Species composition

Based on voucher specimens collected in Oeumsan Mountain area, vascular plants of this region were identified to be 509 taxa (436 species 4 subspecies 57 varieties 12 forms) that belong to 98 families, 301 genera (Table 2, Appendix 1), which corresponded to 12.5% of 4,071 vascular plant taxa of South Korea (Lee, 1996a), 28.3% of 1,796 vascular plant taxa in Gangwon-do (Gangwon-do, 2010) as well as 54.1% and 59.1% of 940 and 861 vascular plant taxa in Hongcheon-gun and Hoengseong-gun, respectively (Gangwon-do, 2010). Thus, species diversity in this region was found to be relatively high. On the other hand, these results were significantly different from 259 and 133 taxa in these regions reported by Lee and Jeon (2002) and Eom et al. (2009), respectively, which seemed to be due to the in-depth surveys conducted for this study through various routes over the course of 2 years.

Table 2.

The abridged list of the plants in Oeumsan Mountatin.

Wild plants with the highest proportion of occurrence in Oeumsan Mountain were Compositae, including 52 taxa, followed by Gramineae with 39 taxa, Rosaceae with 27 taxa, Leguminosae with 25 taxa, both Ranunculaceae and Polygonaceae with 21 taxa, and Liliaceae with 20 taxa.

Among the vegetation of the Oeumsan Mountain forests, Quercus mongolica, Quercus variabilis, and Acer pictum subsp. mono were dominant, and climbing plants such as Rubus coreanus, Rubus oldhamii, and Tripterygium regelii were distributed in areas with a poor upper canopy. Previous studies also reported that Oeumsan Mountain had plant species mostly belonging to the family Fagaceae (Lee and Jeon, 2002), and Rubus coreanus, Actinidia polygama, Tripterygium regelii, and Actinidia arguta were also commonly found (Eom et al., 2009), which were similar to the results of our study.

Since Oeumsan Mountain is relatively perilous and steep, it seems that general climbers tended not to frequently visit this mountain. However, there are forest roads and military roads at the top of the southern slope, leading to military bases, and Jungang Expressway and a national highway are adjacent to the east and west from the peak, respectively. It is predicted that these would gradually increase indirect disturbance. Moreover, there were some shooting ranges, transmitting towers, heliports, and training fields inside and around the forests due to regional characteristics, and there were also military training facilities and human trampling in some areas, which have resulted in devegetation of herbaceous species. In addition, there were forest roads to military bases that were expanded at the top of the area, leaving cut slopes, where vegetation was poorly established. This led to collapses of soils and rocks, resulting in damage to vegetation of neighboring forests. Therefore, these regions need to be multilaterally managed considering, regional characteristics, in order to conserve the plant resource of the region.

Endemic plants

In the 509 taxa identified from the survey area, there were 9 taxa of endemic plants that belong to a total of 7 families 9 genera including Populus tomentiglandulosa, Salix koriyanagi, Aconitum pseudolaeve, Clematis trichotoma, Asarum versicolor, Corydalis lineariloba, Eleutherococcus divaricatus var. chiisanensis, Sillaphyton podagraria, and Abeliophyllum distichum (Table 3), which corresponded to 2.5% of 360 taxa of endemic plants in South Korea (Chung et al., 2017). Of these, Populus tomentiglandulosa and Salix koriyanagi were found at low altitude areas near the beginnings of hiking trails, and Aconitum pseudolaeve, Clematis trichotoma, Eleutherococcus divaricatus var. chiisanensis, and Sillaphyton podagraria often were distributed in mid-forest areas inside forests and slopes of forest roads. Asarum versicolor and Corydalis lineariloba were found to inhabit around valleys in low-lying lands. On the other hand, Abeliophyllum distichum, known to inhabit in Gyeonggi-do, Chungcheongbuk-do, Gyeongsangbuk-do, and Jeollabuk-do (Chung et al., 2010; Shin et al., 2010; Lee et al. 2014) has been reported to maintain its population mostly through vegetative propagation (Kang et al., 2000; Kim and Kim, 2004; Shin et al., 2010), due to a low germination rate and no simultaneity in germination (Yoo and Kim, 1993). In addition, this species is known to inhabit in areas with relatively poor growing conditions, such as between the rocks, around farmlands, or boulder zones along mountain streams (Lee, 1976). The Abeliophyllum distichum plants found in Oeumsan Mountain during this study were the first documented case in Gangwon-do. Four individual plants were found between the rocks in a mountain stream at Sammachi-ri of Hongcheon-gun. According to an inquiry survey, a small number of plants of this species were introduced around buildings in a Buddhist temple nearby in the past, but there has been no artificial planting nearby the stream. To reveal the origin of Abeliophyllum distichum in Oeumsan Mountain, further investigation is needed to determine whether this species was originally planted as ornamentals at the Buddhist temple and then naturalized in the corresponding area resulting from rain spells and typhoons, or this region is the natural northern limit of this species. If this is found to be a natural population, it should be studied for genetic diversity and biogeographic characteristics, targeting the entire population of this species in South Korea.

Table 3.

List of endemic plants in Oeumsan Mountain.

Endangered and rare plants

Abeliophyllum distichum was the only endangered plant species found in the survey area, which was designated as a Grade 2 endangered species by the Ministry of Environment. There were 8 taxa of rare plants that belonged to 7 families and 7 genera, which accounted for 1.4% of the total 577 taxa of rare plants in South Korea (Korean National Arboretum, 2008b), as well as 20.0% and 32.0% of 40 and 25 taxa of rare plants in Hongcheon-gun and Hoengseong-gun, respectively (Gangwon-do, 2010). When classified according to the grades of rare plants, critically endangered species were Abeliophyllum distichum; least concerned species were Eranthis stellata, Aristolochia contorta, Rodgersia podophylla, Viola albida, Viola diamantiaca; and data deficient species was Eleutherococcus divaricatus var. chiisanensis (Table 4).

Table 4.

List of endangered wild and rare plants in Oeumsan Mountain.

Of the identified taxa, Aristolochia contorta and Eleutherococcus divaricatus var. chiisanensis were found around beginnings of hiking trails, and Abeliophyllum distichum was detected in boulder areas of a mountain stream. In addition, Eranthis stellata, Rodgersia podophylla, and Scopolia japonica inhabited areas with various sizes of rocks in a valley within a forest, and Viola albida and Viola diamantiaca were on the slope to the mountaintops and ridge areas.

Floristic regional indicator plants

The floristic regional indicator plants specially designated by the Ministry of the Environment are useful taxa representing areas with similar environments, which are subdivided into 5 grades according to the area they inhabit (Ministry of Environment and National Institute of Environmental Research, 2014). Of the 509 taxa identified, 57 taxa were floristic regional indicator plants, which accounted for 4.5% of the entire 1,255 indicator plant taxa (Ministry of Environment and National Institute of Environmental Research, 2014). This result was significantly different from 19 and 9 taxa reported by Lee and Jeon (2002) and Eom et al., (2009), respectively.

Classifications of these floristic regional indicator plants are as follows: Abeliophyllum distichum for Grade V, habitats are discontinuous and isolated with the narrowest area of distribution; Anemone reflexa, Chrysosplenium ramosum, Rodgersia podophylla, and Wisteria floribunda for Grade IV, northern or southern plants usually found in one subdistrict; 9 taxa including Betula chinensis, Aconitum longecassidatum, Eranthis stellata, Spiraea salicifolia, and Viola diamantiaca for Grade III that inhabit in 2 subdistricts; 19 taxa including Dryopteris expansa, Polystichum braunii, Aquilegia buergeriana var. oxysepala, Caltha palustris, and Caulophyllum robustum were Grade II that are distributed nationwide, but mostly found in areas > 1,000 m in elevation; 24 taxa including Dryopteris crassirhizoma, Matteuccia struthiopteris, Anemone raddeana, Impatiens nolitangere, and Lonicera praeflorens for Grade I that are distributed in 3 subdistricts (Table 5).

Table 5.

List of floristic regional indicator plants in Oeumsan Mountain.

Naturalized plants

Naturalized plants refer to plant species that are not native, but have been introduced to the country via artificial or natural ways, and propagate and reproduce in nature on their own (Koh et al., 1995). A total of 35 naturalized plant taxa that belong to 13 families 32 genera were identified in this study (Table 6) including ecosystem disturbing plants, such as Rumex acetosella, Ambrosia artemisiifolia, and Aster pilosus, and their naturalized ratio and urbanization index were calculated to be 6.9% and 10.9%, respectively. Considering the naturalized ratio of Korean forest areas is 14.0% (Oh et al., 2009), it seems that the vegetation of this area has been conserved relatively well. The naturalized plants were found mostly around private residences in low-lying lands and military facilities where vehicles frequently pass by during military movements and transportation of military supplies. Amorpha fruticosa, Robinia pseudoacacia and Ailanthus altissima inhabited slopes of forest roads where vegetation of herbaceous species was poorly established, and Lepidium virginicum, Trifolium repens, and Erigeron annuus occupied relatively large areas in the open fields such as farmlands, pastures, and heliports.

Table 6.

List of naturalized plants in Oeumsan Mountain.

Rumex acetosella, Ambrosia artemisiifolia, and Aster pilosus have been controlled because they are ecosystem disturbing plants that are harmful to humans. Nevertheless, only a small number of them were found in dry fallow lands located at the edge of relatively desolate forests in low-lying lands, so that they were not considered to have significant effects on the plant ecosystem.