فصلنامه پژوهش های فرسایش محیطی
سال چهارم شماره 4 (پیاپی 16، زمستان 1393)

The aim of this study is investigates the effects of different patches shrubs on the soil surface indicators in Gub Gugeh rangelands, in Golestan Province. The sampling was taken along transects of 50 meters, which are 10 meters away from each other. Via LFA models, three factors of stability, infiltration and nutrient cycling using 11 indicators of surface soil in patch and inter-patch were measured. In the study area exist three patches rangelands including shrubs patch Suaeda (Suaeda physophora), sagebrush (Artemisia sieberi) and mixed patches (Artemisia sieberi + Suaeda physophora). The inter-patch areas (barren soils + litter) were identified, as well. The obtained result shows the stable characteristics between mixed patch and sagebrush patch, and there are no significant differences. Considering the permeability index, the highest rate belongs to mixed patch, but, the lowest permeability belongs to the areas of barren soil and litter. The nutrient cycling index indicates significant differences among the patches in the study area. In general, it shows the mixed ecologic patches (Artemisia sieberi and Suaeda physophora) improve the properties of more than other considered patches. Therefore, the mixed patched can be considered as an ecological index in the study area. The studies of functional features of patches of rangelands will help effectively in the detection the healthiness of arid and semi-arid rangelands, the improvement of soil conditions as well as the recognition of the effects of managerial and natural changes of rangelands.

Flood spreading is among preventing method from damage of deluge, especially perishing of water and soil in latrine basins of arid and semiarid regions. Accumulation of sediments on the flood spreads regions lead to changes in soil fertility, revival and support of plant covering and controlling of desertification and change in physicochemical properties of soil in these regions. In order to measure of soil changes in the station of flood spreading Hashtbandi, Minab, Hormozgan, were dipped 12 cavities in two regions: flooded and control. Sampling was done from 0-30 cm and 30-60 cm depth. Physicochemical properties were evaluated in the samples. The obtained results indicated that the average of organic carbon, total nitrogen, amount of potassium and phosphorous, EC as well as sand percent significantly increased in the flood spreading region than control region and clay percent, pH and saturating percent (SP) decreased in the flood spearing region than control region. Beside, silt amount non-significantly decreased in the flood spreading region than control region. Generally, can be said flood spreading system changes the soil texture during the time and has positive effect on soil fertility. Increasing amount of macro elements such as N, P and k as well as reduction of pH are positive effects for enhancing soil fertility, although increasing EC may be limited planting of some sensitive crops.

Abstract The forest road is most important sediment sours in the forest regions. the forest roads with remove vegetation cover and disorder hydraulic behavior regions, causes sediment product and problems due of sediment. This study has been done to surveying sediment factors roll in the sediment producing in the northern forest road. For this goal were selected purpose road sections by using homogenous unit map (rainfall, aspect slope, hillside aria and geology) in geography information (GIS) and operation studies, in the culverts output selected sections, were created wooden sediment trapping dams. Spearman analyses Results shown then maximum correlation with high cut slope in the sediment product. Also The result of analysis variance and comparing between the average sediment produced in different slope classes showed positive and significant different. with increase of road age and vegetation cover the amount of sediment significantly decreased. The amount of total sediment that evaluated in study area was about 51 ton in year.

Dust storms and high winds is a natural process that occurs in everywhere of arid and semi-arid land in the world. The phenomenon of dust is one of the most important consequences of the desertification that cause different damages. The aim of this study was to analyze the occurrence of dust in the city of Bandar Abbas. First, the frequency of monthly and annual dust from 1985-2005, in the city of Bandar Abbas was paid and then By using Mann-Kendall trend of phenomenon of dust as monthly and annual in Bandar synoptic stations were examined, and drawing Annual Wind Rose diagram of prevailing winds in the region. The overall results of the analysis with the Mann - Kendall in this period indicated that occurrence of days with dust is a constant process. And monthly trend analysis showed that trend from January to September period is constant and latest month is not constant trend. Study of Charts as partial indicates that the dust has increased since 1996 and then decline and again in 2000 this trend has increased. And because of its, reduced combat operations the phenomenon of dust and increases harvest locations in the province. The results of the correlation between annual precipitation and dust indicated that the rainfall has decreased in the years of dust has increased. As well as results of winds study showed that the higher speed winds in the dry months have increased. Rose diagram showed the direction of the prevailing wind in the region is north and the most frequent wind speed at station is 55/4 meters per second.

Soil erodibility factor is a criterion of soil particle resistance to detachment, transport, and effects of erosivity factors (rain drop, runoff, and wind) during the soil loss processes. In this study, non-linear support vector machines (SVMs) method was used for investigating the effects of some topography, soil physical and mechanical properties on soil erodibility in a part of Northern Karoon watershed at the west of Chaharmahal Bakhtiary province. The obtained results were compared with the outputs of a linear (i.e. multiple linear regression, MLR) method. Furthermore, potential use of the two methods for estimating the soil erodibility factor was investigated in the study area. The correlation coefficient (r), root mean square error (RMSE), model efficiency factor (MEF), and error percentage (ERROR%) were used to evaluate the performance of the models. The results showed that the constructed SVM model had greater performance in predicting the erodibility factor compared to the traditional MLR model. The obtained ERROR% and r values for the developed SVM model were 0.07 and 0.90, respectively. The obtained MEF value for the erodibility factor prediction using the SVM model was 76.79 % while it was -18.04 % for the MLR model. The results from determining the properties influencing the soil erodibility in the investigated points using the two methods revealed that only the sand content, aspect, pods (size between 0.25-0.5 mm), clay content properties were accounted as effective parameters according to the MLR model. Whereas, all investigated properties were determined as effective parameters resulting from the non-linear SVM model. However, the parameters mean weight diameter (MWD) and sand content (size between 0.25-0.5 mm) had the highest importance coefficient and aspect parameter had the lowest coefficient.

Conservation of vegetation is one of most important tools for conservation of soil and decreasing erosion. Therefore, knowledge about vegetation characteristics, such as diversity, is the first and most important biological tools for soil conservation. One of the methods in which we can collect useful data about plant diversity, is additive partitioning. In the current study, plant species diversity components along elevation gradient were studied in the Gen omountain using additive partitioning. All plant species were listed and measured their cover percentages in 15 elevation zones in south aspect using 5 4m2 quadrats in each zone. All plant species diversity (γr) partitioned into additive components within plots (α1) and between plots (β1) and among elevation Zones (β2). We used PARTITION software to analyze the species diversity components in different scales. The results showed that the highest number of species is related to intermediate elevations (1200 to 1700 m a.s.l.). Irano-Turani had the highest number of species in the study area. β1 Diversity with 71.13% had the highest contribution in γr and in expected rate. β2 with 16.36% had the lowest expected rate. We concluded that all scales should be accounted for conservation of all plant species. Using of additive partitioning showed us the scale that has the highest contribution into the total-regional diversity and the best scale that should be considered in conservation projects.