Exploring the Hidden Age of Alishan's Sacred Trees

The Secrets of the Thousand-year-old Giant Trees
Alishan National Forest Recreation Area is a world-renowned tourist attraction. In addition to its famous sunrise, sea of clouds, forests, cherry blossoms, and steam trains, the Giant Tree Cluster Trail is one of the must-see attractions for visitors. In order to systematically manage the health and safety of giant trees in the recreation area, the Chiayi Forest District Office of Forestry Bureau commissioned a team from National Chiayi University to conduct an investigation. The results of the investigation revealed the grafting characteristic of giant Taiwan Red Cypress Trees that lead to conjoined trees; it was also estimated that the oldest Taiwan Red Cypress tree on the Giant Tree Cluster Trail is 1,515 years old, which is a huge difference from the originally estimated age based on the circumference of the tree.

Scientific Research Reveals the Truth Behind the Sacred Trees
Alishan was once one of the three major forest plantations in Taiwan, and there are many cypress forests in the area. After the logging era, Alishan has now transformed into an important conservation and tourism site. The National Forest Recreation Area includes not only the famous Xianglin Sacred Tree and Thousand-Year Cypress, but also has 36 trees with a diameter at breast height (DBH) of more than 1 meter that line both sides of the Giant Tree Cluster Trail. In addition to the health and safety of the giant trees, the Chiayi Forest District Office also investigated the causes of trunk mutations and the actual age of the giant trees, and commissioned a team from National Chiayi University to conduct a three-year investigation and study. Through field observations, visual assessments, drone photography, tree climbing, core drilling, and testing and analyzing the collected data, it was found that the Taiwan Red Cypress developed shallow roots and wide root plates to adapt to adverse environments, and that newly-grown saplings have a tendency to conjoin with the root plates of neighboring Taiwan Red Cypresses to gain a survival advantage, thus forming the phenomenon of conjoined trees and the continuous cycle of reproduction. The Forestry Bureau asked the team to conduct additional tests using DNA molecular genetics technology to further confirm this speculation, and it was confirmed that the results were consistent with the hypothesis. Therefore, a giant Taiwan Red Cypress, which could take dozens of people to fully encircle, may contain old, middle-aged, and young tree family members all growing together, which has completely overturned our previous knowledge on the age of giant trees.
The Forestry Bureau said that the study also used growth cones to drill out core samples, and analyzed these samples with instruments to estimate the age of the trees. Out of the 44 giant trees in the Alishan National Forest Recreation Area, the most famous Shuishan Giant Tree, Xianglin Sacred Tree, and Thousand-Year Cypress were estimated to be 1,081 years old, 626 years old, and 821 years old, respectively. The oldest Taiwan Red Cypress is Giant Tree No. 2 of the Giant Tree Cluster Trail, which is 1,515 years old, and the youngest is Giant Tree No. 35, which is 116 years old. However, the Forestry Bureau also pointed out that core sampling is restricted by cavities within the giant Taiwan Red Cypress trees due to internal decay and the maximum length of the core that can be drilled from the growth cone. Therefore, it is difficult to estimate the most accurate age of the trees, but this method is still a relatively reliable scientific technique.

Establishing a Health and Safety Mechanism for Giant Trees
To understand the health condition of the giant trees, the research team also examined them in detail by climbing and observing them at close range, and determined their safety classification and monitoring frequency based on this. In addition, the team created a table containing the basic information of each giant tree, which can be used by the staff to monitor and implement giant tree management and provide a safe and high-quality forest recreation environment for the public.

Relationship Between Giant Tree Age and Climate
Another interesting fact of the study was that it also analyzed the effect of past climate change on the growth of the giant Taiwan Red Cypresses. By comparing the growth width of tree rings along with the climate change in Taiwan throughout the past century, it was found that global warming was directly proportional to the variation in tree ring widths. Thus, it is clear that the growth of giant trees has also been affected by global warming.
The Forestry Bureau will share the findings of this study with the public in hopes that when people gaze upon the giant trees and marvel at the wonders of nature, they can also understand the special physiological phenomena that occur during the growth of the Taiwan Red Cypress and the extent of the impact of climate change, thereby increasing their scientific knowledge. The information boards related to the giant trees in the Alishan National Forest Recreation Area will also be updated to provide the public with the latest and most accurate information regarding the giant trees. The Dongshih and Hsinchu Forest District Offices of the Forestry Bureau are also conducting investigations and studies on the giant trees under their jurisdiction.