The main forest-forming species of broad-leaf—cedar forests is the Korean pentacone pine, called both in literature and everyday life the Korean cedar, apparently due to its nut-bearing property. P. koraiensis is a typically Far Eastern species that does not grow elsewhere in Russia.
Forests with prevalence of P. koraiensis
had already 40-45 years ago ranked first in Primorye in lumber reserves
and second in area after Picea ajanensis and Abies nephrolepsis forests.
Broad-leaved—cedar forests (hereinafter referred to as “cedar forests”)
differ from all other forest formations of Primorye in richness of specific
composition and complex age and restoration dynamics. Sometimes up to twenty
tree species take part in cedar tree stock on one hectare, and up to 80-100
species in corresponding shrub and grass tiers. The commonly concomitant
species in cedar forests are Tilia amurensis, T. mandshuriensis, Querqus
mongolica, Betula costata, Acer mono and Ulmus lacciniata, and in the south
also Micromeles alnifolia, Carpinus cordata and Kalopanax sempervirens;
in valley cedar forests, concomitant species are Ulmus japonica, Fraxinus
mancshurica, Phelodendron amurense, Juglans mandshurica, Populis spp, etc.
The liana Vitis amurensis, Actinidia kolomicta and A. arguta (in the south)
are widespread everywhere in cedar forests. Such medicinal plants as the
widespread Eleutherococcus senticosus and the still preserved wild Panax
ginseng are extremely popular among the public.
Alpine cedar forests occupy a major area of this formation. They grow on slopes of different exposition and steepness to rise in southern Primorye to an average of up to 600 m, and in northern Primorye up to 300 and occasionally 400 m.
Cedar forests mixed with oaks, and sometimes also pure cedar forests of low productivity (class qualities V and occasionally Va), grow on watershed ridges and over preferentially southerly steep slopes with fine rocky soils.
Cedar forests with underbrush of Corylus mandshurica, Lespedeza bicolor, Rhododendron macronulaatum with more developed grass cover, in which small ferns are particularly perceptible, form on bulging valleys at margins of alpine plateaus and on southerly slopes near watersheds. The tree stocks include oak, spruce small-leaf maple, and less often other species; however, by maturity age and by overmaturity of the main cedar generation, concomitant species die off, and then cedar obtains absolute dominance in the tree stock, whose average class is III, and whose timber reserves may reach 600 cu. m/ha.
These two cedar forest groups occupied about 5% of the area of Primorye cedar forests, but are presently preserved chiefly in sanctuaries, protective zones and sites, and other protected territories.
The largest areas (up to 60%) in cedar forests were occupied by a group of cedar forests with considerable share of T. amurensis and B. costata, which are still partially retained on slopes of all directions except steep southerly slopes, on weakly sloping terraces and on bulging valleys. The admixture of concomitant species may reach 50% of the trunk timber reserve. The class of tree stocks is normally III, and occasionally III,5. The timber reserves in the best tree stocks amount to 500-600 cu. m/ha.
Directly adjoining this group are cedar forests growing on gently sloping lower sections of slopes of all expositions with permanently sufficient humidification. They are characterized by well-developed underbrush of diverse shrubs and by rich grass cover. The lime and birch also take part in the tree stock, albeit the admixture of other species significantly increases as well. The timber class is III-II, and timber reserves amount up to 600 cu. m/ha. Precisely these two cedar forest groups suffered most in years of so-called conventionally solid cuttings, when cedar was fully cut to leave concomitant species intact. This is how recent forests with prevalence of Tilia amureensis, Betula costata and partly mixed larchwood forests had chiefly originated. Natural restoration of cedar prevalence in these forests has been delayed for many decades, and in some places where lumbering technology was rudely violated, it may now be possible only artificially.
Valley cedar forests occupy relatively small areas on river valley terraces.
Cedar forests with well-developed shrub tier of Corylus heterophylla and Phyladelphus tenuifolius grow on elevated sites of terraces located above the flood plain.
From 12 to 15 concomitant species, including Fraxinus mandshurica, Ulmus japonica, Juglans mandshurica, Tilia amurensis, Padus maakia, etc. take part in the tree stocks. Their grade ranges from III to II, and trunk timber reserve is up to 350-400 cu. m/ha.
Cedar forests develop on transitional seldom flooded or flooded terraces, and moisture-loving species, e.g. Syringa amurensis, Lonicera spp, Sorbaria sorbifolia, Cacalia spp, Aconitum spp, Urtica spp, Angelia spp, etc. prevail in their underbrush and grass cover. The principal concomitant species are Frasinus, Ulmus and Populus. The tree stock grade is III-IV, and the timber reserves are up to 300 cu. m/ha.
P. koraiensis often occurs in both these cedar forest groups.
Despite the fact that some valley cedar forests are included in protective zones, they also strongly suffered from industrial cuttings. When cedar is chopped, valley cedar forests are replaced by mixed broad-leaf forests, in which natural cedar restoration is highly impeded.