Light Environment in Hemlock Removal Experiment at Harvard Forest since 2004

The impending loss of hemlock trees due to hemlock woolly adelgid (Adelges tsugae) infestation is expected to lead to changes in the light environment of the forest understory. These changes will both drive succession and will themselves be altered by successional processes. The light reaching the forest floor is measured using hemispherical canopy photographs. Photographs were taken in December 2004 and May 2005 (both deciduous-tree leaf-off condition), prior to the application of the logging and girdling treatments, and then in September 2005 (deciduous tree leaf-on condition) after logging and girdling. Subsequent photographic series will be taken annually in spring (leaf-off) and summer/fall (leaf-on).

受铁杉球蚜（hemlock woolly adelgid，Adelges tsugae）侵染导致的铁杉林即将消亡，预计将引发森林下层光照环境的改变。此类改变既会驱动森林演替，同时自身也会受到演替过程的调控。本研究通过半球冠层照片（hemispherical canopy photograph）测定到达林床的光照强度。照片分别于2004年12月与2005年5月采集，两次均处于落叶树落叶期，此时尚未开展伐除与环割处理；随后于2005年9月，即落叶树展叶期，在完成伐除和环割处理后再次进行拍摄。后续将每年于春季（落叶期）和夏秋季（展叶期）开展连续摄影采样。