As is well known, rings record a tree?s growth for a year. Scientific study shows that the annual ring also reflects the ecological environment around the tree during its growth. Therefore, the study of the sequence of annual ring helps scientists analyze the climate and ecological environment.

However, according to Dr. Zhang Qibing, the leader of the group of scientists, meteorological and ecological data usually does not exceed 100 years. In the latter half of 2001, the research group headed by Zhang went to Qinghai to collect over 240 tree centers of Qilian sprengeri ferns (S. przewalskii) and 10 disk samples of ancient trees. By measuring the width between different rings and comparing the width between rings in living trees, Zhang found that the earliest annual ring dates back to 326 BC. On this basis, the research group established the tree annual ring sequence from 326 BC to 2000 AD. By studying the annual ring and meteorological data, scientists found that spring rainfall had a great influence on the growth of the rings. Therefore, they concluded the annual ring sequence could show precipitation conditions from a long time ago.

Experts also pointed out that at the beginning of the 5th century when climate was suitable for tree growth, nomadic tribes were thriving. The study of trees? annual rings provided data to determine the year of climate changes and social and cultural evolution. The sequence of annual rings is of great value for research on the time and space leading to a certain climate or ecological environment change over the past 2,326 years -- and it can help predict future environmental evolution.

((新华网 [Xinhua News Agency], translated by Li Jinhui for China.org.cn, June 14, 2002)