China cypress stumps buried in a bog of primitive forest remains found in Gaoyao, south China's  Guangdong Province, may hold clues to climate changes  several  thousand of years ago.

   Carbon dating tests show that the trees in the 10-square- kilometer muddy basin in this tropical region are more than 2,000  years old.

   Chinese archeologists were excited at the discovery of the  ancient forest this year. They believe it was a shrinking virgin  forest, which used to stretch across a much larger area along the  Pearl River some 2,000 to 5,000 years ago.

   Li Pingri, a 70-year-old research fellow with the Geological  Institute under the Chinese Academy of Sciences, is now leading a  group of experts to decipher the code of ancient climates, which  can be calculated from the growth rings of the aged tree stumps.

   Li's oldest tree sample is about 12,000 years old; the youngest is 2,030.

   "Wider growth rings on the tree sections suggest a mild and  rainy climate, which indicates  favorable years for the growth of  the tree, while thinner ones imply cold or disastrous weather,  such as drought," said Li.

   Most of the trees found here are China cypress that lived 2,000- 3,000 years ago. However, no trace of China cypress younger than  that has been found.

   "The simultaneous disappearance of the tropical tree species in the virgin forest should indicate a widely-spread cold current,"  said the archeologist.

   Historical records said that between the years 1488 and 1893,  the tropical region received snow each winter. The climate  gradually turned warmer after 1893.

   The experts theorize that there may be a pattern to the climate changes. If the assumption can be proved, warm and cold climates  should rotate every 300 to 400 years, and people in Guangdong  should have another a century to go in the hottest period of a  warm climate term.  

   The experts will use more tree samples to weave out a map of  growth rings and the corresponding year of weather changes to  substantiate their assumption.

   The plant "lab" is so unusual that an ordinary China cypress is measured over three meters in trunk diameter. A strong aroma  created by old camphor in the basin can be smelled several meters  away.