Study site

Study site covered overall area of Restoration Center for Endangered Species (255 ha) in Yeongyang (N36°38'10.30 E129°09'13.69), which was located at the northeastern part of Gyeongbuk Province (Fig. 1). Topographically, approximately 77% of the site area were mountainous (slope >15°), but there were plain and stream inside as well. The altitude ranged from 235 m to 568 m (376 m on average). The soil was classified as inceptisols in the USDA soil taxonomy, and as a brown forest soil type with a sandy loam to loamy sand texture in the Korean forest soil nomenclature. The climate was cool temperate with a hot humid summer and a cold dry winter. The concentrated precipitation event generally occurred in the middle of summer. The average air temperature, precipitation, relative humidity, and wind speed were 13.3°C, 1,032.6 mm, 63.0%, and 2.9 m·s^-1 during the last 10 years, respectively. The highest and lowest air temperature was 37.7 and –15.0°C throughout a year.

Floral data collection and analysis

Vascular plants were investigated in May, August, and September 2019 and in May and July 2020. The field survey was based on the line transect method (Braun-Blanquet, 1964), which targeted on the area of Restoration Center for Endangered Species. Any vascular plants were identified in the field using the characteristics of organs (e.g., leaves, flowers, and stems) according to Lee (2003) unless further specification was required with a microscope in detail.

The nomenclature for each taxon followed the national species list from National Institute of Biological Resources. The enforcement regulations by Korean Ministry of Environment were applied to specify the legally protected (endangered or Korea endemic) and exotic plant species. In terms of exotic species, further classification was conducted by the possibility of invasion to the native ecosystems (invasive-exotic, potentially invasive-exotic, and non-invasive) according to a previous assessment by Korean Ministry of Environment (2014b). Urbanization and naturalization indices were calculated with the equations purposed by Yim and Jeon (1980), Numata and Kotaki (1975). Meanwhile, floral data before the establishment of the center (Korean Ministry of Environment, 2014a) was cited and restructured to make a direct comparison with data from the present study. In particular, the classification and the lists of legally protected or exotic species were adjusted to the same versions for those of the present study.

Total floral taxa

There were 418 floral taxa (98 families, 261 genera, 384 species, 4 subspecies, 27 variations, and 3 formations) in the study site (Table 1). Magnoliophyta occupied the largest proportion (95.2%) of the floral taxa, followed by Pteridophyta (3.6%) and Pinophyta (1.2%). The dominant families within Magnoliophyta were Asteraceae (51 taxa), Fabaceae (25 taxa), Rosaceae (25 taxa), Poaceae (24 taxa), Liliaceae (17 taxa), and Lamiaceae (16 taxa), while the dominant genera within Magnoliophyta were Artemisia (9 taxa), Carex (8 taxa), Persicaria (8 taxa), Viola (8 taxa), Dioscorea (6 taxa), and Quercus (6 taxa). On the other hand, the dominant family and genus within Pinophyta were Pinaceae (4 taxa) and Pinus (2 taxa), whereas those within Pteridophyta were Dryopteridaceae (4 taxa) and Dryopteris (4 taxa). Full list for the floral taxa in the study site was provided in Supplementary Table 1.

In a quantitative manner, our result differed from previous studies investigating the other mountainous areas in Yeongyang. For instance, Chung et al. (2007) found 513 floral taxa (91 families, 318 genera, 424 species, 3 subspecies, 73 variations, and 13 formations) in Geomma-san, while Chung et al. (2008) observed 437 taxa (88 families, 267 genera, 384 species, 4 subspecies, 43 variations, and 6 formations) in Podo-san. Oh et al. (2015) also reported 582 taxa (94 families, 307 genera, 508 species, 4 subspecies, 61 variations, and 9 formations) in Ilwol-san. Such difference between the present and previous studies might occurred because the study site has undergone anthropogenic disturbances such as agriculture (Korean Ministry of Environment, 2014a), in contrast to Geomma-san, Podo-san, and Ilwol-san. The presence of agricultural fruit trees (e.g., Diospyros kaki Thunb. and Ziziphus jujuba Mill.) in the study site possibly supports this explanation (Supplementary Table 1). Relatively low altitude of the study site (study site: 376 m; Geomma-san: 1,017 m; Podo-san: 748 m; Ilwol-san: 1,219 m) might also contribute to such differences in floral taxa (Yirga et al., 2019).

The total number of floral taxa from the present study was larger than that of a study for the same site before the establishment of Restoration Center for Endangered Species (102 families, 331 species, 4 subspecies, 25 variations, and 1 formation) (Korean Ministry of Environment, 2014a). Such increase in floral taxa was remarkable in Magnoliophyta (from 344 to 398 taxa). On the contrary, the number of family was lower in the present study than in Korean Ministry of Environment (2014a) as a result of the disappearance of 5 families (Eucommiaceae, Ginkogoaceae, Grossulariaceae, Malvaceae, and Orobanchaceae) and the new appearance of 1 family (Juncaceae). These changes might reflect the potential reorganization in plant niche and vegetation composition after the anthropogenic event due to the construction (De Martis et al., 2016). Given that the present study covered a relatively short period of time, this aspect should be confirmed through further monitoring in the long-term.

Legally protected species

A total of 6 legally protected species were detected in the study site (Table 2). Of them, the endangered species included Cypripedium macranthos Sw. (grade II by Korean Ministry of Environment). The endemic species consisted of Aconitum pseudolaeve Nakai, Eleutherococcus divaricatus var. chiisanensis (Nakai) C.H. Kim & B.-Y. Sun, Lonicera subsessilis Rehder, Paulownia coreana Uyeki, and Weigela subsessilis (Nakai) L.H. Bailey.

One result deserving highlight is that the detected endangered species, C. macranthos, did not occur in the previous study on the same site, while the number of endemic species remained unchanged (Korean Ministry of Environment, 2014a). This new inclusion might result from either seed disposal from the outside of the study site or simple unidentification during the previous study. The presence of the endangered species was comparable to previous studies in Yeongyang, which revealed several endangered species (grade II by Korean Ministry of Environment) such as C. macranthos in Geomma-san (Chung et al., 2007) and Eleutherococcus senticosus (Rupr. & Maxim.) Maxim. and Paeonia obovata Maxim. in Podo-san (Chung et al., 2008); however, no endangered species was found in Ilwol-san (Oh et al., 2015). As C. macranthos has been unreported around the study site until the present study, detailed investigations should be necessary to ensure whether that species habituate in the surrounding area of Restoration Center for Endangered Species.

Exotic species

The number of exotic species was 33, comprising 4 invasive-exotic, 4 potentially invasive-exotic, and 25 non-invasive species (Table 3). The invasive-exotic species consisted of 3 North American species (Ambrosia artemisiifolia L., Ambrosia trifida L., and Aster pilosus Willd.) and 1 European species (Lactuca scariola L.). The potentially invasive-exotic species contained 2 North American species (Amorpha fruticosa L. and Bidens frondosa L.), 1 European species (Festuca arundinacea Schreb.), and 1 Eurasian species (Rumex obtusifolius L.). These species were either herbaceous weeds living along road- and stream-side (A. artemisiifolia, A. trifida, A. pilosus, L. scariola, B. frondosa, F. arundinacea, and R. obtusifolius) or plantation shrubs (A. fruticosa). Meanwhile, the non-invasive species were comprised of 9 North American species (Conyza canadensis (L.) Cronquist, Coreopsis lanceolata L., Cuscuta campestris Yunck., Erigeron annuus (L.) Pers., Euphorbia maculata L., Geranium carolinianum L., Helianthus tuberosus L., Oenothera biennis L., and Robinia pseudoacacia L.), 9 European species (Cerastium glomeratum Thuill., Fallopia dumetorum (L.) Holub, Medicago sativa L., Poa pratensis L., Rumex crispus L., Taraxacum officinale F.H. Wigg., Thlaspi arvense L., Trifolium pratense L., and Trifolium repens L.), 3 Eurasian species (Avena fatua L., Carduus crispus L., and Dactylis glomerata L.), 2 Tropical American species (Amaranthus retroflexus L. and Galinsoga quadriradiata Ruiz & Pav.), 1 South American species (Bidens pilosa L.), and 1 Asian species (Melilotus suaveolens Ledeb.).

Urbanization (proportion of exotic floral taxa in the study site to that in the entire country) and naturalization (proportion of exotic floral taxa to total floral taxa in the study site) indices were 9.9 and 7.9%. These values slightly exceeded the findings from Chung et al. (2005; 2007; 2008) in Yeongyang (urbanization index: 6.3-9.7%; naturalization index: 3.6-4.1%) as well as the indices prior to the establishment of the center (urbanization index: 7.8%; naturalization index: 7.2%) (Korean Ministry of Environment, 2014a). Moreover, the proportion of both invasive-exotic and potentially invasive-exotic species increased 1.5-fold, comparing it to that before the establishment of the center (Fig. 2). These results demonstrate that the study site might have been subjected to the anthropogenic disturbances like agriculture and the construction of the center, as suggested by the total floral taxa data (see total floral taxa subsection). Considering that the newly appeared exotic species (e.g. L. scariola) are generally tolerant and invasive to the unvegetated bare environments (Kim et al., 2013), the increasing trend in invasive species might be closely related to the recent construction of infrastructure, such as parking lots and roads across the study site.

Concluding remarks

The present study exhibits a total of 418 floral taxa (98 families, 261 genera, 384 species, 4 subspecies, 27 variations, and 3 formations) around the area of Restoration Center for Endangered Species in Yeongyang, Gyeongbuk Province. The flora in the study site particularly contained 1 endangered species and 5 Korea endemic species as well as 33 exotic species consisting of 4 invasive-exotic, 4 potentially invasive-exotic, and 25 non-invasive.

Several changes were detected relative to the data before the establishment of the center. In particular, the total number of floral taxa increased by 16%, although several floral families (Eucommiaceae, Ginkogoaceae, Grossulariaceae, Malvaceae, and Orobanchaceae) were faded out in the present study. Additionally, 1 endangered species (C. macranthos) newly occurred, and the proportion of invasive and potentially invasive species was 1.5-fold elevated. Overall results imply potential alterations in floral community, which might be related to the recent establishment of the center at the study site. Subsequent studies should be required to confirm and track the potential floral changes in the future.