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 and 2013, and saplings growing into the "tree" size class of greater than or equal to 5cm diameter were measured, tagged and mapped.

本数据集涉及的样地于1990年建立并测绘，初始实验旨在探究上层林木选择性死亡的生态效应。实验原计划在4块样地中各针对一个树种进行灭杀并保留其枯立木，以模拟物种特异性病原体引发的林木死亡。但因后勤协调困难，且铁杉球蚜（hemlock woolly adelgid）的出现提供了更为紧迫的“自然”实验对象，该人工操控方案最终未能实施。不过该批样地至今仍得到妥善维护，并被应用于多项其他研究。
本次数据集包含4块50m×50m的样地，均设置于飓风实验研究区北侧的混交硬木林内，该林分以红栎和槭树为主要组成树种。
由于所有样地处于同一区域且林分类型一致，且对所有林木采用了相同的测量规范，因此部分分析可纳入飓风实验研究的对照样地林木数据。
研究人员分别于2003年与2013年秋季对该批样地开展了林木胸径与健康状况的复测，并对胸径≥5cm、已达到林木径级标准的幼树进行了测量、挂牌及测绘。