INTRODUCTION
Rapid environmental changes due to urbanization and climate change in recent are expected to have a serious impact on biodiversity, such changes are thought to caused by an increase in human activities (Czech et al., 2000). In particular, changes in land use due to urbanization, agriculture, and forestry are known to have a direct influence on the loss of biodiversity (Myers and Knoll 2001, Novacek and Cleland 2001). For this reason, the importance of nature reserves has been steadily increased. In addition, identification of key factors determining the distribution of species in habitats is necessary for biodiversity conservation. Although several attempts have been conducted in order to identify the relationship betw een insects distribution and environment in Korea (Park and An, 2000; Kwon and Park, 2005; Kang et al., 2009; Park, 2010; Do et al., 2012; Jung et al., 2011a, 2012), many studies conducted in Korea have been focused on biodiversity study (i.e., fauna=species list) through surveys on a specific area.
Performing a monitoring of whole biota is the best way to investigate biodiversity in a certain area (Weibull et al., 2003), but this is generally impossible due to limitations in human resources for monitoring and identification. For this reason, bioindicators should be applied for monitoring (Lindenmayer et al., 2006), because information on a monitoring program for the biodiversity management can be obtained if the bioindicators are monitored (Ferris and Humphrey, 1999). In this study, ground beetles was selected as bioindicators, because their taxonomic and biological characteristics are generally well known, and most of them are carnivores belonging to a high trophic level among arthropods (Rainio and Niemelä, 2003). In addition, because ground beetles have a specific habitat preference, they are readily respond to environmental changes (Thiele, 1977; Lövei and Sunderland, 1996; Rainio and Niemelä, 2003). Therefore, many studies have been carried out using ground beetles as a bioindicators to monitor environmental changes.
There were few studies regarding insects conducted in Naejangsan National Park as follows: a study on the entomofauna of Naejangsan Mountain (Kim et al., 1993); a report of resource monitoring in Naejangsan National Park published in 2011 (NNPO, 2011); a study on species distribution and the diversity of beetles (Lee, 2011). Although 10 and 17 ground beetle species were reported by Kim et al. (1993) and NNPO (2011) respectively, they were mainly reported lepidopteran insects. In case of Lee (2011), 32 coleopteran species belonging to 13 families using various sampling methods (hand collecting, pitfall trap, beating, sweeping). However, regarding the ground beetles distributed in Naejangsan Mountain, more study is necessary, because only six ground beetle species were reported by Lee (2011).
Therefore, this study was conducted to investigate biodiversity of ground beetles that inhabit Naejangsan National Park and identify the their distribution characteristics. This results can be useful for the establishment of long-term strategy on both habitat and biodiversity management.
MATERIALS AND METHODS
1.Study Site
Naejangsan National Park has been recognized for its importance as a nature reserve and was designated as a IUCN Category II protected area in 2010. According to the Dong'guk yeoji seungnam: an Augmented Geography Survey of the Eastern Nation (Korea), Naejangsan Mountain is one of the famous five mountains in Honam along with Jirisan Mountain, Wolchulsan Mountain, Cheongwansan Mountain and Neunggasan Mountain (Korea National Park Service, http://knps.or.kr/). Naejangsan National Park, which was designated as the eighth national park in 1971, is located in Naejang-dong, Jeongeup-si, Jeollanam-do and Bonkheung- myeon, Sunchang-gun, Jeollabuk-do, and covers an area of 80,708 km2 (Korea National Park Service, http://knps.or.kr/). There is Naejangsan (763 m) to the east, Ipamsan Mountain (626 m) to the west and Baekamsan Mountain (741 m) to the north of Naejangsan National Park. Although the height of these mountains are not high about 700 m, their slopes are very steep and ravined (NNPO, 2011). The dominant plant species in Naejangsan National Park are Pinus densiflora Sieb. et Zucc., Quercus variabilis Blume, Carpinus laxiflora Blume, Torreya nucifera Siebold & Zucc., Acer palmatum Thunb., Quercus serrata Thunb., Daphniphyllum macropodum Miq., Quercus mongolica Fisch. ex Turcz., Cornus controversa Hemsl. and Salix koreensis Andersson. In particular, Torreya nucifera Siebold & Zucc. in Baegyangsa Temple and Daphniphyllum macropodum Miq. in Seoraebong are geographically acknowledged as the northern limit line of plant distribution and are designated as natural monuments (Lee, 2011).
To collect ground beetles, 12 sites from 2008 to 2010 and 7 sites in 2011 were surveyed, and the management number of the grid 2×2 km, that assigned by the Korea National Park Research Institute, was used for each study site (Table 1). The major vegetation types at the survey sites were classified into three subgroups, such as coniferousdominated forests (5 sites), broadleaf deciduous forests (14 sites), and bamboo forest (1 site). In the coniferousdominated forests, P. densiflora, Pinus koraiensis Sieb. et Zucc. and Thuja orientalis L. were dominant and Q. mongolica, Q. variabilis, Quercus aliena Blume and A. palmatum were dominant in the broadleaf deciduous forests.
Althougt, this study was conducted on the forest environment in Naejangsan National Park, the surrounding habitat of study sites located at forest edge habitats were different, such as grassland, farmland, and road. As for information on the land use of study sites, land-use within a 1-kilometer radius of study sites were confirmed using the land cover map (scale of 1:2,500) provided by the National Geographic Information Institute. While forest coverage rates in most areas in the National Park were considerably high (more than 90 %), that of study sites adjacent to built-up area or boundary area of the National Park were 60~83 %. Such environmental information was used to understand the distribution characteristics of ground beetles in Naejangsan National Park.Fig .1
2.Collecting Method and Identification
Three pitfall traps were installed in each study site to collect ground beetles. The trap (10.5 cm in diameter, 8 cm in height) was plastic containers with six perforated holes (2.5 cm in diameter) at mouthpart of trap to prevent trapping non-target animals (rodent, amphibian, and reptile), and a plastic roof was placed 3 cm above each trap to prevent the inflow of rainfall and litter. Pitfall traps were un-baited, containing preservatives (300 ml, 95 % Ethyl-Alcohol:95 % Ethylene-Glycol=1:1) as killing- preserving solution, which replaced every month (3~4times a year). Collected ground beetles were brought to the laboratory and dried, mounted, and identified to the species level under a dessecting microscope (63×, Olympus SZ61).
Identification was performed according to Habu (1967, 1973, 1978, 1987), Kwon and Lee (1984) and Park and Paik (2001), and nomenclature confirms to list of Korean Carabidae by Park and Paik (2001) and Park (2004). The identified ground beetles were stored in the Insect Ecology Laboratory at Seoul National University.
3.Data analysis
The abundance and species richness of ground beetles were calculated in each study site. And non-parametric estimation methods, rarefaction curves (Gotelli and Colwell, 2001) and Chao I (Chao, 1984), were used to estimate the number of species in Naejangsan National Park. Also, for species composition analysis, data of ground beetles were pooled in each study site. Because the study period was different by study sites (92~310 days), the number of individuals of ground beetles at each site was transformed by trap-days (i.e., divided by the total study period per trap) for standardization. After that, the Bray-Curtis similarity among study sites was calculated and a cluster analysis was carried out (Clarke and Warwick, 2001). Species Diversity and Richness v3.0, the biodiversity analysis program was used for the rarefaction curves and Chao I (Henderson and Seaby 2002), and PRIMER v6.0 was used for the Bray-Curtis similarity and the cluster analysis (Clacke and Gorley, 2006).
RESULTS AND DISCUSSION
A total of 2,409 individuals belonging to 35 species were collected during 2008 and 2011 (Table 2). Estimated species richness of ground beetles in Naejangsan National Park was also approximately 35 species derived from rarefaction curves and Chao I (Figure 2). However, because the rarefaction curves did not asymptotic and there were large variations in the result of Chao I, which was reflected in rare species such as singleton, there is the possibility that more species will be collected in the further monitoring.
In species richness, 15 species were collected in site 25.2, followed by site 25.1 (13 species) and site 15.2 (12 species) (Table 2). In abundance, 368 individuals were caught in site 25.1, followed by site 16 (246 individuals), site 6 (218 individuals) and site 28 (217 individuals).
Because all pitfall traps were installed within forests, the distribution of medium- and large-bodied species (Aulonocarabus spp., Coptolabrus spp., Eucarabus spp., and Pterostichus spp.) affected the species richness of ground beetles in each study site. On the other hand, the distribution of open-habitat species may differed according to the characteristics of the surrounding environment. For example, in case of the study sites within the well- protected area, medium- and large-bodied species including Coptolabrus jankowskii jankowskii Oberthur, Eucarabus sternbergi sternbergi Roeschke and Pterosticus audax Tschitschérine were dominant. On the other hand, Pheropsophus jessoensis Morawitz, Synuchus nitidus (Motschulsky), Synuchus cycloderus (Bates) or Chlaenius naeviger Morawitz were dominant at the boundary area of the National Park.
The result of cluster analysis also showed that the distribution of ground beetles was affected by the surrounding habitats in accordance with the characteristic of forests (Figure 3). In particular, the abundance and species richness of medium- and large-bodied species groups were high in well-preserved sites as broad-leaved deciduous forests (site 8.1, 9, 14, 15.1, 18, 19, 20, 25.1, 25.2), showing a clear difference from other study sites. But species composition of some broad-leaved deciduous forests sites, which were adjacent to non-forest environment with a rocky ground surface, Such results were thought to be relevant to the difference in distribution of dominant species by study site. In general, S. cycloderus and S. nitidus are dominant in Korean forests (Yeon et al., 2005), but the results of this study showed some differences according to environmental characteristics of study sites. This is thought to be due to various factors such as competition among species, changes in the surrounding environment, and habitat stability. And this results similar with some of previous studies carried out in Bangtaesan Mountain (Jung et al., 2011a) and Gariwangsan Mountain (Jung et al., 2011b) in Gangwon-do, the places that have well-preserved forest habitats. In particular, changes in the surrounding environment may play a critical role for species distribution. In fact, if the surrounding environment changes due to newly constructed roads, agricultural activity or urbanization, microclimate factors (e.g., temperature, humidity, wind, etc.) within forests may also change (see edge effect described by Laurance, 2008). These changes in the forest environment can also affect the characteristics of microhabitats and lead to a decrease in abundance of species that prefer stable habitats. In addition, species composition may change greatly when open-habitat species habitats penetrate into forests.
Compared to previous studies that reported 27 ground beetle species in Naejangsan National Park (Kim et al., 1993; Lee, 2011; NNPO, 2011), 25 species (including 3 undetermined species) were newly listed except for 1 species (Pterostichus mucronatus), which species may be misidentified. Overall, ground beetle fauna in Naejangsan National Park is summarized as 51 species belonging to 28 genera of 11 subfamilies (Appendix-1). In ground beetles, the species richness may vary greatly according to the number of species belonging to Harpalinae or Callistinae, which species are generally known to openhabitat species. However, in this study, because pitfall traps were installed within forest environments, their capture was not much influence on abundance and species richness of whole ground beetles, while species belonging to Carabinae or Pterostichinae, which include many forest species, did have a substantial influence on the abundance and species richness in study sites. The species richness of ground beetles in NNPO (2011) and Kim et al. (1993) was lower than that of this study, because they mainly used light traps to collect flying insects. However, pitfall trap is the most commonly used monitoring ground-dwelling arthropods (spiders, rove beetles, and ants) including ground beetles. Therefore, there are some limitations in sampling ground beetles with light traps. On the other hand, only 6 ground beetle species were listed by Lee (2011), although pitfall traps were used in that study. In this case, short installation period in pitfall traps (i.e., 3 times for 3 days) may be resulted in lower diversity. In general, in case of monitoring ground beetles using pitfall traps, a period of at least four months a year is suggested as the reasonable survey period in order to secure species diversity (Woodcock, 2005). This is because the seasonal occurrence is vary according to species. In addition, if long-term monitoring is impossible, it was suggested that at least 20 days a year are required considering the season to collect more than 50% of total species diversity (Niemelä et al., 1990).
The result of this study is limited to ground beetles, however, it will be useful to establish strategy for the habitat and biodiversity management. Species composition and diversity in core habitat in National Park may greatly differed from that of its boundary habitats. In particular, among study sites, Naejangsa Temple ~ Geumseon Valley area, Namchang Valley ~ Monggye Waterfall area, and Baekyangsa Temple area are thought to be the most important areas of biodiversity conservation in Naejangsan National Park. On the other hand, forest habitats located at the boundary of the National Park with thinned litter layer may have a less potential capability to enhance biodiversity, although these areas can be used as buffer zone to protect core habitats or valuable habitat for some threatened and endangered species (Brockerhoff et al., 2008). However, more studies are required how various arthropods including ground beetles are affected by environmental characteristics such as vegetation and litter layer in terms of spatial distribution.
In conclusion, because the existence of natural broadleaved deciduous forests within a forest landscape is very important for the biodiversity conservation in general (Fuller et al., 2008), the development and disturbance in these natural forests should be minimized. In addition, the results of this study can be used as basic data for the management of forests and their surrounding habitats to improve biodiversity in national parks, because pitfall trap can be used as useful monitoring tools to study the spatiotemporal distribution of ground beetles (i.e., the relationship between ground beetles and environmental variables) as well as other ground-dwelling arthropods (Woodcock, 2005). In addition, long-term monitoring is necessary to predict the response of organisms under environmental changes.
