Climate Change Across Seasons Experiment (CCASE) at the Hubbard Brook Experimental Forest: Leaf Level Photosynthesis

Leaf-level photosynthesis was measured on all Climate Change Across
Seasons Experiment (CCASE) plots. Reference (or control) plots are
shared with the collaborating Northern Forest DroughtNet experiment.
There are six plots total (each 11 x 14m). Two are warmed 5 degrees C
throughout the growing season (Plots 3 and 4). Two others are warmed 5
degrees C in the growing season and have snow removed during winter to
induce soil freezing and then warming cables turn on to create thaws;
each soil freeze/thaw cycle includes 72-hours of soil freezing
followed by 72-hours of thaw (Plots 5 and 6). Four kilometers (2.5 mi)
of heating cable are buried in the soil to warm these four plots. Two
additional plots serve as controls for our experiment (Plots 1 and 2).
This data set includes photosynthesis measurements for 2015 and 2017
growing seasons. These photosynthesis data were gathered as part of the Hubbard Brook
Ecosystem Study (HBES). The HBES is a collaborative effort at the
Hubbard Brook Experimental Forest, which is operated and maintained by
the USDA Forest Service, Northern Research Station.

本数据集针对跨季节气候变化实验（Climate Change Across Seasons Experiment, CCASE）的全部样地开展了叶片水平光合速率测定。其参照（对照）样地与合作开展的北部森林干旱网络（Northern Forest DroughtNet）实验共享。
本次实验共设置6块样地，单块样地面积为11×14米。其中2块在整个生长季维持5℃增温（3号、4号样地）；另外2块在生长季进行5℃增温，并在冬季移除积雪以诱导土壤结冻，随后启动加温电缆实现融冻，单次土壤冻融循环包含72小时土壤结冻与72小时融冻过程（5号、6号样地），研究人员在这4块样地的土壤中共埋设了总长4千米（2.5英里）的加温电缆。剩余2块样地作为本实验的对照样地（1号、2号样地）。
本数据集涵盖2015年与2017年生长季的光合速率测定数据。上述光合数据是哈伯德布鲁克生态系统研究（Hubbard Brook Ecosystem Study, HBES）的组成部分，该研究是在美国农业部林务局北部研究站（USDA Forest Service, Northern Research Station）运营维护的哈伯德布鲁克实验林开展的合作项目。