Long-term Vegetation Dynamics on the Massachusetts Coast from 2000 BP to Present

We use a retrospective approach to reconstruct the past distribution of fire in New England and to investigate the important drivers of this pattern across the period of European arrival to North America. Our study sites are in New England, and range from pitch pine and oak forests of coastal Massachusetts, pine and hardwood forests of central Massachusetts, and northern hardwood and spruce fir forests of northern Massachusetts and Vermont. We collected sediment profiles from 18 lakes across the study area to assess fossil charcoal and pollen abundance over the past 1000 years and including the time period of European arrival and settlement. Based on presettlement pollen composition, our study sites are divided into three vegetation types: 1) pitch pine and oak, 2) oak, pine, and hardwood, and 3) northern hardwoods. The abundance of presettlement charcoal in these lakes is closely related to climate and the composition of surrounding vegetation. Charcoal is most abundant in pitch pine forests and least common in northern hardwood and spruce forests. Following the arrival of Europeans, charcoal abundance increases, at most sites substantially, and vegetation composition changed in a direction of either greater dominance by pitch pine or white pine, depending on whether the forests were located in the southern or northern part of New England. The major factor influencing the distribution of fire across New England is climate, which has a direct effect on the physical conditions conducive to fire ignition and spread and an indirect effect on fire through its control on the distribution of vegetation at this spatial scale. We find evidence that other factors exert some control over local fire regimes as well including landforms and their impact on vegetation composition, firebreaks, and prevailing winds. Native Americans likely influenced the local occurrence of fire, but their impact on regional fire regimes in New England is not apparent from this or other studies. However, additional paleoecological, archaeological and historical work needs to be done to better address this question. In contrast, Europeans had a dramatic effect on fire throughout the New England landscape, increasing its occurrence almost everywhere.

本研究采用回溯法重建新英格兰地区历史火灾分布，并探究欧洲人抵达北美以来该区域火灾格局的关键驱动因子。本研究的样地位于新英格兰地区，涵盖马萨诸塞州沿海的脂松（pitch pine）-栎林、马萨诸塞州中部的松林-硬叶林，以及马萨诸塞州北部与佛蒙特州的北部硬叶林-云杉冷杉（spruce fir）林。研究团队在研究区域内的18个湖泊中采集了沉积物岩芯剖面，以分析过去1000年（含欧洲人抵达与定居时段）的化石炭与花粉丰度。基于欧洲人定居前的花粉组成，本研究样地被划分为三类植被类型：1）脂松-栎林；2）栎-松-硬叶林；3）北部硬叶林。上述湖泊中定居前的化石炭丰度与区域气候及周边植被组成密切相关：脂松林中的化石炭丰度最高，而北部硬叶林与云杉冷杉林中的化石炭丰度最低。欧洲人抵达后，多数样地的化石炭丰度出现显著上升；同时植被组成发生改变，根据林分位于新英格兰南部还是北部，分别朝着脂松占优或白松占优的方向演替。影响新英格兰地区火灾分布的核心驱动因子为气候：气候直接作用于利于火灾引燃与蔓延的物理条件，并通过调控该空间尺度下的植被分布，对火灾产生间接影响。研究同时发现，其他因素也对局地火灾格局存在一定调控作用，包括地形及其对植被组成的影响、防火隔离带以及盛行风。美洲原住民可能对局地火灾的发生存在影响，但本研究与其他相关研究均未揭示其对新英格兰区域火灾格局的显著作用。不过，未来需开展更多古生态学、考古学与历史学相关研究，方能更深入地解答这一问题。与之形成鲜明对比的是，欧洲人对新英格兰全境的火灾活动产生了显著影响，几乎在所有区域都提升了火灾的发生频率。