Canopy transpiration of a semi arid Pinus canariensis forest at a treeline ecotone in two hydrologically contrasting years
Canopy transpiration of a semi arid Pinus canariensis forest at a treeline ecotone in two hydrologically contrasting years
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DOI：
10.1016/j.agrformet.2014.11.008
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发表时间：
2015-02-15
影响因子：
6.2
通讯作者：
Jimenez, Maria S.
中科院分区：
文献类型：
--
作者：
Brito, Patricia;Roberto Lorenzo, J.;Jimenez, Maria S.
鉴于其重要性，森林冠层的蒸腾作用已经在广泛的环境中进行了测量。然而，在地中海气候的树线生态系统中的测量是罕见的，在半干旱气候中更是如此。因此，在本研究中，我们调查的年际变化冠层蒸腾（E-C）的加那利松林位于特内里费岛，加那利群岛，西班牙，那里的气候是典型的半干旱地中海的林线交错带。气象条件和树干液流连续监测两年。在这两年中，研究地点的大气条件是典型的。然而，降水量（P）的年际变化很大的差异。日历年（1 - 12月）2008年P高于2009年，而在相应的水文年（10 - 9月），2008年P显著低于2009年。尽管这两个年份之间的差异P顶部土壤水的可用性几乎耗尽在两个夏天。然而，表层土壤干旱的影响，表现出明显的季节性E-c只清楚地检测到在2008年的值下降到0.02毫米日（-1）在夏季。相比之下，在2009年夏季，E-c率高达1.12毫米日（-1），表明当前一个潮湿时期（12月至4月）的P补充这些储备时，P. canariensis能够从深层土壤中取水。这就指出了在水文年P.气候变化模型预测降水量减少30%以上，在半干旱的树线评估液流研究的重要性。在我们的研究中，只有一个水文干旱年的影响导致严重的水分胁迫。因此，当冬季降雨量低了几年，慢性干旱可能有负面影响的树木和立场蒸腾半干旱的树木。(C)2014爱思唯尔有限公司版权所有。
Given its importance, transpiration of forest canopies has been measured in a wide range of environments. However, measurements in treeline ecosystems with Mediterranean climate are rare more so in semi arid climates. Therefore in the present study we investigate inter-annual variation in canopy transpiration (E-c) of a Pinus canariensis forest located on a treeline ecotone in Tenerife, Canary Islands, Spain, where the climate is typically semi arid Mediterranean. Meteorological conditions and sap flow were continuously monitored during two consecutive years. In both years, atmospheric conditions were typical for the study site. Nevertheless large differences were detected in precipitation (P) with a high inter-annual variability. Calendar year (January-December) P was higher in 2008 than in 2009, while in the corresponding hydrological year (October-September), P was considerably lower in 2008 than in 2009. Despite this difference in P between both years top soil water availability was almost exhausted during both summers. However, the effect of top soil drought, showing a visible seasonality on E-c was only clearly detected in 2008 with values down to 0.02 mm day(-1) during summer. During the summer 2009, in contrast, E-c rates were up to 1.12 mm day(-1) showing that P. canariensis is able to tap water from deep soil layers when P of the previous wet period (October-April) recharged these reserves. This points out the importance of evaluating sap flow studies in semi arid treelines with respect to hydrological year P. Climate change models predict a reduction of more than 30% in precipitation. In our study the effect of only one hydrological dry year resulted in severe water stress. Thus, when winter rainfall is low for a number of years, chronic drought may have negative implications for tree and stand transpiration in semi arid treelines. (C) 2014 Elsevier B.V. All rights reserved.