a concentration of 30 mg/l in S. minor showed the highest positive effects on plant resistance under drought stress. Application of silver nanoparticles at concentrations of 60 and 90 mg/L showed negative effects on the vegetative and physiological characteristics of the two studied species.

 drought stress caused negative effects on the structural characteristics of the studied species, and using hydropriming treatments, potassium nitrate, polyethylene glycol, and silver nanoparticles (with a concentration of 30 mg/liter) reduced stress adverse effects. The reason for this is mainly the changes in the physiological factors, such as the amount of proline, catalase, and superoxide dismutase enzymes, and the application of various pretreatments causes positive changes in pretreatment factors and increases the species' drought resistance. The results related to the effect of different pretreatments on the germination of the mentioned species under laboratory and field conditions also confirm this issue.

With the multi-purpose use of rangelands, grazing pressure in rangelands can be reduced and an important step can be taken to preserve rangeland ecosystems and improve related ecosystem services. Therefore, the present study aimed to determine the priority of multi-purpose use of vegetation in Koohrang mountain rangeland in terms of livestock grazing, beekeeping and exploitation of medicinal plants. For this purpose, the class of each plant species for different types of use was determined and by comparing different classes and considering the good species (class I and II plants) for livestock grazing; the priority of using any was determined. Finally, based on the share of types of use for the total number of plant species in the plant composition, it was decided on the type of multi-purpose use of vegetation. Based on the results, 178 plant species belonging to 32 families and 138 genera are distributed in the plant composition of the region. In terms of livestock grazing, respectively 11.79, 29.21, 48.31and 10.67 percent of the species have palatable class I, II, Ш grazable and Ш non-grazable. For beekeeping, attractive species for beekeeping include plants with good attractiveness (Class I), medium attractiveness (Class II), low attractiveness (Class III usable) and plants without attractiveness (Class III unused), respectively 11.79, 49.94, 4.44 and 38.76 percentage of species in plant composition. Oral and medicinal species, contain about 50% of the plant composition, which respectively 19.10, 16.85,12.92 and 50 percentage of species have usefulness classes I, II, Ш pharmaceutically usable and Ш non-pharmacologically useful. Meanwhile, 18.53% of medicinal plants can be grazed on livestock and are in class I and II in terms of livestock grazing. In total, 18.53percent of medicinal plants can be grazed and are in food grade I and II in terms of grazing. The results show that the use of medicinal plants is effective in the livelihood of beneficiaries and according to the phenology of plant species and rangeland segmentation, vegetation can be used in the context of multi-purpose use.

Continuous and long-term measurement of vegetation is required to obtain basic and timely information concerning rangelands. The important point to consider in this regard is the correct choice and the proper number of representative places to be taken into account when measuring vegetation density in different ecological areas. On the other hand, monitoring rangeland ecosystems is exessively costly, requiring a great number of personnel and technical facilities. However, failing to monitor the rangelands in those areas that are representative of a wide range of vegetation prevents the achivement of desired results concerning vegetation monitoring. Therefore, as measuring and monitoring the vegetation of macro rangeland ecosystems of Iran requires the investigation of several landmarks / sites over a specific period, this study sought to monitor the vegetation of a number of select representative sites along the elevation gradient of Taftan’s southern slope.
 

 First, several places representing the habitats of the region and the distribution of Taftan Mountain’s vegetation along the altitude gradient were selected by examining the maps of Iran’s ecological zones (Khash region). Then, vegetation characteristics of the places, including percentage of canopy cover, number of bases per hectare, and amount of species forage production were measured, followed by the classification of sampling units based on similarities in species composition. To this end, four 450-meter transects with a distance of 100 meters from each other were used in the first place, which is dominated by Hammada salicornia and Zygophyllum atriplicoides. On each transect, 15 four-square meter plots (2× 2 m), that is 60 plots in total, were placed 30 meters away from each other. The second place that was dominated by Hammada salicornia, Zygophyllum atriplicoides, Artemisia sieberi and Artemisia santolinifolia species resembled the first place in terms of sampling network and the number of sampling units. On the other hand, three 100-meter transects were used in the third place with 50 meters’ distance from each other, on each of which 10 two square-meter plots (2×1 m) were placed 10 meters away from each other (30 plots in total). The lower vestibule of the third place was dominated by Artemisia quettensis, Artemisia sieberi, and Artemisia deserti (herbaceous species), and the upper vestibule of the place was dominated by Amygdalus scoparia (the woody element). Moreover, in the fourth place dominated by Artemisia quettensis and perennial herbaceous species such as Ferula ovina, four 100-meter transects were used with 50 meters’ distance from each other, on each of which 10 one-square meter plots were placed 10 meters away from each other (40 plots in total). To classify sampling units based on species compositional similarities, the sites’ vegetation was first classified into ecological groups using Twinspan analysis. Then, the correlation between the groups and topographic factors (slope, direction, and height) was investigated via principal component analysis (PCA), and the significance of the model was evaluated by P-value. Furthermore, thee collected data were analyzed using the Pc-OIRD software version 5.1.
 

 The study’s results indicated that the average canopy cover in the studied sites were 17%, 28.9%, 52.6%, and 40.8%, respectively, during the growing season at 2021, with the sites’ average forage production being 32.8 kg/ha, 46.0 kg/ha, 107.7 kg/ha, and 208.8 kg/ha. Moreover, compared to the potential forage production in steppe areas (200 kg/ha), the sites’ producation capacity (against the ultimate production limit) was found to be 16.4%, 23.0%, 53.5%, and 100%. Based on the results of the classification, the first axis had the highest positive correlation with the dominant species of the first and second places, that is, the Hammada salicornia and Zygophyllum atriplicoides, suggesting that the similarities within the species of the two places are the same. The second axis was also found to have the highest positive correlation with Artemisia quettensis and Ferula ovina (the dominant species in the fourth place), indicating the distinction of the similarities within the species of the place form other three places, especially from the first and second places. On the other hand, compared to other sampling units, those of the third place where Artemisia quettensis, Artemisia sieberi, and Amygdalus scoparia are dominant were found to have an intermediate distribution, with their species mainly having a negative correlation with the first and second coordinate axes.
 

 According to the results of this study, selecting at least three representative locations (site) along a region’s altitude gradient to monitoring vegetation on a regional scale, it is necessary to select. A site can represent desert ossuaries (altitude range 1500-1700 m) dominated by Hammada salicornia and Zygophyllum atriplicoides. The other two sites can represent both middle-altitude mangroves (located at altitude range of 1700-2500 m) dominated by Artemisia quettensis, Artemisia sieberi, Artemisia deserti, and high-altitudes above the tree line (more than 2800 m) whre Artemisia quettensis, Ferula ovina, and cushion plants are predominant. Therefore, it could generally be argued that applying the results of vegetation monitoring and measurement to a specific scale on a wider scale requires the consideration of temporal and spatial scales of monitoring (customary order scale, landscape scale, and regional/national scale), taking into account the existence of different issues and data.

Climate change has been a serious issue in the last two decades and many studies have focused on its various aspects. Therefore, it is necessary to determine the future habitat of rangeland species present and future years, under climate warning models. In this regard, it should be investigated whether the increase in temperature will have a positive effect on the presence of species in the habitats of the distribution site or a negative effect?.

For this purpose, from 19 bioclimatic variables and three physiographic variables and logistic regression model, to quantify climate change in the next three decades (2050) and to examine its effects on the current change of Ferula ovina species and the future, was used. Output maps were also grouped into four categories with a probability of occurrence between zero and one. These groups, unsuitable habitat, (0-0.25); Habitat almost suitable, (0.25-0.5); It shows a high proportion habitat (0.5-0.75) and a very high proportion habitat (0.75-1). Finally, by referring to the coefficients of climatic variables and topography in regression relations, effective variables for the current and future range of F.ovina were introduced.

Based on results; among the climatic and topographic variables, only the indicators related to the average temperature of the warmest season (BIO10) and the average temperature of the coldest season (BIO11) were identified as effective on the distribution of F.ovina species in present and future Alborz rangeland habitats. The characteristics increase as the climatic conditions become more difficult. Average annual temperature in places with a probability of more than 75%; over the next three decades, under milder (Rcp 4.5) and pessimistic (Rcp 8.5) scenarios, it will rise from 2.6 to 0.3 ° C. The height of suitable habitats will be 60 to 162 meters. As a result, adequate habitat levels (greater than 75% probability) decrease in response to climate change. Under climate scenarios, 15% of suitable habitat habitats will be lost by 2050 and current unsuitable habitats will increase by 48%. Overall; climate change and increasing temperature characteristics will cause the vertical expansion of F.ovina species to higher latitudes along the altitude gradient. This indicates that over the next three decades, the presence of F.ovina species in the habitats of the region will decrease and the risk of its removal from the southern Alborz ecosystems is evident.

According to the results obtained in this study, large changes in the distribution of this species are expected to occur along with climate change. These changes are such that they can limit the suitable climatic conditions for the life of this important and effective species in the southern Alborz rangeland habitats. Therefore, in order to improve the conditions, the least that can be recommended in such conditions is to control the degradation of F.ovina species habitat, by managing livestock grazing and preventing rangeland use change, and in general, to apply a conservation approach in these habitats. If a protective approach is applied; It is to be hoped that climate change, by itself, will not be able to remove, undermine, or even completely eliminate this valuable species from the flora of the region, and perhaps the physiological, phenological, and morphological adaptations of this species will help combat climate change. Therefore, while protecting it inside the habitat, it is necessary to think of measures to protect it outside the habitat with an approach close to nature. In this regard, collecting seeds and storing them in the gene bank of natural resources, introducing superior and drought-tolerant ecotypes with better structural and functional traits and preparing strong seeds from them, cultivating them in small one-hectare plots in botanical gardens and plant collections And finally their rangeland in habitats with poor and very poor status class; One of the basic requirements is its protection outside the habitat with an approach close to nature.

This study was conducted to identify and analyze the effects of some invasive/undesirable plants on rangeland ecosystems. To analyze the risk of invasive species presence, on livelihood of the local people, a hierarchical analysis method was used. Factors used included 3 main criteria, 8 sub-criteria and 5 options. The main criteria were impact, invasion and growth potential. A linguistic scale was used to weight the criteria and options using the hierarchical analysis process. Questionnaires distributed among rangeland experts to express the degree of importance of the factors for evaluation. To check the accuracy of the criteria, compatibility ratio of each criterion was calculated in Expert Choice software. The results showed that Stipa capensis, Echinops dichrous, Alhaji mannifera, Peganum harmala and Carthamus lanatus had more destructive effects, respectively. The results of this study may be used for the control of invasive plants in rangeland ecosystems.

Measuring this year's growth is one of the basic requirements for calculating the annual storage potential of carbon. On the other hand, shrub plants, and especially Astragalus, are considered to be the most prominent and dominant species of semi-steppe rangelands. Therefore, the present study was conducted in June 2016, with the aim of estimating the growth of storage carbon in the Astragalus microcephalus plant and its relationship with the distance from the crisis center (overnight livestock area) in the Nazluchai mountain rangelands. For this purpose, Chir rangelands in the north of Noushin Shahr with an area of 1332 hectares, which in terms of vegetation, soil and topography, represents a level of various species in the region, were selected and six ecological sites were surveyed. Given that almost all of A.microcephalus species grow this year, it will become a woody organ; within each site, this year's growth of 30 A.microcephalus plant bases is intended to determine the organic carbon conversion factor and estimate the amount of carbon stored, it was cut off. After calculating the organic carbon conversion factor for biomass of plant bases on each site, multiplying it by the dry weight of this year's growth, the amount of organic carbon stored in the aerial parts was determined. By calculating the average carbon content in the bases and A.microcephalus species density, the amount of stored carbon per unit area of the habitat was calculated.