Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Prague, Czech Republic.
Department of Forest Harvesting, Logistics and Ameliorations, Faculty of Forestry, Technical University in Zvolen, Zvolen, Slovakia.
PLoS One. 2020 Mar 10;15(3):e0230082. doi: 10.1371/journal.pone.0230082. eCollection 2020.
Annual trunk increments are essential for short-term analyses of the response of trees to various factors. For instance, based on annual trunk increments, it is possible to develop and calibrate forest growth models. We investigated the possibility of estimating annual trunk increments from the terrestrial structure from motion (SfM) photogrammetry. Obtaining the annual trunk increments of mature trees is challenging due to the relatively small growth of trunks within one year. In our experiment, annual trunk increments were obtained by two conventional methods: measuring tape (perimeter increment) at heights of 0.8, 1.3, and 1.8 m on the trunk and increment borer (diameter increment) at a height of 1.3 m on the trunk. The following tree species were investigated: Fagus sylvatica L. (beech), Quercus petraea (Matt.) Liebl. (oak), Picea abies (L.) H. Karst (spruce), and Abies alba Mill (fir). The annual trunk increments ranged from 0.9 cm to 2.4 cm (tape/perimeter) and from 0.7 mm to 3.1 mm (borer/diameter). The data were collected before- and after-vegetation season, besides the data collection increment borer. When the estimated perimeters from the terrestrial SfM photogrammetry were compared to those obtained using the measuring tape, the root mean square error (RMSE) was 0.25-1.33 cm. The relative RMSE did not exceed 1% for all tree species. No statistically significant differences were found between the annual trunk increments obtained using the measuring tape and terrestrial SfM photogrammetry for beech, spruce, and fir. Only in the case of oak, the difference was statistically significant. Furthermore, the correlation coefficient between the annual trunk increments collected using the increment borer and those derived from terrestrial SfM photogrammetry was positive and equal to 0.6501. Terrestrial SfM photogrammetry is a hardware low-demanding technique that provides accurate three-dimensional data that can, based on our results, even detect small temporal tree trunk changes.
年干径生长量对于树木对各种因素响应的短期分析至关重要。例如，基于年干径生长量，可以开发和校准森林生长模型。我们研究了从地面结构光（SfM）摄影测量估算年干径生长量的可能性。由于一年内树干的生长相对较小，因此获取成熟树木的年干径生长量具有挑战性。在我们的实验中，通过两种常规方法获得年干径生长量：在树干 0.8、1.3 和 1.8 m 高度处使用测径器（周长增量）和在树干 1.3 m 高度处使用生长锥（直径增量）。研究了以下树种：欧洲山毛榉（山毛榉）、栓皮栎（栎木）、欧洲云杉（云杉）和银枞（枞树）。年干径生长量范围为 0.9 厘米至 2.4 厘米（测径器/周长）和 0.7 毫米至 3.1 毫米（生长锥/直径）。除了生长锥数据采集外，还在植被季前和季后采集数据。当将地面 SfM 摄影测量估算的周长与使用测径器获得的周长进行比较时，均方根误差（RMSE）为 0.25-1.33 厘米。对于所有树种，相对 RMSE 均未超过 1%。在山毛榉、云杉和枞树中，使用测径器和地面 SfM 摄影测量获得的年干径生长量之间没有发现统计学上的显著差异。只有在栎木的情况下，差异才具有统计学意义。此外，使用生长锥采集的年干径生长量与从地面 SfM 摄影测量获得的年干径生长量之间的相关系数为正，等于 0.6501。地面 SfM 摄影测量是一种硬件要求低的技术，可提供准确的三维数据，根据我们的结果，甚至可以检测到树木树干的微小时间变化。
