نشریه خشک بوم
سال یکم شماره 3 (بهار 1390)

The objective of this study was to analyze the relationship between meteorological and hydrological droughts using related variables in the Zayandeh-Rud basin. Standardized Precipitation Index (SPI) and Surface Water supply Index (SWSI) were usede to evaluate the temporal and spatial variations of meteorological and hydrological droughts were used. Drought monitoring in the basin shows that the phenomenon has occurred in different years during the statistical periods. Andysis of the 12-months time scale of SPI proves the occurrence of the main drought in all of the basin area during the period of 1999 to 2001. The hydrological drought analysis also shows that the most severe drought has occurred between October 1998 to September 2001. Moreover، analysis of the correlation between meteorological and hydrological droughts indicates a difference in start time of droughts diagnosed by using these tow drought indices. However، this lag time is varied on average of 7 months with a variation of 3 to 11 months.

Saxual (Haloxylon aphyllum) as one of the main species used in the sand fixation and desertification projects can be grown in a wide range of desert soils in Iran. Considering the ecological needs of plants, including water requirements for establishment and long-term stability, is essential. In this research, biomass (shoot and root), shoot to root ratio (S/R) and canopy size were determined under different soil moisture regimes. One year old plants grown in drainage and weighting lysimeters in natural condition were subjected to three soil moisture regimes, viz. well- watered (100%), low- watered (30%) and less- watered (15%) of total field capacity. For determining the evaporation rate and its role in crop evapotranspiration, a lysimeter was used without vegetation. Water requirement content to reach the soil moisture to optimum level, provided by weighting of lysimeters and use of TDR, weekly. Biomass rate and ratio of shoot to root decrease significantly (P<0.001) with a reduction in soil water content. The effects of different treatments on canopy size were not significantly different. Calculating of the amount of the plant production per unit of water consumpted showed that black saxual (Haloxylon aphyllum) trees, need to 2.4 m3 water for optimal annual growth.

The limited water resources and available precipitations can be used in water storage process using modern and convenient water and soil management, such as compost, organic fertilizers, and polymers. In this study, the effect of physical soil amendments using superabsorbent polymer (in the four levels of %0, %1, %2, %3), and compost (in the four levels of %0, %0.5, %1, %1.5),on Haloxilon aphyllum plants.in the field condition by means of pots was assessed. The values of different traits including plant height, plant fresh and dry weights and root weight, internodes length and collar diameter were measured. The experiment was completely randomized design (16 treatments and four replications). In comparison with unamended soil, the compost-polymer amended soil showed promoted emergence, establishment and enhanced measured traits in plantlets. Values of plant water requirement index were significantly different compared to the control soil treatment. In Comparison with polymer amendment, the compost amendment shows more enhancements in the average values of the measured traits. However application of both amendments brought about greater results.

Wild goat (Capra aegagrus), the most typical species in the mountain area, is distributed in Iran. However, in arid regions, there are not any researches on the interrelationship of its species and habitat. In the Kuh-e-Bafgh protected area, wild goat is one of the main food sources for Iranian Cheetah (Acinonyxjubatus venaticus) (highly endangered species) and Leopard (Pantherapardus) (Endangered). The habitat suitability modeles investigate using Geographical Information System (GIS) and multivariable statistical analysis to study relationship between species presence and environmental variables. These models are used in Conservation Biology and results to the habitat suitability models have a major role in management of conservation programs and restoring of populations of wildlife species. Therefore, in this study,using Ecological Niche Factor Analysis (ENFA) and field observations and comparison of ecological characteristics of presence area of species (recorded 258 points presence wild goat in a random sampling method with commensurate classification, through the seven transects in different parts of the study area) with the ecological characteristics of the study area, habitat suitability model was prepared and mapped for the wild goat in the Kuh-e-Bafgh protected area with an area of 88,528 hectares. Results indicate that in the winter water resources, slope, aspect rocky areas, vegetation, and human variables (roads) have a major role in wild goat habitat suitability. The model was classified 27,379 hectares (%30.93) of the protected area as suitable areas for wild goat. In ecological Niche Factor Analysis (ENFA), the amount of marginality (1.053) indicate that the wild goat preferes the environmental conditions above the regional average. The amount of specialization (5.007) indicates that these species are dependent on the limited range of environmental conditions.

In this study, responses of three prosopis species to salinity stress in two life cycles (germination and seedling). In order to investigate the effects of salinity stress to germination, the experiment carried out based on the completely randomized design with 3 replicates and different salinity levels (0, 2.5, 8.5, 14 and 20 ds/m). Germination rate, germination percentage, roots and shoot length and weight in seeds and the amount of proline, sugar and chlorophyll in seedlings stage were measured. In the habitat of the species, seasonal changes of Na and K content of leaves were measured. Results showed that the germination rate, germination percentage, roots and shoot length and weight decreased in all species with increasing salinity stress. The highest and lowest germination characteristic accured in control and 14 ds/m treatments, respectivly. No germination occurred in salinity of 20 ds/m. P. juliflora and P. koelziana showed the highest germination rate in all treatments. P. juliflora showed the highest germination percentage and root length (except in 14 ds/m) of salinity. Results also showed that the salinity caused the accumulation of proline in all species. P. juliflora and then P. koelziana showed the highest accumulation of proline and sugar. The amount of sugar decreased in P. cineraria by increasing salinity. Chlorophyll decreased in all plant by increasing salinity stress and P. juliflora did better compare to two the others plants. Compared to P. cineraria and P. koelziana, P. juliflora accumulated highest Na and K. In summer, the accumulation of these ions in P. juliflora were higher than the other seasons. It can be concluded that although P. juliflora is a suitable plant for plantation in arid lands, great care should be taken for places that endemic plants are able to regenerate or plantation of them is easy.

Identifying indicator species and plant functional trait facilitate predicting ecological characteristics of arid and semi-arid ecosystems and help managers to introduce appropriate plant species in order to rangeland management reclamation. This study focused on indicator species related to three grazing regimes (exclosure, moderate and high grazing intensity) in steppic rangelands of Borojen, Chaharmahal and Bakhtiari province. Sampling was according to a random-systematic method in which the cover of plant species estimated within 10 plots established along three transects in each grazing regime. Plant traits include growth forms (annual forb and grass, perennial forb and grass and shrub), life form (Terophytes, hemi- cryptophytes, cryptophytes, chamaphytes and phanerophytes), vegetation structure (Rosette, semi-rosette and erect), plant palatability (Class I, II and III) and plant height. In order to identify indicator species and examine of changes in plant community composition, we used indicator species analysis and non-metric multidimensional scaling. Results of indicator species analysis showed that 16, 8 and 8 indicator species were identified for exclosure, moderate and high grazing intensity regimes, respectively. There were also indicator functional traits for each grazing regime including hemi-cryptophytes, cryptophytes, perennial grass and palatable plant class I was related to exclosure, annual forb, perennial grass and erect forb related to moderate grazing and finally annual grass, therophytes, rosette and palatability class III related to high grazing intensity. Results indicate that grazing was responsible for changes in indicator species and finally resulted in a significant shift in community wide trait composition. As a consequence grazing regimes can be identified using indicator species, however, several species and functional traits indicator should be into account.

Increasing demand and various uses of water resources has increased pressure on water resources. In addition, water use by one group of users has affects on usage possibility of other groups, so water resources management and its optimal allocation is very important. Undoubted, one of the most important tools for optimal allocation of water resources is economic valuation that emphasized in long-run development guidelines of water. Since decision making and allocation base on economic value amount have remarkable affects on micro and macro economic aspects of country, choosing the precision to choose method and its implementation is necessary. So, the aim of study, estimating water economic value in agricultural sections using production function approach in the Yazd-Ardakan plain. It illustrates departure in results providing inappropriate selection of functional form. Necessary data were collected from farmers with 154 questionnaires by stratified random sampling method. Next, various forms of production functions were estimated. Using econometric criterions, Translog production function was chosen for pistachio as best forms. Water economic value calculated for this crop is 310 Rial per cubic meter. Thus, total economic value of Water in this plain was estimated 109 milliard Rials.