雑草生育形による群落構造の研究

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1. Plants which are recognized as weeds constitute a group which are ecologically specialized as they flourish on such unstable lands as cultivated fields, foad-sides, etc. To dynamically analyze of weed communities which are adapted to habitats under various artificial factors, we attach a great importance to the growth form as constituting a part of the life form of weeds and we have accordingly set up a new system of the growth form. 2. Classification of the growth form of weeds is based upon the external, morphological features of vegetative-body of the plants of those species and individuals of weeds which are well-adapted to the life-environments of the cultivated land, in a broad sense including road-sides, fallows and other secondary weed communities possessing extremely artificial factors. 3. Two forms of weed growth are recognized : shoot form and root form. Each of the two forms is classified into 5 divisions, and furthermore into 10 subdivisions as a convenience for actual use (Table 1). 4. Our first examinations of weed communities, utilizing our system of growth form were conducted in the following two regions, which are widely separated and thus afford an excellent comparison. (1) Takasu in Hiroshima City (0.5m and 50m above sea level). This locality was chosen because of its being on the coastal region of the Inland Sea of Seto. (2) Fukiya in Okayama Prefecture (550m above sea lavel). This locality was chosen because it is a rather cool plateau in the Chugoku district. In both regions we studied the cultivated and the abandoned fields for seasonal fluctuation of weed communities with respect to growth form, growth stage, floristic features, weed dominance and the RAUNKIAER's system of life form. The investigations were conducted once or more times during each month from March 1951 to January 1952. 5. The following shows the number of species observed growing in the cultivated land by locality. (The area of each investigation was 20 sq. m.) [table] The number of species observed growing in the abandoned cultivated fields were : [table] Fukiya 48 species abandoned for three years after cultivation (4 were tree seedlings) 6. In our observations of the seasonal aspects of weeds, it was found that the ephemeral plants such as Stellaria media CYR., Stellaria uliginosa MURR., etc. decrease in quantity in summer at Fukiya, but they continue to grow throughout a year, whereas, in comparison, at Takasu they grow as distinct winter annual weeds and are never found in summer. 7. The growing period of summer annual weeds as Digitaria ascendens HENRY, Cyperus microiria STUD., etc. is much shorter in Fukiya than in Takasu. 8. Generally speaking, on the cultivated fields, E of the shoot form is at its maximum in summer, while in winter it is replaced by P, the value of which is the greatest. Moreover, in winter, R, Ca and sometimes T are recognized. Spring is the shifting period of the maximum value from P to E and autumn is that from E to P, and this shift is most likely due to the change of local environmental factors on habitats and to the degree of artificial factors. Some variations in the values are always recognized in each of the types. In the root form, Re shows a particularly great value in winter and spring, but in summer and autumn S and Fb become more abundant than during the periods of spring and winter, and accordingly Re shows a smaller relative value than in the periods of spring and winter. 9. Throughout a year, in the shoot form the value of P is always great and in the root form Re is the greatest, which indicates the distinguished feature of the cultivated fields. 10. In the field which had been abandoned for one year, E of the shoot form covers 64 per cent in summer when it attains the maximum value. In winter R takes the same place as P on the cultivated fields and attains its maximum, and T also shows an increase. In root form, Re, which always shows the greatest value on the cultivated fields, becomes
日本生態学会の論文
1954-07-31

雑草生育形による群落構造の研究

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