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北海道のカラマツ林に於ける細胞性粘菌の密度の季節変動

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(1)Title. 北海道のカラマツ林に於ける細胞性粘菌の密度の季節変動. Author(s). 神田, 房行. Citation. 北海道教育大学紀要. 第二部. B, 生物学,地学,農学編, 37(1): 1-3. Issue Date. 1986-10. URL. http://s-ir.sap.hokkyodai.ac.jp/dspace/handle/123456789/6429. Rights. Hokkaido University of Education.

(2) (rnzgpB) ^m ^i^- nstoGi^io^. Journal of Hokkaido University of Education (Section II B) Vol. 37, No. 1 October, 1986. Seasonal changes in the density of Dictyostelid cellular slime molds in larch forests of Hokkaido*. Fusayuki KANDA Department of Biology, Hokkaido University of Education, Kushiro, Hokkaido 085. »M® ^7-7 7^^ ^ ij- ^ffl^tt^a®^^®; tt ffl H ff. ^mm^±^w^t]E.^m. Dictyostelid cellular slime molds are soil microorganisms that are widely distributed in forest soil (CAVENDER, 1973). There is only one report in which the density of the cellular slime molds was examined every month over two years (KUSERK, 1980). In this paper, I report seasonal changes over. three years in the density of the Dictyostelid cellular slime molds in the forest soils of Hokkaido, Japan's northernmost island. Investigation was carried out by means of the clonal isolation technique that permits the quantitative sampling of cellular slime molds (CAVENDER and RAPER, 1965 ; KANDA,. 1981). Soil samples were collected every month from April, 1981, to March, 1984, at 3 to 10 different plots in larch forests in the vicinity of Kushiro, Hokkaido. Samples were taken from both the soil surface and the humus layer that contained the fermenting needles of larch-trees besides a small quantity of leaves of Sasa sendaika. The isolation of the cellular slime molds was carried out , according to previously described techniques (CAVENDER and RAPER, 1965 ; KANDA, 1981,. 1983). Aliquots (0.5ml) of the prepared soil suspension were diluted 1/20 with sterilized distilled water, mixed with pre-grown Escherichia coli cells and spread evenly on non-nutrient agar plates (60 cm2, pH 6.4) (see KANDA, 1981, 1983). The plates were then incubated at 23°C'for 4 to 10 days, * This work was supported by a Grant-in-Aid for the Encouragement of Young Scientists (No. 5774032) from the Japanese Ministry of Education, Science and Culture.. (D.

(3) Fusayuki KANDA. f. /\. /•\. f \. sirfi: 8. ^. & 0. M I .t y). 0/. \. <. \. /. rf^"\\. 7 V. // ^7 0. Ky;. \. -1180c. p\. / /^<. f\*\. /'. D). ^20. A.. ^. tie. \. -?. /o--d >-< ^ /\. )8 ^6. -|10. ^4 ^2. I. t. v. \. ^. V:. p. -2. H. i-6. '0. T. \w. 1-8. +10 t. 11. 11. 5'6'7'8'g'. 1981. t t 1_t L J It! I I I. lo'n'ch1' 2 34 5 6 7 891011121 1234. 1982. t I I 1 t I I I I 1 I. 5 67 8 91011121 1 2 3~ 1983 1984. Fig. 1 Seasonal change in the absolute density of cellular slime molds in larch forest soil over a three year period. —®— , absolute density (clones / g soil). •"O"-, average montMy temperature.. followed by a counting of the number of clones of the cellular slime molds.. Figure 1 shows that the absolute clone density of the cellular slime molds changed from 10 to 1.54 X 103 clones/g of soil over three years (from April, 1981 to March, 1984). The clone density was highest in 1982 and lowest in 1983. The highest value of the absolute density was recorded in •. October, 1982. There were two to four developing peaks of clone density in a year. Two major peaks occurred between August and October, and between December and January. In 1982, another. peak (830 clones/g of soil) was observed during the spring. In the spring of 1981 and 1983, however, the densities were low. Seasonal lows occurred in winter. In addition, minor lows were. seen in June and November in 1981 and 1983, and in July and September in 1982. KUSERK'S report has indicated that there were numerical peaks in the oak-beech forest of Delaware, North America, during, his two-year survey, and that some major peaks occurred in October and November, while peaks observed in spring were different from year to year (KUSERK, 1980). CAVENDER and RAPER (1965) also reported on data collected from forests in Wisconsin, North. America. According to their data, the cell density of cellular slime molds in soil was highest in autumn in almost all parts of the forests. The present result obtained from the larch forests of. Hokkaido shows a similar pattern to that existing in North America ; that is, the density is high in the period from autumn to winter, although it does not change so frequently as in KUSERK. This seasonal. change in the density pattern may be explained by assuming good conditions for growth of the cellular slime molds, caused by the nutrients supplied from freshly fallen leaves or needles in the temperate area.. I am grateful to Dr. M. IWABUCHI of Hokkaido University for his critical reading of this. (2).

(4) Seasonal changes in the density of Dictyostelid cellular slime molds in larch forests of Hokkaido 3 manuscript. Thanks are also due to Mr. K. KIKUCHI, Mr. Y. IMAI and Mr. Y. KOHZAI for generous assistance in carrying out experiments, and to Mis M. BEYLER for correcting the English expressions in the manuscript.. References. CAVENDER, J. C. (1973) Geographical distribution of Acrasieae. Mycologia, 65 : 1044-1054. CAVENDER, J. C. and RAPER, K, B. (1965) The Acrasieae in nature. II. Forest soil as a primary habitat. Amer. J. Bot., 52: 297-302.. KANDA, F. (1981) Composition and density of Dictyostelid cellular slime molds in the Kushiro moor, Hokkaido. Jap. J. Ecol., 31: 329-333.. KANDA, F. (1983) Composition and density of Dictyostelid cellular slime molds in Phragmites comimmis communities in the Kushiro moor and relationship between vegetation and distribution of cellular slime molds. Jap. J. EcoL, 33: 453^60. KUSERK, F. T. (1980) The relationship between cellular slime molds and becteria in forest soil. Ecology, 61: 1474-1485..

(5)

Fig. 1 Seasonal change in the absolute density of cellular slime molds in larch forest soil over a three year period.

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