The Impact of Global Warming on the Alpine Plants of Hallasan

Woo-Seok Kong

Department of Geography, KyungHee University, Seoul, 130-701, Korea

(wskong@khu.ac.kr)

1. Introduction

Many people are concerned about the possible ecological effects that are associated with global climate change. There are positive and negative economic impacts concerning global warming. It has been predicted that some areas of the world such as northern Canada, Central Africa, and Central Asia could see an increase in their growing seasons because of either warmer temperatures or more precipitation. This would produce larger crop yields for these nations. It has also been speculated that increased CO2 levels may allow plants to grow more rapidly. The negative side of this scenario is that other nations will be dealing with severe drought conditions or be inundated with water due to the rising sea levels. Present works aim to understand the probable impact of climatic warming on the alpine plants of Hallasan, which are sensitive to global warming.

2. Environment of Hallasan

Hallasan (Mt. Halla) rises in the centre of Chejudo (Cheju Island) as a highest in the Republic of Korea stretching out to the east and west. At 1,950 metres above sea level (m a.s.l.), Hallasan is Republic of Korea (South Korea)'s highest peak. At the summit of Hallasan, at 1,950m a.s.l., is a large crater, Paeknokdam (700 x 400m, 210,230 square metres; the White Deer Lake, in Korean translation). From the layering and formation of its rock, it reveals several dozen periods of volcanic activity (from as far back as 10 million years), which have left crusted lava beds, jagged outcrops, geometric basalt columns, and lava tubes. Hallasan's last eruption was in 1007, and while generally considered extinct.

Hallasan's east, west, and north sides ascend gently. The steeper and more weathered south side stood through millennia as a bastion against the hot, humid, and sometimes violent summer weather. A crater atop the mountain holds Paeknokdam, R. O. K.'s only natural lake, which swells during the summer rains but shrinks to nothing for the rest of the year. Paeknoktam is well known for its legend that an unworldly man descended from heaven and played with white deers. Walking around a large volcanic lake Paeknoktam that measures 2,000 metres in circumference and 100 metres deep.

3. Climate of Hallasan

Chejudo is said to have subtropical marine climate, but it is definitely has four distinct seasons. The temperature is warmer on average than the Korean Peninsula by 2 to 4℃. An important factor contributing to the higher temperatures is the warm Kuroshio Current and accompanying air, which push up in summer from the Philippines. Chejudo has an average temperature of about 15℃ (in summer the temperatures range 23 to 27℃, while winter gets cold 3 to 7℃) and the humidity, at 71 to 74%, is slightly higher than in the rest of the country.

Due to its extremes in elevation, Chejudo also has widely divergent climatic zones, from the subtropical south coast through the temperate mountain slopes to the alpine zone at the mountain summit. The peak's average temperature is 5℃, and for long periods in winter it drops well below freezing, even down to -25℃ when wind sweep across the Yellow Sea (West Sea) from Manchuria picking up moisture, lay in a layer of cloud at about 700 m a.s.l., and drop great amounts of snow on the mountain. The island also has a high degree of average precipitation. Most of its more than 1,400mm comes during the summer rainy season (on average, about 500mm in July alone), but some falls as winter snow on the mountain.

Hallasan is capped from December through April, but many receive snow as early as October and as late as May. Although light rains occur in spring, the heavy monsoon rains start in the beginning of June and last well into August. Sogwipo and the south-central coast receive the greatest amount. Temperature rise at their onset, but it is seldom muggy because of freshing sea breezes. Few of Asia's seasonal typhoons make it as far north as Chejudo, but often the associated weather does. Strong winds and heavy rains cause crop damage and high seas, and interrupt ferry traffic.

Weather at the mountain top is extremely fickle. A bright clear morning may easily turn into a downpour by afternoon, or a misty morning chill may burn off by midday. It's exceptional when the mountain is clear from morning till evening. On the average, the summit can be seen only one in ten.

With respect to climate and vegetation Chejudo has a transitional character. Since Chejudo is an outpost of Korea reaching far southward into the warm sea, it has the least continental climate of the entire country. Chejudo is simultaneously the only part of Korea in which the average minimum temperatures of the winter months do not drop below the freezing point. Chejudo has an annual average of only 18 days each with frost and snowfall.

4. Vegetation of Hallasan

Hallasan's rocky top gives way to thickly forested slopes of evergreen and deciduous trees gouged by prominent valleys. Below the mixed forest spreads open grassland which carpets the vast rolling lower elevations. In general, coastal vegetation is found up to 50m a.s.l., grassland to 600m a.s.l., the deciduous broad-leaved forest to 1,100m a.s.l., and evergreen coniferous forest to 1,500m a.s.l., with alpine vegetation above that.

Floristic diversity and high endemicity of Hallasan may due to ; first, the long term isolation of island and summit from the Korean Peninsula since the Pleistocene, secondly, wide range of local environmental conditions (topography, climate, soil, vegetation, landscape etc.) provided, and finally the absence of catastrophic environmental change in the past which ensured the survival of diverse floristic and vegetational elements.

Hallasan is characterised by an extremely impressive altitudinal zonation of its vegetation. Four main altitudinal belts, a subtropical one, a temperate one, a subalpine one and alpine one are separated from each other approximately by the 600, 1,300 and 1,800 metres contour lines.

The region belonging to the subtropical zone is the site of intensive agriculture and grazing. The lower subdivision is characterised by a predominance of evergreen plants. On the shorelines of Chejudo, more than 70 species of broad-leaved evergreens grow. The southern coast and the offshore islands of Chejudo is region where warm-temperate plants grow abundantly. Many evergreen plants growing in the southern parts are identical or similar to those found in the southwestern part Japan.

Because of the more favourable winter climate on the south side, it extends high up there, to approximately 400 m a.s.l., and the evergreen plants develop into sturdy trees as much as 20 metres tall with dense foliage. On the north the same species often form only thin stemmed little trees. The climate appears to be least favourable for evergreen plants in the northwest, since this part of the coast is most strongly exposed to the winter monsoon winds.

In the upper subtropical belt (bamboo zone) evergreen species, such as camellia, occur everywhere only as shrubs and small trees, and summer-green woody plants predominate. They include several oaks and the Korean willow. The only frequent conifer in this and the following subzone is the black pine (Pinus thunbegii). red pine (Pinus densiflora) stands are often severely damaged by the pine bug (Gastropacha pini) in an unbelievably short time. The pure black pine forests found on the coastal fringe of southern Korea are hardly affected because their needles are so thick and hard.

The temperate belt, which is preserved in its full expanse as more or less virgin forest, consists of a varied summer-green deciduous forest, similar in composition to that on the southern Korean mainland. Sporadic evergreen shrubs, such as Daphniphyllum macropodum, very common even on the north side, penetrate into the lower temperate zone (Styrax zone), which extends to about 1,300 m. a.s.l.

Otherwise this forest is composed exclusively of often very good-sized summer-green deciduous trees, with lianas entwined about them and covered with epiphytes. Formerly, stands of the hornbeams (Carpinus laxiflora and Carpinus tschonoskii) belonged to this zone. Most have been felled to cultivate the edible mushroom on the rotting trunks. In the upper temperate zone (oak zone) warmth-tolerant evergreen elements are completely lacking. The summer-green deciduous trees of the previous subzone extend more or less far up into it.

Subalpine belt occurs in the northern part of Korea and on high mountains, including Hallasan more than 1,800 metres high, where the mean annual temperature is 5℃. Typical of these locations are such needle-leaved trees as Korean fir (Abies koreana), yew (Taxus cuspidata), and deciduous trees such as oaks (Quercus mongolica, Q. dentata), birch (Betula ermanii, B. costata), willow (Salix myrtilloides var. mandshurica), and so on.

Korean endemic fir (Abies koreana) occurs at Mts. Dukyoosan, Chirisan, Moodungsan, and Kayasan of the Peninsula. It grows from 1,300 m a.s.l. to the peak of Hallasan and different types of dead trunks of Korean fir create unique subalpine landscape.

At 1,800m. a.s.l., on the north side of the conifers begin to take over in a rapid transition by alpine plants. Alpine plants of Hallasan include Juniperus chinensis var. sargentii, Empetrum nigrum var. asiaticum, Diapensia lapponica subsp. obovata, Vaccinium uliginosum, and so on.

These species are regarded as a relic species, its present location resulting from the climatic change which presumably occurred in the Quaternary period. Empetrum nigrum var. asiaticum grows in the northernmost regions and the southern end of Hallasan, while Diapensia lapponica subsp. obovata is found on Hallasan and in Japan.

5. Alpine Plants of Hallasan

The Korean Peninsula at present contains c. 340 species of alpine plants (100%). Out of those the number of alpine plants in Republic of Korea is 130 species (38%), Hallasan in the southern island 81 species (24%), 54 species at Chirisan of south and 67 species at Soraksan of mid-land.

The alpine plants of Hallasan can be divided into eight groups based upon their horizontal and vertical distributions, and include ① species solely grow on Hallasan (15 spp.) ② species common to northern Korea and Hallasan (14 spp.) ③ species common to Soraksan and Hallasan (5 spp.) ④ species common to Chirisan and Hallasan (7 spp.) ⑤ species common to Soraksan, Chirisan and Hallasan (40 spp.) ⑥ species which are endemic to Hallasan or Korea (27 spp.) ⑦ species common to numerous Korean mountains and Hallasan (22 spp.) ⑧ species common to Japan and Hallasan (6 spp.).

Alpine plants which are solely found on Hallasan in Korea consist of 15 species, such as Salix blinii, Potentilla matsumurae, Bistorta suffulta, Diapensia lopponica subsp. obovata, Silene fasciculata, Vaccinium japonicum, Acontium napiforme, Gentiana chosenica, Ranunculus erucilobus, Anaphalis sinica subsp. morii, Arabis serrata var. hallaisanensis, Cirsium rhinoceros, Rosa taquetii, Tofieldia fauriei and Allium taquetii.

Alpine plants which are disjunctive to North Korea and Hallasan contain 11 species, i.e., Dianthus superbus var. speciosus, Empetrum nigrum var. japonicum, Ranunculus borealis, Pedicularis virticillata, Sanguisorba alpina, Adenophora lilliflora, Trifolium lupinaster var. alpina, Senecio obatus, Pternopetalum tanakae, Carex tenuiformis and Cnidium tachyroei.

Alpine plants which are common to Soraksan and Hallasan include 5 species i.e., Aquilegia oxysenala, Geranium duricum, Vaccinium uliginosum, Scabiosa japonica and Adenophora radiatifolia.. Alpine plants which are common to Chirisan and Hallasan consist of 7 species Caltha gracilis, Betula ermanii var. parvifolia, Vicia boissieuana, Thymus quinquecostatus, Veratrum grandiflorum, Aletris fauriei and Agrostis canina..

Alpine plants which grow on Soraksan, Chirisan and Hallasan contain 41 species such as Juniperus chinensis var. sargentii, Salix hallaisanensis, Betula ermanii var. acutifolia, Rhododendron brachycarpum, R. fauriae var. roseum, R. tschnoskii, Leontopodium coreanum and etc.

Endemic herbaceous alpine plants in the crater of Hallasan consist of 16 species, including Aconitum napiformae, Geranium skikokianum var. quelpartense, Cirsium rhinoceros, Taraxacum hallaisanensis and so on.

Endangered alpine plants on th summit of Hallasan reach up to 19 species and include Diapensia lapponica subsp. obovata, Leontopodium japonicum, Vaccinium uliginosum, Empetrum nigrum var. japonicum, Lonicera caerulea var. emphyllocalyx, Tofieldia fauriei, Aquilegia japonica, Euphobia fauriei, Pedicularis verticillata, Astragalus nakaiana, Trifolium lupinaster var. alpinum, Anaphalis sinica var. morii, Chrysanthemum zawadskii spp. coreanum, Adenophora coronopifolia, Scabiosa mansensis for. alpina, Hosta minor, Geranium modesta, G. jesana and Gymnadenia conopsea.

6. Alpine Plants of Hallasan and Past Environments

The presence of large number of alpine flora on Hallasan must primarily be attributed to historical factors, since it can not be wholly explained by reference to present environmental conditions. Seventy per cents of the alpine plants of Hallasan, which occur both in the Korean Peninsula and Japanese Islands may indicates the previous floristic connections between two areas in the past, probably through the former land-bridge.

The alpine flora of Hallasan are evidently descended from immigrants from Northeast Asia via the Korean Peninsula and eventually moved down to the Japanese Isles during the epoches of the Ice Age. These plants, which are very intolerant of competition, have been able to persist in alpine area thanks to their harsh climatic conditions, sterile soil, rugged topography and cryoturbation. Current distributional ranges of arctic-alpine and alpine plants on Hallasan are confined to near its summit.

There are also large number of fauna indicative of the presence of land connection in the past between the Korean Peninsula and Chejudo. These include fauna which are known to occur on Chejudo as the southernmost distributional limit of many animal in Korea, such as amphibians (Bombina orientalis, Kaloula borealis, Rana dybowskii, R. plancyi), reptiles (Elaphne dione, E. rufodorsata, Agkistrodon calinosus, Takydromus wolteri), as well as fossil mammals (Ursus arctos var. laciotus, Sus scrofa var. coreanus, Cervus nippon var. manchuricus, Caprelous pygargus).

7. Alpine Plants of Hallasan and Global Warming

Alpine plants, which are very intolerant of competition under mild environment, have been able to persist in alpine belts thanks to their harsh climatic conditions, sterile soil, rugged topography and cryoturbation.

The lapse rate of temperature on Hallasan based upon the my observation from 1995 to 1997 at the altitudes of 1,700 and 1,900m a.s.l. marked -0.58℃/100m for daily mean temperature, -0.53℃/100m for daily maximum temperature, -0.62℃/100m for daily minimum temperature.

The limits of some alpine species of Hallasan seem to coincide with the daily maximum isotherms of 23.5 to 18.7℃, and they grow well on areas of relatively low summer temperature. The presences of numerous alpine plants on Chejudo are mainly due to their relative degree of sensitivity to high summer temperatures. The distributional limits of the some typical alpine species seem to coincide with the maximum summer isotherms.

Due to the high wind and extremely cold winter temperature on the subalpine and alpine belts of Hallasan, the wind-shaped formation tree and deformed dwarf krummholz trees of Korean fir, juniper and birch can be seen.

Overall, the present-day alpine and subalpine belts, as well as relevant arctic-alpine and alpine plants, are likely to have been formed during the post-glacial warming phase. The existence of a north-south orientation of mountain ranges, and of scattered numerous mountains within the Korean Peninsula, along with the presence of different climatic regimes, enabled many arctic-alpine and alpine plant species to survive in the alpine and subalpine belts in both primary and secondary refugia during both the glacial and interglacial phases, respectively.

The present occurrence of several arctic-alpine species on the Hallasan at the world's southernmost limit of their distribution, and of another species at the southernmost limit of their range in Northeast Asia, further promotes the idea of the existence of refugia for these species in the Korean Peninsula.

The presence of numerous arctic-alpine and alpine plants in the alpine and subalpine belts, mainly in the north, but also in the midlands, the south and Chejudo of Korea are mainly due to their relative degree of sensitivity to high summer temperatures. Arctic-alpine plants may be unable to grow in warm areas, partly because of competition from tall plants, but also because they themselves suffer from abnormal growth effects at high temperatures.

8. Conclusions

The presences of large numbers of the arctic-alpine flora on Hallasan, Cheju Island, at the mid of the Korea Strait between the Korean Peninsula and Japanese Islands, especially as the southernmost distributional limits of the earth for certain species may primarily be attributed to palaeo-environmental factors, since it can not be wholly explained by reference to present environmental conditions.

Floristic diversity and high endemicity of Hallasan may due to ; first, the long term isolation of island and summit from the Korean Peninsula since the Pleistocene, secondly, wide range of local environmental conditions (topography, climate, soil, vegetation, landscape etc.) provided and finally the absence of catastrophic environmental change in the past which ensured the survival of diverse floristic and vegetational elements.

The arctic-alpine flora on the peak of Hallasan, mainly above 1,500m a.s.l. are evidently descended from immigrants from Northeast Asia via the Korean Peninsula during the epoches of the Ice Age. These plants, which are very intolerant of competition, have been able to persist in alpine belts thanks to their harsh climatic conditions, sterile soil, rugged topography and cryoturbation. The distributional limits of the some species seem to coincide with the maximum summer isotherms. The continued survival of arctic-alpine and alpine plants on the summit of Hallasan, Cheju Island, Korea, however, is in danger, if global warming associated with the greenhouse effects continues to takes place.

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