6.2. ecological distribution of seven evergreen …ito/esc/6-2.pdf6.2. ecological distribution of...

6.2. Ecological distribution of seven evergreen Quercus species in southern/eastern Kyushu

Satoshi Ito1, Kumiko Ohtsuka1 and Toshiyuki Yamashita2

1 Faculty of Agriculture, Miyazaki University, Miyazaki 889-2192, Japan2 Botanic Gardens of Toyama, Fuchu-machi, Nei-gun, Toyama 939-2713, Japan

Abstract　We investigated ecological distribution of seven evergreen Quercus species in southern and western Kyushu, Japan, onthe basis of analyses of previously reported vegetation data. An analysis along the elevation gradient, together with acluster analysis of species correlation, revealed two major distribution types of the species: Q. acuta, Q. salicina, Q.myrsinaefolia and Q. sessilifolia as a high-elevation type, and Q. gilva, Q. glauca and Q. hondae as a low-elevation type.Q. acuta had the highest elevation range of its distribution, and Q. hondae had the lowest range among the species. Q.acuta also showed preference on upper parts of slopes according to χ2 test between topographic units. In contrast, Q.sessilifolia, Q. gilva and Q.hondae had biased occurrence on the lower slopes. Occurrence of Q. sessilifolia was particularlyrestricted on lower slopes in the lower elevation range (<400m), suggesting its characteristics as a riparian component inthe lowland region. Q. salicina had the highest frequency and less site preference for their occurrence and dominance interms of both elevation and topography, indicating its characteristics as a typical generalist. Q. glauca had no topographypreference, and formed a same cluster with pioneer and/or deciduous species. This suggested the early-seral characteristicsor the disturbance-dependence of this species.Key words: elevation, evergreen broad-leaved forests, topography, Quercus, species correlation

Introduction

Genus Quercus widely distribute in temperate forestsin Japan. Of the Quercus species, a subgenusCycrobalanopsis, which is a group of evergreen oakspecies, is one of the major components of evergreenbroadleaved forests in a warm-temperate region ofsouthwestern Japan (Murata 1977, Okamoto 1979) , andoften used in the name of phytosociological units of theregion (e.g., Miyawaki 1978; 1981). Thus, comparativeexplanations of the ecological distribution and habitatsof these species may be greatly helpful for expandingphytosociological understandings of the evergreenbroadleaved forest communities of the region, in additionto clarifying the species characteristics and intra-subgenusrelationships of the species. Major previous studies of the ecological distributionsof Cycrobalanopsis have been done as qualitativedescription for each species, or with reference tophytosociology. Information based on quantitativecomparisons between species is less available.Quantitative analyses of the ecological distribution wouldprovide useful information for conservation aspect suchas estimation of potential habitats or prediction ofvegetation dynamics in relation to the climates changes. It is imperative to analyze species distribution withcombination of different scales and factors: coarse andregional scale factors affecting at elevation or climatelevels, and fine scale factors such as topography or site

conditions (cf. Kikuchi 2001). We focused on the southernand eastern regions of Kyushu surrounding MiyazakiPrefecture, where the most species rich forests werereported (Hattori et al. 2001). We aimed to describe theecological distribution of seven Cycrobalanopsis species(Quercus acuta, Q. gilva, Q. glauca, Q. hondae, Q.myrsinaefolia, Q. salicina and Q. sessilifolia) throughquantitative comparisons in relation to elevation gradientand topography.

Methods

1. Dataset Vegetation inventory data published by the JapaneseMinistry of Environment (Ministry of Environment 1980,1988a, 1988b) for southern and eastern Kyushu（Kumamoto Pref., Ohita, Pref., Miyazaki Pref. and

Kagoshima Pref.）was used in this study. This regioncorresponds to the distribution of Q. hondae, the rarestspecies in the seven evergreen Quercus species in Japan,reported in the past inventories by the government. From this inventory data, 209 stands where at least oneof seven Quercus species occurred in the tree layer or thesub-tree layer were selected for the analysis. Of the 255species appeared in the tree layer or the sub-tree layer inthe 209 stands, 101 species which occurred in more than5 stands were listed with their coverage class (c.f., Braun-Blanquet 1964) for each layer. The coverage class in thetwo layers were converted into percentage cover as:

基盤研究(B)(2):森林の潜在的生産力と撹乱体制を考慮した生態的ゾーニング手法の開発 (課題番号：14360090)

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“coverage class 5”=87.5%, “4”=67.5%, “3”=32.5%,“2”=17.5%, “1”=5.0% and “+”=0.5%, and summed foreach species to have one dominance value in each stand.Then, a relative dominance for each species wascalculated by dividing by the total dominance value forall species in each stand. Consequently, a matrix of relativedominance of 101 species for 209 stands was used forthe analysis. Stands attributes such as elevation, topography, andlocation of the selected 209 stands described in theinventory data sheets were also listed. As the originaldescription of topography varied in detail, we classifiedthese descriptions into following four simple categories:upper slopes, mid slopes, lower slopes and plains.

2. Data analysis For all 208 stands (excluding 1 stand which lackedelevation data in the original data sheet), and for sevensets of stands where each species occurred, stands weresorted by their elevation. The cumulative number of standsand cumulative relative dominance of each species werecalculated from lower elevation. Then, the elevation at

25, 50 and 75 percentiles of two cumulative values werelisted for each stand set to examine the distribution traitof each species along the elevation gradient. In order to examine the preference of each species tospecific topography, we applied the ?2 test to the numberof stands of each topographic category. Ten stands whichlacked description of topography in the original data wereexcluded from the analysis. Expected values of thenumber of stands for each topographic category werecalculated on the assumption that, for every species, ratioof stands on a topographic category was same to thatwithin the 199 sample stands. The ?2 test was appliedeach of seven stand sets, except for the case where thetopographic category had an expected value less than 5. Species correlation in terms of occurrence similarity wasexamined by cluster analysis using full matrix of 209stands. Species were classified by group average methodwith relative Euclidian distance used as dissimilarity.Stand type classification was also achieved by usingTWINSPAN with the same dataset. The cluster analysisand TWINSPAN were made by using PC-ORD Version4 (McCune and Mefford, 1999), a personal computer-

6.2. 九州東・南部における常緑カシの生態分布

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based software package.

Results

1. Regional distribution Fig. 1 shows the distribution map of seven Quercusspecies in for prefecture in the southern and easternKyushu. Every species showed different distribution trait.Q. salicina had wider range of distribution with thehighest frequency. Q. acuta and Q. glauca also had widerrange of distribution, but Q. glauca showed occurrenceslightly biased to the coastal region. Q. gilva, Q. hondaeand Q. sessilifolia mainly occurred in southern and easternpart of the target region. Particularly, distribution of Q.hondae was mostly restricted in the east coast of Kyushu.Q. myrsinaefolia showed their distribution biased to theinland region among the seven species.

2. Distribution along the elevation gradient Analysis along the elevation gradient demonstrated Q.acuta to have the highest elevation range of distribution(Fig. 2, Table 1). The 50-percentiles for the cumulativeoccurrence and the cumulative dominance of Q. acuta

were 750m a.s.l. and 780m, respectively. The 25-percentiles were 540m and 630m, respectively. Thesevalues were far higher than the averages (values forpooling seven species) of 50- percentiles (390m and380m, respectively). Q. salicina had similar range ofelevation to that of Q. acuta (45 – 1120m), but showedhigh dominance at lower elevation (Fig. 2). This resultedin relatively lower value of dominance percentiles (390m,520m and 690m for 25-, 50- and 75-percentile,respectively), which were 200m to 300m lower than thoseof Q. acuta (Table 1). Q. myrsinaefolia and Q. sessilifolia followed the formertwo species in terms of the elevation order. Q.myrsinaefolia and Q. sessilifolia had quite similardistribution (Fig.2), where 25- and 75 percentiles were260-270m and 560m for occurrence, respectively, and270m and 610m for dominance, respectively (Table 1).However, as Q. sessilifolia occurred with high dominancein several stands at low elevation, the 50-percentile ofthis species for dominance was lower (440m) than thatof Q. myrsinaefolia (560m). The elevation of the stand with occurrence of Q. gilva,Q. glauca and Q. hondae biased to lower elevation

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Fig. 2. Relative dominance of seven evergreen Quercus species along the elevation gradient in southern/eastern Kyushu based on 209 stands. The stands where the target species did not occur were not plotted.

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Fig. 2. Relative dominance of seven evergreen Quercus species along the elevation gradient in southern/eastern Kyushu based on 209 stands. The stands where the target species did not occur were not plotted.


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compared with the other four species (Fig.2). Particularly,occurrence of Q. hondae was mostly restricted to less than400m. Most distribution of these three species wasobserved in the range less than 500m, with the centralelevation (50-percentiles) less than 300m (Table 1). The50-percentiles of Q. hondae were extremely low amongthe seven species (160m and 115m for occurrence anddominance, respectively).

3. Topographic distribution Table 2 shows the summary of ÷2 analysis for occurrenceof the seven Quercus species with the four topographiccategories in the 199stands. The analysis demonstratedthe biased occurrence on different topography for Q.acuta, Q. sessilifolia, Q. gilva and Q. hondae (p<0.05).Q. acuta mostly occurred on upper slopes, and was lessobserved on lower slopes (Fig. 3). In contrast, Q.sessilifolia, Q. gilva and Q. hondae were mainly foundon lower slopes (Fig. 3). As shown in Fig. 2 and Table 1, differences in occurrence

and dominance between species were apparent with thethreshold of ca. 400m a.s.l., which corresponded to themedian value of elevation of all 199 stands. We also foundthe difference in proportion of stand topography with thisthreshold elevation (i.e., the more stands on upper slopesat >= 400m a.s.l. than those at <400m a.s.l., ÷2, p<0.05).According to these results, we divided 199 stands intothe upper elevation groups (102 stands, >= 400m a.s.l.)and lower elevation groups (97 stands, <400m a.s.l.), andmade same analysis as for all 199 stands. In upperelevation stands, Q. gilva and Q. glauca showed biasedoccurrence on the lower slopes (Table 2, Fig. 4), andunclear topographic preference in the lower elevationstands (Table 2, Fig. 5). In the lower elevation stands, Q.sessilifolia’s dependence on topography was mostevident; this species occurred mostly on the lower slopesin the lower elevation range. Q. acuta and Q. hondae,though these species did not have enough samples in thelower elevation for statistical test, tended to occur more(for Q. acuta) and less (Q. hondae) on upper slopes.

Average SD Min - Max at 50 (at 25 - at 75) at 50 (at 25 - at 75)

All stands 208 435.0 303.6 5 - 1170 390 (180 - 630)* 380 (190 - 610)*Q. acuta 64 725.0 259.5 40 - 1160 750 (540 - 930) 780 (630 - 940)Q. salicina 102 497.0 231.8 45 - 1120 480 (320 - 630) 520 (390 - 690)Q. myrsinaefolia 21 430.7 192.6 150 - 830 410 (260 - 560) 560 (270 - 610)Q. sessilifolia 40 431.1 188.5 40 - 850 420 (270 - 560) 440 (270 - 610)Q. gilva 61 335.5 192.3 15 - 1040 280 (190 - 470) 270 (200 - 430)Q. glauca 100 255.9 185.8 5 - 830 250 (100 - 400) 180 (60 - 380)Q. hondae 15 207.7 142.1 40 - 570 160 (50 - 270) 115 (50 - 200)* Cumulative dominance for all stands were calculated based on the sum of dominance of the seven Quercus species.

Stand type

Table 1 Elevation attributes of all examined stands and those where the seven Quercus species occurred. Elevations at 25,50 and 75 percentiles of cumulative frequency (number of stands) and cumulative dominance of each species were listed.Cumulative values were counted from lower to upper elevation.

Numberof stands

Elevation statistics (m) Elevation at percentiles ofcumulative dominance (m)

Elevation at percentiles ofcumulative frequency (m)

n 1) χ2 statistics p 1) n 1) χ2 statistics p 1) n 1) χ2 statistics p 1)

Q. acuta 61 9.920 0.019 53 6.694 0.082 8 - -Q. salicina 102 4.130 0.248 66 0.658 0.883 36 4.418 0.220Q. myrsinaefolia 20 3.001 0.392 11 - - 9 - -Q. sessilifolia 39 18.824 0.000 24 6.696 0.082 15 22.063 0.000Q. gilva 62 12.422 0.006 21 8.454 0.037 41 3.451 0.327Q. glauca 96 7.611 0.055 24 7.976 0.047 72 0.946 0.814Q. hondae 13 9.251 0.026 1 - - 12 - -1) n , total number of stands where the species occurred; p , significance level.

Table 2 χ2 statistics of the number of stands where each species occurred reffering to the four topographic categoriesamong 199 investigated stands .

Whole range of elevation(199 stands)

Upper (>400m) range ofelevation (102 stands)

Lower (<=400m) range ofelevation (97 stands)Species


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Fig.3. Percentage of four topographic categories of stands where the each species occurred at the whole examined range of elevation. Figures above each bars indicate total number of stands where the species occurred.Right most bars indicate the percentages for the all 199 examined stands.

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Fig.4. Percentage of four topographic categories of stands where the each species occurred at upper range of elevation (>400m). Figures above each bars indicate total number of stands where the species occurred.Right most bars indicate the percentages for the all 102 stands at the elevation range.

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Fig.4. Percentage of four topographic categories of stands where the each species occurred at upper range of elevation (>400m). Figures above each bars indicate total number of stands where the species occurred.Right most bars indicate the percentages for the all 102 stands at the elevation range.

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4. Species correlation The 101 examined species was grouped into two majorgroups, the group A and group B by the cluster analysis(Fig. 6). Of the seven Quercus species, Q. gilva, Q. glaucaand Q. hondae were include in the group A, and the groupB consisted Q. acuta, Q. salicina, Q. myrsinaefolia andQ. sessilifolia. The group A was subdivided into subgroups a1, a2 anda3. The subgroup a1 included several secondary forestspecies such as Castanopsis cuspidata and Pinusdensiflora. The subgroup a2 consisted of Q. glauca andmany pioneers of early-seral species (e.g., Idesiapolycarpa, Styrax japonica, Fagara ailanthoides, Albizziajulibrissin, Rhus sylvestris and Celtis sinensis) with thecomponent of Symploco glaucae-Castanopsietumsieboldii (e.g., Ilex chinensis, Neolitsea sericea, Perseathunbergii and Camellia japonica). The subgroup a3comprised Q. gilva and Q. hondae, associated with boththe components of Symploco glaucae-Castanopsietumsieboldii (Symplocos glauca, Meliosma rigida, Ilexrotunda, Castanopsis cuspidata var. sieboldii) andLaciantho-Quercetum gilvae (Diospyros morrisiana,Elaeocarpus japonicus, Symplocos theophrastaefolia andSymplocos lancifolia). The group B was subdivided into b1 and b1. The

subgroup b1 consisted of Q. acuta, associated with Tsugasieboldii, Pieris japonica, Illicium anisatum, Abies firmaand Symplocos myrtacea the major component of Illicio-Abietetum firmae, and the species of Fagetea crenatae(e.g., Fagus crenata, Stewartia monadelpha, Acersieboldianum, Quercus crispula, Carpinus laxiflora andAcanthopanax sciadophylloides). The subgroup b2comprised the components of Quercetum sessilifolio-myrsinaefoliae (e.g., Quercus sessilifolia, Quercusmyrsinaefolia, Quercus salicina, Ilex integra, Cleyerajaponica and Trochodendron aralioides)

Discussion

Seven Quercus species examined in this study were ableto be classified into two groups: the upper elevation type(Q. acuta, Q. salicina, Q. myrsinaefolia and Q.sessilifolia) and the lower elevation type (Q. gilva, Q.glauca and Q. hondae). Though Q. myrsinaefolia and Q.sessilifolia seemed to be intermediate in terms of theoccurrence and dominance feature along the elevationgradient, the cluster analysis grouped these two speciesas the associate with Q. salicina. Thus, it is appropriateto distinguish these two species as the upper elevationtype. The two species groups classified by cluster analysis(groups A and B) approximately corresponded with the

Fig.5. Percentage of four topographic categories of stands where the each species occurred at lower range of elevation (=<400m). Figures above each bars indicate total number of stands where the species occurred.Right most bars indicate the percentages for the all 97 stands at the elevation range.


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components of Maeso - Castanopsion sieboldii allianceand Quercion acuto - myrsinaefoliae alliance,respectively, suggesting a validity of the classification ofthe upper and the lower elevation types. The analyses also revealed the inter-specific differencesin topographic preference and regional distribution ofQuercus Spp. As the data used in this study had notsampled systematically, there was still a possibility thatthe detected distribution traits did not exactly reflectedtheir natural distribution. However, we believe that theresults here would indicate the major characteristics ofdistribution at least in the investigated region. From these results, we described the traits of ecologicaldistribution of the seven Quercus species as follows.

Q. acuta

The upper elevation type, having the highest elevationrange of distribution among the seven species. Thoughthis species has a wide elevation range, the range fordominating is c. 700-900m a.s.l.. This range wasconsistent with the report by Okano and Suzaki (1989).Frequent occurrence on ridge and/or the upper slope,which have generally known as poor soil conditions,suggested relatively higher tolerance to moisture stress.Fujiwara (1981) noted this species being distributed inthe ‘cloud zone’. The ‘cloud zone’ is compatible to thedominating elevation of this species, and thought to bethe site of less desiccation because of low vapor pressuredeficits. However, in our results, Q. acuta growing onthe upper slopes at low elevation indicated a possibleadaptability of this species to poor soil conditions.

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Quercus glauca, Cornus macrophylla, Albizzia julibrissin, Styrax japonica, Idesia polycarpa, Fagara ailanthoides, Cornus controversa, Rhus sylvestris, Celtis sinensis, Premna japonica, Aphananthe aspera, Ilex chinensis, Neolitsea sericea, Persea thunbergii, Camellia japonica, Cinnamomum insularimontanum, Lindera erythrocarpa, Zelkova serrata, CinnamomumCamphora, Acer palmatum, Podocarpus macrophyllus, Pittosporum tobira, Litsea lancifolia, Elaeocarpus sylvestris, Torreya nucifera, Ligustrum japonicum, Ilex latifolia

Schoepfia jasminodora, Lithocarps glabra, Rhus succedanea, Lyonia ovalifolia, Ilex macropoda, Eurya japonica, Myrsine seguinii, Prunus jamasakura, Pinus densiflora, Castanopsis cuspidata, Dendropanax trifidus, Myrica rubra, Daphniphyllum macropodum, Clethra barbinervis, Daphniphyllum teijsmannii

Quercus hondae, Quercus gilva, Symplocos glauca, Meliosma rigida, Ilex rotunda, Castanopsis cuspidata var. sieboldii, Diospyros morrisiana, Elaeocarpus japonicus, Symplocos theophrastaefolia, Symplocos lancifolia, Prunus spinulosa, Heliciacochinchinensis, Mallotus japonicus, Ficus erecta, Acer mono, Xylosma congestum, Sapindus mukorossi, Camellia sasanqua, Cryptomeria japonica, Persea japonica, Callicarpa japonica, Litsea acuminata, Symplocos prunifolia, Ilex buergeri, Micheliacompressa, Sciadopitys verticillata, Lithocarpus edulis

Quercus acuta , Tsuga sieboldii, Pieris japonica, Illicium anisatum, Abies firma, Symplocos myrtacea, Cephalotaxus harringtonia, Fagus crenata, Stewartia monadelpha, Acer sieboldianum, Quercus crispula, Carpinus laxiflora, Acanthopanax sciadophylloides, Sapium japonicum, Kalopanax pictus, Evodiopanax innovans, Rhus trichocarpa, Cornuskousa, Neolitsea aciculata, Symplocos lucida, Ilex pedunculosa, Acer rufinerve

Quercus sessilifolia, Quercus myrsinaefolia, Quercus salicina, Ilex integra, Cleyerajaponica, Trochodendron aralioides, Carpinus tschonoskii

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Quercus glauca, Cornus macrophylla, Albizzia julibrissin, Styrax japonica, Idesia polycarpa, Fagara ailanthoides, Cornus controversa, Rhus sylvestris, Celtis sinensis, Premna japonica, Aphananthe aspera, Ilex chinensis, Neolitsea sericea, Persea thunbergii, Camellia japonica, Cinnamomum insularimontanum, Lindera erythrocarpa, Zelkova serrata, CinnamomumCamphora, Acer palmatum, Podocarpus macrophyllus, Pittosporum tobira, Litsea lancifolia, Elaeocarpus sylvestris, Torreya nucifera, Ligustrum japonicum, Ilex latifolia

Schoepfia jasminodora, Lithocarps glabra, Rhus succedanea, Lyonia ovalifolia, Ilex macropoda, Eurya japonica, Myrsine seguinii, Prunus jamasakura, Pinus densiflora, Castanopsis cuspidata, Dendropanax trifidus, Myrica rubra, Daphniphyllum macropodum, Clethra barbinervis, Daphniphyllum teijsmannii

Quercus hondae, Quercus gilva, Symplocos glauca, Meliosma rigida, Ilex rotunda, Castanopsis cuspidata var. sieboldii, Diospyros morrisiana, Elaeocarpus japonicus, Symplocos theophrastaefolia, Symplocos lancifolia, Prunus spinulosa, Heliciacochinchinensis, Mallotus japonicus, Ficus erecta, Acer mono, Xylosma congestum, Sapindus mukorossi, Camellia sasanqua, Cryptomeria japonica, Persea japonica, Callicarpa japonica, Litsea acuminata, Symplocos prunifolia, Ilex buergeri, Micheliacompressa, Sciadopitys verticillata, Lithocarpus edulis

Quercus acuta , Tsuga sieboldii, Pieris japonica, Illicium anisatum, Abies firma, Symplocos myrtacea, Cephalotaxus harringtonia, Fagus crenata, Stewartia monadelpha, Acer sieboldianum, Quercus crispula, Carpinus laxiflora, Acanthopanax sciadophylloides, Sapium japonicum, Kalopanax pictus, Evodiopanax innovans, Rhus trichocarpa, Cornuskousa, Neolitsea aciculata, Symplocos lucida, Ilex pedunculosa, Acer rufinerve

Quercus sessilifolia, Quercus myrsinaefolia, Quercus salicina, Ilex integra, Cleyerajaponica, Trochodendron aralioides, Carpinus tschonoskii

Fig. 6. Cluster analysis dendrogram of 101 species based on data from 209 stands.


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Q. salicina The upper elevation type. This species was most frequentthroughout the investigated elevation range, and spatialdistribution. From its high dominance at lower elevationcompared to Q. acuta and no topographic preference, thisspecies has the highest adaptability to environmentalvariations in various scales, taking together with itspreviously reported shade tolerance (Tanouchi &Yamamoto 1995) and vigorous sprouting ability (Miyoshi1953). In conclusion, this species is considered to be atypical generalist among the seven Quercus species.

Q. myrsinaefolia The upper elevation type, but having a slightly lowerelevation range (lower than 800m a.s.l.) compared withthe former two species. This species occurs in the sameelevation range but less frequent compared to Q.sesslilifolia. Geographic distribution suggested inlandtype characteristics. This may partly be due to thedistribution of middle elevations in Kyushu Island.However, a contrast with Q. sessilifolia suggests thisspecies as the inland type. Dependence on small scaletopography is not clear.

Q. sessilifolia The upper elevation type, but having a slightly lowerelevation range as Q. myrsinaefolia. We specially mentionthe distribution of this species biased on lower slopesparticularly at lower elevation. As this biased distributionis more apparent than the three low elevation type species,Q. sessilifolia can be characterized as one of the ripariancomponents in mountainous evergreen broadleavedforests at low elevation in Kyushu. This would probablybe explained by local climates of riparian regions such aslow temperature and high humidity (cf. Takagi,unpublished data).

Q. gilva The lower elevation type. Although most previous studiesreferred to the preference of this species to rich soil onlower/foot slopes (Suzuki 1960, Itow 1975, Miyawaki1981), wide distribution range and less topography-dependence at lower elevation obtained in this studysuggest wider potential habitats of this species. Q. gilvahas been widely planted in southern Kyushu (cf. Taoda,2004), because this species produces good timber. Thus,we could not deny the possibility that the dataset used inthis study contained old plantations of this species.

However, high dominance even on the upper slopes stillsuggests the ability of this species to grow in wide rangeof environment. High plasticity of leaf water relations(Ito et al. unpublished) also supports this hypothesis. Thisspecies also has high plasticity in light response ofphotosynthesis (i.e., variations of sun and shade leaves,Ito et al. unpublished), suggesting that this species mustbe a late-seral or climax species of this region (Tanouchi1990; Taoda, 2004).

Q. glauca The lower elevation type. This species has a similardistribution trait to that of Q. gilva, but have notopography-dependence at lower elevation, indicatinggeneralist characteristics. The high frequency whichfollowed to Q. salicina also suggest this species asgeneralist. However, compared to the range of elevationand regional distribution of Q. salicina, the ecologicaldistribution of Q. glauca seems to be narrow; restriced to<ca 600m a.s.l. On the other hand, high correlation withdeciduous pioneers and early-seral species suggests adependence of this species on disturbances. Tanouchi(1990) also pointed out the early-seral characteristics fromthe view point of growth under a shade compared to Q.gilva. Miyawaki (1981) referred to the site condition ofQ. glauca -dominated forests as gravel soil on steepslopes, where frequent disturbance can be expected. Thus,the summary of Q. glauca as disturbance-dependentcharacteristics must be reliable.

Q. hondae The lower elevation type. This species is most infrequentspecies limited to lower slopes of lowland in the east coastof Kyushu. Q. hodane previously reported to bedistributed at <200m a.s.l. in southern Kyushu andShikoku (Mashiba, 1973). However, our analysissuggested that the distribution range of this species isslightly wider (<350 m a.s.l.). Less occurrence of Q.hondae on upper slopes indicate the stronger sitepreference than that of Q. gilva. Lower plasticity of leafwater relations than those of Q. gilva (Ito et al.unpublished) would explain the strong limitation ofdistribution to lower slopes. Explanation of concentrateddistribution of this species to the east coast of Kyushumay require another discussions form the view point of ageological time scale.

Acknowledgements


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A part of this study was supported by Grant-in-Aid forScientific Research form JSPS (No.11660154, 14360090,15380110).

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