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41.
Majid KIAEI 《中国林学(英文版)》2012,14(3):229-234
This study examined the effect of site and elevation on the oven-dry density and volumetric shrinkage of hornbeam (Carpinus betulus) wood.For this purpose,45 normal hornbeam trees from three different sites (Mazandaran,Guilan and Golestan) at three elevations,300 m (low elevation),700 m (intermediate elevation) and 1100 m (high elevation) from natural forest in northern Iran were selected.Disks were cut at breast height from mature wood and test samples were prepared to determine physical properties,i.e.,wood density and volumetric shrinkage.The results show that there are significant differences between site and elevation on these physical properties of wood.The interaction effects between site × elevation on wood density and volumetric shrinkage were also statistically significant.At any fixed site,wood density and volumetric shrinkage increased with elevation.As well,their values at Guilan were higher than those at the other two sites.The relationship between wood density and volumetric shrinkage was determined by simple regression equations.Strong,positive relationships between wood density and volumetric shrinkage at each site were found.Again,these were stronger at the Guilan site than at the other two sites.Given a fixed site,the correlation at high elevation was stronger than at the other two elevations. 相似文献
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<正> 当前,养鸡业进入微利时代,为提高经济效益,各养殖场千方百计寻找降低生产成本、增加生产效益的措施。种蛋入孵率是衡量种鸡生产成绩好坏的一个重要指标,种蛋入孵率与种蛋质量(即蛋形指数和蛋壳质量)密切相关,它与种蛋的受精率、孵化率和鸡苗质量均有着内在的正相关性。因此,研究影响种蛋入孵率的因素及改善措施,对种鸡场提高经济效益具有十分重要的意义。一、影响因素种蛋入孵率与种蛋质量密切相关,而种蛋质量通常受多种因素影响,如品种、周龄、环境条件、饲料营养、应 相似文献
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种公牛阴囊周径与其体重、体高间的相关性研究 总被引:1,自引:0,他引:1
测定了山东银香伟业集团中大种公牛站1998~2003年引进的西门塔尔(XM)、盖普威(德国黄牛GL)、利木赞(LM)、荷斯坦(HS)四个品种62头种公牛阴囊周径(SC)、体高,体重,并对SC与体重、体高、年龄进行相关性分析.结果表明:西门塔尔、盖普威(德国黄牛)、利木赞、荷斯坦这四个品种的SC与体重、体高呈正相关,并且同品种不同年龄阶段SC与体重、体高呈高度正相关,同品种不同年龄阶段以及不同品种的同一年龄阶段,SC表现为差异显著(P<0.05).为引进牛品种的选育工作提供依据. 相似文献
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通常,亲鱼与所产生的后代数量在一定水平之下呈正相关,如果资源急激持续地增加或减少,其正常的亲子关系就不复存在,而把握其关系的关键在于成活条件。也就是说当某一年份成活率特别好或特别坏,或者年成活力持续恶化的情况下应推倒这种关系。因此,当资源呈现到某一水平以后的正常的亲子数量的正相关就会变为负相关。 相似文献
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Five molecular related indexes: MOL, SIM, d2, H0and PIC of 15 turbot parent pairs were estimated by using 10 SSR loci, which were used in correlation analysis with growth traits, DIL and DIW, of family filial from those 15 parent pairs.DIL and DIW were regressed on the MOL, SIM, d2, H0and PIC. Results showed MOL of five SSR loci(12, 17, 24, 81 and 85) and SIM of five loci(17, 21, 24, 81and 85) all shared significant positive correlation with DIL(r=0.482, P=0.035 and r=0.479, P=0.035, respectively); H0of six SSR loci(11, 17, 21, 24, 26 and 85) had significant positive correlation with DIW(r=0.551, P=0.017); PIC of two SSR loci(9and 26) had significant positive(r=0.519, P=0.024) correlation with DIL, while that and of four loci(17, 24, 27 and 85) had significant negative correlation(r=-0.519,P=0.024), with DIL. This present study suggested that filial growth expression could be predicted by using molecular related indexes in turbot breeding practice, and the accuracy of prediction depends on more SSR loci, especially associated with QTL. 相似文献
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武夷山不同海拔高度森林土壤呼吸初步研究 总被引:3,自引:0,他引:3
采用Li-cor6400、Li-8100和碱呼吸法初步测定和分析了中亚热带武夷山不同海拔高度、森林植被下的土壤呼吸.结果表明:(1)随着海拔高度的递增,土壤呼吸的速率下降.(2)土壤温度与土壤呼吸呈明显的正相关.(3)土壤湿度对土壤呼吸有一定的影响.由于影响土壤呼吸的因子较多,且土壤呼吸在空间和时间的变异较大,所得结果需在以后的研究中进一步验证. 相似文献