Long-term Processes Affecting the Hemlock-hardwoods Mosaic at Sylvania, Michigan

美国农业部西瓦尼亚荒野地区的铁杉硬木森林马赛克的长期森林动态，密歇根州北部，将使用小森林空洞中的化石花粉进行研究。沉积物中记录的单个森林林分的历史将确定3000年前铁杉入侵之前以火为主导的森林生态系统中的演替群落，从而有可能看到干扰是否使某些地区特别难以入侵。因此影响了铁杉的进入和从那时起占据这些地点的铁杉斑块的位置。通过测定铁杉到达沼泽、湖泊或粗糙土壤等极端环境中的一系列地点的年代，我们将检验另一种假设，即物理环境的差异是铁杉斑块分布位置的原因。沉积物的精细分析和结果数据的时间序列分析将探索3000年前扰动从火到风的变化过程中演替路径的变化。建模将用于研究森林马赛克中林分边界位置发生的动态变化。这些结果将有助于证明森林群落对气候的响应，包括可能伴随全球变暖的扰动制度的变化。了解森林群落在景观上的马赛克图案的起源有助于森林管理者保护这方面的原生林林分的生物多样性。

Long-term forest dynamics in the hemlock-hardwood forest mosaic of the USFS Sylvania Wilderness Area, northern Michigan, will be studies using fossil pollen in small forest hollows. Histories of individual forest stands, recorded in the sediment, will identify successional communities in the fire-dominated forest ecosystem before hemlock invasion 3000 years ago, making it possible to see whether disturbances made some areas particularly invasible, thus influencing hemlock entry and the locations of hemlock patches that have occupied those sites ever since. By dating hemlock arrival at a series of sites in extreme environments, near bogs or lakes or on coarse soils, we will test the alternative hypothesis that differences in the physical environment were responsible for the locations of hemlock patches. Fine-scale analyses of sediment and time-series analyses of the resulting data will explore changes in successional pathways as the disturbance regime changed from fire to wind 3000 years ago. Modeling will be used to investigate the dynamic changes that have occurred in the positions of boundaries between stands in the forest mosaic. The results will be useful for demonstrating the response of forest communities to climate, including changes in disturbance regimes which may accompany Global Warming. Understanding the origin of the mosaic pattern of forest communities on the landscape may help forest mangers to preserve this aspect of the biodiversity of old-growth forest stands.