Data of large-scale landscape-ecological survey performed on the test ground in the vicinity of the Mendeleev Volcano (Kunashir Island, South Kuril Ridge) were used for empirical-statistical modeling of forest ecosystems characterizing one of the initial stages of geological history of the continental biosphere formation in the Pacific Mobile Belt. The causal mechanisms for the lowering of the boundaries of altitudinal bioclimatic belts and the southward shift of natural zones on extratropical Neo-Pacific islands compared to the neighboring continent were revealed. The evolutionary significance of the insular-arc bioclimatic system is characterized. Two phenomena of structural-functional organization of the Mendeleev volcanic landscape have been revealed. First, there is an exceptionally high system-forming role of forest phytobiota in the formation and development of young volcanic landscapes. The forest communities of the insular Neo-Pacific in the south of the boreal belt are characterized by an annual turnover of plant matter falling into the category of intensive metabolism and being typical only of subtropical forests by the zonal standards. Second, the intense annual turnover of the above-ground phytobiota and the high rate of the entire biological cycle in the southern Kunashir landscapes are the main factors of their stability under the conditions of “cold” oceanicity and, together with magmatic geotherms, contribute to the formation of subboreal “climatically unjustified” forests. The energy bases of productivity of forest communities of the insular-arc Neo-Pacific have been analyzed as a focus of local and regional diversity of terrestrial ecosystems, which develops further on the continent. The mechanisms of formation (at the topological level) of new intrazonal types of ecological systems, which serve as the driving force of evolutionary processes, have been revealed. It is shown that evolutionary tendencies in plant cover emerge already at the initial, volcanogenic stage of formation of the continental biosphere.Keywords: biosphere, insular forest ecosystems, structure, productivity, biological cycle, empirical-statistical modeling.