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Factors affecting diurnal stem contraction in young Douglas-fir

机译:影响幼小道格拉斯冷杉昼间茎干收缩的因素

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a- Diurnal radial stem contraction was measured in a young Douglas-fir plantation. a- Vapor pressure deficit and solar radiation predicted the magnitude of diurnal contraction. a- Soil water availability was high, and soil water content was unrelated to contraction. a- Continuous diameter measurements provide valuable information on tree water balance. Diurnal fluctuation in a tree's stem diameter is a function of daily growth and of the tree's water balance, as water is temporarily stored in the relatively elastic outer cambial and phloem tissues. On a very productive site in southwestern Washington, U.S.A., we used recording dendrometers to monitor stem diameter fluctuations of Douglas-fir at plantation ages 7 and 8 and related the fluctuations to environmental variables measured on-site. Growing-season diurnal stem contraction (DSC) averaged 0.21% of stem diameter, while dormant-season DSC averaged 0.03% of stem diameter. Maximum daily stem diameter generally occurred between 7:00 and 9:00 Pacific Standard Time (PST) and minimum stem diameter occurred between 17:00 and 20:00PST. Diurnal stem contraction during the growing season was predicted by a model that included vapor pressure deficit and solar radiation (adjusted R 2 =0.84). A similar model predicted DSC during the dormant season with an adjusted R 2 =0.26. Soil water availability was high, and soil water content was not correlated with DSC. On four of the coldest winter days (mean daytime air temperature <0A degree C), large decreases in stem diameter were observed. Recording dendrometers, used for continuous diameter measurements throughout the growing season, have the potential to provide important information not only on tree growth but also on a tree's water balance.
机译:在幼小的道格拉斯冷杉人工林中测量了昼夜radial茎收缩。 a-蒸气压不足和太阳辐射预测了日收缩的大小。 a-土壤水分利用率高,土壤水分与收缩无关。 a-连续的直径测量可提供有关树木水平衡的有价值的信息。树木的茎直径的日变化是日常生长和树木水平衡的函数,因为水被暂时存储在相对较弹性的冈比亚韧皮部和韧皮部组织中。在美国华盛顿州西南部一个生产力很高的站点上,我们使用了记录测速仪来监测花旗松在7和8岁时的茎直径波动并将其与现场测量的环境变量相关联。生长季节昼间茎干收缩(DSC)平均占茎直径的0.21%,而休眠季节DSC平均占茎直径的0.03%。每日最大烟梗直径通常在太平洋标准时间(PST)7:00至9:00之间发生,而最小烟梗直径则在太平洋标准时间17:00至20:00 PST之间发生。通过包括蒸气压不足和太阳辐射(调整后的R 2 = 0.84)的模型预测了生长期的日干收缩。相似的模型预测了休眠期的DSC,调整后的R 2 = 0.26。土壤水分利用率高,土壤含水量与DSC无关。在最冷的四个冬季(平均白天气温<0A摄氏度)中,观察到茎直径大幅度减小。记录式测树仪用于整个生长季节的连续直径测量,不仅有可能提供有关树木生长以及树木水分平衡的重要信息。

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