You are here

Initial Impressions of the Summer Ahead

Tuesday, June 3, 2014, by Alison Ochs
Printer-friendly version

[Hemlock branch with the small, white, woolly masses - signs of the hemlock woolly adelgid - visible at the base of some needles]When I first arrived at Harvard Forest, I saw green. The woods were beautiful, the trails stunning, and all I could tell was that the forest around me was unlike anything I was used to. 

What I didn’t see initially were the dying trees, the falling needles, and the slow decline of a once healthy hemlock forest. Yes, the maples were fine, the pines booming, even some chestnuts starting to sprout, but the hemlock was fading away. This loss and its accompanying effects on the forest ecosystem are what I am here to study.

The hemlock woolly adelgid is an invasive insect that attaches to the base of hemlock needles, both eastern and Carolina species. It appears as a small, woolly dot of cotton, hardly noticeable unless you’re looking. The insect is small enough that it can be carried by wind or birds, or on infected horticulture plants. While it cannot survive under -13 degrees Fahrenheit, restricting its range somewhat, with global climate change its range has been extending north, including to the Harvard Forest. Infested trees have begun to decline, losing needles and slowly weakening, and will die within a few years.

This loss will have wide reaching effects on the ecosystem. As the hemlock passes away, new trees will take its place, pines and beeches among other species. I have joined the study examining how the change of forest affects its residents, from small mammals and salamanders to ants and other vegetation. Most of my work will be helping with the salamander study.

[Red eft, the terrestrial middle stage of growth of an eastern newt] One of our projects will be calibrating the survey methods for salamanders. Commonly, salamanders are surveyed by laying down wooden boards and counting the salamanders that congregate beneath them. However, it is possible that the salamanders are attracted to the artificial habitats, and so this method may give skewed results. We will be spending several nights a week searching for salamanders along a transect and in established sample sites to compare with the data we gain from the board method. By calibrating the two methods, we will be able to increase the accuracy of the study and improve sampling methods for future studies.

With more experience in the woods, I’ve learned to hear the sound of falling needles and see the dying trees. I note the fallen branches and the thinning canopies, and check branches for infestations. There is little we can do now to control the spread of the adelgid, and the hemlock’s prospects are bleak. Though saddening, I gain hope from knowing that nature is durable: a similar die off of the hemlock has occurred before, about 5,000 years ago. It took the forest several millennia to recover, but recover it did, and so hopefully it will do so again.


[Alison Ochs at the top of a research tower in the Prospect Hill tract of Harvard Forest] 

Blog tags: 

Add new comment