Overstory Mapped Tree Plots at Harvard Forest since 1990

These plots were established and mapped in 1990 for an experiment designed to study the effects of selective overstory tree mortality. The planned manipulation was to kill and leave standing one species in each of four plots, to simulate mortality by a species-specific pathogen. This manipulation was never done, for logistical reasons and because the appearance of the hemlock woolly adelgid provided a more pressing "natural" experiment to study; however, the plots are maintained and have been used in other studies. There are four 50m x 50m plots, located in a mixed hardwood forest (red oak and maple species are major components), north of the experimental hurricane. Tree data from the control plot of the experimental hurricane study could be added to this set for some analyses, since all the plots are in the same general area and forest type, and similar types of measurements were made on all of these trees. Tree diameter and condition were re-surveyed in these plots in Autumns 2003, 2013 and 2023, and saplings growing into the "tree" size class of greater than or equal to 5cm diameter were measured, tagged and mapped.

本数据集对应的样地于1990年设立并测绘，最初用于开展一项旨在探究上层林木选择性死亡效应的实验。原计划在4块样地中各选取一个树种进行灭杀并保留其立木，以模拟物种特异性病原体引发的树种死亡事件，但由于后勤限制，加之铁杉球蚜（hemlock woolly adelgid）的爆发提供了更为紧迫的‘天然’研究对象，该预设操控处理最终未能实施。不过样地仍得到持续维护，并已应用于其他多项研究。该区域位于实验飓风研究区以北，为混交硬木林（主要树种为红栎与槭树），共包含4块50m×50m的样地。针对部分分析需求，可将实验飓风研究的对照样地林木数据纳入本数据集，因所有样地所处区域与森林类型均一致，且林木测量方法也相似。本数据集的样地分别于2003年、2013年及2023年秋季开展了林木胸径与生长状况的复测；同时对胸径≥5厘米、达到林木径级标准的幼树进行了测量、标记与测绘。