中坝制盐遗址的孢粉分析与古植被、古环境

PALAEOVEGETATION AND PALAEOENVIRONMENT BASED ON POLLEN ANALYSIS AT THE ZHONGBA SALT PRODUCTION ARCHAEOLOGICAL SITE,SOUTH WEST CHINA

考古证据表时,距今4000多年以前,重庆三峡地区的中坝遗址就开始了规模性的盐业生产。为了解盐业生产的环境背景及其影响,在中坝遗址厚达12.5m的文化堆积层进行了孢粉取样和分析。AMS^(14)C测年结果显示,这些样品分别来自新石器时代晚期(4420～3700aB.P.)、商至西周(3550～2700aB.P.)和东周(2700～2300aB P.)。孢粉分析表明:中坝遗址的样品均以草本植物花粉和蕨类植物孢子占绝对优势。主要以禾本科(Poaceae)、楼梯草属(Elatostema)和蹄盖蕨属(Athyrium)为主,而乔灌木植物花粉所占比例很低,除松属(Pinus)、桦木属(Betula)、枫杨属(Pterocarya)、栎属(Quercus)花粉外,还见到夹竹桃科(Apoeynaceae)、女贞属(Ligustrum)、(?)木属(Loropetalum)和枫香属(Liquidambar)等亚热带树种的花粉。中坝遗址及附近地区自新石器时代以来的植被以少林、灌丛草地为主,遗址周围分布大片杂草群落,并可能有大面积的农阳,表明这个地区始终存在较强的人类活动。早在新石器时代,制盐业和种植业使得低山丘陵与河谷的森林植被遭到破坏,遗址附近的河谷形成疏林草地景观。商至西周时期,尽管气候变干,但人类活动仍很强烈,似乎气候变化对盐业生产的影响不大;东周时期的气候较为温暖湿润,制盐业和农业活动规模扩大,森林植被破坏程度加大,草坡随之增多。

Zhongba archaeological site （30°20′43″N, 108°01′37″E, elevation 135 - 148m） is located in the terrace of Ganjing River,6km from Zhongxian County,Congqing City. Archaeological evidence from the Zhongba site indicates that salt production was well developed in a time period more than 4000a B. P old. To explore the natural background of the salt production and its effect on the environment, samples from a cultural layer with a depth of 12.5m in Zhongba archaeological site were collected for pollen analysis. According to AMS ^14C dating data, these samples were divided into three groups： late Neolithic period （4420 -3700aB. P. ） , Shang ＆ Zhou Dynasty（3550 2700aB. P. ）and Eastern Zhou Dynasty （2700 -2300aB. P. ）. Pollen analysis shows that the herb pollen and fern spores including Poaceae,Elatostema and Athyrium are dominant taxa in all of the samples. Tree and shrub pollen of Pinus,Betula, Pterocarya, Quercus and some subtropical species including Apocynaceae, Ligustrum, Loropetalum, Liquidambar, have relatively low percentage values. Intensive human activities, mainly deforestation and salt production,have been existing in the Zhongba archaeological site and the vicinity since the late Neolithic. Shrub, grassland and cropland were, therefore, widely distributed. Forest was destroyed to form shrub and grassland near the Zhongba archaeological site during the Neolithic period（2700 -2300aB. P. ）. Human impact was still strong during the Shang ＆ Zhou Dynasty（3550 -2700aB. P. ）although the climate became dry,implying that climate change had little effect on the salt production. The climate became warmer and moister during Eastern Zhou Dynasty （2700 - 2300aB. P. ） , in the meantime the scale of salt production and farming expanded, which resulted in widespread deforestation and promoted grassland development.