Development and Expansion of Peatlands in Central New England from 14000 BP to Present

As peatlands form they create a temporal archive of community development, allowing the reconstruction of vegetation dynamics through the analysis of sediments and the development of detailed chronologies of successional change. Peatland formation occurs through two mechanisms: (i) terrestrialization, when a water body fills with sediments and peat; and (ii) paludification, the conversion of dry land to peatland. In temperate regions, where high summer temperatures may limit peat accumulation, general models of peatland development suggest that allogenic factors such as climate change control peatland development and that terrestrialization is the primary mechanism of formation. This study evaluates this widely accepted model by comparing the developmental histories of three peatlands within the same climate region in New England in order to: (i) describe the development and timing of successional events among peatlands; (ii) document the roles of paludification and terrestrialization as developmental mechanisms; and (iii) evaluate the importance of climate change vs. autogenic factors in peatland development in this temperate region. Basin morphometry, sediment stratigraphies, and chronologies of community change determined through radiocarbon dating indicate that peatland development at each site involved terrestrialization followed by paludification, with no apparent influence of broad-scale climate change on the timing of these processes. Paludification was consistently initiated coincident with the consolidation of a shrub mat across each lake-basin, and was controlled in extent and rate by the topography of the adjoining uplands. The timing of stratigraphic changes varied among sites, suggesting that autogenic factors associated with the accumulation of peat rather than regional climate change controlled development. These results provide the foundation for a model of temperate peatland development driven by autogenic factors and caution against the use of temperate peatland development as a proxy for climatic reconstruction.泥炭地在形成过程中会构建一套群落发育的时间档案，借此可通过沉积物分析重建植被动态，并建立详细的演替变化年表。泥炭地的形成存在两种机制：(i) 陆地化（terrestrialization），即水体被沉积物与泥炭填充的过程；(ii) 沼泽化（paludification），即旱地转化为泥炭地的过程。在夏季高温可能限制泥炭积累的温带区域，现有泥炭地发育通用模型认为，气候变化等外源因子（allogenic factors）主导泥炭地发育，且陆地化是主要的形成机制。本研究选取新英格兰同一气候区内的三处泥炭地，通过对比其发育历史，以达成以下三个目标：(i) 阐明不同泥炭地的演替事件发育过程与时间节点；(ii) 明确陆地化与沼泽化作为发育机制的具体作用；(iii) 评估该温带区域内，气候变化与内源因子（autogenic factors）在泥炭地发育中的相对重要性。通过放射性碳定年法（radiocarbon dating）确定的盆地地貌参数、沉积物地层序列以及群落变化年表显示，各研究点的泥炭地发育均遵循陆地化在先、沼泽化在后的顺序，且大范围气候变化并未对这两个过程的时间节点产生显著影响。沼泽化的启动始终与各湖盆区域灌木垫的固结同步，其发育范围与速率受毗邻高地的地形控制。不同研究点的地层变化时间存在差异，这表明泥炭积累相关的内源因子而非区域气候变化主导了泥炭地发育。本研究结果为‘内源因子驱动温带泥炭地发育’的模型提供了支撑，并警示切勿将温带泥炭地发育作为气候重建的代用指标。