Michael Gaige, MS '09

Conservation Biology

Legacy Tree

You see them out in the forests at times, gnarly old trees that announce their presence by the fact that they grow not up, but out. Perhaps hard by an old stonewall, perhaps at the crest of a ridge, these trees lend a distinct character to the woods around them. Some folks call them ‘wolf trees,’ because of the way they stand alone in the forest, while others deem them wolves because, they say, these trees prey on forest resources. Michael Gaige, a third year AUNE conservation biology master’s student, refers to them as “legacy” trees and has made them, and their little-studied role in the ecology of a forest, the focus of his research.

As their name implies, legacy trees are those left behind, memories of a disturbance to the forest sometime in the past. Such a disturbance could be the result of a natural event or cultural event. Gaige focused his studies in Vermont where, as he put it, “Rather than having lava pour over the landscape, we had humans pour over the landscape.”

Gaige figures he’s spent about 650 hours in the field, searching out and studying cultural legacy trees. What did he look for? While there’s no hard and fast definition of a legacy tree, he looked for trees that were at least twice the diameter of the largest nearby trees and that showed an open growth form. Trees growing close by one another in a forest tend to race one another upwards, putting their energy into growing toward the canopy to capture sunlight. The trees Gaige searched for are a consequence of farming and grazing practices that allowed individual trees to grow and thrive in clearings where their growth extended outward, as well as upward.

Listening to Trees

He began his research in the spring of 2007 and soon learned where to look and, oddly enough, what to listen for. The legacy trees tended to grow near walls that once marked pastures. A few grew along ridges in old pasture lands, apparently left uncut by farmers to provide shade for livestock escaping gnats and flies. Others grew by vernal pools, which prompted Gaige to listen for the songs of spring peepers to lead him to the pools and, on occasion, the trees he sought. By summer’s end, he had cataloged twenty-eight legacy trees and paired each with a nearby control tree of the same species. For each pair he recorded data that will help him better define the role of the trees in a forest ecosystem. Gaige used a mix of observational methods, including looking for indirect signs of use (denning, nesting), small mammal trapping, motion sensitive remote cameras, snow tracking during the winter, and, in what he termed a “a great lesson in patience,” direct observation of each tree in his survey with “no gadgets or gear, just eyeballs and ears.”

Though he aims to continue his observations for at least another season, Gaige has already developed a sense of his legacy trees’ role in the forest. At a very basic level, he notes that “legacy trees are 100 years or so ahead of other trees, which means they’ll die 100 years ahead of others, providing structure for the forest floor. Instead of a carpet of needles and leaves, you have lumps and cavities, downed branches and trunks, all adding complexity to the structure of the forest.” Wildlife makes use of that added structure for nesting and protection. “They appear to act as a focal area,” he adds, “a ‘town square’ within their patch of forest.” Birds especially appear drawn to the trees, flocking to them in greater number and spending more time in and around them than at the control trees. From early observations, it appears that these ‘wolf’ trees are in fact rare resources in forests, enriching their immediate environs by offering structure, cover, and other resources to the immediate ecosystem. Gaige expects his research to be of more than academic value. Hopefully, it will lead to changes in forest management practices that encourage the growth of legacy trees, once they lose their reputations as lone wolves of the woods.