Wieser Gerhard, Oberhuber Walter, Gruber Andreas, Leo Marco, Matyssek Rainer, Grams Thorsten Erhard Edgar
Department of Alpine Timberline Ecophysiology, Federal Research and Training Centre for Forests, Natural Hazards and Landscape Innsbruck, Austria.
Institute of Botany, Leopold-Franzens-Universität Innsbruck Innsbruck, Austria.
Front Plant Sci. 2016 Jun 7;7:799. doi: 10.3389/fpls.2016.00799. eCollection 2016.
The ability of treeline associated conifers in the Central Alps to cope with recent climate warming and increasing CO2 concentration is still poorly understood. We determined tree ring stable carbon and oxygen isotope ratios of Pinus cembra, Picea abies, and Larix decidua trees from 1975 to 2010. Stable isotope ratios were compared with leaf level gas exchange measurements carried out in situ between 1979 and 2007. Results indicate that tree ring derived intrinsic water-use efficiency (iWUE) of P. cembra, P. abies and L. decidua remained constant during the last 36 years despite climate warming and rising atmospheric CO2. Temporal patterns in Δ(13)C and Δ(18)O mirrored leaf level gas exchange assessments, suggesting parallel increases of CO2-fixation and stomatal conductance of treeline conifer species. As at the study site soil water availability was not a limiting factor iWUE remained largely stable throughout the study period. The stability in iWUE was accompanied by an increase in basal area increment (BAI) suggesting that treeline trees benefit from both recent climate warming and CO2 fertilization. Finally, our results suggest that iWUE may not change species composition at treeline in the Austrian Alps due to similar ecophysiological responses to climatic changes of the three sympatric study species.
中阿尔卑斯山树线附近的针叶树应对近期气候变暖和二氧化碳浓度增加的能力仍知之甚少。我们测定了1975年至2010年欧洲刺柏、欧洲云杉和欧洲落叶松的树木年轮稳定碳和氧同位素比率。将稳定同位素比率与1979年至2007年在原地进行的叶片水平气体交换测量结果进行了比较。结果表明，尽管气候变暖和大气二氧化碳浓度上升，但在过去36年中，欧洲刺柏、欧洲云杉和欧洲落叶松树木年轮衍生的内在水分利用效率（iWUE）保持不变。δ¹³C和δ¹⁸O的时间模式反映了叶片水平的气体交换评估结果，表明树线针叶树种的二氧化碳固定和气孔导度同时增加。由于在研究地点土壤水分供应不是限制因素，iWUE在整个研究期间基本保持稳定。iWUE的稳定性伴随着基部面积增量（BAI）的增加，这表明树线树木受益于近期的气候变暖和二氧化碳施肥效应。最后，我们的结果表明，由于三种同域分布的研究树种对气候变化具有相似的生理生态响应，iWUE可能不会改变奥地利阿尔卑斯山树线处的物种组成。
