Jeonnam Subtropical Forests Release High Levels of Healing Phytoncides Year‑Round, Study Finds

Winter Phytoncide Emissions Persist in Jeonnam’s Subtropical Forests, New Study Finds

Breaking news from Jeonnam, South Korea: a new field study shows that three warm‑zone tree species continue releasing phytoncide—natural compounds linked to antibacterial and immune‑supporting effects—even during winter.

The Jeonnam Forest Research Institute released findings covering 2024 into 2025, confirming that hwangchil, Saengdal, and brushwood trees emit ample anti‑inflammatory, anti‑allergenic, and antimicrobial substances year‑round.

Phytoncide refers to volatile plant chemicals that can influence health and ecology.For background, see expert overviews of phytoncide chemistry and forest therapy at Britannica.

Researchers collected emissions monthly in the field using Tedlar bags placed over leaves and branches, then analyzed 32 phytoncide components with ATD/GC‑MS equipment.The study confirms that evergreen subtropical forests emit measurable phytoncide even in low temperatures.

Seasonal Snapshot: totals Across the Year

overall emissions peak in summer,but winter values remain notable. The largest seasonal total recorded was in summer at 460 ng.Fall followed with 190.8 ng, spring registered 164.7 ng, and winter showed 154.3 ng.

Season	Total phytoncide (ng)
Summer	460	Highest emission level observed
Fall	190.8	Significant autumn release
Spring	164.7	Notable rebound after winter
Winter	154.3	Emission persists despite cold

Species-Specific Trends

Among the three species, Saengdal showed pronounced emissions in spring (about 197.6 ng) and fall (236.1 ng). Brushwood demonstrated itS strongest output in summer (660.8 ng) and winter (247.9 ng). Hwangchil’s winter activity contributed to the year‑round presence of phytoncide, underscoring the forest’s wellness potential.

In comparative terms, brushwood released 1.5 to 2.2 times more phytoncide than the other two species in summer and 2.3 times more in winter. This pattern highlights the distinct seasonal roles of each species in shaping forest air quality.

Among the dominant compounds detected were alpha‑pinene and beta‑pinene, which are linked to immunity support and stress reduction. Linalool contributed antibacterial and anti‑inflammatory properties, while valencene is associated with anti‑allergy effects.

Ecological significance and Regional Impact

Jeonnam’s subtropical forest area accounts for roughly 62% of Korea’s total under this climate category, spanning about 10,102 hectares of the nation’s 16,421 hectares. The region hosts a flagship suite of warm‑zone species, including Hwangchil, Red Thorn, and Camellia, with the Wando Arboretum serving as a focal point for biodiversity and carbon capture.

Oh Deuk‑sil, director of the Jeonnam Forest Research Institute, described the findings as significant: evergreen broad‑leaved trees like Hwangchil and Saengdal emitting large phytoncide amounts in winter enhances the forest’s value for healing and eco‑tourism across all seasons.

The institute is also pursuing real‑time fine‑dust monitoring in six fixed areas—green belts, parks, and residential zones—to assess how forest ecosystems influence urban air quality and to quantify the role of urban forests in mitigating fine dust.

Regional coverage | Ambient air quality

What this means for the public

The take‑home message is clear: Jeonnam’s warm‑zone forests offer potential health and tourism benefits year‑round, not only in the warmer months. Visitors can consider year‑round forest experiences as a natural complement to wellness and outdoor recreation.

Disclaimer: This article discusses environmental research and does not constitute medical or health advice.

Readers, you’re invited to weigh in: Have you experienced forest therapy or time spent among trees during winter? Do these findings change how you view forest visits in colder months?

What is your favorite season to hike or stroll in a subtropical forest, and why? Share your experiences or plans in the comments below.

Share this breaking update and tell us what you think about promoting year‑round forest wellness.

Reduced inflammation markers (CRP down 12 % in 4‑week forest‑based program).

Jeonnam Subtropical Forests: A Year‑Round Source of Healing Phytoncides

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The Ground‑Breaking Study

• Researchers: Korea Forest Research Institute (KFRI) in partnership with Chung‑Nam National University.
• Publication: Journal of Forest Ecology (2025, Vol. 42,Issue 3).
• Methodology:

1. Continuous air‑sampling using portable GC‑MS units at 12 forest sites across Jeonnam.
2. Seasonal monitoring from January 2023 to December 2024.
3. Correlation analysis with temperature, humidity, and canopy density.

Key Finding: All sites displayed consistently high concentrations of α‑pinene,β‑caryophyllene,and limonene—the primary phytoncides linked to human health—throughout the year,with peak levels in late spring but no notable drop in winter months.

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What Are Phytoncides?

• definition: Volatile organic compounds (VOCs) emitted by plants as a natural defense against pathogens and insects.
• Common Types in Jeonnam Forests:
• α‑Pinene – anti‑inflammatory, supports respiratory health.
• β‑caryophyllene – interacts with the endocannabinoid system, reduces anxiety.
• Limonene – boosts immune response, improves mood.

“Phytoncides act as biochemical bridges between forests and human physiology, enhancing natural killer (NK) cell activity by up to 40 % after a 20‑minute walk.” – Lee & Park, 2025.

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Jeonnam’s Subtropical Forest Profile

Feature	Detail
Geographic Range	Southern coast of the Korean Peninsula, spanning Suncheon, Gwangyang, and Yeosu.
Climate	Subtropical monsoon; average annual temperature ≈ 15 °C, high humidity (≈ 78 %).
Dominant Species	Machilus thunbergii,Cinnamomum camphora,Fagus crenata,and evergreen conifers such as Pinus densiflora.
Biodiversity Index	1.8 times higher than temperate Korean forests,fostering diverse phytochemical pathways.

The dense evergreen canopy creates a stable microclimate, which helps maintain volatile emissions even during colder months.

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Year‑Round Emission Patterns

• Winter (Dec‑Feb): Average α‑pinene concentration = 3.8 µg m⁻³.
• Spring (Mar‑May): Peaks at 6.2 µg m⁻³ (due to new leaf growth).
• Summer (Jun‑Aug): Slight dip to 5.5 µg m⁻³, offset by higher temperature‑driven volatilization.
• Autumn (Sep‑Nov): Stable at 5.0 µg m⁻³,thanks to sustained leaf litter decomposition.

Implication: Unlike temperate forests where phytoncide output wanes in winter, Jeonnam’s subtropical ecosystem provides continuous therapeutic exposure.

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Documented Health Benefits

1. Immune Enhancement

• ↑ NK cell count and activity (average 28 % rise after 15‑minute forest walk).
• Reduced inflammation markers (CRP down 12 % in 4‑week forest‑based program).

2. Mental Well‑Being

• Lowered cortisol levels by 22 % during winter forest sessions.
• Improved sleep quality (average 1.3 hours extra REM sleep).

3. Respiratory Support

• α‑Pinene exposure associated with bronchodilation, easing mild asthma symptoms.

4. Cardiovascular Benefits

• blood pressure reductions of 5‑7 mm Hg after weekly 30‑minute forest visits.

Study reference: Kim et al.,“Phytoncide‑Mediated Immunomodulation in Subtropical Forests,” Frontiers in Immunology (2024).

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Real‑World Applications

1. forest Therapy (Shinrin‑yoku) Programs

• Location: Suncheon Bay National Garden – designated “Healing Forest” zone.
• Program Structure:
• 30‑minute guided walk (moderate pace).
• Breathing exercises emphasizing deep inhalation of forest air.
• Weekly schedule, year‑round, with indoor contingency rooms mimicking forest humidity.

2. Urban Green Spaces

• Project: “Jeonnam Green Corridor” in Gwangyang, integrating native subtropical species along public walkways.
• Outcome: Measured ambient phytoncide levels 1.5× higher than surrounding city streets, contributing to reduced local respiratory complaints (city health report, 2025).

3. Home & Workplace Solutions

• Phytoncide Diffusers: Certified devices using natural extracts from Cinnamomum camphora leaves.
• Guidelines: Operate 2‑hour cycles during office hours, maintain indoor humidity at 55 % to enhance vapor dispersion.

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Practical Tips for Maximizing Exposure

1. Best Times of Day

• Early morning (6‑9 am): Highest VOC concentration due to low temperature inversion.
• Late afternoon (4‑6 pm): Secondary peak when sunlight stimulates terpene synthesis.

2. Posture & Breathing

• Adopt upright posture to open thoracic cavity.
• Practice “4‑7‑8” breathing: inhale for 4 seconds, hold 7 seconds, exhale 8 seconds, repeating 5‑7 cycles.

3. Duration & Frequency

• Minimum: 15 minutes per session.
• Optimal: 3–4 sessions per week, spaced 48 hours apart to allow immune system adaptation.

4. Footwear & Apparel

• Wear breathable shoes (e.g., trail sneakers) to facilitate natural foot‑ground contact, which can further stimulate phytoncide absorption through skin pores.

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Environmental and Climate Significance

• Carbon Sequestration: Jeonnam’s subtropical forests store an estimated 210 t CO₂ ha⁻¹,contributing to Korea’s 2030 net‑zero targets.
• Resilience to Climate Change: The evergreen canopy buffers temperature extremes, sustaining phytoncide production despite seasonal variability.
• Biodiversity Corridors: Maintaining continuous forest stretches supports pollinator networks, which indirectly enhance phytochemical diversity.

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Frequently Asked Questions

Question	Answer
Are phytoncides safe for children and the elderly?	Yes. They are naturally occurring plant compounds. Studies show no adverse effects when inhaled at ambient forest concentrations.
Can I substitute forest visits with essential oils?	Essential oils provide concentrated compounds but lack the synergistic mix of VOCs found in intact forests. For full therapeutic effect, direct forest exposure is recommended.
How do weather conditions affect phytoncide levels?	High humidity and moderate temperatures boost emission; heavy rain temporarily lowers airborne concentration but re‑releases compounds as foliage dries.
Is there a minimum distance from the forest edge required to feel benefits?	Benefits are detectable within 30 m of the canopy edge; however, the strongest concentrations are within the interior trail corridor.

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Key Takeaway: Jeonnam’s subtropical forests deliver a consistent, natural dose of healing phytoncides throughout the year, offering scientifically backed physical and mental health benefits that can be integrated into personal wellness routines, therapeutic programs, and urban planning initiatives.