جستجوی مقالات مرتبط با کلیدواژه "soil physical properties" در نشریات گروه "آبخیزداری، بیابان، محیط زیست، مرتع"

Soil properties and land use affect the soil carbon content and reduce the adverse effects of climate change. This study aims to assess the effect of some physical properties of soil and land use on the amount of soil organic carbon content (SOC) and model development to estimate the amount of SOC. This investigation was carried out in 2020 in the areas of flood spreading in of Fasa (Kowsar station). Land uses included acacia (Acacia salicina Lindl.), eucalyptus (Eucalyptus camaldulensis Dehnh.), atriplex (Atriplex lentiformis (Torr.) Wats.) plantation, and natural rangeland, all of which are irrigated by flood spreading. By sampling in three replications of the soil of different land uses from the depth of 0-30 cm (15 composite samples), percentage of sand, silt, clay, silt+clay, percentage of soil saturation moisture (SP), bulk density (BD), particle density (PD), porosity percentage (PS), void ratio (VR) and SOC were determined. Obtained data were statistically analyzed in a complete randomized design and the means were compared with the Duncan test at P<0.05. The analysis of variance showed that the effect of land use (PT) on the percentage of sand, silt, silt + clay, SP, BD, PS, VR, and SOC has been significant at P<0.01, and the clay, at P<0.05. Comparison of the means of SOC in different land uses showed that the Eucalyptus forest, with 1.68%, has the highest value and the control with 0.14% organic carbon has the lowest value. There was no statistically significant difference between the SOC in Acacia forest, Atriplex, and rangeland. Stepwise regression analysis was used to present the model. Soil physical properties and land use were considered as independent variables and SOC was considered as a dependent variable. The results showed that the variable of silt explains 77.00% of the changes in organic carbon. Based on the principal component analysis (PCA) method, according to the specific values, considering the first two axes, about 91.70% of the changes can be explained. Considering the first axis, 69.71% and considering the second axis, 21.99% of the changes are justifiable. The PT, with 91.40%, sand with 84.30%, BD, 82.70%, showed a negative correlation with SOC. While the SP had 90.30%, percentage of clay+silt had 84.80%, PS, 80.70%, VR, 79.10%, silt, 78.50%, clay, 78.50%, had a positive correlation with SOC.

To evaluate the effects of grazing on some physical and chemical properties of soil, in the summer rangelands of southern slopes of Sabalan, three regions with different grazing intensity were selected after field observation and 27 soil samples were randomly taken along three 200-m transects. Soil samples were taken from the depths of 15-0, 30-15 and 45-30 cm and transported to laboratory and soil properties such as texture, organic matter, organic carbon, phosphorus, potassium, EC and pH were measured. Analysis of variance and mean comparison were made using Duncan's test. Results showed that no significant difference was found for soil pH and phosphorus among the grazing intensity treatments and soil depths; however, significant differences were observed for other variables. The results showed that organic matter content decreased with increasing of grazing intensity and the lowest content was recorded for the 30-45 cm soil depth in the heavy grazing area. According to the results of this research it can be concluded that soil structure is degraded with increased grazing intensity; therefore, a balanced grazing need to be taken into account in summer rangelands to prevent soil degradation.

The present research was conducted with the purpose of assessing the interaction between some soil properties and runoff generation time in the downstream of Educational and Research Forest Watershed of Tarbiat Modares University (Kojoor Watershed) located at Southeastern of Nowshahr. Rainfall simulation was done through applying a pumping rain simulator generating rain intensity of some 1.6 mm min-1. Accordingly, runoff generation time was determined from starting time of the simulation until runoff generation. In this research, some soil characteristics such as percentages of organic matter, clay, Silt, sand, antecedent soil moisture contents and soil bulk density were analyzed at two topography characteristics of slope steepness and aspect. For statistical analysis, a normality and variance homogeneity test was firstly carried out and variance analysis was then adopted. The significant relationships were ultimately evaluated using the Pearson correlation test. Results showed that the soil properties were strongly correlated to each others. Amongst them, there were just a positive correlation between the percentage of organic matter and topography properties with runoff generation time in the significant level of 5 %. Most of the runoff generation time were measured from plots of 44% and located at the western aspect that had the highest percentage of organic matter of 5.9%. It could be inferred from the results that the runoff generation time was significantly sensitive to environmental variables.

Evaluating the effects of different grazing intensities on soil physical and chemical properties is required to achieve appropriate management plans. This study was conducted in three rural areas in Sabalan mountain rangelands. A random systematic sampling method was used to collect soil samples along 600 meters transects. Six composite and 18 intact soil samples were collected using soil sampling cylinders within two depths including 0-15 and 15-30 cm from soil surface. According to the results, soil humidity percent, porosity, particle density, texture, and mean weight diameter were among soil physical charatersitics that were significantly affected by grazing in the study area. Soil organic matter, nitrogen, phosphorus, potassium, pH and EC were also affected by severe grazing pressure. Continuing heavy grazing leads to destruction of soil structure, hence controling grazing intensity is very important to avoid irreversible and inappropriate changes in soil characteristics.

Many natural fires occur in arid and semi arid rangelands that may result in destruction of desirable forage and also erosion of valuable rangeland's soil which eventually will lead to great environmental and financial losses. To study the effects of fire on soil physical and chemical properties, a research project was defined and carried out in semi steppe rangelands of Kordan located in southern Alborz Mountain north east of Karaj city. A randomized completely block design was used with two treatments (control and burned rangelands) and 15 replications in year 2008. Soils of the studied area (control and burned rangelands) were examined using sampling in the first spring season after fire was occurred. In each quadrate, percentage of canopy cover was measured. Statistical analysis was performed through factorial experimental design and means comparisons were done by Duncan's test. According to the results of soil analysis, amount of total N, absorbable phosphorous, absorbable calcium and soil organic carbon decreased after the fire. Magnesium absorbable, Cation exchange capacity and percentage of clay increased after the fire. Fire also had no significant effects on the percentage of sand, silt and soil bulk density.

Since vast areas of forest lands have been changed in their usage in Mazandaran province in the past decades، this study examined the impact of changing in usage of forest lands in to the agricultural rain-fed lands (canola)، paddy lands and citrus gardens on some physical and chemical properties of soil in the Eastern part of Sari، Iran. For this purpose، four repetitions from each land use were sampled from 2 depths of 0-20 and 20-50 centimeters as factorial design in complete randomized block pattern. Results showed that land use change causes increase in bulk and particular density، the content of bulk density، which in depth، was more than that in surface layer. The most percentage of silt، clay and sand particles was observed in forest، paddy lands and garden usage، respectively. Change in usage caused decrease in water holding capacity and residual moisture. The most percentage of aggregates stability was found in forest and paddy lands. The highest amount of porosity and previous moisture was observed in paddy lands. Land use change caused an increase in soil reaction which increases with depth too. Land use change caused a decrease in organic carbon، the most percentage of which was 2 percent related to forest lands and the lowest percentage of which was 0. 72 percent which was related to rain-fed lands. The lowest available phosphorus was related to rain-fed lands too and the most amount of electrical conductivity was related to paddy lands.