Desert
Year:2005 | Volume:10 | Issue:2|Papers Count:16

Drought is a silent phenomenon of the nature which occurs at global scale level but acts at local scale. This phenomenon is observed in vast zone of Iran with different forms, or may be occurred in the future. It will bring limitation, decrease and deficit fresh water resource, limitation of crop yield and noncrop yield, changes time and location to increase and decrease precipitation, increase of evapotraspiration etc.This phenomenon causes non natural equilibrium at regional and zonal scale. The results of this phenomenon are environmental pollutions, species change, wetland drying, increase of diseases, poverty and famine. The progress is slow-moving with negative effects. The droughts are classified as: meteorological, hydrological, agricultural based on social, economic and environmental impacts. Several approaches can be used to assess the severity of drought. For study, this paper used description-analysis, Normal Percent Index (willike-1994) method. So, for statistic calculation and mapping, aridity index and time series from Minitab 14.2, winsurfer8 software (GIS) were applied.Result of this research has showed that plain and coastal areas are in drought condition and hilly lands and mountainous area are in wet condition.  

Salinity is a growing problem in agricultural soils that affects plants growth and development. Salinity reduces substrate water potential, thereby restricting water and nutrient uptake by plants. In this research, the effects of salinity on germination, fresh and dry mass accumulation, starch, soluble sugars, praline and ion content of the halophyte Suaeda fruticosa were investigated. To determine the effects of salinity, seeds and seedlings of this plant were exposed to 0, 100, 200, 300, 400 and 500 mM NaCl. The results showed that by increasing the salt levels, the germination rate decreased, and in 500 mM NaCl it was blocked. Treatments from 100 to 200 mM NaCl increased fresh and dry mass compared to control, higher salinity levels declined fresh and dry mass accumulation. Increases in soluble sugars, praline, Na+ and Cl- content and decrease in K+ content were resulted from salt increases. Also, salinity did not affect starch content of this plant significantly.

To investigate the effects of sodium chloride on two wheat (Triticum aestivum L.) cultivars, four levels of salinity: 0, 4, 8 and 12 dS/m, were employed as a factorial experiment arranged in a randomized complete block design with four replication in a controlled environment of the greenhouse during 2003-2004. The results indicated that increasing salinity from 0 to 12 dS/m, decreased emergence percentage, significantly. The two cultivars (Kavir & Shiraz) responded differently to salinity, so that Kavir showed significantly higher emergence rate. This cultivar (Kavir) also had greater shoot potassium content. The number of tillers and leaves per plant and also the plant height were decreased upon increasing salinity level. The shoot sodium chloride content was also increased by increasing the salinity level in both cultivars, however, the sodium content of Kavir cultivar, compared to Shiraz cultivar, was lower probably due to Na+ exclusion mechanisms in this cultivar. The results also revealed that the highest grain number and phytomass was obtained from Kavir cultivar at the lowest salinity level. Phytomass and grain yield were also decreased upon salinity significantly. Overall, it appeared that less adverse effect of salinity on Kavir cultivar may make it more suitable for growth in saline soils found in the investigation. 

One of the most important factors, affecting desertification process is soil and water salinization, which is the result of different natural and human effects. According to our studying, the region of Brom (Damghan) was selected. At first step the boundaries of this region were characterized with using GPS, then work units were determined for field survey and also soil sampling in 15 units were done according two factors planting pattern and water resources in each unit. The soil profile was prepared and soil samples were obtained from different depths (0-50cm, 50-100cm, and 100-150cm). For study of water resources in this region some samples were obtained from7 wells and also from upland runoff, then soil and water samples were analyzed and some parameters were measured.Then according to data base, geological map, topography map, work unit map, measured data of soil and water and also field studies, schedule of soil and water salinizatian and status of region were investigated.Water salinization factors in this region are geological formations in place of aquifer recharge and climatic conditions. Important factors in soil salinization in region include: Irrigation with saline water, improper irrigation method, unsuitable planting method, climatic condition and land form.  

Cotton is one of the agricultural plants resistant to salinity. It is absolutely necessary to conduct a consistent research on many of the resistant plants to salinity. An experiment was performed about the effect of different sea water salinities cosentrations on growth and yield of cotton (Sahel cultivar) in respect to the sea water advance towards the seaside lands. This experiment was done in greenhouse of Agricultural College of Sari in 2003. The experiment was performed in the factorial form in a completely randomized design. The factors were the different irrigation times at four growth stages (seedling, 2-leaves, 4-leaves and 6-leaves stages) with different concentrations sea water salinity (3.6,4.2 and 5.5 dS/m). The results of this experiment showed that the sea water irrigation has a dramatic effect on many of cotton growth characteristics. In this research, the stem height, nod numbers, plant biomass, the cotton first harvest yield (p<1%) and the cotton second harvest yield (p<5%) were affected by the irrigation times. The different salinity levels also affected some growth characteristics as: stem height, plant dry matter, cotton yield of the first and second harvest (p<1%) and stem diameter (p<5%). In study the interaction effects on cotton yield, only cotton yield of first harvest was affected by that as it caused to significant difference at 5% statistical probability level. Interaction effects of salinities levels treatments and irrigation times levels treatments on other studied cotton characteristics were no significant differences.

Physiological effect of seven levels of salinity (0, 50, and 100, 150, 200, 250, 300 Mm Nacl) was studied on seed germination, plumule and radicle lengths in two different Agropyron species (Agropyron elongatum-Agropyron afghanicum). Total of 25 seeds of each Agropyron species were sawn. Experimental design was factorial with complete randomized design. The results show that maximum germination rate was obtained at (0MmNacl).Germination rate, plumule and radicle lengths were declined with increasing of salinity concentration. Agropyron elongatum was found to be more resistant to salinity stress compared to other species.

Drought is an ecological fact in Iran. In many arid and semi-arid regions of the country, lack of rainfall along with uneven spatial and temporal distribution of rainfall, cause poor vegetation coverage. Salinity is another problem in these regions. It is mainly caused by high evaporation rate. Due to an increase in population and "- demand for more food, it is necessary to rehabitant the rangelands. Success will be achieved only by using relevant species of saltbush. Atriplex spp. is among the saltbushes cultivated widely in different parts of the country (esp. in arid areas). The object of this research is to study the interchange effects between soil properties and plant characteristics. In this study planted plots with Atriplex canescens were compared with control ones. The effects of plantation Atriplex on soil characteristics were compared by analyzing three series of samples from soil (under shrubs, between the rows and control plots). Also plant height, density, coverage, annual wet and dry biomass were measured and compared in both regions for environmental the effects on shrubs. Some factors of nutritional values were determined in the lab. For determining the effect of Atriplex saltbush on the native plants, vegetated and control plots were compared. The results show that Atriplex had different effects on vegetation community and plant characteristics in both regions. Analysis of the soil samples showed that some properties of the soil have been changed.

According current situation of Iran, if range condition and ecological potential of rangelands considered as limiting factors for establishment of a productive system, social unit can be considered as the base of sustained utilization development which warranty economical investment and balance between range and animal So it is essential that economical size of range property be determined according to social units requirements and ecological potential, climatic and cultural conditions. Based on ecological and climatic condition and as a result, different range production, living cost of families is different. For determination of minimum property size in Markazi province 31 range properties in three different climatic zones were selected. According to the results, living cost of a family with 6.3 sizes was 16859thousand rials per year. Net income of a herd of 100 sheep and a herd of 100goats per year were 3023 and 140thousand rials respectively. To cover living cost of a family with the size of 5 persons 40-50 animals is required. To feed the animal required for each family minimum range areas of 715-890'hectares in arid areas, 555-695 in semi - arid areas and 666-833 in Mediterranean climate based on range condition is required. Ignoring climatic condition generally in Markazi province based current range condition, living level and accessing to rangelands minimum property size of 700- 900 ha for arid areas, 550-700 ha for semiarid areas and 650-850 ha for Mediterranean climate for each family was determined.

In this research, using regression equation, the relationship between climatic elements and the necrosis of date palm bunch in Kahnooj, Bam, Jiroft and Busher has been investigated. The used elements are rain, relative humidity and temperature. The results of this research show that among all of the climatic elements, relative humidity has the most relation with the necrosis of date palm bunch. That is, when about one percent of relative humidity increases, the rate of damage will be decreased (about%20). As a whole, decreasing the relative humidity and increasing the temperature are the main reasons of necrosis of date palm bunch.

The aim of this research was to investigate the relationship between environment characteristics (soil factors) and vegetation cover to determine the most important factors affecting vegetation cover in different vegetation types. The studied area located in Voshnaveh Rangeland in Qom province. The six vegetation types selected as indicator stands in order to investigate soil-plant relationship. Method of sampling was random- systematic and measured vegetation parameters such as canopy cover and density were measured, The area of each plot was determined according to kind of plant species and distribution of plant to use minimal area. Soil samples were collected from two layers of 0-30 30-60 depth to determine texture, percent of lime, EC, acidity, organic matter, nitrogen percentage, potassium, phosphor and gravel percentage of soil. Statistical methods were included analysis of variance, multivariate regression and principle component analysis and to analysis soil and vegetation data were used SPSS, and MINITAB soft wares. Results show specific relationship between soil factors and vegetation cover although correlation is not 100%. As a total conclusion, plants have a positive tendency to factors which help to absorb nutrient and water .Analysis of regression and correlation show that organic matter, texture, and gravel percentage were the most important factors effective on separation vegetation types respectively in study area.

Addition of organic materials of various origins to soil is one of the most common practices to improve soil physical properties. In the green house, the impact of organic and inorganic fertilizers on physical properties of soil after Plantago ovata harvest was assessed. The treatments were two rates of each cattle manure (4,8 ton/h), municipal waste compost (4,8 ton/h) and four rates of inorganic fertilizers (N30P10, N30P20, N60P10, N6oP20 Kg/h) and a control with three replication for each treatment. Soil physical properties were significantly affected by organic fertilizers. The compost and manure treated soil significantly decreased soil bulk density compared to inorganic treatments. The water holding capacity and porosity and microspores were the highest in compost treatment, but macrospores were the highest in the manure and compost treatments. In this study Organic fertilizers had more positive effects on soil physical properties than the inorganic fertilizers. The impacts of compost due to the higher C/N ratio and carbon and organic matter increase in soil were higher than the cattle manure.

Drought is one of the most serious natural hazards that have more effect on human societies than the others. There are several meteorological drought indices for drought study. Although no index is superior to other indices in all circumstances, but every one has been developed for specific aims. The study of drought using different indices may conclude to the different answers for the existence and nonexistence of the drought and therefore some of them are better for special applications and areas.In this paper, the applicability of different indices viz. Z-Score, PNPI, DPI, RAI and SPI were assessed in Bakhtegan, Tashk, and Maharlo lakes watershed. The above five indices were calculated using monthly precipitation data from 8 meteorological stations during 30 years (1970-99) for 1, 2, 6, 9 and 12 month basis. Then monthly indices were changed into annual scale. The correlation matrix among indices as well as minimum precipitation, average and standard deviation were used to select the most suitable index. The results showed that DPI and PNPI classified the least annual precipitation in time scale in severe and extreme drought in all study stations and these indices have had less standard deviation and more mean values compare to other indices and therefore have more efficiency to other indices for meteorological drought determination.

In this study, germination characters and growth of two halophytic species Atriplex canescens and A. halimus at different temperature regime and salinity concentrations were investigated. In both species, germination and growth were decreased with increase of salinity in different temperature regimes. At optimal temperature regime of 25:10, A. canescens seeds showed 82% germination at 0mM NaCl and 14% germination at 500mM NaCl. A. halimus showed 86% and 19% germination at 0mM and 500 mM NaCl, respectively. In both species, rate of germination decreased with an increase in salinity at all temperature regimes, but most germination rate was obtained at 25:10 regime. The least value of first day germination index showed in both species, at optimal temperature. Also root length and hypocotyls length decreased with increase in salinity. At high temperature regime, difference between root length and hypocotyls length was less.

It is believed that the fertility of soils has been lost due to the soil erosion between 8 to 100 percent. In Iran, soil erosion has also imposed many damages on arable lands. Although there is no land limitation regarding to the vast area of Iran, but fertile soil is a limited factor. Varamin plain in Tehran province is an example. The reclamation and degradation elements of its soil have different effects on lands. In this research, northern and southern parts of Varamin plain were studied. These lands show productivity variances to the agricultural products due to existing of different mineral and organic elements. Identifying these elements, we studied different effects on Varamin plain lands and compared their fertility. This study showed that northern part has more reclamation and lower degradation factors compared to the southern part. Moreover, soil surface layer has more reclamation and degradation factors compared to the subsurface layer.

Tabas basin with 507 Km2total areas is in southern part of Khorasan province. It is located between 56 42 to 75 42 E and 33 17to 33 45 N.Regarding to the role of vegetation on sand dune fixation, this study revealed the vegetation and soil relationships. In this case, in addition to field survey, topographic maps, land capabilities, geology and other data sources were used. The distribution of Haloxylon species and soil factors including gypsum percentage, lime percentage, saturation percentage, salinity, acidity, surface and depth gravel percentage were determined through soil sampling. The equation delineating plant density was computed using Multiple Regression Analysis.The results reveal that there is a significant relationship between vegetation density and the soil properties. It shows that the correlation rate is different depending on the soil properties.

BIABAN as one of the scientific Journals has been published in International Research Center for Living with Desert, University of Tehran since 10-year ago. It covers subjects related to the agriculture and natural resources fields. In this study, in order to assess this Journal, all papers published from 1996 to 2005 were considered. Three parameters including "participation of institutions", "scientific ranks of authors" and "diversity of subjects" were assessed. The results showed that universities located in Tehran have sent more papers compared to the other universities of the country. It can be also concluded that the universities submitted more papers than other research institutes and centers. The authors with "Professor" rank have published more papers compared to the other ranks. This shows the appropriate scientific background of this Journal. Regarding to the diversity of subjects, from ten selected categories, all had the same proportion except architecture of deserts and plant science subjects which had the lowest and most proportions, respectively. Totally, it can be said that each active institute has some negative and positive points in which authorities must strive to enhance positive and decrease negative points. This Journal is going to commence its eleventh year of activity. In this regard, the relevant authorities of Journal should improve the quality and quantity of Journal more and more to change it into ISI.