Verticaldistribution Forestof Mt. Pulog,Cordiiiera The

The Society ofofVegetationScience Vegetation Science

Vegetation Science, 15 :19-32, 1998. 19

Vertical distribution and structure of the tree yegetation

in the montane forest of Mt. Pulog, CordiIIera mountain range, the highest mountain in Luzon Is., Philippines

I. E. Buot, Jr. and S. Okitsu

Laboratory of Forest Ecology, Graduate Scheol of Science and Technology, Chiba University, 648 Matsudo, Matsudo City, Chiba 271-8510 JAPAN

The altitudinal zonation of the rnentane forest of Mt. Pulog (2924 m altitude), Cordil!era

mountain range, the highest mountain in Luzon Is., Philippines was described and compared

with other mountains in the Philippines and in the tropics. Three vegetation zones were

clistinguished from ca. 2000 m to 2700 m altitude each indicated by the cornmon dominant

species in the site; Zone I (ca. 2000 m to 2400 m altitude), Pinas zone cemposed of a distinct pure Pinus forest (ea. 2000 m to 2300 m altitude) and a Pin"s-Deutzia-Schefi7era forest (ca. 2300 m to 240e m altitude, Zone II (ca. 2400 m to 2600 m altitude), LithocaiPzrs-Dac,yca?Pus-SL4Jlgium-

Loptosper"tum forest and, Zone III (ca. 2600 m to 2700 m altitude) , Rhododendron-Clethm-Eurya forest. The floristic character was not simi!ar to the other mountains in southern Luzon and the

rest of the Philippines because of the presence of a number of northern types (e.g. Sleimmia,

Pinus, Uex and others) on Mt. Pulog. The number of species and species diversity, DBH, and

height tended to decrease with increasing altitude. Dominant component species at the upper

altitudinal forest zones were found to be the sarne species forming the unclerstory elements of

the lower altitudinal forest zones. The change of the vegetation between each zone was not

gradual in contrast with the ether tropical mountains. Mt. Pulog appears to be a southern extension of north temperate flora and the northernmost limit of the tropical mossy forest, a

unique forest type within the montane zone in the tropics.

Key words: altitudinal zones, Cordillera mountain range, floristic character, Mt. Pulog, tropical

tree vegetation

over, the vegetation structure along altitudinal gradi- INTRODUCTION ents seems to be a unique one in the Philippines. It has

Until the present time details on the vertical distri- a pure pine forest, a mossy forest and a 2000-hectare-

bution and structure of the vegetation on Mt. Pulog grassland summit (Merrill & Merritt 1910). The

(2924 m altitude) of the Cordillera mountain range, mossy forest which is a physiognomic variation of the

the highest mountain in Luzon Is., Philippines, has montane forest in the tropics due to physiography

been left unattended. Mt. Pulog has an interesting (Beard 1955) is very prominent and well-developed in

vegetation formation. Floristically, it is different from Mt. Pulog.

the rest of the Philippine mountains by the absence of Some taxonomic literatures already provide data the dipterocarp flora in its lower slopes (Dickersonon flora and some particular vegetation zones or

1928). Phytogeographically, Mt. Pulog is the converg- species on Mt. Pulog. Merrill and Merritt (1910)

ing point of plant species of Asiatic, Malayan and wrote about the flora of Mt.Pulog. Jacobs (1972) Australasian origin (Merrill & Merritt 1910). More- studied the topography, vegetation and flora of the

mountain with particular reference to the grassland

summit. Santos (1979) made some observations on a Received April 28, 1997 Accepted January 18,1998 dwarf bamboo, Yitshania niilakayamensis (Hayata)

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Keng f, on the grassland summit. Buot and Okitsu below 2000 m altitude.

(1997a) described the woody species composition at The slopes of Mt. Pulog are generally quite steep

various altitude of the mossy forest region. Those and the soil is fairly deep apparently formed for the

taxonomic studies revealed that Mt. Pulog flora has greater part by the rapid decomposition of rock in about 528 species of bryophytes, pteridophytes and place except in heavily-eroded steep slopes of the spermatophytes growing in the various altitudinal rocky pine forest where soil is very shallow (Merrill

zones of the mountain, The flora has been described & Merritt 1910).

as unique and essentially Asiatic rather than Malayan, The mean annual precipitation (1974-1994) was

Three general vegetation types of this mountain 3845 mm in Baguio City, Benguet (ca. 15eO m alti-

had also been already identified by Merrill and Mer- tude), south of Mt. Pulog. Annual mean temperature

ritt (1910) in the altitudinal range from ca. 12eO m to (1974-1994) from the same weather station was 2924 m: 1) pine forest, 2) mossy forest and 3) grass- 19.4℃ . The coldest rnonth, January, had a mean tem-

land. Recently, Buot and Okitsu (1997b) preliminarily perature of 12.8℃ . Hence at ca. 2000 m altitude, the

identified three vegetation zones in the mossy forest annual and January mean temperature would be 16℃

region of Mt. Pulog, Those vegetational studies, and ℃ respectively. how- 9 , At the upper limitof the pine ever, reveal still insufficient aspects of the vertical forest, at ca. 2300 m altitude the annual mean would

zonation of this mountain. be 14℃ and 7℃ for the coldest month. The expected

This paper first aims to clarify the zonation pattern temperature reading at ca. 2600 m to 2700 m altitude, of the vegetation on Mt. Pulog from the pine to the

mossy forest (Merrill & Merritt 1910) . Then it discus-

ses the iloristic character, species diversity, structure 116,E 127SE1l[1111 1 oo of the vegetation and the structure of the altitudinal N 1

zonation comparing with other mountains with refer- 1

ence to the phytogeographical characteristics of this 1 . mountaln. 1 l.!5.0N-. STUDY SITE

! Mt. Pulog (16"3e'36"N, 120e5e'20" E) , situated at [ about 60 krn from the coast on the Cordillera moun- 1 "ti,

tain range, is the main massif of Mt, Pulog National 1 1 Park of Benguet, Ifugao and Nueva Vizcaya prov- 1 inces which includes three main mountains, Mt. Pulog 1 (Fig. 1), Mt. Tabeyo (2819 m altitude) and Mt. Akiki 1 (2318 m altitude). The three mountains are non- I･ volcanic, 1 p The study site was mainly on the southern and 1

eastern slopes of Mt. Pulog, Benguet from ee province 1 " ft 2000 m to 2700 m altitude. This site was selected diqll{l' l4!Nl :" a"1 because the tree vegetation types in the altitudinal .., . tt: range was quite intact. Below 2000 m altitude down to 1 [ Onftokm the lowest recorded elevation of Mt. Pulog which is

1200 m altitude, there is disturbance from fire and

human activities. Commercial pine plantations fre- Fig. 1. Map of the Philippines showing Mt. Pulog, quented by fire and agricultural lands are extensive Mt. Makiling, and Mt. Apo,

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would be 12 ℃ and 5-6℃ for the annual mean and the (RBA) derived from DBH values. Absolute basal area

coldest month, respectively. values were not used because of the inherent weak-

ness of the point centered quarter method to tend to METHODS exaggerate basal area and density values in a given Seven sampling sites were idgntified on the southern site (Mueller-Dombois & EIIenberg 1974). Besides and three sites on the eastern slopes of Mt. Pulog from that, some sampling sites were not also large enough

2000 m to 2700 m altitude to follow the changes in owing to the difficulties encountered in sampling due

floristic composition, dominance of woody species and to unfavorable and dangerous topographic conditions.

forest structure. The point-centered quarter method Hence, relative basal area values were used. All

(Mueller-Dombois & Ellenberg 1974) was used at sites species were then subjected to cluster analysis. First,

set at elevations 2325, 2400, 2485, 2520, and 2585 m the dissimilarity matrix of the floristic composition in

above sea level and a minimurn of 20 points composed every sampling site was calculated based on the RBA

of 80 quarters were sampled per sampling site. The using the squared Euclidean distance (Tanaka &

distance between points was 15 m to 25 m depending Tarumi 1995) as follows:

m on the steepness of the slope of the sampling site. The - dij-- Cxki xig･)2 sampling points were situated more or less along the k\.I

contour of the sampling site depending on the topo- where, di,･ squared Eucliden distance between plots i

graphic conditions. However, at elevations 2615 m and andh m=number of species, xhi--relativebasal

27eO m, the forest limit, the quadrat technique area of the kth species in plot i, and xld -m relative basal

(Mueller-Dombois & Ellenberg 1974) was used as the area of the feth species in plot j. A dendrogram was

vegetation was short and many species tended to be then constructed using the single-linkage clustering or

shrubby with many stems. The size of the quadrat was nearest neighbor method (Sneath & Sokal 1973).

25 m2 each (5x5 m) . Likewise, below 2325 m altitude Floristic diversity of each sampling site was

the quadrat technique was also used to determine the examined using the Shannon-Wiener's index (Shan-

vegetation structure of the pure pine forest. The sizes non & Weaver 1949) as follows:

bf the quadrats were 72e m' (24X 30 m) for 2000 m and = - H' opT) 2100 m altitude sampling sites and 400 m2 (20× 20 m) ,i.lii(pt)Ciogi

for the 2200 m altitude sampling site. Woody species where H'= index of diversity, Pi -- the proportion of arl

having at least 1.3 m in height were measured from individuals in the sarnple which belong to species i,

2000 m altitude to 2585 m altitude. At the forest limit and m=: number of species.

where the vegetation was short, woody species with at RESULTS least O.5 m height were included. Identity of the

species, the height in m, and the diameter at breast Species composition

height (DBH) in cm were determined Sample speci- There were a total of 36 woody species belonging to

mens from each unidentified tree were collected. 21 families determined on the southern and partly on

Likewise, the elevation (rn),slope (degree), exposure the eastern slopes of Mt. Pulog (Table1). Twenty-

and the area (mi) were recorded in every sampling two species belong to the plant families mainly in the

site. temperate regions such as Pfnaceae, Ericaceae,

Unknown specimens were then identified at the Fagaceae, Podocarpaceae, Lauraceae, Saxifragaceae,

herbarium (CAHP) of the University of the Rutaceae, Caprifoliaceae, Compositae, Theaceae and

Philippines at Los Bafios (UPLB), Laguna, Aquifoliaceae. Pinaceae had one species; Pinus keslya

Philippines, Our nomenclature followed mainly that of Royle ex Gordon. Ericaceae had five species; Rhodo-

Merrill (1923a, 1923b, 1925, 1926). dendron st{bsessige Rendle, VZzccinium indutum Vid.,

Dominance was based on the relative basal area I,lrccinium sp., Gaulthen'a cumingiana Vid. and, Di-

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Plycosia sp. Fagaceae was represented only by two Lithocarpus-Iinc,yca,Pvcs-twzJtgium-Loptospermum for-

species; Lithocarpt{s zvoodii and Lithocatoijus sp. est and, Zone III) Rhododendron-Clethra-Etc,],a forest.

Podocarpaceae had only one species; Dac}o,carptts

stempii de Laub. Lauraceae had three members; IVbolit- Zone I . Pinus forest zone, 2000m to 2400m altitude

sea micmpibylla Merr., iVL mqgacarpa Merr. and 1'ersea (sampling sites 1, 2, 3, 4)

philippinensis Elm. Saxifragaceae was represented by The Pinzts zone on Mt. Pulog has two distinct group Deutsia Pulchra Vid., Pblyosma PhilipPinensis Merr. as shown in the cluster at a dissimilarity level of about and an unknown Saxifragaceae species. Rutaceae had 1,5 (Fig. 2). These two groups are, the pure llintts

two species; Sleimmia 1'mponica Thunb. and Eatodia forest from 2000m to 2300m altitude (sampling sites

reticulala Merr. Caprifoliaceae was represented by 1, 2, 3) and the mixed pine-broadleaved forest

Viburnum odoratdssimum Ker. while Compositae had designated as Pinus-Deudela-SchqMera forest at 2300m

Vbrnonia benguetensis Elm. Theaceae was represent- to 2400m altitude (sampling site 4).

ed by two species; Ebe7ya nitidu (Korth.) Dyer and E. The pure Pinus forest. On Mt. Pulog, pure Pinus

coriacea Merr. and Aquiforiaceae was represented by forest reaches up to 2300m altitude. Pinus feeslya is the

only one species, Ilex crenata Thunb. forma luaonica onry canopy tree to be found in the site. It forms an

(Rolfe) Loes, open park-like forest often associated with some

Conversely, fourteen species, being smaller in num- species as EhrPaton'um adenQPhorzam (Compositae), ber than the temperate families, belong to the tropical Coriaria intermedla (Coriariaceae) and imPemte taxa such as Euphorbiaceae, Clethraceae, aylindrica (Gramlneae).

Myrsinaceae, Cyatheaceae, Myrtaceae, Rubiaceae, The maximum DBH value was 57cm found in sam-

Araliaceae, Winteraceae, Proteaceae and Sabiaceae. pling site 1. The maximum height was 30m found in

Euphorbiaceae was represented by Mdcara]aga dipter- sampling site 1. The pine was the only tree species in

ocarptt2)lia Merr. and Dmphnipdyllum glaucescens BI. the sarnpling site, hence the RBA recorded for the

Clethraceae had Clethm luzonica Merr. Myrsinaceae three sampling sites was 100% each.

had Rapanea PhilipPinensis (A. DC.) Mez. and Mdesa The pure pine forest on Mt. Pulog occurs only on

dbnticulate Mez, Cyatheaceae was represented by very steep and frequently eroded slopes with poor,

(lyathea fotliginosa (Christ.) Copel. Myrtaceae had rocky and shallow soil having low water holding

three species; Decaspermum Paniculatum (Lindl.) capacity. This makes the site arways dry favoring

Kurz., byzJ{gium besukiense

AustralianLoptospemaum ,ilLzvescens Sm. The species Pinus keslyaforeston Mt. Pulog isone of the few

of Rubiaceae was Rsychotria crispipila Merr, Pin"s kesdya forests in the tropical Asia. Others are

Araliaceae had Sehe}fi7era oblongijbha Merr. Winter- found in northern Thailand (Walker & Pendleton aceae was represented by the Australian Drt'mys 1957, Whitmore 1984, Santisuk 1988), Burma (Stamp Pipen'la Hook. f. Proteaceae had Hlrlicia robusta Wall 1925, Walker & Pendleton 1957), Vietnam (Walker & while Sabiaceae was represented by Meliosma multi- Pendleton 1957), Chittagong (Banglaclesh) (Merrill & flbm Merr. Merritt 1910) and in Assam (India)

Merritt 1910, Bor 1938).

Altitudinal zones The Pinets-Deuteia-Schqfi7era forest. The mixed pine-

Table 1 and the dendrogram (Fig. 2) reveal three broadleaved forest at 2300m to 24eOm altitude (sam- altitudinal zones of forest tree species on the montane pring site 4) is the lower limit of the mossy forest.

zone of Mt. Pulog from 2000m altitude to 2700m Mosses, Iiverworts and Iichens cover abundantly the

altitude. The cluster at a dissimilarity level of about ground, and the trunks and crowns of trees. This 2,5 shows three vegetation zones. The three forest forest is the transition between the pure Pint{s forest

zones are; Zone I) Pinus forest, Zone ll) below 2300m altitude and the typical mossy forest.

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[ Ie 17ee

9 ;61SRhododendrontSynyLgiu"t-E"o,a-cathraC7ethra-Rhodedendeen-Eunpa Zone M

s 2SS5ISIO &rvglvnt-Leptospermum-Paccyearpus-Lnthoearpuswuodi

1 Pa=rycarpus-LithoearpllsHvodii-Lithocao7ussp,

Zone II 6 2#S5 Lithocqrpus-Feodh'.DaccFcarp"s-Lithocarpussp.

f !400 Lithocarpusmoedi-E"cva-Neolitsent

4 2]2S Pinlls-Deutt'a-Sehc07era l1 31 !100 Pinas 11l[ Zone l moo Pin"s

1 loDe PinJts - ,

4 3 1 t S;tc Altltllde(m) Deminnnt Spccies SgijAredEucl:deand:stAnce ' Fig. 2. Dendrograrn of ten samp]ing sites on the altitudinal zones of Mt. Pulog montane forest obtained by the nearest neighbor method using the squared Euclidean distance (Tanaka & Tarumi 1995) . Three altitudinal tree vegetation zones were identified from 2000m to 2700m altitude: Zone I ) Pintes forest at 200em to 24eem altitude, Zone II} Lithocarptss-llac,],carpus-S,zngium- Laptospe77num forest at 2400m to 2600m altitude and, Zone III) Rhodbclencthron- Clethra-Etzrya forest at 2600m to 2700rn altitude.

The maximum DBH was 177cm whire the maximum (sampling sites 5, 6, 7, 8)

height was 25m (Table1), This zone is a well-developed mossy forest char-

The three top dominants of this forest are R keslya acterized by having large and tall trees covered with

Royle ex Gordon, Deuteia pulchva Vid. and SchqMeva Iichens and bryophytes on their trunks and branches.

oblo7agijblia Merr. (Table 1) with RBA values of 67%, The maximum DBH was 95cm while the rnaximum

and respectively. 9.1% 6.3%, height was 35m (Table 1).

These three dominating species occupied the canopy There were seven tree species dominating this for- layer. The dominant pine trees in this forest, however, est zone. The most common were Lithocarpus woodii

differ from those found in the pure pine forest by (Hance) A, Camus, Ilac7yca7Pus stempii de Laub.,

being richly Iaden with bryophytes and lichens on fly4J{gium besukiense (Miq.) Masamune and Leptosper-

their trunks and crowns. Shrubby and herbaceous mum Lithocampus .t7dvescens Sm. woodii was dominant vegetation were crowding the understory of this vege- in the four sampling sites in this zone and was the top

zone. stands of tation Few Rhodbclendron subsessile dominant in sampling sites 5 and 6 with RBA values of Rendle and Clethra lu2onica Merr. which usually 52% and 19.6%, respectively. Dac7yca?Pzas steuPii was

dominate in higher altitudes were observed in this dominant in sampling sites 6, 7 and 8. It had the

forest, highest RBA in sampling site 7 <37%), beingthe top dominant. S;,aygium besukiense was top dominant in Zone II Lithoca,tPus-Dacxl,ca71Pus-Syzygium- , sampling site 8 with RBA of 35%. Laptospemaum

LqPtosPermum iorest zone, to 2600m altitude 2400m .tlavescens with RBA of 2e.3% was the second domi-

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nant species in sampling site 8. tiori of sampling sites 1, 2, and 3 (Fig. 3B). A similar

The other dominants were the lauraceous Arbolitsea trend was observed for DBH and height at various

micropdylla Merr. in sampling site 5, with RBA of altitudinal zones. The maximum DBH for sampling

7,8%, the fagaceous Lithoca,1)tts sp. in sampling sites site 1 was 57cm while that of sampling site 10, the

6 and 7 with RBA of 11.4% and 19%, respectively, and maximum DBH was 11 cm (Fig. 3C). The maxirnurn

the theaceous species, Eu,),a nitido (Korth,) Dyer in height for sampling site 1 was 30m whereas that of

sampling site 5 with RBA of 14.5%. sampling site 10 was 8m (Fig. 3D). Constituent species

This Iauro-fagaceous, podocarpaceous, theaceous at the lower elevations were bigger and taller than the

and myrtaceous mossy forest zone is unique in being ones in the higher altitudes which generally became

composed of tall and large trees with prominent crowns. Zone I II III 2s!o/s/o

Zonelll. Rhodociendron-Clethizz-Etzrya forest zone, .;u?ts:2i 456T8910A

2600m to 2700m altitude, (sampling sites 9, 10)

This is the upper Iimit of the mossy forest region

being the forest Iimit on Mt. Pulog. Above this zone is so/.2 123 the grassland summit with scattered Rhoclodendron

subsessile and Vticcinium sp. in steep slopes.

,ose.eo.ae.2 Vegetation was composed of few species (8 species B each for sampling site 9 and 10) with small individuals 2sl ' having a maximum DBH of 21 cm (sampling site 9) and 11 cm (sarnpling site 10). The forest height tended to b6 very low with a maximum height of 8 m

There were four dominant species, Rhodbdendron EeEog.I:= subsessile Clethva luzonica, E. niticla, and S. beszdeien-

se. Clethra lu2onica was top dominant in sampling site c 9 (RBA of 48%) while R, subsessile was the top ' dominant in sampling site 10 (RBA of 41.6%).

It is noteworthy that the dominants of this zone (C, o

luzonica and R. subsessile particularly) are compo- -o

nents of the lower zones (zoneI and zone II) as ]s

:t:o D understory elements e$pecially in sampling site 4. itu 7S ;t 70 E,, .E Altitudinal changes in forest structure l"o s Changes in forest structural features along the o /IOO IWO EIan 71M 21an T-OP 1500 IEoe"on 7noo different altitudinal zones of Mt. Pulog are illustrated AL-TUDE Cm)

in Fig. 3. The number of species per sampling site Fig. 3. Structural characteristics of the ten sam- decreased with increasing altitude (17 species in sampling sites along the altitudinal forest zones pling site 4 and 8 species in sampling site 10) exclud- of Mt. Pulog from 2000m to 2700m altitude. ing the in zone I (Fig. 3A). Species diver- pure pine A) number of species, B) species diversity, sity, showed considerably values at H' higher the H' using the Sharmon- Wiener's index (Shan-

Iower for site 4) than at the (1.12dit sampling higher non and Weaver 1949) , C)maximum DBH,

artitudes (O.8 dit for sampling site 10) with the excep- D) maximum height.

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shrubby. forest region of Mt. Pulog (Pinas-Deuteia-St;hop7eva

forest of zone I and II) in contrast to that of the DISCUSSION upper zone (zone III). Sampling site 5 (zone II) has

FIoristic character and species diversity also lower number oi species and species diversity and

The tree flora of Mt. Pulog is in striking contrast to could be attributed to the smaller site sampled due to

that of the other Philippines parts of the (Dickersonunfavorable topographic conditions (deep and sharp

1928, Merrill I926). It presents a number of temperate gullies). There were 17 species in sampling site 4 and

types that do not occur elsewhere in the archipelago, there were only 8 species in sampling site 10 (Fig, 3A,

suggesting their derivation from the north. Typical Table 1), This decreasing trend of the number of

tropical families such as Arecaceae, Pandanaceae and species and species diversity towards higher altitudes

Dipterocarpaceae are not represented in Mt. Pulog had also been observecl by Brown (1919), Schoeniget

(Dickerson 1928). Contrarily, the flora in southern aL (1975), Whitmore (1984) and Ohsawa et al.

Luzon and the rest of the Philippines in general is (1985) . Furthermore, on Mt. Pulog, and in the tropics,

Malayan in nature (Dickerson 1928, Merrirl 1926, the species in the higher altitudes were also smaller in

1946, Ashton 1993, Buot et al. 1997). This is eviden- size and shorter in stature (Fig. 3C, 3D) compared

ced by the well-developed dipterocarp forest forma- with the forests in the lower altitudes. DBH values of

tion lacking in the Cordillera meuntain range (wnit- the pure pine forests in sampling sites 1-3, however,

ford 1911a, 1911b, Brown & Matthews 1914, Dicker- were not as high as expected of lower altitude forests,

son 1928, Schoenig et aL 1975, Seidenschwarz 1988). the highest recorded DBH being 57cm only (Table 1,

Merrill and Merritt (1910) reported that in the Fig. 3C) . This could be due to the extremely stressful

lower altitudes of the Pintss forest (ca. 1500m alti- conditions in the pure pine zone compared with the

tude) some tropical evergreen broadleaves such as mixed pine and the lauro-fagaceous forests.

Pittosporum Pentandrnm Merr., JiVctcs hauili Blanco, The reason for the variation in forest structure

Iil nota Merr., Premna odorata Blanco and others, along the altitudinal gradients is that, in tropical

were noticed at deep ravines and stream depressions. mountains, there is insufficient heat in such high

These species are widely distributed at low altitudes altitudes (ca. 2600m altitude in the case of Mt. Pulog) in Philippines. the In the Benguet region, however, to support enough organic production and to form a

they occur only in gullies and stream depressions. tall forest. The year-round decrease in temperature in Some Australasian elements represented by Le- higher altitudes cuts down available energy (for Ptospermum (Myrtaceae), QTcrycarptcs (Podocar- photosynthesis) needed to ferm a high forest (Ohsawa paceae) and Dri"ays (Winteraceae) among others are 1995). In temperate mountains with their seasonal

also present in Mt. Pulog. These species however are climate, the amount of avairable energy during sum-

also well-developed in the northern hemisphere and mer is often large enough to sustain maximum forest

must have reached Australia through Malaya (Merrill dimensions (Ohsawa et al, 1985). and Merritt 1910). Its occurrence on Mt. Pulog, how-

ever, had not yet been explained and needs to be Structure of the altitudinal zonation on Mt. Pulog

studied to better understand this peculiar distribution The first striking observation is the apparent simi-

pattern. larity of the dominants of the higher altitudinal zones

Thus, the floristic character of Mt. Pulog is quite to that of the understory elements of the lower

unique in the Philippines and phytogeographically, the altitudinal zones. This is evident in the case of Clethra

mountain the is floristicconverging pointof plant and Rhodbdendron which were the dominant compo-

species of Asiatic, Malayan and Australasian origins. nent species in the upper forest zones of Mt. Pulog

The number of species and species diversity (Fig. 3 (zone III) and which happened to be the constituents

A, 3B) were higher in the lower slopes of the mossy of the lower forest zones (sampling site 4 of zone I)

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as understory elements (Table 1). This had also been The boundary line between the lower and upper

observed ln Mt. Makiling (Brown 1919, Trelease & montane vegetation zones on Mt. Pulog is set at ca. McLean 1919), in Mt. Apo (Schoenig et al. 1975), in 2600m altitude. The huge and tall trees which are

Mt. Kerinci. (Ohsawa et al. 1985), and in tropical components of the lower montane zone reached their

mountains in general (Whitmore 1984, Ohsawa 1991). upper limit at 260em altitude on Mt. Pulog. These tall

Hence the upper forest zones seem te be equivalent in and large trees on Mt, Pulog included Pinus, Lithocar-

floristic composition to the understory of the lower pzts. Daciycarpus, S,ap{giu"z, Loptospenuum and others forest zones. This differs from that of the temperate (zone I, II). Above this zone, the small trees

mountains as in Japan, where the higher altitudinal (Rhododendron, Cleth7u, ltZtccinium among others)

vegetation zones (e,g. conifer zone) are composed of lesser than lem in height started to proliferate signify-

different species from the lower zones (e.g. evergreen ing the shift to the upper montane vegetation zone

broadleaves). (zone III). The rnain distinguishing characteristic

Several explanations such as mineral shortage, fre- between the lower montane and the upper rnontane

quent fogfcloud incidence (Grubb 1977), temperature zones is the physiognomy particularly the vegetation effects (Ohsawa 1991, 1993) and UV-B radiation height, Lower montane zone is composed of tall and

(Frenley 1992) had been given for this replacement huge trees (15m to 33m high) while the upper montane

phenomenon along altitudinal gradients on tropical zone is composed mainly of short and small trees and

mountams. shrubs (1.5m to 18 m high) (Grubb 1974, Whitmore

The second important observation on the vegetation 1984, Grubb & Stevens 1985, Richards 1996). In

zonation on Mt. Pulog is the quite distinct boundary addition, Ohsawa (1991, 1993) also emphasized the

between each vegetation zone along the altitudinal floristic and Ieaf morphological difference between

gradient (Table 1 and Fig. 2). Other mountains in the the lower montane and the upper montane zones in the Philippines such as Mt. Makiling (Brown 1919, tropics. The lower montane vegetation zone is largely

Trelease & McLean 1919) and Mt. Apo

al. 1975) have a gradual shift of vegetation change ing to families, Lauraceae, Fagaceae, Theaceae and

along altitudinal zones; the change of the vegetation is Myrtaceae while the upper montane vegetation zone

unnoticeable. On Mt, Pulog, the 1'inas forest (zone I ) is composed of microphyllous small trees and

is sharply differentiated from the succeeding ericaceous shrubs.

Lithocarptts-Ilac,ycarpzts-S,IJ{gizam-Loptospemaum for- The lower montane vegetation zone on Mt. Pulog

est (zone II) in terms of floristic composition and could be further subdivided into an extensive Rnus general physiognomy (Table 1, Fig. 2). The latter is forest (zone I) from 2000m to 24eOm altitude (prob-

composed largely of tall lauro-fagaceous, podocar- ably could be extended below 2000m altitude down to

paceous, theaceous and myrtaceous species which in the lowest recorded elevation of Mt. Pulog at 1200m

turn are in sharp contrast to the low-statured, one- altitude), and a Lithocamptts-Daciyca71)us-twaygium-

storied Rhododondron-Clethva-Eui2ya forest in zone III Lqptospermum forest (zone II) from 2400m to 2600m

(Fig. 2). altitude {Fig. 2, 4). The entire altitudinal range of the montane forest

of Mt. Pulog could be classified into two distinct Comparison of Mt. Pulog with other mountains

general vegetation zones (Fig. 4) based on structure The natural pure Pint{s kesdya forest (zone I) in the and physiognomy (Table 1, Fig. 2). The two distinct dry steep slopes of the lower montane vegetation zone

vegetation zones are the lower montane vegetation of Mt. Pulog (Fig. 4) has no equivalent in the tropical

zone and the upper montane vegetation zone folrowing mountains such as Mt. Makiling, Mt. Apo, Mt. Kerin-

Mt. Kinabalu or Mt. Wilhelm. However Pintts Grubb (1974), Whitmore (1984), Grubb and Stevens ci, (1985), Ohsawa (1991, 1993) and Richards (1996). leeslya had been observed in the tropical lower

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montane pine-oak and pine-deciduous dipterocarp for- holding capacity. Thus, even with the high annual

ests in northern Thailand at ca. 700m to 1800m alti- average precipitation record in Benguet (3845 mm

tude (Walker & Pendleton 1957, Santisuk 1988), in from 1974-1994), the steep pine forest is left dry. The

the oak forest of Burma at ca 1000m altitude (Stamp P, leeslya forest above 2000m altitude on Mt. Pulog

1925, Walker & Pendleton 1957), in the forest at sea may represent a topo-edaphic climax on precipices or

level in Vietnam (Walker & Pendleton 1957), in the shallow, stony soils that are simply too dry and infer-

forests of Chittagongdistrict(Bangladesh)(Merrill tile for other trees to grow, The pure stands of P,

& Merritt 1910) and Khasi hills, in Assam (India) at imwanensis in Taiwan lower montane forest at ca. 500

ca. 150em to 2200m altitude, the type locality of the m to 2500m altitude had been interpreted also as a

species from which the species epithet of Pinzas keslya topo-edaphic climax though it is considered as a seral

was derived (Merrill & Merritt 1910, Bor 1938). stage in many habitat types maintained by fire (Hsieh Coniferous forests in northern Thailand rnay be et al. 1994).

considered as a severe destruction stage of the lower Seme few shrubs, herbs and grasses such as Corikerin

montane oak forest or dipterocarp forest caused by intermedla, V2zccinium "ayrimdbs, and others were

biotic (burning, cutting, grazing) or edaphic (soil observed sparsely scattered in the open sites within

erosion) factors (Santisuk I988), On Mt. Pulog, traces the pure pine forest (sampling sites 1, 2, 3 of zone I) of fire occurrences and other human activities (agri-of Mt. Pulog. Neither pine seedlings nor seedlings of

culture) were observed in the pure pine forests below other trees found in the Pinus-Deuteia-Sthq07era forest 2000m altitude. However, in the sampling sites above (sampling site 4 of zone I) were observed under the

2000m altitude which are protected sites, traces of fire canopy of the pure pine stands. Pine seedlings were

occurrences were not observed, In these localities, the reported to only develop on well-lighted sites with

pine stands were confined in very steep, highly-eroded podzolic, well-drained mineral soil (Whitmore 1984). rocky slopes apparently having a very low water In the narrow valleys in the pure pine forest, small

Altitvde MLPuleg(2g24mEIO NtApo(2954mele

Fig. 4. A comparison of the altitudinal vegetation zones of Mt. Pulog with other Philippine mountains, Alt is altitude.

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trees and ericaceous shrubs (Rhodbdendron, etc,) 1200m to 2IOern altitude and in the subalpine forest at

were observed, In the lower elevations (ca. 1500m 2900m to 3600m altitude (Kitayama 1987, 1991, 1992).

altitude), the pine occurs exceptionally with some On Mt. Wilhelm in New Guinea, Dac7ycarptts occurred

evergreen broadleaves and grasses in the gullies and in the midmontane, upper montane and subalpine

stream depressions. This ceuld be exp}ained by the forests at ca. 2000m to 380em altitude (Wade &

relatively drier condition on the slopes and ridges McVean 1969, Johns 1982). On the other hand, Le-

compared with those in the gullies and stream depres- Ptospermum which dominated at 2400m to 26eOm sions (Merrill & Merritt 1910). In addition, clouds altitude on Mt. Pulog, was reported to dominate in the

which are frequent on Mt. Pulog upper montane forest lower subalpine forest of Mt. Kinabalu at ca, 2900m to

region (at 2600m to 27eOm altitude) as in other tropi- 3400m altitude (Kitayama 1987, 1991, 1992). cal mountains (van Steenis 1972, Leigh 1975, Sugden The upper montane vegetation zone of Mt. Pulog

1982, Whitmore 1984, Kitayama 1991, Ohsawa 1993) (zone III) at 26eO m to 2700 m altitude (Fig. 4) promoting moist and mossy condition, go down to the appears to be floristically related to the summit

lower limit of the mossy forest only (ca. 2300m alti- mossy forest (ca. 9eO m to 1114 m altitude) of Mt.

tude) except in severe stormy seasons. Hence the pine Makiling (Fig. 1 and Fig. 4) and that of the warm

forest (below 2300m altitude) is left relatively cloud- temperate zone of Mt. Kerinci, above 2400m altitude

free and consequently, relatively drier enhancing the (Ohsawa et al. 1985). In addition, it is rnore or less

optimum growth and development of the pure pine floristically related to the upper mossy forest region stand. (ca. 2400m to 250em altitude) of Mt. Apo (Fig. 4),

The lower montane mixed pine forest, i.e., the southern Philippines (Fig, 1>, On Mt. Makiling a

Pinus-Deuteia-Schqfi7era forest of Mt. Pulog at 23eOm dormant volcano, constriction of vegetation zones

to 2400m altitude

The difference however is on the associated species. elevations 900m to 1114m (Fig. 4) . In the very narrow

In northern Thailand, P. keslya is associated mainly but typical mossy forest zone of Mt. Makiling

with Fagaceae (700m to 1800m altitude) and to a (Brown, 1919, Trelease & McLean 1919) while on Mt. lesser degree with Dipterocarpaceae (800 m to 1200m Apo, another dormant mountain volcano,

altitude) (Santisuk 1988). On Mt. Pulog, R heslya is Rhododendron-Vizccinium communities descend at

associated mainly with Saxifragaceae, Araliaceae and 2400m to 250em altitude (Fig. 4) due to the effects of

Lauraceae (Table 1) though in higher elevations (ca sulfuric emissions near the summit crater (Schoenig, 2485m altitude) at sampling site 6 (Table 1) PL keslya et al. 1975, Numata 1971).

was associated with Fagaceae. It is evident in the aforementioned discussion and in

The lower montane Lithocampus-DaciycaiPus- Fig. 4 that the altitudinal zonal rimits between the

S,aygium-Loplospemaum forest (zone II) of Mt, Pulog lower and upper rnontane vegetation zones vary with

(Fig.4) has floristic equivalents on Mt. Wilhelm difierentmountains. This had also been the observa-

and of and (Wade & McVean 1969, Johns 1982) Mt. tions Grubb (1974), Whitmore (1984), Grubb Kinabalu (Kitayama, 1987, 1991, 1992). The Aus- Stevens (1985) and Richards <1996) . On Mt. Pulog,

tralasian species, Dac71;carpus and Ler)tospermum are the boundary line is at ca. 2600m altitude. On Mt.

also dominant elements in the mentane zone of these Makiling, it is at ca, 900m altitude while on Mt. Apo

mountains. Dacitycarptts, which was observed to occur it is at ca. 2400m altitude (Fig. 4). On Mt, Kinabalu

in the lower montane forest at 24eem to 260em alti- the boundary between the lower and upper montane is

tude on Mt. Pulog had been reported to occur on Mt. at ca. 2100 m altitude (Kitayama 1987) while on Mt.

Kinabalu, Borneo in the lower montane forest at ca. Wilhelm it is at 3000m altitude (Grubb 1974). In

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Malayan mountains, the boundary line is at ca. 1500 m (UPLB), for allowing their research staff, Ms. M.A, altitude (Whitmore 1984). On Mt, Kerinci (Sumatra), Cajano and Ms. N. Orlido to serve as guides and to

the boundary line is at 2370m altitude whereas on Mt. Forester G. S. Fianza, Mr. D. B. Caranto and Ms. G. I.

Pangrango (Java), the boundary line is at 2300m Solano of the Department of Environment and Natu-

altitude (Ohsawa 1991). These variations chiefly ral Resources (DENR), Benguet, Philippines for giv-

depend on the Massenethebung or mass elevation ing the permit to do some fieldworks and access to

effects (Grubb 1974, Richards 1996). Hence in larger some park records. Mr. H. Cayat, Mr. R. Lupos and

and higher mountains the boundary line is on higher Mr. S. Nayosan of DENR facilitated the field survey.

altitudes compared with smaller mountains. Mr. B. F. Hernaez of the Herbarium of the MNH-

UPLB, helped in plant identification. Dr. J. F. Veld- CONCLUSION kamp, editor of the Flora Malesiana Bulletin, Rijk-

The peculiarity of Mt. Pulog lies on the occurrence sherbarium, Leiden, The Netherlands, confirmed the

of a number of northern types Pint{s, Skimmia. nax validity of the botanical names listed in Table 1 and

and others) in the altitudinal forest vegetation zones gave encouragement through his fruitful discussions.

of the montane forest which cannot be observed in Dr. Koji Shimano of Yokoharna National University

other Philippine mountains. The Pinzas keslya forest at contributed valuable suggestions and discussions. The

2000 m to 2400m altitude in the lower montane zone of Japanese Ministry of Education, Science, Culture and

Mt. Pulog (zone I ) is floristically similar to the pine Sports awarded the senior author a graduate scholar-

forests in northern Thailand, Burma, Vietnam, ship. Chittagong (Bangladesh) and in Assam (India). The REFERENCES extensive lower montane mossy forest at 2300m to

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The authors are grateful to Dr, N. O. Aguilar and interpretation of the present range of distribution Dr. A. C. Sumalde, of the Museum of Natural History and dispersal of Ochrosia ofipositijblia (Lam.) K. University (MNH), of the Philippinesat Los Banos Schum.

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est. Tech. Bull. Fac. Hort. Chiba Univ., 51: 119u126. Manila.

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Shannon C． E ．＆ Weaver W ．1949 ． The Mathemati − ，，摘要 cal Theory of Communication． Univ． Illinois Press，・ Illinois．フィリピンルソン島のプログ山において植生垂直分

Sneath P． H ． A ．＆ Soka1 R． R ．1973 Numerical 布を記述した植地理ふ，，，．物学的特性をまえて，それらを

Taxonomy ． Freeman ， San Francisco．他の熱帯山地のものと比較．しプログ山での特徴を検討し

Stamp L． D ．1925 The ；たのつの，． Vegetationof Burma From ．以下三植生帯が認められた．1 ．Pinus林（2000

an ． and ． − − − EcologicalStandpointThacker， Spink Co ， 2400m ．2eOO 23eOm は Pinus 純林，2300 2400m は Calcし1tta 、 Pinus −1）eutzia −Schefflera林）， 2 ．LithocarPus − Sugden A ． M ．1982 The vegetation − − − ，． of the Serraniade DacrycarPusSyzygium LePtosPeγ7num 林（2400 260e ・ − Macuira， Guajira， Colombia： acontrast of arid low m ）， 3 ．Rhododendron−Clethra−E ％嬲林（2600 2700

lands arld an isolatedcloud forest．Journ．Arnoid m ）．プログ山では，北方の温帯要索（Skimmia ， Pinus， − Arboretum，63： 1 30． llexなど〉が多く出現するため，フロラの特徴は，ルソン

Tanaka Y ．＆ Tarumi T ．1995 Handbook − のフピンのい，，． of Statisti 島南部や他ィリ山地とは異なってた．標高 cal Analysis： Multivariate Analysis． Kyoritsu Pub ．が増加するにつれて，種数，多様性，胸高直径，樹高な Corp． Tokyo in ，（ Japanese）．どは減少する傾向にあった．垂直上部の植生帯における

Trelease S ． F ．＆ McLean F ． T の，，，1919．Mt ．Makillng 林冠優占種多くは垂直下部の植生帯における林床構成

as a station for botanical っ research ．Phil．Agric．，8： 6 要素であた．各植生帯の境界ははっきりしており，他 − 16．ののにの熱帯 ll亅地よう漸次的に変わるもではなかった．

van Steenis， C． G ． G ． J．1972 ．The Mountain Flora of プログ山はの温フロの，北方帯ラ南限であり，また熱帯

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