PRELIMINARY STUDY OF CHARCOAL MORPHOLOGY AND ITS ENVIRONMENTAL SIGNIFICANCE
现代植物炭屑形态的初步分析及其古环境意义*

23 species of modern plants which are typically found in North China were burned in open fire, after which charcoals bigger than 500μm were collected by sieving. The results of microscopy observation show that charcoal can be divided into three groups by their length/width ratio.Charcoals from grasses have the greatest length/width ratio, 10.2±1.3 on average; woody charcoals 3.1±0.2; while charcoals from woody plant leaves the smallest,averaged 1.7±0.1. In morphology, charcoals of grasses are long and thin, mostly have sharp edges and breakpoints. Some have stomata observed and only a few have irregular shape.Charcoals from wood are generally of rectangular or cubic shape with rough edges. Charcoals from leaves are normally lamellar and reticular in shape. The results of the broken-experiment reveal that both the length and the length/width ratio of all kinds of charcoals have the trend of decrease. Furthermore we observed six surface soil samples of grasslands and forests from the Middle and West of China as well as the Tibetan Plateau. We found out that charcoals from surface soil are generally smaller than those from the modern plants. The length of charcoals from grasslands is 54.4±1.5μm while those from forests is 51.0±1.3μm. However, their L/W ratios are 2.8±0.1 and 2.2±0.1 respectively, largely different from each other. The L/W ratio, as well as some morphological characteristics can thus be used to distinguish herbaceous and woody charcoals. Finally, we measured 12 charcoal samples of S1~S0 layers at Weinan loess section in the Loess Plateau of China for the purpose of researching its palaeoenvironmental significance. The reconstructed vegetation is similar to that resulted from pollen and phytolith analyse. The preliminary study of charcoal morphology shows that charcoal not only can be used as the indicator of ancient wild fires but also have palaeoenvironment reconstruction potential.