著者

森下 正明

出版者

一般社団法人 日本生態学会

雑誌

日本生態学会誌 (ISSN:00215007)

巻号頁・発行日

vol.4, no.2, pp.71-79, 1954-07-31 (Released:2017-04-07)

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1. The relations between the population densities and the rates of dispersion in the experimental populations of the ant-lion and some other insects were examined. 2. For the observation of dispersion of the ant-lion, soil was spread uniformly on the floor, covering the area of 120cm×120cm with the thickness of 2cm on which the individuals were liberated. 3. Two types of behavior of the ant-lion on the experimental field were seen ; one is the normal type, the individuals of which usually make their pits at short distances from the released point when the population density is low, and the other the "unstable" type, in which the individual pit-formation takes place after migration over long distances even in low density. A remarkable increase in the number of unstable individuals was seen when food was not supplied for two or more weeks. 4. When the normal individuals are released in the centre of the field, the rate of dispersion increases with the increase of initial number of individuals. The following equation which relation agrees well with the empirical data : [numerical formula] where y is the number of individuals found in the area S, and N the individuals introduced initially, while b and c are constants. 5. To indicate the degree of population pressure which accelerates the dispersion, an index P was proposed, which is calculated by [numerical formula] 6. Using the data obtained by KONO (1952) with the rice-weevil (Calandra oryzae) and by WATANABE et al. (1952) with the azuki-bean weevil (Callosobruchus chinensis), the change of the dispersion rate with the elapse of time was examined. As the result, it was found that this change is related to the change of the value of c in the equation (1), the relation being as : [numerical formula] where t is the time, and u, v are constants. Thus, the equation of the "density-time-area dispersion curve" is given as : [numerical formula] 7. The change of dispersion rate when the dispersion is disturbed by a barrier was also studied experimentally using the ant-lion. The result showed that the decrease of dispersion rate caused by the barrier is expressed by the increase of the value of c when t→∞. Thus, the degree of barrier effect to the spatial distribution can be represented by the index α, the value of which is given by [numerical formula] where u_1 is the value of u when the barrier exists, and u_0 is the value when no barrier exists. Similarly, the degree of barrier effect to the velocity of dispersion may be represented by the index β, the value of which is given by [numerical formula] 8. By comparing the values of P of three species of insect, it was shown that, the population pressure in unit area is largest in the ant-lion, and smallest in the rice-weevil, while it is intermediate in the azuki-bean weevil, when the population densities are equal to one another.

著者

岡田 光正 木下 富雄 吉良 龍夫 黒岩 澄雄 篠崎 吉郎 島津 康男 寺本 英 森下 正明 山口 昌哉 増山 博行 永平 幸雄

出版者

物性研究刊行会

雑誌

物性研究 (ISSN:05252997)

巻号頁・発行日

vol.24, no.2, pp.65-102, 1975-05-20

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この論文は国立情報学研究所の電子図書館事業により電子化されました。

著者

三木 浩三 松村 智弘 森下 正明 難波 和之 木下 文夫

出版者

社団法人 日本口腔外科学会

雑誌

日本口腔外科学会雑誌 (ISSN:00215163)

巻号頁・発行日

vol.24, no.3, pp.549-552, 1978-06-15 (Released:2011-07-25)

参考文献数

9

被引用文献数

1

著者

森下 正明

出版者

京都大学 (Kyoto University)

巻号頁・発行日

1950-11-04

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旧制

著者

森下 正明

出版者

京都大学

巻号頁・発行日

1950

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博士論文

著者

森下 正明

出版者

日本生態学会

雑誌

日本生態学会誌 (ISSN:00215007)

巻号頁・発行日

vol.46, no.3, pp.269-289, 1996-04-25

被引用文献数

26

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The influences of sample size on the index values of species diversity were examined for various indices which have been used hitherto in community studies, together with several indices newly proposed in this paper. Samples of various sizes ranging from 50 to 4,000 individuals were taken randomly from each of nine types of artificial communities which were set up using paper tips, each representing an individual, and the calculated index values of these samples were compared with each other for each community. The paper tips were made by cutting a card board in about 1×1 cm size. The indices which were least affected by sample size were divisible into three groups. The first group included the β index and allied ones. The indices of the second and third groups had values corresponding to the square root and the logarithm of the respective index values in the first group. The first and the second group satisfied the following quantitative relationship, which has preferable characteristics of diversity index : diversity=richness×evenness. A new method was proposed for estimating the total number of species in the mother community from a sample. The results of comparison between the estimated and actual numbers of species in artificial communities showed that the method might be effective for practical use. The samples of artificial communities were compared with the samples of natural communities, and a number of examples which showed fairly good similarity of structure were found in both communities. It is suggested that not only in artificial communities but also in natural ones, the number of species found in a sample would not reach half the number of species in the mother community when the sample size is smaller than 100 and the value of the β index is larger than 10.