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The EcologicalSocietyEcological Society ofJapanof Japan Vol. 23, No. 4 JAPANESEJOURNAL OFECOLOGY Aug.,1973 HISTORICAL AND ECOLOGICAL STUDIES OF ABIES IILIRIESll' ON MT. GASSAN, THE DEWA MOUNTAINS, NORTHEAST JAPAN Mitsuo YAMANAKA, Kazuo SAITO and Kazuo IsHlzuKA Mt. Hltk:L]acla Bbtanical Labomtoisl IShoku University and Flicttlly ofGeneml Elarucation, lhmcrgata University Synopsis YAMANAKA, Mitsuo,' KazuoSAIT6" and Kazuo IsHIzuKA"" (Mt. Hakk6da Botanical Laboratory, Faculty of Science, T6hoku University' and Faculty of General Education, Yamagata University" ) Historical and ecological $tudies of Abies mariesii on Mt. Gassan, the Dewa Mountains, northeast Japan. Jap. J. Ecol. 23, 171-185 (1973) The subalpine vegetation in north Honshu shows a sharp contrast in physiognomy. Abies mariesi'i and 71izrga diversijblia ar'e well established in the inland subalpine region whiJe scarcely in the Japan Sea area. On Mt, Gassan in the Dewa mountains, Abies maiiesii occurs sporadi- cally on a lava plateau situated on the leeward side of the mountain and screeneq from the strong westerlies or northwesterlies in winter, It was revealed by the pollen-analytical study aimed to elucidate the vegetation history of this mountain that the subalpine conifers had been mere extensive here under the Late Pleistocene climate but retreated under the more recent conditions of heavy snowiall and strong wind. The present occurrence of Abies is, therefore, thought to be a relict of the Late Pleistocene. Further investigations were made on the floristic composition of the Abies habitat, the community structure, the dynamics of the Abies population, the growth form and the seil pro- file of its habitat. The physiognorny of the Abies community is, as a whole. that of the mixed thicket of Abies and deciduous broad-leaved chrubs, covering the wet alpine pod$ol on the ill-drained flats. The stems grow so high on the well-drained soil as to be ifljured or de- formed serieusly by the heavy snow cover and strong wind, so that they can hardly survive there. The wet alpine pedsol is probabiy of gtreat advantage to the Abies survival because of the stunted form that prevents suffering from the effect of snow and wind. The subalpine vegetation in north Honshu is (Mt. Hayachine), while it is scarcely found on rnarkedly modified by the climatic condition in the mountains of the Japan Sea area(Mts.Iide, winter and provides a sharp contrast in physi- Asahi, Gassan, Chokai, Iwaki etc.). This is ognomy. The ciimate of the JaPan Sea area is also true in the central portion of the Ou characterized by the strong westerlies or Mountains (Mts. Akita-koma, Yakeishi, Kuri- northwesterlies and heavy snowfall in winter, koma, Fupagata, etc.) that is not screened whereas that of the inland area is moderate. from the westerlies by the higl) mount'ain of The subalpine coniferous forest of Abies the Japan Sea side. The subalpine region there mariesii and Il;trga diversijblia is well estab- is occupied mainiy by the deciduous broad- lished both in the north and south of the Ou leaved scrub of (?tterczas mo?rgolica var. undtt- Mountains (Mts, Hakk6da, Hachimantai, Zao latijblin, Alnzas maximowic2ir; Acer tschonaskii and Azuma) and in the Kitakami Mountains etc., the dwarf bamboo scrub of dma kurilensts and the various types of snow-bed vegetation Received Oct. 16, 1973 <SuzuKI et al. 1956, MIyAwAKI et al. 1969, work was supported by in This partly the Grant "the IsHIzuKAet al. 1972> and is called Aid for Scientific Research by the Ministry quasi-a]pine of Education defrayed to K. Ishizuka. zone" by SHIDEI(1952). The subalpine conifers 171 NII-Electronic Library Service The EcologicalSocietyEcological Society of Japan Vol. ea, No.4 H4 th re \A su, Aug., 1973 occur sporadicaily on some of these mountains, viz,, Abies mariesii en Mts. Gassan and Kurikoma, and 71ls;trga diversifolla on Mts. Iide, Iwaki and Yakeishi. On the other hand, the recent poilen-analytical studies (HIBINo 1969 and 1970,YAMANAKA 1969) have revealed the more extensive occurrence of Abies, 71strga, ICicea and Beimla during the Late Pleistocene epoch even in the Japan Sea area. These ieatures suggest that the current ciimate of the strong wind and heavy snowfall in winter, together with the long duration of snow cover until late spring or early sumrner, i exerts detrimental effects on the growth and establishment of the subalpine copifers in the km Japan Sea area. Mom is the first to have reported on (1969> Fig. 1. Map showing the situation of the repre- the present occurrence of Abies mariesii on sentative mountains in nomh Honshu Mt. Gassan although without phytosociological in winter 1). and ecological descriptions. Some efforts Japan (Fig. Topographically, Mt. Gassan appears to be (IsHIZUKA 1972, SAIT6 1972) were made prelimi･ a on all escarp'- narilytodescribe its ecological features. The shield volcano truneated sides by ments or steep slopes 2). main ridge present paper is concetned with the further <Fig, The investigations aimed to elucidate the vegeta- extends in a north-south directionat the of mourrtain. and tion history, especial;y the deterioration western part the On the east north sides, slopes of extend process of the subalpine conifers with special gentle lavaflows main ridge, until reference to the climatic change after the Late from the they are cut off by a Pleistocene on Mt.Gassan and to search for series of escarpments at altitudes between the cause and manner in which Abies mariesii 1500mand1300m Two flats called Midaga- survives here. hara and Tsukimigahara are formed at the The field work was done in the summers northern and eastern ends of the lava slopes. At the west, ridge of 1970 to 1972 with the kind help of the the main continues to the members of the Nature Conservation Society steep slopes descendingdownward to 1200 to 13oe rn. of the Dewa Mountains, to whom the writers The climate is characterized, as usual in the are greatly indebted. Cerdial thanks are due to moufitains near the Professor Jun NAKAMuRA of the･K6chi Universi- Japan Sea coast, by the snowfall and strong northwesterlies ty for his valuable advice on the polien-ana- heavy in 1ytical study. winter. Their combined effects results in the heavy accumulation of snow on the east or southeast slopes and escarpments. Area Studied Mt. Gassan is an extinct volcano located at The vegetation of Mt. Gassan was already almost the center of Yarnagata Prefecture and described by SuzuKi et al. (1956). The Fbgzcs rises to a･height of 1980m above Erea level, crenuta forest is well established as the climatic climax montane facing the northwest winds from the Sea of in the zone, and h,･ 172 NII-Electronic Library Service The EcologicalSocietyEcological Society of Japan Vol. as, No. 4 JAPANESE JOVRNAL OF ECOLOGY Aug., lg73 't4ilsua,g･ew )s '\ke'ng'a'nf}'h'd""'!'" edge of the escarpment and at the tops of the .?f XN low folds of lava-land-formation. a' IE,:SliL pt.i ;{!%t M The thick snow cover on the eastern slopes tsvangNz2%'$ )'!,{sr,;6{::;iig,.,..IIilEtsiW of the mountain remains until summer or ' z often until late autumn. It brings about the ± ･' X,K.,-, eeSfiKva %,lliiklpreponderance of the snow･bed vegetation in Sl ,.. zztue the plant cover. gewl\r).･The subalpine deciduous scrubs and the Eiasa zl tsB--es# ee'.i.li.i,,. Ival' scrub are restricted to the ridges and the edge yZ. area of the fiats or slopes, where the duration XJ sk, /-llitflS:i.riuY'r.l'E.-･;'" =iptt[t of snow cover is relatively short. The habitat XNJi.t-,"･'r'trvrv-.r6,of Abibs mahesii in Fig. 2 is in the area of ･ as relatively ･ Xpt`--x",.Tsu.kemiga>llz..early snow melt. Abies martesii is here associated with the decidnous shrubs and Sczsa leurilensis. It is to be noted that this habitat is also protected agaist the strong affects of the northwesterlies /S in winter. other hand, moors of various types y/i//tes.x'"' On the lkand sizes are found in and around Mt. Gassan. eessximegss rmwag4$eg".\eqtm,# Arnong them, the Nembutsugahara moor is glQ most suitable for the po11en-analytical study Ng. 2, ssTopographic rnap of the nomh of Mt, part Gassan. Contours at intervals of 20m, since its peat deposit is thickest. It is develop- 'Ihe stippled area indicates the distrjbntion of ed on a granite plateau of the Cretaceous to Ables tnatiesii, and the line.A-B the site of the Early Tertiary age. It is located ca. 6km east transect belt of the smmit of the mountain and ca. 6.5km extends up to 120e to 14oom in altitude. southeast of the Abies habitat, at an altitude of There it reaclies the forest limit in a peculiar about llOOm. The volcanic ejecta repeatedly form of dwarfed, dense forest. The subalpine accumulated as to form thick impermeable zone is presumed to occupy the area from the horizons in the soil. forest lirnit to the altitude of 1700rn or so, The ridges and slopes surrounding the rnoor Fagtes forest and is mainly cevered by the subalpine broad- are covered by the c7ienate leaved scrub, the 5kzsa han'lensis scrub and the admixed with Pinus parvptom var. pantaptrylla. snow-bed vegetation. The alpine zone is the The flat around the moor is occupied by the area above 1700rn or so and is characterized scrubs dominated by Qnerctts mongolica by the ericaceous dwarf scrub. var. esnd"latt;foha associated with Alnzas The existent growths of Abibs mariasii are matsttmurae, ILex strgerold var. bem'pandun- plotted in Fig. 2 by the field ebservation and culala, HZz,namelis iciponica var. obtzcsala, the interpretation of air-photos. The main SmpPloeas chinensis f.

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