This study aimed to comprehensively investigate the thermal comfort and physiological and psychological effects according to tree density in forest environments during rest and during and after physical activities in the summer. Participants consisted of 18 male university students (average age: 24.0 ± 1.6 years old), and a within-subjects experimental design was used. Participants sat on a chair for 5 min to rest, performed a step-box exercise for 8 min, and then sat on the chair again, and rested for 10 min in a forest with high tree density (85.6%) and one with low tree density (12.2% as a control). Thermal comfort (predicted mean vote; PMV and percentage of dissatisfied; PPD) and physiological and psychological responses were measured. We investigated and analyzed the changes in “rest”, “during exercise”, and “after exercise”. As a result, a forest with high tree density showed a statistically significant decrease in PMV and PPD values; an increase in parasympathetic nervous activity; a decrease in respiratory rate, systolic blood pressure, and pulse rate; an improvement in mood state; an increase in comfortable, relaxed, and natural feelings; and more of an increase in personal thermal sensation during the recovery period after physical activities than in a forest with low tree density. In conclusion, a forest with high tree density during recovery after physical activities in the summer has higher thermal comfort and physiological and psychological relaxation effects on humans, as compared to one with low tree density.

Background and objectives: Forest environments provide various healing benefits for humans and have been widely studied. Nevertheless, the field of forest management for forest healing remains relatively understudied. The purpose of this study is to utilize thermal environmental simulation to derive forest management scenarios that are optimized for forest healing. Methods: This study focused on the Seogwipo Experimental Forest on Jeju Island, Korea. Three-dimensional forest models were generated based on field surveys. Thermal environment simulations were conducted using Grasshopper with the Ladybug and Honeybee plug-ins, and the thermal comfort levels of six forest management scenarios were evaluated using the Universal Thermal Climate Index (UTCI). Results: The simulation results showed that, among all the scenarios, only scenario (c), “10% thinning in the buffer zone”, led to an improvement in thermal comfort. Additionally, the study identified discrepancies in thermal comfort between different forest management scenarios. Conclusions: In the management of forests for healing forestry purposes, the distinction of forest zones by use and the application of different forest management scenarios have thermal comfort implications. Thus, the methodology could be employed in forest management for forest healing purposes.

Research highlights: The increasing rates of mental health disorders during the COVID-19 pandemic have popularized the notion of access to natural environments as a solution, leading to a surge in demand for urban green spaces. The concentration of natural volatile organic compounds (NVOCs) in forests, resulting from plant metabolism, plays a crucial role in forest-based healing and ecosystem health. Background and objectives: This study aimed to investigate how tree spacing influences NVOC concentrations within forest ecosystems using passive samplers, thereby enhancing the understanding of optimal forest management practices to promote human health benefits. Methods: We employed passive samplers to investigate tree spacing effects on NVOC concentrations. We placed passive samplers among trees in the study area to measure NVOC concentrations in individual trees and analyzed the relationship between NVOC concentration and tree spacing and structure. Results: A multiple regression analysis using distance decay models showed that a tree spacing of 2.7–3 m had a significant impact on NVOC concentrations. These findings provide a better understanding of how tree structure, tree spacing, and microclimate within the forest influence NVOC concentration. Conclusion: These findings have important implications for forest management and the design of forest landscapes to promote human health and well-being by considering the spatial distribution of NVOC concentrations.

Urban heat island conditions increase heat exposure and constrain safe outdoor activities. Urban forests can mitigate thermal loads; however, stand morphology can produce divergent microclimates. We aimed to quantify how stand type (open vs. closed), season (spring, summer, fall), and activity intensity (MET 1.0–6.0) jointly modulate thermal comfort and to identify season-specific optimal MET levels in an urban forest in Daejeon, Republic of Korea. We combined site-specific 3D canopy modeling with hourly Predicted Mean Vote (PMV) simulations driven by AMOS tower data (2023–2024). Comfort was defined as |PMV| ≤ 0.5. Analyses included seasonal means, Cliff’s delta, and generalized estimating equation logistic models to estimate the SITE × SEASON × MET interactions and predict comfort probabilities. Across most seasons and MET levels, C1 was more comfortable than C2. However, at MET 1.0 in summer, the pattern was reversed, which may reflect the canopy shading and associated decreases in mean radiant temperature (MRT) of C2. Comfort peaked at MET 2.0–3.0 and declined sharply at ≥4.5 MET. The three-way SITE × SEASON × MET interaction was significant (p < 0.001). The season-specific optimal MET values under our boundary conditions were 3.0 (spring), 2.0–2.5 (summer), and 3.0 (fall). These simulation-based PMV-centered findings represent model-informed tendencies. Nevertheless, they support actionable guidance: prioritize high-closure stands for low-intensity summer use, leverage open stands for low-to-moderate activities in spring and fall, and avoid high-intensity programs during warm periods. These results inform the programming and design of urban-forest healing and recreation by matching stand type and activity intensity to season to maximize comfortable hours.