乔灌木根系对岩土类文物古迹的影响是近年来文物保护工作关注的热点问题,科学监测遗址附近植物根系的空间分布、根径等参数是土遗址风化和机械损害机理研究的任务之一。本文运用探地雷达技术研究了北庭故城遗址周边榆树根系的空间分布特征,探讨了榆树根系对城墙遗址的影响。结果表明:北庭故城4个探测点榆树根系信号所体现的根径信息与树龄吻合,探测区域树木根径范围50~400 mm,多数在100~250 mm。树龄是影响地下根径及空间分布的关键因素。综合考虑树龄、根径比例、大根径走向、树木与遗址位置关系等因素,认为榆树根系对北庭城墙的威胁等级为Ⅲ号探测点(外城南墙中段)>Ⅳ号探测点(外城西墙北段中)>Ⅰ号探测点(外城西墙北段南)>Ⅱ号探测点(外城西北角)。探地雷达技术能够在不损害土遗址本体的前期下,实现对遗址及其周边树木根系的无损监测,在开展植物根系对文物本体安全影响的科学评估中具有较高的应用价值。

The destruction of plants root, especially trees and shrubs, on geotechnical ancient sites is a concerned hotspot by conservators. The primary task for the weathering and mechanical damaging mechanism study of earthen ruin is how to monitor the spatial distribution and diameter sizes of plant roots around ancient sites. In this study, we aimed the Beiting Ancient Town earthen ruins, using the ground penetrating radar technology, to study the spatial distribution of elm roots that extend to the ancient city wall, and the possible influence of belowground roots on earthen city wall ruins has been deduced. The results indicated that dielectric constant ranged between 8.73 to 19.22 in four detected sites, mainly related to the soil water content and medium density belowground. Meanwhile, the roots diameter ranged between 50 millimeter to 400 mm, the minimum resolution was 50 millimeter, most of roots diameter distributed between 100 mm to 250 mm, the tree-age is the key factor that determine the roots diameter and distribution traits. Considering the tree-age, percentage of roots diameter sizes, extension direction of big roots, and relationship between trunk and ancient sites position, we confirmed that the roots with the most threaten degree to ancient city wall were, in order, the third site, the forth site, the first site, and the second site respectively. The nondestructive ground penetrating radar technology can monitor roots that grow in or around historical remains, which conform to the basic principle for cultural heritage conservation, and has very good application value in the scientific evaluation of biotic factors as roots influences on ancient sites.