نشریه پژوهش های حفاظت آب و خاک
سال بیست و نهم شماره 1 (خرداد و تیر 1401)

Soil erosion is a kind of land degradation that is one of the world's environmental issues. One of the most common causes of land degradation is soil erosion. Various additives and amendments are being employed in order to safeguard the country's water and land. As a result, understanding diverse soil additives and their roles in the conservation of soil and water resources, as well as complete watershed management, is critical. As a result, the purpose of this study was to provide comprehensive information on the background and recent studies on the use of organic, inorganic, and biological soil additives, as well as to evaluate various effects and determine their performance and application in erosion control and soil and water conservation.

All studies and research on the application of amendments in soil and water conservation in different conditions on various components of soil erosion and conservation in Iran were documented in databases and extracted from journal articles, conferences, executive reports, and related research, and theses and dissertations were investigated. The relevant 75 documents were then chronologically evaluated, analyzed, and summarized in order to assess the usage of various amendments in many areas, including the kind of amendments, the scope of use, the experimental setting, and the research variables. The necessary conclusions were ultimately drawn qualitatively.

The use of soil stabilizers and amendments such as organic, inorganic, and biological elements to enhance the erodibility threshold and prevent soil water erosion has been widely documented based on the findings of this study. According to research findings, the performance of amendments varied depending on the kind, manner of application, scale, and soil type. In addition, the findings on the usage of amendments revealed that various additions are used and work well in soil and water conservation. However, adopting any of the customary changes has been noted as a considerable difficulty due to economic, environmental, health, administrative, functional, and technical restrictions. The use of biologically and ecologically friendly alternatives to boost the efficiency of the conditions for balancing and stabilizing the soil environment has been stressed due to the aforementioned constraints for the use of amendments.

Because of the widespread use of amendments, the feasibility of using environmentally friendly amendments, and emphasizing waste management in the primary industry through additional studies and research, there is a need for proper and appropriate measures that are naturally environmentally friendly in the long term. Nevertheless, additional research on the application of various amendments resulting from the direct or modified use of significant industrial wastes with respect to various aspects of environmental, economic, ecological, and even aesthetic and at different scales is necessary to summarize and develop appropriate executive instructions.

Drought and dust are serious atmospheric hazards that have affected the western and southwestern parts of Iran in recent years due to various reasons. Since numerous droughts have had a detectable impact on occurrence and severity of dust, therefore, related studies are considered important. The purpose of this study is to analysis the trend of dust storms frequency and its relationship with drought (SPEI).

Bushehr province is located in ​​ north of the Persian Gulf and southwest of Iran. To investigate the effect of drought on dust storm, data on the dust events at daily timescale, monthly precipitation, temperature, humidity-relative, evapotranspiration data were utilized from 7 synoptic stations over 30 years (1989–2018).The Standardized Precipitation  Evapotranspiration Index (SPEI), dust storm occurrence based on weather codes 06 and 07 events and linear regression of parametric statistical test were used to estimate of drought, dust storm index (DSI) and their trends were analyzed by parametric linear regression test method. Spatial distribution of drought and dust in the case study obtained in Arc GIS software by IDW method. To investigate the relationship between climate and dust storms, the data of stations with significant trend of drought and dust storms frequency were analyzed using linear regression.   

The results showed that the percentage of drought frequency were classified into mild drought (79.06%), moderate drought (18.96%) and severe drought (2%) in the whole 30 years. Approximately 6.25% of droughts is occurred in the first decade, 50% in the second decade and 43.75% in the third decade. The spatial distribution map of drought also showed that the main focus of this phenomenon is occurred in the southern, central and northeastern parts of Bushehr province than rest of other parts. Existence air currents from Arabian Desert towards the central area of the province, the lack of appropriate vegetation, soil erosion and sand and salt zones in these parts have confirmed this issue. The percentage of occurrence of different drought during the whole study period showed that the occurrence of mild droughts was more than moderate droughts and the occurrence of moderate droughts was more than severe droughts. The overall trend of DSI changes across the entire study duration was decreased.

This study showed that dust storm index with increasing drought intensity was decreased and its correlation with drought during the 30-year period was not significant. Overlaying both of spatial distribution maps of drought and DSI did not show homogenous distribution pattern. This indicates that human factors or external source of dust can play a more important role in creating heterogeneous distribution pattern of drought and DSI in Bushehr province. Finally, the relationship between drought and DSI has always fluctuated according to dry and wet years over the whole study period.

Dust storm is a phenomenon that occurs in arid and semi-arid regions due to high wind speed and turbulence on the surface of the soil without cover and prone to erosion. Dust changes the radiant budget of the earth's surface and changes the temperature of the earth's surface and atmosphere. Therefore, dust affects the energy exchange between the surface and the atmosphere as well as the dynamics of the atmosphere. Recognizing and studying the trend of dust storms and their relationship with climate change is one of the most important ways to reduce the damage caused by this phenomenon. This study amies to evaluate the effect of dust storms on radiation indices and heat flux according to the combination of satellite remote sensing information and re-analysis data in Hirmand basin.

In this research ERA5 re-analysis and Terra satellite data used for the August 23-26, 2010 event in Hirmand. Products and satellite data used including true color images and AOD and re-analysis data including Surface latent heat flux (SLHF), Surface Sensible Heat Flux (SSHF), Surface net Solar Radiation (SSR), Surface net Thermal Radiation (STR) and Balance Radiation (Rn). Dust particles were routed using the HYSPLIT model and wind speed in the study area was also assessed using the analysis data. Also, for validation of satellite data and re-analysis, visibility and air temperature data, at height of 2 meters, at Zabol Meteorological Station, closest station to the study area, were analyzed.

According to the HYSPLIT model output, most of the dust particles were collected from the deserts of Turkmenistan and then the dry areas around Lake Hamun and parts of northern Pakistan. AOD values showed that from August 21, the value of this index gradually increased so that on the 25th day, the maximum AOD value reached 1.25. Examination of the values of radiation and heat flux indices showed a significant decrease in SSHF, SSR, STR and Rn indices and their values reached the lowest value on the 26th day and the SLHF index with a slight difference on the 25th day reached its lowest value of 58 w/m2. Correlation study showed that SSR and Rn indices with -0.370 and -0.359 respectively had the highest and SLHF index with -0.153 showed the lowest correlation with AOD index.

The results of this study showed that the western parts of Hirmand Basin, Lavar or North wind has emitted dust particles into atmosphere, and the region and rotational currents has caused the distribution of these particles in the study area. The results of satellite data and their re-analysis and matching with real images showed that the study event increased the optical depth of dust particles, which resulted in tangible and surface heat fluxes, solar and thermal radiation, as well as balance. Radiation was greatly reduced. Evaluation of horizontal visibility and air temperature data at a height of 2 meters at Zabol station also confirmed the results of satellite images and re-analysis data.

Assessing and estimating sediment transport from a long time ago is one of the major issues for hydraulic and river engineers. Determining the amount of bed load carried in rivers depends on various factors, and this factor has complicated this phenomenon. Studies on different rivers show that the amount of bed load in different hydraulic and hydrological conditions is different. In addition, the physical properties of bed load particles have a significant effect on the accuracy of model prediction, On the other hand, despite the emphasis on the unreliability of experimental equations that have been extended over a specific area, unfortunately, limited studies have been conducted on temporary changes in bed load. Therefore, Investigating the predictability of this phenomenon is of great importance. In this study, we will try to estimate the bed load in gravel bed rivers using classical and intelligent methods.

Machine learning methods due to their high accuracy in predicting various issues have been noted in recent years . Therefore, in the present study, two methods of classical artificial neural network (ANN) and deep learning of long short-term memory (LSTM), which is a kind of artificial neural network with layers and amplification algorithms to improve network performance; have been used to predict the bed load of 19 gravel-bed rivers. To define suitable models for networks, the results of 10 experimental formulas in bed load prediction have been evaluated and the parameters of superior formulas have been used as the input of intelligent networks.

The results showed that all experimental formulas had very poor results; As most formulas have predicted the bed load with a Discrepancy index of r greater than 100. However, machine methods with input parameters obtained from experimental formulas have acceptable accuracy in predicting bed load. and in comparison with machine methods, LSTM method has provided more accurate results than ANN method. Finally, the model related to the parameters of Begnold formula in LSTM method with DC= 0.900 and RMSE= 0.024 for the test data is the best model obtained from this research and The average diameter of sediment particles (D50), which is a common parameter of the top three models, has been selected as the most effective parameter in predicting bed load.

Despite the very poor performance of experimental formulas in predicting sediment transport, intelligent networks with input parameters derived from experimental formulas have had good results. Also, LSTM network is more efficient than artificial neural network (ANN) in predicting bed load transfer, which indicates that Maintaining training memory during the training process and adding reinforcement layers to the network improves network performance and increases network accuracy in subsequent training.

The purpose of incorporating organic modifiers such as biochar with soil is stabilizing carbon, improving fertility, absorbing pollutants, and consequently increasing crop production. Biochar is a biofuel and the resultant of organic matters thermocouples. Biochars are produced in high temperature ovens and are commonly alkaline and so suitable for the acidic soils. However, if the raw materials are heated at low temperatures, the resulting biochar can be acidic and useful for modifying calcareous soils. The aim of this study was to investigate the effect of two types of acidic biochars of rice husk and pine cone for modifying the physical properties of two calcareous soils of Isfahan province.

Based on a preliminary experiment, rice husk biochar (pH=5.64) and pine cone biochar (pH=6.56) produced at 300°C were selected for this study. The experiment was performed in a completely randomized factorial design with three replications. Treatments included two types of biochar (pine cone and rice husk) mixed with soil at one, three and six percent (g/g), two types of soil (a sandy loam, Tiran and a clay loam, Lavark), and two incubation periods of one and six months, with 4 controls and a total of 28 pots. The treated soils were kept in an incubator at 25°C and 60% of field (pot) capacity. At the end of the incubation periods, the soil moisture contents at field capacity and the permanent wilting point were measured respectively using sand-kaolin box and pressure plate devices and then soil available water contents was calculated.

The results showed that the addition of biochars improved some physical properties of soils. The treatment of the soils with 3% and 6% of biochars caused significant increases in the available water (AW) in the sandy loam soils compared to the control. The physical quality index of Dexter (SDexter) fitted by van Genuchten–Mualem was significantly increased in the sandy loam soil amended with 6% of the biochars and in the clay loam soil amended with 3% and 6% of the biochars. The use of biochars also improved the physical quality of the soil, described by the Dexter index, from poor to very good.

The results of this study showed that addition of 6% rice husk biochar to the clay loam soil and at the 30 days incubation period, could improve soil properties. Therefore, according to these findings, the biochars produced from pine cones and rice husk can be suggested as a suitable conditioner for improving physical properties of the regional calcareous soils.

More than twenty percent of Golestan Province of Iran is covered by wind-blown deposits called as loess. These deposits are silty or loamy materials with yellow to light brown colors. Special erosion phenomena such as pipe and tunnel erosion are common in loess deposits that are important in terms of studying their hydrology and the hydrologic response of the catchments influenced by these phenomena. In this paper, with briefly describing the hydrology and erosion situation of Tamer watershed located in the northeast of Iran with dominant cover of loess deposits, using the Height Above Nearest Drainage map (the topographic index HAND) and the slope map, three hydrologic landscapes were determined. For each of these three hydrologic landscapes (lowland, hillslope and plateau), a conceptual hydrologic model according to the FLEX-Topo model was designed and described. In the FLEX-Topo model, the spatial variation is taken into account by the zonation of the watershed based on topography in a semi-distributed fashion. Considering the intense presence of piping and tunnel erosion in the region and its impact on the hydrologic response of the watershed; in particular, with some changes in structure and formulation of the common structure of FLEX-Topo, a tailor-made conceptual model was suggested and its formulation, required for programming, was described. Likewise the FLEX model, in the FLEX-Topo model four reservoirs including the interception, the unsaturated, the fast response and the slow response reservoirs along with a time lag function play important roles. To consider the effect of piping in the proposed model (FLEX-Topo-P), a splitting parameter for the input rainfall and a shared fast reservoir between hillslope and plateau landscapes were suggested. The proposed model has to be implemented and tested through a methodic and robust research, and its performance has to be evaluated in comparison with flow observations and benchmarked with the FLEX-Top. 

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.