Intermittent heating for drying of small diameter Larch lumbers is investigated experimentally. The lumbers were dried using an experimental drying schedule. Moisture content (MC) of the lumber was continuously record...Intermittent heating for drying of small diameter Larch lumbers is investigated experimentally. The lumbers were dried using an experimental drying schedule. Moisture content (MC) of the lumber was continuously recorded and final drying defects were examined. The drying curves showed that the drying rate was a constant in the early stage of intermittent heating drying and decreased evidently when the MC was about 18% (intermittent 2h) and 20% (intermittent 6h). The drying quality reached the second (intermittent 2h) and first grade (intermittent 6h) of the Chinese National Standard. The visual drying defects, especially the check extent along grains were reduced with intermittent heating. When the intermittent time increased, the effect was more obvious.展开更多
叶大小-叶脉密度的权衡关系是植物叶经济谱理论的基础,对理解资源竞争条件下植物叶片的物理构建与生理代谢的关系具有重要的意义。该文采用标准化主轴估计(standardized major axis estimation,SMA)的方法,按芨芨草(Achnatherum splende...叶大小-叶脉密度的权衡关系是植物叶经济谱理论的基础,对理解资源竞争条件下植物叶片的物理构建与生理代谢的关系具有重要的意义。该文采用标准化主轴估计(standardized major axis estimation,SMA)的方法,按芨芨草(Achnatherum splendens)株丛密度设置I(>12丛·m^(–2))、II(8–12丛·m^(–2))、III(4–8丛·m^(–2))和IV(<4丛·m^(–2))4个密度梯度,以叶面积和叶干质量分别表示叶大小,对张掖洪泛平原湿地不同密度条件下芨芨草种群的叶大小和叶脉密度的关系进行研究。结果表明:随着芨芨草株丛密度的降低,湿地群落的土壤含水量逐渐减小、土壤电导率逐渐增加,芨芨草的净光合速率(Pn)、蒸腾速率(Tr)和分枝数呈先增大后减小的趋势,叶面积、叶干质量、比叶面积和株高呈逐渐减小趋势、光合有效辐射(PAR)和叶脉密度呈逐渐增加趋势;芨芨草叶大小和叶脉密度在高密度(I)和低密度(IV)样地均呈极显著负相关关系(p<0.01),中密度(II、III)样地二者呈显著负相关关系(p<0.05);叶大小和叶脉密度回归方程的SMA斜率在不同密度样地均显著小于–1(p<0.05),即芨芨草叶大小和叶脉密度呈"此消彼长"的权衡关系。在高密度湿地群落芨芨草倾向于大叶片低叶脉密度的叶片构建模式,在低密度湿地群落选择小叶片高叶脉密度的异速生长模式,体现了密度制约下湿地植物的生物量分配格局和资源利用对策。展开更多
基金Sponsored by Huo Yingdong Fund(Grant No.81022) Sponsored by the Science and Technology Project Foundation of Harbin City( Grant No.2004AFX XJ021).
文摘Intermittent heating for drying of small diameter Larch lumbers is investigated experimentally. The lumbers were dried using an experimental drying schedule. Moisture content (MC) of the lumber was continuously recorded and final drying defects were examined. The drying curves showed that the drying rate was a constant in the early stage of intermittent heating drying and decreased evidently when the MC was about 18% (intermittent 2h) and 20% (intermittent 6h). The drying quality reached the second (intermittent 2h) and first grade (intermittent 6h) of the Chinese National Standard. The visual drying defects, especially the check extent along grains were reduced with intermittent heating. When the intermittent time increased, the effect was more obvious.
文摘叶大小-叶脉密度的权衡关系是植物叶经济谱理论的基础,对理解资源竞争条件下植物叶片的物理构建与生理代谢的关系具有重要的意义。该文采用标准化主轴估计(standardized major axis estimation,SMA)的方法,按芨芨草(Achnatherum splendens)株丛密度设置I(>12丛·m^(–2))、II(8–12丛·m^(–2))、III(4–8丛·m^(–2))和IV(<4丛·m^(–2))4个密度梯度,以叶面积和叶干质量分别表示叶大小,对张掖洪泛平原湿地不同密度条件下芨芨草种群的叶大小和叶脉密度的关系进行研究。结果表明:随着芨芨草株丛密度的降低,湿地群落的土壤含水量逐渐减小、土壤电导率逐渐增加,芨芨草的净光合速率(Pn)、蒸腾速率(Tr)和分枝数呈先增大后减小的趋势,叶面积、叶干质量、比叶面积和株高呈逐渐减小趋势、光合有效辐射(PAR)和叶脉密度呈逐渐增加趋势;芨芨草叶大小和叶脉密度在高密度(I)和低密度(IV)样地均呈极显著负相关关系(p<0.01),中密度(II、III)样地二者呈显著负相关关系(p<0.05);叶大小和叶脉密度回归方程的SMA斜率在不同密度样地均显著小于–1(p<0.05),即芨芨草叶大小和叶脉密度呈"此消彼长"的权衡关系。在高密度湿地群落芨芨草倾向于大叶片低叶脉密度的叶片构建模式,在低密度湿地群落选择小叶片高叶脉密度的异速生长模式,体现了密度制约下湿地植物的生物量分配格局和资源利用对策。
