Ecological Studies on Pinus Densiflora Forest 1. Effects of Plant Substances on the Floristic Composition of the Undergrowth

Bet. Mag. Tokyo 76: 400-413 (November 25, 1963)

Ecological Studies on Pinus densiflora Forest 1. Effects of Plant Substances on the Floristic Composition of the Undergrowth

by I1 Koo LEE* and Masami MON SI * *

Received October 8, 1963

The vegetation under Pinus and Abies is, as we usually observe, thin and sparse. But we fail to realize the repulsive effects with which Pinus and Abies work against the natural growth of a fair number of other species, because we generally attribute this to the insufficient light, or become confused with a few different species growing there. A frank evidence in this regard is the phenomenon that weeds which grow thick in crop field cannot invade the adjoining red-pine forest where the light condition is thought rather favorable because of a relative light intensity of 28 to 35 °o with the thin canopy. A closer, continuous observation will discover that some plants in the undergrowth of pine trees lead but an abnormal life, flowerless or barren. Hereupon we recall Knapp'sl' emphasis on the importance of chemical secretion of plants in the experimental sociology, and Bonner's chemical sociology among the plants2' . Such interaction between two plants through chemical secretion was named by Molisch3' allelopathy. Recently a comprehensive review on allelopathy, or chemical influences of other plants was given by Evenari4>, and the details will be discussed later. The present paper is to substantiate through experiments and investigations the senior author's patient observation on red-pine forests in Korea and his presumption that the red-pine tree be secreting substances inhibiting the germination and growth of different species. To remark parenthetically, 60 to 70% of the forest land in South Korea is occupied with red-pine trees, developing a thin, sparse vegetation as well.

Floristic Characters of the Undergrowth of Pinus densiflora Forest

It has been and is usual to try to express numerically the natural combination of plants by means of cover degree, density, frequency, constancy, vitality and adaptability of each plant, the presumed primary factors for the combination being soil, climate and sunlight. On the other hand, we also realize a relative degree of affinity of a species to a plant community, terming it "fidelity ". Table 1, where the plants with high vitality of 1 or 2 and high frequency in the undergrowth of Pinus densiflora forest are tabulated, has been prepared according to investigations in South Korea and Japan, excluding Hokkaido, and it aims at deter- mining the variety and vital combination of species under the red-pine forest. Vitality used here was graded into 4 classes after Braun-Blanquet5' , and the plants were consti- tuents of the undergrowth less than 6m in height. The table covers the authors-surveyed 20 spots in South Korea (near Seoul) and 30 spots in Kanto district and the authors- * Department of Biology, Faculty of Science, Kyung Hee University, Seoul, Korea. Present address : Department of Botany, Faculty of Science, University of Tokyo, Hongo, Tokyo, Japan. ** Department of Botany, Faculty of Science, University of Tokyo, Hongo, Tokyo, Japan. November, 1963 LEE, I. K., and MONSI, M. 401

Fig. 1. Distribution of Pinus densiflora forest stands treated in the paper. One spot means 5 quadrats. 750 quadrats from Yoshiokas> and 50 quadrats were surveyed by the authors. selected 750 spots out of Yoshioka's quadrats in Ecological studies on Japanese pine forests "6)• The latter 750 spots were selected from a large number of quadrats described by Yoshioka by choosing only red-pine stands in which the cover degree of P. densiflora in tree stratum was higher than 4.5. The black-pine (P. thunbergii) forest stands were excluded. The plants described in the table are characteristic speciess of the red-pine forest at least in one district, though they may fail to be characteristic species in other districts. As for the vitalities given in the table, Prof. Yoshi-- oka kindly informed his investigations. The rest are based on the authors' survey. To speak of the main characteristics in the table, Quercus serrata, Prunus jama sakura, Symplocos chinensis var. leucocarpa, Sorbus alnifolia, Rhododendron obtusum var. kaempferi, hex crenata, Cast anea crenata, Lyonia neziki, Styrax japonicus, Eurya japonica, Miscanthus sinensis, Pteridium aquilinum and Atractylis ovata are found well combined with red-pine forest in almost all the districts, while Rhus tricho- carpa, Lespedeza buergeri, Viburnum dilatatum, Rhododendron macrosep alum, Pleio- blastus chino, Carex lanceolata, Ophiopogon japonica, and Dicranopteris dichotoma are judged to have high local adaptability. 402 Bot. Mag. Tokyo Vol. 76

Table 1. Undergrowth plants with high vitality of 1 or 2 and high frequency of Pinus densifora forests in Japan and South Korea. November, 1963 LEE, I. K., and MONSI, M. 403

Experimental Materials Plant seeds : Soils sampled under the red-pine trees and extracts taken from the leaf, root and shoot of the pine tree were used for the tests of germination and growth of the following 15 species, the objective being to examine Pinus densiflora in its inhibitive effects against other species. The material plants could be grouped into two groups, a) characteristic components of the pine forest with a vitality of 1 or 2, and b) non-characteristic of the pine forest and their vitalities are 3 or 4. To the former belong Miscanthus sinensis, Paederia chinensis, Platycodon grandiflorum, and Atractylis ovata. Pinus densiflora itself belongs of course to this group, and it was always used for comparison in the experiment. To the latter belong Setaria viridis, Amaranthus patulus, Achyranthes japonica, Chenopodium album, Polygonum blumei, Phytolacca americana, Desmodium fallax, Galinsoga ciliata, and Aster scaber. Also Himalayan indigo, Indigofera gerardiana, was employed in germination test. The seeds of these plants were collected in the suburbs of Tokyo and in the autumn of 1962 mainly. Pinus densiflora extracts : The root extact was taken through submerging two roots, 9-7.5 mm in diameter and 180 cm in length, and 6.5-4.5 mm in diameter and 80 cm in length, collected in April 1963 at Abiko (Chiba Pref.), in 1 Z of 80° hot water for 24 hours. The total fresh weight of the materials was 300g. Both roots were 404 Bot. Mag. Tokyo Vol. 76 excavated from the upper stratum of 10 cm of soil, together with fine roots grown thickly on them. Fresh- and fallen-leaf extracts were prepared with hot water (80°, 200 g fresh leaves/l, or 250 g fallen leaves/i) or with cold water (18°, 200 g fresh leaves/l, or 200 g fallen leaves/i). These were left alone for 24 hours. The fallen leaves were not so old after defoliation. Soils : Soils not from the red-pine forest were collected from the nursery in Tokyo University campus, from 150 cm under the ground of a vacant lot in Tokyo University Farm at Tanashi, and from the Experimental Field of Tokyo Kyoiku University at Hoya, respectively. Soils under the red-pine forest were collected at Mashiko (Tochigi Pref.), Toride, Koginu (Ibaraki Pref.), and Abiko (Chiba Pref.). The characteristics of the soils are summarized in Table 2.

Table 2. Characteristics of the soils used for the experiment. Field capacity, ignition loss, N and K content are expressed as percentage on a dry weight basis.

(a) Germination experiment : Three sheets of filter paper were spread on a Petri dish and poured onto the Pinus densiflora extract so much as sufficiently to moisten the filter paper. Thereon were placed 50 grains o seeds of P. densi ora, Amaran- thus patulus and Achyranthes japonica. Other Petri dishes were prepared with 1/2 and 1/4 diluted extracts as well as pure water for the control. The temperature was kept at 25° for all the germination tests. These experiments were carried out in the dark as well as in the light. A result with fresh-leaf extract in these species is shown in Figs. 2 and 3 (see also Plate VI, Fig. 2. Germination test with the cold- A and B). Germination of red-pine was water extract of Pinus densiflora fresh found free from the inhibitive effect of the leaves. Sown on June 11, 1963. Q, Pinus densi flora ; •, Amaranthus extract for all the dilutions, while those of patulus; O, Achyranthes japonica. Amaranthus, Achyranthes, Indigofera ge- November, 1963 LEE, I. K., and MoNst, M. 405

Table 3. Germination test with various extracts of Pinus densi flora. Mean germination percentage of 6 tests held between Nov. 27, 1962 and March 5, 1963. Seeding 50 grains a dish.

rardiana were inhibited. The germination-inhibiting effect was stronger in hot-water extracts than in cold-water extracts. Fallen leaves, too, proved an inhibitive effect on the germination. The germination tests for Akebia quinata, Galinsoga ciliates, Phytolacca americana, Polygonum blumei, Macleya cord ata and Aster scaber were suspended, since germination was hardly observed neither in pure water nor in the extracts. Two kinds of soil, that is, one from the Experimental Nursery of Tokyo University and one from a red-pine-forest stand at Abiko, Chiba Pref., were packed separately in a wooden frame, 30 x 30><10 cm3 in the clear, each containing 6.2 kg of fresh soil. Planted in each frame were respective 50 grains of the seed of Ama- ranthus patulus, Achyranthes japonica, Setaria viridis and Desmodium fallax var. manshuricum, all of which are ranked in vitality 4 under red-pine forest, and those of P, densiflora, Atractylis ovata and Aster scaber of which vitalities are 1 or 2. The sowing date was April 14, 1963. Water was supplied once a day, while the temperature being left to atmospheric change.

Fig. 3. Germination rates of various plants sown on two different soil beds. Continuous lines mean red-pine forest soil of Abiko, and broken lines, farm soil of Tokyo Univ. campus. 1, Amaranthus patulus; 2, Achyran- thes japonica; 3, Setaria viridis; 4, Pinus densiflora; 5, Aster scaber; 6, Atractylis ovata; 7, Desmodium fallax.

As seen from Fig. 3, the germination dates for Pinus and Desmodium were ear- Tier in the red-pine-forest soil than in the farm soil of Tokyo Univ, campus, whereas 406 Bot. Mag. Tokyo Vol. 7& the rest of species germinated earlier in the latter soil. No marked differences, how. ever, were observed in germination rate between both soils. (b) Growth experiments: Growth of the seedlings in the above-mentioned experiment was quite different in each species. The results are illustrated in Fig. 4_

Fig. 4. Growth of various plants in two different soils. Continuous lines mean red-pine-forest soil of Abiko, and broken lines, farm soil of Tokyo Univ. campus. 1. Setaria viridis; 2, Amaranthus patulus; 3, Achyranthes japonica; 4, Aster scaber; 5, Desmodium f allax; 6, Atractylis ovata; 7, Pinus densiflora.

The growth of P. densiflora was better in the red-pine-forest soil than in the farm soil of Tokyo Univ. campus (Plate VI, C, D, E, F, and Plate VII, G). The growth of Atractylis ovata was equal in both soils and that of the rest species was better inn the latter soil. Aster (vitality 3), Achyranthes (4) and Desmodium (4) showed some depression in growth on the red-pine-forest soil. Most remarkable inhibition of the red-pine-forest soil was seen in the seedling growth of Amaranthus patulus (4), a na- turalized species. Setaria (4) came to the second in the growth depression. Further experiments as to the inhibitive effect. of red-pine-forest soil on seedling growth were carried out with soils from various localities. Plastic pots of 6 cm in diam. and 3 cm high were packed respectively with about 450 g of fresh soils from the Experimental Nursery of Tokyo University campus and the red-pine-forest stand at Mashiko, Toride and Abiko. Seeds of the following species were sown thereon separately: Amaranthus patulus, Achyranthes japonica, Phytolacca americana, Che- nopodium album, Aster scaber, Pinus densiflora and Paederia chinensis. After sowing,, water was sufficiently given everyday as well as 1/1 Boysen-Jensen's nutrient solution that included micro-elements, once a week. Ten grains a pot were sown on May 13, 1963. Results of the germination and growth are shown in Fig. 5, and Plate VII, H, I, J and K. The different sampling dates of plants correspond to different rapidities of the growth: slow-growing species was sampled later accordingly. November, 1963 LEE, I. K., and MONSI, M. 407

Fig. 5. Germination and growth in dry weight on various soils. Farm soils, Tokyo Univ, campus; red-pine-forest soils, Mashiko, Toride and Abiko. Amaran- thus patulus, Aehyranthes japonica, Phytolacca americana, Chenopodium album, Aster scaber, Pinus densiflora and Paederia chinensis, sown on May 14, 1963.

When compared the growth of seedlings on the Tokyo Univ. soil with that on red-pine-forest soils, Amaranthus, Achyranthes, Phytolacca and Chenopodium, which have a vitality of 4, grew far better in the Tokyo Univ. soil. Aster whose vitality is 3 resulted in some fair difference in growth. Pinus and Paederia with vitality of 1 presented almost equal or a little better growth on the red-pine-forest soils. The authors executed the same experiment in Amaranthus patulus with another non-red-pine-forest soil which was brought from the Experimental Field of Tokyo Kyoiku University at Hoya, to obtain almost the same result as with the Tokyo Univ. soil. Experiments on the same line were made in Polygonum blumei, Platycodon grandiflorum, Galinsoga ciliata, Miscanthus sinensis. Soils of Tokyo University campus and of Hoya Experimental Field of Tokyo Kyoiku University were non-red-pine-forest soil. Red-pine-forest soils were collected from Mashiko, Koginu, Toride and Abiko. These soils were packed separately in porous pots in the amount of 360 g and in the same manner as in the experiment mentioned above. Pots were kept in a greenhouse and left exposed to open air. Fig. 6 shows the results of this experiment. Polygonum and Galinsoga (vitality 4) were much inhibited in their dry-weight growth on the red-pine-forest soils, while Platycodon and Miscanthus grew almost equally on both kinds of soils. The effect of the cold-water extract of fresh Pinus densiflora leaves on the growth of seedlings of Miscanthus sinensis and Amaranthus patulus was tested. An artificial soil, vermiculite, which contains no organic matters, was packed in 8 porous pots, 4 of which were planted each with 10 Miscanthus seedlings (individual fresh weight, 8 mg) and the rest each with 10 Amaranthus seedlings (1 mg). Three different concen- 408 Bot. Mag. Tokyo Vol. 76

Fig. 6. Germination and growth in dry weight on various soils. Farm soils, Tokyo Univ. campus and Hoya Experimental Field; red-pine- forest soils, Mashiko, Toride, Abiko, and Koginu. Polygonum blumei, sown on May 23, 1963; Platycodon grandiflorum and Galinsoga ciliata, sown on Aug. 5, 1963; Miscanthus sinensis, sown on July 20, 1963.

Fig. 7. Effect of Pinus leaf extracts on growth of various plants. A, Dry weight in mg; 1, Miscanthus sinensis; 2, Amaranthus patulus. B, Fresh weight in g. 1, Setaria viridis; 2, Achyranthes japonica; 3, Pinus densi flora. tration, 1, 1/2, 114, of the Pinus extract, 30-40 ml a day, and pure water as a control, were applied. Nutrient solution was also given once a week to prevent any defi- ciency of the mineral nutrients. Amaranthus, (vitality 4) was heavily inhibited in its November, 1963 LEE, I K., and MONSI,M. 409

dry weight growth by the Pinus extract (Plate VII, L), while Miscanthus (vitality 1) was not influenced (Fig. 7-A). Fig. 7-B also shows the result of similar experiment obtained in Pinus densiflora (vitality 1), Setaria viridis and Achyranthes japonica (vitality 4) : the first was not influenced, but the second and the third diminished their fresh weight with increase of concentration of the Pinus extract.

Negative Geotropism of Roots

When we give eosin solution to seeds just prior to the sprouting, the roots, as is well known, turn upward. The same effect was also observed in Amaranthus patulus with extract of Pinus densiflora shoots or seedlings as well as with that of Quercus acutissima seeds or tea grounds. The Pinus-shoot extract used was prepared by put- ting 560 g fresh weight of shoots into 11 water and leaving alone for 24 hours. The tea extract was 11 of water put with 200 g dry weight of green-tea grounds and left alone for 24 hours. The occurring rates of negative geotropism due to the Pinus-shoot extract were in Amaranthus patulus 50% in the 1/2 dilution and 32% in the 1 /4 dilution, where those rates due to tea extract were 35% and 9 °o for the 1/2 and 1/4 dilutions, respectively. On the other hand, the rates of negative geotropism of Amaranthus due to tannic acid were 40% in 0.5% solution and 10% in 0.1% solution. Although this pheomenon was not directly observed in the soil of Pinus densiflora forest, the retarded sprouting of many species which do not combine well with P. densiflora may possibly be ascribed to the effect of this sort.

Preliminary Investigation into the Inhibitor

We have thus determined the fact that Pinus densiflora extract and the red-pine- forest soil apparently contain some inhibiting substances for germination and growth of plants which rarely appear in the forest. It is our common knowledge that Quercus, Prunus, Rhus and Rhododendron, which usually combine well with P. densiflora

Fig. 8. Effect of coumarin concentration on the germination of Amaranthus patulus. O, 4 days; 8 days after sowing. 50 grains a dish. 410 Bot. Mag. Tokyo Vol. 76 forest, have tannin component in common. The authors could detect tannin component in the Pinus extract7~ . As to the germination-inhibitive effect of tannic acid an experiment in Amaranthus patulus was made. At a rather high concentration of 5% of tannic acid the germination percentage was heavily depressed. The seed of Amaranthus, however, is very sensitive to coumarin (Fig. 8). A concentration of 0.01 of coumarin already inhibited the germination of Amaranthus, and this corre- sponds to the growth inhibition in Avena coleoptile8~ . Anyhow, it will be premature to conclude tannin as being the inhibitor, since the tannase, a microbic enzyme, in the soil, can destroy tannin and may cause complex changes. Still more, p-coumaric acid, which exists in Pinus (after Dr. Yoshida, un- published) and is known as a strong inhibitor of germination and growth4~ , has been detected by paper-chromatography in red-pine-forest soil at Abiko and in the Pinus extract, though its quantitative determination is to be due deferred. There is also the possibility of some substances quite peculiar to Pinus densifl'ora to exist, because the chromatography detected a fluorescence apparently different from that of p-coumaric acid.

Discussion and Conclusion

From Table 1 it is apparent that there is a high similarity between South Korea (near Seoul) and Tohoku district of Japan in the floristic composition of the undergrowth of the red-pine forest, and that there are many common species throughout Japan. The table includes 33 families, 46 genera, 58 species and 6 varieties. These plants must survive under the effects of the dominant species, Pinus densiflora. As to the chemical effects of the Pinus the authors' experiments dealt with only a few species. The authors, however, are convinced that those plants listed in Table 1 are in their germination and growth not or only in lower degree vulnerable to the effects of the Pinus extract or of the red-pine-forest soil. We generally owe to the phytosociological studies the finding of the different: degrees of affinity among plant species and the description of floristic combination, but it has never successfully tried to elucidate the causes of a given floristic combination. The commonplace explanation, if any, was based upon such factors as shade by dominant species, soil, climate or the like.

Table 4. Relative light intensities above the undergrowth of various forests (including orchards) in the suburbs of Tokyo. November, 1963 LEE, I. K., and MoNSI, M. 411

As for the light condition, for example, Table 4 will suffice to explode the usual concept of this kind. The interior of the red-pine forest is one of the brightest among forests. It is rather favorable for the undergrowth, and there should be many shade tolerant species which could invade the area. In reality, however, we have generally sparsely-vegetated red-pine forest, especially in Korea. The finding that red-pine trees grow a thin vegetation under them is not new but has been so pointed out by many researchers. Beside the weeding and thinning of the undergrowth, Miyazaki9' , for example, attributed this phenomenon to the my- celoid net of mycorrhiza which develops in the soil and tends to stop rain water penetration and to eventuate in an over-arid state of the soil. This may form a good reason, though not sufficient enough, for there are many species that grow well in such an arid area. It is in this conjecture that the authors try herewith to reduce the interrela- tionship among plant species to their chemical components, though we do not turn as being absolutely obsolete the general way of explanation, that is the theory of inter- specific economic struggle for light, water and inorganic nutrients. To stand in this angle of view and study the ancient documents of Japan, we find Banzan Kumazawa, who already mentioned about 300 years ago that rain water or dew which comes washing the leaves of red-pine is harmful to crops standing thereunderl0> After Fleming's classical verification of exudations of Penicillium notatum affecting the neighboring living things, the interest of research was gradually extended over toward higher plants, rendering a fair series of the relevant findings. Such chemical influences of other plants was named allelopathy by Molisch3' . Bodes l' reported that absintin, a component of Artemisia absinthium, unfavorably affects Foeniculum vulgare, and Funke11 determined that only the plants that have resistivity can grow under Artemisia. In 1942, after actual observation on desert plants, Went13' came with the report that Encelia farinosa admits only limited kinds of plants in a natural re- pulsion against other plants. This was due substantiated by Gray and Bonnerl4'. They demonstrated that the leaves of Encelia contain a growth-inhibiting substance which reduces the growth of tomato plants in water culture. Later the toxic substance was identified as 3-acetyl-6-methoxy-benzaldehyde. Evenari15 "6), on the other hand, repeatedly reported on germination inhibitors, such as dinitrophenol, coumarin and 2, 4-D, against lettuce. Osvald's Agropyron repensl?', Brooks' Fuglaas nigra18' are the other examples of the issue. Further details should be referred in comprehensive work of Evenari4,15) , Grummerl9' and Winter20' . In 1963, Moore21' tested the germination of radish and lettuce in the extract of Cercocarpus montanus to find the inhibitors, while Torres, Koch and Katz21' detected a water diffusible germination inhibitor in the fruit wall of a desert perennial, Zinnia oligantha. To return to our subject, though there are not a few unsolved questions such as microbial changes of dew- or rain-washed red-pine tract in the soil, the physiolog- ical aspect of inhibiting actions in the seeds and plants, the chemical determination of the inhibitors, etc., the present authors think they could convincingly show by various experiments how the red-pine combines with a fixed number of species, or, conversely speaking, how the red-pine rejects a fair number of other species. The inhibitive effect of P. densiflora against other species is common to the leaf extract and root extract. There are no traces of autointoxication in the red-pine itself, and the species which have vitality 1 under the red-pine forest are not or only in a lower degree inhibited in their germination and growth. The inhibitive effect of the pine 412 Bot. Mag. Tokyo Vol. 76 remains in the soil under the forest against heavy washing by high precipitation and microbial decomposition in warm temperature, and enough works on the germination and growth of other low-vitality species to exclude many of them from the undergrowth of the forest, causing negative geotropism of the root. Thus could be concluded that here light or moisture condition is not a decisive factor in selection of the plant species constituting the undergrowth. To add, the authors could also confirm experimentally similar inhibiting effects on the germination and growth of weeds, Amaranthus, Chenopodium, etc., of the soils under Fagus, Abies and Quercus forests. This may suggest that the floristic composition of an association can sometimes highly depend on the chemical components of the dominant species.

Summary

1. High-vitality and high-frequency components of the undergrowth of red-pine forests, in which the cover degree of Pinus densiflora was higher than 4.5, were tabulated for the wide ranges of Japan (mainly according to Yoshiokas~) and South Korea (near Seoul). 2. Leaf extract and root extract of P. densiflora inhibited heavily the seed germination of weeds, e. g. Amaranthus and Achyranthes, which did not naturally grow in the red-pine forest. No inhibition was observed in Pinus seed. 3. Soils taken from the red-pine forests of various localities were detected inhibiting the growth of plants. Amaranthus, Achyranthes, Phytolacca, Chenopodiumr Setaria and Galinsoga, which rarely appeared in the red-pine forest with very low vitalities. The growth of high-vitality components, Pinus, Miscanthus, Atractylis and Paederia, was the same or slightly better on the red-pine-forest soils than on ordinary nursery soils. 4. The growth-inhibitive effect of Pinus extracts was demonstrated in low-vitality plants, Amaranthus, Achyranthes and Setaria, by planting on an artificial soil supplied with mineral nutrients. On the contrary, the high-vitality plants, Pinus and. Miscanthus, did not show any depression of their growth. 5. Negative geotropism was observed in the roots of Amaranthus seeds which were sprouted on filter paper wetted respectively by Pinus shoot extract, Quercus seed extract and tannic acid solution. 6. The chemical nature of the germination and growth inhibitors secreted by P. densiflora was preliminarily investigated. In the Pinus extract as well as in the red-pine-forest-soil extract, the fluorescence of p-coumaric acid-like substance was detected by paper-chromatography. 7. It was suggested that the floristic composition of a plant community may sometimes be decided by chemical influences on other species, allelopathy.

The authors should like to express their deepest gratitude to Profs. M. Shimo-- koriyama, K. Yoshioka, T. Satoo, and K. Minami, and Drs. S. Yoshida, H. Kanai, and T. Totsuka.

References

1) Knapp, R., Experimentelle Soziologie der hoheren Pflanzen. Eugen Ulmer Verlag, Stuttgart, (1954). 2) Bonner, J., Chemical sociology among the plants. Scientific American Ed., Plant Bot. Mag. Tokyo (November, 1963) Plate VI

A and B. Sprouting of Pinus densiflora (A) and of Amaranthus patulus (B) in red-pine- leaf extract. (1) Original solution; (2) 1/2 dilution; (3) 1/4 dilution; (4) pure water. At 25°. Pinus sproutings, 5 days old, showed no differences in germination and growth among the dishes. Amaranthus, 3 days after sowing, showed no germination in (1). C and D. Growth of Pinus densiflora (1) and Amaranthus patulus (2) in ordinary farm soil of Tokyo Univ. campus (C). In red-pine-forest soil of Abiko (D). Sown on July 24; photographed on Aug. 5. In a greenhouse. The growth of Pinus is rather better, where that of Amaranthus is worse. E. Growth of Amaranthus patulus in Abiko pine-forest soil (1) and Tokyo Univ. farm soil (2). Sown on April 14; sampled on Aug. 16. F. Desmodium fallax var. manshuricum seedlings. (1) Tokyo Univ. farm soil; (2) Abiko pine-forest soil. Sown on April 14; sampled on June 25. In a greenhouse.

LEE, I. K., and MONSI, M.: Ecological Studies on Pinus densiflora forest 1. Effects of Plant Substances on the Floristic Composition of the Undergrowth. '$ Plate VII ot. Mag. Toky o (November, 1963)

G. Seedlings of Atractylis ovata grown in Abiko soil (1) and Tokyo Univ. farm soil (2). Almost equal growth is seen. Sown on April 14; sampled on July 9. In a greenhouse. H. Growth of Achyranthes japonica in red-pine-forest soils of Abiko (1), Toride (2) and Mashiko (3) and in farm soil of Tokyo Univ. campus (4). Sown on May 23; sampled on July 12. In a greenhouse. I and J. Growth of Pinus densiflora (I) and of Chenopodium album (J) in red-pine-forest soils of Abiko (1), Toride (2), Mashiko (3), and Koginu (4), and in farm soil of Tokyo Univ. campus (5). Sown on May 14; photographed on June 25. The sprouting of Pinus in (5) was delayed for 3 days. The best growth of Chenopodium was observed in (5). K. Growth of Phytolacca americana in red-pine-forest soil of Abiko (1), Mashiko (2), and in farm soil of Tokyo Univ. campus (3). Sown on May 14; photographed on July 28. Mean air temperature, ca. 28°. L. Growth of Amaranthus patulus seedlings in vermiculite, an artificial soil. Seedlings were transplanted on June 18, 2 days after germination, and supplied with pure water (1), 1/2 dilution of pine-leaf extract (2), and the original solution (3). Photographed on Aug. 10. Mean air temperature, ca. 28°.

LEE, I. K., and MoNSI, M.: Ecological Studies on Pinus densiflora 1. Effects of Plant Sub- stances on the Floristic Composition of the Undergrowth. November, 1963 Lee, I. K., and MONSI, M. 413

Life, New York (1957). 3) Molisch, H., Der EinfluB einer Pflanze auf die andere. Allelopathie. Gustav Fischer, Jena (1937). 4) Evenari, M., Handbuch d. Pflanzenphysiol. 16: 691 Springer Verlag, Berlin (1961). 5) Braun-Blanquet, J., Pflanzensoziologie. 2 Aufl. 79, Springer Verlag, Wien (1951). 6) Yoshioka, K., Ecological studies on Japanese pine forests, Ringyo Gijutsu Kyokai, Tokyo (1958). 7) Hirao, N., Encyclopedia of chemical components of plants in Japan. Sasaki Book Co., 3 : 666. Tokyo (1956). 8) Thimann, K. V., and Bonner, W. D., Proc. Nat. Acad. Sci. U. S. 35: 272 (1949). 9) Miyazaki, S., Theses collection of the manage- ment of red-pine forests. 391, Jap. For. Soc. (1943). 10) Ota, S., Conservation of forest-lands, Chisan Konwa Kai, Sapporo (1961). 11) Bode, H. R., Planta 30: 567 (1940). 12) Funke, G. L., Blumea 5: 281 (1943). 13) Went, F. W., Bull. Torrey Bot. Club. 69: 100 (1942). 14) Gray, R., and Bonner, J., Amer. J. Bot. 35: 52 (1948). 15) Evenari, M., Bot. Rev. 15: 153 (1949). 16) Evenari, M., Symposia Soc. Exp. Biol. 11: 21 (1957). 17) Osvald, H., Vaxtodling 2: 288 (1947) (cited by Grummer, G., Symposia Soc. Exp. Biol. 15: 219 (1961)). 18) Brooks, M., West Verginia Agric. Exp. Sta. Bull No. 347 (1951) (cited by Grummer, G., Symposia Soc. Exp. Biol. 15: 219 (1961)). 19) Grummer, G., Symposia Soc. Exp. Biol. 15: 219 (1961). 20) Winter, A. G., ibid. 15: 229 (1961). 21) Moore, T. C., Ecol. 44: 406 (1963). 22) Torres, A. M., Koch, G. H., and Katz, M. W., ibid. 44: 414 (1963).

摘要

李一球*・門司正三**:アカマツ林の生態学的研究1.アカマツ林床群落の種類組成におよぼす植物成分の影響・

1.韓国(ソウル附近)と,北海道を除く日本各地域(おもに吉岡6)の表による)におけるアカマツ林 (アカマツ被度4.5以上)の下層植物 ¢)うち,高活力度,高頻度を示す植物の表をつくった(第1表). 2.アカマツ林下で活力度の弱いホソアオゲイトウ,イノコズチなどの種子に,アカマツの葉の浸出液を与えるとその発芽に著しい阻害作用がみられた. 3.アカマツ林下で高活力度を示すアカマツ,ヘクソカズラ,オケラ,ススキ,キキョウは,アカマツ林の土壌においてよく生育したが,活力度の弱いシラヤマギク,ホソアオゲイトウ,エノコログサ,イノコズチ,シロザ,ヤブハギ,ハナタデ,ヨウシュヤマゴボウ,ハキダメギクなどの生長は著しい阻害作用を受けた. 4.栄養塩類を加えた人工土にホソアオゲイトウ,ススキ,アカマツ,エノコログサ,イノコズチなどの幼苗を植えて,アカマツの葉の浸出液を与えて栽培した.アカマツ,ススキの生長には影響がみられないのに対して,ホソアオゲイトウ,エノコログサ,イ,ノコズチなどではその浸出液の濃度に応じて生長の差が見られた. 5.アカマツの葉条,コナラの種子などの浸出液とタソニソ酸溶液に対してホソアオゲイトウの発芽種子はエオシソ溶液の場合と同様に根の背地性を示した. 6.アカマツの分泌する阻害物質の化学的性質について多少,予備的実験をおこなった.マツの浸出液,マツ林の土壌浸出液中に阻害作用の知られているp一クマル酸様物質の存在がペーパークロマトグラフィによつて認められた. 7.植物群落の種類組成はときに,化学的影響(アレロパティー)により支配されうる可能性を提:示した.(*韓国慶煕大学校文理科大学生物学教室,東京大学理学部植物学教室**東京大学理学部植物学教室)