甘肃出土糟朽木器材质鉴定及特征分析

甘肃木器是反映河西走廊古丝绸之路文化、历史和社会重要的珍贵遗产。武威、高台作为甘肃木器重要的发现地,出土器物不仅类型、风格迥异,而且器物材质形态、结构特征明显,属于典型的糟朽木器类型。研究工作从木材学的角度出发,应用生物切片技术,对出土器物材质树种、特征及特性进行了科学鉴定和剖析。鉴定结果表明,树种类型有:①云杉；②冷杉；③圆柏；④落叶松；⑤胡杨；⑥榆树；⑦香椿；同时采用扫描电镜、X射线衍射分析技术对糟朽木质纤维显微形态、结构进行了观察和分析,分析结果表明:出土糟朽木器木质结构已发生降解、腐变,其材质形态特征及特性会随着后期保存环境及其因素的影响、腐蚀而频繁变化或骤变。最后,分析工作对糟朽木器纤维素结晶度、降解度等相关物理参数进行了实验测定。测定结果表明:出土实物纤维素结晶度约为58%,而纤维降解度达到40%以上。综合以上鉴定结果和实验数据,得出以下结论:①甘肃木器制作材质涉及的树种种类较多,基本以云杉材为主,而青海云杉在祁连山林区分布广泛,为其制作用材提供了丰富的天然材料；②材质糟朽及纤维严重降解是甘肃木器重要的材质特征,表现为纤维(纤维素、半纤维素)含量降低呈现木素含量升高,而木素含量的相对增大,则是导致材质颜色变深的重要原因；③受糟朽器物自身含水率的变化、影响,其材质特征具有脆弱性和不稳定性,而且改变、变化过程通常具有滞后性,导致结果往往是致命的；④纤维素结晶度和纤维降解度是衡量和评估糟朽木器材质健康状况重要的物理参数,二者之间存在关联关系。本研究结果可为糟朽木器形态与结构研究提供科学依据和技术支撑。

Characteristic analysis and structure identification of rotten wooden artifacts excavated in Gansu

Wooden artifacts excavated in Gansu are a precious heritage, reflecting the culture, history, and society along the ancient Silk Road in the Hexi corridor, and are very different in type and style from artifacts discovered at Wuwei and Gaotai. These artifacts with significantly wooden textures and structural characteristics should be categorized as rotten wood. The tree species and textural characteristics of these unearthed wooden artifacts were identified using biological methods. Identification of the wood types shows that they belong to several types of tree, including spruce, fir, Sabina chinensis, larch, Populus diversifolia, elm, cedrela sinensis. Microscopic fiber characteristics and structure were observed by scanning electron microscopy and Xray diffraction, which indicated that the wood structure of these artifacts are degraded and decayed. Furthermore, the wood structure and characteristics may change according to the preservation environment and other factors. Relevant physical parameters such as crystallinity and degradability of unearthed artifacts were measured with the result that the cellulose crystallinity is about 58% and the cellulose degradability is up to 40%. Taking all these results together, it can be concluded as that:1) the texture of the wooden artifacts indicates that many species were used, with spruce (Picea crassifolia), which is widely distributed in the Qilian Mountains, being the main species; 2) these wooden artifacts are mostly decayed and degraded as manifested by a decrease of fiber (cellulose and hemicelluloses) and an increase in lignin which is a significant cause of wood darkening; 3) the wood structures are characterized by instability and vulnerability to damage; 4) the crystallinity and degradability of cellulose are critical parameters that need to be measured to assess the physical condition of such rotted wooden artifacts.