Fundamental study for the establishment of dendrochronology in tropical trees

在热带树木中，据说生长和/或年轮被认为不如温带树木那么明显。在本研究项目中，对木材形成的季节性特征进行了研究，以获得与生长和/或年轮相关的信息，并特别参考水分条件。在泰国和马来西亚选择了天然林和种植园林作为研究地点。本摘要报告了泰国的结果。实验选用了4种植物：坡垒、铁坡垒、赤桉和柚木。在木材形成研究中，进行了带式测树仪的设置、钉扎试验和包括形成层在内的木块的采集。为了调查水分条件，叶水势以及土壤和韧皮部/木质部水分含量进行了测定。4种植物的生长轮边界形成于雨季末至旱季初，但在详细观察中发现，即使在雨季降水量少的情况下，生长轮边界的形成也较弱，水分亏缺对形成层活动的影响较为敏感，导致生长轮边界的形成。在”H“的比较中。odorata和H. ferrea，飞机草的叶水势高于飞机草。一年四季都是铁。在前木材形成开始后，雨季开始。在后者，它推迟了大约2个月。这可能是由于干旱季节严重的水分胁迫使叶片水势的恢复延迟所致。在钉扎实验中，伤口组织在切线方向上的范围比估计的要宽。在今后的实地调查中，应重新考虑这一方法。

In tropical trees it is said that growth and/or annual rings are considered to be not so distinct as those of temperate trees. In this research project seasonal characteristics of wood formation were studied to get information related to growth and/or annual rings with special reference to water conditions. Natural and plantation forests were selected in Thailand and Malaysia as the research sites. Results of Thailand are reported in this abstract. Four species, Hopea odorata, Hopea ferrea, Eucalyptus camaldulensis and Tectona grandis were used. For the wood formation study, setting of band-type dendrometer, pinning experiment and collection of wood blocks including cambium were carried out. To investigate water conditions, leaf water potential as well as soil and phloem/xylem moisture contents were measured. The growth ring boundaries were formed in the end of rainy season to early of dry season in 4 species, In detailed observation, however, weak growth ring boundary was formed even in the rainy season if it has low precipitation, Water deficit was considered to affect sensitively cambial activity resulted in the formation of growth ring boundary. In the comparison o」 H. odorata and H. ferrea, leaf water potential of H odorata was higher than that of H. ferrea all through the year. In the former wood formation started following the start of rainy season. In the latter it delayed about 2 months. It was considered because of the delay of the recovery of leaf water potential in the latter due to the severe water stressed condition in the dry season. In the pinning experiment, the extent of wound tissue in the tangential direction was wider than it was estimated. Methodologically it should be reconsidered in the future field investigations.