ORIGINAL PAPER
An Early Pliocene lake and its surrounding vegetationin Zhejiang, East China
Jin-Feng Li Æ Ya-Qin Hu Æ David Kay Ferguson ÆYu-Fei Wang Æ Cheng-Sen Li
Received: 9 December 2008 / Accepted: 29 July 2009 / Published online: 12 August 2009
� Springer Science+Business Media B.V. 2009
Abstract The palynomorph composition of an Early
Pliocene assemblage from Du’ao Lake, Zhejiang
Province, East China, including sporomorphs and
algae, was analyzed to reconstruct the vegetation and
climate around the lake, as well as the environmental
conditions in the lake. A subtropical evergreen and
deciduous broad-leaved mixed forest surrounding the
lake is inferred from the pollen data. The composition
of the green algae community indicates a clear,
shallow (about 5–6 m deep), mesotrophic freshwater
lake. The inferred pH was about 7.0–8.0 during the
algae growing season. Applying the Coexistence
Approach, the climatic conditions in Early Pliocene
Du’ao were: (1) mean annual temperature ranged
from 18.1 to 22.0�C, (2) difference in temperature
between the coldest and warmest months ranged from
14.2 to 15.1�C, (3) mean temperature of the coldest
month varied from 10.7 to 12.1�C, (4) mean temper-
ature of the warmest month ranged from 23.5 to
25.4�C, (5) mean annual precipitation varied from
about 994 to 1,255 mm, (6) minimum monthly
precipitation ranged from about 9 to 11 mm, and (7)
maximum monthly precipitation varied from approx-
imately 219 to 245 mm. These values indicate that the
Early Pliocene climate was subtropical.
Keywords Algae � Palynology � Paleovegetation �Paleoclimate � Paleolimnology � East China
Introduction
Pollen in lake sediments is useful for inferring
paleovegetation and paleoclimate (Davis 1999; Jan-
kovska et al. 2002; Vincens et al. 2005). Pollen from
aquatic plants can help reconstruct past aquatic
communities. Pollen production by aquatic plants is
largely dependent on temperature, pH, or the nutrient
J.-F. Li � Y.-Q. Hu � Y.-F. Wang � C.-S. Li (&)
State Key Laboratory of Systematic and Evolutionary
Botany, Institute of Botany, Chinese Academy
of Sciences, 100093 Xiangshan, Beijing,
People’s Republic of China
e-mail: [email protected]
J.-F. Li
e-mail: [email protected]
Y.-Q. Hu
e-mail: [email protected]
Y.-F. Wang
e-mail: [email protected]
J.-F. Li
Graduate University of the Chinese Academy of Sciences,
100039 Beijing, People’s Republic of China
Y.-Q. Hu
Institute of Archaeology, Chinese Academy
of Social Sciences, 100710 Wangfujing, Beijing,
People’s Republic of China
D. K. Ferguson
Institute of Palaeontology, University of Vienna,
Althanstrasse 14, 1090 Vienna, Austria
e-mail: [email protected]
123
J Paleolimnol (2010) 43:751–769
DOI 10.1007/s10933-009-9366-z
status of the lake water (Edwards et al. 2000).
Remains of green algae in lake sediments, for
example the coenobia of Pediastrum, Botryococcus,
and zygospores of Spirogyra, Zygnema and Pseud-
oschizaea, can play an important role in inferring past
lake conditions (Jankovska and Komarek 2000;
Medeanic 2006; Medeanic et al. 2003; Tell and
Zamaloa 2004; Zamaloa and Tell 2005; van Geel and
Grenfell 1996). Diatoms are useful indicators of
water quality. In addition to the microfossils men-
tioned above, seeds of plants and other organic
remains may also provide paleolimnological infor-
mation (Argant et al. 2006; Fontana 2005; Robinson
2004; Torres et al. 2005; van Geel et al. 1989;
Whitehead et al. 2001).
Lake sediments serve as natural archives of paleo-
environmental information by accumulating spores,
pollen, and macro-remains from the plants growing in
the catchment. In addition, the remains of hydrophytes
are preserved in the lake sediments, and these plant
remains can provide valuable information about the
vegetation surrounding the ancient lake, past climate,
and even the water body itself. Early Pliocene sediments
from Du’ao Lake, Zhejiang Province, East China,
contain abundant pollen, and coenobia and zygospores
of green coccal and filamentous algae. These remains
were used to investigate the Early Pliocene Lake and its
surrounding vegetation and climate.
Materials and methods
Du’ao Village lies in the northeastern part of Ninghai
County, Zhejiang Province (Fig. 1). The geological
section referred to as the Du’ao section (29�200N,
121�310E, Alt. 134 m) is about 1 km from the village.
This section is Early Pliocene in age (RGZP 1982). We
collected a sample of basaltic rock from the Xidawan
section in Shengzhou County for isotope dating. The
Xidawan section is about 80 km from the Du’ao
section, and possesses the same sediments as Du’ao,
with the basaltic bed overlying the lake deposit.
Analysis by 40Ar-39Ar was performed in the State
Key Laboratory of Lithospheric Evolution, Institute of
Geology and Geophysics, Chinese Academy of Sci-
ences in March of 2007 and yielded a date of
4.03 ± 0.09 Ma, confirming that the section is of
Early Pliocene age (Fig. 2). This result was only
slightly older than results of a previous study at the
same locality, using the same method, which gave an
age of 3.0 ± 0.1–3.5 ± 0.1 Ma (Ho et al. 2003). We
use the Early Pliocene age of the section in this work.
The section is 6.8 m thick and divided into seven layers
(Fig. 3). In total, 27 palynological samples were
collected from the section. Samples were numbered
from bottom (sample 1) to top (sample 27). Water
chestnut fruits and other organic remains were found in
the top of Layer 1,*2.5 m above the bottom. Wood of
Quercus and Liquidambar was also collected from the
sediments. The present landscape can be described as
low hills with small plains in the northern and eastern
coastal areas. There is no natural large lake in this area
today, only ponds and artificial reservoirs.
The palynological samples were treated by heavy
liquid separation (density = 2.0 g/ml) (Li and Du
1999; Moore et al. 1991). The microfossils were
mounted in glycerin and observed under a Leica DM
2500 microscope. The identification of the pollen and
spores was achieved using three principal references
(Wang 1995; IBCAS and SCIBCAS 1982; Zhang et al.
1976) and other literature. Individual sporomorphs
were examined under a FEI Sirion 400 scanning
electron microscope using the single-grain technique
(Ferguson et al. 2007). Treatment with hydrogen
peroxide and hydrochloric acid was done to obtain
diatoms, but few were recovered from the samples.
To understand the climate around Du’ao Lake in the
Early Pliocene, the coexistence approach (CA) (Liang
et al. 2001; Mosbrugger and Utescher 1997) was
applied. Based on the pollen taxa, the NLRs (nearest
living relatives) and their geographic distributions (Wu
and Ding 1999) were collated. The modern climatic
variables used in the CA were taken from Surface
Meteorological Data of China (1951–1980) (IDBMC
1983a, b, c, 1984a, b, c) and the Paleoflora Database
(http://www.geologie.uni-bonn.de/Palaeoflora/Palaeo
flora_home.htm). Seven paleoclimatic variables were
obtained (MAT = mean annual temperature, WMMT =
mean temperature of the warmest month, CMMT =
mean temperature of the coldest month, DT = differ-
ence between temperature of the coldest and warmest
months, MAP = mean annual precipitation, MaMP =
maximum monthly precipitation, and MiMP = mini-
mum monthly precipitation). Additional information
on the hydrological conditions of Early Pliocene Du’ao
Lake was obtained by analyzing the pollen of aquatic
taxa and algae in the residue.
752 J Paleolimnol (2010) 43:751–769
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Fig. 1 Map showing the location of the sampling point
Fig. 2 Dating data of the Du’ao section
J Paleolimnol (2010) 43:751–769 753
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Results
Sporomorph analysis
No sporomorphs or algae were observed in Samples
11–27. The palynomorphs obtained from Samples
1–10 consist of 81 taxa, including 63 angiosperms
(77.8%), 5 gymnosperms (6.2%), 7 pteridophytes
(8.6%), 5 algae (6.2%) and Pseudoschizaea (1.2%)
(Table 1). More than 11,700 palynomorph grains
were identified in this work. Angiosperm pollen
constituted 53.7% of the grains, gymnosperm pollen
3.0%, pteridophyte spores 0.9%, algae 42.3%, and
unknown pollen and spores 0.1%. Of the angiosperms
Fig. 3 Lithological
sequence of Early Pliocene
from Du’ao (No
sporomorphs were present
in Samples 11–27)
754 J Paleolimnol (2010) 43:751–769
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(Fig. 4; Table 1), pollen of Castanopsis dominated,
with a percentage range of 15.0–47.1%, and an
average percentage of 35.5%, followed by Liquid-
ambar (1.9–9.6%, average of 5.4%) and Betula (1.3–
4.6%, average of 2.6%). Twenty-five herbaceous
angiosperm taxa were identified, representing 2.6%
of the angiosperms. Gesneriaceae (0–4.8%, average
of 1.0%) and Polygonum (0–1.3%, average of 0.2%)
were common among the herbs. Myriophyllum
(0–0.1%, average of 0.1%) was found in every
sample and was the most common aquatic macro-
phyte taxon. Cyperaceae (0–0.1%, average of 0.03%)
and Potamogetonaceae (0–0.1%, average of 0.1%)
pollen were rare in the samples. Although Trapa
pollen was only found in sample No. 7, its fruits were
found in the sediments of Layer 1. Gymnosperms
include five genera (Pinus, Abies, Tsuga, Picea and
Larix), all of which belong to the Pinaceae. They had
an average percentage of 3.0%. Seven genera of
pteridophytes, with an average percentage of 0.9%,
were found in the samples. Athyriaceae (0–1.0%,
average of 0.3%), Polypodiaceae (0–1.0%, average of
0.2%), and Pteris (0–0.7%, average of 0.2%) were
the most common taxa.
Table 1 List of Du’ao taxa grouped by ecological requirements and their percentages (Table style based on Jimenez-Moreno et al.
2007)
Taxa % Taxa % Taxa %
Megathermic elements Carya 1.75 Chenopodiaceae 0.09
Rutaceae 0.09 Castanea 1.08 Compositae 0.03
Flacourtiaceae 0.02 Ulmus 1.11 Plantaginaceae 0.01
Loranthaceae 0.01 Oleaceae 0.07 Caryophyllaceae 0.08
Dipterocarpaceae 0.01 Caprifoliaceae 0.09 Umbelliferae 0.02
Ebenaceae 0.16 Anacardiaceae 0.24 Leguminosae 0.12
Proteaceae 0.08 Campanulaceae 0.05 Polygonum 0.20
Aquifoliaceae 0.13 Araliaceae 0.20 Gramineae 0.09
Symplocaceae 0.03 Magnoliaceae 0.04 Ericaceae 0.18
Piperaceae 0.05 Meso-microthermic elements Aquatic Macrophytes
Pittosporaceae 0.02 Pinus 1.99 Cyperaceae 0.03
Sapindaceae 0.03 Tsuga 0.27 Potamogetonaceae 0.06
Myrsinaceae 0.01 Microthermic Myriophyllum 0.14
Melastomataceae 0.01 Abies 0.72 Trapa 0.01
Mega-mesothermic elements Picea 0.01 Pteridophytes
Hamamelidaceae 0.13 Larix 0.02 Pteris 0.24
Euphorbiaceae 0.45 Non-significant elements Hemionitidaceae 0.11
Liquidambar 5.43 Rosaceae 0.02 Athyriaceae 0.28
Castanopsis 35.49 Herbs and shrubs Polypodiaceae 0.22
Myrtaceae 0.09 Cucurbitaceae 0.16 Dennstaedtiaceae 0.07
Guttiferae 0.04 Labiatae 0.07 Hymenophyllaceae 0.01
Cornaceae 0.01 Gentianaceae 0.02 Botrychiaceae 0.01
Mesothermic elements Thymelaeaceae 0.05 Algae
Quercus 0.68 Rubiaceae 0.08 Spirogyra 1.00
Betula 2.57 Gesneriaceae 0.96 Zygnema 0.01
Corylus 0.32 Amaranthaceae 0.21 Botryococcus 39.99
Alnus 0.13 Lobeliaceae 0.03 Pediastrum 1.17
Ostryopsis 0.02 Saururaceae 0.08 Pseudoschizaea 0.09
Tilia 0.20 Ranunculaceae 0.01 Coelastrum 0.01
Pterocarya 0.02 Convolvulaceae 0.01 Other elements
Juglans 0.03 Cruciferae 0.03 Unknown 0.14
J Paleolimnol (2010) 43:751–769 755
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Algae in the paleolake
Three morphological types of Botryococcus colonies
were identified using features of cell shape and
intracellular structure (Komarek and Marvan 1992)
(Plate 1). They displayed an average percentage of
40.0%, and thus dominated the green algae. Three
morphological types of Spirogyra zygospores (Plate 2)
were found in every sample, with a total percentage of
1.0%. These types differ from one another mainly in
wall ornamentation. Pseudoschizaea also regularly
occurs in samples, with a percentage of 0.1%. Six types
of Pediastrum coenobia were identified as Pediastrum
simplex var. clathratum, P. simplex var. pseudogla-
brum, P. simplex var. sturmii, P. musteri, P. sculptatum
and P. boryanum var. boryanum (Plates 3, 4), with a
percentage of 1.2%. A zygospore of Zygnema (Plate 2,
Fig. 4) and a Coelastrum (Plate 1, Fig. 14) were found
in sample No. 1 and sample No. 7, respectively.
Hydrophytes of Du’ao paleolake in the Early
Pliocene
Zygnemataceae
Spirogyra and Zygnema occur widely in freshwater
(Colbath and Grenfell 1995; Hoshaw and McCourt
1988). Unfortunately, there is little known about the
ecology of the individual species of Zygnemataceae.
The occurrence of the zygospores of Spirogyra and
Zygnema indicate a shallow, eutrophic water body,
with warm pluvial periods that supplied fluvial
sediments (Medeanic 2006; van Geel et al. 1989).
Zygospore formation occurs mostly in the spring
in clean, oxygen-rich, shallow, fresh water (van
Geel 1976). The optimal temperature for Zygnema is
15–20�C, and for most species of Spirogyra the
optimum is from 14 to 22�C (Hoshaw 1968). Such
high temperatures are easily reached in shallow water
exposed to direct solar radiation, at least during the
warm season (van Geel 1978). A pH value of 7.0–8.0
was inferred from the zygospores of Spirogyra (Grote
1977).
Pediastrum
Fossil Pediastrum in the pollen slides would indicate
a wide range of environmental conditions (Batten
1996). The genus has been largely used as a
biological indicator for freshwater environments and
temperate (or warm) climate (Zamaloa and Tell
2005). Crisman (1978) mentioned that species of
Pediastrum are common in hard-water, eutrophic
lakes. However, each Pediastrum species has specific
ecological requirements. Many phycologists are of
the opinion that the whole algal spectrum must be
considered when paleoecological reconstructions of
the aquatic environment are attempted. The larger the
Fig. 4 Diagram showing percentage values of main palynomorphs of Du’ao ( Indicates the presence of a taxon at a low
percentage)
756 J Paleolimnol (2010) 43:751–769
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number of Pediastrum species, the more accurate the
interpretation of the ecological conditions (Komarek
and Jankovska 2001; Tell and Zamaloa 2004).
Pediastrum simplex
P. simplex has a sub-cosmopolitan distribution. At
present, P. simplex occurs in unpolluted, mesotrophic
water bodies (Komarek and Jankovska 2001). As it is
slightly thermophilic, P. simplex indicates a warm
water body. The occurrence of P. simplex is indic-
ative of mesotrophic conditions.
Pediastrum boryanum
P. boryanum is the most common cosmopolitan
species and there are more than nine varieties
recorded. Some of these may be indicative of tropical
conditions. P. boryanum is well known from the
Pleistocene, Late Glacial and Holocene in Europe and
from the Late Cretaceous of America (Komarek and
Jankovska 2001; Tell and Zamaloa 2004). At present,
P. boryanum var. boryanum occurs in mesotrophic to
eutrophic waters (Komarek and Jankovska 2001).
Pediastrum musteri
P. musteri is mainly described from lakes in arid
regions of Patagonia (southern Argentina) (Komarek
and Jankovska 2001). Other literature indicates that
this species probably occurs sporadically in clear
lakes in the temperate zones of both hemispheres
(Tell and Mataloni 1990).
Pediastrum sculptatum
P. sculptatum is known only from clear lakes and
peaty biotopes in the northern parts of the USA and
Canada, and as far north as the Arctic regions
(Komarek and Jankovska 2001). This is the first
report of this species in China.
Plate 1 1–8 Botryococcustype 1; 9–11 Botryococcustype 2; 12, 13 Botryococcustype 3; 14 Coelastrum sp.
(Scale bar = 30 l)
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Botryococcus
Botryococcus, which is mainly distributed in temper-
ate and tropical regions, is one of the most common
palynomorphs of coccal algae in lagoonal and
lacustrine sediments (Medeanic 2006). It has changed
little with time and no evolutionary pattern of
morphological change has been detected, so it was
obviously successful as an early colonizer and
evidently adapted easily to the aquatic habitats in
which it grew (Guy-Ohlson 1992).
The predominance of Botryococcus indicates
shallow water and clear, mesotrophic conditions
(Medeanic et al. 2003; Reynolds et al. 2002). Guy-
Ohlson (1992) showed that Botryococcus is more
widespread in brackish-water basins than other green
algae, and is usually abundant in shallow water with
relatively low rainfall and a seasonal climate.
Other coccal green algae in the paleolake
The zygospores of Pseudoschizaea (syn. Concentri-
cystis) are considered to represent zygnemataceous
algae (Medeanic 2006). The genus is widely dis-
persed in shallow, freshwater localities (Ke 1995).
Although Pseudoschizaea has never been found alive,
it is considered to have lived mainly in marshy
habitats (Milanesi et al. 2006). Besides that, there is
little ecological information about this genus (Plate 4,
Fig. 4).
Coelastrum (Plate 1, Fig. 14) is a euplanktonic
taxon of freshwater lakes and ponds, and it develops
Plate 2 1 Spirogyra type
1; 2 Spirogyra type 2;
3 Spirogyra type 3;
4 Zygnema sp
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mainly from late spring to early autumn in shallow
water (Salmaso 2002). Little is known about the
ecological preferences of Coelastrum.
Reconstruction of the vegetation
Plant communities surrounding the paleolake
Pollen taxa (Plates 5, 6, 7, and 8) were grouped by
their ecological requirements (Jimenez-Moreno et al.
2007) (Table 1) based on the work of Wu and Raven
(1999). There are 13 megathermic elements, 7 mega-
mesothermic elements, 17 mesothermic elements, 2
meso-microthermic and 3 microthermic elements in
the vegetation surrounding the lake. Rosaceae is
distributed widely in different climatic zones. Though
the megathermic elements only have a percentage of
0.7% in total, this can be attributed to the low pollen
productivity of these largely entomophilous plants.
We suggest that many megathermic taxa were
growing in the forest and most of them are represen-
tatives of tropical-subtropical taxa, such as Rutaceae
(0.09%), Flacourtiaceae (0.02%), Loranthaceae
(0.01%), Dipterocarpaceae (0.01%), Pittosporaceae
(0.02%) and Myrsinaceae (0.01%). Castanopsis
(35.5%) and Liquidambar (5.4%) are very common
taxa in the palynological assemblages. Genera of
Betulaceae (3.7%) and Juglandaceae (2.9%) are the
most common mesothermic elements. Considering
the great pollen production of their catkins, these
mesothermic plants may not have been very common,
at least in the lowland forest. Ulmus pollen (1.1%) is
also relatively common. The meso-microthermic
and microthermic elements all belong to the Pinaceae
Plate 3 1, 2 Pediastrumsimplex var. clathratum;
3 Pediastrum simplex var.
pseudoglabrum;
4 Pediastrum simplexvar. sturmii
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(5 genera), representing only 3.0% of the assemblage.
Representatives of these genera were probably part of
the regional flora.
Vegetation at Du’ao in the Early Pliocene
We reconstructed the paleovegetation using the
pollen remains in the sediment. The pollen remains
suggest a subtropical-tropical evergreen and decid-
uous broad-leaved mixed forest in the landscape
around Du’ao Lake during the Early Pliocene.
Castanopsis and Liquidambar were the dominant
elements in the forests. The megathermic trees (e.g.
Loranthaceae, Flacourtiaceae, Dipterocarpaceae and
Pittosporaceae) must have been growing in the
valleys and/or the lowlands close to the lake. Some
representatives of Betulaceae and Juglandaceae grew
in the forests on the hillsides. Abundant herbs (25
herbaceous types) were living under the trees or on
the edge of the lake. Among the herbs, Gesneriaceae
and Polygonum were very common. Pteridophytes
such as Athyriaceae, Pteris and Polypodiaceae were
also common in the area. Considering the high
productivity of conifer pollen and their structure,
with two huge sacci (Ruffaldi 1994; Vermoere et al.
2001), we suggest that some of the conifer pollen
may have undergone long-distance dispersal.
Although it has sacci, Abies pollen is deposited
rapidly from the airshed. Larix does not have sacci.
Hence, the vegetation can be characterized as a
Plate 4 1 Pediastrummusteri; 2 Pediastrumsculptatum; 3 Pediastrumboryanum var. boryanum;
4 Pseudoschizaea
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subtropical-tropical type in the Early Pliocene. This
is supported by the work on mega-fossils from the
Early Pliocene of Shengzhou, Zhejiang Province
(Hu 2007).
The modern vegetation of the study area is mid-
subtropical (Jin 1994), with tropical and subtropical
families, such as Olacaceae, Flacourtiaceae, Myrsin-
aceae, and Myrtaceae composing 66.3% of all
spermatophytic families. Evergreen broad-leaved
forests are present below about 1,300 m (FZEB
1993). Castanopsis eyrei (Champ. ex Benth.) Tutch.
is the most common species in the evergreen broad-
leaved forests of Zhejiang (FZEB 1993; Jin 1994,
1998). Species of Liquidambar often occupy the
highest level of the forest community (Shi et al.
1995). Most of the subtropical-tropical elements (e.g.
Dipterocarpaceae) that were present in this area
during the Early Pliocene are absent from present
forests. But the representative subtropical elements
(e.g. Liquidambar and Castanopsis) have lived in the
forests of this area until today.
Aquatic macrophytes in the paleolake
Myriophyllum and Potamogetonaceae are very com-
mon submerged aquatic plants that grow in water at
depths of 1–6 m. Trapa, a rooted or free-floating
aquatic plant, is represented in the sediments by its
pollen and fruits. As most of the leaves and seeds of
aquatic plants are found within 35 m of the parent
plants (Zhao et al. 2006), Trapa must have been a
local element (cf. Zetter and Ferguson 2001). The
Plate 5 1 Abies; 2 Pinus;
3 Pteris; 4 Polypodiaceae
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species of Polygonum and Gramineae could either
have lived on land or in the littoral zone.
Climatic conditions around Du’ao
in the Early Pliocene
Climatic conditions around Du’ao in the Early
Pliocene were inferred by applying the coexistence
approach (CA) to the palynological data. Figure 5
illustrates the ranges of the climate variables based on
68 spermatophytic taxa from Du’ao. They are:
MAT = 18.1–22.0�C (median value of 20.1�C),
DT = 14.2–15.1�C, CMMT = 10.7–12.1�C, WMMT =
23.8–25.4�C, MAP = 994–1,255 mm, MiMP = 9–11
mm, MaMP = 219–245 mm (Table 2).
Discussion
Reconstruction of the lake conditions
The organic-rich sediments belong to Facies 11 of
Torres (Torres et al. 2005), which represent shallow-
water conditions. Analysis of the hydrophytes in the
lake indicates a shallow, freshwater lake probably
existed at Du’ao in the Early Pliocene (Fig. 6). On
shore, Polygonum and Gramineae occupied the
largest area. The littoral zone of the lake was about
1–6 m deep, with much Myriophyllum, Potamogeton
and Trapa. Many green algae were living in the water
body, such as Spirogyra, Zygnema and Pediastrum.
The water must have been clear and mesotrophic.
Plate 6 1 Liquidambar; 2Symplocaceae; 3 Quercus;
4 Rutaceae
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During the rainy season, the lake filled with fresh
water. Seasonal variation of the water temperature
was not extreme and the water level of the lake was
probably relatively stable throughout the year. Based
on the hydrophytes in the samples, the water
temperature was about 14–22�C, at least during the
growing season. A water-column pH of 7.0–8.0, at
least during the reproductive phase of the algae, was
inferred from the diverse zygospores found.
Vegetation in the Early Pliocene and succession
of the vegetation in the Zhejiang area
Pliocene vegetation and climate in China
During the Pliocene, the vegetation and climate were
highly diversified in China. In Northwest China, the
vegetation of Qinghai Province was characterized by
grassland with mixed conifer/broad-leaved forests
dominated by Pinus, Picea, Quercus, Betula, Artemi-
sia, Chenopodiaceae, and Compositae (Shen et al.
1990). The vegetation in Xinjiang Autonomous
Region was regarded as a desert steppe, with mainly
Chenopodiaceae, Artemisia, Ephedra, Compositae,
and Tamarix (Xiao et al. 2003). Mixed conifer and
broad-leaved forests possessing Pinus, Picea, Betula,
Corylus, Juglans, and Quercus were found in Gansu
Province (Wu 2001). The presence of xerophytic
plants, such as Chenopodiaceae, Artemisia, and Ephe-
dra in this vegetation suggests that the climate was
becoming dry in Northwest China in the Pliocene.
In Southwest China, conifers, deciduous broad-
leaved trees (e.g. Tsuga, Picea, Quercus, Ulmus) and
xerophytic herbs (e.g. Artemisia and Chenopodiaceae)
Plate 7 1 Tilia; 2 Carya;
3 Ulmus; 4 Ericaceae
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were growing on the Tibetan Plateau. These plants
formed coniferous or conifer-broad leaved forests and
retama bushland (Li and Zhou 2001; Shen and Tang
1992; Wang 1992). The climate on the Plateau was
becoming dry and cold (Shen and Tang 1992). On the
other hand, the climate in Yunnan was mainly hot and
humid (Li 1994; Wang 1992; Yi et al. 2002) with
plants such as Euphorbiaceae, Liquidambar and
Anacardiaceae growing in subtropical broad-leaved
forests.
In North China, the vegetation was dominated by
large numbers of herbs (e.g. Artemisia, Gramineae
and Chenopodiaceae) in Shandong Province (Wang
et al. 2002; Tan et al. 2000). At the same time, a few
subtropical plants, such as Carya, Euphorbiaceae and
Pterocarya, were living in the forests. The climate
changed from subtropical-warm temperate in the
Mid-Miocene (Liang et al. 2001; Liang et al. 2003;
Yang et al. 2007) to warm temperate in the Pliocene.
In Shanxi Province, many common plants, such as
Picea, Tsuga, Pinus and Amentiferae (catkin-bearing
trees), along with a few subtropical trees (e.g.
Rutaceae, Pterocarya), were found in the mixed
conifer/broad-leaved forests (Cao et al. 1998; Li et al.
2001; Li et al. 2004; Shi 1996). The climate was
warm-temperate in this area. Li et al. (2001, 2004)
also recognized warm-humid and warm-dry intervals,
as reflected by changes in the amounts of herbs (e.g.
Artemisia, Chenopodiaceae) and Ephedra in the
Early Pliocene.
In Southeast China, a pollen study in Anhui
Province showed that Picea, Tsuga, Carya, Liquid-
ambar and Podocarpus were well represented in the
forests. Meanwhile, the presence of Hemiptelea and
Plate 8 1 Polygonum; 2Araliaceae; 3 Vitaceae; 4Myriophyllum
764 J Paleolimnol (2010) 43:751–769
123
Ephedra indicates that the climate was getting colder
and drier, although the landscape was still covered
largely by subtropical conifer/broad-leaved forests at
that time (Yu et al. 1991). In Zhejiang Province, the
climate was subtropical-tropical in the Early Plio-
cene. At Du’ao, Castanopsis, Liquidambar, and
Fig. 5 Intervals of the seven climatic parameters of Du’ao in
Early Pliocene. (MAT the mean annual temperature, WMMTthe mean temperature of the warmest month, CMMT the mean
temperature of the coldest month, DT the difference of
temperature between the coldest and warmest months, MAPthe mean annual precipitation, MaMP the maximum monthly
precipitation, MiMP the minimum monthly precipitation.) 1
Pinus, 2 Abies, 3 Picea, 4 Tsuga, 5 Larix, 6 Liquidambar, 7
Castanopsis, 8 Castanea, 9 Quercus, 10 Betula, 11 Tilia, 12
Corylus, 13 Carya, 14 Alnus, 15 Pterocary, 16 Juglans, 17
Ostryopsis, 18 Ulmus, 19 Myrtaceae, 20 Oleaceae, 21
Ericaceae, 22 Euphorbiaceae, 23 Araliaceae, 24 Magnoliaceae,
25 Hamameliaceae, 26 Campanulaceae, 27 Anacardiaceae, 28
Rutaceae, 29 Cucurbitaceae, 30 Rosaceae, 31 Loranthaceae, 32
Caprifoliaceae, 33 Aquifoliaceae, 34 Labiatae, 35 Gentiana-
ceae, 36 Flacourtiaceae, 37 Thymelaeaceae, 38 Dipterocarpa-
ceae, 39 Ebenaceae, 40 Guttiferae, 41 Proteaceae, 42
Symplocos, 43 Cornaceae, 44 Piperaceae, 45 Pittosporaceae,
46 Sapindaceae, 47 Rubiaceae, 48 Myrsinaceae, 49 Gesneri-
aceae, 50 Amaranthaceae, 51 Melastomataceae, 52 Lobelia-
ceae, 53 Saururaceae, 54 Ranunculaceae, 55 Convolvulaceae,
56 Cruciferae, 57 Chenopodiaceae, 58 Compositae, 59
Plantaginaceae, 60 Caryophyllaceae, 61 Umbelliferae, 62
Leguminosae, 63 Polygonum, 64 Gramineae, 65 Cyperaceae,
66 Potamogeton, 67 Myriophyllum, 68. Trapa
J Paleolimnol (2010) 43:751–769 765
123
Betula made an important contribution to the mixed
evergreen/deciduous broad-leaved forest.
The climate in China during the Pliocene was
mainly affected by the East Asian monsoon system.
The control and interaction of the various monsoons,
including the northwestern monsoon from Siberia,
the southwestern monsoon from the Indian Ocean and
the southeastern monsoon originating in the Pacific
Ocean, resulted in a range of climate patterns in
different regions of China. During the Pliocene, there
was a gradient from a dry temperate climate in
Northwest China to a humid tropical-subtropical one
in Southeast China. Zhejiang Province is located in
southeastern China, and the Pliocene climate there
was subtropical, being influenced mainly by the
southeastern monsoon.
Table 2 A comparison of the climatic parameters of Du’ao in the Early Pliocene and Xiangshan at present
MAT/�C WMMT/�C CMMT/�C DT/�C
Du’ao (Early Pliocene) 18.1–22.0 23.8–25.4 10.7–12.1 14.2–15.1
Du’ao (Early Pliocene) 20.1a 29.6a 11.4a 14.7a
Xiangshan (Present) 15.8b 27.8b 3.7b 24.1b
MAP/mm MaMP/mm MiMP/mm
Du’ao (Early Pliocene) 993.8–1,254.7 218.9–245.2 9.3–11.3
Du’ao (Early Pliocene) 1124a 232a 10a
Xiangshan (Present) 1111b 155.6b 34.7b
a Median valueb Mean value
Fig. 6 Reconstruction of the vegetation in and around the Early Pliocene lake in Du’ao
766 J Paleolimnol (2010) 43:751–769
123
Climate change at Du’ao in the Pliocene
Climate of Du’ao in the Early Pliocene
The climatic inferences obtained from the CA analysis
indicate that the climate of Early Pliocene Du’ao was
subtropical and/or tropical. Xiangshan County, which
is the nearest site available in the IDBMC meteoro-
logical database, lies about 42 km southeast of Du’ao.
Compared with the present surface meteorological
data, the MAT of Early Pliocene Du’ao was a little
higher (ca. 4.3�C) than that of Xiangshan at present and
the MAP was similar, 1,124 mm during the Early
Pliocene compared to 1,111 mm at present. The
increase of the DT value, from a mean value of
14.7�C during the Early Pliocene to 21.7�C at present,
and the decrease of the CMMT value, from a mean of
11.4�C in the Early Pliocene to 3.7�C on average at
present, indicate that the climate has become more
variable. This could explain why the vegetation
changed considerably from the Early Pliocene to
present. The amount of precipitation during the Early
Pliocene was similar to that of the present.
Climate change in the Zhejiang area
after the Early Pliocene
We inferred a median value of 20.1�C for the MAT in
Du’ao (see the CA results) during the Early Pliocene.
A similar result (17.7–21.4�C, median value of
19.6�C) was obtained based on the mega-fossil flora
of a nearby diatomite deposit (Hu 2007). A study on
stalagmites (Wang et al. 1998) in Hangzhou, the
capital city of Zhejiang Province and about 120 km
from Du’ao, indicates that the MAT there was 9.4�C
at 50,000 years BP, 12.3�C at 42,000 years BP, 7.6�C
at 31,000 years BP, 14�C at 28,000 years BP, 6.6�C
at 16,000 years BP and 10.2�C at 9,700 years BP.
The MAT is 16.2�C at present in the Hangzhou area.
We assume that the temperature in Zhejiang dis-
played a downward trend from 20.1 to 16.2�C.
However, the Quaternary glaciations affected the
climate and caused temperature to fluctuate.
Conclusions
Analysis of fossil pollen assemblages in lake deposits
can reveal much about past vegetation composition
and climate, while study of the algae can provide
information on the chemistry of the water body. By
combining information from both microfossil sources,
a more complete picture of the paleoenvironment is
achieved. In this study, we attempted to infer both past
lacustrine conditions and the vegetation surrounding
the water body. Our results indicate that there was a
clear, shallow, mesotrophic freshwater lake at Du’ao,
Zhejiang Province, East China during the early
Pliocene. Vegetation surrounding the lake can be
described as subtropical-tropical evergreen, and
broad-leaved deciduous forest. The Early Pliocene
MAT was higher than at present. However, large
differences in CMMT and DT, between the Early
Pliocene and present, are inferred from the consider-
able changes in vegetation since the Early Pliocene.
Acknowledgments The authors thank Senior Engineer Nai-
Qiu Du for her help with pollen identifications. We are also
grateful to Su-Ping Li for her assistance with laboratory
analysis. Ya-Meng Li, Dr. Jian Yang, Dr. Yi-Feng Yao and
other colleagues also assisted. This investigation was supported
by the National Basic Research Program (No. 2004CB720205),
National Natural Science Foundation (No. 30530050), Beijing
Finance Special Fund (No. Jingcaiyuzhi[2008]0178) and State
Key Laboratory of Systematic and Evolutionary Botany
Special Found. The present publication is a contribution to
the NECLIME project.
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