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As the 2024 field season draws to a close, we reflect on the milestones and achievements that have marked this productive period. This summer, our dedicated team of three research technicians made remarkable strides in our ongoing data collection efforts, showcasing their expertise and commitment. In addition to collecting data on tree seed, seedling, sapling, and overstory dynamics, the technicians completed independent research projects utilizing publicly accessible datasets collected at the Holt Research Forest. On August 1, 2024, the technicians presented their projects and findings to the Maine TREE Staff, Board of Directors, and Holt Research Forest Committee to celebrate their accomplishments and hard work. The afternoon was filled with discussions about harvest impacts on forest composition, tree mortality and recruitment, and salamanders! Read below to learn more about the technician’s projects and findings.
Gursimran Sahota presented “Long-Term Forest Dynamics and Regeneration Patterns in Holt Research Forest: A Study of Post-Harvest Changes.”
Long-term forest dynamics and regeneration patterns at Holt Research Forest: A study of post-harvest changes
Gursimran Sahota, a master's student at Northeastern University studying bioinformatics with a concentration in data analytics, analyzed forest dynamics at HRF, focusing on growth rates, relative abundance, and basal area for four common tree species (white pine, red spruce, balsam firm, and red maple) in response to the 1988 timber harvest. Using the timber inventory and seedling regeneration datasets, Gursimran found that harvesting had varying effects on regeneration and overstory patterns. Seedlings, specifically white pine and red maple, were significantly more abundant following the 1986-1987 harvest. Furthermore, harvesting did not significantly impact mature tree growth rates, however, mature red maples were more abundant in the east and mature red spruce was more abundant in the west (Figure 1). This study offers insights into the long-term trends in forest regeneration and composition, particularly following disturbances like timber harvests.
Figure 1. Relative abundance of red maple and white pine seedlings by harvest period. Relative abundance of seedlings and saplings for red maple (a) and white pine (b) across different time periods (pre-harvest, post-harvest, late post-harvest) in Holt Research Forest. Bars represent data from eastern and western blocks. Significant differences in relative abundance were observed across periods for red maple (p = 0.048) and white pine (p < 0.001).
Toby Ouellette presented “Mortality and Recruitment Rates Pre and Post Timber Harvest in the Holt Research Forest.”
Mortality and recruitment rates pre- and post-timber harvest at the Holt Research Forest
Toby Oullette, an undergraduate student at the University of Maine studying ecology and environmental sciences with a concentration in forest ecosystem ecology, investigated the impacts of the 1988 timber harvest on mortality and recruitment for dominant tree species at HRF. Toby used complete and partial timber inventory data to determine that mortality rates did not significantly differ pre- and post-harvest (Table 1). In 1984 (pre-harvest), the forest recorded 322 more recruitment trees, those greater than or equal 9.5 cm in diameter, than in 1988 (post-harvest). These results suggest that the timber harvest did not impact tree mortality and recruitment and could be used to inform future management practices for other coastal oak-pine forests.
Table 1. Mortality rate percentages for the 10 studies species by year.
Olivia Case presented “Predicting Plethodon cinereus Abundances at the Holt Research Forest.”
Predicting Plethodon cinereus abundances at the Holt Research Forest
Olivia Case, an undergraduate student at The Pennsylvania State University studying forest ecosystem management with a concentration in forest biology, used salamander count data to predict future populations of redback salamanders at HRF. With groundcover and shrub data collected in 1994, Olivia created a multiple linear regression model including the most significant environmental variables to predict future redback salamander populations. Although there were differences between the observed and predicted populations of future redback salamanders, the significant predictor values included in the model aligned with known salamander habitat and resource preferences, specifically the presence of coniferous, deciduous, and mixed dry litters, which are known to host a variety of invertebrates commonly eaten by redback salamanders (Figure 2). The findings of this study highlight the importance of continuity and accessibility in data collection and presents information related to wildlife habitat conditions at HRF.
Figure 2. A bar graph comparing the summed P. cinereus abundances that were observed in 1994,
observed in 2011, and predicted in 2011. The summed observed abundance from 1994 was 876, the
summed observed abundance from 2011 was 462, and the summed predicted abundance in 2011 was
781.5. Salamander abundance decreased by 47% between 1994 and 2011.
To read more about the technician’s research and experiences check out these articles from our monthly Seedlings newsletter!
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