فهرست مطالب

  • Volume:2 Issue:4, 2015
  • تاریخ انتشار: 1394/04/20
  • تعداد عناوین: 7
  • Vahid Feizi, Maryam Mollashahi, Manochehr Farajzadeh, Ghasem Azizi Pages 727-742
    Analysis of the spatial and temporal trends of precipitation and temperature are pertinent for future development and sustainable management of water resources in a given region. In this paper, we present a study concerning the climatic behavior of two principal observables Variables, viz. monthly temperature (maximum and minimum) and mean precipitations obtained from the measurements carried out in 60 Iranian meteorological stations for 40 years from 1969 to 2008. The Mann-Kendall test was used to detect the significant trends.Results showed that during summer and autumn, the precipitation had a negative trend (at 5% significant level) in the south-eastern parts of Iran and this trend is less during spring, but no special trend was observed in winter. The minimum and the maximum temperatures did not have any particular trend in winter. Spring was accompanied by an increase in positive trend in the maximum temperatures in the south-west and north-east, while the minimum temperature only limited in the south-west parts. Positive and negative trends of the minimum temperature were very dispersed during the summer. The maximum temperatures had a negative trend in the north-west and no positive trend was observed at 5% significant level. During autumn, the temperatures indices had positive and negative trends with a wide range of dispersion.
    Keywords: Climate change, Climatic variables, Iran, Mann, Kendall, Spatial distribution
  • Zahra Saiedyfar, Hamid Reza Asgari Pages 743-755
    Soil compaction has become a widespread problem in the world and it is considered as one of the main factors affecting land degradation in arid and semi-arid agricultural land. The aim of this study was to investigate the effects of soil compaction on soil carbon and nitrogen sequestration, physical (aggregate stability, saturated soil moisture content, bulk density, and porosity) and chemical (EC, pH, organic carbon and nitrogen) features. The treatments were applied in the form of the completely randomized block design with four independent variables and three replicates. The study treatments included: control treatment (no artificial compaction), T2 (2 times passing heavy tractor), T3 (4 times passing heavy tractor) and T4 (6 times passing heavy tractor). Toward this attempt, data was analyzed by means of the SPSS 16.0. Software package. The type of mean comparison method applied is the LSD test (at significant level of 5%). The results showed that different levels of soil compaction caused a significant effect on soil physical and chemical features. Based on the results, 6 times passing heavy tractor significantly reduced soil porosity and aggregate stability (respectively from 0.45% and 5.32 mm in control treatment to 0.255% and 3.88 mm) while this treatment (4) significantly increased soil bulk density as compared to other treatments(from 1.45 g cm-3 in the control to 1.97 g cm-3). Four and six times to-and-fro passing heavy tractor caused a significant reduction in soil carbon and nitrogen sequestration respectively from 3.26 t ha-1 and 149.62 kg ha-1 (in control) to 1.70 ton ha-1 and 48.16 kg ha-1for T3 and T4 treatments, but significantly increased EC in comparison with other treatments (changed from 0.58dS m-1 in control treatment to 0.83dS m-1 in T4). Also, all soil compaction treatments significantly increased soil pH. For example pH increased from 7.93 in control to 8.09 inT4. While soil compaction treatments resulted in significant decrease in organic carbon, total nitrogen and saturated soil moisture values.
    Keywords: Artificial compaction, Land degradation, Soil feature
  • Narayan Gautam, Manohar Arora, Nk Goel Pages 757-765
    Precipitation data is of utmost importance to carry out many hydro-meteorological studies. Observed warming over several decades has been linked to changes in the large-scale hydrological cycle such as: increasing atmospheric water vapour content, changing precipitation patterns, intensity and extremes, reduced snow cover and widespread melting of ice, and changes in soil moisture and runoff. Precipitation changes show substantial spatial and inter-decadal variability. General Circulation Models (GCMs), representing physical processes in the atmosphere, ocean, cryosphere and land surface, are the most advanced tools currently available for simulating the response of the global climate system. Recent interest in global warming has also increased concerns about the possible changes in rainfall amount including floods and drought patterns. This study is based on statistical downscaling, which provide good example of focusing on predicting the rainfall using the input of coarse GCM outputs. In this study, we have used GCM outputs for predicting the rainfall. It is obtained from the study that predicted rain values are higher for the first 30 years in compared to remaining prediction periods. The result has shown that winter rainfall may highly decrease in compared to monsoon, post monsoon and pre-monsoon seasons.
    Keywords: Downscaling, General circulation model, Global warning, Rainfall Prediction
  • Javad Mirzaei, Najmeh Noorbakhsh, Abdolali Karamshahi Pages 767-777
    To identify arbuscular mycorrhiza fungi (AMF) associated with Crataegus pontica C. Koch, 54 soil samples were collected from the rhizosphere of this plant in Ilam Province, western Iran. Isolation of mycorrhizal spores was conducted by wet sieving followed by centrifuge. AMF were identified based on morphological characteristics of spores. In this study, 13 species of AMF belonging to five genera (i.e. Acaulospora, Entrophospora, Glomus, Funneliformis and Claroideo glomus) were identified. The result showed that Acaulospora was the most dominant (30.77%) isolated from the rhizosphere of C. pontica. The Glomus caesaris andClaroideoglomus etunicatum had the highest (17%) and G. pansihalos had the lowest (3.7%) frequency in this study. Results indicated that AMF spores had high variation in the rhizosphere of C. pontica.
    Keywords: Acaulospora, Arghavan valley, Dinar, kooh, Spore
  • Yahya Kooch, Theresa Theodose, Pavel Samonil Pages 779-803
    Studying forest degradation through evaluation of soil nutrient concentrations, which reveals soil functioning within the ecosystem, is necessary for sustainable management of land resources. This research was conducted to understand the changes of soil nutrient, resulting from exploitive management using some soil features and their spatial pattern. In the mid-summer of 2014, two sites were selected consisting of an undisturbed forest site (FS) and a completely deforested site (DS); both sites were in lowland part of Khanikan forests located in Mazandaran Province, north of Iran. Within each site 50 soil samples were obtained from 0-30cm depth along two sampling lines with 500 meter length thus resulting in 100 soil samples for each site. The interval between samples along lines and also the distance between lines were selected 10 m. The mean pH was lower at the DS (5.70) than FS (6.58). The mean of soil organic carbon (SOC) was significantly higher at FS (2.78 %) when compared with DS (0.56 %). Total nitrogen (N) also followed the same trend having significantly higher values at FS (0.28%) than DS (0.16%). Mean available phosphorus (P) values were significantly higher at the FS (17.33 mg kg-1) than at the DS (7.24 mg kg-1). The amounts of available potassium (K) were significantly higher at the FS (148.15 mg kg-1) than DS (84.14 mg kg-1). A geostatistical analysis revealed that deforestation changed the spatial variability models and fractal dimension of soil features. As a conclusion, the spatial variability of soil pH and SOC were more imposed by deforestation compared to the other soil features. Our results suggest that deforestation should be regarded as an effective factor on variability of soil nutrient that are tied to forest ecosystem management.
    Keywords: Forest degradation, Fractal dimension, Geostatistics, Soil chemistry
  • Ali Ariapour, Abdul Rashid Bin Mohamed Shariff Pages 805-818
    Conflagration of forests and rangelands is one of the most frequent events in Iran. It is regarded as one of the most important parts of land degradation that occurred due to range destruction and desertification. This study was conducted in Boroujerd, Lorestan Province in west of Iran in 2013 to determine the fire risk model. The data prepared for the study area involved the vegetation types, land use, elevation, slope, aspect, standard topographic map and mean annual climatic data (evaporation, rainfall and temperature). Landsat ETM+ data were used for the image analysis. Analytical Hierarchical Process (AHP) model was applied to weigh and generate the fire risk map. Results showed that the highest weight of factors has been given to the land use because land use contribute to the maximum extent due to inflammability factor. The second highest weight was related to rainfall since it caused the biomass growth (fuel factor). Land use and rain played important roles in the modeling of fire risk zonation. The third one was attributed to the evaporation because of fuel drying and highly inflammability. The other variables comparatively had less impact on fire risk. Based on the statistics achieved for different weight classes, the map was reclassified into five classes as very low, low, moderate, high and very high in order to generate fire risk area map. Also, final map showed that most of the fires which occurred in the last year (5 fire control points about 4812.323 ha) might be put in the firing class of very high risk. Finally, about 42353.36 ha of the total area fell in the class of very high fire risk. The results indicated that 90% of burned areas were located in high risk class.
    Keywords: Analytical Hierarchical Process, Conflagration, Risk zonation, Satellite Images
  • Mahdieh Ebrahim, Iraj Rahimi Pordanjani, Pejman Tahmasebi Pages 819-831
    The present study was conducted to assess the effect of dung beetles on sheep dung removal and seed dispersal in semi steppe rangelands of Shahrekord province with poor condition located in Iran. Therefore, the large (1 cm2) and small size (1 mm2) meshes were used and filled by sheep dung in six treatments. To evaluate the role of the insects in seeds translocation, three sizes of plastic beads used as seed mimic. The results illustrated that the maximum function of the insect was observed in the possible treatment of the presence of dwellers, absent of large tuneller and large roller beetles and present of small tuneller and small roller beetles. The least dung removal was calculated in the control treatment and possible treatment of dwellers, large and small tunneler and also absent of large rollers and presence of small rollers respectively. Seed removal decreased in the order of small size (29) > medium size (5) > large size (2). In general, dung beetles play an important role in dung removal and secondary seed dispersal, but their function relates depended on habitat condition. In a degraded ecosystem, this insect will disappear. Considering the various factors affecting the function of these insects, further studies would be needed for investigating deeply different seasons and dung of different livestock feeding on the rangelands.
    Keywords: Decomposers, Rangeland ecosystem, Scarabaeoidea, Seed fate