27(1)-04 KE2012-87 임헌명.pdf1.12MB

• INTRODUCTION
• MATERIALS AND METHODS
• 1. Survey areas
• 2. Survey methods
• RESULTS AND DISCUSSION
• 1. Species composition
• 2. Community analysis according to the survey areas
• 3. Similarity analysis

INTRODUCTION

Streamside areas serve to purify contaminants in streams while also serving as a form of shelter and habitat for various living things. They also stabilize the banks, have a recreation function, and provide a visual greenery resource(Ahn and Song, 2003). However, continuous river improvement works change streams, banks and streamside areas until eventually they do not perform their intended functions properly(Son, 1998). In particular, urban streams running through densely populated areas can sustain damage to the habitats of living things when they undergo river straightening projects or when bicycle paths, riverbed roads, parking lots, or athletic facilities which cover the rivers are constructed so as to utilize urban space at riversides. With the recent introduction of the concept of close-to-nature river improvements, many river improvement projects are being planned or are in progress. However, due to the insufficient information pertaining to stream ecosystems, stream landscape architecture or stream landscapes tend to be over-emphasized in favor of the preservation of the stream ecosystem(Namgung, 1999; Shoichiro et al., 2004). Much time and effort are required to restore a close-to-nature stream if the ecosystem is changed because of river improvement projects. Thus, more objective evaluations and expert opinions are required. In addition, river improvement projects should be performed with caution and care(Berit and Matthias, 2008).  

As the importance of the environmental concept of streams has been emphasized, interest in close-to-nature streams is increasing, and studies focusing on birds, fish, and benthic macro-invertebrate related to stream decontamination efforts are actively being performed as part of the overall stream eco-system recovery project(Kim et al., 2002; Park, 2004; Cho, 1994; Cho, 2006). However, studies of terrestrial insects, which represent the greatest percentage in Arthropoda in the animal kingdom, show that they are a direct source of food for birds, amphibians and small mammalians and that they play an important role in ecosystems as a primary consumer. Such studies are, however, somewhat rare, with the exception of a few, such as those by Jung and Yeo (1996), and Jung(1997)(Bae et al., 2002). In a study on insects in relation to city development in Daejeon, 779 species, 149 families and 18 orders of terrestrial insects were identified(Nam and Kim, 1999). Additionally, as the Daejeon stream and Yudeung stream are city streams that penetrates dense urban areas as well as natural eco-streams, which have a direct influence on the natural eco-system at the same time(Lee et al., 1999), the habitats of terrestrial insects and their neighborhood ecosystems can be identified indirectly by comparing the downtown stream and eco-stream sections.  

The Daejeon stream belongs to the Geum River system, the third tributary of the Geum River, and the first tributary stream of the Yudeung stream. It originates at Mt. Manin which is on the boundary of the neighborhood of Hasodong, in the eastern part of the city of Daejeon, and the rural areas of Boksoo township and Chubu township in Geunsan province. It flows to the west and penetrates a very densely populated downtown area. It consists of a Province Grade I Stream(with a stream channel length of 26.29 ㎞, a total stream length of 7.7 ㎞, and a basin area of 89.31 ㎢) at the upper stream of Okgyegyo(bridge), Okgye-dong, Jung-gu, and a Province Grade II Stream (with a stream channel length of 18.59 ㎞, a total stream length of 14.7 ㎞, and a basin area of 49.14 ㎢) at the lower stream(Cho, 2006). Although a natural recreational forest and well-preserved woods are located at the upper stream area, there is some concern that the lower stream will be contaminated by waste water from households and that the forest will be damaged by the growing of rice and other crops. From the midstream to the lower stream areas, a monotonous ecosystem is expected due to heavy contamination by artificial structures and a uniformed natural landscape such as densely built houses, factories, riverbed roads, bicycle roads and grassy fields. The Yudeung stream, which belongs to the Geum River system, is the second tributary of the Geum River and the first tributary of the Gap stream. It originates at Mt. Indae located in Samga-ri, Jinsan township in Geumsan province and at the base of Mt. Wolbong. It flows to the north, merges with a tributary stream to the west at Jinsan township and to the east at Boksoo township, and then merges with the Jibang stream to the east, after which it flows into Daejeon city. The 15.5 ㎞ zone from the neighborhood of Chimsandong, Jung-gu(Central district) to the merging point with the Gap stream is national land. The water quality of the upper area stream of the Yudeung stream is good, and it is used as a recreation area. It is an ecologically good stream where many types of fish can be found. At the lower stream area, there are artificial facilities such as houses, riverbed roads, bicycle roads and sports facilities, similar to the Daejeon stream. The purpose of this study was to identify differences in the community structure of the terrestrial insects living at the streamside of the Daejeon stream and the Yudeung stream and the ecological differences between the natural stream and artificial stream environments. The results of this study can be used as basic materials for long-term monitoring and to identify problems and create solutions during streamside improvement projects.  

MATERIALS AND METHODS

1. Survey areas

The Daejeon stream was divided into 6 zones from Mt. Manin(its origin) to the point where it merges into the Yudeung stream. These zones include two areas that were classified as urban stream areas. The Yudeung stream was divided into ten areas from its origin in Samga-ri, in Jinsan township, Geumsan province to the point at which it merges with the Gap stream. It included three areas that were classified as urban stream areas(Table 1, Figure 1).  

Table 1. Survey areas at the Daejeon and Yudeung streamsides

Figure 1. Map of survey areas

2. Survey methods

For the purpose of this study, quantitative surveys were performed once a month from April to October of 2008. To investigate ground beetles, bait traps were used, while sweeping was used to investigate the insects perched on grass, shrubs or trees as well as those flying. Light traps were not used because they can attract nocturnal insects, the study of which is beyond the scope of the survey. Identification was made of the collections by the Animal Taxonomy and Ecology Laboratory at Daejeon University. Unidentified species were sent to experts in each taxonomy group for identification. An insect list was formulated based on the Checklist of Insects from Korea(1994). Diversity index was calculated using the Shannon-Weaver function (Pielou, 1969), which was influenced by the information theory of Margalef(1958). The similarity Index by Bray and Curtis(1957) was calculated regarding the number of species and the number of individuals at each point, and a weighted average combination method was used to build a dendrogram. To verify the differences between groups, a T-test was performed. Additionally, a Pearson analysis was executed to identify the correlations between the induced factors. For the statistical analysis, SPSS ver. 12K and Primer ver. 6 were used(Clarke and Gorley, 2006).  

Table 2. Species composition by order at the Daejeon and Yedeung streamside areas

RESULTS AND DISCUSSION

1. Species composition

The insects identified at the Daejeon stream and the Yudeung stream belonged to 428 species, 110 families and 11 orders counted in total. At the Daejeon stream, 335 species, 99 families and 11 orders were identified. Coleoptera was the most commonly identified order, with 26 families and 114 species(34.03%), and the next most common orders were as follows: Hemiptera with 60 species and 16 families(17.91%), Hymenoptera with 51 species and 7 families(15.22%), Diptera with 33 species and 16 families (9.85%), Orthoptera with 32 species and 9 families(9.56%), Lepidoptera with 16 species and 8 families(4.78%), Homoptera with 11species and 7 families(3.28%), Odonata with 10 species and 5 families(2.99%), Dermaptera with 4 species and 3 families(1.19%), and Blattaria and Mantodea with 2 species and 1 family(0.6%) each(Table 2). The insects collected by bait traps belonged to 97 species, with 34 families and 6 orders. The most diverse order was Coleoptera, with 60 species and 18 families (61.86%). The order of diversity was Orthoptera with 12 species and 6 families(12.37%), followed by Hymenoptera with 10 species and 1 family(10.31%), Hemiptera with 9 species and 5 families(9.28%), Dermaptera with 4 species and 3 families(4.12%), and Blattaria with 2 species and 1 family(2.06%). The insects collected by sweeping belonged to 281 species, with 85 families and 9 orders. The most diverse order was Coleoptera with 81 species and 20 families(28.83%), and the next most diverse orders were Hemiptera with 56 species and 14 families(19.93%), Hymenoptera with 47 species and 7 families(16.73%), Diptera with 33 species and 16 families(11.74%), Orthoptera with 25 species and 7 families(8.9%), Lepidoptera with 16 species and 8 families(5.69%), Homoptera with 11 species and 7 families(3.91%), Odonata with 10 species and 5 families(3.56%), and Mantodea with 2 species and 1 family(0.71%)(Figure 2).  

Figure 2. Composition of the species collected at the Daejeon streamside area

At the Yudeung stream, 350 species, 98 families and 11 orders were identified. Out of them, Coleoptera was the highest, with 113 species and 25 families(32.29%), and the next most common orders were Hemiptera with 61 species and 17 families (17.43%), Hymenoptera with 47 species and 7 families(13.43%), Diptera with 38 species and 17 families(10.86%), Orthoptera with 33 species and 9 families(9.43%), Lepidoptera with 25 species and 7 families(7.14%), Homoptera with 16 species and 9 families (4.57%), Odonata with 12 species and 4 families(3.43%), and Mantodea with 3 species and 1 family(0.86%). The least common orders were Blattaria and Dermaptera with 1 species and 1 family(0.29%)(Table 2). The insects collected by bait traps belonged to 94 species, 29 families and 6 orders. The most diversely identified order was Coleoptera with 66 species and 18 families(70.21%), followed by Hemiptera with 9 species and 5 families(9.57%), Hymenoptera with 9 species and 1 family(9.57%), Orthoptera with 8 species and 4 families(8.51%), and Dermaptera and Blattaria with 1 species and 1 family each(1.06%). The insects collected by sweeping contained 275 species, with 81 families and 9 orders. Out of them, Hemiptera was the most diversely identified order, with 58 species and 15 families(21.09%), followed by Coleoptera with 54 species and 1 family(19.64%), Hymenoptera with 42 species and 7 families(15.27%), Diptera with 38 species and 17 families(13.82%), Orthoptera with 27 species and 7 families(9.82%), Lepidoptera with 25 species and 7 families(9.09%), Homoptera with 16 species and 9 families(5.82%), Odonata with 12 species and 4 families(4.36%), and Mantodea with 3 species and 1 family(1.09%) in that order(Figure 3).  

Figure 3. Composition of the species collected at the Yudeung streamside area

Before this study, terrestrial insects at streamside locations were investigated twice. Jung and Yeo(1996) reported 176 species and 199 species at the Changwon stream and at the Nam stream in Changwon city, respectively, and Bae et al.(2002) reported 316 species at the Choyang river and Dong river, which are located respectively in Pyeongchang province and Jeongseon province. Although these studies investigated different areas and at different times compared to this study, Coleoptera was the most diverse order in all of the studies, demonstrating that Coleoptera is a very common order at streamside locations. In particular, Cerambycidae was found to habituate in damp and dark areas under rocks or in trees, whereas Chrysomelidae habituated in wide grass fields at stream side locations, accounting for the high density. Moreover, Hymenoptera and Hemiptera were found to be more common than other types of insects. Fewer species in Lepidoptera were identified because this survey did not use light traps.  

2. Community analysis according to the survey areas

At the Daejeon stream, 178 species, 72 families and 11 orders were collected at the D-1 point; 178 species, 66 families and 11 orders at D-2; 157 species, 53 families and 8 orders at D-3; 146 species, 57 families and 10 orders at D-4; 159 species, 62 families and 9 orders at D-5 point; and 143 species, 58 families and 9 orders at D-6(Table 3). At D-1 and D-2, the most species were identified, at 178 species, while D-6 was the point at which the lowest number of species was identified. This may have arisen because the D-1 and D-2 areas encompass wide forest areas, including the neighboring Mt. Manin, and are far from urban areas, although they have narrow streams and an unstable habitat owing to stream straightening efforts and unclear banks. D-6, showing the lowest number of insect species, passes an urban area, and the water quality worsens as the Daedong stream merges into it near Hyeonamgyo(bridge)(Kim and Seo, 1994). Additionally, people travel through this area quite often on account of the presence of riverbed roads and parking lots, and most of the area is covered with grassy fields. Those factors as a whole may cause the low density of insects. At the Yudeung stream, 160 species, 61 families and 11 orders were identified, at Y-1; 179 species, 65 families and 9 orders at Y-2; 144 species, 51 families and 9 orders at Y-3; 118 species, 53 families and 9 orders at Y-4; 167 species, 65 families and 10 orders at Y-5; 145 species, 54 families and 10 orders at Y-6; 142 species, 59 families and 10 orders at Y-7; 102 species, 48 families and 9 orders at Y-8; 116 species, 52 families and 9 orders at Y-9; and 108 species, 51 families and 9 orders at Y-10(Table 3). Y-2 showed the most species, at 179, and Y-8 showed the fewest species, at 102. Y-2, with the most species, has a wide stream area and excellent quality forest to create diverse habitats for insects. Fewer people travel through this area, allowing this area to have the characteristics of a natural stream. Y-8, with the fewest species has large apartment blocks near the site. At the streamside of Y-8, a grassy field is situated owing to a river improvement project, and there are bicycle and walking paths near this point. Therefore, insect habitats are mostly destroyed owing to the work done to the stream and the banks, mainly for the people who come to rest or exercise there. DGN(the Degree of Green Naturality) is influenced by tire contaminants flowing from riverbed roads, by streamside temperature increases due to the use of concrete blocks, and by dryness owing to the stream straightening project. To resolve these issues, artificial facilities such as riverbed roads and parking lots should be removed in phases and plant communities should be composed to restore it as a close-to-nature stream(Park et al., 2002).  

Table 3. Species composition by survey area at the Daejeon and Yudeung streamside areas

From a community analysis at each investigation point, the diversity index was the highest at Y-5 and D-1, at 3.945 and 3.881, respectively, and lowest at Y-9 and Y-8, at 2.106 and 2.845, respectively. The species richness index was the highest at D-1 and Y-2, at 27.723 and 24.007, and lowest at Y-8 and Y-10, respectively at 13.518 and 14.534(Figure 4). In particular, Y-8, Y-9 and Y-10, which are located at the lower stream of the Yudeung stream, showed a remarkably lower species richness index compared to other points at the Daejeon stream and Yudeung stream. The main problems identified were related to the straightening of the water reservoir, the steady and constant width of the stream, the destruction of vegetation to build riverbed roads, the induction of contaminants from parking lots, a lowered water flow speed on account of the constant water depth caused by the artificial reservoir composition, and the removal of the aquatic plant habitat as a result of the riverbed arrangement (Park et al., 2002).  

The dominance index was highest at Y-9 and Y-7, at 0.650 and 0.514, respectively, and it was lowest at D-1 and Y-5, at 0.304 and 0.228. The evenness index was highest at Y-5 and D-1, at 0.771 and 0.749, respectively, and lowest at Y-9 and Y-7, at 0.443 and 0.584. Y-9 and Y-7 with the highest dominance index had 1,559 and 753 individuals of Tetramorium caespitum, which is the dominant species, which increased the dominance index. On the other hand, those points showed the lowest evenness index owing to the high proportion of the dominant species. At Y-5, the number of individuals of T. caespitum was 173, which is the lowest among the 16 investigation points. Consequently, it showed the highest evenness index and the lowest dominance index at the same time(Figure 5).  

Figure 4. Comparison of diversity and richness indices

Figure 5. Comparison of dominance and evenness indices

3. Similarity analysis

From the analysis of the similarity index of each investigation point, D-5 and D-6 showed the highest degree of similarity, at 60.66%, for the Daejeon stream, which means they have similar habituating environments. These points are situated from the neighbrohood of Hyodong, Daejeon city, to the neighborhood of Jung-dong, where convenience facilities for citizens are located, grassy fields are planted, and weed-removal projects are performed seasonally. At the Yudeung stream, Y-2 and Y-3 and Y-3 and Y-4 showed the highest degree of similarity, at 61.28%, and the next most similar areas were Y-9 and Y-10, with a similarity ratio of 61.44%. Among them, the Y-2, Y-3, and Y-4 areas are well-preserved areas of the upper part of the Yudeung stream, and the Y-9 and Y-10 areas in the lower area show characteristics similar to the Daejeon stream due to the heavy traffic on the riverbed road and the artificial planting of the grassy fields(Table 4).  

Table 4. Similarity index between sampling sites at the Daejeon and Yudeung streamside areas

From the cluster analysis based on the similarity index, the investigation points were classified into three groups: A-1, A-2 and B. The A-1 group included D-1, D-2, D-3 and D-4, covering the upper and midstream areas of the Daejeon stream from its origin to the urban stream area in Daebyeol-dong. The A-2 group included Y-1, Y-2, Y-3, Y-4, Y-5, Y-6 and Y-7, covering the upper and midstream parts of the Yudeung stream from its origin to the urban stream in the Chimsan-dong neighborhood. Te B group included D-5, D-6, Y-8, Y-9 and Y-10, covering the lower parts of both the Daejeon stream and the Yudeung stream which pass through urban areas. Through a comparison of the three groups, the differences in the insect habitats and species diversity according to the natural streamside environments could be identified. Although A-1 and A-2 had similar natural environments, they showed different emergences of insects as a result of their regional differences, as the Daejeon stream and the Yudeung stream had different diversity and richness characteristics in terms of the insect species habituating in the streamside areas. The B group had the typical natural environment of an urban stream, passing Daejeon city, which showed the influence of stream and streamside management on the insect habitats (Figure 6). Although stream naturality is reflected in the streamside management plan, most of these efforts were based on physical factors such as the physical structure and water quality analysis. Therefore, continuous studies regarding evaluation indexes of the physical structure and biological, geological and geographical characteristics and a method to integrate them are necessary(Pyo and Mun, 2011).  

Figure 6. Cluster analysis based on insects collected from 16 sites at the Daejeon and Yudeung streamside areas

Table 5. T-test and correlation analysis for habitat types and community indices

When a T-test was executed to verify the differences in the averages of the groups classified by the cluster analysis, it satisfied the normality and homoscedasticity measures, though a statistical difference was noted in the number of species(P=0.018) and the species richness index(P=0.012). In the correlation analysis to identify the relationship between the number of species and the habitat type, it was found that both the number of species (r=-0.582, p<0.05) and the species richness(r=-0.613, p<0.05) showed a negative correlation(Table 5). Thus, streamside habitats were found to provide diverse habitats for living things, and the straightening of the streamside influenced the number of species and the richness of the insect community, as in earlier studies(Vannote et al., 1980).  

From the results of this study, the characteristics of streamside insect communities were identified and changes in the ecology after river improvement efforts were confirmed. This can provide a model of the species diversity changes in the stream ecosystems through the identification of the relationships between terrestrial insects habituating at streamside areas and benthic macro-invertebrate insects habituating in the stream.  

Appendix 1. List of insect species collected at the Daejeon and Yudeung streamsides

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