Laboratorio de Dendrocronología e Historia Ambiental, IANIGLA-CCT CONICET-Mendoza, Av. Ruiz Leal s/n, Mendoza, Argentina.
Section 5.2 Climate Dynamics and Landscape Evolution, GFZ-German Research Centre for Geosciences, Telegrafenberg, Potsdam, Germany.
Tree Physiol. 2019 Apr 1;39(4):661-678. doi: 10.1093/treephys/tpy144.
The carbon isotope composition (δ13C) in tree rings were used to derive the intrinsic water-use efficiency (iWUE) of Araucaria araucana trees of northern Patagonia along a strong precipitation gradient. It is well known that climatic and ontogenetic factors affect growth performance of this species but little is known about their influence in the physiological responses, as iWUE. Thus, the main objective of this study was to assess the physiological reactions of young and adult trees from two open xeric and two moderately dense mesic A. araucana forests to the increases in atmospheric CO2 (Ca) and air temperature during the 20th century, and to relate these responses with radial tree growth. The results indicated that the iWUE and the intercellular CO2 concentration (Ci) increased 33% and 32% in average during the last century, respectively, but carbon isotope discrimination (∆13C) was more variable between sites and age classes. Trees from xeric sites presented greater iWUE and lower ∆13C and Ci values than those from mesic sites. In general, iWUE was strongly related with Ca and was significantly affected by mean summer maximum temperature. ∆13C from mesic sites seemed to be mainly affected by summer maximum temperature, while trees from xeric conditions did not show any influence. Tree age also presented a significant effect on iWUE. Adult trees showed higher iWUE values than young trees, indicating an incidence of the tree age and/or height, mainly in closed mesic forests. Moreover, some trees presented positive relationships between iWUE and radial tree growth, while others presented negative or no relationships, indicating that other factors may negatively influence tree growth. Broadly, the results demonstrate the incidence of climatic, environmental and ontogenetic variability in the tree responses; however, more studies are needed to better understand which forests will be more affected by actual and future climate changes.
树木年轮中的碳同位素组成 (δ13C) 被用来推导巴塔哥尼亚北部强降水梯度下南洋杉树木的内在水分利用效率 (iWUE)。众所周知，气候和个体发育因素会影响该物种的生长表现，但对于其对生理反应（如 iWUE）的影响知之甚少。因此，本研究的主要目的是评估来自两个开阔干旱和两个适度密集湿润南洋杉林的幼树和成年树木对大气 CO2 (Ca) 和空气温度在 20 世纪增加的生理反应，并将这些反应与径向树木生长联系起来。结果表明，在上个世纪，iWUE 和细胞间 CO2 浓度 (Ci) 分别平均增加了 33%和 32%，但碳同位素分馏 (∆13C) 在不同地点和年龄类之间的差异更大。干旱地点的树木比湿润地点的树木具有更高的 iWUE 和更低的 ∆13C 和 Ci 值。一般来说，iWUE 与 Ca 密切相关，并且受到夏季最高温度的显著影响。来自湿润地点的 ∆13C 似乎主要受到夏季最高温度的影响，而来自干旱条件的树木则没有受到任何影响。树龄对 iWUE 也有显著影响。成年树木的 iWUE 值高于幼树，表明树木年龄和/或高度的发生，主要发生在封闭的湿润森林中。此外，一些树木的 iWUE 与径向树木生长之间呈正相关，而另一些树木呈负相关或无相关，表明其他因素可能会对树木生长产生负面影响。总的来说，结果表明了气候、环境和个体发育变异性对树木反应的影响；然而，需要进行更多的研究以更好地了解哪些森林将受到实际和未来气候变化的影响。
