For more than a century, Great Mountain Forest has served as a laboratory for forest science. The focus has been on trees, but now a new element—the moose—is under its metaphorical microscope.
Moose, usually denizens of northern forests, were unexpectedly detected in the forest in 2002, even though Connecticut is on the southern fringe of moose habitat. Eight years later, research into the effects they were having on the forest was initiated and in 2020, a second study was begun to determine their population.
Deploying game cameras at known foraging spots, Great Mountain Forest has identified 21 animals: 11 mature bulls, two adolescent bulls, five cows and three calves. This accounts for about one-quarter of the moose in Connecticut, according to DEEP estimates.
Although moose are breeding in the forest, anecdotal reports suggest their population is decreasing. Climate change is one factor that allows ticks to remain active in winter, continuing to prey on and weaken the animals.
Another factor limiting population growth is less area that attracts moose. The animals are drawn to areas where trees have been cut down, allowing younger trees to grow. As moose prefer to browse at head height, they look for trees roughly four to eight inches in diameter. Moose can walk over these young trees, bending their trunks and browsing on the upper branches.
While the moose population has been resident at GMF, scientists have taken the opportunity to compare their impact on forest development to that of white-tailed deer. In 2010, researchers Ed Faison, senior ecologist at Highstead Foundation, and Steve DeStefano, retired leader of the Massachusetts Cooperative Fish and Wildlife Research Unit, began collaborating with Great Mountain Forest to set up experimental moose and deer exclusion plots.
Each plot was fenced in different ways to dictate which species could access its vegetation. Comparing the trees, shrubs and other plants in the plots is allowing researchers to study how selective foraging patterns affect the forest.
According to Faison, the browsing effects of deer alone on the forest have been minor and often not much different from the plot where browsers have been completely excluded. The effects by moose and deer combined have been large and point to moose being the dominant browser in these harvested areas.
Here are some of the strongest patterns :
- Moose and deer together have reduced the number of trees less than 1 inch by about 30 percent.
- By creating a more open forest, moose and deer together have increased the number of trees that have grown larger than 5 inches in diameter. In the herbivore exclusion and deer browsing plots, none of the more densely packed trees have grown above 5 inches in diameter. This increase in large trees has resulted in a greater tree size diversity in the area browsed by both moose and deer relative to the other plots.
- By browsing deciduous tree species and avoiding white pine, moose plus deer have increased the abundance of pine. Pine comprises almost half the tree area in the moose and deer plot compared to only one-sixth to one-eighth of the tree area in the other plots where deciduous species are more abundant.
- Moose plus deer browsing has greatly reduced the abundance of early successional (aka pioneer) tree species such as pin cherry, gray birch and paper birch. These fast-growing tree species are particularly susceptible to browsing because they are shade intolerant and, once they are reduced in height by browsing, they tend to die out under the shade of other trees.