在西班牙加那利群岛特内里费岛的一个半干旱树线交错带，水分利用效率的提高并不能阻止树木生长衰退。
Increased water use efficiency does not prevent growth decline of in a semi-arid treeline ecotone in Tenerife, Canary Islands (Spain).
作者信息
Brito Patricia, Grams Thorsten E E, Matysssek Rainer, Jimenez Maria S, Gonzalez-Rodríguez Agueda M, Oberhuber Walter, Wieser Gerhard
机构信息
Department of Botany, Ecology and Plant Physiology, Universidad de La Laguna (ULL), C/Astrofísico Francisco Sánchez s/n, E-38207 La Laguna, Tenerife, Spain.
Ecophysiology of Plants, Department of Ecology and Ecosystem Management, Technische Universität München, Von-Carlowitz-Platz 2, 85354 Freising, Germany.
出版信息
Ann For Sci. 2016 Sep;73(3):741-749. doi: 10.1007/s13595-016-0562-5. Epub 2016 Jun 7.
KEY MESSAGE
Intrinsic water-use efficiency of (Sweet Spreng.) growing at a semi-arid treeline has increased during the past 37 years. Tree-ring width by contrast has declined, likely caused by reduced stomatal conductance due to increasing aridity.
CONTEXT
Rising atmospheric CO concentration ( ) has been related to tree growth enhancement accompanied by increasing intrinsic water-use-efficiency (iWUE). Nevertheless, the extent of rising on long-term changes in iWUE and growth has remained poorly understood to date in Mediterranean treeline ecosystems.
AIMS
This study aimed to examine radial growth and physiological responses of in relation to rising and increasing aridity at treeline in Tenerife, Canary Islands, Spain.
METHODS
We evaluated temporal changes in secondary growth (tree-ring width; TRW) and tree ring stable C isotope signature for assessing iWUE from 1975 through 2011.
RESULTS
Precipitation was the main factor controlling secondary growth. Over the last 36 years showed a decline in TRW at enhanced iWUE, likely caused by reduced stomatal conductance due to increasing aridity.
CONCLUSION
Our results indicate that increasing aridity has overridden the potential CO fertilization on tree growth of at its upper distribution limit.
关键信息
在过去37年里，生长于半干旱树线地区的（甜斯普伦格）的内在水分利用效率有所提高。相比之下，年轮宽度有所下降，这可能是由于干旱加剧导致气孔导度降低所致。
背景
大气中二氧化碳浓度（）升高与树木生长增强以及内在水分利用效率（iWUE）增加有关。然而，在地中海树线生态系统中，迄今为止，二氧化碳浓度升高对iWUE和生长长期变化的影响程度仍知之甚少。
目的
本研究旨在探讨西班牙加那利群岛特内里费岛树线处，与二氧化碳浓度升高和干旱加剧相关的（甜斯普伦格）的径向生长和生理反应。
方法
我们评估了1975年至2011年期间次生生长（年轮宽度；TRW）的时间变化以及树木年轮稳定碳同位素特征，以评估iWUE。
结果
降水是控制次生生长的主要因素。在过去36年里，（甜斯普伦格）在iWUE提高的情况下，TRW却出现下降，这可能是由于干旱加剧导致气孔导度降低所致。
结论
我们的结果表明，在其分布上限处，干旱加剧已超过了潜在的二氧化碳施肥对（甜斯普伦格）树木生长的影响。
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