ABSTRACT

Pre-Euro-American settlement vegetation provides information about historical ecology. I evaluated baseline conditions and novel status of current forests in Michigan using historical (1836 to 1858) and current (2010–2015) surveys and assessed quantitative and qualitative measures of novel status. Aspen (increased from 2% to 11% of all trees) and red maple (<2% to 12.5%) replaced eastern hemlock (15% to 2%) and American beech (8% to <1%) as most abundant species. Density was similar between surveys but mean diameter (trees ≥12.7 cm) decreased from 39 to 22 cm. The emerging forest type is a mix of early- to mid-successional species, particularly red maple, from eastern broadleaf forests of the central-eastern US.Openlands in southern Michigan have been replaced by agriculture and closed forests. Historical forests dominated by few tree species have transitioned to diverse eastern broadleaf forests throughout the eastern US, conforming to quantitative and qualitative measures of novel ecosystem status. Besides exceeding a quantitative threshold (e.g., squared chord distance), current forests meet novel status because they are ubiquitous, constitute a new normal, arise predictably, and unavoidably in response to disturbance or land-use change, auto-organize, and retain novelty after crossing thresholds challenging to reverse.

摘要

欧美前的定居植被提供了有关历史生态学的信息。我使用历史调查（1836年至1858年）和当前调查（2010年至2015年）评估了密歇根州现有森林的基准条件和新状况，并评估了新状况的定量和定性测量方法。白杨（占所有树木的2％至11％）和红枫（<2％至12.5％）取代了东部铁杉（15％至2％）和美国山毛榉（8％至<1％）作为最丰富的树种。两次调查的密度相似，但平均直径（≥12.7厘米的树）从39厘米降低到22厘米。新兴的森林类型是来自美国中东部的东部阔叶林的早期至中期的成功物种，尤其是红枫。密歇根州南部的开阔土地已被农业和封闭森林所取代。在美国东部地区，以少数树种为主的历史森林已过渡到多样化的东部阔叶林，符合新生态系统状况的定量和定性测量。除了超过定量阈值（例如弦长平方）以外，当前的森林还具有新颖的地位，因为它们无处不在，构成新的常态，可预测地出现，并且不可避免地响应干扰或土地利用变化，自动组织并保持新颖性越过挑战性逆转的门槛后。