Lake Sediment Pollen from Guilder Pond in Mount Washington MA from 13882 BP to Present

Aim We analyzed a dataset composed of multiple palaeoclimate and lake-sediment pollen records from New England to explore how postglacial changes in the composition and spatial patterns of vegetation were controlled by regional-scale climate change, a subregional environmental gradient, and landscape-scale variations in soil characteristics. Location The 120,000-km2 study area includes parts of Vermont and New Hampshire in the north, where sites are 150-200 km from the Atlantic Ocean, and spans the coastline from southeastern New York to Cape Cod and the adjacent islands, including Block Island, the Elizabeth Islands, Nantucket, and Martha’s Vineyard. Results Boreal forest featuring Picea and Pinus banksiana was present across the region when conditions were cool and dry 14,000-12,000 calibrated 14C years before present (ybp). Pinus strobus became regionally dominant as temperatures increased between 12,000 and 10,000 ybp. The composition of forests in inland and coastal areas diverged in response to further warming after 10,000 ybp, when Quercus and Pinus rigida expanded across southern New England, while conditions remained cool enough in inland areas to maintain Pinus strobus. Increasing precipitation allowed Tsuga canadensis, Fagus grandifolia, and Betula to replace Pinus strobus in inland areas during 9000-8000 ybp, and also led to the expansion of Carya across the coastal part of the region beginning at 7000-6000 ybp. Abrupt cooling at 5500-5000 ybp caused sharp declines in Tsuga in inland areas and Quercus at some coastal sites, and the populations of those taxa remained low until they recovered around 3000 ybp in response to rising precipitation. Throughout most of the Holocene, sites underlain by sandy glacial deposits were occupied by Pinus rigida and Quercus. Main conclusions Postglacial changes in the composition and spatial pattern of New England forests were controlled by long-term trends and abrupt shifts in temperature and precipitation, as well as by the environmental gradient between coastal and inland parts of the region. Substrate and soil moisture shaped landscape-scale variations in forest composition.研究目的：本研究分析了新英格兰地区多套古气候与湖泊沉积花粉记录数据集，旨在探讨冰川后期植被组成与空间格局的变化如何受区域尺度气候变化、亚区域环境梯度以及景观尺度土壤特征变异的调控。 研究区域：本次研究区域面积达12万平方千米，北部涵盖佛蒙特州（Vermont）与新罕布什尔州（New Hampshire）部分区域，该区域内的研究点距大西洋150至200千米；研究范围向南延伸至纽约州东南部至科德角（Cape Cod）及其邻近岛屿，包括布洛克岛（Block Island）、伊丽莎白群岛（Elizabeth Islands）、楠塔基特岛（Nantucket）与玛莎葡萄园岛（Martha’s Vineyard）。 研究结果：在经校准的放射性碳定年距今14000至12000年的冷干气候条件下，区域内广泛分布以云杉属（Picea）与班克松（Pinus banksiana）为优势种的北方针叶林。距今12000至10000年，随着气温升高，北美乔松（Pinus strobus）成为区域优势植被。距今10000年后气候进一步变暖，内陆与沿海地区森林组成出现分化：栎属（Quercus）与刚松（Pinus rigida）在新英格兰南部扩张，而内陆地区仍维持足够低温以保留北美乔松种群。距今9000至8000年，降水增加使得加拿大铁杉（Tsuga canadensis）、大果山毛榉（Fagus grandifolia）与桦木属（Betula）在内陆地区取代北美乔松；同时自距今7000至6000年起，山核桃属（Carya）在区域沿海区域扩张。距今5500至5000年的突发性降温事件导致内陆地区加拿大铁杉与部分沿海站点栎属种群急剧下降，此类类群种群数量始终处于低位，直至距今3000年左右随降水增加才得以恢复。在全新世（Holocene）大部分时期，覆盖冰川砂质沉积物的站点始终以刚松与栎属为优势植被。 主要结论：新英格兰地区森林的冰川后期组成与空间格局变化，受气温与降水的长期趋势及突发性变化、区域沿海与内陆间的环境梯度共同调控。基质与土壤湿度则塑造了森林组成在景观尺度上的变异。