• Journal of Korean Society of Forest Science
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• v.90 no.3
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• pp.380-387
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• 2001

The characteristics of ecological niche, breadth and overlap, for seventeen major tree species were evaluated in the natural deciduous forest in Mt. Chumbong area. Employed by the plot sampling method, the environmental gradient for vertical niche was based on the intensity of light within the forest, and that for horizontal niche was based on multi-dimensional resources in distribution pattern. The result showed that Fraxinus rhynchophylla had the highest value of vertical niche breadth and Maackia amurensis had the lowest, and Acer pseudo-sieboldianum had the highest value of horizontal niche breadth and Betula costata had the lowest. There was no significant correlation between both measures of niche breadth. However, the tolerance index for each species was positively correlated to the values of niche breadth. Spearman's rank correlation coefficients were applied to test the correlationship between the species ranks of tolerance index and those of two ecological niche breadths. The coefficient of $r_s=0.432$ ($P{\leq}0.1$) was not enough to support significant correlationship between the tolerance index and vertical niche breadth at the 95% probability. If Carpinus cordata, rarely reach canopy of the forest due to its own growth form, are excluded from the analysis, coefficient was calculated as $r_s=0.650$ ($P{\leq}0.01$), resulting in highly significant correlationship. The Spearman's rank correlation coefficient was $r_s=0.797$ ($P{\leq}0.01$) for tolerance indices and the values of horizontal niche breadth, indicating highly significant. Four distinctive species groups, produced by cluster analysis on the basis of ecological niche overlap for each pair of species, were in considerable accord with the positively associated species constellation pattern created by the inter-species association analysis.

• The Korean Journal of Mycology
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• v.27 no.4 s.91
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• pp.283-288
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• 1999

The effect of water activity ($a_w,\;0.9{\sim}0.995$) and temperature ($18{\sim}30^{\circ}$C) on in vitro growth and interactions between ochratoxin-producing Aspergillus ochraceus and six other fungi (Alternaria alternata, Aspergillus candidus, A. flavus, A. niger, Eurotium amstelodami, E. rubrum) isolated from maize grain were investigated. A. ochraceus and each six other species were paired and their interactions given a numerical score to obtain an index of dominance ($I_D$) for each species. Generally A. ochraceus was very competitive and dominant against other fungi. It was, however, dominanted by Alternaria alternata and A. niger at high $a_w\;(0.995\;a_w)$, and mutually antagonistic when paired with E. amstelodami and E. rubrum at low $a_w\;(0.9\;a_w)$. The growth rates of each species were also calculated under the same range of environmental conditions. They were markedly influenced by aw and temperature. At high temperature ($30^{\circ}C$), A. ochraceus grew most rapidly under slightly drier conditions ($0.95\;a_w$), while A. alternata, A. flavus and A. niger did at high water availability level ($0.995\;a_w$). At $18^{\circ}C\;and\;25^{\circ}C$, and high $a_w$ level ($0.995\;a_w$), A. alternata grew fastest, while A. candidus, E. amstelodami and E. rubrum grew very slowly. Using Biolog plates the effect of $a_w$ and temperature on utilization patterns of carbon sources in maize was evaluated. The niche overlap index (NOI) relative to A. ochraceus was determined and compared with that of each interacting species. Under high water available condition ($0.995\;a_w$). the NOI of A. ochraceus was often >0.9, indicative of the coexistence with other interacting species. However, against E. amstelodami and E. rubrum at $18^{\circ}C$, the species had NOI <0.8, indicative of occupation of different niches. At low $a_w\;(0.95\;a_w)$, NOI for A. ochraceus was <0.8 when paired with A. alternata and A. niger also suggested the occupation of different niches.

• Journal of Forest and Environmental Science
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• v.28 no.3
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• pp.158-169
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• 2012

Sabah has experienced a rapid decline in the extent of forest cover. The precise impact of habitat loss on the conservation status of the plants of Sabah is uncertain. In this study we use the niche modelling algorithm MAXENT to construct preliminary, revised and final ecological niche models for Dipterocarpus lamellatus and Dipterocarpus ochraceus and combined these models with data on current land-use to derive conservation assessments for each species. Preliminary models were based on herbarium data alone. Ground surveys were conducted to evaluate the performance of these preliminary models, and a revised niche model was generated from the combined herbarium and ground survey data. The final model was obtained by constraining the predictions of the revised models by filters. The range overlap between the preliminary and revised models was 0.47 for D. lamellatus and 0.39 for D. ochraceus, suggesting poor agreement between them. There was substantial variation in estimates of habitat loss for D. ochraceus, among the preliminary, revised and constrained models, and this has the potential to lead to incorrect threat assessments. From these estimates of habitat loss, the historic distribution and estimates of population size we determine that both species should be classified as Critically Endangered under IUCN Red List guidelines. Our results suggest that ground-truthing of ecological niche models is essential, especially if the models are being used for conservation decision making.

• Korean journal of communication and information
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• v.19
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• pp.7-36
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• 2002

The purpose of this study is to compare the webcasting and television from the perspective of genres. It adopted the niche theory in analyzing them, avoiding simply comparing the collective average of the two media's gratification. As a result, television turned out to expand broader at niche breadth than the Webcasting and thus presented more diverse functions thar the Webcasting. The niche overlap was investigated with the average of overlapping values. The competition between the two media was rather eased in dimensions of education, culture, and entertainment. And in terms of competitive superiority, the music service sector was the only function that the Webcasting had superiority to television. Upon the results, the Webcasting was absolutely inferior to television in a whole sense. But one thing which requires consideration is that the Webcasting will have functional mergers among genres and thus develop different functions from the corresponding ones of television.

• The Journal of the Korea Contents Association
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• v.20 no.9
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• pp.261-270
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• 2020

This study aimed to investigate the competing relationships among webzines, TVs and online video platforms in terms of usage gratification of consumption of beauty contents based on niche theory. Five types of usage gratification including information, entertainment, attractive characters, convenient usage and honesty were identified from the previous literature and they were used for niche analysis. The findings showed that online video platforms had the wider breadth than webzines and TVs in all dimensions of usage gratification except for attractive character and TVs and online video platforms had the least niche overlap. The results also revealed that online video platforms had the competitive superiority over the other media in terms of convenient usage and honesty. This study has meanings in a way that it can be used as guidelines for how the future consumption patterns of beauty contents will be.

• Journal of Wetlands Research
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• v.25 no.3
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• pp.205-212
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• 2023

This study was attempted to find out how the ecological niche and interspecies relationship of Quercus aliena and Q. serrata, which are the main constituents of potential natural vegetation along the riverside of mountains in Korea, under climate change conditions. To this end, soil moisture and soil nutrients were treated with 4 grad ients under climate change conditions with elevated CO₂ and temperature, plants we re harvested at the end of the growing season, growth responses of traits were measured, ecological niche breadth and overlap were calculated, and it was compared with that of the control group(ambient condition). In addition, the relationship between the two species was analyzed by principal component analysis using trait values. As a result, the ecological niche breadth of Q. aliena was wider than that of Q. serrata under the moisture environment conditions under climate change. Under nutrient conditions, the ecological niche of the two species were similar. In addition, the ecological overlap for soil moisture of Q. aliena and Q. serrata was wider than the soil nutrient gradient under climate change. The species with traits in which the increase in ecological niche breadth due to climate change occurred more than the decrease was Q. aliena in both water and nutrient gradients. And in the responses of the population level, due to climate change, the adaptability of Q. aliena was higher than that of Q. serrata under the soil moisture condition, but the two species were similar under the nutrient condition. These results mean that the competition between the two species occurs more severely in the water environment under climate change conditions, and at that time, Q. aliena has higher adaptability than Q. serrata.

• Korean Journal of Agricultural and Forest Meteorology
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• v.15 no.3
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• pp.153-160
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• 2013

This study was conducted to investigate the effect of ecological factors affecting Pinus densiflora forest distribution associated with climate change in the future. Ecological niche is used as a method to quantify the position occupied in biological communities, space, influence and all ecological factors. Ecological niche breadth was analyzed on meteorological and growth factors of P. densiflora. Nine sites (i.e., Gangneung, Jeongseon, Pyeongchang, Hamyang, Bonghwa, Yeongyang, Uljin, Uiseong and Boseong) were selected to set $20m{\times}20m$ quadrat from September to October 2010. The height, DBH, clearlength, crown width and basal area were measured at each quadrat and used as growth factors. In addition, the measured values from the closest weather stations of each survey area of the maximum, mean and minimum temperature, humidity and precipitation were used as meteorological factors. The ecological niche breadth of the five meteorological factors except humidity was low. It is considered that precipitation could effect on the distribution of P. densiflora forest. In particular, maximum temperature showed low ecological niche breadth less than 0.4 in most of the survey areas. However, the ecological niche breadth of the five growth factors was high in all survey areas.

• Journal of Wetlands Research
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• v.25 no.2
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• pp.159-165
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• 2023

This study measured the ecological niche overlap between two deciduous oak species(Quercus acutissmia and Q. dentata) according to the change in growth responses after treating with the moisture and nutrient contents of the soil at four gradients, and interpreted the degree of competition between the two oak species by ordination method. In the moisture environment gradient, the ecological niche overlap of the two species was high in the photosynthesis-related leaf organs and low in plant architecture such as shoot length. In addition, in case of competition between two oaks, Q. dentata was remarkably dominant in soil moisture gradient, but Q. acutissimia slightly was slightly advantageous over Q. dentata in the soil nutrient gradient. These results show that even in a similar taxonomical group growing in a similar habitat, the response to the organ system of the plant varies depending on the type of environment factor, resulting in different competitive differences among plants.

• Journal of Korean Society on Water Environment
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• v.33 no.5
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• pp.587-599
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• 2017

Physical environmental factors (water depth, current velocity and substrate) and fish community were surveyed in the Gapyeong stream, Korea. The fish group of Gapyeong Stream was divided into three types. Lithophilic fish, Koreocobitis rotundicaudata and Pseudopungtungia tenuicorpa preferred shallow depth, low-velocity current, and coarse bed condition, whereas Coreoleuciscus splendidus and Microphysogobio longidorsalis were adapted to high-velocity current and bed materials. Nektonic fish, Zacco koreanus and Zacco platypus appeared in a wide range of physical conditions. Intermediate fish, Hemibarbus longirostris, Pungtungia herzi and Coreoperca herzi adapted to moderate water depths and current velocities. Among them, H. longirostris and C. herzi were adapt to various bed materials. C. splendidus, M. longidorsalis and P. herzi showed high niche overlap for current velocity, water depth and substrate with Z. koreanus and Z. platypus. The occurrence of M. longidorsalis in a relatively low-velocity current compared to Z. koreanus and Z. platypus suggests that the current velocity act as a isolation factor for these species. The competition, isolation and character displacement among these species investigated detail in the future. Based on canonical correspondence analysis, the relative importance of each environmental factor was determined as substrate > water depth > current velocity.

• Korean Journal of Environmental Biology
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• v.26 no.4
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• pp.385-391
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• 2008

In Korea, Quercus acutissima distributed in good condition with high nutrients and moisture content, but Quercus variabilis in dry soil or rock habitate. In order to understand this ecological distribution of Q. acutissima and Q. variabilis, we cultivated the seedlings of two oak species treated with light, soil moisture and nutrient gradients each four level, from May to October in glass house. Then we measured the ecological niche breadth and niche overlap of the two species, and analyzed the relationship of competition using cluster analysis and PCA ordination. Ecological niche breadths of Q. acutissima under moisture and nutrient treatments were slightly wider than those under light one. Among 14 characters measured, 6 characters related with length items were wider in all the environmental treatments, but 8 characters connected with weight terms narrower in light treatment. Ecological niche breadths of Q. variabilis under moisture and nutrient treatment were wider than those of light one. Ecological niche of Q. acutissima was wider than those of Q. variabilis in all the environmental treatments. Ecological overlap between two species was higher with a range of 0.87$\sim$0.92, especially higher in soil moisture factor. These results means that Q. acutissima is more competitive than Q. variabilis, especially in soil moisture condition. Two species were ordinated with distinct group based on 9 characters. From these results, it can be explained that what Q. variabilis distributed in bad soil condition is due to the escape strategy, because of its low competitive ability to Q. acutissima in natural communities.