中国福建省亚热带山地4 000年来植被变化的孢粉记录

根据采自福建省中部戴云山脉亚高山水系源头地带(大致25°40'N,118°11'E)泥炭沉积洼地的孢粉纪录,对该地区亚热带山地植被近4 000年来的变化进行了研究.孢粉记录和其他沉积资料显示,3个取样点的泥炭沉积开始于4 000年前,很可能是全新世后期气候转冷的结果.在距今4 000～1 200年前期间,戴云山脉上部(海拔1 300～1 600 m)的植被为亚热带针阔叶混交类型,优势种属包括Cryptomeria(柳杉)、Castanopsis(栲)、Quercus(栎)和Tsuga(铁杉)等.距今1 200年前左右,该区域的植被发生了一次大的变化,表现在上述优势属种的孢粉在样品总孢粉数的比例突然下降,而Pinus(松),Gramineae(禾本科)以及Dicranopteris(芒萁)等属种的比例则提高了.这次剧烈的植被变化在其中的一个泥炭钻孔中留下了一层粘土记录,它代表了当时流域内植被受破坏后出现的严重土壤侵蚀.从泥炭沉积提取的孢粉记录还可以看出,研究区内广泛分布的松林是一种次生植被,它是人类不断干扰的结果.

A 4 000-Year Pollen Record of Vegetation Change from the Subtropical Mountains of Fujian Province, China

This study examines the pollen evidence of vegetation change in the subtropical mountains in southeastern China based on three short sediment cores from the elongated peat-filled depressions in subalpine headwater zones from the Daiyun Mountain Range in central Fujian Province (approximately 25°40'N,118°11 'E). Analysis of pollen and sediment-stratigraphic data indicates that peat accumulation began in the three coring sites after 4 000 a BP, probably as a result of the late-Holocene cooling. From 4 000 to 1 200 a 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). A major change in vegetation cover occurred around 1 200 a BP when pollen frequencies of these dominant tree taxa were abruptly reduced, followed by increases in Pinus, Gramineae, and Dicranopteris. This vegetation change was marked by a distinct clay layer in one of the sedinent cores, suggesting intensified soil erosion occurred on the slopes of the catchments area due to destruction of the climax vegetation. The extracted pollen records indicate that pine woodland in the study area is a secondary vegetation type and is a result of constant human disturbance.