Long-Term Dynamics of Oak and Chestnut in Central Massachusetts from 3500 BP to Present

Despite decades of study we have limited insights into the nature of the pre-European landscape of the northeastern USA and the forces and changes that shaped modern forest patterns. Information on such long-term forest dynamics would provide critical insights into the relationships among environmental change, land-use history and biotic responses and is greatly needed for conservation planning. To address these issues we used modern, historical, and paleoecological approaches to reconstruct the 3500-year history of a New England upland region dominated by oak and (formerly) chestnut forests and to interpret the interactions among climate change, natural and human disturbance, and site factors in controlling vegetation patterns and dynamics at different spatial scales. The results indicate that stand, landscape and regional forest dynamics were most strongly driven by climate, notably an apparent cooling and increase in moisture availability c. 1500 yr BP, and European land-use activities commencing 260 yr BP. However, the abundance of oak and chestnut (fire-tolerant, sprouting species) and the distribution of hemlock (fire-intolerant) at a stand to landscape scale were also influenced by fire, which, in turn, varied with climate and human activity. Despite, or perhaps as a consequence of ongoing disturbance by fire and presumably windstorms in this hurricane-prone region, the pre-European period was marked by two 1000+ year periods of remarkably stable forest composition, separated by an abrupt compositional shift. In contrast, over the past 260 years the vegetation has changed rather continuously in response to human activity, producing stand, landscape and regional patterns that are novel ass well as recent in origin. Chestnut was a major component of some pre-European landscapes in New England, in part because of occasional fire, and that cultural and physical factors have interacted over millennia to control vegetation patterns and dynamics. Our analyses also suggest that the composition of low diversity forests can be remarkably stable over millennia. The range of ecological, cultural and management insights afforded by this study underscores the fundamental utility of very long-term research in science and policy development.尽管历经数十年研究，我们对美国东北部欧洲殖民前的景观本质，以及塑造现代森林格局的驱动力与演变过程仍所知有限。此类长期森林动态的相关信息，可为环境变化、土地利用历史与生物响应之间的关联提供关键洞见，同时也是保护规划工作的迫切需求。为解决上述问题，本研究采用现代生态学、历史学与古生态学（paleoecological）方法，重建了以栎林及（原）栗林为主的新英格兰高地地区3500年的植被历史，并解析了气候变化、自然与人为干扰、立地因子在调控不同空间尺度下植被格局与动态过程中的相互作用。研究结果显示，林分、景观与区域尺度的森林动态主要受气候驱动，尤其是距今约1500年的显著降温与水分供给增加，以及260年前开启的欧洲殖民土地利用活动。不过，林分到景观尺度下的栎树与栗树（耐火、萌枝物种）丰度，以及铁杉（耐火性差物种）的分布，同样受火干扰影响；而火干扰的强度又随气候与人类活动而变化。尽管该飓风频发区域长期受火干扰与推测的风暴扰动，欧洲殖民前的森林仍呈现出两个跨度超1000年的稳定植被组成阶段，两阶段之间存在一次显著的组成转变——这或许正是持续扰动的结果。与之形成鲜明对比的是，过去260年间，植被因人类活动持续发生变化，形成了兼具新颖性与近期起源特征的林分、景观与区域尺度格局。栗树曾是新英格兰部分欧洲殖民前景观的核心组成部分，这在一定程度上得益于偶发的火干扰；同时，文化与自然因子在数千年间相互作用，共同调控着植被格局与动态。本研究的分析还表明，低多样性森林的组成在数千年尺度下可保持极高的稳定性。本研究所提供的生态学、文化与管理层面的多元洞见，凸显了长期研究在科学研究与政策制定中的核心价值。