نشریه مهندسی اکوسیستم بیابان
پیاپی 10 (بهار 1395)

The current study addresses determination of occurrence optimal thresholds of predictive models of plant species distribution in Nir rangelands of Yazd province. Accordingly, after determination of homogeneous units using digital elevation model and geology maps with scale 1:25000, vegetation sampling was carried out using random systematic method via plots which establishment across 3-5 transects with 300-500 m lengths. In order to sample the soil at each habitat, eight holes was drilled and samples were taken from 0-30 and 30-80 cm depths. Measured soil properties included gravel, texture, available moisture, saturation moisture, organic matter, lime, gypsum, pH, electrical conductivity and soluble ions. Plant distribution modeling was conducted using LR, the MaxEnt and ANN. After preparation of predictive maps of plant species habitat, an occurrence optimal threshold was determined using sensitivity-specificity equality approach and Kappa maximization approach for each plant species. Then, the compliance of classified maps with real maps cover was measured using the kappa coefficient. Based on obtained results, accuracy of predictive maps derived from different methods is different from each other. Among derived maps from LR, MaxEnt and ANN methods, the highest compliance belonged to the C. monacantha (κ= 0.9), R. ribes-A. sieberi (κ= 0.93) and S. rosmarinus (κ= 0.93), respectively. These results indicate that due to differences in the discriminatory ability of the model to classification of the presence or absence, occurrence optimal thresholds of plant species is different in various species, therefore, in order to determination of occurrence optimal thresholds, quality of predictive models should be considered in addition to the research objective and abundance of studied species

Groundwater is a valuable resource both in the Iran and throughout the world. Drought as a natural and inevitable phenomenon, frequently occur in the different regions of the world, especially in the hot and dry area. It lead to economical, social, and environmental damages. Drought should decrease groundwater recharge. In main aim of this study was to investigate the effects of drought on groundwater resources using Standardized Precipitation Index (SPI). The longest period of drought, the number of drought months and large drought period (DM) in supercritical Kashan plain were studied. To investigate the relationship between drought and groundwater level, period 1991 to 2010 was selected based on the available data. Also a significant relationship was observed between groundwater level decreasing and drought index, but in the groundwater depletion, the role of the over exploitation is more important than drought effects. We can conclude that the only basic principal method of preventing dangerous consequences of groundwater depletion is proper and lawful consumption of water to avoid uncontrolled withdrawal of groundwater.

Species relative abundance have closely related to ecological niche of plant communities. The broader specie ecological niche for food sources the greater relative abundance of plant species. Species abundance distributions models can be are divided into two groups Statistical and biological models. In this study we aimed to investigate how animal grazing (Long time grazing exclusion, Grazing and Short time grazing exclusion) could change species abundance distribution based on biological models such as Dominance decay, MacArthur fraction, Power fraction, Random fraction, Random assortment, and Dominance per-emption. Ecological niche apportionment models were presented according assumption that species abundance is a ratio of resources (Niche) that allocated to a species with its entrance to community. Vegetation data was sampled in each region using of 40 plot (1*1 m2) across four 100m transects based on systematic random sampling. Data analysis was performed in R software and “nicheApport” package according Monte-Carlo test. The results showed that random fraction model were appropriately fitted to observed frequency of species distribution in Grazing and grazing exclusion Short- time grazing exclusion

Discovering ecological factor of desert indicator specific species is considered as an applied study aiming to shed light on edaphic and ecological factors influencing the very labor ever and their management. In the Land of sandy desert soil conditions are very compatible with special herbs, growing and one of the most important species is Stipagrostis pennata That of the family Poaceae. In the current research climate of the study area is cold dry. A random systematic design has been applied in 4 sites called A, B, C, and D within a distincthabitat of S. pennanta. The most important ecological factor for the growth and distribution of Sand plain desert region as a dominant species and communities of habitat, species Soil compatibility with sandy hair root sheath and the development of the root system in wide area network. Studies have shown that in addition to the impact of the consolidation of sands. The results show that there is a direct relationship between the amount of nitrogen and growth properties off S. pennanta.

Plants, in arid and semi-arid regions, are leading to form the Nebka geosystem using the decrease of wind speed and the stabilization of quicksand, which they play an important role in desert greening and protection of the environment and natural resources. Therefore, identification of plant species adapted to the environmental conditions in format of Nebka efficiency assessment is very important for stabilizing the quicksand. Hence, this study tries to assess the Nebka efficiency in Negar plain of Bardsir using AHP and TOPSIS models comparatively, till we can be achieving an optimal recognition for the selection of the most suitable plant species to stabilize the quicksand. In this regard, at first the most important morphometric parameters of 241 Nebkas from Tamarix macatensis, Calligonum comosum and Alhagi mannifera species, including the height, base diameter, slope, and volume of Nebka and canopy cover and height of plant, were sampled via transect method. Then, Nebka morphometric parameters were assessed and prioritized using TOPSIS and AHP models. The results show that based on the AHP model, Tamarix mascatensis Nebka with the weight of 0.676, has the most importance and priority to the stabilization of sands. Also, Calligonum comosum with the weight of 0.269 has less importance than the Tamarix mascatensis and more importance than Alhagi mannifera. The results of TOPSIS model show that Tamarix mascatensis species, with relative proximity 1 to the ideal, have the highest priority in stabilizing the quicksand. Also Calligonum comosum species with relative proximity 0.5 to the ideal is the most preferable after Tamarix mascatensis species. However, according to the results of the two models, Tamarix mascatensis and Calligonum comosum species can be suggested as a suitable species for stabilizing the quicksand via the development of Nebka geosystem in the study area.

Assessment of land use changes in the previous years and prediction of these changes in the following years is an essential tool for different planning and management of natural resources. Therefore, the aim of present study is modeling of land use changes in Mehran Plain using Markov- Cellular automata Model in 2028. In order to detect land use changes in the studied area, TM and ETM satellite images of Landsat were used during three time periods of 1989, 2002, and 2015, and a separate map was prepared for each year. Then according to model, 2015 land use map was provided. Assessment of the match between simulated and actual map of 2015 with kappa index showed that this model is an appropriate model for simulating of land use change. After that, land use map for the year of 2028 was simulated. The results showed that in 1989 to 2015, the area of agricultural lands and the area of very poor range lands have been increased up to 6778 and 5961 hectares, respectively. In contrast, the area of poor range lands has been reduced up to1534 hectares. The results of prediction showed that during the next 13 years, the area of agricultural lands and bare lands will increase about 1177 and 389 hectares, respectively. Poor range lands will decrease about 1950 hectares.

Natural resource management is requires update and accurate information. Thus, monitor changes would have help to optimal management of natural resources and accurate recognition of resource changes. In this study, using digital data MSS (1977), TM (1988), ETM (2002) and OLI (2014) studied hamoun wetlands and land cover Its surrounding changes over a period of 38 years (2014-1977) using the comparative after classification method (post classification) and was predicted land cover map for 2025. Land cover mapping was conducted after pre-processing and processing satellite images, creation of training samples and assessing maps accurate was done by coefficient kappa and overall accuracy. Results of wetland changes and its surrounding land cover showed that wetland changes Has been negative in the first and second periods but, changes has been positive and wetland moved forward to revive in the third period. Generally, during the whole period the trend of wetland changes has been destruction. Land cover changes, canebrake, Barren lands classes and Saline Soils reduced and only will increase vegetation class. This study also can be used as a pattern for other studies to predict ecosystem changes in arid regions should be used.

Investigation of changes in groundwater resources is of great importance in planning and sustainable management of water resources. Knowledge on the relationship between groundwater and drought is prerequisite for water resources management. In this study, climatic variables including evaporation, temperature, precipitation as well as hydrological variables i.e. discharge and groundwater depth from 50 piezometric wells were used for the period of 1992-2015 in the Shar-e-Babak plain, west of Kerman province. The SPI index, the longest period of drought and the number of years faced drought were calculated at first step. Then, trend of SPI index variation, evaporation, discharge and groundwater depth were determined using Mann-Kendall non-parametric trend test. Correlation coefficient was also investigated between groundwater depth, SPI index, evaporation and temperature. Results showed that trends of groundwater depth, evaporation, discharge and drought index were decreasing in most stations during the past 33 years. Evaporation and temperature were not significantly correlated with groundwater depth, but there was a positive correlation between groundwater depth (dependent variable) and SPI index (independent variable) on the scale of 48 months. The highest correlation and regression coefficients were 0.439 and 0.51, respectively, at 99% significance level indicating direct effect of drought on groundwater level in Shahr-e-Babak plain. Changes in groundwater depth in association with drought severity and duration as well as decreasing trend indicate that all six stations were facing drought. Among the criteria in SPI index, drought duration was recognized as an appropriate criterion for indicating drought conditions in the study area. It was found that in addition to excessive use of groundwater, prolonged drought periods has more destructive effect than shorter periods on drop of groundwater level.

The main parts of Iran have been countered in arid and hyper arid area that in result of especial environmental condition as low precipitation and vegetation density can be caused wind erosion, whereas wind erosion usually has a tiny destruction quantity than water erosion due to wide its activity. Because of not matching presented models by other countries with climate and edaphic condition of our country, empirical model of IRIFR.E. A was offered. In this model nine effective factors in sedimentation of wind erosion are studied and then sedimentation of wind erosion is determined for each working unites, sub basins and basins. In this study, the IRIFER.E. A empirical method used for investigation of wind erosion classes in Ala region of Semnan. To reach this goal, scores of determined working units in this region were measured according to nine factors affecting this method. With considering the results, the highest score obtained from working units of waterway and clay land with Kalootak included annual sedimentation about 4443.2 and 5212.6 tone/Km2 respectively. Therefor 2.5 %, 48.23 %, 19.98 % and 29.19 % of region have a minor erosion (very low), low erosion, medium erosion and high erosion respectively