Monitoring Forests for Climate Resilience

The monitoring crew heads into the forest to collect data. From left to right: NorthWoods Forestry Outreach Coordinator Devan Pensinger; NorthWoods interns Megan Strauss, Ryan Lent, and Brooke Bartlett; UVM Extension Forestry intern Loden Croll; NorthWoods intern Sarah Hosking; and Alexandra Kosiba. Photos by Ben Conant.

This past summer, University of Vermont Extension Assistant Professor Alexandra Kosiba collaborated with the NorthWoods Stewardship Center to establish climate resilience monitoring plots at a privately-owned forest in Sheffield, Vermont. The project is part of Kosiba’s effort to establish permanent monitoring plots on forestland across Vermont to examine how active management affects forests’ capacity to recover from disturbances and to remain ecologically healthy. The goal is to track the long-term outcomes of resilience-focused forest management.

To observe the effectiveness of this management over time, monitoring plots are set up in pairs. Treatment plots are located in an area of recent forest management aimed at increasing the resilience of the forest, while control plots are in an adjacent area not recently managed. In each plot, the crew measures and catalogs the trees and plants in the over- and understory, including standing dead and downed trees. They also note the presence of invasive species and other forest health issues.

“The gist of the measurements is to capture the composition and structure of the forest in each plot,” said Kosiba. “These plots will be revisited in the future and remeasured to quantify how the forest composition and structure have changed. If there is a climate-related or other disturbance, we can examine how the response of that disturbance or stress differed between the plots.”

These photographs depict Kosiba and the NorthWoods group establishing four pairs of plots at Al Robertson’s Pfälzerwald Tree Farm. Robertson has practiced ecological forest management at this 60-acre forest since purchasing the land in 1979, and he has created a trust to bequeath the property to Sheffield to use as a town forest. His stewardship of the land is inspired by German silvicultural practice, and he has worked to enhance the resilience of his woods by increasing tree species and age diversity, including planting new tree species that may be better adapted to a future climate. (To learn more about Robertson’s stewardship goals, check out our November 16, 2022 Community Voices interview.)

“We’re so fortunate to have forest landowners in Vermont like Al who care deeply about their land,” Kosiba said. “Thanks to Al, this property offers the opportunity to continue to observe the impacts of resilience-focused forest management into the future.”

If you are a Vermont landowner engaging in climate-focused management and interested in allowing UVM Extension to establish forest monitoring plots, please reach out to Alexandra Kosiba.

The entrance to Pfälzerwald, Al Robertson’s 60-acre forestland in Sheffield, Vermont.

The group established treatment plots in areas where forest management activities created canopy gaps through the harvest of selected trees, as seen in the top center of this photo, while control plots were established close by, where trees had not been removed.

Devan Pensinger installs a permanent PVC marker at the center of a monitoring plot that will allow researchers to locate the plot in the future.

Brooke Bartlett estimates the height of the different layers of the forest canopy. Variations in tree heights can be an indicator of forest resilience because a more diverse canopy structure may be able to better withstand wind, drought, and heavy rain events compared to a forest with trees of the same height. A diverse, complex structure also provides more types of habitat for wildlife.

Sarah Hosking measures the diameter of a standing dead tree. Standing dead trees, also called snags, are a critical part of a healthy forest. They provide habitat and food to a wide range of organisms, from fungi to woodpeckers, and are a key component of the forest’s nutrient cycle. As dead trees slowly decompose, carbon, nitrogen, and other important nutrients stored in the wood are incorporated into the soil.

Large legacy trees, such as this yellow birch, are a key component of resilient forests. Legacy trees are trees that are designated to never be harvested so they can live out their full lifespans.

Adjacent to each understory microplot, the crew assesses the soil for introduced, non-native earthworms, which can quickly decompose and homogenize organic matter on the forest floor faster than it would otherwise decay. If there were earthworms present, the soil would resemble coffee grounds. No earthworms were detected at this site, and the soil showed organic material in various sizes and stages of decay, a good sign of soil health.

The crew also measures and records dead logs on the forest floor. Like standing dead trees in a forest, dead wood on the forest floor is critical for resilience and ecosystem function. Dead logs protect soils from erosion, hold water during drought, store carbon, cycle nutrients to the soil, and provide habitat to a suite of biodiverse organisms. Some tree species, such as yellow birch and red spruce, germinate and grow on dead logs. Most of the forests in our region lack dead wood, especially large pieces, because of past land use.

Loden Croll and Alexandra Kosiba catalog and estimate the cover of understory vegetation within a square area of the monitoring plot. The crew uses a square made of PVC to create a microplot that helps ensure a specific area is assessed. To capture the variability in understory plants, the crew sets up five of these microplots within each larger monitoring plot – one microplot is placed at the center of the monitoring plot, and four are placed at the edge of the monitoring plot at each of the cardinal directions.