Spring comes earlier, autumn foliage later as climate change alters forests

Korea’s forests are showing earlier spring growth and later autumn foliage as temperatures rise, with this year’s peak colors forecast for late October and early November. Studies tracking Korean trees found that spring development advanced while autumn color changes were delayed, lengthening the average growing season by more than 17 days from 2009 to 2024. Researchers say the shifts may affect carbon storage, understory plants and trees’ preparation for winter, and call for long-term monitoring to guide forest management.

The Korea Forest Service forecast peak foliage for Oct. 28 at Mount Songni, Nov. 4 at Mount Naejang and Nov. 6 at Mount Halla.

A 2021 study tracking 25 native plant species found that broadleaf trees’ leaf emergence advanced by 13 days over a decade, while autumn foliage onset was delayed by 3.7 days.

Researchers estimated that a 1-degree Celsius rise in average spring temperatures advanced leaf emergence by 3.6 days, while the same rise in autumn temperatures delayed fall foliage by 1.5 days.

A study of 20 deciduous broadleaf species at 10 arboretums found that from 2009 to 2024, leaf buds burst 0.94 days earlier per year on average and flowering began 0.83 days earlier per year.

The study defined peak autumn foliage as the period when 90 percent to 100 percent of leaves had changed color.

Published Oct 24, 2026 12:05 am KST

Participants in the Walk the Road to Mount Kumgang event stroll along a trail ablaze with autumn colors in the Dutayeon area of Yanggu County, Gangwon Province, Oct. 15. Yonhap

If you are planning a fall foliage trip this year, you may need to set off a little later than expected. The peak autumn foliage season is forecast to arrive later than usual.

According to the Korea Forest Service, fall colors will spread gradually from the central to southern regions, starting with Mount Seorak on Oct. 20. Foliage is expected to reach its peak nationwide only in late October, with peak dates forecast for Oct. 28 at Mount Songni, Nov. 4 at Mount Naejang and Nov. 6 at Mount Halla.

The average peak date for maples and oaks nationwide is expected to be Oct. 31, about 0.8 days later than the average peak date over the past five years.

The delayed foliage season is not an isolated development this year. As temperatures rise, spring is arriving increasingly early while autumn is shifting later, a pattern that researchers have consistently observed in Korea's forests. The seasonal clock that we have long taken for granted is changing.

A 2021 study by researchers at the Korea National Arboretum and Seoul National University’s Graduate School of Environmental Studies tracked 25 native plant species in Korea over a decade. It found that the timing of leaf emergence in broadleaf trees had advanced by 13 days over the 10-year period, while the onset of autumn foliage had been delayed by 3.7 days.

The researchers estimated that a 1-degree Celsius rise in average spring temperatures advanced leaf emergence by 3.6 days, while a 1-degree increase in average autumn temperatures delayed fall foliage by 1.5 days.

A pedestrian walks along a ginkgo-lined street in Unridan-gil, Heungdeok District, Cheongju, North Chungcheong Province, Saturday. Yonhap

Extending the observation period has made the changes even more apparent.

A study titled “Long-Term Changes in Plant Phenology in Korea (2009-2024),” published last year in the Korean Meteorological Society’s journal Atmosphere, analyzed seasonal changes in 20 deciduous broadleaf tree species observed at 10 arboretums nationwide.

From 2009 to 2024, leaf buds burst an average of 0.94 days earlier each year, flowering began 0.83 days earlier and leaves unfolded 0.79 days earlier. In other words, spring plant development advanced by roughly 13 to 15 days over the 16-year period.

By contrast, the peak autumn foliage period — when 90 percent to 100 percent of leaves have changed color — was delayed by an average of 0.33 days each year, shifting approximately five days later over the same period.

As a result, the growing season for trees — the period from when leaves emerge in spring until they change color in autumn — lengthened by more than 17 days on average.

“This shows that the seasonal clock of forests is changing, with spring arriving earlier and autumn coming later,” said Jung Soo-jong, a professor at Seoul National University’s Graduate School of Environmental Studies.

Longer growing season: Good for carbon absorption?

Is a longer growing season good for forests? With leaves remaining active for longer, trees have more time to photosynthesize and potentially absorb carbon.

However, a forest's capacity to absorb and store carbon cannot be assessed solely by how long trees photosynthesize. Soil also stores substantial amounts of carbon, and rising temperatures can stimulate microbial activity in the soil, potentially increasing carbon dioxide emissions. The amount of carbon absorbed through photosynthesis also depends on temperature and water availability, not just the length of the growing season.

“Carbon absorption capacity is determined by the balance between plant photosynthesis and carbon emissions from the soil, as well as factors such as drought and extreme weather events,” said Noh Nam-jin, a professor in the Department of Forest Resources at Kangwon National University.

More complex changes are also taking place within forests.

“When leaves emerge earlier in spring, the canopy of taller trees may become dense before understory plants — small plants growing on the forest floor — that bloom briefly in early spring have had enough time to complete their life cycles,” said Park Pil-sun, a professor in the Department of Forest Sciences at Seoul National University.

The leaves of taller trees block sunlight, potentially preventing understory plants from producing fruit properly, she explained.

Cheona Valley, a popular spot for viewing autumn foliage on Mount Halla / Courtesy of Jeju Special Self-Governing Province

A later autumn is not necessarily beneficial, either. After completing their growth, trees begin preparing for winter. If they do not have enough time for this process, they may become more vulnerable to severe cold.

“In a country like Korea, where the four seasons are distinct, a shorter period of preparation for winter weakens trees’ tolerance to low temperatures,” said Kim Hyun-jun, a professor in the Department of Forest Resources at Chonnam National University.

This is one reason why a simplistic response, such as indiscriminately introducing subtropical tree species, is not viable. Subtropical climates are generally defined by having an average temperature of 18 degrees Celsius or below in the coldest month and at least eight months with average monthly temperatures of 10 degrees or higher.

The problem is that researchers still do not fully understand how these changes will affect forests. A delay of several days in peak foliage is not simply a matter of adjusting the dates of autumn trips. The growth cycles of plants and their preparations for winter are changing as well.

The effects of climate change are also not driven by rising temperatures alone. Multiple factors, including droughts, torrential rain and strong winds, interact in complex ways, making it difficult to assess the overall impact through short-term observations.

Researchers have recently warned that “the climate is changing faster than we can monitor it,” Kim said.

That makes it all the more important to collect and maintain long-term data across multiple indicators. Noh emphasized the need to monitor soil carbon emissions, air temperature, precipitation, soil temperature and soil moisture together over extended periods.

The accumulated data should also be used to guide forest management.

“Rather than applying a uniform management approach nationwide, we need to closely monitor seasonal changes by tree species and region,” Jung said, adding that stable, long-term observations are essential to strengthening forests’ resilience to climate change.

This article from the Hankook Ilbo, the sister publication of The Korea Times, is translated by a generative AI system and edited by The Korea Times.

随着气温升高，韩国森林春季生长提前，秋季变色推迟，预计今年的最佳赏叶期将在10月下旬至11月初。追踪韩国树木的研究发现，春季生长提前，而秋季变色推迟，导致2009年至2024年间平均生长季延长超过17天。研究人员表示，这种变化可能会影响碳储存、林下植物和树木的越冬准备，并呼吁开展长期监测以指导森林管理。

韩国林业厅预测松里山、内藏山和汉拿山的赏叶高峰期分别为10月28日、11月4日和11月6日。

2021 年一项追踪 25 种本土植物的研究发现，阔叶树的叶子萌发期在十年间提前了 13 天，而秋季树叶变色期则推迟了 3.7 天。

研究人员估计，春季平均气温每升高 1 摄氏度，树叶萌发时间就会提前 3.6 天；而秋季气温每升高 1 摄氏度，树叶变色时间就会延迟 1.5 天。

一项对 10 个植物园的 20 种落叶阔叶树种进行的研究发现，从 2009 年到 2024 年，叶芽平均每年提前 0.94 天萌发，开花平均每年提前 0.83 天开始。

该研究将秋季树叶变色高峰期定义为 90% 至 100% 的树叶变色的时期。

发布于2026年10月24日凌晨12:05（韩国标准时间）

10月15日，在江原道杨口郡斗泰渊地区，参加“徒步金刚山”活动的游客们沿着秋色斑斓的步道漫步。（韩联社）

如果您今年计划赏秋叶，可能需要比预期晚一些出发。预计今年的赏叶高峰期会比往年来得晚。

据韩国林业厅称，秋色将从韩国中部逐渐向南部蔓延，最早于10月20日出现在雪岳山。预计全国范围内的秋叶观赏高峰期要到10月下旬才会到来，其中松里山的观赏高峰期预计为10月28日，内藏山为11月4日，汉拿山为11月6日。

全国枫树和橡树的平均盛花期预计为 10 月 31 日，比过去五年的平均盛花期晚约 0.8 天。

今年树叶变色季节的推迟并非个例。随着气温升高，春天来得越来越早，秋天来得越来越晚，研究人员在韩国的森林中一直观察到这种趋势。我们习以为常的季节更替正在发生变化。

2021年，韩国国立植物园和首尔国立大学环境研究生院的研究人员进行了一项研究，追踪了韩国25种本土植物长达十年的变化。研究发现，阔叶树的展叶时间在十年间提前了13天，而秋叶变色的时间则推迟了3.7天。

研究人员估计，春季平均气温每升高 1 摄氏度，树叶萌发时间就会提前 3.6 天；而秋季平均气温每升高 1 摄氏度，树叶变色时间就会延迟 1.5 天。

周六，一名行人走在韩国忠清北道清州市兴德郡云丹路上一条两旁种满银杏树的街道上。（韩联社）

延长观察期使这些变化更加明显。

去年发表在韩国气象学会期刊《大气》上的一项题为“韩国植物物候的长期变化（2009-2024）”的研究，分析了全国 10 个植物园中观察到的 20 种落叶阔叶树的季节变化。

从2009年到2024年，叶芽萌发平均每年提前0.94天，开花期提前0.83天，叶片展开期提前0.79天。换句话说，在16年间，春季植物发育提前了大约13到15天。

相比之下，秋季树叶变色高峰期（90% 至 100% 的树叶变色）平均每年推迟 0.33 天，在同一时期内大约推迟 5 天。

因此，树木的生长季（从春天树叶萌发到秋天变色的时期）平均延长了 17 天以上。

“这表明森林的季节时钟正在发生变化，春天来得更早，秋天来得更晚，”首尔大学环境研究研究生院教授郑秀钟（Jung Soo-jong）说。

生长季延长：有利于碳吸收吗？

生长季延长对森林有利吗？树叶保持活跃状态​​的时间越长，树木就有更多的时间进行光合作用，并有可能吸收碳。

然而，森林吸收和储存碳的能力不能仅仅根据树木光合作用的时间长短来评估。土壤也储存着大量的碳，而气温升高会刺激土壤中的微生物活动，从而可能增加二氧化碳的排放。通过光合作用吸收的碳量还取决于温度和水分供应，而不仅仅是生长季的长度。

“碳吸收能力取决于植物光合作用与土壤碳排放之间的平衡，以及干旱和极端天气事件等因素，”江原大学森林资源系教授卢南镇说。

森林内部也在发生更复杂的变化。

“如果春天早些时候树叶就长出来了，那么在早春短暂开花的林下植物（生长在森林地面的小植物）完成其生命周期之前，较高树木的树冠可能会变得茂密，”首尔国立大学森林科学系教授朴弼善说。

她解释说，高大树木的叶子会阻挡阳光，可能会妨碍林下植物正常结果。

天那溪谷，汉拿山赏秋胜地 / 图片由济州特别自治道提供

秋季来得晚也未必有利。树木完成生长后，便开始为过冬做准备。如果它们没有足够的时间完成这个过程，就更容易受到严寒的侵袭。

“在韩国这样四季分明的国家，冬季准备期缩短会削弱树木对低温的耐受力，”全南国立大学森林资源系教授金贤俊说。

这就是为什么像不加选择地引进亚热带树种这样简单粗暴的应对措施不可行的原因之一。亚热带气候通常定义为：最冷月的平均气温为18摄氏度或以下，且至少有八个月的平均气温为10摄氏度或以上。

问题在于，研究人员仍未完全了解这些变化将如何影响森林。秋季赏叶高峰期延迟数日并非仅仅是调整秋季旅行日期的问题。植物的生长周期及其越冬准备也在发生变化。

气候变化的影响并非仅仅由气温上升造成。干旱、暴雨和强风等多种因素相互作用，错综复杂，因此难以通过短期观测评估其总体影响。

金说，研究人员最近发出警告，“气候变化的速度比我们监测的速度还要快”。

因此，收集和维护多个指标的长期数据就显得尤为重要。卢强调，需要长期综合监测土壤碳排放、气温、降水、土壤温度和土壤湿度。

积累的数据还应用于指导森林管理。

Jung表示：“与其在全国范围内采用统一的管理方法，我们更需要密切监测不同树种和地区的季节性变化。”他还补充说，稳定、长期的观测对于增强森林应对气候变化的能力至关重要。

本文来自《韩国日报》（《韩国时报》的姊妹报），由人工智能生成系统翻译，并由《韩国时报》编辑。