Ancient trees are silent witnesses to the changes that have occurred in the world around them. Having survived for millennia, they are rare, and in China, these ancient giants are primarily found in the harsh environment of the Qinghai-Xizang Plateau.

　　Surviving in extreme weather

　　The question of why the Qinghai-Xizang Plateau, with its extreme conditions, is home to many ancient trees has intrigued scientists and the public for a long time. Professor Zhang Qibing from the Institute of Botany, Chinese Academy of Sciences, has shed light on this phenomenon. According to mainstream beliefs, trees living under certain adverse conditions tend to have longer lifespans. This concept suggests that the extreme conditions of the Qinghai-Xizang Plateau might contribute to the longevity of its trees, says Zhang.

　　The role of ecological resilience

　　One key factor in the longevity of these trees is ecological resilience, which is the capacity of trees to actively respond to environmental stresses and disturbances. As trees age, their demand for photosynthetic products, water, and nutrients increases. If the supply of these resources cannot meet the demand, the tree's ecological resilience declines, making it more difficult for the tree to survive natural disasters such as extreme climate events and pests, ultimately affecting its ability to reach old age.

　　However, the ancient trees of the Qinghai-Xizang Plateau, like the cypress, have adapted to their harsh environment through a strategy of slow growth, reducing their demand for resources and maintaining their ecological resilience over long periods. This adaptation can be seen in the exceptionally narrow tree rings of millennia-old cypress trees on the plateau, usually less than 1 millimeter wide, indicating their remarkable ability to endure and thrive in adversity.

　　Ancient trees tell stories of past climates

　　The tree rings of these ancient giants hold vast amounts of information about past climate conditions. For instance, research on seven millennia-old cypress trees in Qinghai province revealed wider tree rings between 929 and 1031 AD, correlating with increased rainfall from May to June over that period. This suggests favorable moisture conditions during the Medieval Warm Period, highlighting how ancient trees can provide insights into historical climate patterns.

　　Moreover, the resilience and "memory" of trees, as observed by Zhang and his team, show that trees can accumulate experiences from past disturbances, enhancing their resilience against future challenges. This ability was evident in ancient cypress trees in Xizang, where narrower growth rings indicated a two-hundred-year period of hardship, followed by a return to normal growth.

　　Cultural and archaeological significance

　　According to Zhang, the ancient trees in the Qinghai-Xizang Plateau are not only valuable for their climatic and ecological records, but also because they hold cultural and archaeological significance. In some areas, these trees are revered as sacred, which has helped protect them from human destruction. Additionally, tree ring data from ancient trees has played a crucial role in archaeological studies, such as dating the construction period of ancient tombs in Qinghai province.