Late-Holocene vegetational history of a subtropical mountain in Southeastern China.

摘要

This research primarily examines the pollen evidence of vegetation change in the light of human disturbance in the subtropical mountains in southeastern China based on three sediment cores from the elongated peat-filled depressions in subalpine headwater zones (dambos) from the Daiyun Mountain Range of Fujian Province (approximately 25;Analysis of pollen and sediment-stratigraphic data from this study indicates that peat accumulation began in the three coring sites after 4,000 yr BP, probably as a result of the late-Holocene cooling. From 4,000 to 1,100 yr BP the vegetation of the upper mountain zones (between 1,300-1,600 m) of the Daiyun Mountain Range was a subtropical mixed conifer-hardwood forest dominated by Cryptomeria (Japanese cedar), Castanopsis (chinkapin), Quercus (oak), and Tsuga (hemlock). Widespread deforestation occurred between 1,500 and 1,000 yr BP when pollen frequencies of these dominant tree taxa were abruptly reduced, followed by increases in Pinus, Gramineae, and Dicranopteris. This abrupt vegetation change took place soon after the large-scale immigration of the Han Chinese to the region from North China, suggesting an anthropogenic origin. This hypothesis is also supported by the subsequent sedimentary changes. The event was followed by a distinct clay layer in one of the sediment cores, suggesting an intensified soil erosion occurred on the slopes of the catchment areas after the removal of its primeval forest cover. Pine woodland became a dominant secondary vegetation type in the study area after the major deforestation.;The results of the pollen rain study indicate that modern pollen rain in the hilly country of the Chinese tropics and subtropics is dominated by the Pinus-Dicranopteris-Gramineae assemblage except for in some very remote and protected areas where substantial pollen frequencies of the mesic subtropical forest components can be found. The occurrence of the pine woodland pollen assemblage is a good indicator of intensified human disturbance.