Life strategy of the Korean pine (Pinus koraiensis Sieb. et Zucc.) in the old-growth Korean pine-broadleaved forest, Southern part of the Sikhote-Alin Mountain Range
To study life strategies of tree species is necessary for formation of knowledge about processes occurring in forest ecosystems, prediction of succession changes, as well as for addressing issues related to biodiversity and sustainable species coexistence. In this regard, the aim of this work was to describe the features of Pinus koraiensis life strategy associated with the passage of trees through different age stages. The research was conducted on the territory of the Sikhote-Alin mountain range (44°01'35,3"N, 134°12'59,8''E) on two permanent sample plots (1.5 ha and 10.5 ha). We measured the diameter at breast height, tree height, age stage and vitality for each Pinus koraiensis tree. In total, 2810 plants were recorded during the growing seasons 2010-2015. We also took increment cores (648 samples) from most trees. Using the data, we defined the absolute age of trees and described the ontogenetic structure of population. Using the "boundary-line release criterion method", we reconstructed the stand disturbance history beginning from 1460. Comparing the obtained results, we found that P. koraiensis has a C-strategy. Trees of the species reach the height of 38 m, the diameter up to 150 cm and the absolute age up to 527 years. The periodicity of mast seed production is 4 and 10 years. Root system of trees in mountain forests is shallow. We revealed no severe stand-replacing disturbances are not revealed. Decades with a maximum number of trees showed releases: 1561-1570, 1681-1690, 1731-1740, 1761-1770, 1811-1820, 1841-1850, 18811890, 1941-1950, and 1981-1990. The beginning of life of most trees is associated with the decades of maximum releases. The study also found that factors affecting survival and development of plants change with passing age stages. The number and placement of immature and virginal plants is determined by lighting conditions, i.e., the presence or absence of canopy gaps. For immature plants, not so much light is required for development, so they accumulate under the stand canopy, and their number is relatively large; the maximum age reaches 110 years. We showed that for virginal plants, much more light is needed for development, so they are considerably rare in comparison with immature plants. The maximum age of virginal plants is 260 years. In general, plants reach the stand canopy in several periods of rapid growth after release, thus only single individuals survive to the final phase of the virginal period. We established that further survival and placement of generative plants depends on the disturbance history of the stand (how gaps were located in the canopy of the stand), the presence of rot and other stem damages, and conditions which are determined by the topography (moisture and temperature regimes). Accumulation of plants occurs in the middle-aged generative period. We demonstrated that P. koraiensis population in the old-growth forest is stable and its existence depends on the combination of many elements of the forest community. Taking into account the duration of life of trees, formation of a stable population requires a very long time (1000-1200 years). Since plant species have a long life span and reach a considerable size, they play an important role in shaping the environment of Korean pine-broadleaved forests.