Aliakbar Noroozi; Morteza Miri; Davoud Nikkami; Tayeb Razi; Amir Sarreshtehdari; Ziaedin Shoaei
Abstract
The purpose of this study was to investigate the oak forest dieback with respect to drought occurrence, soil moisture changes and dust occurrences factors in Ilam, Kermanshah, Lorestan and Chaharmahal and Bakhtiari provinces of Iran. The data used were field surveys collected through GPS, MODIS satellite ...
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The purpose of this study was to investigate the oak forest dieback with respect to drought occurrence, soil moisture changes and dust occurrences factors in Ilam, Kermanshah, Lorestan and Chaharmahal and Bakhtiari provinces of Iran. The data used were field surveys collected through GPS, MODIS satellite imagery, GLDAS Soil Moisture, dust and precipitation data of the meteorological stations of the provinces during an 18-years period (2000-2017). The results of the study of greenness values of the forests in the study area showed that the first decline occurred in 2005 and repeated more severely with much wider spatial extent in 2008. Investigation of the relationship between drought events and its spatial and temporal variations with the changes in forests greenness of the study area showed that the reduction in precipitation amount is one of the main reasons for forest greenness reduction in the study area. The increased frequency of periods of rainfall shortage and drought duration, especially at 9 and 12-month time scales, showed a significant relationship between drought occurrences and forests greenness in the study area. The results indicated that by decreasing precipitation drought periods increased, soil moisture decreased, and dust storm occurrences increased. As a result, in most of the years, with decreasing soil moisture and increasing dust storms, the forests greenness of the study area has decreased and vis versa. Therefore, there is a direct relationship between soil moisture and forest greenness while an inverse relationship exists between dust and forest greenness.
Alireza Majidi; Golamreza Lashkaripour; Ziaedin shoaei
Abstract
Erodibility, resistance and soil engineering behavior are affected by their physical and chemical properties. Lithology and characteristics of parent rock can be such factors that influence on soil properties and behavior. The aim of this study was to investigate and compare some of the physical properties ...
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Erodibility, resistance and soil engineering behavior are affected by their physical and chemical properties. Lithology and characteristics of parent rock can be such factors that influence on soil properties and behavior. The aim of this study was to investigate and compare some of the physical properties of Marly fine grained soils with two different maternal formations in a unit basin (Qom salt lake). The study was carried out on 61 soil samples. The physical parameters studied are the specific weight of the unit volume of soil, the grain size, the Atterberg limits and the soil activity number, which was measured according to ASTM standards. The investigation of the above mentioned soil properties showed that the soils of these two marl formations are silty and all are classified in the category of fine-grained soils with low to moderate plasticity. The values of the soil activity number and the Atterberg limits, especially the plasticity limit and plasticity index, indicated that the clay minerals in these soils are more Kaolinite and Illite and less montmorillonite. The comparison of variance and mean of physical properties of two groups of soil by using t-student (two independent groups) test, showed that in most of the physical properties of two Marl Soil groups consist of liquid limit, plasticity index, soil activity number and percentage of clay, silt and sand, there is a differences significant level of confidence of over 95%. This difference of physical properties was validated by clustering the samples by hierarchical method. Considering to the unit basin and similar conditions in the formation and evolution of these two groups of soil, the results of this study indicate that conditions and characteristics of the sedimentary environment of the matter rocks mainly affected on the properties and behavior of soils, especially in their early stages of evolution.
