Journal of Asian Earth Sciences 38 (2010) 162–169
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Journal of Asian Earth Sciences
journal homepage: www.elsevier.com/locate/jseaes
Bulk organic carbon isotopic record of lacustrine sediments in Dahu Swamp, eastern
Nanling Mountains in South China: Implication for catchment environmental
and climatic changes in the last 16,000 years
Zhong Wei a,*, Xue Jibin a, Cao Jixiu b, Zheng Yanming a, Ma Qiaohong a, Ouyang Jun a, Cai Ying a,
Zeng Zhiguo a, Liu Wei a
a
b
School of Geography Science, South China Normal University, Guangzhou 510631, China
School of Resources and Environment Science, Lanzhou University, Lanzhou 730000, China
a r t i c l e
i n f o
Article history:
Received 20 November 2008
Received in revised form 13 September
2009
Accepted 13 December 2009
Keywords:
Dahu Swamp
Bulk organic carbon isotope
The East Asia monsoon
Environmental changes
The Last Deglaciation
South China
a b s t r a c t
A combination of lithology, organic matter accumulation rate, bulk dry density, mass magnetic susceptibility, median grain size, carbon-to-nitrogen and trace element Rb/Sr ratio was utilized to characterize
bulk organic carbon isotopic ratio (d13Corg) of a lacustrine sediment core recovered at Dahu Swamp in
the eastern Nanling Mountains as an indicator of past environmental and climatic changes. Chronological
sequence of this core was established by twelve conventional radiocarbon dates and the bottom age was
determined at ca. 16,000 cal year BP. Multiproxies demonstrate that terrestrial source organic matter
may have played a more important role in contribution to accumulation of organic matter in Dahu
Swamp than autochthonous source. Multiproxies support the interpretation that bulk d13Corg record
reflects carbon isotopic signal of allochthonous C3 plants on which atmospheric precipitation may exert
a strong impact. Although changes in bulk d13Corg of lacustrine sediments may be resulted from a mixing
of materials with different d13C signature and with different fraction, and the cause and mechanism leading to the observed organic carbon isotope responses are presently not fully understood, however, this
study demonstrates that bulk d13Corg record of Dahu Swamp sediments has the potential to reflect variation of environmental and climatic changes of the lake catchment since the Last Deglaciation, the more
negative the bulk d13Corg values the stronger the summer monsoon precipitation and vice versa.
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
Lacustrine sediments have long served as archives of continental environmental changes because they contain a myriad of isotopic, chemical, and biological proxies (Talbot, 1990; Meyers and
Horie, 1993; Anderson et al., 1996; Aaron et al., 2008) that characterize changes in past environments and climate. Carbon isotopes
of lacustrine sedimentary organic matter (OM) have frequently
been used as environmental proxies because carbon budgets are
very sensitive to environmental and climatic changes (Brown
et al., 1991; Talbot and Johannessen, 1992; Meyers and Ishiwatari,
1993; Street-Perrott et al., 1997; Lücke et al., 2003; Leng and
Marshall, 2004; Andreas et al., 2003; Liu et al., 2005a). However,
in many cases, lacustrine sedimentary OM consists of a mixture
of organic materials from lake-internal and -external sources.
These sources may have clearly distinguishable isotopic signatures,
and therefore changes in the sources of OM may likewise be re-
flected in the stable isotope composition of sedimentary OM
(Meyers, 1994; Lücke and Brauer, 2004; Mackie et al., 2005). Due
to these diverse origins organic material can have different isotopic
signatures and, thus, a mixture of unknown amounts can disguise
the organic carbon isotope signals; an evaluation of the direct environmental influence on the isotopic signature of sedimentary OM
remains difficult. However, investigation of lacustrine systems
characterized by high time resolution, reliable dating and high signal to noise ratios can overcome the existing problems. In this
study, we present a new well-dated high-resolution bulk carbon
isotope record of a lacustrine sedimentary sequence recovered in
Dahu Swamp in the eastern Nanling Mountains, South China. The
aim of the study is to test the potential of bulk organic carbon isotope record as an indicator to reflect environmental and climatic
changes in the last 16,000 years over the lake’s catchment.
2. Regional setting
* Corresponding author. Fax: +86 020 85215910.
E-mail address: [email protected] (Z. Wei).
1367-9120/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jseaes.2009.12.011
Dahu Swamp (24°45.00 N–24°46.00 N, 115°02.10 E–115°02.30 E),
developed in a small closed intermontane basin in the eastern Nan-
Z. Wei et al. / Journal of Asian Earth Sciences 38 (2010) 162–169
ling Mountains, is located about 2 km southwest of the Dingnan
county town in Jiangxi province (Fig. 1). The study region lies in
the watershed between the Yangtze River and the Zhujiang River
systems and in the southern boundary of the mid-subtropical regime. The East Asia (EA) monsoon climate, as well as the zonal climatic shifts strongly influences this area (Zhou et al., 2004). Mean
annual precipitation is about 1600 mm and mean annual temperature is 17.8 °C. Modern vegetation consists of subtropical species
of evergreen broadleaf trees with Castanopsis and varieties of
Lithocarpus and Cyclobalanopsis as dominant assemblages, and
Schima, Eurya, Michelia, Symplocus and Ilex as the companion
assemblages (China Vegetation Editing Committee, 1980). Dahu
Swamp appears hydrologically closed and is mainly fed by atmospheric precipitation.
3. Material and methods
In December 2006, we recovered seven cores in Dahu Swamp.
Together with core D01 drilled in May 2005, all the eight cores
indicate stratigraphy of Dahu Swamp is characterized by shifts between organic-poor greyish green (or brown) silt or silty clay and
dark grey organic mud or brownish yellow peat. A 350-cm-long
sediment core (named core K02, 24°450 4300 N, 115°020 2500 E, 246 m
above the mean sea level) (Fig. 1) was chosen for this study. In
the field, this core was halved lengthwise, photographed and
described.
Samples were collected at 1 cm intervals for analyses of grain
size distribution, mass magnetic susceptibility, total organic carbon content and nitrogen. Bulk dry density and organic carbon isotope measurements were made on samples collected at 2 cm
intervals. Concentration of chemical element was measured at
5 cm intervals. Samples were sealed in the field before they were
taken to laboratory for analyses.
Twelve organic-rich bulk samples were measured using the
conventional method. Radiocarbon ages were calculated with a
half-life of 5568 year and were calibrated to the calendar ages
using Calib 5.0 program (Stuiver et al., 2005). The chronological sequence for this core was established based on the mean sedimentation rate between the two adjacent calibrated ages using linear
interpolation for samples.
For organic carbon isotope (d13Corg) measurement, samples
were acid-washed with 5% HCl to remove possible trace amounts
of carbonate, rinsed with de-ionized water and oven dried at
50 °C. According to organic carbon content, about 20 mg sediment
163
of each sample was combusted in excess of oxygen at 1020 °C by
an elemental analyzer. The d13Corg of produced CO2 was measured
using a Finnigan MAT-253 Mass Spectrometer. The analytical error
is 0.1‰. Results are reported in the d notation relative to the international PDB standard in per mil (‰) (Craig, 1957).
Bulk dry density (DD) was measured as the weight of the dry
mass per unit volume (Janssens, 1983). Dry mass was determined
by oven drying at 50 °C until constant weight was achieved. Total
organic carbon (TOC) and total nitrogen (TN) were determined by
a CE Model 440 Elemental Analyzer after treating samples with 1 N
HCl. OM was analyzed using the potassium dichromate-vitriol oxidation titration technique proposed by Walkley (1947) with an
uncertainty of 0.2%. According to DD, OM, and sedimentation rate,
we calculate the accumulation rate of OM (OM–AR,
mg cm3 year1).
Grain size distribution was determined using a Malvern Mastersizer-2000 Analyzer. Samples were pretreated with 10–20 ml of
30% H2O2 to remove organic matter and then with 10 ml of 10%
HCl to remove carbonates. About 2000 ml of deionized water were
added, then the sample solution was kept for 24 h to rinse acidic
ions. The sample residue was finally treated with 10 ml of 0.05 M
(NaPO3)6 on an ultrasonic vibrator for 10 min to facilitate dispersion before grain size analysis. The Mastersizer-2000 automatically
yields the median diameter and the percentages of the related size
fractions of a sample with a relative error of less than 1%. The median grain size (Md) of a sample is the diameter at the 50th percentile of the distribution.
Mass magnetic susceptibility (SI) was measured using Bartington MS-2 Magnetic Susceptibility Meter after sample was dried
at 38 °C for 48 h. Concentrations of rubidium (Rb) and strontium
(Sr) were analyzed using VP-320 X-ray fluorescence (XRF) spectrometer after samples being ground to fine powder <38 lm. The
error is less than 1 ppm.
4. Analytical results
For core K02, radiocarbon dating results and the relationship
between age and depth are shown in Table 1 and Fig. 2. The bottom
age of core K02 was determined at ca. 16,000 cal year BP. Sediments from 0 to 20 cm of this core are composed of greyish-green
silt or silty clay, underlain by a brown herb-rich peat layer (from 20
to 65 cm depth). The sequence from 65 to 110 cm is composed of
greyish green silt or silty clay, and sediments from 110 to
140 cm consist of dark grey or black organic mud. From 140 to
Fig. 1. Climatic background of the study region (modified after Peng et al., 2005) and the location of core K02 in Dahu Swamp. The positions of top soil samples around the
swamp were also indicated.
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Z. Wei et al. / Journal of Asian Earth Sciences 38 (2010) 162–169
Table 1
Radiocarbon dating results of core K02 in Dahu Swamp.
Laboratory number
Sample number
Depth (cm)
Conventional
07-119
07-121
07-123
07-124
07-125
07-127
07-128
07-147
07-148
07-149
07-150
07-151
JXDN-01-01
JXDN-01-03
JXDN-01-05
JXDN-01-06
JXDN-01-07
JXDN-01-09
JXDN-01-10
JXDN-01-11
JXDN-01-12
JXDN-01-13
JXDN-01-14
JXDN-01-15
5–10
33–38
78–83
110–115
131–136
175–180
200–205
220–225
235–240
270–275
285–290
343–348
1711 ± 64
4468 ± 80
6421 ± 76
7319 ± 89
7961 ± 106
8555 ± 122
9742 ± 102
10,180 ± 108
11,565 ± 109
12,160 ± 91
12,798 ± 126
13,410 ± 155
14
C age (year BP)
Calibrated age (cal year BP)
2 sigma
Intercept
1420–1815
4874–5307
7174–7466
7972–8329
8544–9113
9621–10,112
10,746–11,387
11,348–12,352
13,225–13,672
13,780–14,259
14,642–15,568
15,386–16,477
1617
5090
7320
8150
8828
9866
11,066
11,850
13,448
14,019
15,105
15,931
Material
TOC
TOC
TOC
TOC
TOC
TOC
TOC
TOC
TOC
TOC
TOC
TOC
Fig. 2. Stratigraphy and the relationship between age and depth of core K02. Sedimentation rates between the two adjacent calibrated ages are presented in years per cm
(year/cm).
215 cm depth, sediments are characterized by grey green or yellow
brown silt or silty clay, underlain by dark grey organic mud (from
215 to 245 cm depth). Between 245 and 320 cm, sediments are
composed of two brown herb-rich peat layers at depth from 245
to 280 cm and from 310 to 320 cm, intercalated with a layer of
dark brown organic mud (from 280 to 310 cm depth). In the lowest
part between 320 and 350 cm, sediments consist of grayish green
silty clay bearing some terrestrial tree remains, underlain by greyish fine gravel and coarse sand (Fig. 2).
Dry bulk density (DD), which give a first impression about the
input of clastic material into the lake, clearly revealing an enhanced input during the early and mid-Holocene (from 10,000 to
6000 cal year BP) and the late Holocene (from 3000 cal year BP
afterwards) (Fig. 3). During the time period from 16,000 to
10,000 cal year BP, DD generally show low values, although several
excursions characterized by relatively high values occurred. SI and
Rb/Sr ratio correlate positively with DD, while OM and Md show an
inverse correlation. TOC/TN ratios are normally above 25 and reveal two periods with relatively high values from 16,000 to
11,000 cal year BP and from 6000 to 3000 cal year BP. OM–AR is
low between 16,000 and 10,000 cal year BP and from 3000 cal year
BP afterwards. Bulk d13Corg values show variation within a broad
range of 4.1‰ with values mainly between 31.1 and 27.3‰. Evident negative d13Corg values characterize the early and mid-Holocene (from 10,000 to 6000 cal year BP), then bulk d13Corg displays
a distinct transition towards positive values after 6000 cal year
BP. In general, relatively more positive d13Corg values exhibit during
the Last Deglaciation, however, two excursions characterized by
relatively negative d13Corg appeared between ca.15,000 and
14,000 cal year BP and between ca. 13,500 and 12,800 cal year BP
(Fig. 3).
Carbon isotope signatures of modern plants that dominate the
catchment of Dahu Swamp and six surface soil samples around this
swamp are given in Table. 2. All data points fluctuate within a
range from 27.3 to 31.8‰, showing a strong signature of C3
plants (Ballentine et al., 1998).
5. Organic matter sources and potential environmental
implication of bulk organic carbon isotope
Because particulate OM buried in lake sediments is often a mixture of material derived from different sources (e.g., terrestrial
plants, aquatic macrophytes and plankton; Meyers, 1994), in order
to use carbon isotopes of sedimentary OM as an indicator of environmental and climatic changes, potential effects that weaken the
indicative strength of the isotopic signal have to be discussed,
identified and eliminated.
Changing proportions of OM from various sources can induce
carbon isotope variations in the lacustrine sedimentary record,
which may mask the relation between isotope value, environment
and the respective forcing factors. Generally, the d13Corg derived
from lacustrine primary production depends on the availability
Z. Wei et al. / Journal of Asian Earth Sciences 38 (2010) 162–169
165
Fig. 3. Variations of bulk d13Corg, OM, TOC/TN, Md, OM–AR, DD, SI, and Rb/Sr ratio in core K02. Grey bar indicates the dry phase.
Table 2
d13Corg values of modern dominant plant species and six samples of surface soil around Dahu Swamp.
d13Corg of plant species(‰)
Cunninghamia lancedata (Lamb) Hook
Gahnia tristis Nees.
Dicranopteris dichotoma (Thunb) Bernh
Syzygium championii (Benth.) Merr.et Perry
Camellia oleifera Abel
Ficus pumila Linu.
Pinus massoniana L.
Rhaphiolepis indica (L) Lindl.
Rhodoendron simsii Planch
Litsea cubeba (Lour.) Pers.
29.2
28.0
30.0
31.7
27.6
30.1
31.1
29.3
28.9
29.3
Callicarpa rubella Lindl.
Castanopsis fissa (Champ.ex Benth.) Rehd.et wits
Blechnum orientale Linn.
Rubus reflexus ker.
Ficus hirta Vahl
Cedrela toona Roxb
Rubus pirifolius Sm.
Viburnum fordiae Hance
Maesa perlarius (Lour.) Merr.
27.3
30.6
30.7
29.5
31.0
31.8
30.8
29.3
29.6
d13Corg of top soil samples(‰)
DHS-1
DHS-3
DHS-5
27.4
28.2
27.9
DHS-2
DHS-4
DHS-6
27.7
27.8
28.1
of dissolved CO2 as the inorganic carbon source and on the amount
of primary production (Laws et al., 1995). Ambient environmental
conditions additionally influence growth and productivity of lacustrine algae through the control of nutrient availability ([CO2]aq, silica, phosphorus, nitrate), climate, and water temperature
(Goldman and Carpenter, 1974; Rhee and Gotham, 1981). Each of
these sources is characterized by different carbon isotopic values
(O’Leary, 1988). Primary producers and macrophytes have wideranging d13Corg values from 27.0 to 17.0‰ (Ku et al., 2007). A
previous study (Lücke et al., 2003) has pointed out that in the
mid-latitudes of the Northern Hemisphere organic carbon derived
from land plants and aquatic macrophytes is characterized by
d13Corg values in general higher than 28.0‰ (e.g., Osmond et al.,
1981; LaZerte, 1983; Meyers and Ishiwatari, 1995) while lacustrine
algae, respectively, lacustrine sediments normally show values below 25.0‰. The latter one can even decrease to values as low as
36.0‰ (LaZerte, 1983; Mayer and Schwark, 1999). On the other
hand, the source of terrestrial plants is dominated by three distinct
vegetation groups, the C3, C4, and the CAM plants which employ
different photosynthetic pathways and produce different d13Corg
values. In the Northern Hemisphere, the C3 plants are characterized by d13Corg between 34.0 and 22.0‰ with an average value
around 27.0‰; while the C4 plants normally show values between 17.0 and 9.0‰ (Ballentine et al., 1998). The CAM plants,
which are mainly distributed in arid areas, use either the C3 or the
C4 pathway and their d13Corg values reported in most cases are in
the range of 20 to 10‰ (Osmond et al., 1982; Hong et al.,
2001). In Dahu Swamp, bulk d13Corg values of core K02 are lower
than 27.0‰ during the most of studied period (Fig. 3). Besides,
d13Corg values of the modern dominant plants in the catchment
and surface soil samples show a similar carbon isotopic signature
of C3 plants (Table 2). Obviously, terrestrial and lacustrine organic
matter cannot be distinguished clearly by the carbon isotope signature in this case.
Since Dahu Swamp is hydrologically closed, input of materials
to this lake is mainly derived from the surrounding hilly area and
transported by the surface runoff. Stratigraphy of this lake characterized by shifts between the organic-poor greyish green or brown
silt or silty clay and the marshy sediments (peat or organic mud)
can represent past hydrological variations. As illustrated in Fig. 3,
more positive d13Corg, as well as high OM values, generally correspond to the marshy sediments and vice versa, implying that
shrinkage of the water body of Dahu Swamp would lead to intrusion of the terrestrial and near shore aquatic plants and result in
higher OM values, whereas expansion of water body will reduce
OM content.
TOC/TN ratio has been frequently utilized to infer predominance of autochthonous versus allochthonous sources of OM
(e.g., Meyers, 1994; Hassan et al., 1997; Kaushal and Binford,
1999; Mackie et al., 2005; Mayr et al., 2009). The TOC/TN ratio of
aquatic plants and lacustrine plankton is only about 5–12, generally less than 10, while that of terrestrial plants is 20–30 and can
reach 45–50 (Stuiver, 1975; Krishnamurthy et al., 1986; Meyers
and Ishiwatari, 1995; Shen et al., 2005) although lake-internal
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Z. Wei et al. / Journal of Asian Earth Sciences 38 (2010) 162–169
processes such as N-limitation can also produce elevated C/N ratios
in aquatic organic matter (Hecky et al., 1993; Talbot and Lærdal,
2000). The relatively stable TOC/TN ratios, more than 25 for most
of the investigated time period in Dahu Swamp (Fig. 3), suggest
that the organic matter is mainly from allochthonous sources.
Additional evidence for a mainly allochthonous source of OM at
Dahu Swamp arises as a correlation between TOC/TN and OM–AR
(Fig. 3). It has been considered that higher nutrient availability
and increased OM production rate should lead to 13C-enriched
OM (Lücke et al., 2003) and increased d13Corg values have to be
accompanied by higher OM–AR due to an increased carbon flux
to the sediments (Hollander et al., 1992). However, in our case,
OM–AR shows strong negative correlation with the OM record,
lower OM–AR values are synchronous with peat or organic-rich
sediments, whereas higher OM–AR values coincide with organicpoor sediments. This phenomenon implies that sedimentation rate
plays a key role in the OM–AR. Input of terrestrial clastic materials,
which is influenced strongly by hydrological conditions over Dahu
Swamp, is the key factor controlling sedimentation rate.
In addition, DD, Md, Rb/Sr ratio, and SI, which are often considered to be the responses to changes in input of terrestrial clastic
materials to lakes in relation to hydrological changes (Thompson
et al., 1975; Janssens, 1983; Jin et al., 2004; Peng et al., 2005), correlate inversely with bulk d13Corg record (Fig. 3). Stronger surface
runoff (thus implying wetter climatic conditions) would favor high
input of clastic materials to Dahu Swamp, resulting in increases in
DD and SI. Though input of clastic materials would be enhanced
during wetter period, however, weaker surface erosion due to increase in vegetation cover would result in less input of coarser
materials thus leading to lower Md values in sediments and vice
versa. Rb/Sr ratio shows strong correlation to DD, suggesting that
though Rb is stable while Sr readily passes into solution, more clastic materials transported into Dahu Swamp would favor relatively
high Sr content.
Based on above discussion, we believe that terrestrial source
may have played a key role in contribution to OM in the sediments
of Dahu Swamp. Of course, autochthonous source of OM may also
contribute to accumulation of OM in sediments; however, its contribution may be less than the allochthonous source. Nevertheless,
problems still exist concerning a detailed separation of the factors
responsible for the carbon isotopic variation of terrestrial OM.
The relative abundance of C3/C4 plants is often considered to
influence variation of the d13Corg in terrestrial source of OM; however, our bulk d13Corg record shows a strong signature of C3 plants.
For the terrestrial C3 plants, both the atmospheric CO2 concentration and climate can affect their d13Corg features (Krishnamurthy
and Epstein, 1990). According to Feng and Epstein’s (1995) study,
100 ppm increase in atmospheric CO2 will cause 2.0 ± 0.1% more
negative deflection for d13Corg values of the C3 plants. For the past
16,000 years, the amplitude of variation in CO2 did not exceed
30 ppm (Stauffer et al., 1998); therefore, the influence of atmospheric CO2 on d13Corg value of terrestrial C3 plants in the catchment of Dahu Swamp was negligible.
In North China, investigations on modern C3 plants revealed
that the d13Corg values become more negative when temperature
increase (Wei et al., 1997; Wang et al., 2002), a temperature increase by 1 °C will cause a decrease of d13Corg value of C3 plants
by 0.3%. Although evident drop of temperature may have occurred in the last 16,000 years in South China, however, the amplitude of 4.1% in variation of d13Corg values in core K02 is unlikely
caused by change of temperature. A number of studies have documented that the d13Corg values of terrestrial C3 plants are sensitive
to humidity or precipitation, in general, the more negative d13Corg
values, the more precipitation or soil water content and vice versa
(White et al., 1994; Hatté et al., 2001; Hong et al., 2001; Wang and
Han, 2001; Liu et al., 2005b; Chen et al., 2006). Though the exact
relationship between the d13Corg values of C3 plants and precipitation in South China remains unclear, we believe that more negative
d13Corg values of core K02 would indicate relatively wetter environmental conditions, whereas more positive d13Corg values imply a
direr climate. However, an existing problem has to be pointed
out, owing to Dahu Swamp had been dried up many years ago,
no reliable estimation can be made with regard to the contribution
of changing aquatic macrophytes and algal associations to carbon
isotope variations.
To summarize, multiproxies support the potential of bulk stable
carbon isotopes from core K02 to serve as a proxy to reflect
changes of ecological environment in Dahu Swamp catchment
throughout the Holocene and the Last Deglaciation. The organic
carbon isotope record of Dahu Swamp sediments shows a distinct
variation, suggesting that the dynamics of the ecosystem has been
experienced evident changes. These changes are closely related to
atmospheric precipitation derived from the East Asia (EA) summer
monsoon. Our study on core K02 reflects a relationship between
bulk organic carbon isotopes and the EA summer monsoon
strength, the more negative the d13Corg the stronger the EA monsoonal precipitation and vice versa. Because climatic changes in
the EA monsoon-influenced regions are generally assumed to appear as a combination of cold and dry or of wet and warm conditions in response to the weakening or strengthening of the
summer monsoon, respectively (Yao et al., 1996; Herzschuh,
2006), we infer that variations of relatively dry and wet climate
may reflect relatively cold and warm conditions as well.
6. Variation of monsoonal precipitation and its impact on
environmental changes of Dahu Swamp catchment
In Fig. 3, relatively evident dry and wet phases reflected by multiproxy records were label as C1C4 and W1W4, respectively.
During the Last Deglaciation (from 16,000 to 10,000 cal year BP),
bulk d13Corg values vary between 30.6 and 27.3‰ with an average value of 29.0‰. As illustrated in Figs. 3 and 4, within the reasonable accuracy of our age model, relatively more positive d13Corg,
high DD, and low OMAR values reflect three relatively dry phases
occurred between ca. 16,000 and 15,000 cal year BP (C1), between
ca. 14,000 and 13,500 cal year BP (C2) and between 12,800 and
11,500 cal year BP (C3), which possibly coincide with the Oldest,
Older and Younger Dryas (YD) cooling events, respectively.
Relatively positive d13Corg values during these dry (cold) periods
imply a corresponding decline of carbon isotope ratios in terrestrial
C3 plants. Two wet intervals indicated by more negative d13Corg,
low DD, and high OM–AR values appeared between ca. 15,000
and 14,000 cal year BP (W1) and between ca. 13,500 and
12,800 cal year BP (W2), may correspond to the Bølling and Allerød
warming events (Fig. 4).
In Holocene (from 10,000 cal year BP afterwards), bulk d13Corg
values vary between 31.4 and 27.9‰ with a mean value of
29.9‰. Previous studies had demonstrated that during the early
and mid-Holocene, a strengthening of the EA summer monsoon
precipitation characterized this period in South China (Zhou
et al., 2004; Wang et al., 2007; Xue et al., 2009). Between ca.
10,000 and 6000 cal year BP, more negative d13Corg and high values
of OMAR, DD, SI, and Rb/Sr ratio evidently reflect a wet period
(W3) that coincides with the 25°N summer solar insolation maximum. An enhanced precipitation during this period resulted in increases in DD and OM–AR, as well as more depleted d13Corg values
of terrestrial C3 plants in the catchment of Dahu Swamp (Fig. 4).
This period shows a nature of the Holocene Optimum period, but
appears to differ from the traditional Holocene optimum in China
(lasting from ca. 8500 to 3000 cal year BP) (Shi et al., 1993), and
does not follow the conceptual model that the Holocene Optimum
Z. Wei et al. / Journal of Asian Earth Sciences 38 (2010) 162–169
167
Fig. 4. Comparison between Dahu records and the regional and global climate proxy data. (A) bulk d13Corg record, (B) OM–AR, and (C) DD of core K02 in Dahu Swamp; (D) the
25°N summer solar insolation (Berger and Loutre, 1991); (E) d18O record of the Dongge Cave stalagmite (Dykoski et al., 2005); (F) d18O record of the GISP2 ice core (Grootes
et al., 1993). Grey bar indicates the dry (cold) phase.
reached a maximum at ca. 3000 cal year BP in South China (An
et al., 2000).
A dry period following the trend with decreasing solar insolation for the mid-Holocene, was widely discovered in South and
Southwest China (Zhou et al., 2004; Dykoski et al., 2005; Wang
et al., 2007) and on Tibetan Plateau (Thompson et al., 1997). In
Fig. 3 and 4, it can be observed that low values of OMAR, SI,
DD, and Rb/Sr, as well as high Md and OM values together with a
40cm thick peat layer (from 15 to 65 cm depth) demonstrate a
pronounced dry mid-Holocene period (from ca. 6000 to 3000 cal year BP) (C4). Dry conditions would lead to 13C-enriched organic
matter, thus resulting in a trend of d13Corg shift towards more positive after 6000 cal year BP.
However, we cannot ascertain carbon isotopic situation during
the period from 3000 cal year BP afterwards, because anthropogenic influence was strengthened since 3000 cal year BP in the
study area (Zhou et al., 2004; Xiao et al., 2007). More positive bulk
d13Corg values during this period (Fig. 4) possibly suggest a
strengthened human’s agricultural activity.
The East Asia monsoon, one of the most important components
of the global climatic system, plays an important role in changes of
ecosystem in South China. Our bulk d13Corg record, together with
other multiproxies indicate that variation of precipitation over
the study area is closely related to the strengthening or weakening
of the EA summer monsoon, and agrees well with the d18O record
of Chinese stalagmite in Southwest China (Dykoski et al., 2005;
Wang et al., 2005) and with the 25°N summer solar insolation
(Berger and Loutre, 1991), implying a linear response to the Earth’s
orbital parameters. Nevertheless, the cold SST and LaNina condi-
tions were thought to account for the aridity during the mid-Holocene period in the EA monsoon-influenced areas as well (Riedinger
et al., 2002; Zhou et al., 2004).
7. Conclusions
Bulk organic carbon isotopes are usually considered as an integrating parameter characterizing the biological system of a lake
(Lücke et al., 2003). However, a direct interpretation on bulk
d13Corg record of lake sediments in terms of climate changes is
not guaranteed. In Dahu Swamp, a site in South China, bulk d13Corg
record, as well as multiproxies including lithological variation, OM,
OM–AR, TOC/TN, DD, Md, SI, and Rb/Sr ratio, suggests that terrestrial sources of OM, which are influenced strongly by climatic conditions, may play a more important role than the primary
production in contribution to accumulation of OM in Dahu Swamp,
and therefore, bulk d13Corg record was considered a proxy reflecting
carbon isotope signal of terrestrial C3 plants, on which atmospheric precipitation may exert a strong impact. On the other hand,
although owing to low altitude of the geographic location, Dahu
Swamp is thought to be vulnerably influenced by the organic ‘‘contaminations” from various potential sources of OM, multiproxies
demonstrated that bulk d13Corg record has the potential to indicate
the input of terrestrial OM and has a clear reflection of ecological
environment in the catchment that was closely related to climatic
changes. Even if the causes and mechanisms leading to the observed organic carbon isotope responses are presently not fully
understood, they are manifestations of terrestrial ecosystem rather
than externally forced changes of lake primary production. Despite
168
Z. Wei et al. / Journal of Asian Earth Sciences 38 (2010) 162–169
the rather high time resolution of our record, possible lag effects
can yet not be resolved in detail, however, coinciding variations
of bulk d13Corg record, as well as other multiproxies, and climatic
features of the South China testify not only the strong impact of
the EA monsoon circulation patterns on local environment of the
study area, but also the excellent and sensitive recording of South
China climate conditions.
Acknowledgements
Analysis of radiocarbon date was conducted at the Key Lab. of
Western China’s Environmental Systems (Ministry of Education of
China), Lanzhou University. Bulk organic carbon isotope was analyzed in Sate Key Lab. of Gas Geochemistry, Lanzhou Institute of
Geology, CAS. We feel grateful to Prof. C.J. Zhang, Dr. H. Yang, Prof.
J.X. Cao and Prof. S.J. Xu for their help with laboratory analyses. We
appreciate K. Refsnider in University of Wisconsin-Madison and
Dr. H.Y. Zhou in Guangzhou Institute of Geochemistry, CAS for language improvement. The authors sincerely thank the anonymous
reviewers for their thorough comments and constructive suggestions, which significantly improved the manuscript. This work was
supported by the NSF of China (No. 40671189), NSF of Guangdong
Province (Nos. 8151063101000044 and 06025042) and the Fok Ying
Tung Education Foundation Grants (No. 91021).
References
Aaron, F.D., William, P.P., Chris, H., Henry, T.M., 2008. Carbon isotopes of marl and
lake sediment organic matter reflect terrestrial landscape change during the
late Glacial and early Holocene (16,800–5540 cal yr BP): a multiproxy study of
lacustrine sediments at Lough Inchiquin, western Ireland. Journal of
Paleolimnology 39, 101–115.
An, Z.S., Porter, S.C., Kutzbach, J.E., Wu, X.H., Wang, S.M., Liu, X.D., Li, X.Q., Zhou, W.J.,
2000. Asynchronous Holocene optimum of the East Asian monsoon. Quaternary
Science Reviews 19, 743–762.
Anderson, N.J., Odgaard, B.V., Segerstrom, U., Renberg, I., 1996. Climate-lake
interactions recorded in varved sediments from a Swedish boreal forest lake.
Global Change Biology 2, 399–405.
Andreas, L., Gerhard, H.S., Bernd, Z., Negendank, J.F.W., 2003. A Late glacial and
Holocene organic carbon isotope record of lacustrine palaeoproductivity and
climatic change derived from varved lake sediments of Lake Holzmaar,
Germany. Quaternary Science Reviews 22, 569–580.
Ballentine, D.C., Macko, S.A., Turekian, V.C., 1998. Variability of stable carbon from
combustion of C4 and C3 plants: implications for biomass burning. Chemical
Geology 152, 151–161.
Berger, A., Loutre, M.F., 1991. Insolation values for the climate of the last 10 million
years. Quaternary Science Reviews 10, 297–317.
Brown, H., Eakin, P.A., Fallick, A.E., Creer, K., 1991. Variations in the carbon isotopic
composition of organic matter in lacustrine sediments of Meerfelder Maar. In:
Manning, D. (Ed.), Organic Geochemistry. Manchester University Press,
Manchester, pp. 352–354.
Chen, F.H., Rao, Z.G., Zhang, J.W., Jin, M., Ma, J.Y., 2006. Variations of organic carbon
isotopic composition and its environmental significance during the last glacial
on western Chinese Loess Plateau. Chinese Science Bulletin 51, 1593–1602.
China Vegetation Editing Committee, 1980. China Vegetation. Science Press, Beijing,
pp. 272–273 (in Chinese).
Craig, H., 1957. Isotopic standards for carbon and oxygen and correction factors for
mass-spectrometric analysis of carbon dioxide. Geochimica et Cosmochimica
Acta 12, 133–149.
Dykoski, C.A., Edwards, R.L., Cheng, H., Yuan, D.X., Cai, Y.J., Zhang, M.L., Lin, Y., An,
Z.S., Revenaugh, J., 2005. A high-resolution, absolute-dated Holocene and
deglacial Asian monsoon record from Dongge Cave, China. Earth and Planetary
Science Letters 233, 71–86.
Feng, X., Epstein, S., 1995. Carbon isotopes of trees from arid environments and
implications for reconstructing atmospheric CO2 concentration. Geochimica et
Cosmochimica Acta 59, 2599–2608.
Goldman, J.C., Carpenter, E.J., 1974. A kinetic approach to the effect of temperature
on algal growth. Limnology and Oceanography 19, 756–766.
Grootes, P.M., Stuive, M., White, J.W.C., Johnson, S., Jouzel, J., 1993. Comparison of
oxygen isotope records from the GISP2 and GRIP Greenland ice cores. Nature
366, 552–554.
Hassan, K.M., Swineheart, J.B., Spalding, R.F., 1997. Evidence for Holocene
environmental change from C/N ratios, and d13C and d15N values in Swan
Lake, western Sand Hills, Nebraska. Journal of Paleolimnology 18, 121–130.
Hatté, C., Antoine, P., Fontugne, M., Lang, A., Rousseau, D., Zöller, L., 2001. d13C of
loess organic matter as a potential proxy for paleoprecipitation. Quaternary
Research 55, 33–38.
Hecky, R.E., Campbell, P., Hendzel, L.L., 1993. The stoichiometry of carbon, nitrogen,
and phosphorus in particulate matter of lakes and oceans. Limnology &
Oceanography 38, 709–724.
Herzschuh, U., 2006. Palaeo-moisture evolution in monsoonal Central Asia during
the last 50,000 years. Quaternary Science Reviews 25, 163–178.
Hollander, D.J., McKenzie, J.A., ten Haven, H.Lo., 1992. A 200 year sedimentary
record of progressive eutrophication in Lake Greifen (Switzerland): implications
for the origin of organic-carbon-rich sediments. Geology 20, 825–828.
Hong, Y.T., Wang, Z.G., Jiang, H.B., Lin, Q.H., Hong, B., Zhu, Y.X., 2001. A 6000-year
record of changes in drought and precipitation in northeastern China based on a
d13C time series from peat cellulose. Earth and Planetary Science Letters 185,
111–119.
Janssens, J.A., 1983. A quantitative method for stratigraphic analysis of bryophytes
in Holocene peat. Journal of Ecology 171, 189–196.
Jin, Z.D., Wu, J.L., Cao, J.J., Wang, S.M., Shen, J., Gao, N.H., Zou, C.J., 2004. Holocene
chemical weathering and climatic oscillations in north China: evidence from
lacustrine sediments. Boreas 33, 260–266.
Kaushal, S., Binford, M.W., 1999. Relationship between C:N ratios of lake sediments,
organic matter sources, and historical deforestation in Lake Pleasant,
Massachusetts, USA. Journal of Paleolimnology 22, 439–442.
Krishnamurthy, R.V., Epstein, S., 1990. Glacial-interglacial excursion in the
concentration of atmospheric CO2: effect in the13C/12C ratio in wood
cellulose. Tellus 42B, 423–434.
Krishnamurthy, R.V., Bhattacharya, S.K., Kusumgar, S., 1986. Palaeoclimatic changes
deduced from13C/12C and C/N ratios of Karewa lake sediments, India. Nature
323, 150–152.
Ku, H.W., Chen, Y.G., Chan, P.S., Liu, H.C., Lin, C.C., 2007. Paleoenvironmental
evolution as revealed by analysis of organic carbon and nitrogen: a case of
coastal Taipei Basin in Northern Taiwan. Geochemical Journal 41, 111–120.
Laws, E.A., Popp, B.N., Bidigare, R.R., Kennicutt, M.C., Macko, S.A., 1995. Dependence
of phytoplankton carbon isotopic composition on growth rate and [CO2]aq:
theoretical considerations and experimental results. Geochimica et
Cosmochimica Acta 59, 1131–1138.
Leng, M.J., Marshall, J.D., 2004. Palaeoclimate interpretation of stable isotope data
from lake sediment archives. Quaternary Science Reviews 23, 811–831.
LaZerte, B.D., 1983. Stable carbon isotope ratios: implications for the source of
sediment carbon and for phytoplankton carbon assimilation in Lake
Memphremagog, Quebec. Canadian Journal of Fisheries and Aquatic Sciences
40, 1658–1666.
Liu, Q., Gu, Z.Y., Liu, J.Q., You, H.T., Lü, H.Y., Chu, G.Q., Qi, X.L., Negendank, J.F.W.,
Mingram, J., Schettler, G., 2005a. Bulk organic carbon isotopic record of
Huguangyan Marr lake, southernwastern China and its paleoclimatic and
paleoenvironmental significance since 62 ka BP. Marine Geology & Quaternary
Geology 25, 115–125 (in Chinese).
Liu, W.G., Feng, X.H., Ning, Y.F., 2005b. Delta C-13 variation of C3 and C4 plants
across an Asian monsoon rainfall gradient in arid northwestern China. Global
Change B 11, 1094–1100.
Lücke, A.L., Schleser, G.H., Zolitschka, B., Negendank, J.F.W., 2003. A Lateglacial and
Holocene organic carbon isotope record of lacustrine palaeoproductivity and
climatic change derived from varved lake sediments of Lake Holzmaar,
Germany. Quaternary Science Reviews 22, 569–580.
Lücke, A., Brauer, A., 2004. Biogeochemical and micro-facial fingerprints of
ecosystem response to rapid Late Glacial climatic changes in varved
sediments of Meerfelder Maar, Germany. Palaeogeography, Palaeoclimatology,
Palaeoecology 211, 139–155.
Mackie, E.A., Leng, M.J., Lloyd, J.M., Arrowsmith, C., 2005. Bulk organic d13C and C/N
ratios as palaeosalinity indicators within a Scottish isolation basin. Journal of
Quaternary Science 20, 303–312.
Mayer, B., Schwark, L., 1999. A 15,000-year stable isotope record from sediments of
Lake Steisslingen, Southwest Germany. Chemical Geology 161, 315–337.
Meyers, P.A., Ishiwatari, R., 1993. Lacustrine organic geochemistry – an overview of
indicators of organic matter sources and diagenesis in lake sediments. Organic
Geochemistry 20, 867–900.
Meyers, P.A., Horie, S., 1993. An organic carbon isotopic record of glacial–postglacial
change in atmospheric pCO2 in the sediments of Lake Biwa, Japan.
Palaeogeography, Palaeoclimatology, Palaeoecology 105, 171–178.
Meyers, P.A., 1994. Preservation of elemental and isotopic source identification of
sedimentary organic matter. Chemical Geology 114, 289–302.
Meyers, P.A., Ishiwatari, R., 1995. Organic matter accumulation records in lake
sediments. In: Lerman, A., Imboden, D., Gat, J. (Eds.), Physics and Chemistry of
Lakes. Springer, Berlin, pp. 279–328.
Mayr, C., Lücke, A., Maidana, N.I., Wille, M., Haberzettl, T., Corbella, H., Ohlendorf, C.,
Schäbitz, F., Fey, M., Janssen, J., Zolitschka, B., 2009. Isotopic fingerprints on
lacustrine organic matter from Laguna Potrok Aike (southern Patagonia,
Argentina) reflect environmental changes during the last 16,000 years. Journal
of Paleolimnology 42, 81–102.
O’Leary, M.H., 1988. Carbon isotopes in photosynthesis. BioSciences 38, 328–336.
Osmond, C.B., Valaane, N., Haslam, S.M., Votila, P., Roksandic, Z., 1981. Comparisons
of d13C values in leaves of aquatic macrophytes from different habitats in Britain
and Finland: some implications for photosynthesis processes in aquatic plants.
Oecologia 50, 117–124.
Osmond, C.B., Winter, K., Ziegler, H., 1982. Functional significance of different
pathways of CO2 fixation in photosynthesis. In: Lange, O.L., Nobel, P.S., Osmond,
C.B., Ziegler, H. (Eds.), Physiological Plant Ecology II. Springer, Berlin, pp. 481–499.
Peng, Y.J., Xiao, J.L., Nakamurab, T., Liu, B.L., Inouchi, Y., 2005. Holocene East Asian
monsoonal precipitation pattern revealed by grain-size distribution of core
Z. Wei et al. / Journal of Asian Earth Sciences 38 (2010) 162–169
sediments of Daihai Lake in Inner Mongolia of north-central China. Earth and
Planetary Science Letters 233, 467–479.
Rhee, G.Y., Gotham, I.J., 1981. The effect of environmental factors on phytoplankton
growth: temperature and the interactions of temperature with nutrient
limitation. Limnology and Oceanography 26, 635–648.
Riedinger, M.A., Steinitz–Kannan, M., Last, W.M., Brenner, M., 2002. A 610014C yr
record of El Ninõ activity from the Galapagos Islands. Journal of Paleoliminology
27, 1–7.
Shen, J., Liu, X.Q., Wang, S.M., Matsumoto, R., 2005. Palaeoclimatic changes in the
Qinghai Lake area during the last 18,000 years. Quaternary International 136,
131–140.
Shi, Y.F., Kong, Z.C., Wang, S.M., Tang, L.Y., Wang, F.B., Yao, T.D., Zhao, X.T., Zhang,
P.Y., Shi, S.H., 1993. The climate and environment during the Holocene
megathermal maximum in China. Science in China, Series B 23, 865–873 (in
Chinese).
Stauffer, B., Blunier, T., Dällenbach, A., Indermühle, A., Schwander, J., Stocker, T.F.,
Tschumi, J., Chappellaz, J., Raynaud, D., Hammer, C.U., Clausen, H.B., 1998.
Atmospheric CO2 concentration and millennial-scale climate change during the
last glacial period. Nature 392, 59–62.
Street-Perrott, F.A., Huang, Y., Perrott, R.A., Eglington, N.G., Barker, P., Khelifa, L.B.,
Harkness, D.D., Olago, D.O., 1997. Impact of lower atmospheric carbon dioxide
on tropical mountain ecosystems. Science 278, 1422–1426.
Stuiver, M., 1975. Climate versus changes in13C content of the organic component of
lake sediments during the late Quaternary. Quaternary Research 5, 251–262.
Stuiver, M., Reimer, P.J., Reimer, R., 2005. CALIB Radiocarbon Calibration. <http://
calib.qub.ac.uk/calib>.
Talbot, M.R., 1990. A review of the palaeohydrological interpretation of carbon and
oxygen isotopic ratios in primary lacustrine carbonates. Chemical Geology 80,
261–279.
Talbot, M.R., Johannessen, T., 1992. A high resolution palaeoclimatic record for the
last 27,500 years in tropical West Africa from the carbon and nitrogen isotopic
composition of lacustrine organic matter. Earth and Planetary Science Letters
10, 23–37.
Talbot, M.R., Lærdal, T., 2000. The Late Pleistocene–Holocene palaeolimnology of
Lake Victoria, East Africa, based upon elemental and isotopic analyses of
sedimentary organic matter. Journal of Paleolimnology 23, 141–164.
169
Thompson, R., Battarbee, R.W., O’Sullivan, P.E., Oldfield, F., 1975. Magnetic
susceptibility of lake sediments. Limnology Oceanography 20, 687–698.
Thompson, L.G., Yao, T.D., Davis, M.E., Henderson, K.A., Mosley-Thompson, E., Lin, P.,
Beer, J., Synal, H.A., ColeDai, J., Olzan, J.F., 1997. Tropical climate instability: the
last glacial cycle from a Qinghai-Tibetan ice core. Science 276, 1821–1825.
Walkley, A., 1947. A critical examination of a rapid method for determination of
organic carbon in soils-effect of variations in digestion conditions and of
inorganic soil constituents. Soil Science 63, 251–257.
Wang, G.A., Han, J.M., Zhou, L.P., 2002. The annual average temperature in northern
China. Chinese Journal of Geology 29, 55–57 (in Chinese).
Wang, G.A., Han, J.M., 2001. between d13C values of C3 plants in northwestern China
and annual precipitation. Chinese Journal of Geology 36, 494–499 (in Chinese).
Wang, S.Y., Lü, H.Y., Liu, J.Q., Negendank, J.F.W., 2007. The early Holocene optimum
inferred from a high-resolution pollen record of Huguangyan Maar Lake in
southern China. Chinese Science Bulletin 52, 2829–2836.
Wang, Y.J., Cheng, H., Edwards, R.L., He, Y.Q., Kong, X.G., An, Z.S., Wu, J.Y., Kelly, M.J.,
Dykoski, C.A., Li, X.D., 2005. The Holocene Asian monsoon: Links to solar
changes and North Atlantic climate. Science 308, 854–857.
Wei, M.J., Dong, J.S., Zhang, J., 1997. The basic characteristic of stable carbon isotopic
composition of the pollen of modern plants in the Chinese Loess Plateau.
Chinese Science Bulletin 42, 725–728 (in Chinese).
White, J.W.C., Ciais, P., Figge, R.A., Kenny, R., Markgraf, V., 1994. A high-resolution
record of atmospheric CO2 content from carbon isotopes in peat. Nature 367,
153–156.
Xiao, J.Y., Lu, H.B., Zhou, W.J., Zhao, Z.J., Hao, R.H., 2007. Evolution of vegetation and
climate since the last glacial maximum recorded at Dahu peat site, South China.
Science in China, Series D 50, 1209–1217.
Xue, J.B., Zhong, W., Zheng, Y.M., Ma, Q.H., Cai, Y., Ouyang, J., 2009. A new highresolution Late Glacial–Holocene climatic record from eastern Nanling
Mountains in South China. Chinese Geographical Science 19, 274–282.
Yao, T.D., Jiao, K.Q., Tian, L.D., Yang, Z., Shi, W., 1996. Climatic variations since the
little ice age recorded in Guliya ice core. Science in China, Series D 39, 587–596.
Zhou, W.J., Yu, X.F., Timothy, J.A.J., Burr, G., Xiao, J.Y., Lu, X.F., Xian, F., 2004. Highresolution evidence from southern China of an early Holocene optimum and a
mid-Holocene dry event during the past 18,000 years. Quaternary Research 62,
39–48.