Data from: Early departures and delayed arrivals: Holocene dynamics of temperate tree species in the boreal temperate ecotone

Understanding historical dynamics of peripheral populations over the
Holocene provides key insights to anticipate species responses to ongoing
global changes. A marginal stand at the leading edge of sugar maple (Acer
saccharum) range was hereby investigated to infer the Holocene dynamics of
sugar maple, red maple (Acer rubrum), eastern white pine (Pinus strobus),
three prominent temperate tree species of the boreal-temperate forest
ecotone in eastern Canada. Soil macrofossil charcoal analysis of 25,595
charred wood particles revealed that white pine is detected at this
marginal temperate forest site since the early-Holocene, red maple since
the mid-Holocene, and sugar maple since the late-Holocene.  The
transition from the warmer mid-Holocene to the cooler late-Holocene was
marked by a decrease of white pine, which was expected because the overall
bioclimatic envelope of temperate species shifted southward in response to
lower mean temperatures of the Neoglacial. In contrast, the abundance of
sugar and red maples increased during the cool late-Holocene
period.  There was a significant lag between the establishment of
maples, whereby the rustic red maple was found since the warmer
mid-Holocene, while the cold intolerant sugar maple was only detected
during the cooler late-Holocene. A shift in the fire regime, a disruption
of coniferous priority effects in the soil, as well as the introduction of
shared mycorrhizal fungi might tentatively explain late establishment of
maples and the migration lag between the two species.  Synthesis:
As temperate tree species require warmer temperatures than boreal species,
some thermophilous species, such as white pine, increased in abundance at
their northern edge during historically warmer periods. Our data reveals
that not all temperate species behaved accordingly: maples were scarce
during the warm mid-Holocene, while their abundance increased during the
cool late-Holocene. A migration lag suggests that earlier arrival of
generalist species such as red maple might be required to facilitate later
establishment of specialists such as sugar maple. The historic decoupling
between macroclimatic trends and temperate species range shift sheds new
light on the potential responses of the boreal-temperate ecotone facing
modern-day anthropogenic climate change.

解析全新世（Holocene）边缘种群的历史动态，可为预判物种对当前全球变化的响应提供关键见解。本研究针对加拿大东部北方-温带森林交错带（boreal-temperate forest ecotone）的三种优势温带乔木——糖枫（Acer saccharum）、红枫（Acer rubrum）与东部白松（Pinus strobus）——的分布前缘边缘林分展开调查，以推演这三个物种的全新世动态。通过对25595颗炭化木材颗粒开展土壤大化石炭屑分析，结果显示：该温带边缘林分中，东部白松的记录可追溯至全新世早期，红枫始于全新世中期，糖枫则出现于全新世晚期。从暖期全新世中期向冷期全新世晚期的过渡阶段，东部白松的丰度出现下降——这一结果符合预期，因为新冰期（Neoglacial）平均气温降低，温带物种的整体生物气候适宜区随之向南迁移。与之形成对比的是，在寒冷的全新世晚期，糖枫与红枫的丰度均有所上升。两种枫属植物的定植存在显著滞后效应：乡土红枫早在暖期全新世中期便已出现，而对低温敏感的糖枫仅在寒冷的全新世晚期才被观测到。火动态格局的改变、土壤中针叶树优先效应的打破，以及共享菌根真菌的引入，或可初步解释枫属植物的延迟定植以及两个物种间的迁移滞后现象。综合分析：相较于北方树种，温带乔木需要更高的温度，因此部分嗜热物种（如东部白松）在历史暖期的北部分布区丰度有所上升。本研究数据表明，并非所有温带物种都遵循这一规律：枫属植物在暖期全新世中期较为稀少，却在寒冷的全新世晚期丰度上升。迁移滞后现象提示，红枫这类广适性物种的先期定植，或可促进糖枫这类特化物种的后续建立。大气候趋势与温带物种分布范围迁移之间的历史脱耦现象，为北方-温带森林交错带应对当代人为气候变化的潜在响应提供了新的研究视角。