Journal of Arid Biome
Year:2014 | Volume:3 | Issue:2 |Papers Count:8

Urmia Lake located in the northwestern corner of Iran is one of the largest permanent hypersaline lakes in the world and the largest lake in the Middle East. This lake with the area of 4500-6000 km2, as the largest lake in Iran and Twentieth Lake in the world has a particular importance. The lake is full in danger of drying and in the recent years, height of the water level has decreased about of 7 meters. This study, estimated the changes of lake water salinity and modeled the lake salinity patterns by remote sensing techniques. For this purpose, the amount of water reflection values of landsats TM data was considered. Radiometric and geometric corrections were performed in the preprocessing stage. Furthermore, the range of variation of reflectance between bands correlation images were examined to investigate the effects of fluctuations in the defined time period. According to the results, the effects of salinity and the range of factors such as drought, excessive use of resources and procedures, and mismanagement is very clear. Based on the results a positive relationships between band 1 (450-520 nm), band 2 (520-600 nm), band 4 (775-900 nm) and salinity were found. In addition negative relationships between band 3 (630- 690 nm), band 5 (1550-1750 nm) were observed.

Phonological knowledge of species are important in rangeland management. The aim of this study was to determine the phenological stages of two species of Artemisia sieberi and Eurotia ceratoides in Nodoushan steppe rangelands of Yazd during the period of 4 years (2007-2010). First, for each species, 10 plants were identified within the enclosure and these plants were inventoried in the study process. Phenological characteristics of vegetative and reproductive stages at intervals of 15 days and 7 days, respectively, were measured. Based on results, the growth of sagebrush could be started in second decade of February. Flowering occurs during first to second decade of October. The milky seed continues until mid-November. Seeding of this species in the study area will be in December. Maximum canopy height was 50 cm, which is owned by the wet year, 2007, and at least it was 36 cm, which is related to the very dry year, 2008, and this difference is significant. Maximum and minimum canopy diameter, respectively 67 cm (2007) and 56 cm (2008) and did not differ significantly (P£0.05). Growth of Eurotia ceratoides started in the first decade of February. Therefore, This species appears in about 10 days earlier than Artemisia sieberi in the field and the lower the temperature needed for germination. Flowering occurs from the first to third decade of May. This seeding is the second decade of June to first decade of July. Maximum canopy diameter and height are respectively 56 and 42 cm in 2007. Minimum values of 57 and 37 cm has emerged, in the dry year of 2008, that there is no significant difference between them (P£0.05).

Mapping soil classes digitally generally starts with soil profile description with observed soil classes at a taxonomic level in a particular classification system. At each soil observation location there is a set of co-located environmental variables and a challenge is to correlate soil classes with environmental variables. The current methodology treats soil classes as ‘labels’ and their prediction only considers the minimization of the misclassification error. Soil classes at any taxonomic level have taxonomic relationships between each others. Using classification trees, we can specify an algorithm that minimises the taxonomic distance rather than misclassification error. Therefore, in this research, we have attempted to develop decision tree model for spatial prediction of soil taxonomic classes in an area covering 720 km2 located in arid region of central Iran. In this area, using the conditioned Latin hypercube sampling method, location of 187 soil profiles were selected, which then described, sampled, analyzed and allocated in taxonomic classes according to soil taxonomy of America. Auxiliary data used in this study to represent predictive soil forming factors were terrain attributes, Landsat 7 ETM+data and a geomorphologic surfaces map. Discriminant analysis was applied to calculate taxonomic distances. Results showed using the taxonomic distances led to achieve overall accuracy up to 70%. Results also showed some auxiliary variables had more influence on predictive soil class model which included: wetness index, geomorphology map and multi-resolution index of valley bottom flatness. General results showed that incorporating taxonomic distance into decision tree model had reliable accuracy. Therefore, it is suggested using of decision tree model with taxonomic distance for spatial prediction of soil classes in the future studies.

Cheetah (Acinonyx jubatus venaticus) is a threatened species that it’s population and distribution have decreased during last decades. Dareh-Anjir wildlife refuge is one of the known habitats of the species, therefore, studying on cheetah habitat suitability in this area can provide proper to predict distribution and habitats of the species. Ecological Niche Factor Analysis (ENFA) method and Biomapper software for habitat suitability modeling of this species by using presence point of the species were used.Data layers were provided as variables affect on presence of the species including slope, aspect, elevation, landforms, mean annual temperature, vegetation, water resources, development variables (such as villages and roads) and prey density. Results showed that 15 percent of the habitats of the wildlife refuge were suitable for cheetah. Based on habitat suitability layer cheetah prefer elevation ranged from 1200 to 1800 meters above sea level and slope ranged from 10 to 30 percent. Prey density is one of the affected agents on presence of the species. High specialization in the model shows that cheetah depends on restricted range of environmental condition and has specialized act in its habitat.

To select the best drought tolerant forage maize hybrid, an experiment was conducted in seed and Plant Improvement Institute (Karaj), in 2010. The experimental design was split plot based on randomized complete block with three replications. Three irrigation regimes (irrigating after 70, 100 and 130 mm evaporation from surface of class A pan) were considered as main factor and 14 maize hybrids (11 new hybrids and three commercial hybrids KSC700, KSC704 and KSC720) were assigned to the sub plots. Based on results, hybrid No.10 was tolerant in both mild and severe drought stresses and is suggested for further researches. Hybrid No.11 and 1 were the most sensitive hybrids in both mild and severe drought stresses and are not recommended for places with probability of drought stress during. Four indices of MP, GMP, STI and Harm have a high positive correlation with each other and forage yield in mild and severe drought stress can be used as indicators for choosing the best drought tolerant hybrids in the same conditions.

In this research, effects of Sodium NitroProside (SNP) and Salicylic Acid (SA) on some physilogical characteristics of Melia azedarach under salinity conditions were studied. Thus, a factorial experiment was conducted using a randomized complete block design with three replicates. Results showed that amount of proline and sugar in root and leaves significantly increased with increasing salinity. As a result, stem proline in concentration of 20 ds/m increased to 13 times more than control and application of SA and SNP decreased amounts of proline in this salinity concentration. The amount of solouble sugar in roots and leaves significantly increased with increasing salinity in concentration of 20 ds/m and application of SA and SNP decreased amounts of sugar. In contrast, K significantly decreased in leaves and roots. The amount of chlorophyl significantly decreased in concentration of 10 and 20 ds/m with increasing salinity. Application of SA did not change the amount of chlorophyl but SNP increased leaves chlorophyl. Increase in salinity also significantly decreased dry weight of root.

Extent of soil salinity in vast areas of the country, verifies the necessity of advanced techniques and tools for monitoring of salinity at different scales farm, field, catchment and national scales. Electromagnetic induction (EM) is a technique that can be used for mapping of soil salinity in bareor cultivated land condition with no extensive field works and large soil samples. The main objective of this study is to evaluate the ability of EM38 device for soil salinity mapping of 5, 000 hectares of the Yazd-Ardakan plain soils. For this purpose, soil samples were collected from descrete depths (0-15, 15-30, 30-60 and 60-100 cm) as well as vertical and horizontal readings of EM38 in sampled locations. Electrical conductivities of soil saturated pastes (ECe) were measured in the laboratory and then, relationships between EM38 readings and ECe were analyzed. Results showed that the EM38 instrument can be recommended as a rapid, accurate (R2>0.75), and RMSE=0.41) and relatively low cost technique for in-situ measurement of soil salinity. However, soil moisture should be considered as a major limitation for this technique.

Zeolites are crystalline, hydrated aluminosilicates of alkali and alkaline earth metals. They are further characterized by large tunnels for a fluid to pass through, large ion exchange capacity, the ability to lose and gain water reversibly. The atomic structure and surface properties of zeolites make them suitable for many industrial and agricultural uses. In this study the application effects of natural zeolite was studied at the early stages of plant growth for two rangeland species (Ziziphose Spina christi and Acacia Salicina) under drought stresses. According to results, the number of reminded plants decreased during studied period for all treatments, but a significant different was observed between control pots (0% zeolite) and pots treated with zeolite (P<0.05) for stream size and number of reminded plants.