ECOLOGICAL AND GEOGRAPHICAL OUTLINE OF THE ENTOMOFAUNA OF THE KURIL ARCHIPELAGO
SECTION 1. PHYSICAL GEOGRAPHICAL CONDITIONS
The Kuril Archipelago comprises a chain of mountainous islands of volcanic origin, which extend nearly 1,200 km from the northeast to the southwest, from the Kamchatka Peninsula to Hokkaido, between 4326 and 5055 N and 14524 and 15630 E. The waters of the Sea of Okhotsk wash it on the west and those of the Pacific Ocean on the east. The islands form two parallel island chains which bear the names Greater Kuril Range and Lesser Kuril Range (Figure 15). Their total area is about 15,600 km2.
The Greater Kuril Range includes a number of comparatively large (Kunashir, Iturup, Urup, Simushir, Onekotan, Paramushir, and Shumshu) and smaller islands, about 25 in all, as well as numerous crags and rocks elevated above the water. The islands are the peaks of an enormous mountain ridge, the base of which is submerged in the sea. The straits between the islands are of varied width (from several to tens of kilometers) and depth (50-2,000 m). The relief of the islands is highly diverse, represented by mountainous massifs, consisting of solitary volcanos or groups of them, hills, and plains. Many of the volcanos are active and play a leading role in the relief-forming process. The majority of the volcanic massifs are classified as medium-high, with peaks from 1,000 to 2,000 m, and low-mountain, not exceeding 1,000 m above sea level. Only the Alaid Volcano (2,339 m) in the north of the range is considered a high-mountain volcano. Lowland and hilly relief are characteristic of the large islands and cover limited areas. The necks (of fill or alluvial origin), abrasion and accumulation marine terraces, lava plateaus, alluvial riverine and coastal plains, lowland sections in the calderas of ancient volcanos, the so-called atrios of complex volcanos (Korsunskaya, 1958), are among the elements of lowland relief. Only Shumshu, the northernmost of the islands of the Greater Kuril Range, is entirely lowland. The shores of the islands are extremely varied in character, from steep craggy clifs which are encountered mainly on the Okhotsk littoral, to gently sloping shorelines, leveled in some places, on the Pacific Ocean side.
The large islands comprise complex formations which have arisen as a result of the joining of neighboring volcanic islands by means of bridges (necks) of an alluvial and accumulative character. This is indicated by the existence of lakes of lagoon origin of nearly all the necks. Thus, Kunashir was formed of four independent mountainous massifs: the calderas of Golovnin Volcano, Mendeleev Volcano and Otdel'naya Mountain, the Dokuchayev Ridge, the Tyatya Volcano, and the hilly Lovtsov Peninsula, composed of sedimentary rocks. These parts of Kunashir are joined together by bottomland necks, on which lagoon lakes of various sizes are situated. Iturup consists of 12 volcanos and mountain massifs, separated in the past and joined today by necks and mountainous cols. There are five groups of volcanos, separated by low cols, and occupied by lakes, of which the largest is Lake Tokotan on Urup. Simushir is also formed of six volcanic massifs, fused or joined by necks deposited by the sea.
Some smaller islands may be termed volcano islands, since they have been formed by solitary volcanos elevated above the surface of the sea, with a narrow coastal strip or with precipitous shores. Among these are the islands of Ketoy, Matua, Raykoke, Chirinkotan, Antsiferova (Shirinki), Atlasova (Alaid), and some others.
The river system is well-developed on the large islands, where there are numerous small rivers and streams. On the small islands, especially on the volcanic islands, the slopes of which are covered by pyroclastic materials and fissures which are highly water-permeable, there are few rivers, and on some islands there are none at all in the summer. The rivers are fed by atmospheric precipitation, large collections of snow, which melts slowly in the mountains in the spring and summer, and mineral springs. G. V. Korsunskaya (1958) divides the Kuril rivers into mountain, lowland, and mixed types based on their character and the water regime. The mountain rivers are distinguished by a narrow bed, rushing flow, waterfalls which not infrequently plunge downward from steep shores directly into the sea, by the small number of tributaries, and by their short length. The lowland rivers are characterized by slow flow and by wide multiterrace valleys. They are encountered mainly on the necks. The mixed-type rivers begin in the mountains, where they possess the features of mountainous water courses; after descending to the lowlands, they take on the features characteristic of lowland rivers. The flood plains of the rivers and streams on the Kuril Islands, as is the case on Sakhalin, are typically thickly overgrown with tall herbaceous vegetation forming gigantic brakes (Figure 16).
Lakes are fairly common on the archipelago. The majority of these have been formed of marine lagoons on the necks. This process is continuing even at the present time. Lake Lagunnoye on Kunashir, which is separated from the Sea of Okhotsk by a narrow sandbar, evidently deposited relatively recently, may serve as an example. Typically the lagoon lakes are connected to the sea or ocean by a narrow channel (Lake Peschanoye on Kunashir, Lake Tokotan on Urup, etc.). The shores of such lakes are thickly overgrown with herbaceous vegetation.
Among the lakes of volcanic origin, one differentiates the caldera lakes (Lake Goryacheye on Kunashir, Lake Krasivoye on Iturup, Lake Biryuzovoye on Simushir), the crater lakes, which are usually solfatara lakes (Lake Kipyashcheye on Kunashir, the hot lake in the crater of Ebeko Volcano on Paramushir, which disappeared after the eruption of the volcano in the fall of 1964), and the lava-retaining lakes (Slavnoye and Lopasnoye Lakes on Iturup). The solfatara lakes typically remain devoid of life. The caldera and lagoon lakes, on the other hand, are inhabited by various aquatic insects and sometimes have a very original entomofauna, for example Lake Goryacheye.
The Lesser Kuril Range, 100 km in length, is situated to the southeast of the Greater Kuril Range and is separated from it by the Yuzhnokuril'skiy Strait, which is 60 km in width. It is a continuation of the Nemuro Peninsula (Hokkaido), and simultaneously the southern (most elevated) part of the underwater Vityaz' Ridge, which extends northeastward to Kamchatka (Figure 17; according to Goryachev, 1966). The Range consists of six small, lowland, treeless islands and the larger northern Shikotan Island, which exhibits low-mountain-hilly relief and is covered by broadleaved-dark coniferous forests.
The climate of the Kuril Archipelago is determined by its geographical position at the boundary of the Asian continent and the enormous aquatic expanses of the Pacific Ocean, by the prevalence of the East Asian monsoons, by the great north to south extent, by the character of the cold and warm marine currents washing the shores, and by the general temperature regime of the surrounding aquatic masses, as well as by the relief of the islands themselves. In winter steady northwesterly winds blow in this region, caused by the shifting of dry air masses that are cooled markedly above the continent. Reaching more southerly latitudes and moving out over the Sea of Okhotsk, which is not entirely covered by ice, these air masses are warmed and moistened somewhat, bringing precipitation to the islands in the form of abundant snowfalls. In the winter the precipitation is primarily brought to the northern islands by cyclones from the Bering Sea, where the so-called "Aleutian minimum", i.e., a low-pressure region, is established (Ushakov, 1946; Korsunskaya, 1958). Flows of warm subtropical air that induce thaws up to +9, which are especially frequent on the southern islands, often break through from the south in winter in the region of the Kuril Range. The winter northwesterly monsoon is replaced in summer by a southeasterly monsoon which blows from the region of the Pacific Ocean subtropical maximum. It brings to the archipelago masses of warm and moist air, inducing summer rains and fogs that fall mainly on the eastern littoral, since the western littoral is protected by mountains.
Winds on the Kuril Islands reach hurricane force, up to 40-50 m/sec. In summer they shift masses of sand, sweeping up sand dunes on the shores, covering adjacent forests and settlements, and in winter they sweep up enormous drifts in some places and denude the ground in others. The woody vegetation on the shores acquire the character of elfin woods, with trunks pressed to the ground through the constant action of the wind (Figure 18).
The abundant precipitation throughout nearly the entire year (700-1,000 mm per year on the northern islands and 1,000-1,030 mm on the southern islands), the encirclement by colossal aquatic expanses, and the predominance of overcast weather create constant high humidity on the islands with moderate temperatures; this is characteristic for a typically maritime climate. Thus, the mean annual relative humidity of the air in Kurilsk is 80.2%, and the mean annual temperature of the air is correspondingly equal to +4.5.
Despite the maritime climate, which is characteristic of the archipelago as a whole, the environment is varied in its various parts. The climate is more severe on the northern and central islands (from Shumshu to Urup), and is characterized by a prolonged, although somewhat warmer winter than in the south, which lasts about 5 months, a late protracted and cold spring, a short (1.5-2.0 months) cool summer, and an early autumn commencing in September. Uneven and gradual melting of snow, with the preservation from year to year of intergelisols which form thick strata in places (Figure 19), is characteristic for the northern islands. The development of plants which begin to vegetate as they are freed from the snow cover is closely associated with this phenomenon. In July-August 1964, on Paramushir, we observed concurrently all of the phenological phases of the development of woody and herbaceous vegetation, from the unfurling of leaves to fruiting, depending upon their distance from firns.
The climate is somewhat milder on the southern islands (Iturup, Kunashir, and partially Shikotan). Here winter is less prolonged (about 4 months) and more frosty; the average number of blizzard days is almost half that in the north. Spring starts a month earlier. The summer is longer than on the northern islands, by about 1.0-1.5 months, and is warmer, with mean monthly temperatures of +12 and +19, and maximal temperatures up to +31. Fall continues to the end of November.
Despite the commonality of the climate, there are many local areas, often situated close to one another (at a distance of only several kilometers), with local microclimatic conditions which are of great significance for the formation of phyto- and zoocenoses. These microregions have been observed by some investigators (Yaroshenko, 1960a, 1960b; Vorob'ev, 1963; Krivolutskaya, 1964), but thus far remain nearly unstudied. The occurrence and existence of such areas with warmer or cooler microclimate are determined by the warm and cold marine currents which wash, respectively, the western and eastern shores of the archipelago, by the disposition of the mountain ridges that often screen off the west coast from the east, resulting in the creation of different wind and temperature regimes on them, and the presence of volcanic activity which warms isolated areas. This is manifested especially dramatically when the thermal influence of volcanic activity is combined with the protective role of the mountains, which restrain cold fogs and winds from the Pacific Ocean in the summer. A southern thermophilous flora flourishes luxuriantly at such sites, and representatives of a southern fauna are concentrated there, as in the region of the Golovnin caldera on Kunashir.
Substantial differences in weather conditions and temperature regime are observed between the Okhotsk and Pacific Ocean littorals, especially on the large islands. Whereas rain falls or a drizzling fog hangs on the eastern littoral, bright sun shines on the western littoral (over only several kilometers). This variation in weather, when one moves from the Sernovodsk set. to Alekhino set. (Kunashir), which are separated by a relatively low pass, is especially striking. Interesting data regarding the difference in climatic conditions on the Pacific Ocean and Okhotsk coasts of Iturup, based on two-year-long observations of A. I. Butenko (Table 15), can be cited. A. I. Butenko also observes that the western slopes of the mountains are freed of snow in May, whereas on the eastern slopes the snow melts slowly and in some places may be preserved throughout the summer.
According to the observations of D. P. Vorob'ev (1963), the same phases of development in the very same species of plants, namely kolomikta vine (Actidinia kolomicta), mountain ash (Sorbus commixta), maple (Acer ukurunduense), honeysuckle (Lonicera edulis), black crowberry (Empetrum nigrum), Japanese bird cherry (Padus ssiori), and others commence on the Okhotsk coast and in the depth of the islands 8-12 days earlier than on the Pacific Ocean coast. The same can be said regarding the phases of development of the insects.
Vegetation with which the insects world is closely associated depends directly on the climatic conditions. The vegetation of the Kuril Archipelago has been studied in considerable detail both by Soviet (Vasil'yev, 1944, 1946; Vorob'ev, 1947, 1956, 1963; Lashkov, 1948; Koval', 1960; Yaroshenko, 1960b; Popov, 1962, 1963), and foreign botanists (Miyabe, 1890; Takeda, 1914; Kudo, 1921, 1922, 1927; Tatewaki, 1928, 1929, 1933, 1940, 1957; Ohwi, 1933; Hulten, 1933). Several systems of geobotanical regionalization of the territory of the Kuril Range have been proposed. We will dwell on two of the more recent ones advanced by M. Tatewaki (Tatewaki, 1933, 1957) and D. P. Vorob'ev (1963), since we have had occasion to return to them when analyzing the zoogeographical features of the entomofauna.
M. Tatewaki assigns the Northern and Central Kuril Islands to the Subarctic Province, and the Southern Islands to the East Asian Province. He draws the boundary between them, the so-called Miyabe line, through the Vries Strait, between the islands of Urup and Iturup. He than distinguishes three regions within the limits of the Range, northern, central, and southern, each of which in it turn he divides into two subregions (Figure 20). M. Tatewaki's regionalization has been adhered to by many scientists in Japan until the present time.
D. P. Vorob'ev assigns all of the northern and central islands up to Urup, with some reservations, to the North Pacific Ocean meadow subregion, and the southern islands (including Urup), to the Far East coniferous-broadleaved subregion and the Japanese-Korean Province. He further divides the entire range into three districts: Southern Kamchatka, Central Kuril, and Kuril-Sakhalin. He distinguishes two regions within the limits of the districts: the Northern Kuril, to which he assigns all of the northern islands up to Rasshua, and the Southern Kuril, dividing the latter into four subregions (Figure 21). Thus, D. P. Vorob'ev, based on new data, presents a revised, more differentiated geobotanical regionalization of the southern part of the archipelago.
Considering the fact that insects are closely associated with specific plant formations, we will briefly characterize the vegetation of the principal regions of the Kuril Range. As one moves from north to south, the appearance of the vegetation changes appreciably. On the northern and partially the central islands (from the Kamchatka Peninsula to Rasshua), the woody vegetation is represented by subalpine, stunted elfin groves of "Kamchatka" alder (Alnus kamtschatica) and Japanese stone pine (Pinus pumila), admixed with which are mountain ash (Sorbus sambucifolia) and willows (Salix, several species). The birch is absent on these islands. Quite large expanses are occupied by forb meadows, waterlogged in some places, alternating with groves of woody species. On Paramushir, the upper parts of the slopes of some volcanos (Ebeko, Chikurachki, etc.) are covered by mountain tundras or are entirely devoid of vegetation.
Farther south, starting with Ketoy, such representatives of a southern flora as the Kuril bamboo (Sasa kurilensis), and of the woody species, Erman's birch (Betula ermanii), scrub forms of the yew (Taxus cuspidata), and the "Kuril" cherry (Cerasus kurilensis), shrubs (holly, Ilex rugosa, and Middendorff's weigela, Diervilla middendorffiana), and a number of southern herbaceous plants appear. But, in essence there are no forests as such on the islands of Ketoy and Simushir yet. Here the woody vegetation, as in the case of the more northerly islands, has an exclusively elfin character.
Forests appear only on Urup, where the Kuril bamboo, which forms impassable groves throughout the entire island, acquires simultaneously wide distribution and robust development. Of the woody species, Erman's birch, which forms sparse elfin stands, Korean mountain ash (Sorbus commixta), "Maksimovich" alder (Alnus maximoviczii), the "Kuril cherry", and Japanese stone pine which occupies primarily mountain slopes but which not infrequently descends to the very seashore, are common on Urup; maples (Acer pictum and A. ukurunduense) are encountered in the depths of the island, in places protected from the wind. Under the protection of the Kuril bamboo, which reaches a height of 2-4 m and greater, such representatives of southern broadleaved forests as the yew, which has a bushy form, the oriental poison oak (Toxicodendron orientalis), the spindle tree (Euonymus striata), and the evergreen shrubs (Ilex rugosa and Skimmia repens), and a number of southern herbaceous plants grow even on the coastal slopes; among these are some fellow-travelers of the dark coniferous forests, for example, the fern (Plagiogyrria matsumuraeana), etc. A belt of Erman's birch stands with a cover of Kuril bamboo and a belt of Japanese stone pine are quite distinctly conspicuous on Urup; although the latter can grow at various heights, beginning at the seashore, it is displaced here by other plants.
On the Southern Kuril Islands, especially in the southern region of Iturup and on Kunashir, the dark coniferous forests, consisting of Sakhalin fir (Abies sachalinensis), spruces, the Yezo spruce (Picea microsperma) and Sakhalin spruce (P. glehni), and singly the yew (Figure 22), become the predominant plant formation. A number of broadleaved species whose trees reach great heights are included in these forests as an admixture; these are the shallow-cup Mongolian oak (Quercus crispula), the sen (Kalopanax septemlobum), the painted maple (Acer pictum), the trichocarpous toxicodendron (Toxicodendron trichocarpum), and others, as well as lianas, of which the most numerous are the climbing hydrangea (Hydrangea petiolaris), and the oriental poison oak (Figure 23).
Here and there in the central region and along the western coast of Iturup, broadleaved species become prevalent. On Iturup the thick-trunk trees of the Japanese poplar (Populus maximoviczii), in some places the "Sakhalin" apple (Malus sachalinensis), which reaches a height of 12 m (Vorob'ev, 1963), the Japanese bird cherry (Padus ssiori), and willows (Figure 24) grow in the river valleys. A special plant grouping, represented by sparse larch stands, which grow among the Kuril bamboo, intermixed with Erman's birch and Japanese stone pine, exists in the central region of Iturup (Figure 25). The Kuril Dahurian larch (Larix kurilensis) forms pure stands only on limited areas (Listvennichnoye Plateau).
Broadleaved and dark coniferous-broadleaved forests grow in the southern half of Kunashir; in their appearance they are very reminiscent of the forests of Hokkaido. They achieve a special luxuriance on the southwest coast of the island and in the region of the Golovnin caldera (Figure 26). These forests comprise a complex combination of diverse woody species which are characteristic of various vegetation zones and which belong to various geographical groupings. It is possible under the conditions of the moist, relatively warm climate for the following to flourish together: spruce, fir, yew, Japanese stone pine, magnolia (Magnolia obovata), oak (Quercus crispula), sen, cork tree (Phellodendron sachalinensis), elms (Ulmus laciniata and U. propinqua), and cherry (Cerasus sachalinensis and C. maximoviczii), which here achieves the sizes of large trees with a trunk diameter of 50 cm, Bothrocaryum (Bothrocaryum controversum), mulberry (Morus bombycis), linden (Tilia maximovicziana), alder (Alnus maximoviczii), panicled hydrangea (Hydrangea paniculata), several species of birch (Betula ermani, B. ulmifolia, B. maximovicziana, B. tauschii), lilac (Syringa amurensis), grape and other vines (climbing hydrangea, oriental poison oak, Actinidia, Ampelopsis) which closely entwine the tall trunks of coniferous and leaved trees. The luxuriant development of tall herbaceous vegetation (the ferns, "Sakhalin" knotweed, meadowsweet, tassel flower, Lisichitum, coltsfoot, Cardiocrinum glehnii, and many others) under the forest canopy, especially in the moist floodplains of streams, is striking (Figures 27, 28).
On the Lesser Kuril Range, the vegetation of Shikotan and the small islands is varied; it also is distinguished from that on other islands of the Greater Kuril Range. The small islands are treeless; the scrub forms of mountain ash (Sorbus sambucifolia) and such shrubs as the ledum (Ledum macrophyllum), bog whortleberry (Vaccinium uliginosum), and black crowberry (Empetrum nigrum) grow on them only in some places. But in the main, these small islands are covered with forb meadows and Kuril bamboo.
Dark coniferous forests of Yezo spruce and Sakhalin fir with an admixture of several leaved species, namely Erman's birch and the white birch (Betula tauschii), "Maksimovich" alder and the Manchurian alder (Alnus hirsuta), the "Hulten" (Salix hulteni) and Sakhalin (S. sachalinensis) willows, the Sakhalin cork tree, the mulberry, the Siberian mountain ash (Sorbus sambucifolia), the oriental poison oak, which forms extensive groves and which takes on a scrub form, are the predominant forest formation on Shikotan. In addition, the Kuril Dahurian larch, which is absent on Kunashir, grows here. The Kuril bamboo does not develop so robustly as on Iturup and Urup, but is represented by quite small, dwarfed forms. The absence of the Japanese stone pine, which here is replaced by the Sargent's juniper (Juniperus sargentii), and of a number of broadleaved species, namely oak, sen, elms, and some vines, in particular the tara vine, and many others, is a distinguishing feature of Shikotan by comparison with other "wooded" islands. At the same time, 116 species of plants not found on other islands have been observed on Shikotan (Vorob'ev, 1963).
The vertical zonality on the Kuril Range is insufficiently clearly, not always consistently, and not ubiquitously expressed. Botanists, in particular D. P. Vorob'ev (1963), distinguish six vegetation zones on the islands: 1) broadleaved forests (the south of Kunashir, the southern and the central parts of Iturup); 2) dark coniferous forests (Kunashir, the south of Iturup, and partially Shikotan); 3) Erman's birch stands (Kunashir, Iturup, Urup, from the very shore of the sea); 4) Japanese stone pine (nearly all of the Greater Kuril Range from the southern to the northern islands, not infrequently in combination with elfin groves of "Maksimovich" alder; it has its distinctive characteristics on various islands); 5) heathy woodlands (on the central and northern islands, as well as on Shikotan); and 6) the alpine tundra belt (distinctly marked on the northern islands and on the peaks of a number of volcanos). All of the enumerated vegetation zones are represented to one extent or another on Kunashir and Iturup. As one moves northward, the lower zones disappear. The Erman's birch zone is preserved on Urup and Simushir, but further north only the elfin woods and heathy woodlands remain. However, it must be borne in mind that clear boundaries between vegetation zones are lacking on the Kurils, by contrast with mountainous regions of the continent, in connection with the high humidity and cool temperatures (starting from the seashore and going up to the mountain slopes of various altitudes). Such mountain plants as the Japanese stone pine are constantly encountered at the seashore even on southern islands, to say nothing of the central and northern islands; dark coniferous trees grow in the valleys along with broadleaved trees, and the latter ascend the slopes to a height of 400 m above sea level in places. Such blurring of the boundaries of the vertical zones is even more markedly manifested in insects and other animals which are capable of moving freely. It is evidently determined in the insects by the same factors as in the plants, namely the humid conditions of existence.
The soils of the Kuril Islands are distinctive and are characterized
by multilayering which occurs as a result of periodic volcanic eruptions.
Buried layers of soil alternating with interlayers of volcanic ash are
found in sections. Vegetation has not infrequently perished following powerful
volcanic eruptions, the soils have been covered by ash, and the formation
of plant communities, and then of the soil layer has begun anew. G. V.
Korsunskaya (1958) distinguishes two principal groups of soils for the
Kuril Islands, soddy and gleyey-boggy. Soddy weakly podsolic soils are
characteristic for areas with forest vegetation. Three types of soils are
encountered in the mountains: soddy soils of the mountain slopes under
groves of Japanese stone pine and alder; high-mountain soddy soils under
short-grass mountain meadows and stunted mountain shrubs; and mountain-tundra
soils under meager mountain vegetation, arranged in patches around rocks
and rock detritus. Different variations of gley soils, namely turfy-gleyey
dry, soddy-meadow, turfy, and moist turfy-gley soils are characteristic
for the crowberry mats, short-grass meadows, and boggy areas.
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