جستجوی مقالات مرتبط با کلیدواژه « Dust » در نشریات گروه « جنگلداری »

This study was conducted in 2020 with the objective of identifying dust source areas and soil susceptibility to wind erosion in the eastern part of Kerman Province, through the integration of field and remote sensing methods. In total, ten study areas covering 3007 square kilometers were identified based on remote sensing and field surveys during the winter of 2020. The dust-prone areas and the determination of the dust event frequency in the past 20 years were established using the optical depth index derived from MODIS Terra and Aqua satellites. To assess soil erodibility, wind erosion threshold velocity, and wind erosion rates, soil samples (17 in total) were measured in a wind tunnel at three wind speed classes: 15, 20, and 25 meters per second. Electrical conductivity (EC) values of soil samples (22 in total) were determined in the laboratory to create a soil salinity map using the kriging method. The results of the vegetation cover index were extended, and the linear relationship between EC was computed using Google Earth Engine and compared with kriging results, indicating significant salinity in the studied areas (EC>16). The analysis of prevailing wind directions and wind regimes based on data from five meteorological stations in the region demonstrated that the Rigān and Nasratābād stations, with transport potential of 561 and 1199 kg m^-1 s^-1, respectively, were classified as high-energy wind zones. Wind speeds of 40 knots (20.57 m/s) were prevalent in these areas. The assessment of soil erodibility revealed that the southern parts had the lowest wind erosion threshold velocity (between 6 to 8 m/s), classifying them as wind erosion-sensitive zones, with an accumulated wind erosion rate of 60 kg/m^2/year across the three wind speed classes. Based on the findings, the study areas are considered significant internal dust source areas, requiring management actions to control dust emissions.

Oak decline is a complex phenomenon affecting vast areas of Zagros forests. Dust is the most important factors in the decline of Zagros forest. In order to assess the impacts of dust on oak decline, six dust traps were installed in Helen protected area at the beginning of spring 2016. Dust samples were collected using the traps surface in autumn. The weight of dust samples and the amount of heavy metals were measured in the laboratory. Three transects (replicates) with fixed distances were designed in each of northern and southern directions. In each transect, three circular plots (with an area of 1000 m2) were laid out in three altitudinal ranges (1500-1800, 1800-2000, and more than 2000 meter a.s.l.). In each plot, leaf samples of five trees were collected from healthy and unhealthy trees, and the amounts of heavy elements including lead, cadmium, nickel, arsenic and mercury were measured. The results showed that cadmium and lead in leaves of healthy and unhealthy trees had a significant difference and the amount of these elements in the leaves of healthy tree was more than unhealthy trees. Higher amounts of heavy metals were absorbed by oak trees located in the southern aspect compared with those in the northern one. Moreover, the amounts of intercepted cadmium and lead had significant differences. It seems that the stress caused by the absorption of these heavy elements in the leaves of trees is one of the most important factors for oak trees decline.

This study was designed to evaluate the presence of some heavy metals in dust as well as their influences on soil, leaves and twigs of Brant`s oak (Quercusbrantii Lindl.) at a study site located in Meleh-Siah, Ilam province. For two groups intact and declined trees, we measured four elements including Pb, Zn, Ni and Cd in twodifferent time spots (April and September 2013) during the growth period corresponding to the dust events. Sampling results showed an increase in the amount of all elements except for zinc in the sub-canopy soil for both groups of trees. By showing a significant increase (p