Transpiration and annual water balance of Aleppo pine in a semiarid region: Implications for forest management
Transpiration and annual water balance of Aleppo pine in a semiarid region: Implications for forest management
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DOI：
10.1016/j.foreco.2013.03.003
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发表时间：
2013-06
影响因子：
3.7
通讯作者：
E. Ungar;E. Rotenberg;N. Raz‐Yaseef;S. Cohen;D. Yakir;G. Schiller
中科院分区：
文献类型：
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作者：
E. Ungar;E. Rotenberg;N. Raz‐Yaseef;S. Cohen;D. Yakir;G. Schiller
蒸腾作用是了解干旱地区人工林生态生理的基础数据，对构建生态系统水平的水分平衡至关重要。目前的目的是：(1)测量旱地halepensis林的日蒸腾量。（阿勒颇松）森林，并研究其与土壤含水量和蒸发需求等环境条件的关系；（ii）确定生态系统的季节和年度水量平衡；（三）探讨在日益干旱的气候变化情景下的管理意义。这项研究是在以色列半干旱的内盖夫北部的Yatir森林（300树沙−1）进行的，连续三年（从2003/4年开始），降雨量(R)分别为231、334和224毫米，最后一次被指定为干旱，因为两次主要降雨之间的干旱期相对较长。用热脉冲法测量树木蒸腾，并将测量值升级到林冠层水平。获得了生态系统日蒸散量（ET）、土壤和林下植被日蒸散量(E)的独立估计值。日冠层蒸腾速率(T)变化范围为0.1 ~ 1.6mmd−1，在雨季表现出高度动态和不规则的模式。对于两个非干旱年，T的大部分变化可归因于以下简单关系。当土壤含水量(SWC)≥0.15m3m−3时，土壤水分的主要驱动因子是SWC；T对SWC的回归得到了极显著的二次关系，表明在约0.12m3m−3的SWC以下几乎没有响应，而在其以上则有陡峭的线性响应。对于SWC >0.15m3m−3，潜在蒸散发（PET）是最重要的；在雨季（215d），平均而言，累积ET （201mm）占0.76 R (R=263mm)，累积T (116mm；范围103-126mm) -累积ET的独立估算分量-占0.45 R，累积E为70mm。在年基础上，总蒸散损失约等于R，其中58%通过树木排出系统，39%通过土壤和林下植被排出系统。水平衡数据结合关于树木最小蒸腾的假设，得出了可持续森林密度的第一个近似值。该方法表明，为了在年降雨量分别为200或150毫米的情况下保持可持续发展，Yatir森林应减薄至250或190树的林分。
Transpiration is a fundamental datum in understanding the ecophysiology of planted forests in dry regions and is central to the construction of an ecosystem-level water balance. The present aims were: (i) to measure daily transpiration in a dryland Pinus halepensis Mill. (Aleppo pine) forest and to examine its relationship to environmental conditions such as soil water content and evaporative demand; (ii) to determine the seasonal and annual water balances of the ecosystem; and (iii) to explore management implications in the context of a climate-change scenario of increasing aridity. The study was conducted in the Yatir forest (300treesha−1) in Israel’s semiarid northern Negev, during three consecutive years (starting 2003/4) in which rainfall (R) was 231, 334 and 224mm, the last designated a drought because of relatively long dry spells between major rain events. Tree transpiration was measured by the heat-pulse method and values were upscaled to the forest canopy level. Independent estimates were obtained for daily ecosystem-level evapotranspiration (ET), and soil and understory vegetation evapotranspiration (E). Daily canopy-level transpiration rate (T) ranged from 0.1 to 1.6mmd−1and showed a highly dynamic and irregular pattern during the rainy season. For the two non-drought years a large part of the variation in T could be attributed to the following simple relationships. When soil water content (SWC) ⩽0.15m3m−3, the primary driver of T was SWC; regression of T on SWC yielded highly significant quadratic relationships indicating little response below SWC of approximately 0.12m3m−3, and a steep linear response above it. For SWC >0.15m3m−3, potential evapotranspiration (PET) was of paramount importance; quadratic regression of T on PET yielded highly significant relationships and explained a high proportion of the variance in T. During the wet season (215d), on average, cumulative ET (201mm) accounted for 0.76 R (R=263mm) and cumulative T (116mm; range 103–126mm) – an independently estimated component of cumulative ET – accounted for 0.45 R. Cumulative E was 70mm. On an annual basis, total evapotranspiration losses were approximately equal to R, with 58% exiting the system via the trees and 39% via soil and undergrowth vegetation. Water balance data combined with assumptions regarding tree minimum transpiration led to a first approximation of sustainable forest density. This approach indicated that the Yatir forest should be thinned to stands of 250 or 190treesha−1in order to remain sustainable under annual rainfall regimes of 200 or 150mm, respectively.