نشریه علوم آب و خاک (علوم و فنون کشاورزی و منابع طبیعی)
سال شانزدهم شماره 3 (پیاپی 61، پاییز 1391)

Global solar radiation (Rs(on a horizontal surface in the estimation of evapotranspiration of plants and hydrology studies is an important factor. Average daily global solar radiation on a horizontal surface was estimated by artificial neural networks (ANNs) and five empirical models including FAO (No. 56)، Hargreaves-Samani، Mahmood-Hubard، Bahel and Annandale. The weather data was selected from Karaj، Shiraz، and Ramsar weather stations، which have arid، semi arid and very humid climates (based on De Martonne classification). Daily solar radiation was measured at the three sites selected. The ANN، with actual duration of sunshine and maximum possible duration of sunshine as input parameters، generated daily solar radiation estimates with highest level of accuracy among all models tested. Rs estimates by ANNs with only temperature indices as input and by Hargreaves-Samani، Annandale and Mahmood-Hubard، which are all temperature oriented models، had lower accuracy at all three sites. In contrast، ANNs with actual duration of sunshine and maximum possible sunshine hours as inputs in Karaj، Shiraz and Ramsar station with root mean square error (RMSE) of 2. 08، 1. 85 and 2. 05 Mj m-2 day-1 respectively were the best models. After ANNs، FAO-56 model which is based on sunshine hours produced results closer to the measured values. Rs estimates by ANNs with only temperature indices as input and by Hargreaves-Samani، Annandale and Mahmood-Hubard which are all temperature oriented models، had lower accuracy at all the three sites. These models are not appropriate for estimating daily global solar radiation.

There are different automatic downstream control algorithms developed to increase the flexibility of the irrigation system. CARDD control logic is one of the heuristic and distance automatic downstream control systems. In this research، mathematical model of the CARDD control logic coordinated with ICSS hydrodynamic model was developed and the CARDD control logic was tested and evaluated under different situations. In order to evaluate the performance of this control algorithm، one of the canals suggested by ASCE (canal number 2) was used. The CARDD control algorithm was tested under the operational scenarios suggested by ASCE in which the control algorithm was evaluated by intense and gradual flow changes in a newly constructed (tuned) canal. Performance indicators were calculated and analysed. In the case of gradual flow changes، the maximum diversion of the water depth from the target was about 5% and was always in permitted range. In intense flow changes، the maximum diversion of the water depth from the target was about 8% and it was recovered in about 1 hour، which is a considerable time. The charts showing the variation of water depth at each turnout and the calculated performance indicators showed the satisfactory performance of CARDD control algorithm in gradual flow changes. In intense flow changes، although the maximum variation of the water depth was limited، the system response time was relatively long.

Internal erosion is the second major reason for earth dam''s failure after overtopping. One of the effective factors in internal erosion in earth dams is the clay minerals used in dams as well as the effects of compaction efforts on soil in sample preparation. In this research، internal erosion and the effect of clay minerals and compaction effort on internal erosion were investigated. For this purpose، Kaolin clay and Na Montmorillonite (Bentonite) separately and with different percentages of mixture were used to investigate the effect of different percentages of Bentonite on internal erosion. Two hammers of standard compaction and modified compaction test were also used to investigate different compaction efforts in internal erosion. The results showed that as compaction effort increased in constant water content، erodibility also increased to about 3%. In addition، it is found that erodibility of kaolin clay is more than bentonite، which reaches 65%. Finally، by adding 12% bentonite to kaolinite، erodibility decreased to a great extent.

Rivers as a main sources of supplying water for urban areas، agriculture and industry، are very important. This point reveals the necessity of the control، improvement and solving the problems of rivers، especially all problems relating to water quality. In this study، transport of the suspended sediment is numerically modeled. The Saint-Venant hydrodynamic equations and also advection-dispersion equation (ADE) are applied for modelling flow and suspended sediment transport. It is necessary to choose appropriate empirical and/or semi-empirical equation to accurately estimate the equilibrium suspended sediment discharge، as well as the appropriate equation describing longitudinal dispersion coefficient. In this research، 5 and 6 equations were applied in the ADE for estimating equilibrium suspended sediment discharge and longitudinal dispersion coefficient، respectively. 30 combinations of these equations were made and the final model was run for each of them separately. Comparison of the predicted suspended sediment concentrations and the corresponding measured values at the survey site، Abdelkhan Station، for the calibration and verification periods showed that the combination of the Van Rijn''s equilibrium suspended sediment equation and the Fischer''s longitudinal dispersion equation performed very well. The maximum percentages of errors in estimation of suspended sediment concentrations were 19. 56% and 26. 3% for the calibration and verification periods، respectively.

Knowing about the way water is distributed in the soil is essential for designing and managing the Subsurface Drip Irrigation systems (SDI). Since carrying out experiments to recognize the form of moisture distribution in the soil is too complicated and time-consuming، using numerical simulations can be an efficient، effective substitute method to design these systems. One of these models is HYDRUS-2D، which is able to simulate the movement of water، heat and solute in saturated and unsaturated conditions in soil. This research aims to figure out the extent to which the HYDRUS-2D model is able to estimate wetting pattern in soil around a dripper. The simulations’ findings were compared to the data gathered from the field، including SDI system in different irrigation times، and 72 hours after irrigation. Moreover، the rates of error were measured for all points and distances from the dripper in all times of irrigation and also beyond that. The results indicated that the model can simulate the changes، trend similar to what happened in the soil profile. However، it estimated the rate of soil moisture with higher errors in those points in which the wetting took place، with the maximum error rate being RMSE= 0. 05 per every 1. 5 hours after irrigation starting point in the depth of 30 centimeters where dripper is placed. Also، with an increase in the irrigation time، and soil moisture evening which resulted from redistribution of moisture، the model resulted in better estimations. 72 hours after finishing the irrigation، the estimates were closer to real figures with an average error estimate of RMSE= 0. 002.

In this study، a completely randomized experiment was designed with four irrigation treatments and three replicates. The irrigation programs were raw wastewater، treated wastewater، a combination of 50% raw wastewater and 50% potable water and a combination of 50% treated wastewater and 50% potable water. The experiments were run within a greenhouse. The lysimeters were built up on September 2009 and they were filled with two layers of soil. The upper (0-30 cm in depth) and lower (30-70 cm in depth) layers were sandy loam and sandy clay loam، respectively. A total of eight watering programs with an interval of elevens-day were applied. After each irrigation program، intake wastewater and drainage water of each Lysimeter was sampled in order to analyse the transport of heavy metals (Cu، Zn، Fe and Mn، Ni، Cd and Pb). Results showed that the effect of water quality was significant on percentage of transport of heavy metals. The lowest transport percentage of heavy metals belonged to raw wastewater treatment. Also، the highest percentage of transport of Cu، Zn، Fe، Ni and Pb belonged to the combination of 50% raw wastewater and 50% potable water. In most cases، we observed that the transport percentage of these elements increased by continuing the irrigation

The effect of sugarcane straw anion exchanger with Micro and Nanostructure scale as the adsorbent for contaminated water treatment was investigated. The effects of operating conditions such as adsorbent loading، initial anion concentration، pH and the presence of competitive ions on the adsorption performances were examined. Equilibrium time and pH and adsorbent dosage were 3h، 6 and 0. 5g respectively. The effect of initial concentration on the adsorption of NO3- ions by sugarcane straw anion exchanger was investigated by varying solution concentrations (5-120 mg L-1) using 0. 5g adsorbent dose. For micro and nanostructures، adsorption capacity was (0. 38-6. 94 mg g-1) and (0. 44-7. 51 mg g-1) respectively. In the column experiment، for micro and nanostructures with (15، 50 and 120 mg L-1) and 0. 98 L hr-1 flow rate، adsorption capacity was (8. 73، 25. 71and 36. 25 mg g-1) and (12، 27 and 48. 15 mg g-1) respectively. The result of this study indicated that sugarcane straw anion exchanger with micro and nanostructure scale could be used for the removal of nitrate ions in the contaminated water treatment. sugarcane straw anion exchanger -nanostructure adsorbent had higher adsorption than micro adsorbent for nitrate removal.

Modification of irrigation scheduling and management improvement of irrigation systems are two essential factors that have significant impact on agricultural water use efficiency. Therefore، a field experiment was conducted to evaluate the effect of tape drip irrigation (T) and furrow irrigation systems (S) under different irrigation regimes on yield and yield components of soybean in growing season of 2006-2007 at Gorgan Agricultural Research Station in north part of Iran. The experiment was laid out in a split plot design in a randomized complete form where each treatment was replicated three times. The main plots were irrigation systems of tape and furrow، and three irrigation regimes 100 (I100)، 75 (I75) and 50 (I50) percent of total irrigation requirement were chosen as secondary plots. Results showed that thousandgrain weight (gr) and plant height (cm) in furrow irrigation were significantly more than the tape drip irrigation method. Also significant differences between different irrigation regimes in terms of plant height، node numbers and yield were observed. So، I100 and I50 had highest and lowest values، respectively. In terms of irrigation system، 63 percent of water consumption was reduced in tape drip irrigation method. Also، the results indicated that higher and lower water use efficiencies were obtained from tape drip irrigation method with I50 treatment (1. 09 kg m-3) and furrow irrigation with I100 treatment (0. 50 kg m3)، respectively.

In this research، the quality of the effluent from the City of Mashhad wastewater treatment plants was evaluated based on Ayers and Westcot irrigation water quality guideline، and the potential impacts of these effluents on soil and plants were assessed. For this purpose، the effluent from each of the three existing wastewater treatment plants was sampled on a regular basis، for a period of one year، and their parameters of importance in regard to the agricultural use such as pH، electrical conductivity (EC)، concentrations of Sodium، Calcium، Magnesium، Chloride، Boron، Nitrate (NO3-N)، bicarbonate and heavy metals were measured. Based on the obtained results، the agricultural use of the effluents from the wastewater treatment plants has severe restriction in regard to the bicarbonate concentrations (8-12. 1 meq/L). Also، in view points of parameters such as EC (1250-1874 µS/cm)، Sodium (5. 8-8. 7 as SAR)، Chloride (3. 2-6. 5 meq/L) and adj RNa (7. 8-11. 7)، the effluents were categorized in the class of waters with low to moderate restrictions. However، the measured values of pH (7. 3-8)، Boron (0. 2-0. 8 mg/L)، Nitrate Nitrogen (0. 5-4. 2 mg/L) and heavy metals did not indicate any restrictions for agricultural use. From the results of this research، it can be concluded that the use of effluent as irrigation water requires careful planning، monitoring and management strategies.

Studies on the soils of western Golestan province show that regardless of increased rain and presence of clay minerals with high cation exchange capacity، potassium extractable with ammonium acetate is low. In order to find the reason for this low amount of available K، clay minerals and micromorphology of the soil porosity were studied. Twenty disturbed and undisturbed samples from each horizon were taken for physicochemical properties، mineralogy and micromorphological studies. Four selected profiles included Gypsic Aquisalids، Typic Endoaquepts، Typic Calcixerolls and Typic Hapludalfs. The results showed that in addition to the clay content and type of clay minerals in soils that can affect soil available K (Kava.)، it seems soil porosity can also affect Kava. mainly through their effects on extension of roots، water and nutrients transmission. Favorable content of clay and dominance of smectites in Mollisols and also higher porosity and dominance of channel porosities caused the presence of higher Kava، in these soils. presence of HIS. poor soil drainage، reduction of Fe3+ in smectite crystal lattice in Inceptisols، and also less amount of porosities caused the presence of higher potassium fixation and reduction of Kava. in these soils.

In order to study land degradation from the soil genesis and micromorphological perspective، ten soil profiles were dug and described on five slope positions in both forest and deforested cultivated land. The soil samples were taken from all horizons for physico-chemical analysis and micromorphological studies. Forest soils had a well developed argillic and calcic horizons and also mollic epipedon. These soils were classified as Alfisols and Mollisols. Carbonate leaching into the depth of soil profile and translocation of clays to lower layers and formation of developed soils are by no means related closely with the dense forest cover and its subsequent landscape stability and favorable leaching conditions. Dominant soil orders in this area were Inceptisols and Mollisols. In cultivated landuse، no argillic horizon was observed except in toeslope position. Absence of argillic horizon or its elimination following deforestation is one of the most important and obvious pedogenetic evidences of land degradation after land use change. Outcropping of high carbonatic layers (calcic horizon)، disappearance of mollic and formation of ochric epipedon، presence of redoximorphic features attributed to runoff in lowland، decrease of solum thickness، and change of soil color were the other pedogenic indicators for land degradation in the study area. Microscopic observations showed that granular and crumb microstructures with high porosity were converted to massive and compact ones with low porosity in the deforested area. Disappearance of clay coatings besides absence of excremental pedofeatures were the other important micromorphological evidences of erosion and land degradation.

Discrete Models of Spatial Variability (DMSV) have limitations for soil identification in traditional soil maps. New approaches، generally called digital soil mapping (DSM)، using continuous methods (CMSV)، try to predict soil classes or soil properties based on easily-available environmental variables. The objective of this study was to map the soil classes of the Borujen area، Chaharmahal-va-Bakhtiari province، using digital elevation model (DEM) and its attributes and Soil-Land Inference Model (SoLIM). To do this، eighteen terrain attributes were derived from the DEM of the area. The primary analysis showed seven attributes are the most important derivatives. These derivatives as well as three dominant soil subgroups and seven soil families of the region (41 profiles from 125 profiles) were used to construct the input data matrix of the model. Then، output fuzzy soil maps of SoLIM were converted to polygonal soil map، using ArcGIS. Results showed that different combinations of DEM attributes have different accuracy rates for soil prediction. The accuracy of the interpolation was twice that of the extrapolation. Although SoLIM had an acceptable accuracy for soil nomination، and identification of soil map units’ types، it did not have enough accuracy for the location of soil classes. It seems that using other data like parent material and geomorphic surface maps will increase the accuracy of the model prediction.

Cadmium is a toxic element in plant nutrition and is considered as a contaminant of food and feed. A greenhouse experiment was carried out to examine the effects of combined application of cadmium and zinc on responses of wheat on a clay loam soil texture. This experiment was designed in a factorial experiment with randomized complete block design (RCBD) and four replicates per treatment. Three levels of cadmium (Cd 0، Cd 50 and Cd 100 mg kg-1) and three levels of zinc (Zn 0، Zn 50 and Zn 100 mg kg-1) were added to the pot in factorial (9 treatments)، and then Chamran seed variety of wheat (triticum aestivum L.) was planted in each pot. The statistical analyses showed that Cd application significantly (P0. 01) decreased grain، straw، and total yield، but Zn application increased these parameters significantly (P0. 01). Application of Cd separately decreased the grain yield by 61. 5 while application of Zn separately increased the grain yield by 36. 9. Cd application increased the Cd concentration and uptake by grain and straw as well as total uptake but by increasing Zn application، Cd uptake was decreased by wheat. Cd concentration was higher in straw than that grain، but Zn showed a different trend. Decreasing Zn applications decreased total uptake of Cd from 42. 9 in Zn0 to 7. 8 mg kg-1 in Zn100 treatment. Although this soil was very calcareous، this characteristic did not control Cd absorbtion.

Hardsetting phenomenon is an indicator of poor soil physical quality. Hardsetting soils are soils with high rate of mechanical strength increase upon drying and are hardened and/or compacted when dry out. It is difficult to till such soils. Hardsetting soils have additional limitations such as poor aeration at wet conditions، low infiltrability and high runoff and erosion. Most of Iran soils have low organic matter content and it is expected that hardsetting phenomenon occurs in some of these soils. This study was conducted to investigate the hardsetting phenomenon on 9 soil series collected from Hamadan province. Three types of mechanical strength consisting tensile strength (ITS)، unconfined compressive strength (UCS)، and penetration resistance (PR) were measured on the repacked soil samples prepared in the lab. The ITS، UCS and PR tests were done on the soil cores which had been prepared at bulk density (BD) equal to 90% of critical BD for root growth (0. 9BDcritical). The effects of intrinsic properties on the hardsetting phenomenon were studied، too. Based on the suggested definition in “International Symposium on Sealing، Crusting and Hardsetting Soils” to International Union of Soil Science، in which a hardsetting soil has air-dry tensile strength ≥ 90 kPa، one soil (medium-textured) out of the studied soils showed the hardsetting phenomenon at 0. 9BDcritical. It might be concluded that medium-textured soils are more susceptible to hardsetting. For all of the studied soils، the ITS increased with the increase in clay content. The increasing impacts of clay and carbonate contents were also observed for the UCS and PR، respectively. Calcium carbonate could act as a cementing agent in between the soil particles and brings about the soil susceptibility to hardsetting. Moreover، the decreasing trend of all soil mechanical strengths was observed with water content increase. Slope (b) of the exponential model (fitted to the soil mechanical strength characteristic curve)، as an index of hardsetting، had positive correlation with the sand content and negative correlation with the silt content. Overall، texture and calcium carbonate content are major and effective properties in terms of hardsetting phenomenon in Hamadan soils.

To establish DRIS norms in sugar beet (Beta Vulgaris L.) and compare them with DOP index، leaf samples were collected from 57 fields and N، P، K، Ca، Mg، Fe، Mn، Zn، Cu and B concentrations were determined. On the bases of crop yield، the fields were divided into two groups with low and high yielding performances. Standard DRIS norms were established for the different nutrient ratios. DRIS indices were calculated to evaluate nutrient balances and order of nutrients requirements. Sufficiency ranges of macro and micro nutrients were derived by DRIS technique. DRIS-derived sufficiency ranges were 3. 0-5. 4، 0. 21-0. 47، 1. 7-3. 7، 0. 55-1. 6، 0. 19-0. 34% for N، P، K، Ca، Mg، and 24-168، 10-19، 42-138، 10-14، 9-20 mg/kg for Fe، Zn، Mn، Cu، B، respectively. DRIS indices showed that among macro and micro nutrients in all low yielding fields، Phosphorus and copper had the most negative index values، respectively. The nutritional balance index (NBI) of DRIS and of DOP (∑DOP) were much more than zero in all low-yielding fields، indicating that there was imbalance between the absorbed nutrients by sugar beet. Comparison of the DRIS method with the DOP showed that both methods provide similar information in the interpretation of the results of leaf analysis.

The Soil Conservation Service Curve Number (SCS-CN) method is widely used for predicting direct runoff from rainfall events. The ratio of initial abstraction (λ=Ia/S) to maximum potential retention (S) was assumed in its original development to be equal to 0. 2 (λ=Ia/S=0. 2) in SCS-CN method. Application of the initial abstraction ratio equal to 0. 2 out of the area where it has been developed may lead to a non logical estimation of runoff. Thus، the study was conducted to determine the initial abstraction ratio (λ=Ia/S) by analyzing measured rainfall-runoff events. The dataset consisted of 58 rainfall-runoff events during 15 years (1987-2001) of rainfall and runoff measurements from Taham-Chay watershed، northwest of Zanjan، Iran. Based on the results، the estimated runoff value on the basis of Ia= 0. 2S was 26. 7 times higher than the measured value، on average. There was a very low relationship between the measured and estimated runoff values (R2=0. 09) and mean model error was 0. 13. The Ia/S values varied from 0. 004 to 0. 008 with an average of 0. 006. When Ia/S value was modified to 0. 08، ratio of the measured to estimate runoff value was 1. 4 and the determination coefficient (R2) of the relationship between the two was 0. 41. When seven rainfall events that had the low rainfall intensity values (lower than 0. 14 mm/h) and two events that had the high rainfall depth (bigger than 10. 47 mm) during the past five days were removed from the data analysis process، ratio of the measured to estimated runoff value decreased to 1. 3 and the determination coefficient (R2) of the relationship between the two enhanced to 0. 90. The mean model error for the modified Ia/S value also decreased to 0. 007. It also improved model efficiency coefficient (EF) to -0. 089 compared with 0. 91 for traditional Ia/S value (0. 2).

Potato is one of the most important tuberous crops. To achieve optimum yield in potato، suitable brand and sufficient and balanced soil nutrients are necessary. In order to study the effects of Zinc، Manganese and Copper on potato yield and leaf and tuber concentrations of Phosphorus and Iron، a factorial pot experiment with 32 treatments was conducted in greenhouse of Soil Science Department، Zanjan University، using a completely randomized design and three replications. The study factors were four levels of Zinc (Zn0:1. 14، Zn1:5، Zn2:10 and Zn3:15 mg/kg soil)، four levels of Manganese (Mn0:1. 4، Mn1:5، Mn3:10 and Mn4:20 mg/kg soil) and two levels of Copper (Cu0:0. 22 and Cu1:2 mg/kg soil) which were applied to the soils of planting pots. The results showed that potato yield increased as the soil concentrations of Zinc، Manganese and copper increased to certain levels Soil application of zinc and manganese fertilizers significantly decreased leaf and tuber concentrations of Phosphorus and Iron. Soil application of copper decreased Iron concentration of leaf but not Phosphorus. The highest potato yield was obtained from the treatment of 15، 10 and 2 mg zinc، manganese and copper per kg of soil، respectively.

The task of modern agriculture is to safeguard the production of high quality food، in a sustainable natural environment under the precondition of pollution not exceeding accepted norms. The sustainability of current land use in agro-ecosystems can be assessed with respect to heavy metal accumulation in soils by balancing the input/ output fluxes. The objectives of this study were to model accumulation rate and the associated uncertainty of Zn in the agro-ecosystems of 3 arid and semi-arid provinces (Fars، Isfahan and Qom). Zinc accumulation rates in the agro-ecosystems were computed using a stochastic mass flux assessment (MFA) model with using Latin Hypercube sampling in combination with Monte-Carlo simulation procedures. Agricultural information including crop types، crop area and yield، kind and number of livestock، application rates of mineral fertilizers، compost and sewage sludge and also metal concentration in plants and soil amendments were used to quantify Zn fluxes and Zn accumulation rates. The results indicated that Zn accumulates considerably in agricultural lands of the studied townships especially in Najafabad (3009 g ha-1yr-1). The major Zn input routes to the agricultural soils (and due to agricultural activities) were manure and mineral fertilizers and the major part of the uncertainty in the Zn accumulation rate resulted from manure source.

Magnetic susceptibility measurement is a simple and quick technique for characterizing soils and sediments and describing soil-forming processes. The interpretation of soil magnetic susceptibility data needs sufficient knowledge about the factors affecting this parameter. To identify the effects of parent material، gypsum and calcium carbonate equivalent، 42 samples were taken from horizons of soils developed on loessial، alluvial، granitic and marly materials in southern Mashhad. Gypsum and carbonates of soil samples were removed by successive washing with distilled water and diluted HCl، respectively. Magnetic susceptibility of bulk samples (lfbulk)، gypsum free samples (lfGf)، gypsum and carbonates free samples (lfGCf) and gypsum، carbonates and sand free samples (lfGCSf) was measured. The results revealed a strong 1:1 correlation between the measured and calculated lfGf and lfGCf. Despite the high amounts of gypsum and carbonates in soils developed on marls، their lfbulk was much more than that of the other soils and reached up to 121. 8×10-8m3 kg-1. In contrast، the lfbulk values of saprolitic granite were less than 10. 4×10-8m3 kg-1. The lfbulk values of loessial and alluvial soils were less than those of marly soils but higher than those of soils developed on saprolitic granite. lfbulk values were negatively correlated with the amount of sand. However، reduction in magnetic susceptibility values of marly soils after removing sand reflects the different nature of this soil. The correlation between lfbulk and amount of silt and clay is positive، but the magnetic susceptibility values are more sensitive to clay percentage، indicating the more important contribution of clay to magnetic susceptibility values. The results of this study highlight the role of parent materials، gypsum and carbonates in the soil magnetic susceptibility values that should be considered.

Increase in soil bulk density and reduces in porosity and infiltration rate are the most common disturbances during timber harvesting and ground-base skidding. The present study was conducted to study soil physical properties e. g.، soil bulk density، moisture، porosity and soil hydrological properties e. g.، soil infiltration from ground-base skidding in twenty years since logging. After initial survey، four abandonment skid trails were selected with similar pedologic، climatic conditions and physiographic and different age in Necka-Zalemrod catchment in east of Mazandaran province. Results indicated that impacts of machinery traffices in high traffic intensity have remained yet 20 years since logging. Means soil bulk density، porosity and void ratio were 42. 4 greater، 24. 6 and 46. 7 percent، respectively، lower than the undisturbed areas. The least infiltration rate was recorded in 1-5 years old skid trail، so the reduction of water was not considerable within 18 minutes after experiment into soil in inner ring in this skid trail. Results in each skid trail firmed that in low traffic intensity soil physical and hydrologic properties was tent to “normal” recover in compare to the undisturbed areas.

Southern Oscillation Index (SOI) and Sea Surface Temperature (SST) patterns affect rainfall in many parts of the world. This study aimed to investigate the relationship between monthly and seasonal rainfall of Iran versus SOI and Pacific and Indian sea surface temperature. Monthly rainfall data، from 50 synoptic stations with at least 30 years of records up to the end of 2007، were used. Monthly and seasonal time series of each station were divided to several groups by four methods (Average SOI، SOI Phases، Indian SST Phases and Pacific SST Phases) using Rainman software and with regard to 0-3 months lead-time. Significant differences among rainfall groups in each method were assessed by the non-parametric Kruskal-Wallis and Kolmogorov-Smirnov tests، and the significant relationship was validated using Linear Error in Probability Space (LEPS) test. The results showed that SOI during summer (July-September) was related to autumn (October-December) and October rainfall in the west and northwest of Iran and the west Caspian Sea coast. The El Niño (negative) phase was associated with an increase in rainfall and the La Niña (positive) phase was associated with a decrease in rainfall in these regions. Average SOI is a useful index for rainfall forecasting in the above-mentioned areas. However، Indian and Pacific SST phases are not suggested for rainfall forecasting in Iran، duo to weak or non-persistence relationships. In conclusion، Iran rainfall is not limited to SOI، Pacific and Indian SST; therefore، Rainman could not be used as an aid to water resources management over a year in Iran. It is suggested that we study the teleconnection between Iran rainfall and other ocean-atmospheric oscillations developing a model similar to Rainman in order to that we investigating the variation in Iran rainfall with aid of other effective ocean-atmospheric indicators

Flooding and fire are important phevent which could impact the forests of north of Iran periodically. These phenomena could have undesirable effects on properties and quality of soil. This study was conducted in order to investigative the effects of flooding and fire on some soil properties in Lakan forest، Guilan province. Soil sampling was carried out on three replicates from three depths 0-3، 3-6 and 6-9 cm in flooding، burned and intact regions. Results of this study indicated that clay، silt، pH، electrical conductivity (EC)، Na and K values (in all of depths)، organic carbon (OC) and N values (in second and third depths) significantly increased and sand content (in all depths) significantly decreased in flooding soils in comparison with intact soils. In burned soils، pH values (in first and second depths)، EC، K and P values (in first depth) significantly increased and clay، OC and N values (in first depth) significantly decreased in comparison with intact soils. Soil water retention capacity showed that the flooding and burned soils had maximum and minimum levels soil moisture that can be related to clay and OC changes. Results of WDPT test showed the water repellency in the first depth in burned soils. Generally، flooding and fire phenomena significantly affected physical and chemical properties.