Three dambo sediment profiles from Daiyun Mountains in central Fujian, southeastern China, were used to reconstruct the vegetation and monsoon climate history. These three dambos sites include one from Lianhuachi (Lotus Lake, 25o35'N, 118o9'E) and two from Jiuxianshan (25o40'N, 118o8'E).
Pollen stratigraphies recovered from the three dambos sites indicate that the original vegetation for the region during 4,000-2,500 yr B.P. was a mixed conifer-hardwood forest, a more diverse and productive forest than the pine woodlands of today. A major vegetation change occurred at about 2,500 B.P. when the pollen frequencies of the major tree species (mainly Cryptomeria, Castanopsis, Lithocarpus, Quercus, and Tsuga) were slightly reduced. This vegetation change seems to have occurred mostly at lower elevations because no distinct changes in the sedimentological records of the three dambo cores were detected. The second major vegetation change took place around 1,600 B.P. and was documented in all three pollen stratigraphies as an abrupt decline in the major tree species accompanied by an increase of Pinus, Gramineae, and Dicranopteris. It occurred at a larger scale and reached two of the three catchment basins of the dambo sites under study. Since then the secondary pine woodland has persisted to the present.
Deforestation by human activities is probably the major cause of the documented vegetation changes. The first vegetation change occurred when trees were cut down at lower elevations. The second vegetation change was caused by a more extensive deforestation which reached up to the catchment basins of the two lower dambos sites. This happened during the years between 307 to 420 A.D. when large number of Han Chinese migrated to Fujian Province to escape the wars and political turmoil in North China. This deforestation marked the end of the original mixed conifer-hardwood forest and the initiation of the present-day pine woodlands.
The growth of a mixed conifer-hardwood forest before the formation of dambos in the headwater zones suggests that the climate was probably warmer and/or drier prior to the beginning of the pollen sequences. The onset of cooler/wetter climate after 4,000 yr B.P. was responsible for the initiation of dambo development at the three study sites.