基于炭化木的长白山火山喷发测年与植被重建

The Changbai Mountains Volcano produced a massive Plinian eruption around 1000 AD, which results in a plenty of complete carbonized logs. These carbonized logs record the environmental information before the volcano eruption. This project aims to According to the carbonized logs, this project aims to date the eruption of Changbai Mountains Volcano and reconstruct vegetation over Changbai Mountains. We accurately determine the volcano eruption time using the AMS 14C dating method and dendrological calibration curve wiggle-match method. According to the growth vigor of spring wood and autumn wood in the volcano eruption year, we determine the season of the eruption. On the basis of principles and methods of plant anatomy, we identify the carbonized logs species and determine the tree age, and then reconstruct forest vegetation (including tree species composition and forest age structure) before the volcanic eruption. Subsequently, on the base of comparative analysis of the current forest vegetation composition and that before the volcanic eruption, we quantize the differences between the current forest vegetation composition and that before the eruption, and determine the reasons for the differences of the current forest between different slopes over the Changbai Mountains. According to the new perspective of carbonized logs, the project studies the Changbai Mountains volcano activities and reconstruction of vegetation, which has direct significance for accurately estimating the vegetation succession of the Changbai Mountains after the volcanic eruption, and provides scientific basis of investigating the millennial-scale vegetation changes over the Changbai Mountains. Meanwhile, the project has important significance for revealing the interference patterns of the Changbai Mountains volcanic eruption on the forest of different slopes and the role of environmental changes on forest tree species composition.

长白山火山在1000 AD左右发生一次大喷发后，保留了记载着火山喷发前环境信息的大量完整炭化木。本项目以长白山为研究区，利用AMS系统进行炭化木14C测年，通过高精度树轮曲线摇摆匹配，精确测定火山喷发年代；通过分析带树皮炭化木最后一年春材和秋材的长势，确定火山喷发的季节；利用植物解剖学原理及方法，鉴定炭化木树种并测定其树龄，重建火山喷发前的森林树种组成和年龄结构；通过对比分析火山喷发前与当前森林树种组成、林龄结构，量化火山喷发前与当前森林树种组成的差异，确定当前长白山森林的坡向差异是因火山喷发后各坡向的演替模式不一样造成的还是坡向不同而伴随的环境差异造成的。本项目以炭化木为新的视角研究长白山火山活动、植被重建，对准确估算长白山火山喷发后植被演替有直接意义，为探索长白山千年尺度的植被变化提供了科学依据；对揭示长白山火山喷发对不同坡向森林演替的干扰模式和环境变化对森林树种组成的作用有重要意义。

长白山火山在1000AD左右发生一次大喷发后，保留了记载着火山喷发前环境信息的大量完整炭化木。本项目以长白山为研究区，对采集的炭化木利用AMS 14C测定火山喷发年代，并根据植物解剖学原理重建火山喷发前的森林树种组成和年龄结构，对比分析火山喷发前与当前森林树种组成、林龄结构。研究结果表明：（1）长白山一千多年来喷发了多次，而最大那次发生在946AD。（2）千年火山喷发前，长白山低海拔主要以针叶树为主的针阔混交林，针叶林占比达到87%，阔叶树只有13%。其中，针叶树主要为红松和云冷杉，阔叶树主要是演替后期树种，如椴树。（3）当前同海拔森林也为针阔混交林，相比千年火山喷发前，针叶树比例下降（56%），阔叶树比例增多（44%），其中，针叶树主要为冷杉，阔叶树主要是演替早期树种如桦树。本项目对揭示长白山火山喷发对森林演替的干扰模式和环境变化对森林树种组成的作用有重要意义。