Davood Davoodi Moghadam; Seyed Hamidreza Sadeghi; Mahmood Azami Rad
Abstract
Introduction: It is vital to control land degradation, for conserving precious natural treasures. Quantification of runoff production and soil and nutrient loss from wild lands under different managerial systems is one of the scientific and optimal management in agriculture and natural resources, as ...
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Introduction: It is vital to control land degradation, for conserving precious natural treasures. Quantification of runoff production and soil and nutrient loss from wild lands under different managerial systems is one of the scientific and optimal management in agriculture and natural resources, as a major component of sustainable development. Many researches have been conducted to assess the effects of different land uses on soil erosion and runoff generation throughout the globe. Most of which, mainly verified the detrimental effects of human intervention on land degradation. However, limited comprehensive and comparative studies have been conducted to consider the amount of surface runoff generation, and soil and nutrient loss from watersheds with different management patterns viz. untreated and treated small watersheds.
Materials and Methods: The present study aimed to compare surface runoff generation,soil and nutrient loss in Kakhk treated and untreated watersheds with an area ca. 222 ha and precipitation of some 243 mm per annum. Other physical and geological characteristics of the paired watersheds were also similar to allow assessing the effects of study measures on soil, water and nutrient losses. The area under consideration has been located in Khorasan Razavi Province in northeastern Iran. The present study was performed in plots with standard size of 22.1 × 1.8 m in treating and representative areas, with three replicates and on the storm basis occurred during early 2011 and mid-2014. The treated plots were covered by biological measures viz. seeding, bunching and exclusre. The study plots have been situated on eastern,western and northern aspects with respective slope of 55, 40 and 40 %. The entire runoff from study plots were collected in a container in 0.5×1×1 m. The sediment concentration was also measured in 2-liter samples taken from the container after a complete mixing of the entire collected runoff. The sample was treated by decantation technique, oven dried and weighted by high precision scale. The transported elements, i.e. potassium, phosphorous and nitrogen were also measured in solute and particulate forms. Ultimately, the data bank was developed in Excel 2010 and got ready to be processed in SPSS 19.0 software package and statistically compared with the help of analysis of variance (ANOVA) test.
Results and Discussion: The results showed that the soil loss, nitrogen concentration, potassium concentration and sediment concentration had significant difference (p
Shirko Ebrahimi Mohammadi; Mahmood Azari; Esmaeel Manoochehri
Abstract
Introduction: Forest herbs due to decrease of runoff coefficient and the kinetic energy of raindrops, is known as a key factor in controlling runoff and soil conservation. Many physical (hydrophobicity, electrical conductivity, pH, particle size distribution, color and temperature regimes), chemical ...
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Introduction: Forest herbs due to decrease of runoff coefficient and the kinetic energy of raindrops, is known as a key factor in controlling runoff and soil conservation. Many physical (hydrophobicity, electrical conductivity, pH, particle size distribution, color and temperature regimes), chemical (quality and quantity of organic matter, nutrient availability) and biological (Microbial biomass, soil invertebrates living community) soil properties can be affected by forest fires. Fire not only reduces forest herbs, vulnerability against splashing rain but also has strong effects on the hydrological cycle and soil loss. despite of repeated fires, there are very few studies about fire impact on natural resources of the west of the country, especially the city of Marivan, in Kurdistan province so this study aimed to investigate the short-term fire impacts on soil properties, Hydrologic regime, soil erosion and sedimentation of Zrebar Lake watershed in west of Iran.
Materials and Methods: Considering the importance of the slope on the hydrological response of the watershed, slope classes of the Zrebar Lake watershed were mapped. Therefore, effects of fire on hydrological characteristics, erosion and sedimentation were studied by the establishment of twelve 0.25 square meter plots in three replications at two dominant slope classes (0 to 30 and 30 to 60%) in burned and natural areas . The first plots in the burned and natural sections, was established randomly and two other plots with the similar conditions at a distance of 1.5 meters from each other were established. Garden Spray Simulator with constant pressure was used to fall rain from half a meter height for thirty minutes with an intensity of about 2 mm min-1 and 1 mm droplet diameter according to the general weather conditions of the studied area. For every five minutes, runoff and sediment were collected. Runoff volume by weighting and suspended sediment concentration by drying at 105°c were measured. Infiltration and interception by water balance assessment and subtracting the simulated rainfall volume and runoff were calculated. Soil samples were also collected in triplicate by auger drilling method to assess the effects of fire on different characteristics of topsoil (depth of 5 cm) asthe samples 1 and 2 in the slope class of 30 to 60%, and samples 3 and 4 in slope class of 0 to 30%, at the burned and natural sections respectively. In the laboratory, after determination of soil texture, the moisture content, pH and EC by portable laboratory instruments, the percentage of total organic carbon and organic matter bye wet oxidation were measured. Soil water repellency by Water Drop Penetration Times (WDPT) method in the field was calculated. Statistical analysis for comparing the average hydrophobicity of the soil, runoff and sediment of both natural and burned treatments by independent t-test and for equality of variances by the Levene test was performed using SPSS 21 software.
Results and Discussion: The results showed no effect of fire on soil texture because the fire severity was low to moderate as the color of ash was black. The fire caused to 46 percent reduction of soil moisture and also 24 percent reduction of soil organic matter and 29 percent reduction of total organic carbon at 0% to 30% and 30% to 60% slope classes respectively. Slight increase in pH and electrical conductivity were another effects of fire. At the slope of less than 30%, the average water drop penetration time were 1.24 and 0.70 S in burned and natural treatments and at the slope of 30 to 60 % slope class were 4.52 and 1.04 S respectively. Independent t-test results showed that, the water repellency differences of natural (t=3.466, p=0.003) and burned (t=7.364, p=0.000) treatments were significant. Levene test and independent t-test results showed significant difference in the average of runoff at confidence level of 95% in both slope classes. At the slope of less than 30%, differences of sediment average of burned and natural plots with a significant level of 0.012 were significant. But in slope class of 30% to 60%, despite of large different sediment concentration output from the burned and natural plots at the beginning of the experiment, there was no significant difference between them. The results showed that fire leads to low soil moisture content, total organic carbon and soil organic matter. Slight increase of pH and EC and also lack of effect on soil texture, in both slope classes were also observed. Ash on the forest floor caused to soil water repellency and therefor decreased soil infiltration and increased runoff and soil erosion.
F. Asadzadeh; manoochehr gorji; A. Vaezi; S. Mirzaee
Abstract
Introduction: Field plots are widely used in studies related to the measurements of soil loss and modeling of erosion processes. Research efforts are needed to investigate factors affecting the data quality of plots. Spatial scale or size of plots is one of these factors which directly affects measuring ...
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Introduction: Field plots are widely used in studies related to the measurements of soil loss and modeling of erosion processes. Research efforts are needed to investigate factors affecting the data quality of plots. Spatial scale or size of plots is one of these factors which directly affects measuring runoff and soil loss by means of field plots. The effect of plot size on measured runoff or soil loss from natural plots is known as plot scale effect. On the other hand, variability of runoff and sediment yield from replicated filed plots is a main source of uncertainty in measurement of erosion from plots which should be considered in plot data interpretation processes. Therefore, there is a demand for knowledge of soil erosion processes occurring in plots of different sizes and of factors that determine natural variability, as a basis for obtaining soil loss data of good quality. This study was carried out to investigate the combined effects of these two factors by measurement of runoff and soil loss from replicated plots with different sizes.
Materials and Methods: In order to evaluate the variability of runoff and soil loss data seven plots, differing in width and length, were constructed in a uniform slope of 9% at three replicates at Koohin Research Station in Qazvin province. The plots were ploughed up to down slope in September 2011. Each plot was isolated using soil beds with a height of 30 cm, to direct generated surface runoff to the lower part of the plots. Runoff collecting systems composed of gutters, pipes and tankswere installed at the end of each plot. During the two-year study period of 2011-2012, plots were maintained in bare conditions and runoff and soil loss were measured for each single event. Precipitation amounts and characteristics were directly measured by an automatic recording tipping-bucket rain gauge located about 200 m from the experimental plots. The entire runoff volume including eroded sediment was measured on storm basis using the collection tanks. The collected runoff from each plot was then mixed thoroughly and a sample was taken for determining sediment concentration by weight. The per-storm soil loss was then obtained.
Results and Discussion: A wide range of rainfall characteristics were observed during the study period.The results indicated that the maximum amount of coefficients of variation (CVs) for runoff and soil loss from replicated plots were 60 and 80 percent, respectively, which were considerably higher than the variability of soil characteristics from these plots. CV of runoff and soil loss data among the replicates decreased as a power function of mean runoff (R2= 0.661, P
