ARTICLE IN PRESS
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Quaternary International 147 (2006) 16–33
Pollen stratigraphy, vegetation and environment of the last glacial andHolocene—A record from Toushe Basin, central Taiwan
Ping-Mei Liewa,�, Shu-Yue Huangb, Chao-Ming Kuoc
aDepartment of Geosciences, National Taiwan University, 1, Sec. 4, Roosevelt Rd. Taipei 106, Taiwan, ROCbDepartment of Life Science, National Taiwan University, 1, Sec. 4, Roosevelt Rd. Taipei 106, Taiwan, ROC
cChinese Petroleum Corporation, 3, Sung Ren Rd, Taipei 11010, Taiwan, ROC
Available online 9 November 2005
Abstract
The pollen record from the Toushe Basin (231490N; 1201530E; 650m above sea level), a peat bog of central Taiwan, displays a
continuous vegetation history of the past 96,000 yrBP of monsoon Asia. Instead of today’s closed subtropical evergreen broadleaved
forest dominated by Machilus–Castanopsis surrounding the basin, temperate deciduous forest predominated during most of the last
glacial. In early MIS 4, Alnus reaches the highest value of the whole sequence (60–70%) representing temperate deciduous forest and
relatively cold and arid conditions. Following this stadial, Alnus and herbs (mainly Cyperaceae) dominated alternately, with a minor
increase of Castanopsis. Peaks of monolete spores between cal. 42.2 and 37.0 kyr BP (kyr BP represent calibrated years) indicate episodic
wet conditions. The later glacial, especially between 23.2 and 18.7 kyrBP, shows a high percentage of Gramineae, indicating dry and
possibly sometimes cold conditions. The late glacial shows a remarkable increase of warm-temperate to temperate forest elements, such
as Ilex, Cyclobalanopsis and Symplocos. At about 15.1 kyrBP a peak of monolete spores indicates wet–warm conditions. A subsequent
sharp increase of Salix and then Gramineae between 13.0 and 11.6 kyr BP corresponds to the Younger Dryas. A warming event at
11.5 kyr BP is also evident. The Holocene is characterized by warm–wet conditions of the overwhelmingly abundant monolete spores
since 10.7 kyr BP and the prominent increase of Castanopsis.
r 2005 Elsevier Ltd and INQUA. All rights reserved.
1. Introduction
Toushe Basin (231490N; 1201530E; 650m above sea level),a 1.75 km2 desiccated peat bog in the low hills of centralTaiwan, is one of a series of north–south trending middlePleistocene tectonic basins along the island’s backbone(Fig. 1). To the north lies Sun-Moon Lake (or Jih-YuehTan, 750m above sea level) where a pollen sequencecovering time since the last glacial has been reported byTsukada (1967). Mountains surrounding these basins rangein altitude from 700m to higher than 1000m eastward. Thefluvial and lake deposits in Toushe Basin are about 80mthick. The bog became desiccated at about 1.8 kyr BP.
In the context of global climate, changes in low-latitudeareas have the same importance as those at high latitudes.Marine records of the last glacial from offshore Taiwanshow that low-latitude sea-surface temperature is not as
e front matter r 2005 Elsevier Ltd and INQUA. All rights re
aint.2005.09.003
ing author. Tel.: +886 2 33662932; fax: +886 2 23636095.
ess: [email protected] (P.-M. Liew).
warm (Huang et al., 1997) as previously estimated byCLIMAP (1981). This is also shown for other low-latitudeterrestrial areas (Flenley, 1979; Hooghiemstra, 1989;Farrera et al., 1999). On the other hand, a chronologicaldiscrepancy of climatic events between the two poles isrecognized (Sowers and Bender, 1995). Thus, the latitu-dinal variations of regional climates should be betterunderstood before attempting to interpret the globalfeatures of climate change, even though the climateconditions of higher latitude since the last glacial havebeen well documented. The tropical–subtropical record iscrucial in understanding the driving force of climate changefrom a global point of view (Stock, 1999). Recent studiesfrom the stalagmites of Hulu Cave (China) show that thetiming of changes in the monsoon generally agrees with thetiming of temperature changes from the Greenland ice coreGISP2 (Wang et al., 2001). This indicates that the EastAsian monsoon is integral to millennial-scale changes inatmosphere/oceanic circulation patterns and is affectedby orbitally induced insolation variations. Remarkable
served.
ARTICLE IN PRESS
Fig. 1. Location map of the studied site with the climate conditions of Sun-Moon Lake.
P.-M. Liew et al. / Quaternary International 147 (2006) 16–33 17
vegetation and climate changes during glacial time in thesubtropical island of Taiwan were found in a previousstudy of Sun-Moon Lake (Tsukada, 1967). According tohis study, by excluding Alnus pollen, an early stadial atsome time subsequent to 60,000–50,000BP contains pre-dominantly boreal conifers and pine and a low percentageof temperate elements, indicating a temperature decrease of8–11 1C; the period from about 50,000 to 10,000 BP isdominated by cool-temperate species. However, there areonly four radiocarbon dates in the core and a detailedrecord of climate change is not available. It is important toobtain a high-resolution pollen record with good agecontrol from the last glacial in Taiwan so as to reveal thesynchronism (or not) of global climate events. Thus, theToushe Basin was chosen for a study of its palynostrati-graphy. We use biomization of fossil pollen assemblages asproposed by Prentice et al. (1992, 1996) and used for thereconstruction of vegetation in Europe, Africa and Asia todiscuss the climatic conditions of the stadials andinterstadials of the last glacial and Holocene based onthe record of surface pollen assemblages of the naturalforests nearby in the Salixian area (Jolly et al., 1998;Tarasov et al., 1998; Yu et al., 1998; Allen et al., 2000;Takahara et al., 2000; Gotanda et al., 2002). We aim todescribe the vegetational changes quantitatively so asto interpret the magnitude of possible environmentalchanges. The simplified pollen diagram of the upper 17mof this site has been published previously (Liew et al., 1998;Kuo and Liew, 2000), but data to 39.5m depth will bedescribed here.
2. Modern vegetation and climate of the study area
Taiwan is a subtropical mountain island whose climate isdominated by the East Asian monsoon. Warm–wetsummers and cool-relatively dry winters prevail and the
whole island is generally humid. According to themeteorological data near the study site (Fig. 1), the Sun-Moon Lake Station (altitude 1014m) immediately north ofthe Toushe peat bog, mean annual rainfall is 2341mm,annual evaporation is 1098mm and mean annual tempera-ture is 19.2 1C. The coldest month has an averagetemperature of 13.9 1C, whereas the warmest month is23.6 1C, with an average of 155.6 rainy days. The estimatedmean annual temperature of Toushe is 21.2 1C, the lapserate being 0.54 1C/100m. The present vegetation surround-ing the study area belongs to the subtropical evergreenLauro-Fagaceae forest. This forest consists mainly ofMachilus kasanoi, M. zuihoensis, Beilschmiedia erythrofolia,Phoebe formosana, Sapium discolor, Michelia formosana,Cyclobalanopsis flauca, Pasania uraiana, P. konishii,P. ternaticupula, P. brebicaudata, Ardisia sieboldii, Zelkova
fomosana, Engelhardtia roxburghiana, Glochidion hongkon-
gensis, Trema orientalis, Liquidambar formosana, Rhus
succedanea, Schefflera octophylla, Castanopsis hystrix,Quercus variabilis, Fraxinus formosana, Lagerstroemia
subcostata, Symplocos theophrastaefolia and Sapindus
mukorosii among others (Lin et al., 1968).Tsukada (1967) described the vegetation of mountain
forests above the nearby subtropical forest as follows:
�
Warm-temperate forest (ca. 500–1800 m): Dominatedby Castanopsis, Lithocarpus, Cyclobalanopsis and Cin-namomum with other broadleaved species and withconifers such as Keteleeria and Podocarpus species. Theundergrowth is crowded with ferns and mosses.
� Cool-temperate forest (ca. 1800–2400 m): Composed ofdeciduous hardwood species of Cyclobalanopsis, Ulmus,Zelkova, Juglans, Carpinus and others, mixed withconifers including Chamaecyparis. Cyclobalanopsis andthe Chamaecyparis species form two separate associa-tions but both groups occupy the misty climate belt.
ARTICLE IN PRESSP.-M. Liew et al. / Quaternary International 147 (2006) 16–3318
�
Subalpine coniferous (or boreal) forest (ca. 2400–3500 m):Composed of Tsuga chinensis, Abies kawakami andPicea morrisonicola mixed with Pinus armandii. Aboveabout 3300m, alpine shrubs and herbs occur.Su (1984) studied the vegetation in the mountains ofcentral Taiwan and identified the following altitudinalzones (Fig. 2) with annual temperature range:
(1)
Ficus–Machilus Zone (below altitude 500m; 23–26 1C;tropical): Lowland evergreen broadleaved forest in-cluding species of Ficus and Machilus.(2)
Machilus–Castanopsis Zone (500–1500m; 17–23 1C;subtropical), submontane evergreen broadleaved forestwith two major types: 1. Castanopsis type: mainlycomposed of Castanopsis hystrix, C. Kawakamii,Schima superiba, Engelhardtia, Lithocarpus and 2.Machilus type: mainly Machilus japonica, M. kusanoi,Ficus, Lagerstroemia and tree fern species.(3)
Lower Quercus Zone (1500–2000m; 14–17 1C; warmtemperate), with major components Cyclobalanopsislonginus, C. gilva, Lithocarpus and Litsea species.
(4) Upper Quercus Zone (2000–2500m; 11–14 1C; tempe-rate), with major components Cyclobalanopsis morii,
Fig. 2. Present vegetational zone in mountain ar
C. stenophylloides, Trochodendron and Castanopsis
carlesii.The Upper Quercus Zone is often mixed with montanemixed coniferous forest including Chamaecyparis,Pinaceae and Taxodiaceae, although they may separateinto associations. When local conditions are less humid,montane deciduous broadleaved forest appears inQuercus Zone including species of Acer, Juglans,Ulmus, Carpinus, Platycarya and Quercus. Whenaridity increases Alnus formosana prevails in this zonealthough this tree may appear at altitudes between 900and 2600m. However, Alnus with Salix, Carpinus andAcer frequently appear near 2000m, whereas Alnus
associated with Urticaceae usually occurs below thisaltitude. In addition, Pinus exists in the still drierconditions of this zone.
(5)
Tsuga–Picea Zone (2500–3100m; 8–11 1C; cool tempe-rate), with major components Tsuga chinensis, Piceamorrisonicola and Pinus armandii mastersiana.
(6) Abies Zone (3100–3600m; 5–8 1C; cold temperate),mainly Abies kawakami. Beyond 3300m, alpine shrubsand herbs are scattered.
(7)
Alpine vegetation (43600m; o5 1C; cold), mainlyGramineae with some Juniperus.ea, central Taiwan (after Su, 1984).
ARTICLE IN PRESSP.-M. Liew et al. / Quaternary International 147 (2006) 16–33 19
In an effort to elucidate the fossil sequence of Toushe, apreliminary study was made of the surface pollenassemblages of the natural forest in Salixian(231280–231330N; 1201530–1201590E), 30 km southeast ofthe Toushe site (Liew and Chung, 2001). This area includesthe Machilus–Castanopsis Zone, Lower and Upper Quercus
Zones and Picea–Tsuga Zone (Fig. 2) of Su (1984) betweenaltitudes 700 and 2800m (Chung, 1994). Pollen assem-blages above 2500m, the Picea–Tsuga Zone, are dominatedby Pinus, Tsuga and Picea. Below 2500m, in the Upper andLower Quercus Zones, pollen assemblages are morecomplex. Between 2500 and 2250m, an Alnus-dominantpollen assemblage appears while below 2250m Castanop-
sis-dominant pollen assemblages are common. Cyclobala-
nopsis pollen is expected to prevail in the Quercus Zone ifsampling in different parts of this zone is wide enough tocover more associations of this zone. Nevertheless, theUpper Quercus Zone may sometimes also be representedby a Castanopsis-dominant pollen assemblage associatedwith Cyclobalanopsis and Alnus, even though Cyclobala-
nopsis is common in this zone. This is possibly becausesome of the prevailing genera in the zone belong to theCastanopsis pollen types, such as Castanopsis carlesii.
Castanopsis-type pollen includes Castanopsis, Lithocarpus
and Pasania, totaling 26 species. However, Castanopsis-
dominant pollen assemblages in the Quercus Zone (above1500m) can still be differentiated from those of theCastanopsis–Machilus Zone (below 1500m) if there existsignificant associated elements in the pollen assemblages.The latter are characterized by Castanopsis associated withsubtropical to warm-temperate elements such as Elaeocar-
pus, Diospyros and Euphorbiaceae, and abundant spores,which are different from those of the Castanopsis-dominantassemblages at higher altitudes.
3. Methods
3.1. Chronology
The 39.5-m-long core was taken in the center of thissmall, rectangular basin. The sediment from 39.5 to 32.8mdepth is clay. The upper 32.8m is mainly peaty sedimentsintercalated with thin layers of clay or gyttja except forbackfill in the top 0.3m. Each sample for analysis wasabout 1 cm3, with an average sampling interval of 9 cm.The total number of samples is 395, yielding 114 pollentaxa. Thirty-one radiometric analyses were performed,including three AMS and 28 radiometric 14C dates. Eachsample for conventional 14C dating was 6–10 cm in length.The sedimentation rate is relatively constant, as shown inFig. 3. Ages of sediments beyond the limit of 14Cradiometric dating are extrapolated by tentatively correlat-ing the Alnus-dominant interval with MIS 4 (MIS 3/4,23.3m and MIS 4/5a, 26.5m) (Martinson et al., 1987). Thishigh Alnus-interval, representing cold/dry conditions, ismost likely to correspond to MIS 4. It contrasts with thelayer beneath where less cold and less dry elements, i.e.
Castanopsis or Cyperaceae, are still significant. The bottomof this core at 39.5m is estimated as 95.2 kyr BP by theleast-squares equation shown in the figure, and the ages ofdepths between 39.5 and 26.5m are then extrapolated.
3.2. Vegetation reconstruction
Yu et al. (2002) transferred the surface pollen assem-blages of Salixian (Liew and Chung, 2001) into modernvegetational types by the biomization technique (Prenticeet al., 1996) by which vegetation can be described bybiomes and major vegetation categories defined on thebasis of their dominant plant functional types (PFTs).However, the ecological reference is not as complete at thattime as it is at present and the results show overlapsbetween the upper boundary of subtropical/warm tempe-rate and also between warm-temperate/temperate vegeta-tion types. In this study, we slightly modified (Tables 2 and3) the previous work of Yu et al. (2002) with reference tothe altitudinal vegetational zones of Su (1984) (Fig. 2) andalso to newly available ecological data (Editorial Commit-tee of the Flora of Taiwan, 1993, 1994, 1996, 1998, 2000).For example, PFT sut are those broadleaved evergreenplants that appear in subtropical evergreen forest (Machi-
lus–Castanopsis Zone of Su; 500–1500m in altitude centralTaiwan). We attempted to name biomes by following theaforementioned altitudinal zones proposed by Su (1984).Thus, the tropical evergreen forest corresponds to theFicus–Machilus Zone (o500m; 423 1C) and subtropicalevergreen forest to the Machilus–Castanopsis Zone(500–1500m; 17–23 1C); warm-temperate evergreen forestto the Lower Quercus Zone (1500–2000m; 14–17 1C) andtemperate broadleaved and conifer mixed forests (com-prised of the montane evergreen forest, montane mixedconiferous forest; montane deciduous forest) to the UpperQuercus Zone (2000–2500m; 11–14 1C); cool-temperateconiferous forest to the Tsuga–Picea Zone (2500–3100m;8–11 1C). We also included in the biome list the tropicalrain forest occurring in southern but not in central Taiwan,and for the biomes absent in Taiwan we followed Yu et al.(2002), and Editorial Committee of the Vegetation ofChina (1980) as a reference to forest steppe.A test of modern forest reconstruction is carried out by
using the same set of surface pollen assemblages in Salixianthat was used by Yu et al. (2000). We apply two strategieswhen assigning Castanopsis-type pollen in PFTs: (1)include Castanopsis in PFTs sut and wte2, i.e. insubtropical and warm-temperate forests since Castanopsis
is the main forest element of subtropical and warm-temperate forests; (2) include Castanopsis in PFTs sub,wte2 and wte1, i.e. in subtropical, warm temperate and alsotemperate broadleaved and conifer mixed forests, sincefour of 26 species of Castanopsis-type pollen grow intemperate broadleaved and conifer mixed forests. Amongthe 16 sites between altitudes 700 and 2800m in theSalixian area, the result of strategy (1) shows two sitesincorrectly assigned (altitudes 2000 and 2150m: temperate
ARTICLE IN PRESS
Fig. 3. Ages and information used to establish age–depth relations at Toushe bog. Radiocarbon yr were converted to calendar yr (kyr) by use of refs Bard
et al. (1998) and Stuiver and Reimer (1993).
P.-M. Liew et al. / Quaternary International 147 (2006) 16–3320
broadleaved and conifer mixed forests are incorrectlyassigned to warm temperate evergreen forest). The resultof strategy (2) shows three sites incorrectly assigned(altitudes 1500m: warm-temperate forest incorrectly as-
signed to temperate broadleaved and conifer mixed forest;1780m: warm-temperate forest incorrectly assigned tosubtropical forest; 2150m: temperate broadleaved andconifer mixed forests incorrectly assigned to subtropical
ARTICLE IN PRESSP.-M. Liew et al. / Quaternary International 147 (2006) 16–33 21
forest). In Japan, Gotanda et al. (2002), followingTakahara et al. (2000), studied the reconstruction of forestsby surface pollen samples. They improved the reconstruc-tion of present forests by assigning Fagus to temperatedeciduous forest instead of several forest types andexcluding Gramineae. For the biomization of the Toushefossil pollen sequence, we use strategy (1) based on thebetter results of the modern forest reconstruction inSalixian, by assigning Castanopsis in subtropical andwarm-temperate forests (Tables 2 and 3).
4. Palynostratigraphy of the Toushe bog
4.1. Palynological zones
The pollen zones are described as follows and also inTable 1. The percentage of each pollen genus is based onthe total pollen sum, whereas that of spores is based on thesum of pollen and spores (Figs. 4.1 and 4.2). In thefollowing discussion, years (e.g. 2.9 kyr BP) representcalibrated years, and 14C years are expressed as 2900 yr BP.
Zone 20 (39.5–39.0 m, tentatively estimated as 95.2–
94.4 kyr BP): arboreal pollen (AP) is about 70% in whichCastanopsis is dominant (460%). Other associated ele-ments are Cyclobalanopsis, Quercus and Symplocos.
Zone 19 (39.0–37.2 m, tentatively estimated as 94.4–
91.4 kyr BP): AP still prevails but Cyperaceae and Grami-neae continuously increase. Among the AP, Castanopsis
and Salix are the most important. Associated elementsare Quercus and Cyclobalanopsis. Compared with theprevious zone, Salix increases to more than 20% at theexpense of Castanopsis. Liquidambar and Ilex values alsoincrease.
Zone 18 (37.2–35.6 m, tentatively estimated as 91.4–
88.8 kyr BP): is characterized by an abrupt increase ofPteridophytes (460%). AP is dominant, Symplocos
(450%) and Myrica (25%) being the most common ones.Zone 17 (35.6–30.5 m, tentatively estimated as 88.8–
80.5 kyr BP): AP reaches 60%, slightly less than in theprevious zones in which the major element Castanopsis
(20–40%) again reaches its dominant situation. Myrica
reaches 15% in the lower part. Cyperaceae increase upwardto 30%.
Zone 16 (30.5–29 m, tentatively estimated as 80.5–
78.0 kyr BP): is characterized by a sharp decrease ofCastanopsis, from 40% to o15%, and herbs outnumberarboreal pollen for the first time. Cyperaceae increase to40% or more, whereas Salix increases remarkably in theupper part at the expense of Cyperaceae.
Zone 15 (29–28.2 m, tentatively estimated as 78.0–
76.7 kyr BP): exhibits remarkable changes in both APand NAP (non-arboreal pollen). AP dominates in this zone(80%) but instead of Castanopsis, the major tree pollen areIlex (40%) and Alnus (up to 70%). Alnus reaches its climaxfor the first time in this sequence. Castanopsis is at about5%, even less than in Zone 16, and is lower than
Cyclobalanopsis. Cyperaceae decrease sharply, while theArtemisia content rises slightly.
Zone 14 (28.2–26.5 m, tentatively estimated as 76.7–
73.9 kyr BP): Cyperaceae dominate in the lower part. Alnus
sharply decreases while Cyclobalanopsis increases. In theupper part Alnus reaches 40%. Cyclobalanopsis (about15%) is higher than Castanopsis and maintains this trendduring the glacial. Artemisia is relatively higher in Zones 14and 15.
Zone 13 (26.5–23.3 m, tentatively assigned as 73.9–
59.0 kyr BP): AP dominates (480%) with Alnus as themajor component (generally 60% or more). Salix increaseswhile Cyclobalanopsis decreases in comparison with theprevious zone. Cyperaceae decrease as well. Pinus decreasesfrom Zone 15 upward.
Zone 12 (23.3–23 m), tentatively estimated as 59.0–
57.6 kyr BP: is characterized by a decrease of Alnus
(20%) and Salix and the increase of Ilex (from o5% to425%).
Zone 11 (23.0–22.4 m, tentatively estimated as 57.6–
54.0 kyr BP): Alnus predominates again (60%). Comparedwith Zone 13, Castanopsis and Symplocos increase at theexpense of Salix. Symplocos occasionally increases inZones 11 and 12.
Zone 10 (22.4–21.0 m, tentatively estimated as
54.0–48.5 kyr BP): Alnus decreases remarkably to about40% or even less, although it is still the main component ofAP. Cyclobalanopsis and Castanopsis are relatively sig-nificant, similar to the last two zones 12 and 11. Ilex andSymplocos decrease. Cyperaceae dramatically increaseagain. Castanopsis is relatively higher from Zones 12 to10, after its decrease to a very low value in Zone 13.
Zone 9 (21.0–18.4 m, tentatively estimated as 48.5–
36.9 kyr BP): Alnus has the same amount as in Zone 10but peaks at the middle. Cyperaceae frequently fluctuate atthe expense of Alnus. The most notable feature is theincrease of Pteridophytes, especially monolete spores. Salix
increases episodically in this zone. Castanopsis decreasesslightly and maintains the trend from this zone upwarduntil the beginning of the Holocene. Ilex is common fromZone 12 upward.
Zone 8 (18.4–16 m, cal. 36.9–31.2 kyr BP; 14C years,
41,100–31,600 yr BP): Pteridophytes and Cyperaceae de-crease sharply. Compared with the previous zone Alnus
and Ilex increase while Cyclobalanopsis decreases. Grami-neae increase slightly.
Zone 7 (16–14.6 m, 31.2–27.9 kyr BP; 31,600–23,900 yr
BP): Cyclobalanopsis slightly increases. Alnus is stilldominant with a level similar to the previous zone. Ilex
and Symplocos decrease. Castanopsis increases slightly.Alnus is relatively low but with remarkable fluctuationsfrom Zones 10 to 7.
Zone 6 (14.6–13.8 m, 27.9–27.4 kyr BP; 23,900–23,400 yr
BP): compared with Zone 7, Alnus increases clearly.Cyclobalanopsis, Castanopsis, Quercus, Ligustrum andSalix decrease. Artemisia decreases slightly. Zones 6–12are assumed to belong to MIS 3.
ARTICLE IN PRESSTable
1
Toushebogpollen
zones
withinferred
paleovegetationandpaleoclim
ate
Zonedepth
andage
OIS
andage
Characteristics
Paleovegetation
Paleoenvironment
1b(1.4–0.3m)3.8–1.8kyrBP
1Herbaceouspollen
rise
(70–80%
).Increase
inL
iqu
ida
mb
ar;decrease
in
Cy
clo
ba
lan
op
sis,
Ilex.CyperaceaeandGramineaefrequent.Increase
in
pteridophytes
Grassland
Subtropicalto
warm
temperate,wet
1a(2.5–1.4m)5.7–3.8kyrBP
0–12.1kyr
Herbaceouspollen
increase.Increase
inS
ali
x,
Sy
mp
loco
s,Il
ex;decrease
inM
all
otu
s.Increase
inCyperaceae
Subtropicalforest
but
fluctuated
Fluctuatedsubtropicalto
temperate
2c(3.1–2.5m)6.3–5.7kyrBP
Increase
inIl
ex,
Lig
ust
rum;decrease
inP
inu
s.Decrease
inCyperaceae
andpteridophytes
Subtropicalto
tropical
forest
Subtropical,less
wet
2b(3.9–3.1m)7.0–6.3kyrBP
Increase
inGramineaeandCyperaceae,
Sa
lixpeaksatfirstandthen
decrease.Increase
inP
inu
s.Increase
inpteridophytes(to50%)
Subtropicalforest
mainly
Subtropical,wet
2a(4.7–3.9m)8.0–7.0kyrBP
Woodytaxasum
increase
slightly.Increase
inIl
exand
Mall
otu
s,S
ali
x
peakatearlypart.Sharp
decrease
inpteridophytesandCyperaceae
Subtropicalforest
but
fluctuated
Fluctuatedsubtropicalto
temperate
less
wet
3(7.10–4.7m)11.0–8.0kyrBP
Woodytaxasum
decreases(to40%
).Increase
inC
ast
an
op
sis,
Tre
ma,
Pin
us;decrease
inC
ycl
ob
ala
no
psi
sand
Sy
mp
loco
s.S
ali
xvaries;peakof
Ilex
atmiddle.Increase
inCyperaceaeandGramineae,sharp
increase
in
pteridophytes
Subtropicalto
warm
-
temperate
forest
Subtropicalto
warm
temperate,wet
4d(7.6–7.10m)11.9–11.0kyrBP
Increase
inC
ycl
ob
ala
no
psi
s,S
ym
plo
cosand
Sa
lix;increase
in
Gramineae(to40%)
Tem
perate
tosubtropical
forest
Tem
perate,less
dry
4c(9.2–7.6m)14.5–11.9kyrBP
WoodytaxaA85%
.Increase
inS
ali
x,
Sy
mp
loco
s.Decrease
in
Cyperaceaeand
Art
emis
ia.Gramineaeislow
butpeakatend.Decrease
inpteridophytes
Tem
perate
forest
Tem
perate,less
dry
4b(9.8–9.2m)15.7–14.5kyrBP
2Woodytaxasum
varies,increase
inA
lnu
s.Increase
inCyperaceae.
Sharp
increase
inpteridophytes
Warm
-tem
perate
forest
Warm
temperate,moistto
wet
4a(10.3–9.8m)16.7–15.7kyrBP
12.1–24.1kyr
Woodytaxarise
(to70%),decrease
inA
lnu
s;increase
inIl
ex,
Sym
plo
cos,
Cy
clob
ala
no
psi
s.Decrease
inCyperaceaeandGramineae
Tem
perate
forest
Tem
perate
less
dry
5(13.8–10.3m)27.4–16.7kyrBP
Decrease
ofwoodytaxapercentages,herbsrise
(to75%)ofpollen
sum,
Gramineaerise
(to50%
).Decrease
inA
lnu
s(to20%
);increase
in
Cy
clo
ba
lan
op
sis,
Ilex
,S
ym
plo
cos.Increase
inA
rtem
isia
(to10%),
Cyperaceae
Tem
perate
forest
toforest
steppe
Tem
perate,dry
6(14.6–13.8m)27.9–27.4kyrBP
WoodytaxaA80%
;increase
inA
lnu
s;decrease
inC
ycl
ob
ala
no
psi
s,
Ca
sta
nop
sis,
Qu
ercu
s,L
igu
stru
mand
Sali
x.Decrease
inCyperaceaeand
Art
emis
ia
Tem
perate
deciduousforest
Tem
perate
7(16–14.6m)31.2–27.9kyrBP
Woodytaxasum
varies
60–90%,
Aln
usfluctuatedatthecompense
of
Cyperaceae.
Increase
inC
ycl
ob
ala
no
psi
sand
Ca
sta
nop
sis.Increase
in
Sali
xattheearlypart;decrease
inIl
exand
Sy
mp
loco
s,peakin
Gramineaeatend
Tem
perate
deciduousforest
Tem
perate
8(18.1–16m)36.9–31.2kyrBP
3Woodytaxasum
increase
A80%
,A
lnu
svaries
andpeakatmiddle;
increase
inIlex;
Cy
clo
ba
lan
op
sisslightlydecrease;decrease
in
Cyperaceaeandincrease
inGramineae.
pteridophytesdecrease
sharply
Tem
perate
deciduousforest
Tem
perate,gettingdrier
9(21.0–18.4m)48.5–36.9kyrBP
27.6–58.9kyr
Woodytaxasum
fluctuates40–85%
,decrease
inC
ast
an
op
sis.
Fluctuationof
Aln
usatthecompense
ofCyperaceae.
Increase
in
Sym
plo
cos;tw
opeaksof
Sali
xatmiddle
andso
does
Ilex;increase
in
pteridophytes(to60%
)
Tem
perate
deciduousforest
Tem
perate,moistto
wet
10(22.4–21.0m)54.0–48.5kyrBP
Woodytaxasum
decreasesandthen
increases.Increase
in
Cy
clo
ba
lan
op
sisand
Ca
sta
no
psi
s.Decrease
inA
lnu
s(to40%),
Ilex,
Sym
plo
cos;Increase
inCyperaceae
Tem
perate
deciduousforest
Tem
perate,less
dry
11(23.0–22.4m)57.6–54.0kyrBP
WoodytaxaA80%,increase
inA
lnu
s(to60%);
Ca
sta
nop
sisthesameas
thepreviouszone.
Decrease
inIl
exand
Sa
lix.Increase
inGramineae
Tem
perate
deciduousforest
Tem
perate,dry
P.-M. Liew et al. / Quaternary International 147 (2006) 16–3322
ARTICLE IN PRESS12(23.4–23.0m)59.0–57.6kyrBP
4Increase
inIl
ex(to25%),
Ca
sta
nop
sis,
Sy
mp
loco
s.Decrease
inA
lnu
s(to
20%)and
Sa
lix
Tem
perate
deciduousforest
Tem
perate
13(26.6–23.4m)assigned
as
73.9–59.0kyrBP
58.9–73.9kyr
WoodytaxaA80%,mainly
Aln
us(to60%
),increase
inS
ali
x;1peakin
Sym
plo
cos;decrease
inC
ycl
ob
ala
no
psi
s.Decrease
inCyperaceae
Tem
perate
deciduousforest
Tem
perate,dry
14(28.2–26.6m)76.7–73.9kyrBP
Woodytaxasum
varies
30–70%,
Aln
usdeclinebutrisesatin
thelater
part(to40%
),C
ycl
ob
ala
no
psi
s(15%)higher
than
Ca
sta
nop
sis;decrease
inS
ali
x,increase
inCyperaceae(to50%),
Art
emis
iasimilarto
the
previouszone
Tem
perate
deciduousforest
Tem
perate,less
dry
15(29–28.2m)78.0–76.7kyrBP
5a?
WoodytaxaA80%;declinein
Ca
sta
nop
sis(to5%
)and
Sa
lix.Increase
inIl
ex(40%)andthen
Aln
us(70%),decrease
inP
inu
s,increase
in
Art
emis
ia,decrease
inCyperaceae
Tem
perate
deciduousforest
Tem
perate,gettingdry
16(30.5–29m)80.5–78.0kyrBP
73.9–85.1kyr
Woodytaxasum
varies
A40%,declinein
Ca
sta
nop
sis(15%).Increase
inS
ali
x(to40%
).Increase
inCyperaceae(to40%
)andGramineae
Tem
perate
deciduousforest
Tem
perate,moist
17(35.6–30.5m)88.8–80.5kyrBP
WoodytaxaA60%
butupto
80%
atlower,
Ca
sta
no
psi
svaries
(20–40%
).M
yri
cadecreasesupward.Increase
inCyperaceae(to30%
),
decrease
inpteridophytes(10%
)
Subtropicalto
warm
-
temperate
forest,less
closed
Subtropicalto
warm
temperate,less
wet
18(37.2–35.6m)91.4–88.8kyrBP
5b?
Woodytaxasum
varies
50–90%,declinein
Ca
sta
nop
sis(o
15%
),
increase
inS
ym
plo
cos(to50%)and
My
rica
(25%).Increase
in
Poly
go
nu
mandpteridophytes(to80%)
Tropicalto
subtropical
forest
Subtropical,wet
19(39.0–37.2m)94.4–91.4kyrBP
85.1–93.6kyr
Woodytaxasum
60–85%
,decrease
inC
ast
an
op
sis,increase
inS
ali
x(to
20%)andalso
Ilex,
Liq
uid
am
ba
rand
Lig
ust
rum.Increase
inGramineae
andCyperaceae
Tem
perate
forest
Tem
perate,moist
20(39.0–39.5m)95.2–94.4kyrBP
5c?
493.8kyr
WoodytaxaA70%
;dominanttaxais
Ca
sta
no
psi
s(to60%
).
Cy
clo
ba
lan
op
sis,
Qu
ercu
s,S
ym
plo
cosand
Pin
usalsosignificant;
Cyperaceaeabout20%,pteridophytesare
low
Warm
-tem
perate
forest
Warm
-tem
perate,moist
P.-M. Liew et al. / Quaternary International 147 (2006) 16–33 23
ARTICLE IN PRESS
Fig. 4.1. Pollen diagram for the Toushe Basin. Percentage of each pollen genus is based on total pollen sum.
P.-M. Liew et al. / Quaternary International 147 (2006) 16–3324
ARTICLE IN PRESS
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
2100
2200
2300
2400
2500
2600
2700
2800
2900
3000
3100
3200
3300
3400
3500
3600
3700
3800
3900
4000
Dep
th (
cm)
1840 ± 502230 ± 50
4230 ± 504410 ± 404800 ± 50
5640 ± 60
6480 ± 607370 ± 60
8780 ± 60
9600 ± 13010059 ± 8710309 ± 89
12100 ± 90
12350 ± 90
13700 ± 10013900 ± 10015200 ± 110
18150 ± 120
20500 ± 100
23400 ± 190
23900 ± 150
28000 ± 250
29300 ± 300
31100 ± 400
31600 ± 350
32800 ± 500
37200 ± 60039200 ± 600
8270 ± 70
>43000
>41000
>43000
>40000
>45000>41000
Age
(C
-14
yr B
P)
20
Artemisi
a
20
Polygo
num
Umbelli
ferae
20 40 60 80
Cypera
ceae
20 40 60 80
Gramine
ae
20 40 20 40 60 80 20 40 60 80 100
Zone
1b
1a
2c
2b
2a
3
4d
4c
4b4a
5
6
7
8
9
10
1112
13
14
15
16
17
18
19
20
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Subtropical evergreen forestWarm-temperate forest
Tropical evergreen forestTemperature deciduous and conifer mixed forest
Mon
olete
spor
eother
Trilete
spor
e
Potamog
etonac
eae
DCAaxis-1
BiomesLyg
odium
(%)
Fig. 4.2. Percentage of each spore genus is based on sum of pollen and spore. Reconstructed biomes plotted stratigraphically in relation to sample scores
on the 1st axis of a detrended correspondence analysis of the pollen data.
P.-M. Liew et al. / Quaternary International 147 (2006) 16–33 25
ARTICLE IN PRESSP.-M. Liew et al. / Quaternary International 147 (2006) 16–3326
Zone 5 (13.8–10.3 m, 27.4–16.7 kyr BP; 23,400–13,800
yr BP): NAP prevails in the middle and upper parts of thiszone in which Gramineae (up to 40% once in the upperpart) as well as Artemisia (at about 10%) reach theirhighest values. Alnus decreases remarkably to less than20% and Cyclobalanopsis increases slightly. Symplocos ishigher than in the previous zone but decreases graduallyupward in the upper part of this zone. This zone belongs toMIS 2.
Zone 4 (10.3–7.10 m, 16.7–11.0 kyr BP; 13,800–9700 yr
BP): differs from the previous zone remarkably. The forestelements rise again and NAP falls. AP increases to 80% inthe upper part. Cyclobalanopsis together with Ilex,Symplocos and Salix are the main woody elements.Gramineae decrease. Due to the abrupt change ofassemblages, the zone is divided into three subzones. Insubzone 4a (10.3–9.8m) Cyperaceae sharply decrease. Ilex,
Cyclobalanopsis and Symplocos increase. NAP is clearlylower. In subzone 4b (9.8–9.2m) spores increase abruptlyand Cyperaceae also increase. Alnus is higher and Ilex islower than in the previous subzone. Cyclobalanopsis
maintains the same level as previously. In subzone 4c(9.2–7.6m) spores decrease remarkably. Symplocos drama-tically increases in the lower part and Salix in the upperpart. Ilex is common. Herbs are relatively low. In subzone4d (7.6–7.1m) Gramineae rise to 40%. Salix reaches itshighest value in the upper part.
Zone 3 (7.10–4.70 m, 11.0–8.0 kyr BP; 9700–7200 yr BP):Pteridophytes are high. Castanopsis is dominant amongAP. Trema increases. Salix, Symplocos and Ilex arereduced. NAP increases again. It is probably hydrophyllusbecause of the accompanying large amount of fern-spores.AP is higher than NAP.
Zone 2 (4.70–2.50 m, 8.0–5.7 kyr BP; 7200–4900 yr BP):is characterized by the increase of Ilex and Mallotus.Pteridophytes reach their maximum value in the middlepart. Three subzones are distinguished here: In sub-zone 2a, Salix, Ligustrum (12–15%) and Ilex (25%)increase again. Cyclobalanopsis decreases. Cyperaceae arereduced. Pteridophytes decrease remarkably. Mallotus
appears from the middle part of this zone upward. Insubzone 2b Pteridophytes increase to maximum (ave-rage in 50%). Ilex decreases while Pinus increases. Insubzone 2c, Pinus is lower while Symplocos and Ilex riseagain. Herbs increase again. Ligustrum and Symplocos alsoincrease.
Zone 1 (2.50–0.30 m, 5.7–1.8 kyr BP; 4900–1800 yr BP):is characterized by the increase of Cyperaceae. Salix
increases but Ilex decreases. Herbs reach their maxi-mum values. Cyperaceae and monolete spores becomeimportant. This zone is further divided into two subzonesdue to the changing amounts of NAP. In subzone 1a(2.5–1.4m) Pinus is lower while Symplocos and Ilex riseagain. Salix increases but monolete spores decrease.Cyperaceae also increase upward. In subzone 1b (1.4mupward) Cyperaceae reach their maximum. Monoletespores increase as well.
4.2. Paleovegetation: a quantitative reconstruction
The characteristics of vegetation of pollen spectra fromToushe Basin appear in Fig. 4.2 according to PFTs andbiomes shown in Tables 2 and 3 with the biomes plotted onthe 1st axis of detrended correspondence analysis (DCA byTilia; Grimm, 1997). The results show that subtropicalevergreen forest dominated during the Holocene, incontrast to temperate broadleaved and coniferous mixedforests, specifically the temperate deciduous forest withinthem, during the last glacial.Vegetation reconstruction shows that the Castanopsis-
dominant pollen assemblages of the early glacial are mainlysubtropical to warm-temperate evergreen forests exceptZone 19. The warmest conditions are in Zone 18 (tropicaland subtropical forests) and the lower part of Zone 17(subtropical to warm-temperate forests). Thus, Zone 19,where temperate broadleaved and conifer mixed forestsprevailed, might correspond to MIS 5b. From Zones 16 to4, the temperate broadleaved and conifer mixed forests,especially the deciduous forest, dominated except for someintervals of the last glacial at cal. 41.6, 38.0 and 37.3 kyr BPand at 22.3 and 18.9 kyr BP as well as 15.1 kyr BP wherewarm-temperate evergreen forest or subtropical forestappeared. It shows a distinct interstadial at about42–37 kyr BP. The warm conditions occurred at 22.3 and18.9 kyr BP just before and within the dry phase (Grami-neae prevail) of the late stadial. However, due to highamounts of Gramineae in these samples, this result needsto be further discussed. Nevertheless, an abrupt warmphase around 22 ka is reported in the Siple Coast ofAntarctica (Taylor et al., 2004) and a warm phase very nearLast Glacial Maximum (LGM) is also reported in NewZealand (Hormes et al., 1999). Post-Bølling subtropicalconditions are found at 11.5 kyr BP. Thus, the subtropicalconditions of 15.1 kyr BP (depth 9.59m) and 11.5 kyr BP(depth 7.28m) of this study correspond to the spikes ofAtlantic melting events (Bond et al., 1992). After10.7 kyr BP, subtropical conditions continue. Tropicalforest appeared at 6.9 and 6.1–5.9 kyr BP. Temperatebroadleaved and conifer mixed forest appeared at about11.2–11.0, 7.5, 7.2 and 7.1, 5.2, 5.0 and 4.9 kyr BP. The coolinterval at 3.7–2.0 kyr BP which was found in alpine lakesof Taiwan (Liew and Huang, 1994) appeared here only as achange from subtropical to warm-temperate forests. Itindicates that it is a less prominent cooling than those inthe first half of the Holocene. Subtropical and tropicalforests are frequent from 8 to 5 kyr BP. Warm-temperateevergreen forest is common in early Holocene before8 kyr BP.However, the result of biomization shows that samples
with equal score of warm-temperate evergreen forest andsubtropical evergreen forest are common although theyshould be assigned as warm-temperate forest according tothe rule of less number of PFTs in biomization (among thesamples assigned as warm-temperate forest are almost withthe same score as subtropical forest except at depths 31.1,
ARTICLE IN PRESSTable
2
Assignmentofpollen
taxato
plantfunctionaltypes
(PFT)
PFTcode
Pollen
taxa
teF
icu
s,L
ith
oca
rpu
s,B
isch
offi
a,
Ho
ma
lan
thu
s,P
alm
ae,
Pip
erace
ae,
Tre
ma,
Alb
izzi
a,
Aca
cia,
Cel
tis,
Sch
effl
era,
Ard
isia,
My
rica,
Ela
eoca
rpu
s,S
loa
nea,
Ma
llo
tus,
Om
ala
nth
us,
Ma
cara
nga,
Mel
ano
lep
is,
Glo
chid
ian,
Da
phn
iph
yll
um,
Cit
rus,
Za
nth
ox
ylu
m,
Ch
lora
nth
us,
Sa
piu
m,
Mic
hel
ia,
Mel
ia,
Alg
aia,
Sy
zyg
ium,
Hel
icia,
Mel
iosm
a,
Sty
rax,
Wen
dla
ndia,
My
rsin
e,V
ibu
rnu
m,
Sy
mp
loco
s,L
igu
stru
m,
Sa
ura
uia,
Ilex,
Ka
nd
elia,
Rh
izo
ph
ora,
Lu
mn
itze
ra,
Dy
sox
yll
um,
Ara
lia,
Fra
xin
us,
Osm
an
thu
s,C
all
ica
rpa,
Cy
cas,
Lager
stro
emia,
Ma
esa,
Dio
spy
ros,Rutaceae,
Combretaceae,
Moraceae,
Leguminosae,
Proteaceae,
Melastomaceae,
Ulm
aceae
trD
iosp
yro
s,D
yso
xy
lum,
Ag
laia,
Alb
izzi
a,
Ter
min
ali
a,
Fic
us,
Sy
zyg
ium,
Bo
mb
aca
cea
e,B
om
ba
x,
Co
mb
reta
cea
e,E
up
ho
rbia
cea
e,L
egu
min
osa
e,M
ela
no
lepis,
Mic
rotr
op
is,Myrsinaceae,
Proteaceae,
Sapotaceae,
Ulm
aceae,
Ulm
us,
Wen
dla
nd
ia
sut
Cy
clo
ba
lan
op
sis,
Ca
sta
no
psi
s,L
ith
oca
rpu
s,P
asa
nia,
Cry
pto
cary
a,
Sch
effl
era,
Ard
isia,
My
rica,
Ela
eoca
rpu
s,S
loa
nea,
Pla
tyca
rya,
Mall
otu
s,D
ap
hn
iph
yll
um,
Mic
hel
ia,
Mel
iosm
a,
Ilex,
Dio
spy
ros,
Eng
elh
ard
tia,
My
rsin
e,S
chim
a,
Ma
esa,
Fra
xin
us,
Lig
ust
rum,
Osm
an
thu
s,P
run
us,
Call
icarp
a,
Act
inid
ia,
Sa
ura
uia,
Ca
pa
pa
ris,
An
aca
rdia
cea
e,A
rali
ace
ae,
Cit
rus,
Zel
ko
va,
Ch
lora
nth
us,
Ca
mel
lia,
Hel
icia,
Sy
mp
loco
s,S
yzy
giu
m,
Cel
tis,
Za
nth
ox
ylu
m,
Sa
piu
m,
Vib
urn
um,
Cy
cas,Moraceae,
Rhamnaceae,
Rubiaceae,
Rutaceae,
Ebenaceae,
Meliaceae,
Apocynaceae,
Euphorbiaceae,
La
ger
stro
emia
wte2
Cy
clo
ba
lan
op
sis,
Ca
sta
nop
sis,
Lit
hoca
rpu
s,Q
uer
cus,
Vib
urn
um,
Da
phn
iph
yll
um,
Sch
ima,
Ara
lia,
My
rsin
e,L
igu
stru
m,
Osm
an
thu
s,E
laeo
carp
us,
Tro
cho
den
dro
n,
Act
inid
ia,
Cle
yer
a,
Eu
rya,
Go
rdon
ia,
Pla
tyca
rya,
Den
dro
pa
na
x,
Illi
ciu
m,
Ilex,
Mel
iosm
a,schffleraMagnoliaceae,
Aaliaceae,
Hydrangeaceae,
Sym
plo
cos
wte1
Ilex,
Lig
ust
rum,
Cy
clob
ala
no
psi
s,Q
uer
cus,
Sho
rtia,
Vib
urn
um,
Tro
chod
end
ron,
Sy
mp
loco
s,P
run
us,
Act
inid
ia
ts1
Aln
us,
Rib
es,Ulm
aceae,
Sali
x
ts2
Ca
rya,
Aln
us,
Ela
eog
nu
s,F
ag
us,
Ju
gla
ns,
Liq
uid
am
ba
r,P
tero
cary
a,
Qu
ercu
s,S
ali
x,
Ca
sta
nea,
Ca
rpin
us,
Zel
ko
va,
Ulm
us,
Hel
win
gia,Ulm
aceae
ts3
Rh
us,
Zel
ko
va,
Lag
erst
roem
ia,
Sa
pin
du
s,P
laty
cary
a,
Sa
piu
m,
Tax
illu
s,C
elti
s,U
lmus,
Liq
uid
am
ba
r,T
rem
a,
Ko
elre
ute
ria,
Ter
min
ali
a,
Alb
izia,
Hel
win
gia,Ebenaceae.
Dio
spy
ros,
Fra
xin
us
tsA
can
tho
pa
na
x,
Ace
r,V
ibu
rnu
m,
Aln
us,Ulm
usRutaceae,
Rosaceae,
Rhamnaceae
ecP
inu
s,J
un
iper
us
wtc
Ket
elee
ria,
Pod
oca
rpus,
Ca
loce
dru
s,C
epha
lota
xis
tcC
ha
macy
pa
ris,
Cry
pto
mer
ia,
Cu
nn
ing
ha
mia,
Ta
iwan
ia,
Pin
us,Taxodiaceae
ctc
Pic
ea,
Tsu
ga
bec
Ab
ies
tef
Imp
ati
ens,
Mic
role
pia,
Cu
scu
ta,
Za
nth
ox
ylu
m,
Ru
ma
x,
Ch
eno
pod
ium,
Am
ara
nth
us,
Cle
ma
tis,
Ra
nu
ncu
lus,
Co
ccu
lus,
Ny
mp
ha
ea,
Hy
dra
ng
ia,
Ch
lora
nth
us,
Hy
per
icu
m,
Dro
sera,
Ara
bis,
Ka
lan
choe,
Sed
um,
Deu
tzia,
Pit
tosp
oru
m,
Ro
sa,
Ru
bu
s,S
an
guis
orb
a,
Rh
am
nu
s,C
issu
s,E
laeo
gn
us,
Beg
onia,
Act
inost
emm
a,
Mel
ast
om
a,
Bre
dia,
Epil
obiu
m,
Lud
wig
ia,
Tra
pa,
My
rio
ph
yll
um,
Hel
win
gia,
Sch
effl
era,
Tet
rap
an
ax,
Sho
rtia,
Ma
esa,
Ard
isia,
My
rsin
e,L
ysi
ma
chia,
Sty
rax,
Sy
mp
loco
s,G
enti
an
a,
Ga
liu
m,
Ca
llic
arp
a,
Call
itri
che,
Sola
nu
m,
Ju
stic
ia,
Str
ob
ila
nth
us,
Pla
nta
go,
Vib
urn
um,
Sa
git
tari
a,
Pota
mo
get
on,
Mu
sa,
Bry
op
hy
llu
m,
Typ
ha,
Sta
uto
nia,
Pip
er,
Act
inid
ia,
Lo
ran
thus,
Mic
rotr
op
is,
Wir
kst
roem
ia,Acanthaceae,
Gesneriaceae.
Gramineae
tfA
ctin
ost
ema,
Gen
tian
a,
Cu
scu
ta,
Ga
liu
m,
Po
lyg
onu
m,
Sta
uto
nia,
Hyper
icum,
Ara
bis,
Sed
um,
Deu
tzia,
Hy
dra
ng
ia,
Pit
tosp
oru
m,
Ro
sa,
Ru
bu
s,Im
pati
ens,
Euo
ny
mu
s,R
ha
mnu
s,E
laeo
gn
us,
Epil
obiu
m,
Sh
ort
ia,
Ly
sim
ach
ia,
Pri
mu
la,
Sy
mp
loco
s,S
wer
tia,
Pla
nta
go,
Lon
icer
a,
Cle
mati
s,L
ora
nth
us,
Mic
rotr
op
is,Cucubitaceae,
Gramineae,
Labiatae,
Ranunculaceae,
Rutaceae
Scrophulariaceae,
Solanaceae,
Umbeliferae
af
Po
lyg
onu
m,
Rh
od
od
end
ron,
Tha
lict
rum,
Sa
lix,
Act
inid
ia,
Ju
nip
erus,
Ch
eno
po
diu
m,
Cle
ma
tis ,
Ra
nu
ncu
lus,
Da
mn
aca
nth
us,
Eu
rya,
Ga
liu
m,
Ro
sa,
Lo
nic
era,
Sed
um,Cruciferae,
Ericaceae,
Compositae.
Ber
ber
is,
Rib
es
sfA
rtem
isia,
Ju
stic
ia,
Ru
bu
s
gGramineae,
Compositae
hEricaceae
sCyperaceae
wod
Sy
mp
loco
s,Q
uer
cus,
Ilex,
Cy
clob
ala
no
psi
s
Ferns(x)
Psi
lotu
m,
Lyco
po
diu
m,
Sel
agin
ella,
Eq
uis
etu
m,
Op
hio
glo
ssu
m,
An
gio
pte
ris,
Arc
ha
ng
iop
teri
s,M
ara
ttia,
Osm
un
da,
Lyg
od
ium,
Sch
iza
ea,
Dic
ranopte
ris,
Hem
enophyll
um,
Cib
oti
um,
Cy
ath
ea,
Den
nst
aed
tia,
Mic
role
pia,
Pte
ridiu
m,
Da
vall
ia,
Vit
tari
a,
Wo
od
ward
ia,
Dry
op
teri
s,D
ipte
ris,
Po
lyp
od
ium,
Azo
lla,
Cte
nit
is,
Dip
lazi
un,
Pla
gio
gyri
a,
Mic
roso
rium,
Sel
agin
ella
trx
Cyatheaceae
Key
toPFTcode:te,tropicalevergreen;tr,tropicalraingreen;sut,subtropicalevergreen;wte2,warm
-tem
perateevergreen;wte1,temperate
evergreen;ts1,cool-temperate
summergreen;ts2,interm
ediate-
temperate
summergreen;ts3,southernwarm
-tem
perate
summergreen;ts,temperate
summergreen;ec,eurythermicconifer;wtc,south
warm
-tem
perate
conifer;tc,temperate
conifer;ctc,cool-temperate
evergreen
conifer;bec,borealevergreen
conifer;tef,tropicalandsubtropicalevergreen
forbs/shrubs;tf,temperate
forbs/shrubs;af,arctic-alpineforbs/shrubs;sf,steppeforb/shrub;g,grass;h,Ericaceae;
s,sedge;
wod,woodland;x,ferns;trx,Cyatheaceae.
P.-M. Liew et al. / Quaternary International 147 (2006) 16–33 27
ARTICLE IN PRESS
Table 3
Assignments of plant functional types to biomes
Biome PFTs
Tropical evergreen forest te, tef, trx, x
Tropical rainforest tr, tef, trx, x, ts3
Subtropical evergreen forest sut, tef, ts3, wtc, trx, x
Warm-temperate evergreen forest wte2, tf, ts3, x
Temperate broadleaved and
conifer mixed forest
wte1, ec, tc, ts1, ts2, ts, tf
Cool-temperate conifer forest ctc, ec, g, h
Cold-temperate conifer forest bec, ec, g, h
Alpine conifer forest ec, af, g
Forest steppe wod, g, sf
Alpine shrub land af, sf, g
P.-M. Liew et al. / Quaternary International 147 (2006) 16–3328
35.4, 39.1 and 39.2m where warm-temperate forest has thehigher score). It possibly indicates that further discrimina-tion of the altitudinal zones within the Lauro-Fagaceaeforest using genus level data is not very easy. This is partlydue to the fact that the main pollen types of forests lowerthan the Tsuga–Picea Zone are the Fagaceae—Castanopsis
and Cyclobalanopsis—whose altitudinal spread of species iswide.
The other problem in biomization here is the difficultywhen Gramineae-dominant assemblages are encountered,such as during LGM, due to the wide occurrence ofGramineae in these tropical–subtropical areas. Conse-quently, even though the Gramineae-dominated assem-blages of LGM possibly represent forest steppe or steppeconditions, the biome of temperate broadleaved andconifer mixed forests occurred. We hope more work inthe future will further refine the rule set of the biomes.
5. Interpretation of vegetational history and climatic
conditions
In the pollen diagram, warm elements, such as Castanopsis
and Mallotus, alternated with cold elements, such as Alnus
and Salix. Higher spore values in the diagram are regardedas a proxy of higher precipitation conditions or water-transport processes. Precipitation is usually an index of anintensifying summer monsoon, which in turn representsmore frequent tropical cyclones. Relatively dry conditionsare represented by high values of Gramineae (i.e. Gramineaewithout accompanying large amounts of monolete spores),Alnus and Salix. According to modern vegetation assem-blages (Fig. 2) Alnus and Salix grow in less humid parts ofthe Quercus Zone even though they are well known astemperate, boreal or arctic-alpine trees and shrubs indicatingwet conditions in other places (Tarasov et al., 1998).
5.1. Zones 20–17, tentatively estimated as 95.2–80.5 kyr BP,
probably MIS 5c–a
The early glacial (Zones 20–17) is characterized byassemblages with a high value of Castanopsis-type pollen(20–40%) except Zone 18. Castanopsis-dominant pollen
assemblages usually represent assemblages of subtropicalto warm-temperate forest—Machilus–Castanopsis Zone(500–1500m) in present Taiwan, as shown in pollen recordsstudied earlier (Liew, 1977). However, Castanopsis-domi-nant assemblages of the early glacial have much lowerspore and much higher Cyperaceae content if comparedwith the present Machilus–Castanopsis Zone. They mayindicate a climatic condition less humid than that oftoday’s Machilus–Castanopsis forest. Alternatively, if thoseCastanopsis-type pollen during early glacial are the fewspecies growing higher than 2000m, they may represent aforest within today’s Upper Quercus Zone. The increase ofSalix in Zone 19 indicates a relatively cold trend althoughstill within the temperate broadleaved and conifer mixedforests (the Upper Quercus Zone), which is tentativelyassigned to MIS 5b. After this, a remarkable fluctuationfrom dry to wet is shown in Zone 18 in which Symplocos
and Myrica replace the important role of Castanopsis thenfollowed by high peaks of monolete spores and Polygonum
(91.4–88.8 kyr BP estimated by the age model here). Myrica
presently grows in the low altitude (below 1500m) area ofTaiwan. Whether this wet/warm phase corresponds to thewet event at 88 ka in the loess record of China (Rousseauet al., 2000) needs further study. Castanopsis returns to itsdominant role after this warm–wet phase. Another smallwet/dry fluctuation in the lower part of Zone 17 isindicated by various amounts of Cyperaceae. HigherCyperaceae contents might indicate lower lake levels(Maley and Brenac, 1998). The drought trend in the upperpart of Zone 17 is also witnessed by changes of lithologicalfacies from lake clay to peat. Zones 18 and 17 are assumedto be within MIS 5a. The following zones 16–14 representthe transition from warm to cold conditions.
5.2. Zones 16–14, tentatively estimated as 80.5–73.9 kyr BP
The interval begins with the remarkable decrease ofCastanopsis and increase of Salix, indicating less humidand less warm conditions than before. Fluctuations ofcold/dry to warm/wet conditions from Zones 15 to 14 areshown by the successive dominance of Ilex, Alnus, the lowvalue of Cyperaceae in Zone 15 and the increase ofCyclobalanopsis and Cyperaceae in Zone 14, although stillwithin the temperate broadleaved and conifer mixed forest.
5.3. Zone 13, tentatively assigned as 73.9–59.0 kyr BP,
possibly corresponds to or within MIS 4
Alnus rises to more than 60% and Cyperaceae decreasesharply suggesting spread of Alnus in the area. A pollenassemblage with such high value of Alnus is similar tosurface pollen assemblages between altitudes 2250 and2500m of the present natural forest, central Taiwan. Sharpdecrease of Cyperaceae indicates still drier conditions thanthose of the previous zone. This assemblage represents thetemperate deciduous forest within the present UpperQuercus Zone (or temperate broadleaved and conifer
ARTICLE IN PRESSP.-M. Liew et al. / Quaternary International 147 (2006) 16–33 29
mixed forests). Most of this zone is probably colder thanthe late stadial (Zone 5), considering the associated woodytaxa of Zone 5.
5.4. Zones 12–6 (59.0–27.9 kyr BP): represent interstadial
conditions of MIS 3
Alnus and Cyperaceae alternately dominated, within thetemperate deciduous forest; Cyperaceae indicate increasinghumidity. Ilex and Cyclobalanopsis increase. Castanopsis
increases from Zones 12 to 10, indicating a warmer trendbetween the early and late stadials. There is a remarkable wetepisode from cal. 42.2 to 37.0 kyrBP (estimated36,100–32,500 yrBP) represented by spore-dominant assem-blages (Zone 9). Warm-temperate forest conditions at 41.6,38.0 and 37.3kyrBP appeared based on forest reconstructionalso. A prominent wet episode (35–25kyrBP) during MIS 3has been documented by An (2000). Compared with thisstudy, its age appeared to be younger.
The upper part of this interstadial (from Zone 9 upward)appeared relatively drier than the lower part as revealed bythe amounts of Gramineae. Castanopsis has its lowest valuebetween Zones 9 and 6 although showing a slight increasein Zone 7.
5.5. Zone 5, 27.4–16.7 kyr BP, late stadial, belongs to MIS 2
Vegetation in Zone 5, especially the upper part, ischaracterized by dominance in NAP, representing atemperate forest or possibly forest steppe. Between 23.2and 18.7 kyr BP Gramineae and Artemisia reach theirhighest values, indicating relatively dry and sometimescold conditions. Cyperaceae replace Gramineae at about18.6 kyr BP and warm elements including Symplocos, Ilex
and Cyclobalanopsis increase at about 16.7 kyr BP. How-ever, among the woody elements, Cyclobalanopsis ratherthan Alnus or Pinaceae appear. This is the intervalcorresponding to the LGM. According to the surfacepollen study of lowland northeast China, 40% NAP marksthe existence of forest-steppe zone, and this boundaryalmost overlapped the 700mm/yr annual precipitation(Ren, 1998). Thus, Zone 5 represents relatively dryconditions but probably not as cold as those of Zone 13(MIS 4). The less cold late stadial is shown in the result ofbiomization and also indicated by the study of Tsukada(1967) at Sun-Moon Lake. In comparison to present-daytemperatures, the estimated temperature was 4–5 1C lowerthan today during the late stadial and 8–10 1C lower in theearly stadial. This study confirms this estimation. Warm-temperate to subtropical conditions appeared at 22.3 and18.9 kyr BP before or within the Gramineae-prevailingdrier phase as mentioned previously.
5.6. Zone 4, 27.4–11.0 kyr BP, the late glacial
The late glacial is characterized by a rise of AP. Amongthe woody taxa, Cyclobalanopsis, Ilex, Symplocos and Salix
are of changing importance, mainly representing temperatebroadleaved and conifer mixed forests. The climaticconditions are drier and cooler than today, but warmerand wetter than before. A strong peak of monolete sporesand warm-temperate forest at 15.1 kyr BP (12,800 yr BP)indicates the warm–wet Bølling interval. At about13.0–12.5 kyr BP (10,900–10,450 yr BP) the increase ofSalix marked the beginning of cold conditions. Then Ilex
peaked at 12.1 kyr BP and Gramineae (435%) at11.8–11.6 kyr BP (10,200–10,100 yr BP). They indicate atrend from cold to less cold and then dry-cold conditions ofYounger Dryas time similar to the main trend found in thearid–semiarid transition zone of northern China (Zhou et al.,2001). According to a detailed study in the Netherlands(Hoek, 1997), the late Pleniglacial ended about radiocarbonage 12,900 yrBP (uncalibrated). From 12,900 to 12,450 yrBPis the Oldest Dryas, 12,450 to 12,100 yrBP is Bølling, 12,100to 11,900 yrBP is Older Dryas, 11,900 to 10,950yrBP isAllerød, 10,950 to 10,150 yrBP is Younger Dryas. In theToushe record, the warm interval with a peak of monoletespores at 15.1 kyrBP marked the warm–wet episodecorresponding to Bølling, while peaks of Salix andGramineae may correspond to Younger Dryas (13.0–11.6kyrBP or 10,900–10,100 yrBP). Warm-temperate tosubtropical elements increase at 11.5 kyrBP, but soon returnto temperate conditions at 11.2–11.0 kyrBP (7.18m). After11.0 kyrBP warm-temperate to subtropical forests appearedalmost continuously.
5.7. Zones 3–1 (11.0–1.8 kyr BP)
A Salix peak appeared at 11.0 kyr BP (7.07m) which justpreceded the wet phase indicated by the increase ofmonolete spores at 10.7 kyr BP (6.97m). Climatic condi-tions become subtropical/warm–wet again as indicated bylarge amounts of monolete spores, hydrophyllus herbs andan increase of Castanopsis at the expense of Ilex,Ligustrum, Symplocos and Salix. But the rise of Salix,Ilex and Symplocos again at about 9.6–9.4 kyr BP(8600–8400 yr BP) indicates a cold episode. The subtropi-cal-warm elements increased in the middle Holocene, i.e.Mallotus began to increase between 7.3 and 6.8 kyr BP(6500 and 6000 yr BP) and Glochidion increased at6.2–5.8 kyr BP (5450–090 yr BP). The higher value ofPinus—which grows far from the study site—runs parallelto the trend of the warm element Castanopsis, which mightindicate an intensified monsoon at about 6.9–6.8 kyr BP(6150–6050 yr BP). Salix peaks indicated the prevailingdeciduous forest and less warm conditions at about 11.0,9.6–9.4, 9, 7.9, 7.5, 7.2 and 7.1, 5.2 and 5.0, 4.0 and3.7 kyr BP.The most remarkable feature in the Holocene record is a
conspicuous dominance of monolete spores which indicatewet conditions. An et al. (2000) mentioned that theHolocene optimum may be represented by a wet intervalwhich is asynchronous in East Asia. There are severalintervals during the Holocene with such features especially
ARTICLE IN PRESS
Fig. 5. Detrended correspondence analysis. Mean scores for the samples
of each zone (from 20 to 1) plotted for the first two DCA axes.
P.-M. Liew et al. / Quaternary International 147 (2006) 16–3330
before 6.8 kyr BP in present study, including 10.6–10.3,10.0–9.7, 9.5–8.5, 6.9–6.8 and 2.9–1.8 kyr BP (9300–9100,8900–8600, 8500–7700, 6000–6100 and the last 3000 yr BP).However, the record of the last 5000 yr in the alpine lakesat almost the same latitude has been discussed by theauthors elsewhere (Liew and Huang, 1994). The highervalue of NAP in the early Holocene is considered to be aresult of the enlargement of flooding areas due to earlyHolocene wet conditions (Bush, 2002), while that ofthe recent several millennia is attributed to humandisturbance.
The average score of each zone presented in the first andsecond axis of DCA (Grimm, 1997) is shown in Fig. 5. Pollentaxa involved in DCA analysis are those with percentage42%, including Pinus, Taxodiaceae, Ericaceae, Ilex, Alnus,Quercus, Cyclobalanopsis, Catanopsis, Liquidambar, Symplo-
cos, Trema, Ulmus, Ligustrum, Salix, Glochidion, Homa-
lanthus, Mallotus, Hydrangea, Tristellateia, Gymnosporia,Aizoaceae, Artemisia, Compositae, Polygonum, Ranunculus,Umbeliferae, Typha, Cyperaceae, Gramineae and Liliaceae.The similarity of Zones 6–13 may indicate cold conditionsbefore the late stadial drought; similarities among Zones 7, 9,10 and Zones 8, 11, 12 may indicate cyclic changes inhumidity during the interstadial. Large shifts occurredbetween Zones 19 and 18, 18 and 17, 16 and 15, 15 and14, and 4 and 3 indicating the abrupt change during the earlyglacial and between the late glacial and Holocene.
6. Discussion
We used a biomization technique to reconstruct pastaltitudinal vegetation of the Toushe pollen sequence. Thisallows interpretation of the magnitude of possible environ-mental changes if the site is sensitive to past ecotonechanges. For this site, especially in the Holocene, changesin prevailing biomes appear frequently (Fig. 4.2). Tempe-rate deciduous forest dominated by Alnus prevailed duringthe last glacial. The cold or cold/dry phase in the lastglacial is possibly indicated by the times when peaks of
Gramineae appeared although they are hardly recognizedin the biome reconstruction of this study. Tsuga–Picea
forest does not appear at this site during the last glacialalthough it appears during the early stadial in Sun-MoonLake located 100m higher. Thus, we believe that theboundary between Tsuga–Picea forest and Alnus forest waslocated near the Sun-Moon Lake in the early stadial (Liewand Chung, 2001).The large altitudinal range of Castanopsis pollen type is
another concern in the reconstruction of past biomes. Inthe present study, we include Castanopsis in subtropicaland warm-temperate forests, which means excluding itfrom the temperate broadleaved and conifer mixed forest.If we consider the high-growing species and includeCastanopsis-type pollen in wte1 also, with Castanopsis alsoincluded in temperate forests, we will find only a smallchange in Holocene biome reconstruction but a relativelyclear change in that of the early glacial (six samples among83 samples in Holocene, i.e. ages at about 4.8, 4.85, 4.9, 7.6,7.7 and 7.9 kyr BP will change to temperate broadleavedand conifer mixed forests; while most of Zone 17 willbecome temperate broadleaved and conifer mixed forests).Thus, the Castanopsis-dominant assemblage in early glacialis possibly like that of present subtropical/warm-temperateforests but less humid, or alternatively like parts oftemperate broadleaved and conifer mixed forests.
6.1. Maximum cooling of the last glacial
Long-term vegetational records often show the responseof local flora to climatic changes. During the last glacial,the winter monsoon intensified (Huang et al., 1997), andthe climate was relatively drier and colder than that oftoday. As mentioned above, the stadials of the last glacialare represented by Zone 13 (possibly MIS 4) and Zone 5(MIS 2) in which the early stadial (Zone 13) has the highestvalue of Alnus (460%). Surface pollen assemblages ofSalisien area show that Alnus-dominant (50%) conditionscould be found at about altitude 2250m of today’s forests.Thus, a vertical migration of 1500m could have occurredbetween the early stadial of the last glacial and theHolocene. Furthermore, in contrast to the Alnus-dominantassemblage of Zone 13 in Toushe, a contemporaneousPinus/Tsuga-dominant assemblage is found at the neigh-boring Sun-Moon Lake (Tsukada, 1967). Thus, the level ofSun-Moon Lake (750m) should represent the lowerboundary of Alnus/coniferous forest of the early glacial.Presently the boundary lies at about 2400m above sealevel. Though Taiwan’s uplift rate is generally high, thisarea is fairly stable (Chen, 2003), and vertical displacementdue to tectonism is negligible. Thus, the maximum ecotonemigration is estimated to be at least 41000m and possiblyabout 1500m; therefore, the temperature difference be-tween MIS 4 and present is 8–10 1C.The smooth sedimentation rate in this peat bog (Fig. 3)
excludes the conspicuous diastem during the LGM. Theseverity of cold conditions of the early and late stadials of
ARTICLE IN PRESSP.-M. Liew et al. / Quaternary International 147 (2006) 16–33 31
the last glacial here (Zone 5) appeared different from thoseof many other regions. As described above, Gramineaesometimes reached more than 40% and NAP prevailedduring the late stadial, which indicates drought conditionswith precipitation less than half the present level probably.However, if we compare the woody elements with the earlystadial (Zone 13, MIS 4), the late stadial shows a lowerpercentage of Alnus but higher percentage of Cyclobala-
nopsis. Thus, most of MIS 4 may have been colder thanMIS 2. The biomization results show a similar trend.Conditions of relatively higher sea level and lowerinsolation during MIS 4 than that of MIS 2 may beplausible reasons. The southward shifting ITCZ andtrade wind belt as well as the lowering of sea level duringthe late stadial (MIS 2) possibly resulted in the droughtconditions in this area, while the effect of the maximum icesheet of MIS 2 on subtropical temperature needs to beevaluated.
Many discussions have emphasized the wet intervalduring the later part (35–25 kyr BP) of MIS 3 and the EastAsia monsoon (An, 2000; Shi et al., 2001). In Europe, thereis a mild phase during MIS 3 at about 39,000–36,000 yr ago(Andel and Tzedakis, 1996), similar to the warm–wetinterval of 37–42 kyr BP characterized by remarkable sporepeaks in the present study. If they are related, then thewarm phase may have occurred not only in Asia.
6.2. Younger Dryas
The Younger Dryas was indicated by the remarkableincrease of Salix at about 13.0–12.5 kyr BP which differsfrom previous Cyclobalanopsis–Symplocos prevailing as-semblages, and culminated in the later part of this coldevent by an increase of Gramineae (435%) at11.8–11.6 kyr BP. They indicate a trend from cold to lesscold and then dry-cold conditions of Younger Dryas time,similar to the main trend found in the arid–semiaridtransition zone of northern China (Zhou et al., 2001). It isalmost synchronous with climate records from Europe(Peteet, 1995) and from Africa (Bonnefille et al., 1995). Inequatorial and northern Africa, Gasse (2000) also foundtwo drastic arid-humid transitions occurring around15–14.5 and 11.5–11 ka which correspond to the post-Bølling interstadial and post-Younger Dryas warmingevent in this study. However, at the present study site,the change of vegetation in 13.0–11.6 kyr BP is still withinthe range of temperate broadleaved and mixed coniferforest based on biomization. Thus, this cold event is notrecognizable from the results of forest change only.Nakagawa et al. (2003) described Younger Dryas in thepollen sequence of Lake Suigetsu, Japan, with about a400 yr lag compared with the Greenland ice core (Alley,1993; Mayewski et al., 1993). According to the pollendiagram of Lake Suigetsu, an increase of Fagus and adecrease of Carpinus occurred about 12,600 yr BP. Thus,the onset of Younger Dryas remains equivocal. Onepossible explanation of this age discrepancy is the
definition of magnitude of coldness for the beginning ofthe Younger Dryas.
7. Conclusion
The pollen stratigraphy from the low mountain area ofcentral Taiwan shows vegetational change across the last96,000 yr. During MIS 5 (probably 5c), the Castanopsis-dominant assemblage possibly represents a subtropicalevergreen broadleaved forest, less humid than at present,assuming that these Castanopsis are not high-growingspecies. A Salix-dominant interval follows, which istentatively correlated with MIS 5b. After that, Symplocos
and Myrica dominate; in conjunction with a high sporelevel, this indicates a subtropical forest with a wet episode.Castanopsis then prevails again. Thus at least one wetinterval existed in the early glacial (MIS 5a). The Alnus-
dominant forest replaced the preceding Castanopsis forestduring most of the last glacial. In the early stadial (MIS 4),the Alnus percentage is higher than that of the late stadial(MIS 2). A 8–10 1C lower annual temperature than atpresent and an about 1000–1500m lower boundary of theTsuga–Picea Zone/Upper Quercus Zone than at presentcharacterizes the early stadial (MIS 4). However, in MIS 2,the high value of NAP might represent a forest steppecondition; a fall in precipitation to half the present levelmight be possible. Alnus is lower but Cyclobalanopsis ishigher during the late stadial (MIS 2) than in the earlystadial (MIS 4) indicating less cold conditions than in mostof the early stadial. The generally drier conditions of theglacial stage are interrupted by an episodic warm/wetinterval around 42.2–37.0 kyr BP. Abrupt changes duringthe late glacial and Holocene are also clear. The peak ofmonolete spores at 15.1 kyr BP (12,800 yr BP) and a warm-temperate forest mark the warm–wet episode correspond-ing to the Bølling. At about 13.0–12.5 kyr BP an increase ofSalix possibly marks the onset of cold conditions. Thenafter a peak of Ilex at 12.1 kyr BP, Gramineae (435%) riseat 11.8–11.6 kyr BP which may correspond to the cold toless cold and then cold-dry phases of the Younger Dryas. Asubtropical warm period also appeared at 11.5 kyr BP asindicated by biomization. Subtropical conditions continueto prevail from 10.7 kyr BP onward. An increase of warmelements, such as Castanopsis, appeared around11.2 kyr BP and wet conditions indicated by spore peaksoccurred at about 10.7 kyr BP. Possible abrupt coldepisodes are indicated by Salix peaks at about 11.0,9.6–9.4, 7.9, 7.1, 5.2 and 5.0, 4.0 and 3.7 kyr BP.Subtropical to tropical elements such as Mallotus increasedin the mid-Holocene at about 7.3–6.8 kyr BP (except7.2 kyr BP), while Glochidion was higher between 6.2 and5.8 kyr BP, probably indicating a warmer interval when thesummer monsoon intensified. The warmest climate oc-curred at 6.9 and 6.1–5.9 kyr BP based on forest recon-struction. High early Holocene spore peaks occurred in theintervals 10.6–10.3, 10.0–9.7, 9.5–8.8, 6.9–6.8 and about2.9–1.8 kyr BP and are considered as a proxy of higher
ARTICLE IN PRESSP.-M. Liew et al. / Quaternary International 147 (2006) 16–3332
precipitation induced by an intensifying East Asianmonsoon.
Acknowledgements
The authors are grateful to the reviewers Dr. Pavel Tarasovand Dr. John Dodson for their constructive suggestions inimproving this paper. We also wish to thank Prof. C.F. Hsiehin the Department of Lifesciences of National TaiwanUniversity and Prof. Ge Yu and Dr. B. Xue from NanjingInstitute of Geography and Limnology for their informationabout their biomization study, Dr. M.L. Hsieh and Mr. T.S.Shih for their help in the field and Mr. C.Y. Lee and B.C.Chen for their computer work during this study. Thanks arealso due to Dr. Grimm for DCA analysis using TiliaProgram. This study was funded by the National ScienceCouncil for the PAGES project.
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