Interspecific variation in nighttime transpiration and stomatal conductance in a mixed New England deciduous forest
Interspecific variation in nighttime transpiration and stomatal conductance in a mixed New England deciduous forest
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DOI：
10.1093/treephys/26.4.411
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发表时间：
2006-04-01
期刊：
影响因子：
4
通讯作者：
Phillips, NG
中科院分区：
文献类型：
--
作者：
Daley, MJ;Phillips, NG
一般认为，夜间气孔因光合有效辐射的缺乏而关闭时，蒸腾作用是微不足道的。然而，越来越多的证据表明，一些物种的气孔在夜间保持开放，如果有足够的环境驱动力，这将允许夜间蒸腾。我们研究了夜间用水共发生的物种在混合落叶林在哈佛森林，MA，使用整树和叶水平的测量。采用Granier型液流传感器连续监测纸桦（Betula papyrifera Marsh.）红栎（Quercus rubra L.）和红枫（Acer rubrum L.）。进行了分析，其中夜间水通量可以划分为内部水存储和蒸腾之间的再填充。大量的夜间树液流量，观察到在所有的物种，这种流量大部分是由于枯竭的水存储的再填充。然而，在纸皮桦，夜间树液流量经常超过补给估计。在生长季中，白桦树夜间蒸腾作用占日液流总量的10%以上。夜间液流超过8%的红橡树和2%的红枫，但这种流量主要与补给。在蒸汽压赤字升高的夜晚，纸桦的树液通量在夜间持续存在，而红橡树和红枫的树液通量在夜间达到零。在一个蒸汽压亏缺升高的夜晚，对叶片水平气体交换的测量表明，纸皮桦的气孔导度仅下降了25%，而红橡树和红枫的气孔导度接近于零。这项研究强调了共同发生的物种对液流的生理生态控制的差异。纸桦是一种生长迅速、不耐阴性的物种，其继承地位比红橡和红枫更早。通过夜间蒸腾冒着水分流失的风险可能会为纸桦提供生态优势，使该物种能够最大限度地发挥光合作用并支持快速生长。夜间蒸腾也可能是一种机制，提供氧气呼吸细胞在深边材的纸桦树。
Transpiration is generally assumed to be insignificant at night when stomata close in response to the lack of photosynthetically active radiation. However, there is increasing evidence that the stomata of some species remain open at night, which would allow for nighttime transpiration if there were a sufficient environmental driving force. We examined nighttime water use in co-occurring species in a mixed deciduous stand at Harvard Forest, MA, using whole-tree and leaf-level measurements. Diurnal whole-tree water use was monitored continuously with Granier-style sap flux sensors in paper birch (Betula papyrifera Marsh.), red oak (Quercus rubra L.) and red maple (Acer rubrum L.). An analysis was conducted in which nighttime water flux could be partitioned between refilling of internal water stores and transpiration. Substantial nighttime sap flux was observed in all species and much of this flux was attributed to the refilling of depleted water stores. However, in paper birch, nighttime sap flux frequently exceeded recharge estimates. Over 10% of the total daily sap flux during the growing season was due to transpiration at night in paper birch. Nighttime sap flux was over 8% of the total daily flux in red oak and 2% in red maple; however, this flux was mainly associated with recharge. On nights with elevated vapor pressure deficit, sap flux continued through the night in paper birch, whereas it reached zero during the night in red oak and red maple. Measurements of leaf-level gas exchange on a night with elevated vapor pressure deficit showed stomata] conductance dropping by only 25% in paper birch, while approaching zero in red oak and red maple. The study highlighted differences in ecophysiological controls on sap flux exerted by co-occurring species. Paper birch is a fast-growing, shade-intolerant species with an earlier successional status than red oak and red maple. Risking water loss through nighttime transpiration may provide paper birch with an ecological advantage by enabling the species to maximize photosynthesis and support rapid growth. Nighttime transpiration may also be a mechanism for delivering oxygen to respiring cells in the deep sapwood of paper birch.