نوع مقاله : مقاله کامل علمی پژوهشی
نویسندگان
1 دانشجوی دکتری هواشناسی کشاورزی، گروه مهندسی آبیاری و آبادانی، دانشکده مهندسی و فناوری کشاورزی، دانشگاه تهران،کرج، ایران
2 استادیار گروه آبیاری، دانشکده مهندسی زراعی، دانشگاه علوم کشاورزی و منابع طبیعی ساری
3 استادیار گروه تکنولوژی و مهندسی چوب، دانشگاه علوم کشاورزی و منابع طبیعی گرگان
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and objectives: Equilibrium moisture content of wood is a condition in which the world has at least an exchange of moisture with the environment. Wood moisture effects on most properties of wood. This feature is a function of relative humidity and temperature so that with increasing relative humidity, EMC increase and also with increasing of temperature EMC is decreased. There are many research regarding wood EMC in different places of the world and Iran. Also the annual trend of EMC was investigated. The objective of this study is trend analysis of EMC in a 25 year period of country.
Materials and methods: For this purpose, EMC was calculated from relative humidity and average annual temperature at 88 meteorological stations. Then by using the non-parametric Mann-Kendall method, the trend of temperature, relative humidity and EMC were analyzed. In this study the variation map of significant coefficients was drawn with the reverse of square distance by weight method regarding climate conditions. Finally the difference of first year amount with the last one and also the difference between first and last decade of the period were investigated in order to compare EMC.
Results: The results showed that in most studied stations the trend of temperature is increasing while the relative humidity and EMC in north beach, plane of Khouzestan and a major part of south-east have negative trend, significantly. The average of EMC in first and last decades changed from 0.35 % to 2.59 % and also between the first and last year of study period changed from 0.33 % in the first to 5.33 %. The main reason for this decline is related to the increasing temperature and decreasing of relative humidity.
Conclusion: With respect to significant negative trend of EMC in North and Northern west forest of Iran and probable intense of this positive trend in the future, it seems that the wood quality and growth rate of forest trees in these regions will be changed. Furthermore, the decreasing trend of EMC, make environment drier for using the wooden furniture and products that need more attention to wood drying process and final EMC of products. Also the negative trend of EMC is an alarm for import wooden products and raw materials and export of wood products.
Conclusion: With respect to significant negative trend of EMC in North and Northern west forest of Iran and probable intense of this positive trend in the future, it seems that the wood quality and growth rate of forest trees in these regions will be changed. Furthermore, the decreasing trend of EMC, make environment drier for using the wooden furniture and products that need more attention to wood drying process and final EMC of products. Also the negative trend of EMC is an alarm for import wooden products and raw materials and export of wood products.
کلیدواژه‌ها [English]
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