جستجوی مقالات مرتبط با کلیدواژه « حرارت » در نشریات گروه « آب و خاک »

Changing land use is one of the most important human interactions in natural ecosystems that affect ecosystem processes, especially soils. In the present study, the effects of forest (natural forest and oak plantation) and non-forest (garden, rangeland and agriculture) land sues on the variability of soil quality indices and carbon dioxide emission dynamics have been considered. In each of the proposed land uses, 16 soil samples (0-10 cm depth) were collected and transferred to the laboratory. According to the results, the highest amounts of soil organic matter were allocated to forest habitats and the highest bulk density was belonged to rangeland and agricultural areas. However, the variation of soil particle density among the various land uses was not significant, but the highest soil porosity was found under oak plantation. The natural forest has the most stable aggregates, and following deforestation and the land use change, their stability was significantly reduced. The highest amount of sand was belonged to rangelands and the highest amount of clay was allocated to natural forest, while the content of silt did not show significant differences among different land uses. The highest amount of coarse root biomass was observed in the natural forest and oak plantation, while the fine root biomass in the natural forest was the highest amount. Greater amounts of soil moisture content were found in the forest habitats (especially in winter and autumn), while the highest soil temperature was assigned to agriculture and rangeland areas (especially in summer). The emission of carbon dioxide from the soil was highest during the summer, under the oak plantation. According to the PCA output, the amount of soil organic matter, moisture content and porosity in the oak plantation have had an important role in increasing carbon dioxide emission from the soil of this type of land use compared to other sites. The results of this study confirm the protection of natural forests in order to increase the soil quality characteristics and health.

Usually، dry soil readily absorbs water. However، not all soils display such characteristics. Some soils (hydrophobic soils) show resistance to wetting. Because of the importance of this subject and lack of research، we evaluated the effect of heating on water repellency and some of soil physical and chemical characteristics. So soil was combined with compost and heated at deferent temperatures، 100، 200، 300، 400 and 500 °C for 30 minutes in an oven or muffle furnace. The results showed that control treatment and heated soil at 300 °C had WDPT and MED 45 (s)، 17% and 80 (s)، 23% respectively. So، little water repellency was present prior to heating the soil. When soil was heated up to 300°C، intense water repellency resulted، but it was abruptly eliminated by increasing the heating. The soil texture was changed from loam to sandy loam at high temperatures (400 & 500 °C) and the sand percentage was increased. Organic matter decreased by increasing the temperature. Amount of pH decreased up to 200 °C and then increased at 500°C because of increasing ash in soils. Diminution of mineral and organic matter caused EC to decline in all the heated soils.

Heating affects soil physical and chemical properties and sometimes causes soil water repellency. In order to investigate heating effect on water retention curve، an organic soil was heated in a muffle furnace preheated at 100 (T100)، 200 (T200)، 300 (T300)، 400 (T400) and 500 °C (T500). Hence، the soil was exposed to five heating treatments in three replications، in a completely randomized design. Water repellency was determined by using water drop penetration time method and aqueous ethanol method. Water retention curve of the treatments was determined by means of sand box and pressure plate. The van Genuchten equation''s parameters were obtained by minimizing mean square procedure and using RETC software. Then، heating effects were determined using SAS8 and LSD model. Some properties of water retention curve in heated and unheated soils were measured. The results showed that the original soil had low water repellency، while، at 300 °C، strong water repellency appeared، but disappeared by increasing the temperature. Van Genuchten equation''s parameters changed by increasing temperature and water repellency. The hydrophobic soils had low saturation water content compared to the other treatments with similar texture. T500 had the least saturation water content، probably because higher temperature decreased organic matter and increased sand and ash content. The value of α in hydrophobic soil was lower than other treatments with the same texture، but the “n” parameter in hydrophobic soils was higher than that in T100 and T200 treatments. Since this parameter is lower in heavy soils than light soils، it was low in T400 and T500 with sandy loam texture compared with the other treatments with loam texture. Water content at field capacity and wilting point diminished by increasing temperature.

In this study diflubenzuron as a chitin synthesis inhibitor with a dosage of 25 mg A.I/L, and Pyriproxyfen as a juvenile hormone analogue with a dosage of 0.4 mgA.I/L were incorporated in the wax diets of young and last instar larvae of greater wax moth and reared at different temperatures (25, 30, 35°C). Results showed that these compounds in comparison with control increased larval mortality. Diflubenzuron and pyriproxyfen caused 33.9% and 24.1% mortality respectively. The young larvae showed higher mortality with the mean of 57.8% in diflubenzuron and 31.5% in pyriproxyfen. In evaluation of pupation and emergence of adults, no significant differences were observed between diflubenzuron and control. Pyriproxyfen induced reduction in pupation about 48.4% and adult emergence about 44.8% and caused some abnormalities of pupae. Last larval instar was more sensitive to JHA in this respect. Maximum pupation disruption occurred at 25ºC and 30ºC in comparison with 35ºC which reduced abnormal pupae up to 19.7%. IGRs were effective in last larval instar at 35 ºC and increased abnormality of adult up to 49.4%. Reproductive potential (egg viability, hatchability) of adults reduced in F1 generation and was 70-90 percent. IGRs have unfavorable effects on biological aspects of larvae therefore, it is possible to use IGRs alone or in conjunction with other pesticides (Fumigants) in integrated control of these pests.