Wave Hill youth researchers present findings on urban forest health and restoration

After more than a year of fieldwork and data analysis, a group of young scientists from Wave Hill presented their findings at one of New York City’s leading scientific institutions.

On Aug. 13, interns in Wave Hill’s Woodland Ecology Research Mentorship program, known as WERM, presented their three research projects at the American Museum of Natural History. Their studies explored the relationship between tree health and bat activity at Wave Hill, the effects of forest fragmentation on soil respiration and the potential restoration of American chestnut trees in Inwood Hill Park.

The 14-month paid internship allows New York City high schoolers to dive into the realm of ecology through hands-on fieldwork and independent research. In the program’s first phases. students learn foundational skills before conducting their own studies in small groups alongside research mentors.

This collective is the third to graduate since Wave Hill Youth Program Manager Ilana Weinstein entered her role, and she described this cohort as one particularly close to her heart. While some students continued multi-year studies started by previous WERM interns, others crafted their own.

“They’re looking at real topics related to climate change and forest health so they’re making real contributions as young people before they even get to college,” Weinstein said.

In a collaboration with the University of Mount Saint Vincent, interns are also enrolled in three college courses, allowing them to leave the program with several college credits under their belt.

For most of the interns, however, their accolades represented not just their growth as scientists, but the tight bonds they formed as a close-knit cohort.

Tree health as a predictor of bat activity

Amelia Hearse, Atiksh Bordia, Laila Allen and Ishrat Raisa spent 14 weeks studying whether healthier trees attract greater bat activity across Wave Hill’s garden’s 28-acre grounds.

The group installed acoustic monitors at 12 locations reflecting both densely wooded and open areas. One monitor remained at a control site, while two others rotated among the remaining locations. The devices recorded audio from 30 minutes before sunset until 30 minutes after sunrise, capturing the echolocation calls bats use to navigate and find prey.

The recordings were analyzed using Kaleidoscope, software that identifies bat species by their distinct calls. The interns also evaluated every tree wider than four centimeters within a 10-meter radius of each monitoring site, noting its diameter, height, crown condition, dieback and dead limbs.

Bat activity varied widely, from zero to 1,806 passes at individual sites during the sampling period. An initial statistical analysis found a significant positive relationship between tree health and bat activity. The interns’ model estimated that each one-point increase in tree health was associated with a 56.3 percent increase in weekly activity.

However, after accounting for tree size, temperature, wind speed, time and repeated sampling, the relationship was no longer statistically significant. The intern’s findings concluded tree health may support bat roosting and foraging, but other factors may also shape bat behavior — humidity, moon phase, and light and noise pollution, among them.

“Seeing how the data all came together at the end and seeing that there are actual results was like retribution of our efforts,” Raisa said. “That was awesome.”

Hearse said presenting the research was “very rewarding,” particularly after hearing peers and visitors at the museum express interest in and praise for the work.

Soil respiration interacts with forest fragmentation

Theo Bernstein, Michelle Garcia Rosario and Max Fong, whose study is set to be published in a youth peer-reviewed publication called “Convergence Journal,” examined how forest fragmentation affects the movement of carbon between Wave Hill’s soil and the atmosphere.

The group’s research centered on soil respiration, a process where soil releases carbon dioxide as plant roots, fungi and other living organisms break down. Because urban development divides forests into smaller patches, it also creates more forest edges, allowing additional exposure to the elements that can alter soil conditions.

They focused on two 48-meter plots in Wave Hill’s eight-acre, second-growth forest — a term for woodlands that regrow naturally after severe disturbances, like deforestation or fires. The interns monitored emissions through 26 soil collars, or short PVC pipes that are pushed into the ground and remain there throughout the duration of a study. The collars create a seal to track the carbon dioxide emitted and allows researchers to return to the same spot for repeated measurements without disturbing the surrounding soil.

The collars were positioned at varying distances from the forest edge. Twice a week, they placed a gas analyzer over each collar to measure emissions released from the ground. Sensors also recorded soil temperature and moisture every 15 minutes.

To explore what might drive respiration, the interns measured fine-root biomass and buried handmade fabric bags containing oak leaves for six weeks to track decomposition.

The study found soil respiration was about 13 percent higher at the forest edge than in the interior, contradicting earlier research showing reduced respiration at urban edges. Moisture was about 20 percent lower at the edge, while temperature data also failed to explain the increased carbon release.

“Temperature cannot be the sole driver of respiration,” Fong said. “So, yeah, that’s the main finding, that respiration is higher at the edge compared to the interior.”

Neither root biomass nor decomposition showed a clear relationship with respiration.

The findings suggest carbon models based largely on intact forests may overlook the more complicated behavior of fragmented urban forests.

“We’re researching the reality, which is that these forests are no longer intact and they’re now fragmented,” Bernstein said.

Assessing potential sites for American chestnut restoration in Inwood Hill Park

Harrison Luterman and John Dean evaluated three locations in Inwood Hill Park to determine whether they could support the restoration of the American chestnut, once a dominant tree in forests throughout the eastern United States.

The species was nearly eliminated after chestnut blight, a fungal disease introduced from Asia in the late 1800s, spread throughout its native range. The fungus encircles the trunk and interrupts the movement of nutrients, often killing the tree above its roots.

“Billions of chestnut trees all around the eastern U.S. were reduced to just a stump, and then all their value to the ecosystem was lost,” Dean said.

Working with mentor Jasmine Bayron, the interns selected three potential planting areas in Inwood Hill Park –- a valley floor, a marsh and a ridge top. At each site, they established a 30-by-30-foot transect and catalogued the plants growing inside it. They also measured canopy density, slope and soil acidity, phosphorus, potassium and nitrogen.

None of the locations perfectly matched the American chestnut’s preferred growing conditions. All three had overly dense canopies and slopes that were too gradual. Soil tests also identified nutrient deficiencies, while the marsh site contained numerous invasive plants and vines.

Still, the interns concluded each site could be modified through pruning, fertilizer, added organic matter, improved drainage or changes to the slope. Their recommendations differed according to each location’s conditions.

“All of this research is critical,” Luterman said. “It’s just the beginning of a larger initiative for our mentor.”

The study could help guide where blight-resistant American chestnuts are eventually planted as part of broader efforts to restore the species and its ecological role.