The Korean Peninsula is located on the Eurasian continent (33°05′32″‒43°00′52.67″ N and ~124°40′30.77″‒131°55′45″ E) and is surrounded by sea, except for the northern side. Longer (north–south direction) than it is wider (east–west direction), 70% of the territory of the peninsula comprises mountainous regions (Kwon 2003). Such geographical conditions cause the ambient temperature and precipitation to reflect the characteristics of the latitude, elevation, and land and sea distribution (Kwon 2010). Thus, the ecological conditions on the Korean Peninsula are markedly influenced by the rises in temperature at each latitude and elevation due to climate change, as well as the rises in seawater temperature causing an increase in the ambient temperature in coastal regions (Kong 1998).

The Korean Peninsula also displays a characteristic graded floral distribution, with northern lineage flora and southern lineage flora coexisting according to the climatic and topographical characteristics (Chang et al. 2016; Kong 1998). According to the classification by Takhtajan (1986) and the Chang et al. (2016), among the 13 plant spheres distributed in East Asia, the northern lineage flora correspond to the “Manchurian flora”, and the southern lineage flora correspond to the “China–Japan–Korea flora” (hereafter abbreviated as ‘CJK flora’). Manchurian species increase in distribution toward the north and decrease toward the south at the foot of the high-elevation mountainous regions at 37° N (Kong and Watts 1999), below which the distribution of Manchurian species is concentrated in mountainous regions at elevations of 800 m or above and in the refugia, which are geographically isolated regions, along the Baekdudaegan (Hájek et al. 2009; Kong 1998; Kong and Watts 1999). In comparison, the distribution of CJK species is concentrated in the southern regions below 33° N (Jeju-do and the southern coastal regions) and decreases with increasing latitude (Kong 1998). In contrast, no subtropical species have been detected in North Korea.

Over the past several decades, ongoing climate change has resulted in a severe disturbance of biological habitats and the global ecosystem due to the rise in temperature across the globe (Garamvölgyi and Hufnagel 2013; Kong 1999a). Therefore, the survival of boreal species is threatened by significant changes in the ecological conditions of their habitat (Birks and Willis 2008; Stralberg et al. 2020; Tribsch and Schönswetter 2003). The regions facing the greatest challenge in South Korea are the high-elevation regions below 37° N and the limestone fields, being inhabited by species that used to inhabit the regions in the Würm period and the periglacial period in the Korean Peninsula, through the interglacial period, and under the current conditions of a temperate monsoon climate (Kim et al. 2016; Kong 1999a; Kong 1999b; Kong et al. 2011).

The status of a divided country has prevented the investigation of the Korean Peninsula as a whole, as it has severely restricted the collection of data in the regions of North Korea. Therefore, it has been difficult to determine even the current overall distribution of Manchurian and CJK species. Consequently, the habitat characteristics determined by environmental factors with continuity throughout the territory could not be taken into account, and studies have been restricted to the regions of South Korea (Chang et al. 2017). This has posed great challenges for the development of response measures to the transnational problems caused by the changes in biological habitats and the loss of biodiversity due to climate change. A wide spectrum of studies have reported the influence of climate change on the ecosystem in South Korea (Choi and Kim 2013; Kang and Paek 2005; Kim 2012; Kim et al. 2015; Lee and You 2001; Park et al. 2008), and a similar level of investigation has presumably occurred in North Korea. However, more accurate and practical studies will only be possible once the plant species distribution trends have been analyzed for the entire Korean Peninsula as a premise for causal analysis of the changes. The construction of a database containing the points of distribution will allow the prediction of the future floral distribution throughout the Korean Peninsula using a species distribution model (Riordan et al. 2018; Wiens et al. 2009; Zhang et al. 2019). Therefore, this study aimed to construct a database using flora data collected for South and North Korea and apply it to the analysis of the current status and distribution characteristics of Manchurian and CJK plant species occurring on the Korean Peninsula.

Study area

The Korean Peninsula is located at ~33°05′32″‒43°00′52.67″ N and ~124°40′30.77″‒131°55′45″ E, on the easternmost end of the mid-latitude Asian continent, in the Northern Hemisphere (Fig. 1). Given its geographical characteristics, the Korean Peninsula is simultaneously influenced by continental and maritime climates. The average annual temperatures and precipitation levels of the Korean Peninsula during 1991–2020 were 12.8 and 8.9°C, and 1,306.3 and 912 mm in South and North Korea, respectively (Korea Meteorological Administration 2021). The elevation range in the Korean Peninsula is 0–2,750 m, and high-elevation regions are distributed mostly in the eastern and northern areas of the peninsula. Compared with other regions, these regions show more active morphogenic processes, with a lower proportion of humus in the soil. In contrast, the relatively high mean temperature and precipitation in the southern area of the peninsula induce high levels of chemical weathering and pedogenic processes, facilitating leaf decomposition and allowing for a higher proportion of humus in the soil (Kim et al. 2021). The mean distribution of elevation for latitudes increases above 37° N and peaks at 41° N (Fig. 2).

Figure 1. Map of the study area. The area north of the DMZ line shown on the map is North Korea, and the area to the south is South Korea.

Figure 2. Mean elevation by latitude on the Korean Peninsula.

The traditional geo-cultural perception of the major mountain ranges formed in the Korean Peninsula may be represented by the Baekdudaegan System (Hyeun 2000), stretching from Mt. Baekdusan (2,750 m, northern part of the Korean Peninsula) to Mt. Jirisan (1,915 m, southern part of the Korean Peninsula), with a mean elevation of 990 m and the major mountain peaks of the Korean Peninsula between them (Fig. 3).

Figure 3. Schematic profile diagram of the macroscopic topography of the Korean Peninsula.

Jeju Island, the southernmost island of the Korean Peninsula, is the largest island (1,849.2 km²) affiliated with the region. It is a volcanic island and is rich in biodiversity due to its warm climate and isolated geographical characteristics. Mt. Hallasan, located in the center of Jeju Island, is the highest mountain (1,950 m) in South Korea, forming a biome with an altitude-dependent gradient. (Dolezal et al. 2012).

The forests in the Korean Peninsula are predominantly deciduous forests, whereas coniferous forests mostly grow in the low-elevation regions subjected to afforestation. In addition, evergreen broad-leaved forests are distributed mostly in the southern coast and subalpine regions (Chang et al. 2016). Algific talus slopes and limestone fields formed by unique topographical and geological conditions serve as key habitats for unique species on the Korean Peninsula (Bae et al. 2014; Kim et al. 2016).

Construction of a flora database

To analyze the distribution characteristics of Manchurian and CJK plant species inhabiting the Korean Peninsula, a database with information regarding the localization of the plant species was constructed from 1,643,500 previously reported cases. In the construction of this database, information regarding the localization of approximately 1,440,000 cases from the National Ecosystem Survey performed by the Ministry of Environment in South Korea was used (Korea National Institute of Ecology 2019). Vector-type spatial data of the natural flora identified in the second to fourth National Ecosystem Surveys were directly provided by the Korea National Institute of Ecology. Then, using ArcGIS 10.1, integrated spatial information of plants in South Korea was constructed based on the scientific names in the national species list (https://species.nibr.go.kr/) (accessed on 7 September 2022) provided by the Korea National Institute of Biological Resources (geodetic longitude and latitude projection, EPSG 4326, WGS84 ellipsoid). For the data of species occurring in North Korea, biota information from approximately 16,000 cases was collected from published literature and converted to species localization information (Do and Im 1976; Im 1976; Im 1998; Im 1999; Im 2000; Im and Lee 2000; Im et al. 1975; Im et al. 1996). From the collected literature data, life forms, major distribution areas, sources, years, and pages were inserted into a spreadsheet-type database. When constructing the database, the common and scientific names in South Korea and North Korea were written together. The Korean and scientific names in South Korea were recorded based on the National Species List of the Korea National Institute of Biological Resources. Unlike in South Korea, plant distribution information recorded in North Korean literature is described with the geographical location specified, such as the geographical location, mountain name, river name, lake name, etc., without the geographical coordinates. After separating these geographical descriptions, location coordinates were obtained (Kim et al. 2019). The coordinates were obtained from the extracted place names using Google Server’s geocoding tool (https://developers.google.com/maps/documentation/geocoding/overview) (accessed on 7 September 2022). Finally, spatial information for plants in North Korea in the vector format was constructed using ArcGIS 10.1 based on the longitude coordinates (geodetic longitude and latitude projection, EPSG 4326, WGS84 ellipsoid). In addition, localization information for 234 boreal plant cases from the Global Biodiversity Information Facility (GBIF) database was used (GBIF 2021).

Based on the species list presented by the Oh et al. (2010) (Tables S1–5), data for 45,877 cases, including Manchurian and CJK flora species; species unique to the Korean Peninsula; and species distributed in isolated habitats, such as Baekdudaegan, limestone fields, and regions with elevations of 800 m or higher, were extracted from the constructed flora distribution database for habitat environmental analysis. The extracted data contained 7,997 cases of Manchurian plants, 16,327 cases of CJK plants, 14,716 cases of species endemic to the Korean Peninsula, 3,050 species distributed in the Baekdudaegan, 2,959 species from regions at elevations of 800 m or higher, and 828 species inhabiting limestone fields (Table 1).

Table 1 . Numbers of plant species and individuals used in the analysis.

Plants	Species	Individual
Manchurian	1,910	7,997
China–Japan–Korea	92	16,327
Endemic	97	14,716
Above 800 m	757	2,959
Baekdudaegan	226	3,050
Limestone	15	828
Total	3,097	45,877

Construction of abiotic factor variables

Temperature and precipitation data for 1970–2000 from WorldClim version 2.1 (WorldClim 2021) were used to construct the climatic variables. The package ‘ENVIREM’ of R statistics 4.13 was used to estimate the warmth index, coldness index, and continentality from the data (Title and Bemmels 2018).

The hydrological modeling tool in ArcGIS 10.1 was used to obtain the digital elevation model (DEM) in the construction of the Baekdudaegan spatial data. The principle of extraction was as follows: the fill function was applied to remove the sink and peak, which may have influenced watershed data extraction using the DEM. The ground surface-water flow from the DEM ridges and peaks was then estimated in eight directions to which the flow direction function could be applied. To obtain the cumulative direction values, the Flowaccumulation function was applied, and among the calculated cumulative flow values, the data of the divide and primary channels were extracted based on the stream systems and watershed with a threshold of ≥ 2,000. The finalization was based on the localization of ‘daegan’ recorded in the Sangyongpyo (Hyeun 2000), a historical book on the mountain systems of the Korean Peninsula.

Analysis of distribution characteristics

The Korean Peninsula distribution characteristics in terms of latitude, longitude, and elevation were analyzed using the extracted flora data for the Korean Peninsula. To solve the problem of skewed distribution in certain regions with high-density populations, data normalization was performed on the distributed population size against the area. In addition, the ArcGIS 10.1 program was used in the latitudinal, longitudinal, and elevation analyses to identify the correlations between plant distributions and environmental factors; Manchurian, CJK, and endemic species; and species distributed in isolated habitats, such as the Baekdudaegan mountains, limestone fields, and regions with elevations of 800 m or higher.

The package ‘plotbiomes’ in R statistics 4.13 (https://rawgit.com/valentinitnelav/plotbiomes/master/html/Whittaker_biomes_dataset.html) (accessed on 7 September 2022) was used to analyze the flora distribution across the Korean Peninsula based on the bioclimatic classification method suggested by Whittaker (1975), which takes into consideration the temperature and precipitation variables for the classification of biomes. Additionally, the representative species inhabiting the Korean Peninsula, including two endemic, two CJK, and three Manchurian flora species, were selected to analyze the biome distribution by species. The representative species were selected from the species designated by the Oh et al. (2010).

Statistical analysis

One-way analysis of variance (ANOVA) and Tukey’s honestly significant difference post hoc test were performed to test the differences in habitat altitude for plant species belonging to the Manchurian, CJK, and endemic groups. Factor analysis was performed to identify the environmental factors influencing the distribution of boreal and subtropical plants on the Korean Peninsula. The following nine variables were selected as the main factors for analysis: latitude, elevation, temperature, precipitation, warmth index, coldness index, continentality, slope, and aspect (Zhao et al. 2018). The results of the first analysis indicated a commonality (h2) value of ≤ 0.3, which led to the exclusion of two factors, namely slope and aspect, which had low significance. Second, factor analysis was then performed using the remaining seven variables (Samuels 2017). Elevation and precipitation showed either negative correlations with other variables or large deviations. In this case, reverse scoring was applied to prevent the calculation of a negative score in the rotated principal component analysis. The ANOVA and factor analyses were performed using the package ‘stats’ in R statistics 4.13 (https://stat.ethz.ch/R-manual/R-devel/library/stats/html/00Index.html; accessed on 7 September 2022).

Distribution of Manchurian and CJK species

The mapping of the distribution points for 8,804 cases of Manchurian and 15,725 cases of CJK species on the Korean Peninsula (Fig. 4) showed that boreal species were distributed at high densities at approximately 37‒38° N in South Korea and throughout North Korea. The density at the distribution points was high in the high-elevation mountain ranges of South Korea, presumably due to the relatively low amount of flora data for North Korea (Total count of data in South Korea = 36,866, North Korea = 2,724). Plant species were distributed in the Baekdudaegan mountains and those with high elevations of ≥ 800 m (e.g., Mt. Jirisan, Mt. Deogyusan, and Mt. Hallasan) at ≤ 36° N in South Korea, and high population densities were recorded in the Mt. Baekdusan and Kaema Plateau regions in North Korea.

Figure 4. Distribution of Manchurian and China–Japan–Korea flora on the Korean Peninsula.

CJK plants were distributed at high densities on Jeju-do (33° N) and along the southern coast (34‒35° N) of the Korean Peninsula (Figs. 4, 5A). Furthermore, the distribution density decreased as the latitude increased, and in coastal regions, compared with inland regions, the distribution reached higher latitude regions.

Figure 5. Distribution of China–Japan–Korea (A) and Manchurian (B) flora by latitude on the Korean Peninsula.

Manchurian species were observed at high densities in the regions with the highest elevations on the Korean Peninsula, including the Mt. Baekdusan and Kaema Plateau regions (40‒41° N). Furthermore, they were distributed at high densities in regions with latitudes of ≤ 37° and at 33‒35° N; 33° N in South Korea only, including Mt. Hallasan; and at 35° N, including the high-elevation mountain region of Mt. Jirisan (Fig. 5B).

The ANOVA results confirmed a significant difference in altitude between the groups (p ≤ 0.001, Table 2). Among the three groups, there was no significant difference in altitude between the Manchurian and endemic groups. In the case of the CJK group, there was a significant difference in altitude from that of the other two groups (Table 3).

Table 2 . One-way ANOVA table showing the differences in mean elevation among the three flora types (Manchurian, China–Japan–Korea, and endemic).

Source of variation	Sum of squares	df	Mean square	F	Sig.
Between groups	1,288,086,453.77	2	644,043,226.88	3,387.58	0.000***
Within groups	7,369,967,859.81	38,765	190,119.12
Total	8,658,054,313.58	38,767

Sig., significance value.

***Significant at p ≤ 0.001.

Table 3 . Tukey’s HSD post hoc test results.

Class		Mean difference	Std. error	Sig.	95% CI
					Lower bound	Upper bound
Manchurian	CJK	361.35	5.97	0.000***	347.37	375.34
	Endemic	–13.16	6.06	0.076	–27.36	1.04
CJK	Manchurian	–361.35	5.97	0.000***	–375.34	–347.37
	Endemic	–374.51	4.98	0.000***	–386.17	–362.84
Endemic	CJK	13.16	6.06	0.076	–1.04	27.36
	Manchurian	374.51	4.98	0.000***	362.84	386.17

Std. error, standard error; Sig., significance value; CI, confidence interval; CJK, China–Japan–Korea.

***Significant at p ≤ 0.001.

The normalization of the distribution points showed that the rate of distribution was high at elevations of 0‒300 m for CJK species, decreasing towards 800‒2,750 m. The highest distribution frequency for endemic and Manchurian species was observed at elevations ranging from 800 to 2,750 m above sea level (Fig. 6).

Figure 6. Normalized count divided by the distribution area of the populations of China–Japan–Korea, Manchurian, and endemic flora by elevation class.

The analysis of the species detected at more than 200 points, including Manchurian, CJK, and endemic species, led to the identification of 7 Manchurian, 17 CJK, and 16 endemic species (Table 4). In addition, at 200 or more sites in the isolated habitats of the Baekdudaegan and regions at ≥ 800 m elevation, two and three boreal species were detected, respectively (Table 5).

Table 4 . Species that have appeared at more than 200 points.

No.	Manchurian plant	Count	CJK plant	Count	Endemic plant	Count
1	Mukdenia rossii (Oliv.) Koidz.	519	Mallotus japonicus	745	Clematis trichotoma Nakai	942
2	Viola diamantica NAKAI.	461	Neolitsea sericea	648	Asarum maculatum Nakai	655
3	Anemone reflexa Steph. & Willd.	440	Scopolia japonica	607	Anemone koraiensis Nakai	647
4	Neillia uekii Nakai	386	Meliosma myriantha Siebold & Zucc.	550	Abies koreana	573
5	Eranthis stellata Maxim.	367	Ligustrum japonicum Thunb.	543	Cirsium setidens	470
6	Abelia coreana Nakai	344	Rubus corchorifolius L.f.	454	Clematis brachyura	453
7	Acer ukurunduense Trautv. & C.A. Mey.	303	Quercus acuta Thunb.	439	Hanabusaya asiatica Nakai	422
8			Lindera sericea (Siebold & Zucc.) Blume	432	Vicia venosissima	412
9			Pittosporum tobira	417	Megaleranthis saniculifolia	396
10			Ficus erecta	404	Lonicera subsessilis	376
11			Rhus sylvestris Siebold & Zucc.	392	Coreanomecon hylomeconoides	389
12			Ardisia crenata	383	Aconitum pseudolaeve	382
13			Cinnamomum yabunikkei H.Ohba	375	Berberis koreana	354
14			Arisaema ringens	342	Hepatica insularis	285
15			Litsea japonica	343	Scrophularia koraiensis Nakai	317
16			Quercus glauca	328	Salvia chanryoenica Nakai	308
17			Castanopsis sieboldii	328
Total	7	2,820	17	7,730	16	7,381

CJK: China–Japan–Korea.

Table 5 . List of species that appeared at more than 200 points in Baekdudaegan and at elevations above 800 m.

No.	Baekdudaegan	Count	Elevation above 800 m	Count
1	Megaleranthis saniculifolia	396	Acer ukurunduense Trautv. & C.A.Mey.	303
2	Anemone koraiensis	647	Viola diamantiaca Nakai	461
3			Anemone reflexa Steph. & Willd.	440
Total	2	1,043	3	1,204

Biome types

Biome analysis based on the plant species occurring in the Baekdudaegan and Manchurian, CJK, and endemic species showed that the species in the Baekdudaegan region and Manchurian species overlapped in the regions from the boreal forest biome to the temperate seasonal forest biome, with a mean temperature of ~5°C‒15°C. The overlap of Baekdudaegan species might be attributed to their characteristic crossing of the Korean Peninsula in the south to north direction; however, Manchurian species were mainly distributed in the boreal forest biome, with the overlap observed in certain regions of the temperate seasonal forest biome. In turn, endemic species were observed at the center of the temperate seasonal forest biome, with a mean temperature of approximately 3°C‒17°C, whereas CJK species were observed in the temperate seasonal forest biome, with a mean temperature of approximately 10°C‒17°C, and at certain sites in the woodland/shrubland biome (Fig. 7).

Figure 7. Distribution by plant group according to Whittaker’s biome classification method.

Biome analysis of two endemic, two CJK, and three Manchurian species showed that the Manchurian species Larix olgensis and Betula platyphylla were distributed in the boreal forest biome, while the endemic and CJK flora species were distributed in the temperate seasonal forest biome (Fig. 8).

Figure 8. Distribution by representative plant species according to Whittaker’s biome classification method.

Relationship between plant distribution and habitat environment variables

The factor analysis results indicated a consensus across the variables under study, as all seven variables showed commonality (h2) values of ≥ 0.3. The proportions of variance for Manchurian species were estimated at rotated component 1 (RC1) and rotated component 2 (RC2) to be 54% and 35%, respectively, accounting for 89% of the total variance. The proportions of variance for CJK plants were estimated to be 53% and 38% at RC1 and RC2, respectively, accounting for 91% of the total variance (Tables 6, 7).

Table 6 . Explanatory power of each factor.

Explanation	Manchurian plant			China–Japan–Korea plant
	RC1	RC2		RC1	RC2
SS loadings	3.79	2.46		3.72	2.64
Proportion var.	0.54	0.35		0.53	0.38
Cumulative var.	0.54	0.89		0.53	0.91
Proportion explained	0.61	0.39		0.58	0.42
Cumulative proportion	0.61	1.00		0.58	1.00

SS loading and RC indicate the sum of the squared loadings and rotated component, respectively.

Svar., variance.

Table 7 . Factor analysis results.

Variables	Manchurian plant						China–Japan–Korea plant
	RC1	RC2	h2	u2	com		RC1	RC2	h2	u2	com
Lat.	–0.38	0.86	0.89	0.113	1.4		–0.18	0.93	0.9	0.096	1.1
Elev.	0.96	0.18	0.96	0.0394	1.1		0.96	0.17	0.94	0.056	1.1
Temp.	0.96	–0.27	1	0.0037	1.2		0.93	–0.35	0.99	0.012	1.3
Precept.	0.19	0.88	0.81	0.1893	1.1		0.59	0.63	0.75	0.248	2
Warm.	0.99	–0.06	0.98	0.0238	1		0.95	–0.22	0.95	0.047	1.1
Cold.	0.87	–0.47	0.99	0.0124	1.5		0.78	–0.58	0.95	0.049	1.8
Cont.	–0.15	0.78	0.63	0.3711	1.1		–0.19	0.91	0.86	0.136	1.1

Lat., latitude; Elev., elevation; Temp., temperature; Precept., precipitation; Warm., warmth index; Cold., coldness index; Cont., continentality; RC, rotated component; h2, commonality value between variables; u2, unique variance value; com, communality.

The main variables constituting RC1, which influenced the inhabitation of Manchurian species, were the elevation, temperature, warmth index, and coldness index, whereas those constituting RC2 were precipitation, latitude, and continentality. Furthermore, the main variables constituting RC1 that influenced the inhabitation of CJK plants were the elevation, temperature, warmth index, and coldness index, whereas those constituting RC2 were latitude, continentality, and precipitation. Based on these results, it was concluded that the components of RC1 and RC2 that influenced the distribution of Manchurian and CJK species were associated with temperature for RC1 and latitude as a spatial factor for RC2 (Fig. 9).

Figure 9. Biplot showing the factor analysis results (A: Manchurian plants; B: China–Japan–Korea plants). RC, rotated component.

With the rise in the global temperature, the distribution of subtropical plant species has increased in terms of latitude and elevation, thereby extending their habitat areas (Al Balasmeh and Karmaker 2020; Garamvölgyi and Hufnagel 2013). Concomitantly, the distribution of boreal plants has steadily decreased worldwide due to their confinement to habitats in high-latitude and high-elevation regions (Birks and Willis 2008; Stralberg et al. 2020).

Consistent with the results obtained in this study, most plant species inhabiting the Korean Peninsula were distributed in the temperate seasonal forest and boreal forest biomes. This distribution was found to be simultaneously influenced by the difference in latitude due to the stretching of the geographical environment in the south–north direction, the climatic characteristics of a peninsula located on a mid-latitude continent in the northern hemisphere, and the characteristic high elevations in the east and lower elevations towards the west. Based on these results, the distribution trends of Manchurian and CJK plant species on the Korean Peninsula are shown in Figure 10. At the latitude of approximately 37° on the Korean Peninsula, the distribution of Manchurian plants increased northward and the distribution area of CJK plants widened southward. The distribution trend observed for the Manchurian species in South Korea was centered at the refugia formed in high-elevation mountain regions, mainly in the Baekdudaegan. Notably, owing to the differences in the amount of floral distribution data collected for South Korea and North Korea, the trend may be skewed toward South Korea. To more accurately identify a clear trend, floral distribution data for North Korea should be collected continuously using a standardized methodology. Considering all plant groups used for analysis, the distribution of flora was strongly influenced by climatic factors in association with the geographical characteristics of the peninsula.

Figure 10. Schematic diagram showing the trend of Manchurian and China–Japan–Korea flora in the Korean Peninsula.

Manchurian species in the Korean Peninsula were distributed on Mt. Baekdusan and the Kaema Plateau, the major mountain ranges in North Korea, the Baekdudaegan, and the mountains at ≥ 800 m above sea level in South Korea. The detected species were relict plants that descended from the northern part of the Eurasian continent during the last glacial period of the Pleistocene, approximately 20,000 years ago (Kong et al. 2014). The habitats of these species are ecologically stable regions due to their high elevation and minimal human interference (Kim and Lee 2013; Kwon et al. 2002), and regions that have served not only as long-term habitats for the flora and fauna on the Korean Peninsula, but also as areas exhibiting the differentiation of those isolated species in specific regions (Chung et al. 2013). A diagram based on these distribution characteristics for the correlations across elevations and the main flora of the Baekdudaegan is shown in Figure 11. Meanwhile, Manchurian species occurring in the Korean Peninsula during the periglacial period of the late quaternary have continued to inhabit high-elevation mountain regions, such as the Baekdudaegan and Mt. Baekdusan, and the limestone fields, using these regions as geographical refugia (Chang et al. 2017) (Fig. 12).

Figure 11. Schematic diagram showing the representative flora species and elevation profile in the Baekdudaegan.

Figure 12. Distribution points of species that appeared above an elevation of 800 m. Among these species, the species inhabiting Baekdudaegan and limestone areas are marked separately.

Furthermore, certain species have maintained a high level of competitiveness to continue to inhabit these ecosystems by becoming tolerant under unique habitat conditions, such as limestone fields (Bae et al. 2014; Wang et al. 2018). Limestone areas are known to have different ecosystem structures to non-lime areas due to the unique physicochemical soil characteristics. Owing to the specificity of the ecosystem structure, the biodiversity is higher than that of non-lime areas, and the composition ratio of native species and rare plants has been evaluated as high (Kim et al. 2021). Nevertheless, the death and reduced habitat range of northern lineage species inhabiting the Korean Peninsula have been consistently reported in line with climate change (Kong et al. 2011; Lee 2009; Lee 2011). Previous reports on the death of such plants have mainly focused on the Baekdudaegan and mountain refugia regions, such as Mt. Hallasan in South Korea (Cho et al. 2004; Chung et al. 2018; Kim and Lee 2013; Kim and Yun 2013; Kim et al. 2011; Kong 1998). Species favoring such unique habitats as limestone fields have also decreased (Bae et al. 2014; Nam et al. 2012). Investigations into these species have attributed their decline and reduced habitats to various causes, but the issue remains controversial.

Various causes may underlie the decline and reduced populations of plants, including climatic factors, deforestation, disease, soil, hydrography, hydrological factors, and succession. Climate change plays an indirect role in the death of plants. While extreme weather events related to temperature and precipitation may have a direct effect on plant survival, gradual changes, such as reduced snowfall in winter, emergence of diseases or pests, marked changes in soil properties, and changes in soil moisture, exert a greater influence (Kim 2012; Lee and You 2001). For example, Lee et al. (2016) reported that the death rate of Larix olgensis on Mt. Baekdusan has increased with a 2.6°C increase in ambient temperature over the past 21 years due to the repeated hatching of bark beetle larvae that feed on the sap inside the bark. In addition, dendrochronological studies (Koo et al. 2001; Seo et al. 2019) have reported a disturbance in the water balance due to a decline in snow accumulation in the winter causing the death of Abies koreana in South Korea (Koo and Kim 2020). Similarly, Lim et al. (2018) reported that, with an increase in temperature, the habitat range of A. koreana on Mt. Hallasan may decrease gradually as the species loses competitiveness against temperate tree species, such as Quercus mongolica and Pinus densiflora. The Korea National Institute of Biological Resources (2009) reported that the distribution area of warm temperate evergreen broadleaved trees has moved north by up to 70 km over 60 years (1941–2000). However, there is a lack of research on the mechanism causing the change in distribution in southern lineage plants on the Korean Peninsula, and research should be conducted on this in the future. Most studies on southern lineage plants related to climate change on the Korean Peninsula predicted future distribution areas and generally reported that southern lineage plants will gradually move north due to climate change (Park et al. 2010; Yun et al. 2014; Koo et al. 2017).

A database was constructed for spatial data regarding the habitats of boreal and subtropical plant species distributed across the Korean Peninsula. Using this database, the distribution of these species and their localization in different biomes were determined to characterize the distribution of flora on the Korean Peninsula.

As the threat of biodiversity loss due to climate change to human life has been acknowledged worldwide, there is a general agreement on the need to develop and implement countermeasures to neutralize such threats. Notably, in South Korea, where excessive land development has been boosted by economic growth over the past several decades, firmer and more determined responses are required. While this situation has led to various ongoing studies, the development of more practical strategies in response to the challenge of climate change demands the analysis of the current status across the entire Korean Peninsula considering ecological connectivity. In this regard, studies focusing solely on South Korea are limited. The findings reported herein will prove valuable in developing mitigation strategies against climate change effects regarding habitat conservation and alternative habitat selection, as the study reports on the floral distribution trend across the entire Korean Peninsula. Furthermore, the flora database constructed in this study will provide essential basic data for various follow-up studies regarding the influence of future climate change on the biodiversity of the Korean Peninsula.

Supplementary information accompanies this paper at https://doi.org/10.5141/jee.22.054.

Table S1. China–Japan–Korea flora used in this study.

Table S2. Manchurian flora used in this study.

Table S3. Endemic flora used in this study.

Table S4. Baekdudaegan flora used in this study.

Table S5. Limestone flora used in this study.

Not applicable.

CJK : China–Japan–Korea

Lat : Latitude

Elev: Elevation

Temp: Temperature

Precept: Precipitation

Warm: Warmth index

Cold: Coldness index

Cont: Continentality

NSK carried out conceptualization, performed analysis and wrote the manuscript. CHL constructed the database, performed visualization and reviewed the manuscript. YCC, SHJ, JYC, SZJ, and YN collected base location data of species and verified results. All authors read and approved the final manuscript.

This work was supported by a grant from the National Institute of Ecology (NIE), funded by the Ministry of Environment (MOE) of the Republic of Korea (NIE-B-2022-35).

The datasets used and analyzed during the current study are available from the corresponding author on reasonable requests.

Not applicable.

Not applicable

The authors declare that they have no competing interests.