Fog reduces transpiration in tree species of the Canarian relict heath-laurel cloud forest (Garajonay National Park, Spain).
Fog reduces transpiration in tree species of the Canarian relict heath-laurel cloud forest (Garajonay National Park, Spain).
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DOI：
10.1093/treephys/tpn043
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发表时间：
2009-04
期刊：
影响因子：
4
通讯作者：
A. Ritter;C. Regalado;G. Aschan
中科院分区：
文献类型：
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作者：
A. Ritter;C. Regalado;G. Aschan
尽管人们普遍认为雾水对于北大西洋马卡罗尼西亚群岛这一残余古生态系统的生存和分布很重要，但雾在加那利群岛常绿石南月桂“laurisilva”云林中的生态生理作用尚未得到明确证明。为了确定雾在该生态系统中的作用，我们将使用 Granier 散热探针获得的石南月桂树种的直接蒸腾测量值与在加拉霍奈国家公园（西班牙加那利群岛戈梅拉岛）的 43.7 公顷流域进行的微气象和人工雾收集测量值相结合，历时 10 个月。有雾条件下，环境温度中位数为 7 至 15 摄氏度，而无雾期间的环境温度较高，为 9 至 21 摄氏度。此外，在收集雾水期间，全球太阳辐射值与无雾条件下的太阳辐射值呈线性相关（r2=0.831），因此雾的中值辐射减少了 75+/-1%。雾事件极大地降低了树木的中位日蒸腾量，其速率比无雾条件下的蒸腾速率低约 30 倍，并且接近所研究的两个物种（针状叶 Erica arborea L. 和阔叶杨梅 Ait.）的夜间速率。雾造成的蒸腾量大幅减少与一天中的时间、树木大小、物种以及微气象状态无关，无论是在整个 10 个月测量期间的中值基础上还是在累积条件下。我们的结论是，雾水滴在石南树种上的湍流沉积可能被视为一种局部水文现象，对高海拔暴露在风中的乔木树很重要，而云浸带提供的凉爽、湿润和遮荫的微环境代表了一种大规模效应，这对于减少过度用水的树木的蒸腾失水至关重要，例如那些过度用水的树木。 “劳里斯尔瓦”。
The ecophysiologic role of fog in the evergreen heath-laurel 'laurisilva' cloud forests of the Canary Islands has not been unequivocally demonstrated, although it is generally assumed that fog water is important for the survival and the distribution of this relict paleoecosystem of the North Atlantic Macaronesian archipelagos. To determine the role of fog in this ecosystem, we combined direct transpiration measurements of heath-laurel tree species, obtained with Granier's heat dissipation probes, with micrometeorological and artificial fog collection measurements carried out in a 43.7-ha watershed located in the Garajonay National Park (La Gomera, Canary Islands, Spain) over a 10-month period. Median ambient temperature spanned from 7 to 15 degrees C under foggy conditions whereas higher values, ranging from 9 to 21 degrees C, were registered during fog-free periods. Additionally, during the periods when fog water was collected, global solar radiation values were linearly related (r2=0.831) to those under fog-free conditions, such that there was a 75+/-1% reduction in median radiation in response to fog. Fog events greatly reduced median diurnal tree transpiration, with rates about 30 times lower than that during fog-free conditions and approximating the nighttime rates in both species studied (the needle-like leaf Erica arborea L. and the broadleaf Myrica faya Ait.). This large decrease in transpiration in response to fog was independent of the time of the day, tree size and species and micrometeorological status, both when expressed on a median basis and in cumulative terms for the entire 10-month measuring period. We conclude that, in contrast to the turbulent deposition of fog water droplets on the heath-laurel species, which may be regarded as a localized hydrological phenomenon that is important for high-altitude wind-exposed E. arborea trees, the cooler, wetter and shaded microenvironment provided by the cloud immersion belt represents a large-scale effect that is crucial for reducing the transpirational water loss of trees that have profligate water use, such as those of the 'laurisilva'.