In recent time, Sikhote Alin, as a territory with unique3 natural complexes, moreover characterized by rare preservation, rightfully deserves the close attention it receives from the world’s biologists and ecologists. This region is undoubtedly one of the key ranges for the biosphere, since the exclusive wealth of the Earth’s bioinformational resources are concentrated here on genetic, population and ecosystematic levels. Suffice it to mention the tiger, the relict “host” of this unique ecosystem.
   The formation period of this ecosystem is not subject to direct measurement. For at least tens of thousands of years, the boundary between the subarctic and subtropical natural-climatic zones passed here (periodically and alternately migrating to the south and north) to form natural complexes with unusually contrast combination of biological components. Given the leading role of the global climate on formation of these complexes, the mountain relief that complicated the climate latitudinal component by its altitude zonality had a major impact on formation of these complexes. The proximity of the ocean had certain significance, too. The landscape diversity of these continental outskirts of Asia was also caused by its tense tectonic life over at least one hundred million years, accompanied by volcanism and concomitant diversified rock formation.
   Like all mountainous regions, Sikhote Alin was initially assimilated by man along valleys of large rivers, primarily the Amur and Ussuri, and along fertile plains of lower reaches of medium-size rivers, such as Aniui, Khor, Bikin and Ussurka. The first centers of civilization arose also near convenient sea harbors in near-estuary river sections of the sea basin. Active advance of civilization to the upper reaches of rivers in this area began relatively recently, 70-80 years ago with appearance of the first mines.
   Overall advance on inland Sikhote Alin began quite recently, 25-30 years ago, along with rapid development of the timber sector in the region. Over a short period of active mining of natural resources, ecological balance in the region still had no time to be strongly disturbed, and yet was profoundly shaken.
   A real ecological crisis may break out here only after the core elements of Sikhote Alin as an integral mountain-taiga ecosystem, which in our view the natural complexes of its central part essentially are, will have been disturbed. Territorially, this region, encompassing from the northwest the upper reaches of Aniui River, the left tributaries of Khor River (Kabuli, Sukpai, Katen, Chuken, Matai), and also Bikin River and the right tributaries of Bolshaya Ussurka River (Dalniaya, Armu, Kolumbe). From the southeast, it includes the basins of Samarga, Edinka, Veniukovka, Kabaniya, Peya, Svetlaya, Kuznetsov, Burlivaya, Sobolevka, Maximovka, Amgu, Kema, Tayozhnaya and Serebrianka Rivers
   Today, specifically this region attracts the attention of numerous industrialists, and not only Russian, but foreign as well, including timber specialists. This is not surprising, since these very territories in Sikhote Alin have been assimilated least in mining natural resources. We found no special references in the literature that estimates the ecological significance of the area for preserving the overall ecological balance of Sikhote Alin. We offer our relevant ideas for subsequent familiarization to ecologists and politicians.
   First, the above-cited area is the most elevated section or apical center of the entire region. Areas with maximal annual precipitation have been assigned to the apical center of Sikhote Alin. This fact shows that the main water flow in the entire alpine-taiga ecosystem of Sikhote Alin, and also a significant part of the water flow in the ecosystem of the Ussuri basin, are formed and regulated in the central area of Sikhote Alin. If you analyze the map of isolines of annual precipitation for the entire Amur-Ussuri region (Climatic Atlas, 1960) you would readily see that the area of Central Sikhote Alin is unique on the continent as regards total precipitation within a radius of at least 1,000 km.
   The boundary of two major botanico-geographic zones, namely the alpine-south taiga and conifer-larchwood forest zones, pass along the southern outskirts of this apical center of Sikhote Alin (after B. P. Kolesnikov, 1969). Representatives of the recent floristic school, V. A. Nedolushko (1965) for example, adhere to a proximate boundary. In distinguishing in Sikhote Alin the boundary between two floristic provinces (Manchurian and Okhotsk-Kamchatka), Nedoluzhko, like his predecessors, draws the boundary of the Okhotsk flora range in the form of a strip that encompasses the most mountainous section of the region to descend from the northeast to the south west approximately to the latitudes of the right-hand tributaries of Ussurka River.
    It is common knowledge that boundaries of geobotanical regions are simultaneously boundaries of various faunistic complexes. In alpine Sikhote Alin, the principal environment-forming components and simultaneously indicators of contacting faunistic complexes are combinations of arboreal plants: in the first case, the cedar-oak pair, and in the second the fur, spruce and (or) larchwood triad.
   Unlike recent florists and geobotanists, V. K. Arseniev (famed Russian traveler and universally recognized geographer) perceived the boundary between the Okhotsk and Manchurian biogeographic regions approximately along the line from the lower reaches of Hungari River via the middle reaches of Aniui River and then via Samarga River in the direction of Cape Olympiad (Arseniev, 1912). The Arseniev and Kolesnikov boundaries do not coincide by almost 200 km. What is the matter?
   The matter is that biogeographic boundaries in alpine regions are seldom distinct. As a rule, a vast border zone including displacement of contacting biotas accompanies them. As it moves to the north, the “southern” flora range, saturated with subtropical elements, having encountered in the central part of Sikhote Alin altitudinal obstacles, would “get stuck” in a labyrinth of alpine ridges to split into a mosaic of contrast landscapes to finally attenuate on reaching the “Arseniev line”. In sites where the mountain barrier declines, the “southern” flora would circumvent, as it were, the central mountain massif to split into two “sleeves”. In this case, the western “sleeve” would cross the Bikin River Basin in its middle section to extend northward already as a narrow strip along the lowlands of the right bank of Amur River. The other eastern “sleeve” would extend as an intermittent rivulet along the Japan Sea coast, hardly reaching the latitude of Sovetskaya Gavan. In both cases, the northward movement is accompanied by gradual “wedging out” of some subtropical cenoelements in the southern flora. In this way, the complex structure of alpine ridges and river valleys in central Sikhote Alin caused the appearance of a contact zone between the two biotic complexes in the form of a rather vast area with interpenetrating unusually contrast landscapes.
   The Bikin latitudinal anomalous zone is the geographic and functional center of this boundary region and simultaneously the key element of the entire alpine-taiga ecosystem of Sikhote Alin.
   Being a unique geologic-geophysical, geomorphologic and finally landscape phenomenon, the latitudinal anomalous zone with the incorporated Bikini basin ecosystem do not only naturally organize but, given the existing economic and political situation in the region, actually determine the ecological stability of the entire Amur-Ussuri Region.
   A major circumstance that predetermined the strategic role of the Bikin latitudinal zone in the ecological welfare of the vast alpine-taiga zone was the fact that already millions of years ago two thick subparallel latitudinal-oriented mountain ridges  (with swells comprising tectonic-magmatic dome chains), separating the Sikhote Alin mountain land into two meridional megaslopes, the northern and southern slopes, had outcropped along the tectonic faluts that restricted that zone. At present, these latitudinal ridges, like a tall double fence, partition the middle part of the alpine-taiga ecosystem into two regions approximately equal in area. As a result of this natural partition precisely in the middle of the Bikin valley, and also along the Japan Sea coastal zone, the key sites of the entire cedar-broadleaf forests are situated in the range places where the ridges abruptly decline to restrict the anomalous zone.
   By shutting off these natural ecological “corridors” (pathways), along which animals perform their relatively short cyclic movements (migration cycles), and also the slow, but highly important intrapopulation gene exchange, may cause artificial dismemberment of the still single alpine-taiga ecosystem with inevitable loss of qualities inherent only in the entire system. Preservation of continuity of the cedar forest range in the middle reaches of Bikin River would largely determine the stability and even the very existence of numerous subtropical biota elements to the north of Bikin Valley, within the bounds of the Khor basin and the right bank of Lower Amur.
    The anomalous latitudinal structure also predetermined the forming of a relatively isolated massif of cedar-broadleaf forests that pass into cedar-fir forests to extend along the very Bikin valley to the east and virtually emerging onto the Japan Sea coast. Periodically, during climate warmings (cycles occurring every thousand years), these forests along Bikin River fully lock their range from the east.
    All these structural specifics of Bikin Valley had predetermined the exclusive uniqueness of the component natural complexes. Probably, in this very river valley features of interpenetrating of maximally contrast (northern and southern) representatives of flora and fauna species are most pronounced.  (Naturally, contrast combinations of biota elements are characteristic of the entire central Sikhote Alin, but they show in Bikin most contrastingly and on the most massive scale). For instance, in the Bikin Valley you may see larchwood entwined with grapes, or observe representatives of the tropical Orchid family alongside the mountain cranberry, a representative of northern flora. Here, the runner Shrenka, a typical inhabitant of the tropics, may live alongside the common adder, and the moose, the giant of the northern taiga, come across a guest from the tropics, the turtle. Despite their amazing diversity, these boundary biocommunities are highly unstable and unbalanced. Even insignificant impact of man on these unique landscapes inescapably causes their spontaneous and rapid degradation with formation of poor secondary biocommunities. Degradation of landscapes in river upper reaches is particularly dangerous. Such degradations would inevitably spread to the lower reaches of river basins in the form of destructive floods, climatic anomalies, forest diseases, and decrease in wildlife population, something repeatedly observed in highly diverse biogeographic regions around the world, and something well known to all ecologists. The major ecological corridors in Central Sikhote Alin are shown in the scheme.
   The scheme of structural and functional composition of the Sikhote Alin ecosystem presented herein largely evidences the exceptional ecologic significance of its central part, primarily that of Bikin River valley. To ignore this fact would mean to be indifferent to the unique nature we have begotten. By destroying it, we could at best slightly improve the economic situation of some people, but at the same time strongly risk losing forever just another invaluable “piece” of the life of each and all that cannot be measured by money.

A. PANICHEV. Pacific Institute of Geography, Far East Science Branch, Russian Academy of Sciences.

A. GULKOV. Far Eastern State Technical University.