Wiedemann Andreas, Marañón-Jiménez Sara, Rebmann Corinna, Herbst Mathias, Cuntz Matthias
Department Computational Hydrosystems, UFZ-Helmholtz Centre for Environmental Research, Permoserstraße 15, 04318 Leipzig, Germany.
Institute for Geological Sciences, Friedrich-Schiller-University Jena, Burgweg 11, 07749 Jena, Germany.
Tree Physiol. 2016 Dec;36(12):1471-1484. doi: 10.1093/treephys/tpw071. Epub 2016 Sep 1.
The insertion of thermal dissipation (TD) sensors on tree stems for sap flux density (SFD) measurements can lead to SFD underestimations due to a wound formation close to the drill hole. However, the wound effect has not been assessed experimentally for this method yet. Here, we propose an empirical approach to investigate the effect of the wound healing on measured sap flux with TD probes. The approach was performed for both, diffuse-porous (Fagus sylvatica (Linnaeus)) and ring-porous (Quercus petraea (Lieblein)) species. Thermal dissipation probes were installed on different dates along the growing season to document the effects of the dynamic wound formation. The trees were cut in autumn and additional sensors were installed in the cut stems, therefore, without potential effects of wound development. A range of water pressures was applied to the stem segments and SFDs were simultaneously measured by TD sensors as well as gravimetrically in the laboratory. The formation of wounds around sensors installed in living tree stems led to underestimation of SFD by 21.4 ± 3 and 47.5 ± 3.8% in beech and oak, respectively. The differences between SFD underestimations of diffuse-porous beech and ring-porous oak were, however, not statistically significant. Sensors with 5-, 11- and 22-week-old wounds also showed no significant differences, which implies that the influence of wound formation on SFD estimates was completed within the first few weeks after perforation. These results were confirmed by time courses of SFD measurements in the field. Field SFD values decreased immediately after sensor installation and reached stable values after ~2 weeks with similar underestimations to the ones observed in the laboratory. We therefore propose a feasible approach to correct directly field observations of SFD for potential underestimations due to the wound effect.
在树干上插入用于测量液流通量密度（SFD）的热消散（TD）传感器，由于钻孔附近形成伤口，可能导致SFD被低估。然而，对于该方法，伤口效应尚未通过实验进行评估。在此，我们提出一种实证方法来研究伤口愈合对使用TD探针测量的液流通量的影响。该方法对散孔材（欧洲山毛榉（林奈））和环孔材（岩生栎（利布林））树种均进行了测试。在生长季节的不同日期安装热消散探针，以记录动态伤口形成的影响。秋季砍伐树木，并在砍伐的树干中安装额外的传感器，因此不存在伤口发育的潜在影响。对茎段施加一系列水压，并通过TD传感器同时测量SFD，并在实验室中采用重量法进行测量。在活树干中安装传感器周围形成的伤口分别导致山毛榉和橡树的SFD低估21.4±3%和47.5±3.8%。然而，散孔材山毛榉和环孔材橡树的SFD低估差异在统计学上并不显著。具有5周、11周和22周龄伤口的传感器也未显示出显著差异，这意味着伤口形成对SFD估计的影响在穿孔后的头几周内就已完成。这些结果在田间SFD测量的时间进程中得到了证实。田间SFD值在传感器安装后立即下降，并在约2周后达到稳定值，低估情况与实验室观察到的相似。因此，我们提出一种可行的方法，直接校正因伤口效应导致的田间SFD潜在低估观测值。
