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(1)Hyogo University of Teacher Education Journal Vol. 9 , Ser. 3 , 101-109. 101. Photospectronic Properties of Micro Radiation Climates and. Their Modification by Plants Shigeaki ATSUMI and Takuzou YAMADA (Received September 30, 1988 ). Abstruct Photon flux densities (PFD) of incident light in forests of various vegetaion were measured from 400nm to 800nm wavelength at an interval of lnm. Proportions of PFDs of far red light (from 690nm to 760nm) to those of the measured wavelength range were found to increase in forests and even in the shade on the north side of forests. In open spaces or places without forest vegetations, ratio of PFDs of far red light (FR) to those of red light (R) were less than 1. In deciduous or evergree forests, photosynthetic photon flux densities were extremely low, but the ratio of FR to R reached to 3 t0 7. And the ratio of FR to R were in the levels of 1 in the shade on the north side of forests. Red light was absorbed or reflected by leaves but not a little of far red light were transmitted through leaves to the earth's surface.. Introduction. Many types of plant community are recognized in the actual vegetation of Japan. It is expected that the actual vegetation succeed to the potential natural vegetation if any human interfernce are to be removed. And also, changes of the human interference in qualities or quantities bring about succession on the a-. ctual vegetation (Miyawah et al, 1978). Most of forests in Yahiro-chou Town (Hyogo Pref. ) and surrounding regions can be classiffied into the secondary forest referred to Pinus densiflora plantation and deciduous Quercus forest. They, however, might be not in the stationary stages, because members of evergreen broad-leaved species, such as Castanopsis cuspidata Schottky, Tutcheria virgata Nakai, Camellia japonica L. and so on, are in them (unpublished data). In other words, succession from the secondary forest to evergreen bload-leaved forests as the potential natural vegetation is in progress. Evoking altarations in soil, water in soil and atmosphere, temperature, radiation as the source of energy and so on, competitions in plant communities have been supposed to to be the driving factor of the succession of forests (Clements, 1916). The first step of the succession, however are addition of new members to plant communities, that is, germination of seeds of which have not yet been a. ホBiological. institute,. Hyogo. University. of. Teacher. Education,. Hyogo. 673-14,. Japan.. Abbreviations : FR, far red light ; PFD, photon flux density ; PPFD, photosynthetic photon flux density; R, red light..

(2) 102 species of the forests. Therfore, the factors enumerated above are rather factors to act on the growth of plants which have already existed. Seed germination is mainly controlled by temperature, humidity and soil, and some plant species have been found to require lights, especially red light (R) in their seed germination. These phenomena are named light germination (FrannAND and Taylorson, 1983). In this study, micro radiation climates, which are one the factors driving the succession through limitation on the germination in fields, have been examined in Yashir0-chou Town and her surouding regions.. Experimentals Radiometory Incident light at forest floor was measured with a portable spectroradiometer LI-1800 (Li-Car, Nebraska, USA) equipped with a cosine photo receptor. After horizontally placing the meter, radiation spectrum from 400nm to 800nm were measured three times or five times at an interval of lnm wavelength, and measured values were automatically converted to mean values at each wavelength. Each measurement was carried out between eleven in the morning and two in the afternoon in a day of fine weather, except some measurements with special purposes. Obtained radiation spectrograph were ploted in photon flux density (PFD, 〃mol sec. '・m. 2). against. wavelength. (nm).. When. the. sun. was. concealed. behind. clouds. during a measuement the measurement was halted at once and the data were rejected. Experimental sites Radiation climates were measured principally in Yashiro-chou Town in Hyogo Pref. and in her surrouding regions. To estimate differences in radiation Climates in pine forests with or without human disturbance, several observation sites were provided in an experimental forest in Kasai city of Forest Research Center of Hyogo Pref. Among deciduous Quercus forests, a forest of Quercetum acutissimoserratae association (Okegawa city, Saitama Pref. ) and a forest of Q.serrat0grosseserratae association (contiguous to Choukouji Temple, Yashiro-chou) were examined. Evergreen Quercus forests were located in the precints of Choukoji Temple. A bush of Robinia pseudoacacia L. and a forest of juvenile P. densiflora were located in the campus of Hyogo Univ. Teacher Education. A forest of bam-. boo (第秒Ilostachys nigra Munro var. henonis Nakai) was contiguous to Choukouji Temple. The actual vegetation of the experimental sites were classified according to. Miyawaki's classification system (Miyawaki, 1978).. Results and discussion Solar radiation spectrum at open spaces Incident light in the sunshine is composed of the direct radiation from the sun and of the skylight. On the other hand, the incident light in the shade of build-.

(3) Micro Radiation Climates Modified by Plants. 103. ings is composed only of the skylight. Radiation spectra in the shade on the north side of buildings, however, were almost similar to that in the sunshin (Fig. 1).. j t r > c o ( N J O √ u j o a s │ O ∈ r i ) X ⊃ I d N O . ト O H d. Fig. 1. Radiation spectra measured in the sunshine and the shade. Spectrum A measured at a grassy open space indicates a sum of the direct sunlight and the skylight, and B measured in the shade of a building indicates scattering- light from the blue sky. The spectra were measured in april 8 1987, in the campus of Hyogo Univ. Teacher Education.. 500. 600. 700 α). WAVELENGTH Inml. The absorption bands known as the Fraunhofer lines can be observed in the spectra of the sun light and the skylight. They are due to monoatomic gases in the sun's atmosphere (430nm (G), 466nm (d), 486 (F), 516nm-518nm (b), 526nm (E2), 587 nm-589nm (D), and 656nm (C)) and diatomic oxygen in the earth's atmosphere (759nm-762nm (A), 686nm-688nm (B) and 627nm-628nm (alpha), absorption bands D and b could not be resoluted). Although photosynthetic photon flux densities (PPFD) in the shade were less than a half of that in the sunshine, ratio of the. Table 1. Photon flux densities in the sunshine and in the shade of buildings and evergreen Quercus forest. Observation Site Photosynthetic Photon Flux Density6 Photon. Flux. (ォmol・sec. '・:. Densities (〝mol Open space Sunshine Shade of building Sunshine in the morning at noon. Far Red/Red Photon Flux Density Ratio. 'Red. Far. Red. 1.00×103. 0.263×103. 0.255×103 0.97. 0.411×103. 0.103×103. 0.986×10! 0.96. 0.421×103. 0.117×103. 0.117×103 1.00. 1.18×103. 0.337×103. 0.320×103 0.95. 0.653×102. 0.164×102. 0.187×10! 1.14. 0.645×102. 0.139×102. 0.199×102 1.44. Shade of forest" in the morning at noon. a. b. c. d.. In the campus of Hyogo Univ. Teacher Educ. In the precinct of Choukouji Temple. Between 7:00 and 8:00 am. Between 13:00 and 14:00.. e. Red and far red regions are ranging form 620nm to 690nm and from 690nm to 760nm, respectively..

(4) 104. ー. o. ・ -. 糾.  ̄. ・uu,.3as│0∈rt│X⊃ft)NOIO正. (ui-pss-ioiuri)×rrunoトOHd. o. 2 〇. ム50 500 550 600 650 700 750. WAVELENGTH (nm]. Fig. 2. Incident light spectra at the northern verge of a evergreen Quercus (Ardisio-Castanopsietum siebolddi association) forest of Chokouji Temp. Spectrum A was obtained in a grassy place in the sunshine and B in the north shade of the forest. The solid lines are spectra measured between 7:00 to 8:00 am and the broken lines between 1:00 and 2:00 pm in September 18, 1988.. 650 500 550 600 650 700 750 WAVELENGTH nml. Fig. 3. Incident light spectra at various observation sites in a experimental pine forest in Kasai City. The upper two spectra (A and B) were obtained in a well-kept pine (P. densiflora Sieb. ) plantation of the forest. The lower two (C and D) were obtained in the forest left as it w早s for several years and invaded by R. reticulatum D. Doni and Ilex and Quercus species. Data were obtained in September 21, 1988.. amounts of far red light (FR, ranging in wavelength from 690nm to 760nm) to those of red light (R, from 620nm to 690nm) (hereinafter referred as 'ratio of. FR to R'or 'FR/現ratio') in the shade was pra ctically the same in the sunshin (Table 1), and the ratio was always less than 1.00 even in the shade of buildings.. Radiation spectra in the north shade of the evergreen Quercus forest. Contrasting with the shade of buildings, the solar radiation spectra were steeply modified in the shade on the north side of the evergreen Quercus forest (Fig. 2). PFDs between 650nm and 700nm were obviously decreased to a larger extent than those above 700nm. Although in the shade of building a major portion of the incident light is the skylight, in the shade of forests the transmitted light through leaves is added to the skylight from the open canopy. Therefore, PFDs between 520nm and 600nm and above 700nm are increased to some extent in the shade of forests. Ratio of FR/R, therefore, exceeded 100 in contrast with that in the shade of buildings (Table 1). In such a shade on the north side of forests, poor mantle communities were found、 Pine forests. In a well-kept puer pine forest, where the undergrowth has been cleared off, PFDs between 400nm and 700nm wavelength were decreased intensely more than those above 700nm. But still more decreases between 400nm and 700nm were ob served in the radiation spectra of pine forests left as it is (Fig. 3). The ratio of.

(5) Micro Radiation Climates Modified by Plants. 105. Table 2. Photon flux densities of red and far red regions in pine forests. Observation site. Photosynthetic Photon Flux Density Photon Flux (umol sec 'm !) Densities (umol secー1 m"2) Red Far Red. Far Red/Red Photon Flux Density Ratio. Pinus densiflora plantation juvenile forest matured forest. 0.190×103. 0.510×102. 0.682×102. 1.33. 0.929×102. 0.245×102. 0.328×102. 1.34. mixed forest. 0.980× 100. 0.980×100. 0.167×101. 1.70. Pure pine forest in fine weather. 0.694× 102. 0.177×102. 0.207×102. 1.17. 0.225×102. 0.592×101. 0.676×101. 1.14. 0.810×101. 0.200× 101. 0.781×100. 3.90. 0.157×101. 0.418×100. 0.919×100. 2.20. in rainy weather Mixed pine forset in fine weather in rainy weather. The height of pine trees of the juvenile forest were less than 2.5m, and that of the matured forest was more than 5m. The `pure means that a forest were wellkept without undergrowth, and the `mixed means a forest left as it is with well grown undergrowth. a. In the campus of Hyogo Univ. Teacher Educ. b. In the experimental forest of Forest Research Center of Hyogo Pref. c. Refer to Tab!0 1.. Table 3. Photon flux densities of red and far red regions at various vegetation. Observation Site. Photosynthetic Photon Flux Density Photon. Flux. (umol・sec. '・m. 2). Densities (〃mol・sec ̄l. Far Red/Red Photon Flux Density Ratio. -m-2). Red. Far. Red. Evergreen Quercus forest 0.107×102. 0.261×10'0.959×101. Deciduous Quercus forest 0.140× 102. 0.303×101 0.155×102. Deciduous Quercus forest foliated. 0.410× 10'0.196× 102. defoliated. 0.172× 103 0.179× 103. Robinia pseudoacacia bush 0.198× 10'0.462× 10'0.316× 102 Bamboo forest" 0.441× 10'0.109× 101 0.510× 101. a. In the precinct of Choukouji Temple. b. In adjacent forests to Choukouji Temple. C. In a forest in Okegawa city. d. In the campus of Hyogo Univ. Teacher Educ. e. Refer to Table 1.. FR to R in the pine forest with the well grown undergrowth were approximatetely two to three times of those in the well-kept pine forest. Many sprouts of pine and other plats were found on the forest floors of the wellkept pine forests, where 50 /zmol・sec. '・m. of. PPFDs. were. enought. to. support. the. growth. of. the. sprouts.. PPFDs, however, decreased with progress of the forest maturation and the growth.

(6) 106. 0-. (..UuiP6S-│0∈ユ)x⊃IdNOIOHd. 650 500 550 600 650 700 750 WAVELENGTH (nm. Fig. 4. (a) Incident light苧pectra of a P. densiflora pure forest, (b) Incident light of a Rhododendro reticulati-Pinetum densiflora forest. Locality of the measurements was the same in Fig.3. Spectrum A and B in each figure,were measured in fine weather (September 21, 1988) and in rain (September 20, 19888) respectively.. Fig. 5. Incident light spectra of a deciduous Quercus forest (Quercetum acutissimo serratae association) in Okegawa City in defoliated and foliated periods. C: defoliation (March 30, 1987), D: foliation (June 12, 1987). Spectra A and B were measured in a plowed field on the east of the forest for the comparizon with C and D, respectively.. 400 500 600 咲) ㈱VELENGTH nm) of invasive species (Table 2). Althogh in rainy weather the radiation spectra showed to be the same in enssence with those in fine weather, the rainy weather decreased PFDs between 520nm and 650nm, and above 700nm (fig. 4). Because of relative increase in PFDs between 650nm and 700nm, the ratio of FR to R decreased (Table 2). These modification in radiation spectra should be attributed to scattering the sunlight by clouds. Radiation spectra in several types of forests Deciduous Quercus forests of Quercetum acutissimo-serratae association are the most common secondary forest in the Kanto plains. Radiation spectra in a forest of this type are shown in Fig.5. In foliation the solar radiation below 700nm.

(7) Micro Radiation Climates Modified by Plants. 1∞ 500 600 700 WAVELENGTH ran). 500 600 700 WAVELENGTH (nm). Fig. 6. The radiation spectra in several vegetation observed in the forests around Choukouji Temple. Solid line: deciduous Quercus forest Quercentum serrat0-grosseserratae association). Dash-dot-dash line: evergreen. C0 T>0 U3CO 0 (j.UJ;?3S-│O∈rL)×mLNOトOHd. 551. do -tu,pss.)oErl)xmdNOIOHd. 00. 107. Fig. 7. Incident light spectra in two anthropogenic plant communities. Solid line: Robinia pseudoacacia bush in the campus of Hyogo Umv. Teacher Education. Broken line: bamboo (P. nigra) forest near Choukouji temple.. Quercus forest (Ardisio-Castanopsiet?m sieboldii association). Broken line: pine forest (.Rhododendro reticulati - Pinetum densiflorae association).. wavelength was almost completely absorbed or reflected by leaves. And the ratio of RF to R reached to 4.79. In defoliation, properly, the, ratio was 1.04 (Tavle. 3) about as low as that in the shadeon the north side of evergreen forests (Table 1). Although there were no leaves on the trees in defoliation, PFDs in the forest decreased nearly by a half of that successively measured in plowed field at each wavelenghth (Fig. 5). This lowered PFDs in defoliation might be due to the scattering by the nake branches.. An another type of deciduous Quercus forest, which is classified into Q. serrat0grosseserratae association, is a familiar type of secondary forests in the Kansai and Chuugoku distincts. And the observed modification on the radiation spectrum in the forest was almost the same in the Kanto plains (Fig. 6). Plantlets of P.densiflora and other herbs as the undergrowth were not found on the forest floors of both the deciduous Quercus forests. In the evergreen Quercus forest, on the other hand, PFDs above 690nm were almost a half of that in deciduous Quercus forest (Fig. 6 and Table 3). Because PFDs below 690nm were slightly lower than those of the deciduous Quercus forest, ratio of FR to R in the evergreen Quercus forest was 66% of that in the deciduous Quercus forest. Thick and dark green leaves of evergreen Quercus might absorb the radiation above 690nm wavelength more efficienly than deciduous leaves do. Therefore in the sense of the human sight it might be darker in the. evergreen Qurcus forest than in the deciduous Quercus forest, in spit of almost the same PPFDs of both the forest..

(8) 108 High ratio of RF to R was also observed in the deciduous bush of R. pseudoacacia (Fig. 7). In this bush population of Solidago altissima L. as the undergrowth was found to be extremely few, and there were not any seedlings. Bamboo forest also showed to have a high ratio of FR to R (Table 3). The decrease in PPFDs and the increase in FR/Tl ratio might continue, for the prgress of forestmaturation, i.e. growth of trees. There is also decrease in the population of sprouts. The ratio of FR/R higher than 2 is seemed to Suppress the germination of sporuts. (Table 2 and 3), because the low PPFDs should become fatal to plantlets after germination. After P. densiflora, deciduous trees, or evergreen trees have coverd the canopy, any seeds have not a chance to germinate. Ration of FR/R regulates the germination. Promotive effect of red light on germination has been pronouced (precisely reviewed by Frankland & Taylorson 1983). It should be also emphasized that radiation with high FR/R ratio had an inhibitory effect on germination, and far red light might be the basis of the inhibitory effect. Seeds spreaded on the surface of the earth receive the information of the canopy in the form of radiation spectra.. Refert)nces ( 1 ) Clements F. E. (1926) plant Succession. Carnegie Inst. , Publ. , Washington. (2) Frankland B. and Taylorson G. (1983) Light control of seed germination. In Encylopedia of plant Physiology, New Series, Edited by A. Pirson and M.H. Zimmermann, Vol. 16A, pp. 428-456. Springer-Verlag, Berlin. (3) Miyawaki, A., Okuda S. and Mochizuki R. (1978) Handbook of Japanese Vegetaion, Edited by Kitagawa M. Shibundo Co. , Ltd. Publ. , Tokyo..

(9) Micro Radiation Climates Modified by Plants. iOB. 光スペクトルの微環境とその植物による修飾. 渥美茂明・山田卓三 (1988年9月30日受理) さまざまな植生の森林の林床面における400nmから800nmの入射光量子密度(PFD : photon flux density )のスペクトルを測定した。林の中、あるいは森林の北面にできる 日陰では、測定波長範囲の総光量子数に対して遠赤色光は比較的大きな割合で存在するこ とが示された。また、開けた場所、あるいは無植被地では遠赤色光域と赤色光域のPFD 比は1以下であった。一方落莫樹林や常緑樹林では、光合成に関与する波長域の光量子密 皮(PPFD : photosynthetic photon flux density)は森林外に比べ低かったが、遠赤 色光域と赤色光域のPFD比は逆に増加し3ないし7程度であった。葉によって赤色光は 高率で吸収あるいは反射されるが、遠赤色光は相対的によく葉を透過し林床面に到達する のが観察された。樹冠が発達した森林では林床面に芽生えを見ることはまれであるが、こ れは林床面に到達する遠赤色光が発芽を阻害しているためであると考えられる。.

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Table 2. Photon flux densities of red and far red regions in pine forests Observation site Photosynthetic Photon Flux Density Photon Flux (umol sec 'm !) Densities (umol secー1 m"2) Red Far Red Far Red/RedPhoton FluxDensity Ratio Pinus densiflora planta

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