Oberhuber Walter, Sehrt Melissa, Kitz Florian
Department of Botany, Leopold-Franzens-University of Innsbruck, Sternwartestrasse 15, A-6020 Innsbruck, Austria.
Department of Ecology, Leopold-Franzens-University of Innsbruck, Sternwartestrasse 15, A-6020 Innsbruck, Austria.
Agric For Meteorol. 2020 Aug 15;290:108026. doi: 10.1016/j.agrformet.2020.108026. Epub 2020 May 29.
Time series of stem diameter variations (SDVs) recorded by dendrometers are composed of two components: (i) irreversible radial stem growth and (ii) reversible stem shrinking and swelling caused by dynamics in water storage in elastic tissues outside the cambium. However, SDVs measured over dead outer bark (periderm) could also be affected by absorption and evaporation of water from remaining dead bark layers after smoothing the stem surface to properly mount dendrometers. Therefore, the focus of this study was to determine the influence of hygroscopicity of a thin dead outer bark layer on the reversible component of dendrometer records of Scots pine () under field conditions. To accomplish this, SDVs deduced from dendrometers mounted over dead outer bark were compared among living and dead saplings and mature trees. Results revealed that dead trees showed high synchronicity in reversible daily SDVs compared to living trees throughout several growing seasons (mean Pearson correlation coefficient () = 0.844 among saplings and = 0.902 among mature trees, respectively; <0.001). Furthermore, diurnal and long-term SDVs closely followed changes in relative air humidity (RH) in living and dead trees. A multiple linear regression analysis of environmental influence on SDVs in dead and living trees revealed that the most important predictor of daily SDVs was RH (relative importance 64 %). Hence, results indicate that dendrometers mounted over dead outer bark with a thickness of <4 mm record hygroscopic shrinking and swelling of the bark tissue, which can amplify fluctuations in whole-tree water status. To conclude, hygroscopic processes must be taken into account when extracting intra-annual radial growth, determining environmental drivers of SDVs, and evaluating changes in tree water status from SDVs recorded by dendrometers, which were mounted over even thin dead outer bark layers.
由测树仪记录的树干直径变化（SDV）时间序列由两个部分组成：（i）不可逆的径向树干生长，以及（ii）形成层外部弹性组织中水分储存动态引起的可逆树干收缩和膨胀。然而，在对树干表面进行平滑处理以正确安装测树仪后，在枯死的外层树皮（周皮）上测量的SDV也可能受到剩余枯死树皮层水分吸收和蒸发的影响。因此，本研究的重点是确定薄枯死外层树皮的吸湿性对田间条件下苏格兰松（）测树仪记录的可逆部分的影响。为了实现这一目标，比较了安装在枯死外层树皮上的测树仪得出的SDV在活树苗、死树苗和成熟树木之间的差异。结果表明，在几个生长季节中，与活树相比，死树在每日可逆SDV上表现出高度同步性（树苗之间的平均皮尔逊相关系数（）=0.844，成熟树木之间的=0.902；<0.001）。此外，活树和死树的昼夜和长期SDV都紧密跟随相对空气湿度（RH）的变化。对活树和死树中环境对SDV影响的多元线性回归分析表明，每日SDV的最重要预测因子是RH（相对重要性64%）。因此，结果表明，安装在厚度<4毫米的枯死外层树皮上的测树仪记录了树皮组织的吸湿收缩和膨胀，这会放大整棵树水分状况的波动。总之，在从安装在即使是薄枯死外层树皮上的测树仪记录中提取年内径向生长、确定SDV的环境驱动因素以及评估树木水分状况变化时，必须考虑吸湿过程。
