فهرست مطالب محمود رایینی سرجاز

Applying the raw data of regional climate models in assessing the impact of climate change is not advisable due to possible biases. Therefore, correcting the bias of these data is necessary before using them for climate scenarios of the future. The aim of this study is to evaluate the performance and introduce the best combination of bias correction methods for precipitation and minimum and maximum temperature simulated by three CMIP6 climate models.

Five bias correction methods including linear scaling, variance scaling, local intensity scaling, power transformation and distribution mapping were investigated using root mean square error (RMSE), Nash-Sutcliffe efficiency (NSE), correlation coefficient (r) and Student's t test for the historical period (1990-2014). Afterward, the combination of the best bias correction methods was used to project precipitation and temperature under SSP2-4.5 and SSP5-8.5 scenarios in the future period (2051-2075).

Based on the results, three methods of variance scaling, local intensity scaling and power transformation for correcting the bias of the investigated data had weaker performances compared to the other methods. Two methods of linear scaling and distribution mapping had the lowest RMSE and highest r and NSE. Projecting the future climate using the combination of these two selected methods showed that the average annual precipitation in the Hamedan-Bahar region will decrease by 28 and 37 percent under scenarios of SSP2-4.5 and SSP5-8.5, respectively. Furthermore, the annual average of the maximum and minimum temperature will increase by 0.7, 0.9 under scenarios of SSP2-4.5 and 1.4 and 1.5 °C, under scenarios of SSP5-8.5, respectively. In addition, the highest seasonal decrease in precipitation (19.8 mm) compared to the baseline period will occur in the spring under the SSP5-8.5 scenario. Moreover, the highest seasonal increase of maximum and minimum temperature compared to the baseline period was projected in winter (1.6°C) and spring (1.7°C), respectively, under the SSP5-8.5 scenario.

Two methods of linear scaling and distribution mapping are suitable for reducing the bias of the CMIP6 models in the Hamedan-Bahar plain. Also, considering the projected increase in temperature and decrease in precipitation in this region, this study can provide useful information for policy-makers of water resources and agriculture to decide about the rainwater harvesting, recharging of aquifers, crop selection, cultivating period, crop rotation and management methods to reduce the impact of future climate change.

The study of temperature fluctuations is essential for agricultural planning and environmental studies. With global warming affecting various regions, access to long-term temperature data is becoming increasingly important. Dendroclimatology is a useful tool for long-term climate study, and in this study, the average habitat temperature was reconstructed after developing the chronology of Juniperus polycarpus trees in Keygoran site (Aligodarz, Lorestan). The correlation of annual tree rings with climatic variables of meteorological stations was investigated to reconstruct the average temperature in January-March for the period 1910-2014 for this region. The findings show a positive and significant correlation between the average January-March temperature and the growth of annual tree rings. The results show the occurrence of cold years in the first years of the 1910s to the first half of the 1960s. Warm periods have occurred since the second half of the 1960s, and the temperature trend has generally been increasing in recent years. An examination of the positive and negative pointer years also shows that most of the positive pointer years occurred in the second half of the twentieth century.

Global warming changes precipitation and temperature patterns. In this study, the linear scaling post-processing method was used to correct the biases of seven climate models (GCMs) under the Coupled Model Intercomparison Project Phase 6 (CMIP6). Also, the performance of these models was evaluated for simulating temperature and precipitation in the Hamedan-Bahar plain in the baseline period of 1990 to 2014. Three performance indicators (mean square root error, Nash-Sutcliffe, coefficient of correlation) were used to quantify the models᾽ reproducibility to climatic parameters for the historical period (1990–2014). Based on the results, CMCC-ESM2, MIROC 6, and NorESM2-MM models were selected and their ensemble were used to project temperature and precipitation in near (2026–2050), mid (2051-2075) and far futures (2076-2100) under three socioeconomic shared pathway (SSP) 1–2.6, 2–4.5 and 5–8.5. Based on the obtained results, in all three periods, the average precipitation decrease in summer is higher than the other seasons, and the highest amount of decrease will occur in the mid future period under the SSP5-8.5 scenario (67%). Moreover, the minimum and maximum temperatures increased in all three future periods and under all three scenarios. The highest increase of temperature occurred in January and February. Predicting climate parameters using selected models in this study can be a basis for planning and managing water resources and developing the necessary measures to climate change adaptation in Hamadan-Bahar region.

Due to drought crisis in recent years, the use of alternative cropping methods that saves water without any decrease in yield is increasing. Regulated deficit irrigation is a method of irrigation in which, by supplying part of the maximum crop requirement at specified times, water management is addressed and therefore the root zone is in a dry area most of the time. Using this method will partially stop the growth of the plant and usually decrease yield (Jovanovic et al., 2010). Root Partial Drying (PRD) is a modified form of the deficit, which includes watering one section of the root zone in each irrigation and dry up another side, so the moisture of this section before next irrigation largely come down (Ahmadi et al., 2010). In the root drying method, the roots of the plant simultaneously with soil drying with the production of Abscisic Acid, prevent leaf expansion and reduce stomatal conductance. Simultaneously with this process, the root in the wet part with adequate water uptake puts the plant in proper moisture (Yousri Ibrahim Atta, 2008). Abscisic acid is a plant hormone whose production is increased by root in dry soils and transported by water flow into the stem. (liu et al., 2008). On the other hand, The quality of production is as important in all crops and especially in rice production in Iran. (Salehifar  et al., 2009) In order to evaluate some of the physical and qualitative properties of rice grain and the amount of nitrogen uptake in rice (Hashemi variety) under different irrigation levels and comparing it with continuous waterlogging, an experiment was conducted during two years of cultivation of 2015 and 2016.

 The snow variable plays an important role in hydrological cycles and is an essential component of the climate system. Is one of the basic applications in the field of water resources management, especially in areas where snowfall has a large share of precipitation. Therefore, the main purpose of this study is to investigate the trend of these changes in the watershed of the northern slope of the Alborz Mountain range in Mazandaran province in abnormal climatic conditions in the last decade.

First, MODIS sensor data was received daily from NASA's National Snow and Ice Database (NSIDC) with a 500*500 m embedding capacity. The received images are related to the period 2000-2018. To process the images, pre-processing operations were first performed on them in the ENVI 5.3 software environment. The NDSI index was used to estimate the snow cover. Mann-Kendall test and age line slope estimator method were used to study the trend of snow cover changes. Pearson correlation coefficient was also used to investigate the correlation between snow cover level and climatic parameters.

 Examination of the trend of snow cover level seasonally and annually showed that snow cover in winter has decreased by about -50.41 square kilometers per year. From the elevation standpoint, snow cover is regressing, as its trend is decreasing across all elevation levels, especially at altitudes of 1600 to 2500 meters. The result of this study shows that there is a negative correlation between snow cover and net radiation and a positive correlation with soil moisture at a 95% confidence level. A comparison of the correlation between snow cover status and time and different elevation classes with temperature and precipitation shows that in most cases negative snow cover anomalies are associated with positive temperature and negative rainfall anomaly, which is significant at 95% level. While acknowledging the decline of snow stocks on the northern slope and the increasing increase in freezing temperatures, the management of downstream basin water resources should be reconsidered.

 In general, the results show that the trend of snow cover seasonally and annually has a decreasing trend. It can also be concluded that the trend of snow cover of different altitudes in the northern slopes of Central Alborz has decreased and receded. The greatest effect of temperature increase is observed in spring. This is because the energy required to melt snow is usually provided by short-wave radiation in early spring, and as the intensity of the net radiation current increases due to the increase in short-wave input radiation and the whiteness occurs due to the decrease in height and snow-covered range, the snow melting rate increases. Therefore, with increasing temperature and changing climatic conditions, winter precipitation, which will turn into snow accumulation, has decreased and can affect the runoff caused by these precipitations in spring.

Precipitation estimation and preparing of accurate rainfall maps in regions with no recorded climatic data is critical in hydrology and meteorology studies. This is more important especially in desert areas that do not have dense meteorological stations. The dense network of Aphrodite daily precipitation provides daily rainfall data at 0.25 * 0.25 degrees in Iran. But before using it must be evaluated and corrected.

The aim of this study was to investigate the accuracy of Aphrodite network precipitation data in four desert catchments of Iran from the Central Plateau catchment of Iran in monthly and annual time scales. For this purpose, long-term monthly and annual average data of 9 synoptic and 2 rain gauge weather stations of the Meteorological Organization were used. The climate of the stations varies from extra arid, arid and semi-arid. To validate the data at each time scale, the statistics of correlation coefficient, root mean square error and mean bias error were used. Then the network data were modified by coefficient of means ratio. Then, the accuracy of the modified data was compared with the two usual methods of kriging interpolation and weighted inverse distance.

The MBE showed that Aphrodite network data have a good correlation with station data, but it seems that rainfall network estimation is more than the actual data, which some correction coefficients is used to bias correction of rainfall data. The correction factors vary between 0.60 in low rainfall months to 0.94 in high rainfall months. Evaluation of the modified network in different months showed that in addition of solving network over estimation problem, the error was greatly reduced. as well as in the case of annual rainfall, the root mean square error was reduced from 71.25 to 15.19 mm, that indicating, increase network performance by five times after applying correction coefficients.

  Comparison of modified network with the interpolation methods showed that, the modified network is much more efficient than the two interpolation methods. Therefore, the use of obtained correction coefficients for Aphrodite network modification is recommended to improve the accuracy of the Aphrodite precipitation network.

Vegetation is very important in providing organic matter, regulating the carbon cycle and exchanging energy at the surface. In recent years, climate change and global warming have created frequent events such as floods, high temperatures and droughts that can damage terrestrial ecosystems. Weather fluctuation due to climate change directly affects vegetation growth, on the other hand, vegetation respond to climate change by regulating water, energy exchange, and carbon dioxide concentrations.

In this study, which was conducted to investigate the trend of vegetation changes in the study area during the period 2001-2018, 16-day combined time series data of MODIS-NDVI called MOD13Q1 with a spatial resolution of 250 meters was used. In this study in order to investigate the significance trend of vegetation cover, the non-parametric Mann-Kendall method was taken. Also the relationship between vegetation changes and altitude was investigated.

Of the total area of the study area, 52% of the area had a decreasing trend of vegetation and the rest showed an increasing trend of vegetation, although a significant decrease in vegetation at the level of 5 and 1% occurred in 36% and 32% of the area, respectively. Also, 31 and 26 percent of the study area had a significant increase in vegetation at the level of 5 and 1 percent. In the study of the relationship between Z-Kendall statistic and height, the results showed that with increasing the height of Z-Kendall statistic increases and the correlation coefficient of height with Z-statistic is about 0.62. It seems that significant positive trends in vegetation occur at higher altitudes and significant negative trends in vegetation occur at lower altitudes. 99% and altitudes of 670 and 840 were obtained for the negative trend of 95 and 99%. In other words, at altitudes above 2030 and 1860, the trend of vegetation changes is positive and at altitudes below 670 and 840 meters, the trend of vegetation changes is significantly decreasing.

The results of this study showed a significant trend of greening at altitudes of more than 2030 meters in the region. It seems that with the increase of temperature due to climate change at elevated area, suitable temperature conditions and increasing of growing season length is provided for crop growth at altitudes. This increase in vegetation was further observed in the east and northeast of the study area. Also, the significant decrease in vegetation in low altitude areas less than 670 meters can be due to increased water requirement of low altitude plants and the occurrence of temperature stresses in these areas, which are mostly in the eastern, southern and low altitudes of the study area. However, it seems that the area between these two altitudes have not had a significant trend in vegetation changes.

Climate change is one of the most important issues that have affected various parts of human life in recent decades. Undoubtedly, this phenomenon will change the water resources of each basin. Therefore, estimating and predicting the future of river discharge is of great importance due to its harmful effects on the environment, economy and society. This research is aimed at checking and predicting the discharge of the river Gelevard Dam under different climatic conditions.

To this end, the HadGEM2-EM model was used under three scenarios RCP 2.6, RCP 4.5 and RCP 8.5. Also, the IHACRES model was used to simulate surface flow for the intended periods.

The results of the annual changes in the meteorological parameters under the RCP 2.6 climate change scenario showed that the maximum increase in minimum and maximum temperatures would occur during the period 2061-2080. The greatest change in precipitation will occur during the period 2021-2040. Regarding the results of modeling using IHACRES, it was found that the correlation coefficient of the model in the calibration stage is 0.61 and in the verification stage it is 0.79. The results showed that the average river flow rate decreased by 4, 8.7, 13 and 5 percent, respectively, in the four study periods (2021-2040, 2041-2060, 2061-2080, 2081-2100).

Due to the declining trend of Neka River discharge in the coming decades, the projected targets for the Gelevard Dam for drinking water, agriculture, industry, etc. will face significant shortages.

To evaluate the effects of climate change on irrigated wheat yield, Cv. Mehregan, under drought stress condition, a completely randomized block design (CRBD) experiment was carried out during 2019-2020 cropping season in Varamin, Iran. Five treatments of Control (T1), without stress, drought stress in booting stage (T2), flowering stage (T3), milking stage (T4) and doughing stage (T5) were assigned to three replications. In this study, simulation of the future climate, 2025 and 2055 (2010-2039 and 2069-2040), were performed using the outputs of HadGEM general circulation model under RCP4.5 and RCP8.5 climate scenarios. For this purpose outputs of AgMIP model were employed using long-term climatic data of the base period (1980-2009). Based on these findings, under RCP4.5 and RCP8.5 scenarios, the minimum and maximum temperature parameters might increase for the 2025 and 2055 periods. Also, under RCP4.5 scenario rainfall might increase by 9.4% and 21%, for 2025 and 2055 periods, respectively. However, under RCP8.5 scenario, it might decrease by 1.9% and 2.8%, respectively. Drought stress shortened the phonological stages, the number of days after planting to flowering, ripening and the grain filling periods under climate change conditions. The results also showed that under RCP4.5 scenario in 2025 period the highest decrease in dry matter (4 percent) and seed yield (10.2 percent), due to stress condition, occur during booting and flowering stages, respectively.

With the Green Revolution and crop yield increase per unit area, the use of pesticides and chemical fertilizers, especially nitrogen, has grown significantly. The aim of this study was to evaluate the effects of nitrogen fertilizer levels and irrigation schedule on soil CO2 emission, photochemical characteristics and corn yield. The study a 3×2 factorial was conducted in a randomized completely block design, includes nitrogen fertilizer treatments at three levels 0 (N1), 150 (N2) and 350 (N3) kg of urea fertilizer per hectare, and two Irrigation schedules, immediately (I1) and two days after fertilization (I2). The experiment was conducted during 2016-2017 cropping season at the research farm of Sari Agricultural Sciences and Natural Resources University. According to the results, different levels of nitrogen fertilizer had no significant effect on soil CO2 flux, while irrigating after fertilization significantly affected CO2 emission (P ≤ 0.01). The highest carbon dioxide flux was observed in the tenth stage of sampling in I1 irrigation with 366.42 mgC.m-2.h-1, while the lowest occurred on first sampling stage in I2 irrigation treatment with 45.86 mgC.m-2.h-1. While, the effect of different levels of nitrogen fertilizer showed a significant difference in the yield and photochemical properties of corn (P ≤ 0.01). So that the highest and lowest yields achieved by N3 (36 kg m2) and N1 (13.4 kg m2) nitrogen fertilizer levels, respectively. In conclusion, although irrigation schedule had no effect on yield or photochemical properties of corn, but it assumes by fixation of nitrogen fertilizer immediately on the soil tends to increase soil CO2 fluxes through plant and soil microorganisms activities.

In order to investigate the effect of different methods, levels and salinity of irrigation water ‎on cotton, a two-year experiment was carried out‏ ‏at the Hashemabad Cotton Research Station ‎in Gorgan city.‎‏ ‏The experiment was performed in a randomized complete block design with ‎three replications. So, four salinity levels of irrigation water (1, 4, 8, 12 dS/m) as main factors, ‎four different levels of irrigation water‏ ‏‎(33, 66, 100 and 133% of water requirements) was ‎considered as the first factor and two irrigation methods (complete irrigation and Partial Root ‎Dry irrigation/PRD) were considered as the second factor. The results showed that compared ‎to control, cotton yield decreased by 41%, 22% and 19%, in 12, 8 and 4 dS/m salinity, ‎respectively. The water use efficiency was reduced at rate of 30, 18 and 16 percent. As the ‎salinity of irrigation water increased, the average weight of the boll, fiber index, earliness and ‎the fibers decreased significantly. As the moisture level increased, the yield of cotton, average ‎boll weight, the number of seed in a boll and the number of bolls increased significantly. In ‎additional the water use efficiency of the 133, 100 and 66% treatments compared to 33 ‎percent decreased by 32, 16 and 10 percent,‎‏ ‏respectively. The cotton yield under133, 100 and ‎‎66% treatments decreased by 32%, 16% and 10%, respectively, compared to the 33% of the ‎water requirement. Although PRD reduced crop yields by 15 percent compared to full ‎irrigation treatment, but the water use efficiency increased by 36%.‎‎‎‎‎‎

This study was conducted to determine carbon and soil nitrogen stocks in five plantations with broadleaved stands including oak, alder, maple and poplar species and a cypress conifer stand in Tajan watershed in Mazandaran province (Sari city). In order to study soil physico-chemical properties, soil samples were taken at a depth of 10 cm in each stand. Soil characteristics including texture, soil acidity, bulk density, electrical conductivity, total nitrogen, organic carbon was measured. The results showed that tree species affect the physicochemical properties of the soil. The highest carbon storage was observed in alder (64/61 ton/ha) and the lowest carbon storage in poplar (26/76 ton/ha). Nitrogen stock had the highest (2/68 ton/ha) and the lowest (1/17 ton/ha) in alder stand. Overall, the results showed that carbon and soil nitrogen storage are as an added value with other values ​​and benefits of forest ecosystems and as an indicator for assessing ecosystem sustainability. Based on plantation and reforestation must be done with broadleaf species that have high potential for atmospheric carbon storage.

Global warming is leading to gradual and tremendous climate change following the increase in greenhouse gases. Methane gas can be produced in anaerobic processes in soil, such as paddy fields. Therefore, in the agricultural sector, waterlogged rice cultivation is one of the main sources of this methane gas emissions. On the other hand, straw burning brings a huge amount of pollutants to the atmospher. In this regard, a study with four experimental treatments was conducted: (a) without straw (control), (b) rice straws incorporated into the soil,  (c) burned rice straws left in the field, and finally (d) burned air-dried rice straws left from first cropping harvest. The experiment was carried out on the experimental field of Sari Agricultural Sciences and Natural Resources University. Methane gas sampling was performed at 10- day intervals and carbon dioxide gas sampling was performed one day after straw burning and then in three stages in the second cropping season. Finally, in order to compare the treatments in terms of methane and carbon dioxide emissions, the carbon dioxide equivalent of methane gas was calculated.The findings showed that the highest methane emission was from rice straws incorporated into the soil (6.75 mg/m2.day) and the lowest emissions were from the control treatment (2.97 mg/m2.day) ) and burned rice straws air-dried after harvest (2.62 mg/m2.day). Also, the results of carbon dioxide emissions during the second cropping season showed that the highest amount was from burned rice straws left in the field treatments (133.93 mg/m2.day) and the lowest amount was observed from burned rice straws air-dried after harvest (67.08 mg/m2.day). Finally the results of the total greenhouse gas emissions measured in the whole period showed that wet and dry straws burned treatments could have the potential to increase global warming almost 8 times more than the control treatment.

Global warming could affect snow-covered watersheds and the temporal and spatial distribution of snow, and thus the water needs below the basin. Therefore, the aim of this study is to investigate the spatio-temporal changes of snow cover and snow retention in the northern aspects of Central Alborz. The Normalized Difference Snow Index (NDSI) extracted from MODIS satellite images was employed to estimate snow cover during 2000 - 2018 intervals. The findings of this study showed that there is a significant and increasing trend in the temperatures of May and June. On the other hand, although there was no trend in the snow cover, the Sen's slope estimator showed that the snow cover in January decreased by about 220 km per year, which had a high negative correlation with the increase in the average temperature of this month. (r = - 0.77), while in March, the snow cover increased by nearly 60 kilometers a year. There was a significant positive correlation (r = 0.81) between snow cover and snow depth, and significant negative correlations (r = -0.80 to r = -0.60) were found between the annual snow cover and the average annual air temperature. These findings indicate that the effect of temporal and spatial changes in temperature on the extent and persistence of snow cover is meaningful. By reduction of the basin’s height from the west in Haraz, with an average height of 2059 m, to the east in the Tajan basin, with an average height of 980.7 m, the snow cover area and its durability reduced. From the findings it is concluded that temperature changes in this region follow the global warming trend, while this warming has affected on the variance of the snow cover extend.

Crop Growth Models (CGMs) provide a tool for generalizing the results of water research from small scales to a larger ones. In this situation, using remotely sensed data is vital in order to reduce the inaccuracy derived from spatial variations. The present study was conducted to optimize water use in paddy fields of Guilan province using a combination of DSSAT model and Landsat satellite image. At first, the model was calibrated using the data of the small plot, then the accuracy of the model estimation was evaluated in 110 farmer fields of Some Sara. In the next step, using satellite imagery data, the model was calibrated and evaluated in the same area and the performance of each method was compared. Finally, using the model, the water productivity in the region was obtained in five water use scenarios. The results indicated that with water consumption of 400 mm during the growing season, maximum water productivity was obtained. The average water productivity based on water consumption in the rice growth period is 0.65 kg per cubic meter. In the areas, actual yield is less than potential yield. These areas represent a total of about 80% of the land in the region.

Accumulation of greenhouse gases in the Earth’s atmosphere resulted in global warming and climate change. To mitigate climate change and cope with its consequences several strategies has been proposed. Silviculture and organic matters decomposition management, respectively, propose to sequestrate carbon and mitigate atmospheric greenhouse gases. The aim of this study is to evaluate the influence of tree species on soil greenhouse gas (CO2, CH4, N2O) emissions within forest plantations. For this purpose 20-year old maple, alder, oak, poplar and cypress species plantations were chosen in Sari region, Iran, and soil CO2, CH4, N2O emission rates measured during summer and winter times. Within each plantation area, 3 collecting gas chambers were installed at 10 cm soil depth randomly. The kind of emitted gases and their emission rates measured using gas chromatography. The results indicates that there are highly significant differences (P≤0.01) between tree plantations for CO2, CH4 and N2O gas emissions in the summer time, while during winter significant difference (P≤0.05) observes for CO2 emission. The TOPSIS ranking indicates that oak, maple, cypress, alder and poplar, respectively, are the more favorite sites in declining greenhouse gas emissions. Therefore, it concluded that in future silviculture attempts this issue should be taken into considerations.

Water scarcity is one of the greatest human challenges in this century which can cause many limitations in the world. Demand for freshwater is also increasing due to economic and population growth. Therefore, suitable planning for the limited water resources for storage, allocation, return flow, and environmental services is critical in order to optimize resources. Nowadays, an efficient water accounting system based on measuring, reporting, planning, and monitoring water resources in the world is needed. This system provides the possibility of processing and interpreting information in order to establish a comprehensive and integrated management of water resources through the organization of various data from different hydrological, environmental, and economic sectors. The water accounting system is an approach to standardize the way that data and information is organized. The purpose of this study is to introduce the WA+ water accounting framework as a simple and standard method that describes the state of water and land management in complex watersheds. This method is based on the water balance approach. Its feature is the use of satellite data to access the hydrological base data and surface ground processes. In general, the input data required for this framework can be derived from satellite measurements, hydrological models, and ground data. At present, WA+ contains 8 sheets which summarize water management situation and results are also presented as tables and maps. WA+ has a set of performance indicators that are used in the assessment and analysis of water resources and water consumption situations. WA+ has limitations that need to be resolved in the future and be edited for wider use.

  Environmental stresses, in addition to their straight effects on plants growth and development, induce oxidative stresses on plants. These secondary stresses cause degradations on cell wall lipids and cell organelles proteins. In response to overflow of reactive oxygen species (ROS) enzymatic and non-enzymatic antioxidants productionscould be induced in plants. Due to the kind and intensity of environmental stressesand plant physiological pathways the activity responses of antioxidant enzymes could be different. Therefore, the aim of this research was to evaluate the effect of water stress on soybean antioxidants induction. This trial was done on spring and summer 2012 in Sari Agricultural Sciences and Natural Resources University (SANRU) research station, Sari, Iran. The JK variety of soybean (Glycine max L.), which is widely cultivated in the region was selected for this purpose. A completely randomized design with 4 soil available water (AW) treatments in a pot experiment was employed. After 4-leaf stage soybean seedlings were randomly assigned to 4 water treatments of control, with 100 percent (well-watered, W0), 60 percent (mild stressed, W1), 40 percent (intermediate stressed, W2) and 20 percent (severe water stressed, W3) of soil AW. Plants were re-watered to 100 percent AW upon reaching to the assigned water level. During the R4 and R5 reproductive stages leaf samples were collected to measure leaf catalase and peroxidase enzymes and MDA and leaf total nitrogen and seed weight per plant using spectrophotometer and autoanalyzer. Data were analyzed using SAS software and mean comparisons were done using Tukey post-hoc test. Findings of this research showed that water stress significantly (p ≤ 0.05) affected leaf enzymatic activities of catalase and peroxidase, and influenced malondialdehyde (MDA) and total nitrogen contents and seed weight per plant. The catalase enzyme activity increased up to 60% AW, Then declined by further increase in soil available water. A highly significant quadratic relation (R2 = 0.89; P ≤ 0.01) was found between this enzyme activity and soil available water. The trend of variations in peroxidase activity by reduction in soil AW was highly positive and significant (P ≤ 0.01). The amount of this enzyme in water stressed treatments relative to control increased by 18.7, 29.9 and 34.4 percent, respectively. A highly significant, but negative correlation (r = - 0.86; P≥0.01) was found between MDA values and soil available water. The variation trend of leaf soluble proteins relative to soil available water was decreasing and significant differences were found between control and stressed treatments of W2 and W. The leaf total nitrogen contents increased by reduction in soil available water (r = 0.84; P ≤ 0.01). Also, seed weight per plant as an index of plant performance up to 60% of available water was ascending and in the moisture content of 80% available water, due to the increasing trend of all antioxidants to the highest. It could be concluded from these findings that increase of antioxidant enzymes, due to mild water stress, could diminish destructive effects of reactive oxygen species (ROS) in soybean. Antioxidant activities to a certain level of water stress, in this case up to 60% of AW, had an effective protective effect on photosynthesis process, therefore on soybean seed yield. It seems catalase activity was more effective on severe water stresses compared with peroxidase enzyme.

Optimal use of agricultural inputs, especially water, will result in sustainable agriculture and food security. Therefore, proper management of soil moisture and the use of new methods to maintain and increase soil moisture storage capacity are important. Thus, the aim of this research was investigation the effect of irrigation management with injection superabsorbent gel and organic matter on water use efficiency and quantitative and qualitative yield of orange. The experiment was carried out as split plot in randomized complete blocks design with three replications in Miyandoroud region, Mazandaran province in 2015 and 2016. Three irrigation management including 100, 75 and 50% of plant water requirement were chosen as main plots and two superabsorbent gel injection depth including 30 and 60 cm were chosen as sub plots and four organic matter level (superabsorbent gel, vermi-compost, combined of organic matter and superabsorbent gel and control treatment were chosen as sub sub plots. The results revealed that the most fruit weight and fruit volume were obtained for 100% of water requirement irrigation management with gel injection in 30 cm of soil depth. Moreover, the maximum fruit diameter, fruit volume and fruit weight was achieved for 100% of water requirement irrigation management with combined applied of organic matter and superabsorbent gel. According to findings of treatments interaction, there were observed the negative correlation between TSS percentage and fruit diameter, fruit volume and fruit weight. Based on triple interaction of treatments, with decrease of water usage based on water requirement the young branch length, leaf area, pH, growth density, WUE, tree yield and yield per hectare were statistically significantly decreased that the negative impact of that at gel injection in 60 cm of soil depth and control treatment was more than other treatments. The highest WUE (16.14 kg.m-3) was obtained for 100% of water requirement irrigation management with gel injection in 30 cm of soil depth and combined applied of organic matter and superabsorbent gel. Moreover, the most tree yield was produced with 100% of water requirement irrigation management with gel injection in 30 cm of soil depth and consumption of superabsorbent gel, vermi-compost and combined applied of organic matter and superabsorbent gel. The maximum yield per hectare was achieved by 100% of water requirement irrigation management with gel injection in 30 cm of soil depth and consumption of vermi-compost and combined applied of organic matter and superabsorbent gel (44.03 and 46 ton per hectare, respectively). Therefore, combined applied of organic matter and superabsorbent gel can increase the moisture storage capacity by increasing the WUE and thus improving the quantitative and qualitative yield of orange.

Estimation of evapotranspiration is,one of the main components of the hydrological cycle, and is essential for irrigation scheduling, water balance, irrigation system design and management and crop yields simulation. Unlike conventional methods remote sensing estimates evapotranspiration in different spatial scales. Therefore, the aim of this study is to estimate evapotranspiration using OLI sensor images and SEBAL algorithm in the Dasht-e-Naz area, Sari, Iran. To evaluate the results, evapotranspiration estimated by the reference method, Penman-Monteith-FAO, was compared with SEBAL algorithm. Strong and significant correlation was obtained between these two methods (R2=0.93), Low error of estimation by SEBAL compared with reference method (RMSE=1.14) and low absolute difference between the SEBAL and Penman-Monteith-FAO (MAE=0.96) indicates that there is a good match between estimated values by SEBAL algorithm and Penman-Monteith-FAO standard method. This study showed that OLI sensor images and SEBAL algorithm could satisfactorily estimate actual evapotranspiration in the Dasht-e-Naz area, Sari.

Due to climate change and increasing of water demand for agricultural productions, optimum use of water resources is necessary. In this experiment, the effects of partial root zone drying (PRD) along with shading were investigated on growth and water use efficiency of 2-year old sour orange seedlings in Ramsar, northern town near Caspian Sea, Iran. The pot experiment were assigned to a completely randomized design and were treated during seven months in 2015. Treatments were full irrigation (FI), partial root zone drying (PRD), PRD along with moderate shade (MShPRD) and PRD along with high shade (HShPRD). Irrigations water volumes were determined on the basis of soil moisture deficiency. Water consumption reduction relative to FI treatment for PRD, MShPRD and HShPRD treatments were 29.6, 36.2 and 39.2 percent, respectively. Mean comparion indicated that trunk diameter, dry weight ratio of root/total plant and root variables (dry and fresh weight, volume, length, area and length density) in HShPRD were significantly lower than those of other treatments. Also, total dry matter and volume and weight of stem and branches in HShPRD were lower than those of full irrigation treatment. Dry weight ratios of leaf/total plant, shoot/total plant and shoot/root in this treatment were higher than those of other treatments. Treatments had no significant effect on leaf variables, plant height, branches length, root diameter and specific root area and length. In conclusion, the highest irrigation water use efficiency was observed in MShPRD, but it had significant difference only with full irrigation.

One of the important reasons of soil erosion and sediment production in irrigation and drainage canal networks is the soil instability. Erosion mechanism in this type of channel starts with the impact of raindrops and soil aggregation, so that broken fine particles lead to blockage the pores. In this condition, soil permeability is reduced compared to the initial state and runoff that is increasing. Increased runoff on slopes of moderate to steep, rises shear stress sharply which causes soil destruction and produces sediment production. To overcome this problem, suitable vegetation cover deployment is appropriate, but in some situations, vegetation cover establishment is not possible simply due to special circumstances and it is not the best solution in the short term as well. One of the ways of controlling erosion on slopes is the use of various mechanical structures, commonly used in engineering projects, that is associated with expensive costs. Another solution that was tested in this research, is the use of natural corrective materials such as organic mulch and natural rectifier materials. In this study, by using four types of various organic mulch, soil erosion resistance of various parameters of the drain canal bank was studied using simulated rainfall in the rainfall laboratory of Soil Conservation and Watershed Management Research Institute. In this article, the results of using bio mulch for erosion control, on the drainage channel bank are provided. This study aimed to determine the most appropriate type and density of different mulch on canal bank erosion reduction for irrigation and drainage network channel project that is located in Arayez plain of Khuzestan. With the use of four organic mulch, at least 40 experiments on soil samples were done. For the all laboratory tests, 25 kg soil samples were pressed inside the steel basins, to imply the bulk density of soil in nature. Treatments in the flume with a slope of 1 to 1.25, similar side slope drains, in both 30 and 80 mm per hour rainfall intensity were simulated. Each treatment was applied at three densities. The results showed that all mulch treatments compared with control samples had a significant effect on sediment and it confirmed that the bio mulch are effective in the erosion control of the bank drainage channel. The results showed that the mulch will lead to reduce sediment more than 90 percent. Therefore, the use of mulch 1 and 4 in the highest density, have the greatest impact on the rate of erosion. It was also found that by increasing density of mulch, the amount of sediment reduced significantly.

To design water constructs, such as spillways, canals and many other water structures one needs to estimate probable maximum precipitation (PMP). Since climate variability and spatial variations affect PMP estimation selection of proper statistical method, which provides better estimation is important. Based on general frequency equation, Hirschfield method has been proposed for this purpose, but it overestimation makes it unfavourable. Therefore, the aim of this research is to estimate PMP24 of Kohgiluyeh-e-Boyerahmad region using frequency factor. The PMP trend was calculated using long term meteorological data. Data of 3 out of 31 stations showed trends, which were omitted from further processing The simulated statistics of the 28 selected stations shows that the 3-factor log-normal is the best model to fit the data. The homogeneity factor (H1) is -1.61, which shows a slight non-homogeneity in the region. Therefore, the biggest frequency coefficient could be used to estimate PMP24 in all stations, which were 4.45. Using these criteria the calculated PMP of all stations were used to draw isohyet and reveal special rainfall distribution.

Recent global warming had brought harsh variations on climate variables all over the world. In order to investigate the past climate trend for predicting future climate trend, long term climate data is needed. Tree-ring data are good proxies of past climate which can be used to reconstruct the past climate. The purpose of this investigation is to develop the chronology of tree-ring width and its comparison with climate variables. Tree-ring width was measured by LINTAB table. Then, measured tree-ring width was cross dated by TSAP software. To remove age trend and preparation of final chronology, the ARSTAN software was used. 12 out of 22 tree time series were dropped out, because of insufficient matches with the other samples. The final chronology of the site was determined from 1657 to 2014, close to 358 years. However, EPS was more than 0.85 only for the period of 1910-2014. Correlation between annual tree-rings indices and monthly precipitation was not significant. While monthly mean temperatures of January, February and March had positive and significant correlations with tree-ring widths. It could be concluded that Juniperus growth is not limited by moisture conditions while higher temperatures were in favour of tree-ring growth. It seems that high elevation of habitat provides enough moisture for tree growth but on the other hand occurrence of very low temperature causing failure to provide suitable temperature condition for the start of cambium activities in the first months of growth season. Based on this finding, mean temperature of last century in this region could be reconstructed.

Climate change and ever-increasing water use, along with water scarcity, reduces crop production. Thus, efficient water management, such as deficit irrigation and shading could resolve some of these shortcomings. In deficit irrigation with partial root zone drying (PRD), half of the root zone is irrigated and the other half is left unirrigated. This experiment was conducted with five treatments of (1) full irrigation, which trees received 100 percent of soil field capacity (FC), 2) two PRD treatments, which receiving 50 (PRD50) and 75% (PRD75) of FI and 3) two PRD treatments, such above which treats by shading nets(SHPRD50 and SHPRD75). Tukey's test was used to compare treatment’s means of stomatal conductance (gs), leaf relative water content (rwc), stem water potential (Ψst), and leaf temperature (Tl). Moreover, Regression analysis was done between the above factors and leaf to air vapor pressure difference. The results show that gs and rwc were higher in FI, PRD75 and SHPRD75 relative to stressed treatments of PRD50 and SHPRD50. The same trend was registered for Ψst and the lowest values were achieved by treatments receiving 50% of FI. Leaf temperatures in some measurement intervals were significantly higher in stressed treatments of PRD50 and SHPRD50. Water deficiency significantly reduced yield in stressed treatments of PRD50, while reversly, it increased fruit sloble salids in PRD50 and PRD75. Shading on PRD treatments increased fruit size and yield, Although this improvement was significant only for fruit diameter of SHPRD75 in comparison with PRD50.