Geographical Review of Japan Vol. 72 (Sec. B), No. 2, 122-134, 1999

Distribution of Arboreal Arctic-Alpine and Environments in NE Asia and Korea

Woo-seok KONG* and David WATTS** * Departmentof Geography, KyungHeeUniversity, Seoul, 130-701,Korea **Departmentof Geography, Hull University, Hull HU6 7RX,U. K.

Abstract: The distribution of arboreal arctic-alpine plants in NE Asia and Korea is discussed, The presence of large numbers of of the arctic-alpine flora in the Korean Peninsula, and especially the global southernmost distributional limits for certain species, may primarily be attributed to palaeo-environmental factors, since it cannot be wholly explained by reference to present environmental conditions. The disjunctive distribution of many arctic-alpine plants in NE Asia and the Korean Penin sula, as well as the Japanese Islands, suggests a former continuous distribution of these both regionally and on a broader scale. It also implies their range extension down-slopes and southwards during the Pleistocene glacial phases, and the subsequent breakdown of a former continuous range into fragments as the climate ameliorated during the post-glacial warming phase. The arctic-alpine flora, now mainly on the peaks of the Korean mountains, have been able to persist in alpine belts thanks to their harsh climatic conditions, sterile soil, rugged topography and cryoturbation. The horizontal and vertical distributional limits of some species seem to coincide with the maximum monthly summer isotherms, and the continued survival of alpine plants in Korea is in danger, if global warming associated with the greenhouse effect takes place.

Key words: arctic-alpine plants, NE Asia, Korea, the global southernmost distributional limit, Pleistocene glacial phases, post-glacial warming phase

seems little doubt that arctic-alpine species Introduction from farther north migrated south into Korea, and some at least stayed there, greatly adding The flora of East Asia is extremely rich and to the already rich temperate and sub-tropical distinctive, including more than 20endemic fl ora. During and since the Quaternary, con families and over 300endemic genera, and a spicuous local endemism has taken place, so huge number of endemic species (Takhtajan adding to the richness of this bio-diversity. In 1986). An intermediate region between temper excess of 4,500species of vascular species ate NE Asia and subarctic , which con are known to reside within the Korean Peninsu tains the Maritime Territory of Russia, NE la, a surprisingly rich assemblage, bearing in China, northern Korea, southern Sakhalin, and mind the fact that the area has been extensively Hokkaido of Japan, it is well characterised by a modified by man over the years. vegetation of mixed forests (Tatewaki 1963). It would be naive to expect a species to be However, no extensive research has been limited by a single climatic factor all round its carried out on the distribution of cold-tolerant range. Alpine and northern species, however, plants therein, including the arctic-alpine spe are known to be restricted in their distributions cies of NE Asia. to areas of low summer temperatures (Dahl The Korean Peninsula, a land of rich and 1951, 1998; Tralau 1961; Damman 1965, 1976; unique flora, largely escaped most of the Qua Korner 1999). From a historical viewpoint, the ternary glacial events, including extensive fossil record of arctic-montane plants has been snow cover. During the glacial maximum, there interpreted in the light of their present-day dis Distribution of Arboreal Arctic-Alpine Plants and Environments in NE Asia and Korea 123 tribution correlation with mean annual maxi Hulten (1958, 1962, 1971). They comprise first, mum temperatures of summer (Conolly 1970; more or less circumpolar plants with very dis Gauslaa 1985). Recently, the potential re rupted ranges (arctic and arctic-montane spe sponse of the vegetation to global climate cies); second, boreal plants with north-south change has also been investigated (Smith et al. races, or arctic-montane races overlapping the 1992; Hillier 1993; Krauchi 1992; Melillo et al. boreal area; thirdly, arctic-montane species 1996). If the widely predicted greenhouse effect occurring in the isolated southern mountains occurs, natural ecosystems will respond in but not occurring elsewhere south of the cen ways similar to responses in the past, but the tral Asiatic desert belt; and finally, plants effects on cold-tolerant arctic-alpine plants will known to have east-west races in their circum be more severe because of the rapid rates of polar range. temperature warming trends in Korea. More or less circumpolar plants with very This present work focuses on first, the com disrupted ranges (arctic and arctic-montane parative analysis of the current distributional species) include Diapensia lapponica and pattern of arboreal arctic-alpine plants in NE caerulea. The circumpolar Diapensia Asia focusing on the Korean Peninsula; and lapponica is divided into two major races, subsp. second, the reconstruction of migration and lapponica and subsp. obovata. Diapensia lap survival of arctic-alpine plants mainly in Korea, ponica subsp. obovata shows an amphi-Pacific as well as the vegetational shifts along climatic range (Figure 1). On the Pacific side this species changes in the past, based upon palaeo is known to be present continuously from botanical data. North Korean flora data are , the Chukchii Peninsula, Arctic areas, collated from the work of Chung and Lee the Russian Far East, Kamchatka, the Kuriles, (1965). Sakhalin, Hokkaido, Honshu and Korea. This species prefers dry slopes and rocky cliffs in Arctic-Alpine Arboreal Plants of NE Asia alpine regions (Ohwi 1984). On the summit of Mt. Halla of Cheju Island, Diapensia lapponica The floristic richness of NE Asia, which is due subsp. obovata grows solely in Korea and this to its great diversity in topographic, climatic site is designated as the global southernmost and edaphic conditions, as well as the absence limit of this species. of extensive glaciation during the Pleistocene, The circumpolar shows is a well-known fact (Li 1953). The major types both amphi-Atlantic and amphi-Pacific ranges of natural vegetation in temperate NE Asia (Figure 1). Phyllodoce caerulea grows well on include mixed northern hardwood forest, decid acid soil and reaches to about 1,850m a. s. l. in uous oak forest, birch forest and montane Scandinavia and to about 2,600m a. s. l. in the boreal coniferous forest (Wang 1957; Ohsawa Pyrenees, but is very rare in Scotland and in 1990, 1991, 1993a, b). Though the survival of the Pyrenees. On the Pacific side Phyllodoce arctic plants on the summits of the high moun caerulea occurs around the northwestern Pacific tains of Japan has been discussed (Takeda Ocean from Alaska, Siberia, the Chukchii Penin 1913; Okitsu 1993; Okitsu et al. 1984, 1989, sula, Russian Far East, Kamchatka, the Aleu 1995), very little biogeographical research has tian Islands, Sakhalin, Hokkaido, Honshu and dealt with a comparative analysis of northern Korea. The northern part of the Korean Penin or circumpolar floristic elements of NE Asia. sula is known as the global southernmost limit A knowledge of the floristic elements of a of this species. region is helpful in understanding the path Boreal plants with north-south races, or ways of migration into the region concerned arctic-montane races overlapping the boreal (Stace 1980). This present work is focused on area include Juniperus communis, Vaccinium the biogeography of the circumpolar flora in vitis-idaea, V. uliginosum, Ledum palustre and NE Asia. For the arboreal arctic-alpine plants Empetrum nigrum. Juniperus communis is the of NE Asia and the Korean Peninsula, four most widely distributed coniferous species and different distributional elements are noticed by has also been reported from Tertiary intergla 124 W. -s. Kong and D. Watts

(Modified from Hulteu, 1962, 1971) Figure 1. Global distribution of arctic-alpine plants (Diapensia lapponica subsp, obovata, Phyllodoce caerulea and Vaccinium vitis-idaea subsp. minus).

cial and late glacial layers. Though Juniperus species grows well in coniferous woods and on communis var. montana has been reported in the alpine slopes (Ohwi 1984). The scattered dis peaks of Korea (Hulten 1962), at present only junctive range occurred on the south of the Juniperus sibirica and J. chinensis var. sargentii circumpolar zone, and includes central China, grow. This species occurs also in Sakhalin, southern Japan and northern Korea. Hokkaido and Honshu of Japan. Vaccinium uliginosum is a circumpolar Vaccinium vitis-idaea consists of two closely Eurasiatic lowland plant, in Scandinavia, the related races, chiefly the lowland race subsp. European mountain and eastern Asia. The spe major and the arctic-montane race, subsp. cies is common in both Eurasia and North minus. Vaccinium vitis-idaea subsp. minus, America, including Kamchatka, the Aleutian which is a circumpolar and amphi-Pacific plant, Islands, Hokkaido, Honshu and Korea, The occurs in North America, Scandinavia, Alaska, southernmost limit of continuous range in NE arctic Siberia, Chukchii, the Russian Far East, Asia includes central Korea and Japan. Fossils Kamchatka, the Aleutian Islands, the Kuriles, of Vaccinium uliginosum have been found in Sakhalin, Hokkaido, Honshu, Shikoku, Kyushu, Pliocene layers in France, and in the Cambridge Mongolia, NE China, and Korea (Figure 1). This area, Mass., U. S. A. Distribution of Arboreal Arctic-Alpine Plants and Environments in NE Asia and Korea 125

Ledum palustre subsp. decumbens occurs in are designated as one of the global south arctic North America, Siberia, Eurasia and the ernmost limits of this species. In the Alps, Himalayas. This species reaches the mountains Oxycoccus palustris ascends to about 1,200m of Scandinavia and merges with subspecies and in N. Italy to about 1,900m. Isolated palustris in the north. Isolated disjunctive ranges of Oxycoccus palustris subsp. microcarpus ranges of this species can be noticed in Siberia, in NE Asia are noticed from Japan and northern Kamchatka, Sikhote-Alin, the Kuriles, the Korea. Russian Far East, northern Japan and north Linnaea borealis which is a circumpolar plant, ern Korea. This species occurs on heaths, in grows in North America and Eurasia, including dry, rocky places, in the mountains to at least the Russian Far East, Kamchatka, Chukchii, the 1,800m. Another subspecies Ledum palustre Kuriles, Sakhalin, Hokkaido, and northern subsp. diversipilosum grows in Amur, Ussuri, Honshu. In NE Asia, two disjunctive ranges, i.e., Okhotsk, Japan and Korea. NE China and Korea are noticeable. In the Alps Empetrum nigrum subsp. japonicum occupies this species reaches about 2,200m and de Kamchatka, the Russian Far East, Sakhalin, scends to about 1,270m. In Scandinavia it Hokkaido, Honshu and Korea. This species occurs from the lowlands to about 1,200m in forms broad and dense mats in alpine regions. southern Norway. In Colorado it grows be An Arctic-montane species occurring in the tween 2,600m to 3,300m. isolated southern mountains but not occurring , which is a circumpolar elsewhere south of the central Asiatic desert plant, grows in arctic North America and Eura zone is Dryas octopetala. In pre-glacial times sia, including the Russian Far East, Chukchii, Dryas octopetala already occupied a circumpolar Kamchatka, Sakhalin, Hokkaido, and northern area and was isolated in several different areas Honshu. In Great Britain, Andromeda polifolia during the glaciations. In the interglacials and ascends to 1,750m and in northern Italy to in post-glacial periods, some of these popula 2,000m. In Korea and Japan, Andromeda tions merged but other populations remained polifolia var. grandiflora has been reported and isolated, as those in Caucasus, Japan and the designated as the global southernmost limit of southern Rocky Mountains. In the north of species. Eurasia, two Dryas species, Dryas octopetala and Dryas punctata are reported. Dryas octopetala Arboreal Arctic-Alpine Plants of Korea var. asiatica occurs on dry alpine slopes of Kam chatka, the Kuriles, Sakhalin, Ussuri, Hokkaido, Out of the c. 380 Korean alpine plants, c. 130 Honshu and northern Korea (Ohwi 1984). The species occur in R. O. K. (South Korea) and in disjunctive distributions of Dryas octopetala clude 81species on Mt. Halla, 67 species on Mt. var. asiatica in the north of the Korean Peninsu Sorak and 54species on Mt. Chin. The location la, and Hokkaido and Honshu of Japan, are and height of mountains in Korea is presented noticeable. in Figure 2. Plants known to have east-west races in their More or less circumpolar plants with very circumpolar range, but which occur in the disrupted ranges (arctic and arctic-montane Korean Peninsula, include Oxycoccus quad species) of Korea, Diapensia lapponica subsp. ripetalus (palustris), O. microcarpus, Linnaea obovata, occur solely on Mt. Halla (1,800 borealis and Andromeda polifolia. - 1,950m a. s. l.) (Kong 1998a). The circumpolar Oxycoccus quadripetalus (palustris) has re Phyllodoce caerulea occurs from c. 42•‹N to sulted from the compounding of the genetics of 40•‹30•L N, and it is located on Mts. Chayoo, Oxycoccus macrocarpus and Oxycoccus micro Paikdoo (1,540-1,800), Kwanmo and Hoochi carpus. This species is found in the boreal area (Figure 3). of North America and Eurasia from Scandina Boreal plants with north-south races or via to the Russian Far East, the Kuriles, Sakha arctic-montane races overlapping the boreal lin, Hokkaido, northern Honshu and northern area of Korea, Juniperus chinensis van, sargentii Korea. Northern Honshu and northern Korea or Sabina sargentii is present from c. 40•‹30•L N to 126 W. -s. Kong and D. Watts

Figure 2. The location and height of mountains in the Korean Peninsula. N. B. Bars show the height of mountains Dots indicate the location of mountains

33•‹N, and is found on Mts. Seungjuk (1,600-), 2,000), Hoochi (1,000-1,300), Nangrim (1,700 Nangrim (1,700-), Peenanduk, Myohyang (1,600 -2,000), Keumpae (1,200-1,600), Sasoo (1,600 -1,900), Sasoo (1,600-1,740), Chuae (1,400-), -1,700) and Keumkang (1,000-1,600) (Figure 4). Keumkang (1,000-1,600), Sorak (700-800), Vaccinium uliginosum of Korea grows on Mts. Kaya, Dukyoo (1,400-), Chini (1,400-1,900) and Paikdoo (1,200-2,540), Mantap (2,000-2,200), Halla (1,500-1,950). Ro (1,700-2,000), Hoochi (800-1,200), Nangrim Vaccinium vitis-idaea subsp. minus is restrict (1,700-2,000), Keumpae (1,300-1,600), Sasoo ed, being present from 42•‹N to 39•‹30•LN, and (1,600-1,700), Keumkang (1,000-1,600), Sorak being located on Mts, Chayoo (1,400-), Paikdoo, (1,500-1,700) and Halla (1,500-1,950). Mantap (1,900-2,200), Chilbo (800-), Ro (1,700- Ledum palustre subsp. decumbens of Korea is Distribution of Arboreal Arctic-Alpine Plants and Environments in NE Asia and Korea 127

Figure 3. Distribution of Phyllodoce caerulea in the Korean Peninsula. N. B. Shaded lines show the altitudinal range of species on mountains Dots indicate the presence of species on mountains

found only on Mt. Paikdoo (1,800-2,540). 1,950) in Cheju Island (Kong 1998a). Ledum palustre subsp. diversipilosum shows a Arctic-montane species occurring also in the broad distributional range. In Korea, it grows isolated southern mountains but not elsewhere from 42•‹N to 40•‹N, and it is present on south of the central Asiatic desert zone include Mts. Paikdoo, Kwanmo, Mantap (1,100-1,600), Dryas octopetala var. asiatica. This species, in Chilbo (800-), Hoochi (800-1,100), Keumpae digenous to the entire or nearly entire circum (1,200-1,600) and Ro (1,700-2,000). polar area, is more restricted in its distribution, Empetrum nigrum subsp. japonicum of Korea occurring in Korea and Japan. It is confined has been recorded only from Mts. Paikdoo and to northern Korea in localities such as Mts. Hoochi in the north, and from Mt. Halla (1,500- Paikdoo, Ro and Nangrim (1,300-). 128 W. -s. Kong and D. Watts

Figure 4. Distribution of Vaccinium vitis-idaea subsp. minus in the Korean Peninsula. N. B. Shaded lines show the altitudinal range of species on mountains Dots indicate the presence of species on mountains

Plants known to have east-west races in their Mantap and Ro. circumpolar range, but which occur in the Korean Peninsula include Oxycoccus micro Distributional Pattern of Arboreal carpus, Oxycoccus quadripetalus (palustris), Arctic-Alpine Plants in NE Asia Linnaea borealis and Andromeda polifolia. Out and the Korean Peninsula of those, Oxycoccus microcarpus, Oxycoccus quad ripetalus (palustris) and Andromeda polifolia Four distributional patterns are noticed for var. grandif lora occur from 42•‹N to 41•‹N, in arboreal arctic-alpine plants in NE Asia and the cluding Moosan and Kilju. Linnaea borealis of Korean Peninsula. These include first species Korea is present on Mts. Paikdoo, Kwanmo, with a continuous distribution in NE Asia, Distribution of Arboreal Arctic-Alpine Plants and Environments in NE Asia and Korea 129 which are widespread in Korea; secondly spe tribution worldwide suggests that the Korean cies with a continuous distribution in NE Asia, Peninsula has served as a major glacial refugia but which are restricted in Korea. It also con during the Pleistocene glaciation (Kong 1999a). tains species with a disjunctive distribution in Many hypotheses are available to explain the NE Asia, but which are widespread in Korea; worldwide disjunctive distribution of cold and finally species with a disjunctive distribu tolerant arctic-alpine plants. First, they occur tion in NE Asia, which are restricted in Korea. in response to general environmental varia Out of the five arctic-alpine plants, which tions over time, and especially climatic changes show a continuous distribution in NE Asia and during the Pleistocene glaciation. Secondly, the are widespread in Korea, only Empetrum nigrum expansion of forest tree communities on low subsp. japonicum belongs to this group, and it land subsequent to the end of the Pleistocene occurs in northern Korea and Cheju Island. has had the effect of restricting formerly con Twelve arctic-alpine species grow continu tinuous arctic-alpine groups into disjunctive ously in NE Asia, but display a restricted distri areas on mountain lands. Thirdly, there has bution in Korea. Four arboreal species, which been an ever-greater restriction of available belong to this group are confined to the north habitats for arctic-alpine plants following this of Korea and include Oxycoccus quadripetalus, climatic amelioration. Finally, the creation of Vaccinium vitis-idaea subsp. alpinum, Vac new biogeographical barriers by the expansion cinium uliginosum and Phyllodoce caerulea of new forest has in itself, caused non (Figure 1). mountain, as well as mountain disjunction Thirty arctic-alpine species are found dis (Hulten 1955; Love 1967; Tivy 1982; Bremer junctively in East Asia, but show a widespread 1983; Goudie 1992). distributional pattern in Korea. This group It is likely that the disjunctive distribution of contains three arboreal arctic-alpine plants, arctic-alpine plants in Korea may be due pri including Juniperus communis var. montana, marily to the southward expansion of species which appears to be the same species as towards the Korean Peninsula from the arctic Juniperus chinensis var. sargentii (Sabina regions into refugia, as the Pleistocene glacia sargentii). This species is found throughout the tion phases approached. And then their subse Korean Peninsula. quent isolation upslope in mountain areas as Twenty-eight arctic-alpine species occur dis the Post-Last Glacial Maximum climatic junctively in NE Asia, and are restricted in amelioration followed. It could be due to their Korea. This group includes ten arboreal species continued preservation in isolation in some which are confined to the North, such as Dryas mountain refugia during the LGM itself, and a octopetala var. asiatica, Oxycoccus palustris subsequent persistence in the same areas. subsp. microcarpus, Vaccinium vitis-idaea subsp. Present distribution pattern of arctic-alpine minus, Linnaea borealis, Ledum palustre subsp. plants enable the suggestion that the main diversipilosum, Ledum palustre subsp. decum southward migration route of arctic-alpine bens, Chamaedaphne calyculata and so on. plants from the Arctic to Korea was through Diapensia lapponica subsp. obovata is only found the Maritime Territory of the Far Eastern on the summit of Mt. Halla, Cheju Island in the Russia, and especially along the Sikhote-Alin Korean Peninsula. mountain ranges, which connect arctic Siberia Overall, six arboreal arctic-alpine plants grow and the alpine regions of northern Korea. in the Korean Peninsula at the world's south ernmost limits of their distribution. They in Vegetational History clude Phyllodoce caerulea, Ledum palustre subsp. diversipilosum, L. palustre subsp. decumbens, According to Bocher (1951), history, in partic Rhododendron parvifolium, Diapensia lapponica ular the survival of circumpolar plants during subsp. obovata and Empetrum nigrum subsp. the ice-age, undoubtedly plays an important japonicum (Figure 1). The survival of these role, rather indirectly, by geno-typical changes species at the southernmost limits of their dis in refugia or during the migrations. This pres 130 W. -s. Kong and D. Watts

ent work aims to reconstruct the vegetational Pleistocene of Korea. The appearance of decid history of cold-tolerant arctic-alpine plants of uous broad-leaved plants and cryophilous ever Korea, as well as the vegetational shifts along green coniferous trees such as Taxus, Abies, climatic changes in the past, based upon palaeo Picea, Tsuga, Pinus (Haploxylon) and Thuja botanical data. within the peninsula further indicates the Though the appearance of the oldest existence of cold episodes during the Upper in Korea dates back to the Permian period of Pleistocene. the Palaeozoic, the first which occurred Most of these conifers such as Juniperus, during the Cretaceous period of the Mesozoic Picea, Abies, Larix, Taxus and Cephalotaxus may was Pinus, and this has thrived as one of the have been present from the Miocene; Thuja dominant tree species since then (Kong 1995, dates back to the Middle Pleistocene; and the 1997). The oldest dicotyledon in Korea dates cold-tolerant Pinus pumila, P. sibirica and P. back also to the Cretaceous, but many of the koraiensis to the Upper Pleistocene. In the case present-day floristic genera indeed date only to of Korean dicotyledon genera, which now occur the Oligocene (Kong 1996, 1997). on the high mountains, these have been The presence of thermophilous genera, such reported from the Cretaceous. Salix and Acer as Myrica, Ficus and Hedera in the Oligocene at date back to the Oligocene; Carpinus, Quercus, up to four degrees north of their present dis Betula, Rhododendron and Sorbus date back to tributional limits implies that the climate of the the Miocene (Kong 1996, 1997). Oligocene was warmer than that of today. Glaciation within the Korean Peninsula was Therefore, most of cryophilous alpine and sub always restricted in the northernmost moun alpine plants during the Oligocene might have tains down to 1,900m a. s. l. during the penulti been confined their distribution to the alpine mate glaciation. During this period, the and subalpine belts of northern Korea. The climatic snowline in Korea was at c. 2,000m in occurrence of a similar thermophilous floristic northernmost Korea, and 2,750m in southern element at up to six degrees north of its present Korea (Kong 1989). The presence of cold epi range during the Middle Miocene suggests a sodes during the Upper Pleistocene in the maximum northward expansion of warmth Korean Peninsula might have caused a general tolerant evergreen broad-leaved vegetation expansion of deciduous broad-leaved plants at that time. For example, Cinnamomum, and cold-tolerant evergreen coniferous plants Cyclobalanopsis and Ilex fall into this category as well as the southward expansion of (Kong 1995, 1996, 1997). The occurrence of cryophilous arctic-alpine and alpine floras in thermophilous plants during the Middle Korea. The disappearance of some cold-tolerant Miocene suggests a maximum northward genera, such as Pinus (Haploxylon), Picea, A bies, retreat also of the alpine and subalpine belts for Larix and so on from 10,000years B.P. marks recent Korean vegetational and environmental the continued climatic amelioration since then, history. along with minor climatic fluctuation during According to Larsen (1980), arctic and boreal the Holocene period. fl oras developed throughout the Tertiary Overall, the presence of cold episodes during period, beginning about 70million years ago, the Upper Pleistocene might have caused a gen and probably earlier than this. With the eral southward expansion of alpine and subal steadily-declining temperatures of the late Ter plants and vegetation in Korea. The tiary, it is probable that modern species now climatic warming trend from 10,000years B.P., characteristic of both the arctic and boreal flora however, has isolated alpine and subalpine evolved from former species of the Tertiary plants and relevant vegetation, mainly in fl ora of the . northern Korea but also on high mountains in The present admixture of evergreen conifer southern Korea. ous trees, e.g., Taxus, Abies and Thuja and decid uous broad-leaved plants also indicates a prob able temperate climate for much of the Middle Distribution of Arboreal Arctic-Alpine Plants and Environments in NE Asia and Korea 131

Minor, Central Asia, Afganistan, Siberia, China, Migration and Survival of Arctic-Alpine Mongolia and Japan but Korea was not Plants designated as one of refugia (Kong 1989). During the Pleistocene cold phase, it is likely Using all the evidence, from the basis of the that the climate in northern high alpine belts of present-day latitudinal distribution of arctic NE Asia was too cold and harsh for many alpine plants in Korea, their altitudinal ranges, arctic-alpine and alpine plants to survive. Pleis the fossil evidence and the distributional tocene glaciations in NE Asia are known from patterns of circumpolar plants, the patterns the highlands east of Lake Baikal, the East of migration of arctic-alpine plants from NE Sayan Mountains, Northeast Siberia, including Asia into the Korean peninsula have been Sakhalin, Verkhoyansk, Kamchatka, the high reconstructed. est summits of Japan and Taiwan, and The wide-ranging disjunctive distribution of the northern high mountains of Korea plants in the Arctic and Boreal Eurasia may (Charlesworth 1957). Therefore, arctic-alpine have originally been attained in Tertiary times and alpine plants had to confine themselves to by normal dispersal over land, and may have lower mountain and/or lowland areas, which survived the maximum Pleistocene glaciation effectively then became their primary refugia. in refugia, or at the south of the ice sheet. With Then, as the climate subsequently ameliorated, the retreat of the ice sheets, they seem to have arctic-alpine and alpine plants moved back up spread rapidly into the present far northern slope to the mountain top, which proved to be ranges (Thorne 1978). important secondary refugia within the Korean It has been suggested that, in the pre Peninsula. - Pleistocene southward migration, there were However, as the climates ameliorated during three principal avenues of escape, such as along the post-glacial period, temperate species both the lowlands of eastern Asia, along the moun in lowlands and mountain lands then became tain ranges of North America and down the more common than arctic-alpines. As a result Scandinavian Peninsula and adjacent areas into of the increased competition associated with western and central Europe (Polunin 1960). this process, arctic-alpine and alpine plants As the climate deteriorated during the Pleis retreated upward towards mountain tops, and tocene cold phases, most of temperate trees in the fragmentation of the arctic-alpine and NE Asia and Korea would have shifted down alpine plants' distributional range took place in ward from the mountains and southward from the Korean Peninsula. The arctic-alpines were the north. At the same time, cryophilous arctic once widespread over the lowlands of the Late alpine and alpine plants moved downward and Glacial, but have been removed from all habi southward as well. During the Quaternary, be tats with distinctive ecological and micro cause of the glaciation, many alpine species climatic conditions. This removal has been have migrated from the north via Siberia and caused by the spread of forest trees into envi Kamchatka into Japan (Murata 1977). ronments, which were formerly unsuitable. Concerning the Pleistocene refugia, many The warming of post-glacial times and the areas, such as nunataks, refugia near the ice associated spread of forest has led to the frag margins, the continental shelf, mainland mentation of the distribution of cold-tolerant refugia which are far from the ice margins and plants (Goudie 1992). dispersed mainland refugia, are suggested (Hol At present, therefore, arctic-alpine and alpine land 1981). The Himalayan region also is plants are mainly confined to the alpine and believed to have served as the refugia for both subalpine belts of mountains in Korea, along plants and animals throughout the Pleistocene with specific-habitat-adapted species, which (Hoffman and Taber 1967). On a worldwide grow below the alpine belt. Evergreen arboreal scale, many Asian regions have been suggested arctic-alpine plants dominate low-nutrient envi as refugia for arctic-alpine plants during the ronments. This may result from a lower annual Pleistocene glaciations, and include Iran, Asia requirement or loss rather than from a direct 132 W. -s. Kong and D. Watts

relationship with rate of photosynthesis per ranges in the Korean Peninsula which has en unit of nutrient invested in the (Chapin abled smooth migrations of arctic-alpine and et al. 1980). alpine plants from NE Asia to the south to take Overall, the present-day alpine and subalpine place, with the onset of the Pleistocene cold belts, as well as relevant arctic-alpine and phases. Third, the existence of a large number alpine plants, are likely to have been formed of alpine, subalpine and montane areas, mainly during the post-glacial warming phase. The in the north, but also in central and southern existence of a north-south orientation of moun Korea, which ensured that isolated spaces were tain ranges, and of scattered numerous moun available for these species to colonise during tains within the Korean Peninsula, along with the Holocene period. Fourth, many parts of the presence of different climatic regimes, en Korea have served as primary refugia for these abled many arctic-alpine and alpine plant spe plants during the Pleistocene glacial phases and cies to survive in the alpine and subalpine belts secondary ref ugia during the post-glacial in both primary and secondary refugia during period as the climate ameliorated. And finally, both the glacial and interglacial phases, respec the different climatic regimes present in the tively. Speed of dispersal has been of Korean Peninsula today has encouraged the considerable significance in establishing the long-term survival of these species at alpine present-day geographical distribution of spe and subalpine belts in recent times. The ap cies. It seems that 100-200km or more per pearance of the Korean alpine and endemic 1,000years is a minimum rate of dispersal for alpine species no doubt reflects the long-term many plants under favourable conditions isolation of species in the Korean Peninsula, (Larsen 1980). and the local environmental peculiarities, The present occurrence of several arctic which have both accentuated this isolation and - alpine species, in the alpine and subalpine belts aided the development of genetic diversity. of Korea, at the world's southernmost limit of The presence of several arctic-alpine species, their distribution (Figure 1), and of another spe in the alpine and subalpine belts of Korea, at the cies at the southernmost limit of their range in world's southernmost distributional limit, and NE Asia, further promotes the idea of the exist of other species at the southernmost limit of ence of refugia for these species in the Korean their range in NE Asia further promotes the Peninsula. idea of the existence of refugia for these species The presence of numerous arctic-alpine and in the Korean Peninsula. The disjunction of alpine plants in the alpine and subalpine belts, many arctic-alpine plants in NE Asia, the mainly in the north, but also in the midlands, Korean Peninsula and the Japanese Islands, the south and Cheju Island of Korea are mainly suggests a former continuous distribution of due to their relative degree of sensitivity these both regional and on a broader scale. And to high summer temperatures (Kong 1998b, their range extension down-slope and south 1999b, c). Arctic-alpine plants may be unable to wards during the Pleistocene glacial phases grow in warm areas, partly because of competi might have caused the subsequent breakdown tion from tall plants, but also because they of a former continuous range into fragments as themselves suffer from abnormal growth the climate ameliorated during the post-glacial effects at high temperatures (Walton 1984). warming phase. The continued survival of arctic-alpine and alpine plants in Korea, howev Conclusions er, is in danger, if global warming associated with the greenhouse effect continues to take The occurrence of a large number of arctic place. - alpine and alpine plants, which form up to 10% of the total Korean flora, may be due to first, the Acknowledgements absence of catastrophic environmental events such as a continental ice sheet in Korea. We thank The Association of Japanese Geogra Second, the north-south linkage of mountain phers for the contribution of this paper. Preparation Distribution of Arboreal Arctic-Alpine Plants and Environments in NE Asia and Korea 133 of this article benefited greatly from communications endon Press. with Professor H. H. Won of Kyunghee University, Hillier, S. 1993. Climate change impacts on British Korea and Professor H. Kohsaka, Nihon University, vegetation; creating tomorrow's climate today. Japan. 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