INTRODUCTION
Baekdudaegan divides Korea into east and west and it is recognized by many people in Korea as an iconic mountains. This unique topography divides our traditional lifestyles and geographic perspectives. Baekdudaegan starts from Byeongsabong (2,744m) of Mt. Baekdu to Cheonwangbong (1,915m) of Mt. Jiri without crossing any valleys or rivers. Its length is about 1,400km and altitude of this region is about 100 to 2,744m (Cho, 2002).
Korea stretches from south to north, and cold current and warm current flow around Korea. During the winter, the cold-wind blows from northwest and the warm-wind blows from south in the spring. Therefore, it shows different and diverse floras in each regions of Korea. There are various floras such as temperate plants, subtropical plants, and subpolar plants because of the sea on three sides. Some northern plants move to south and some southern plants move to north because of subpolar climate, temperate climate, and warm temperate climate in Korea. Thus, there are many Korea endemic, endangered and rare plants, and animals throughout Mt Baekdu, Mt. Seolak, Mt. Odae, Mt. Taebaek, Mt. Sobaek, Mt. Jiri etc. in Baekdudaegan.
As people recognize the importance of Baekdudaegan, a lot of studies about Baekdudaegan, which includes survey and concept of Baekdudaegan (Korea Forest Service and Korean Geographical Society, 1997), forest status of the Baekdudaegan (Forestry Administration and Green Korea United, 1999), settings of efficient management range of Baekdudaegan (Korea research institute for human settlements, 2000), natural ecosystem conservation and damaged land restore plan of Baekdudaegan (Korea Forest service, 2001), natural ecosystems survey and management plan of Baekdudaegan (Korea Forest service, 2002) etc. have been conducted. Furthermore, many studies on the vegetation characteristics in Baekdudaegan have been carried out. Yun et al.(2010) studied about the vegetation distribution and community characteristics on the Sobaeksan National Park. Park et al.(2009) reported on the vegetation types and floristic composition of native conifer forest in the ridge of the Baekdudaegan. Lee et al.(2014) investigated on the community structure of Pinus desiflora and Quercus mongolica forest in Jochimryeong to Shinbaeryeong of the Baekdudaega. Despite these much research, study on the vegetation properties from Guryongryeong to Mt. Yaksu, which is adjacent to Guryongryeong ecological tunnel, have not been carried out. Therefore the purpose of this study was to find out the vegetation structure, importance value, DBH distribution, and species diversity of the mountain ridge from Guryongryeong to Mt. Yaksu and to provide a management plan for the future.
MATERIALS AND METHODS
1.Setting of survey area
A preliminary vegetation survey was conducted on June 23 in 2011. Formal surveys were conducted from June 3 to August 5 between Guryongryeong (1,013m) and Mt. Yaksu (1,306m) of Baekdudaegan. A total of 22 plots were surveyed in this area (Figure 1).
2.Investigation of the vegetation and environmental factor
The survey area was from Guryongryeong to Mt. Yaksu. A total of 22 plots (10 × 10m quadrat) were installed with a random sampling method and major environmental factors, soil characteristics, and vegetation for each quadrat were surveyed. Vegetation survey was conducted according to overstory layer, midstory layer, and understory layer divided by position of canopy. In the overstory layer and midstory layer, kinds of tree, population, and diameter at breast height (DBH) were measured. Kinds of tree and cover degree in the understory layer were investigated. To know the relationship between growth rates of tree and environmental factors, altitude, aspect, slope, litter layer (soil depth), and height of overstory layer were examined.
According to the meteorological data of 20 years of Inje weather station, which is adjacent to this research area, the average annual temperature and annual precipitation were 10.1°C and 1,210.7mm, respectively. Most of the precipitation was concentrated from Jun to September. Highest average temperature and lowest average temperatures were 16.4°C and 4.7°C, respectively.
3.Cluster analysis and correlation between species
With population according to species collected from each plots, we tried to classify the survey plots using entire species collected from overstory layer, midstory layer, and understory layer by the method of Ludwig and Reynolds (1988). Percent Dissimilarity (P.D) was applied to calculate the distance among the surveyed plots. To investigate correlations among interspecific or environmental factors collected from 22 plots, SPSS 17.0 program was used.
4.Analysis of forest community
Importance Percentage (I.P.), which was calculated with following equation as (relative density + relative cover degree + relative frequency)/3, was calculated using vegetation data surveyed at mountain ridge of from Guryongryeong to Mt. Yaksu. Mean Importance Percentage (M.I.P.) was calculated with an equation considering the size of the population as (overstory layer I.P. × 3 + midstory layer I.P. × 2 + understory layer I.P.)/6 (Curtis and Mclantosh, 1951). Species diversity, which shows a measure of the diversity of species composition, was comprehensively compared by species diversity (H’), evenness (J’), and dominance (D) calculated by Shannon’s formula (Pielou, 1975).
RESULTS AND DISCUSSION
1.Forest environment and characteristic of Species composition
Table 1 shows the major environmental factors and the numbers of species. The survey plots were installed by considering current vegetation at natural forests from Guryongryeong to Mt. Yaksu, which is a part of Baekdudaegan. There are located between altitudes 1,106 m to 1,275 m. The slop and litter layer were about 15° to 45° and 3 to 5 cm, respectively. The height of the tree was between 9 to 15.6 m in the overstory layer, 3.5 to 7.8 m in the midstory layer, and 0.6 to 2.2 m in the understory. Depending on the story, the DBH was between 15.5 to 40 cm in the overstory layer and 4.7 to 12.4 cm in the midstory layer. The average DBH in the overstory layer and midstory layer were 28.1cm and 7.5cm, respectively. Species numbers per each plot (100m2) of woody plants to be composed of overstory layer, midstory layer, and understory layer were from 5 to 14. This result indicates that there exists a big difference in the numbers of species among the investigated plots. It is likely that the difference results from different seedling occurrence because the surveyed sites are located in mountain ridge and the height of the tree of overstory layer is very high. Current study shows similar results with several previous studies, which were conducted in the same area and showed 2 to 10 species in Mt. Cheongok (Choi, 2002), 4 to 12 species between from Gitdaebong to Mt. Cheongok (Choo et al., 2002), 2 to 12 species between from Mt. Daedeok to Guemdaebong (Kim et al., 2003), 6 to 14 species in subalpine areas of Mt. Deogyu (Kim & Choo, 2004), and 4 to 15 species in Dangol valley of Mt. Taebaek located in Baekdudaegan (Cho et al., 2005). However, it shows slightly low than 11 to 26 species in nature conservation area in Mt. Gyeryong national park, 13 to 20 species between from Donghak temple and Nammaetap of Mt. Gyeryong, and 8 to 20 species between Suryeong and Sosagogae located in Baekdudaegan (Choo & Kim, 2004).
2.Structure of forest community
1)Cluster analysis
Figure 2 shows the result of the cluster analysis based on the data of 22 plots collected between Guryongryeong and Mt. Yaksu. The phylogenetic tree did not show much difference among the surveyed plots because the survey areas are relatively narrow and the geographical characteristics did not show much difference. However, they were classified into three groups with dominant species such as Quercus mongolica community, mixed forest community of subalpine zone species, and another mixed forest community by the slope and direction of the surveyed areas. Carpinus cordata, Cornus controversa, Acer pseudosieboldianum, and Tilia amurensis were relatively major species in this study area. Group I, which includes 13 plots, was Q. mongolica-C. cordata-A. pseudosieboldianum-T. amurensis community. Group II, which has big and old tree of Q. mongolica including 7 plots, was typical subalpine ridge community. This group contains Q. mongolica as a major species and T. amurensis, Rhododendron schlippenbachii etc. as minor species. Group III, which contains 2 plots, was C. controversa-Q. mongolica community with A. pseudosieboldianum, Betula costata, R. schlippenbachii etc. as minor species. These results indicate that the vegetation structure of the subalpine zone between Guryongryeong and Mt. Yaksu is Q. mongolica-C. controversa-C. cordata community. Between Guryongryeong and Mt. Yaksu located in Baekdudaegan, the dominant species was Q. mongolica. This result was similar with some results such as Dosolbong in Mt. Sobaek (Kim et al., 1993), Balbatjae-Birobong in Mt. Sobaek (Park et al., 1993), Birobong-Horyeongbong in Mt. Odae (Kim et al., 1996a), Daecheongbong-Socheongbong in Mt. Seolak (Kim et al., 1997), Daecheongbong-Hangyeryeong (Kim & Baek, 1998a), Pijae-Doraegijae in Mt. Taebaek (Oh & Park, 2002), Gitdaebong-Mt. Cheongok(Choo et al., 2002), Nogodan-Goribong (Kim & Choo, 2003). However, unlike previous results, this survey areas showed that Quercus mongolica grows as a dominant species with C. cordata and Cornus controversa..
2)Analysis of Importance Percentage
Based on the cluster analysis, Importance Percentage (I.P.) and Mean Importance Percentage (M.I.P.) on the major species in three groups were calculated. Table 2 shows I.P. and M.I.P. value calculated based on the size of the tree. The highest M.I.P. in Group I was Q. mongolica as 18.79% followed by C. cordata, A. pseudosieboldianum, and T. amurensis. In group II, the highest M.I.P. was Q. mongolica as 42.02% followed by T. amurensis, and R. schlippenbachii, and Symplocos chinensis for. pilosawere
In the last Group III, unlike two groups, which was dominant by one species, two species as C. controversa and Q. mongolica were dominant. M.I.P. value of C. controversa and Q. mongolica was 27.83% and 24.43%, respectively. Minor dominant species in the group III were A. pseudosieboldianum, B. costata, and R. schlippenbachii. C. controversa and Q. mongolica in the group III might compete until they become dominant species. However, it is likely that Q. mongolica might eventually be dominant species in this community.
Depending on the story, the highest I.P. of overstory layer in the GroupⅠ was Q. mongolica as 36.05% followed by T. amurensis, C. cordata, B. costata, and T. mandshurica. In the midstory layer in groupⅠ, I.P. of A. pseudosieboldianum is the highest as 31.98% followed by C. cordata, Magnolia sieboldii, and T. amurensis. The highest I.P. of understory layer in groupⅠ was R. schlippenbachii as 40.61% followed by Sasa borealis, Pinus koraiensis, and M. sieboldii. Therefore, in the group I Q. mongolica was relatively dominant in overstory layer than those of other species. A. pseudosieboldianum and C. cordata in the midstory layer might compete until to be the dominant species in the future. In understory, R. schlippenbachii might be maintained as a dominant species. Therefore, it seems that it is not easy to expand other species such as P. koraiensis, M. sieboldii, Vaccinium hirtum var. koreanum. etc. in this story.
The highest I.P. in the overstory layer in the group II was Q. mongolica (66.85%) followed by T. amurensis, P. koraiensis, Tilia manshurica etc.. The I.P. of Q. mongolica was also the highest as 25.81% in the midstory layer in group II followed by T. amurensis, R. schlippenbachii, A. pseudosieboldianum, S. chinensis for. pilosa. etc.. However, in the understory, the I.P. of R. schlippenbachii was the highest as 51.0% followed by S. chinensis for., V. hirtum var. koreanum., Rhododendron mucronulatum etc.. Therefore, group II was concluded that Q. mongolica is the most dominant species in the overstory layer and midstory layer. However, in the midstory layer, R. schlippenbachii might be maintained as a dominant species for long time, if they are not artificial disturbance. In the group III, the I.P. of Q. mongolica was the highest as 37.50% in the overstory layer. The next highest I.P in the second group was C. controversa followed by B. costata, Acer pictum subsp. mono etc. In the midstory layer of the group III, the I.P. of C. controversa was the highest as 37.82% followed by A. pseudosieboldianum, Q. mongolica, Ilex macropoda, and R. schlippenbachii showed the highest I.P. as 61.32% in the understory. The next highest species was A. pseudosieboldianum followed by Sambucus williamsii var. coreana., R. mucronulatum.
In summary of the above results, Q. mongolica was the most dominant species in the overstory layer of group III. However, in the midstory layer, it seems that both A. pseudosieboldianum and C. controversa might compete until they become dominant species. In the understory, R. schlippenbachii might be maintained as a dominant species for long time with weak competition along with A. pseudosieboldianum, S. williamsii var. coreana, and R. mucronulatum.
3)Interspecific correlation
Table 3 shows the result of interspecific correlation calculated by consideration of the frequency distribution using the data collected from 22 plots. It showed relatively high positive correlations between Q. mongolica and S. chinensis for. pilosaR. schlippenbachii; T. amurensis and T. mandshurica, S. chinensis for. pilosa; T. mandshurica and S. chinensis for. pilosa, R. schlippenbachii; B. costata and A. pictum supsp. mono; S. chinensis for. pilosa and R. schlippenbachii. Positive correlations were observed between Q. mongolica and T. amurensis, between A. pseudosieboldianum and C. cordata, between T. amurensis and R. schlippenbachii, and between M. sieboldii and Taxus cuspidata etc. Relatively high negative correlation showed between A. pseudosieboldianum and S. chinensis for. pilosa, R. schlippenbachii and so on. Negative correlations was observed between Q. mongolica and A. pictum subsp. mono; A. pseudosieboldianum and T. mandshurica; T. amurensis and A. pictum subsp. mono etc..
4)DBH distribution
Table 4 shows the DBH distribution of major woody plants for each plant communities classified by the cluster analysis. The forest succession might be estimated by DBH distribution analysis, which is an indirect expression way such as stand dynamics and age of tree (Harcombe and Mark, 1978).
In Group I, A. pseudosieboldianum was much such as seedling or small diameter tree, but C. cordata was relatively distributed less. Therefore, the I.P. of A. pseudosieboldianum might be increased. Because seedling or small diameter tree of B. costata, T. cuspidata, and C. controversa etc. did not exist, the I.P. of B. costata, T. cuspidata, and C. controversa might be decreased. However the I.P. of M. sieboldii might be eventually increased.
In Group II, Q. mongolica showed relatively uniform distribution such as seedling, small diameter tree, middle diameter tree, large diameter tree. Therefore, I.P of Q. mongolica and T. amurensis might be increased for long time, if there are not any artificial disturbance whereas, the I.P. of C. cordata, Fraxinus rhynchophylla, P. koraiensis, C. controversa might be decreased for a while without any artificial disturbance.
In GroupIII, Q. mongolica appeared a lot such as seedling and small diameter tree whereas, C. controversa and B. costata was hardly distributed. Therefore the I.P. of Q. mongolica in this forest might be continually increased, but the I.P. of C. controversa and B. costata might be decreased in the future. These results indicate that these survey areas are typical subalpine vegetation of Korea.
5)Species Diversity
Table 5 shows the species diversity indices of three plant communities. A total of 29 species, which are the highest numbers of species among three communities, were found in the group I. Group II and group III were 18 and 11 species, respectively.
Gene diversity (H') in group I, group II, and group III were 1.1446, 0.9197, and 0.8170, respectively. Maximum species diversity (H' max), which was calculated by common logarithm, was 1.4472 in group I, 1.2553 in group II, and 1.0414 in group III. Evenness (J′), which was calculated by following an equation (Gene diversity (H')/ Maximum species diversity (H' max)), was 0.7909 in group I followed by group III and group II.
The species diversity of this study was from 0.8170 to 1.1446. These values are slightly lower than 1.0316~ 1.1776 in Hyangjeokbong of Mt. Deogyu National Park (Kim & Choo, 2004), 0.9574~1.2845 between form Nogodan to Goribong (Kim & Choo, 2003), 0.9586~ 1.1814 in Mt. Dongdae, Doonobong, and sangwangbong of Mt. Odae National Park (Kim & Choo, 2004), 0.9273~1.2167 in Taech'ongbong and Hangyeryong of Mt. Seorak National Park (Kim & Baek, 1998a), 1.0572~ 1.0931 in Myeongseongbong and Deokpyengbong of Mt. Jiri national park (Kim et al., 2000), 1.2973~1.4633 in Sangwonsa, Birobong, and Horyeongbong in Mt. Odae national park (Kim et al., 1996b), and 0.9580~1.2845 between from Nogodan to Goribong; (Kim & Choo, 2003), whereas it showed similar result with several studies such as 0.7506~1.1512 between Suryeong and Sosagogae (Choo & Kim, 2004) and 0.991 in Jangunbong of Mt. Taebaek (Kim & Baek, 1998b).
When dominance value is over 0.9, it is called one species dominant. When dominance value is between 0.3 ~0.7, two or three species are dominant. Dominance value below 0.3 indicates that several species are dominant (Whittaker, 1965). In this study the dominance value was between 0.2091~0.2673, showing regions between Gyryongryeong and Mt. Yaksu are dominated by several species.