UNH Today

Ecological Insights and Education at New Hampshire's Experimental Forests

The U.S. Forest Service’s Experimental Forests and Ranges program began in the early 1900s to provide long-term research sites for studying ecosystem services, silviculture, wildlife habitat, and forest management. Part of a network of 84 experimental forests across the United States, New Hampshire’s Bartlett Experimental Forest, established in 1931, and Hubbard Brook Experimental Forest, founded in 1955, have been central to ecological research and conservation efforts in the region.

At the Bartlett Experimental Forest, UNH researchers have studied forest management practices, carbon sequestration, and wildlife responses to environmental changes. Research at the Hubbard Brook Experimental Forest was pivotal for discovering acid rain in the 1960s. Today, UNH researchers continue to explore how forests store carbon, the effects of climate change, and the impact of invasive species at this location.

Beyond their research contributions, both forests serve as critical outdoor laboratories for UNH students, offering hands-on research opportunities that are vital for training future scientists to work in and learn how to effectively manage local ecosystems. Additionally, UNH researchers extend their work to other U.S. experimental forests, such as studying hydrology and nutrient cycling in Puerto Rico’s Luquillo Experimental Forest.

In the heart of New Hampshire's White Mountain National Forest, the Bartlett Experimental Forest has served as a living laboratory for nearly 90 years, enabling scientists to conduct unique, long-term research to better understand the complexities of New England’s ecosystems. A recent 12-year study by scientists with the New Hampshire Agricultural Experiment Station (NHAES) and the U.S. Forest Service’s Northern Research Station revealed that mice, voles and other small mammals can annually adapt the timing of their reproduction to coincide with peak seed abundance from nearby trees. And the behaviors of these small forest animals can have big implications, influencing seed dispersal, aiding in tree regeneration and sustaining the biological and economic resilience of New Hampshire's forests.

But what’s causing the need for such adaptations?

“Masting events, where trees like the American beech and eastern hemlock produce large quantities of seeds in some years but very few in others, create a fluctuating food resource that small mammals must navigate,” explained Rebecca Rowe, an NHAES scientist and professor in UNH’s College of Life Sciences and Agriculture. “Our study revealed that these events drive small mammals to adjust the timing of reproduction–by up to 79 days–but has little effect on the number of offspring in a given litter.”

These findings, recently published in the Journal of Animal Ecology by Rowe and lead author Ryan Stephens, an assistant professor at East Tennessee State University, demonstrate that during years with significant masting events, many small mammals breed later in the season to align peak lactation with peak seed availability. Conversely, when seeds are scarce, these animals breed earlier, relying on stored resources to support their offspring.

The study examined five small mammal species—northern short-tailed shrew, southern red-backed vole, woodland jumping mouse, white-footed mouse, and deer mouse—revealing distinct species-specific responses to masting events.

“Different species respond uniquely to changes in seed availability,” said Stephens. “For example, the deer mouse times its reproduction closely with peak seedfall—when seeds are naturally dispersed by plants—while species like the southern red-backed vole are more flexible, producing a second litter in non-mast years when seeds are scarce, and fungi become a key food source.”

The study also highlighted how dietary habits and overwintering strategies influence these reproductive responses. Species that hibernate, like the woodland jumping mouse, have a limited window to breed and must carefully time their reproduction to ensure their offspring have sufficient resources before the onset of winter.

The implications of this research extend far beyond the reproductive habits of small mammals. By aligning their reproductive strategies with the availability of seeds, these animals play a crucial role in the health and regeneration of forests. The timing of their reproduction influences seed dispersal and tree regeneration, both of which are essential for maintaining biodiversity and stability within forest ecosystems.

“The way these small mammals adapt to resource availability has a ripple effect throughout the entire ecosystem, impacting everything from seed dispersal to interactions among predators,” explained Rowe. “And by closely monitoring these patterns, we can anticipate changes in forest dynamics and identify management practices that support long-term ecosystem stability.”

This research is particularly important in the context of climate change, added Rowe. As global temperatures rise and weather patterns shift, the frequency and intensity of masting events may change, potentially disrupting these well-established reproductive cycles. Such disruptions could lead to mismatches between seed availability and the reproductive timing of small mammals, ultimately threatening the balance of forest ecosystems.

Rowe highlighted the importance of long-term ecological studies like this, emphasizing their role in predicting climate change impacts on these intricate relationships and informing strategies to mitigate potential ecological disruptions.

This work is co-authored by Ryan Stephans, Joshua Willems, Mariko Yamasaki, Christine Costell and Rebecca Rowe.

This material is based on work supported by the NH Agricultural Experiment Station through joint funding from the USDA National Institute of Food and Agriculture (under McIntire-Stennis award numbers 1006881, 1016133 and 1026211) and the state of New Hampshire.