Research Article
Irrigation
Nader Karimi; Sayyed-Hassan Tabatabaei; Mohammad Hassan Rahimian; Seyyed Alireza Esmaeilzadeh Hosseini
Abstract
Introduction In arid and semi-arid regions, agricultural sustainability needs to improve the consumption of water and soil resources. Low rainfall, high evaporation, low water quality and less leaching of solutes in the soil due to limited water resources are the main problems in these areas. The ...
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Introduction In arid and semi-arid regions, agricultural sustainability needs to improve the consumption of water and soil resources. Low rainfall, high evaporation, low water quality and less leaching of solutes in the soil due to limited water resources are the main problems in these areas. The quality of water and soil resources in the provinces of Fars, Khuzestan, Yazd, Golestan and Khorasan also shows that most of the wheat farming lands in these provinces are always facing salinity issues. According to the conducted studies, saline water can be successfully used in irrigation, but application of unconventional water by surface irrigation systems with low efficiency due to evaporation and high water salts leads to soil salinity. Micro-irrigation methods increase water use efficiency by reducing water consumption and increasing yield, so that drip irrigation efficiency of 91-80% and irrigation levels of 50-73% have been reported. In recent years, the use of drip irrigation system (such as tape on wheat fields) has been recommended to farmers as a water management solution. Micro-irrigation systems by reducing water consumption and increasing yields, improve water use efficiency. Drip tape irrigation system compared to other surface and sprinkler irrigation methods, due to short irrigation periods and reduction of evaporation losses and deep infiltration even for crops can be proposed as an alternative. Drip tape irrigation in wheat cultivation can increase water use efficiency up to 2 times. Also, in irrigation with salt water, while maintaining humidity in the environment, it reduces salinity stress and by consuming less water and reducing the amount of wetting, it introduces less solutes into the soil. This method has limitations in wheat fields due to costs and also the possibility of soil salinity problems, some of which can be overcome by increasing the distance between the laterals and reducing the consumption of drip irrigation (Tape) per unit area.Materials and Methods In this study, during the 2020-2021 at the Salinity Research Center of Yazd Province (Iran), the effect of lateral distances on the surface and depth distribution of soil salinity was investigated. For this purpose, two irrigation water salinity treatments, including 3 and 8 dS / m and two flood (T1) and drip irrigation systems (Tape) with lateral distances of 60 (T2), 100 (T3) and 140 (T4) cm were considered. Irrigation management treatments included the use of the flooding method (as the dominant method in wheat fields) and the use of the Tape drip irrigation method (as the proposed method with very low water consumption). A distance of 60 cm was considered as the optimal distance with complete water overlap, a distance of 100 cm was considered as an economic distance with the possibility of deep moisture distribution and a distance of 140 cm was considered as a large lateral distance. To investigate the salinity distribution and the accumulation of salts in the soil, regular soil sampling of different treatments was the end of the season.Results and Discussion In all irrigation treatments (saline and non-saline), despite the constant volume of water consumption per unit area of all treatments, in T3 and T4 treatments, irrigation depth increased compared to T2 treatment and reduced soil salinity in the wetting area (irrigated area). By increasing the horizontal distance of each point of the field from the lateral, the irrigation depth and leaching fraction decrease and consequently, the soil salinity of these points can also increase. Under non-saline irrigation conditions (salinity of 3 dS/m), soil salinity at intervals of zero (below the lateral), 15 and 30 cm, between 5.5 and 6.1 dS/m has been observed. Values below the threshold of tolerance to salinity of wheat plant and, in this regard, does not pose a risk to the plant. At a distance of 45, 60 and 70 cm from the water pipe, the salinity of the soil is higher than the threshold and if there is a plant in this area of the field, it will face serious damage.Conclusion The results showed that although the Tape method in saline conditions (8 dS/m) compared to non-saline conditions (3 dS/m) leads to higher accumulation of solutes in the soil and increases the possibility of plant damage, but according to the final results of this study, by increasing the distances of irrigation laterals and proportionally increasing the depth of irrigation and keeping the salts away from the planting bed, a more suitable environment for plant growth can be prepared and higher economic benefits of this measure can be obtained. Also, in terms of controlling soil salinity, the conditions have been such that treatment with lateral distance of 140 cm compared to treatments of 60 and 100 cm has led to lower amounts of soil salinity in the subsurface and has provided better conditions for the plant. Thus, by increasing the distances of laterals from 60 to 140 cm and, consequently, increasing the depth of irrigation, it was possible to transfer solutes to lower depths of the soil.
Research Article
Irrigation
Ramin Fazloula; Hedyeh Pouryazdankhah
Abstract
IntroductionMazandaran province is one of the most important rice and citrus-producing areas in Iran, where most of the citrus orchards and agricultural fields are irrigated with groundwater. On the other hand, irrigation water pH is one of the basic qualitative factors that determine the solubility ...
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IntroductionMazandaran province is one of the most important rice and citrus-producing areas in Iran, where most of the citrus orchards and agricultural fields are irrigated with groundwater. On the other hand, irrigation water pH is one of the basic qualitative factors that determine the solubility and biological availability of chemical components in the soil such as nutrients and heavy metals, and it can affect agricultural production.Materials and MethodsThe coastal strip of Mazandaran Province toward the southwest of the Caspian Sea is situated in the north of Iran with an area of 8,252 km2 between 35.77 to 36.99 N latitudes and 50.36 to 57.13 E longitudes. In this study, the temporal and spatial variations of groundwater salinity were studied in the coastal strip using data from 300 wells, collected by Mazandaran Regional Water Company. Data included mean pH for each 6-month period of 9 consecutive years, from 2012 until the end of 2020. pH maps and maps of the risk probability area for rice and citrus growth were obtained by using Ordinary Kriging (OK) and Indicator Kriging (IK) in ArcGIS 10.7.1 software, respectively. Classifications were selected according to the properties pH range for the growth of citrus (5.8, 8) and the optimum pH for rice (6.8) in OK method. The indicator amount of pH was considered equal to 6.8 in IK method. Thereby, areas belonging to different pH classes were outlined and places with the risk probability for growing the rice and citrus were identified.Results and DiscussionThe 11 different models for semivariograms were drawn, and the best one was chosen according to the lowest nugget-to-sill ratio, and thus Stable and Exponential were obtained as the highest frequency for first and second half-years. The indices of cross validation for each selected semivariogram were estimated within acceptable ranges. In Ik method, the pH of studying area was classified into 4 ranges of <5.8, 5.8–6.8, 6.8–8.0, >8, and the percentage area of each classification derived from the ArcGIS software, the average area of each classification during the studying period was calculated zero, 0.6, 83.5 and 15.9 percent, respectively. It showed that most part of the study area located in the range of 6.8-8. It means most rice fields and citrus orchards were irrigated by the groundwater with the pH close to neutral. The obtained maps in the OK method indicated that the pH of the groundwater was not acidic in any points and alkaline conditions were observed in the western and eastern parts of the province. Therefore, The IK method was used to further investigate and determine the vulnerable areas. The probability of pH risk in rice and citrus growth was classified into 4 ranges (0-20%, 20-40%, 40-60% and 60-100%), and the average percentage area of each classification along the period was estimated 94.9, 4.8, 0.3 and zero percent, respectively. Using the IK method, higher probability of groundwater pH reducing the yield in citrus orchards and rice fields was found in eastern parts of Mazandaran province, which was about 5% of total studying area. Also, the results of the study in these 9 consecutive years did not show any decreasing or increasing trend in pH changes and consequently the area under each classification.ConclusionGenerally, the results indicated that the pH of groundwater for irrigating the citrus orchards and rice fields was appropriate in the most parts of the province and merely in the eastern part of the province, low water alkalinity may make a risk probability for rice and citrus growth in both western and eastern parts of the province. Due to the fact that alkaline water causes soil alkalinity and consequently reduces the solubility of phosphorus and some other plant nutrients in soil, it is suggested to supply the optimum required fertilization amounts of the nutrients in soil. However, the amount of fertilization should be on the basis of field research results. It is also proposed to study the condition of rice and citrus growth and the irrigated water in more details through the farms of western parts of the province. Due to the fact that most citrus orchards in this province are irrigated under the pressurized irrigation systems and using groundwater for irrigation, it is suggested that the Langelier Saturation Index (LSI) be examined in future research.
Research Article
Irrigation
Seyed Hamidreza Sadeghi; Mohammad Tavoosi; Somayeh Zare; Vahid Beiranvandi; Hengameh Shekohideh; Fatemeh Akbari Emamzadeh; Marjan Bahlekeh; Faezeh Khorshid Sokhangoy; Reza Chamani
Abstract
IntroductionCurrently, many disasters threaten the health of ecosystems. The pressures caused by extensive human interventions and the unprincipled exploitation of natural resources have led to the degradation of natural resources and the structure and functioning of ecosystems. Hence, evaluating the ...
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IntroductionCurrently, many disasters threaten the health of ecosystems. The pressures caused by extensive human interventions and the unprincipled exploitation of natural resources have led to the degradation of natural resources and the structure and functioning of ecosystems. Hence, evaluating the consequences of human intervention in nature and meeting the growing need of humans to receive diverse services has made it necessary to evaluate the performance of watershed ecosystems in providing different services. Healthy watersheds play an important role in providing a wide variety of ecosystem services. Therefore, watershed health monitoring and evaluation is vital for the conservation of ecosystems and achieving the optimal level of services. In such a way a suitable collaborative and executive approach is established between research and watershed management. In this connection, watershed health analysis can provide valuable help in achieving the goals of integrated management of watersheds and, of course, the balance between the needs of human societies and ecosystems. However, the assessment of the health and sustainability of the watershed affected by human activities has not been sufficiently documented yet.Materials and MethodsThe current pilot research has evaluated the health of the Shiraz Darwazeh Quran Watershed in Fars Province, Iran, and the effect of existing watershed management structures in the region on the health of the watershed with a focus on floods. For this purpose, 36 key criteria from a set of climatic, anthropogenic, and hydrologic factors were identified based on the conditions of the region and the analysis of the flood occurrence process in the watershed. The selected criteria were then categorized into the three indices of pressure (P), state (S), and response (R). After screening the selected criteria in exploring the conceptual approach of pressure, state, and response (PSR), the health status was evaluated in two cases with and without watershed management structures.Results and DiscussionThe results showed that the health condition without considering the watershed management structures was at average conditions with health index of 0.55. In addition, the results of the watershed health assessment verified the non-significant effects of stone and mortar structures on improving watershed health. So that, the health conditions was remained at average status with health index of 0.53. Therefore, it can be acknowledged that the existing watershed management structures, due to the limited both number and spatial coverage, have not been able to noticeably affect the improvement of the general conditions of the watershed, despite the effect on the factors affecting the health of the sub-watersheds where the structures have been constructed. The spatial changes of the calculated variables showed that the abandoned lands, time of concentration, area under military activities, surface of sensitive formations to erosion, high density of the drainage network, density of the roads, areas of regions with high potential in producing runoff and sediment, and size of the residential areas were the most important factors affecting the health situation of the Darwazeh Quran Watershed.ConclusionAccording to the results of the analysis of the indicators and criteria considered in evaluation of the health of the Shiraz Darwazeh Quran Watershed based on the PSR approach, it was found that the watershed had an average health status. Therefore, it can be acknowledged that the existing watershed management structures have not been able to impose a noticeable effect on the prosperity and improvement of watershed health conditions. In general, it can be said that abandoned lands, short concentration time, military activities, the presence of formations sensitive to erosion, high density of drainage network and road, and the potential of high runoff and sediment production, and the size of residential areas are among the most important factors affecting the declining the health of Darwazeh Quran Watershed. Therefore, it is necessary to pay further attention to the aforesaid factors by conducting periodical monitoring with more comprehensive data, in time and also analyzing the trend of relative changes of the indicators in order to explain the adaptive and intelligent management of the watershed. The necessary measures should also be taken into account simultaneously. Therefore, it is suggested to turn the weak points of the region into strong points by applying bioengineering measures and use the opportunities in the region such as the potential of tourism and ecological features in order to improve the health status of the watershed.
Research Article
Soil science
Niloofar Koosha; Kyumars Mohammadi Samani; Vahid Hosseini
Abstract
IntroductionA large part of forest and woodland ecosystems in Iran have been located in arid and semi-arid areas which low level of soil organic carbon (SOC) is considered as one of the main problems. Millions of trees together that make forest ecosystems, play a major role in carbon sequestration and ...
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IntroductionA large part of forest and woodland ecosystems in Iran have been located in arid and semi-arid areas which low level of soil organic carbon (SOC) is considered as one of the main problems. Millions of trees together that make forest ecosystems, play a major role in carbon sequestration and can sequester it in the form of biomass, above ground in plants and also underground in plants root or in the soil. Forest ecosystems play a significant role in absorbing and reducing greenhouse gases and therefore, can play a crucial role in decreasing global warming. Soil is one of the great sources of carbon storage, which plays a significant role in the atmospheric carbon deposition and dioxide gas. The carbon stored in the soil changes under some important driving factors such as: land use change, animal grazing, pollarding, exploitation (included forest harvesting), topography and forest trees, and types. One of the main sources of income for forest stakeholders in Zagros area is the Zagros oak forest. These people livelihoods are heavily dependent on natural resources, especially forest, known as a kind of traditional land use system called “Galazani”. Each family, in this system, has its own common ownership and manages their proprietorships called “Gallajar” which is a part of the woodlands and use some kind of traditional silvopastoral techniques to use these areas. Dominant livestock in the most part of theses area are goats and sheep. In the growing season, they usually feed on ground vegetation and in the winter time, they use dried oak leaves (leaf hay) that is stored before on some special trees call “Daar-Galla”. In the northern part of Zagros oak forest (Kurdistan province), there are some very special stands that are found around every village called sacred groves and are totally intact because of some spiritual values and taboos. There are no exploitation and grazing and even land use changing in these areas, and they show the real undisturbed forest lands in Zagros. The aim of this research was to study and compare soil carbon stock and some essential soil properties in sacred groves and pollarded forests (Gallajar) of northern Zagros forests in order to obtain more precise data in soil after high exploitation and pollarding.Materials and MethodsThe average annual rainfall in 25 recent years in the study is 690 mm and the average annual temperature is 14.2 degrees Celsius. The dominant trees species in the region are Lebanon oak, Aleppo oak and Persian oak. To conduct this investigation, three study areas included both sacred groves and Gallajars, in three main slope aspects including north, east and south facing aspects, were chosen. Then six plots (10 a) were randomly selected in each area and tree canopy (%) and litter percentage were determined in the field. Soil samples took in two depths (0-15 and 15-30 cm) in the center of each plots and then bulk density (BD) and some chemical soil properties included soil organic carbon, soil carbon stock, total nitrogen (N), phosphorus (P), potassium (K), electrical conductivity (EC) and pH were measured in the soil laboratory. A factorial randomized complete block design was used to analysis soil data.Results and DiscussionThe results showed that there were significant differences between soil depths for studied soil properties except BD, N and K and also there were significant differences in various slope aspects in studied parameters. However, no such a trend was observed in soil N and EC. The results also revealed that pollarding had significant effects on all studied soil properties. In addition, all studied soil properties including SOC stock, N, P, K and EC in sacred groves was higher than Gallajars while pH and BD were increased in pollarded areas. The amount of SOC stock, N, P and EC were greater at depth 0-15 compared to depth of 0-15 cm while, pH showed lower amount in the surface soil layer and K and BD had no significant differences in the two studied soil layers. SOC stock in northern, eastern and southern slope aspect were 72.6, 48.2 and 45 tons/ha, respectively. Pollarding and livestock grazing in Gallajars caused a significant decrease in tree canopy and, as a result, the litters on the grounds also reduced. Therefore, it seems that the reduction of trees and canopy cover affected soil properties significantly and reduced SOC stock meaningfully in the long term. Other essential chemical soil properties were also lower in Galajars compared to sacred groves.ConclusionFinally, we can claim that, some factors including pollarding and grazing can significantly reduce SOC stock and other studied soil properties in this research. On the one hand, people are using these forest areas as grazing pastures and also for pollarding trees to fed their livestock and the government could not have convinced them not to pollard the trees and, on the other hand, the results in this study showed that these pollarding operations are affecting forest stands and forest soil chemical properties and SOC stock significantly and reduce their quality considerably. It can be suggested that some new management treatments should be done in these forest areas through the training of local people, preparing sufficient fodder resources and providing enough facilities by the government to reduce pollarding by stakeholders. As a result, the natural process of production and decomposition of organic matter may be controlled in a better way, so that, the soil quality and carbon storage in these forests to be improved in the long term.
Research Article
Soil science
Sahar Mehrnoosh; Ali Beheshti Ale Agha; Fatemeh Rakhsh; Morteza Pourreza; Ali Akbar Safari Sinegani
Abstract
IntroductionThe maintenance of planted forests in arid and semi-arid lands is important. Soil formation in forest ecosystems is different with different tree species. Tree species have a direct and indirect effect on soil organisms. Forest ecosystems change their species composition and abundance of ...
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IntroductionThe maintenance of planted forests in arid and semi-arid lands is important. Soil formation in forest ecosystems is different with different tree species. Tree species have a direct and indirect effect on soil organisms. Forest ecosystems change their species composition and abundance of microorganisms, and consequently their biogeochemical cycles. The accumulation of vegetation biomass and the improvement of soil fertility can play a significant role in soil restoration.Materials and MethodsIn order to investigate the biological characteristics of the soil from 5 treatments, including agricultural (dry farming and relatively poor lands that are usually cultivated barley and wheat and have low productivity), pasture (pastures with minimal vegetation and high slopes that are affected by overgrazing have been changed to barren lands), forest with Acacia type (under and outside the crown), forest with the Cupressus arizonica type (under and outside the crown) and forest with the Pinus brutia type (under and outside the crown) randomly. Sampling was done in 3 repetitions from the 0 to 5 cm layer. The statistical sampling design of this research was completely random, in which, according to the type of afforested species, two types of coniferous forest stands (including Cupressus arizonica and Pinus brutia) and one broadleaf stand (Acacia species) were selected. Also, the area under the crown trees and outside the crown trees was also investigated. Soil samples were sampled with sterile equipment and crushed through a 4-mm sieve. Fresh and moist soil was kept at 4 °C temperature for soil biological tests. Microbial biomass carbon, soil basal respiration (197 days), substrate-induced respiration, and metabolic quotient were measured. Streptomycin sulfate was used to measure fungal respiration and cycloheximide was used to measure bacterial respiration. The activities of urease, acid, and alkaline phosphatase enzymes were determined. After measuring the biological properties of the soil, the normality of the data was checked by the Anderson–Darling test, and the homogeneity of the variance of the treatments was checked by using Levene's test. Analysis of data variance was done using One-Way ANOVA and average data comparison was done using Duncan's test at 5 and 1% probability levels (SAS 9.4 and SPSS 26).Results and DiscussionThe results of soil biological characteristics analysis showed that the highest values of soil respiration and amount of consumed organic matter, substrate-induced respiration, microbial biomass carbon, enzyme activities, and fungal respiration were measured in conifers. Although the amount of these features was also significant in broadleaf trees, they had significant differences. In this study, the high soil respiration rate in coniferous covers compared to broadleaf can be due to the high organic carbon content of the soil in this cover. According to the results of substrate-induced respiration in different coatings, likely the activity of microorganisms involved in the decomposition of organic matter in the studied habitats had a significant difference; Therefore, different coatings can affect the population of soil microorganisms as the main source of decomposition and emission of carbon dioxide by changing the quantity and quality of organic matter and other factors. Also, the highest values of metabolic quotient and bacterial respiration were observed in agricultural and pasture covers. A higher metabolic quotient in these covers indicates a decrease in the efficiency of the use of leaf litter by the soil microbial community. In general, the metabolic quotient in the bacterial community is higher than the fungal community; Therefore, it seems that the predominance of the bacterial population in agricultural and pasture cover has caused this index to increase, although plowing and cultivation, and disturbance of these covers have caused stress to this bacterial community and as a result increased the metabolic quotient deficit in these covers.ConclusionThe results of this research showed that the type of planted tree species causes significant changes in the biological characteristics of the soil. The current research shows that the forest, whether coniferous or broadleaf, had the highest values of enzyme activities, basal respiration, substrate-induced respiration, microbial biomass carbon, and the lowest values of metabolic quotient compared to agricultural and pasture covers. Afforestation increases biological activity and possibly the number and diversity of microorganisms, and improves soil characteristics in the long term. In agriculture and pasture land, due to the destruction of soil and aggregates by agricultural activities such as plowing or excessive livestock grazing, the amount of organic carbon and the activity of microorganisms decreases, and with the decrease of other soil characteristics, the quality of the soil decreases over time. From this research, it can be concluded that the planting of forest species in the soils of degraded areas in the long term can increase soil organic carbon due to high-quality leaf litter, and as a result, increase permeability and soil moisture. Increasing soil organic carbon increases the activity of microorganisms, and in the long term, it will improve various soil characteristics. Planting forest plants in the natural areas of the country, which were destroyed due to the change of use to agriculture and indiscriminate cultivation and finally abandoned, can improve the characteristics of the soil and, as a result, establish the native vegetation of the region, and increase the permeability of water in the soil, the risk of soil erosion, floods, etc. reduce.
Research Article
Soil science
Saba Bagherifam; Mohammad Amir Delavar; Payman Keshavarz; Parviz Karami
Abstract
Introduction
Soil is one of the main drivers of global warming through losing carbon in the form of CO2. On the other hand, its ability to sequester carbon is a suitable option for reducing CO2 emissions. Therefore, even few changes in carbon sequestration or decomposition of soil organic carbon ...
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Introduction
Soil is one of the main drivers of global warming through losing carbon in the form of CO2. On the other hand, its ability to sequester carbon is a suitable option for reducing CO2 emissions. Therefore, even few changes in carbon sequestration or decomposition of soil organic carbon affect the global atmospheric CO2 content. Although the soils of arid and semi-arid regions have low organic carbon content, they can sequester substantial amounts of carbon due to the large area of these regions. So, the Rothamsted carbon model was used to predict the impact of future climate changes on the amount of CO2 emissions and low soil organic carbon stocks in the semi-arid arable lands of Razavi Khorasan province. This model is one of the most widely used models for the study of soil organic carbon turnover and has been evaluated in a variety of ecosystems including grasslands, forests and croplands and in various climate regions. The RothC model is consists of five conceptual soil carbon pools, four active fractions and a small amount of inert organic matter (IOM) that is resistant to decay. The active pools splits into: Decomposable Plant Material (DPM), Resistant Plant Material (RPM), Microbial Biomass (BIO) and Humified Organic Matter (HUM). This model is able to reveal the effect of soil texture, temperature, rainfall, evaporation, vegetation and crop management on the soil organic carbon turnover process.
Materials and Methods
The Rothamsted carbon model was calibrated and validated using data measured in 2020 and available data from the long-term field experiments in the semi-arid agricultural lands of Jolge Rokh. Then, by analyzing the climate change of the study area, the impact of climate change until the end of the current century on the amount of CO2 cumulative emissions, total organic carbon (TOC) and active carbon pools model were modeled and compared in the current climate and also climate change conditions.
Results and Discussion
The comparison between the measured and simulated soil organic carbon values by the model shows the potential of the model to provide predictions with acceptable accuracy. The outcome of comparisons revealed that R2, Root Mean Square Error (RMSE), Mean Difference (MD), Mean Absolute Error (MAE) and Model efficiency were 0.97, 2.78, 2.11, 2.33 and 0.70 respectively. Assessment of climate changes in the region (during 1981-2020) showed a decrease in precipitation and a significant increase in temperature over the past 40 years. Climate change simulation was carried out by temperature increasing and decreasing the precipitation until the end of the current century, indicated the decrease of all active carbon pools. It was found that DPM, RPM, BIO, HUM and TOC decreased respectively to 2.41, 2.72, 2.51, 1.04 and 1.32% compared to the current climatic conditions, while the cumulative CO2 emission increased by 1.26%. Temperature rising leads to increase the rate modifying factor (a) by 2.20%, which enhances microbial respiration and decomposition rate of organic carbon and CO2 emissions (carbon output). However, it also increases the ecosystem's net primary productivity (carbon input). Decreases in rainfall and increase in potential evapotranspiration cause a reduction of the rate modifying factor (b) to 0.23%, which on one side reduces the activity of microorganisms and carbon biodegradation; but on the other side, it decreases the vegetation cover and following that reduces CO2 trapping during the photosynthesis process and transfers it to the soil. It seems that in arid and semi-arid climates where the lack of moisture is the most important limiting factor of the plants growth; the role of precipitation in carbon decomposition and sequestration is greater than temperature.
Conclusion
The Rothamsted carbon model is suitable for regional simulations because it requires only easily obtainable inputs. Therefore RothC is an appropriate tool for estimating long-term effects of climate change and agricultural management (such as application of manures, returning plant residues to the soil, crop rotations, conservation tillage etc.). The RothC model validation in the cold semi-arid agricultural lands of the region, shows the ability of model to properly simulate the pattern of organic carbon changes. Also, simulation of soil organic carbon changes under the climate changes conditions indicates an increase in cumulative CO2 emissions and decrease in soil organic carbon pools of the study area. The methodology can be applied to other regional estimations, provided that the relevant data are available. The predictions allowed to identify the land management potential to carbon sequestration. Such information demonstrate a beneficial tool for evaluation of past land management effects on soil organic carbon trends and also estimation of future climate change effects on soil organic carbon stocks and CO2 emissions.
Research Article
Agricultural Meteorology
Sepideh Dowlatabadi; Mahdi Amirabadizadeh; Mahdi Zarei
Abstract
Introduction
The sustainable availability of water resources and the qualitative and quantitative status of these resources are threatened by many natural and antropogenic factors, among which climate change plays an important role. Climate change can have profound effects on the hydrological cycle ...
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Introduction
The sustainable availability of water resources and the qualitative and quantitative status of these resources are threatened by many natural and antropogenic factors, among which climate change plays an important role. Climate change can have profound effects on the hydrological cycle through changes in the amount and intensity of precipitation, evapotranspiration, soil moisture, and increasing temperature. On the other hand, the distribution of rainfall in different parts of the world will be uneven. So that some parts of the world may face a significant decrease in the amount and intensity of precipitation, as well as major changes in the timing of wet and dry seasons. Therefore, sufficient knowledge about the effects of climate change on hydrological processes and water resources will be of particular importance. In this research, as the first comprehensive study, the effect of future climate change on the water resources components of Neyshabur-Rookh watershed was investigated by a set of one hydrological model and six General Circulation Models under the RCP4.5 scenario.
Materials and Methods
The Neyshabur-Rookh watershed with an area of 9449 square kilometers is a sub-basin of Kavir-e Markazi-e Iran and a part of the Kalshoor Neyshabur watershed, which is located between of 58 degrees and 13 minutes and 59 degrees and 30 minutes and east longitude and 35 degrees and 40 minutes and 36 degrees and 39 minutes north latitude. The study area with an average altitude of 1549.6 m above sea level and average annual precipitation of 246.83 mm, a mean annual temperature of 13.3 Celsius has an arid to semi-arid climate. For hydrological simulation of the watershed using WetSpass-M model, maps of Digital Elevation Model (DEM), land-use, soil texture, slope, and distribution map of groundwater depth, Leaf Area Index (LAI), and climate data (rainfall, mean temperature, potential evapotranspiration, wind speed and the number of rainy days) per month in 1991-2017 period were used. Then the prepared model was calibrated and validated. The climatic data of six General Circulation Models (GCMs) under the RCP4.5 scenario (Representative Concentration Pathways) were downscaled using the Quantile Mapping Bias-Corrected method. The downscaled GCM models were ranked and weighted in each station according to results of the Leave one out cross validation method and utilized as an ensemble for projecting the near-future climatic conditions of the water resources components of the watershed. By importing the monthly maps of precipitation, average temperature and evapotranspiration in the period of 2026-2052 into the calibrated hydrological model, the hydrological response of watershed to near future climate change was determined and evaluated.
Results and Discussion
WetSpass-M was calibrated by changing the calibration parameters in five hydrometric stations and the compared measured and simulated streamflow. The values of four evaluation criteria NS, R2, MB, and RMSE indicated the good performance of the model during the calibration and validation process. By predicting climatic parameters in near future and preparing and importing maps of monthly precipitation, mean temperature, and evapotranspiration to WetSpass-M, the hydrologic simulation of the watershed was done in the 2026-2052 period. The results indicated that the mean annual temperature and precipitation would be respectively increased by 4.66% and 1.21°C under RCP4.5 in the near-future period compared to the baseline period. The average temperature will increase in all months so that the most changes will occur in September and the least changes will occur in March. The rainfall of the watershed will increase in March, April, May, October, and December and will decrease in the rest of the months. The highest and lowest rainfall changes will happen in April and August, respectively. The analysis of the components of water resources in the near future shows that annual total runoff, groundwater recharge, and actual evapotranspiration will increase by 5.9%, 14.85%, and 1.42% compared to the base period, and annual direct runoff and interception will decrease by 15.15% and 3.54%, respectively.
Conclusion
Considering the importance and major role of the Neyshabur watershed in the economy of agricultural products of Razavi Khorasan province, the results of this research will be of great help to the managers and policymakers of the country's water resources management in order to make appropriate decisions with the aim of reducing the effects of climate change on the water resources of the Neyshabur-Rookh Basin.
