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Outcome of surveillance of plant phenology in Yushan National Park interacted with climate change

The core value and function of a national park is to protect and manage natural resources and human assets. Among all, Yushan National Park is one of Taiwan’s three alpine-type national parks, possessing characteristics of an alpine ecosystem. Therefore, long-term investigation and surveillance of animal and plant thriving under an extremely harsh alpine climate is necessary.
In the progress of global warming and climate change, the Alps is one of the most profoundly affected ecosystems. The life cycle of alpine plants from leafing, flowering to fruiting is regularly adapted to various environments. It’s called plant phenology; Yushan National Park Headquarters (abbreviated as YSNPH) conducted a three-year based (2016~2018) phenological survey of alpine plants from flowering to fruiting in the areas along Tataka to the Yushan Main Peak Trail. This project was outsourced to a team formalized by the Forestry Department of the National Chung Hsing University to survey seed plants and flowering plants on a monthly basis. A total of 240 species were recorded. As the weather gets warmer, the number of plant species starting to bloom also increase. The peak of the number of flowering species is in the summer while the peak in the numbers of seeding plants is in November. The higher the altitude, the later the blooming and fruiting.
Global warming and dramatic climate changes are disadvantageous to plant growth, especially when there’s extremely low temperatures in the spring followed by comparatively high temperature in winter & comparatively high temperatures in autumn but then rapidly enters a severe winter. It increases the failure rate of fruiting as plants undergo low temperature during the blooming season in the former scenario; while fruits are rarely ripen because of insufficient energy stored in their bodies in the later scenario despite the later scenario extending the growing season and timeframe of blooming.
Rhododendron pseudochrysanthum is visible along the Tataka to Yushan Main Peak from an altitude of 2600 m to 3900 m in the Yushan National Park. It’s found that the blooming time of Rhododendron pseudochrysanthum varies by climate difference and is especially affected by the change of temperature through the observation of 3 years time-lapse photography shot by the research team. It’s assumed that the flower sprouts of Rhododendron pseudochrysanthum are dormant when the temperature is low in winter and then thrive and bloom when the temperature rises in the spring.

This research compares the thermal-time value of Rhododendron pseudochrysanthum grown in the glacial cirque of the Snow Mountain and Yushan area. The delta of the Main Peak altitude between Snow Mountain and Yushan is approximately 100 km, meaning that the temperature difference is close to 100 m altitude. This indicates that Rhododendron pseudochrysanthum in Yushan area requires higher thermal-time value up to 0.5~0.8 Celsius compared to similar habitat and same altitude in the Snow Mountain area. However, if the baseline temperature is 5 Celsius, the thermal-time values of Rhododendron pseudochrysanthum in both areas are similar, implying that 5 Celsius could be the baseline temperature to trigger Rhododendron pseudochrysanthum to bloom.
The trigger point of Rhododendron pseudochrysanthum blooming is affected by the temperature movement after the lowest temperature hits winter, while blooming has lowlight and highlight affected by climate factors. Long-term observation and monitoring of flowering and fruiting plant phenology are necessary in order to understand how climate changes impact the alpine ecosystem. The YSNPH will continuously engage with volunteers for a long-term recording of the blooming and fruiting of plants on trails to amplify plant phenology data chronologically.
The Rhododendron pseudochrysanthum surrounding the Tataka Trail has been blooming silently this year, starting from the low altitude then rising to the higher altitude. Stunning Rhododendron pseudochrysanthum is everywhere in the alpine area in May and June, estimated to reach its peak by the end of May. White and light pink purple flowers bring color and spring to the alps. Majority of the Rhododendron pseudochrysanthum in the alps grow on rocky and sloped areas. The YSNPH would like to remind visitors to keep to the trails to protect their own safety. Do not step out of the trails to reach out for flowers.