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Pollen and diatom record of climate and environmental change over the last 170 years in Tingming Lake, Yunnan Province, SW China
Journal Pre-proof Pollen and diatom record of climate and environmental change over the last 170 years in Tingming Lake, Yunnan Province, SW China Bing Song, Lingyang Kong, Zhujun Hu, Qian Wang, Xiangdong Yang PII:
S1040-6182(19)30930-9
DOI:
https://doi.org/10.1016/j.quaint.2019.12.006
Reference:
JQI 8086
To appear in:
Quaternary International
Received Date: 29 August 2019 Revised Date:
3 December 2019
Accepted Date: 4 December 2019
Please cite this article as: Song, B., Kong, L., Hu, Z., Wang, Q., Yang, X., Pollen and diatom record of climate and environmental change over the last 170 years in Tingming Lake, Yunnan Province, SW China, Quaternary International, https://doi.org/10.1016/j.quaint.2019.12.006. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
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Pollen and diatom record of climate and environmental change over the last 170 years in
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Tingming Lake, Yunnan Province, SW China
3 4
Bing Song1*, Lingyang Kong1, Zhujun Hu2, Qian Wang1, Xiangdong Yang1
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1 State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and
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Limnology, Chinese Academy of Sciences, Nanjing, 210008, PR China
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2 School of Geography Science, Nanjing Normal University, Nanjing, China
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Email: Bing Song [email protected]; [email protected]
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Abstract:
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The south-east margin of the Qinghai-Tibet Plateau is highly sensitive to global environmental
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changes. Even near treeline lake areas that are very minimally impacted by human activity are
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sensitive to these global changes. In this study, we used pollen and diatom analyses to reconstruct
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the past vegetation, ecosystem, and climate changes. The pollen record was used to indicate
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vegetation changes and showed that the treeline and the vegetation belt have been generally
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moving upward from 1845 AD to the present. The diatom record showed that the lake level was
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rising along with a warming climate during this period. Comparison of the pollen and diatom
31
records with other records suggests that the ecosystem change in the lake and the adjacent region
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are perhaps mainly impacted by the warming climate.
33 34
Keywords: Pollen, Diatom, Alpine lake, Climate change, Vegetation
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1. Introduction
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Climate is one of the most important driver of ecological and vegetation changes (Parmesan and
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Yohe, 2003; Song et al., 2018; Yan et al., 2018). Pollen and diatom analyses of lake sediments are
39
powerful tools for assessing the effects of climate change on lake ecosystems and the nearby
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vegetation (Xiao et al., 2015; Yan et al., 2018). Previous research using diatoms to reconstruct the
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lake ecosystem has yielded different results. Yan et al. (2018) suggest that the lake ecosystem
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responses to rapid climate warming and that the response of diatom biodiversity to climate is a
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nonlinear process. However, Hu et al. (2014) suggest that catchment-mediated atmospheric
44
nitrogen deposition drives ecological change in the alpine lakes in SE Tibet. Even within the same
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diatom species, such as the Cyclotella taxa, there are different interpretations. Some researches
46
suggest the planktonic diatom Cyclotella taxa has increased remarkably in diatom assemblages in
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alpine, boreal, temperate, and arctic areas in response to climate warming (Gerten and Adrian,
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2002; Perren et al., 2003; Smol et al., 2005; Enache et al., 2011; Yan et al., 2018), but some
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paleolimnological records from several regions show a decrease in the relative trend (Perren and
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Douglas, 2009, Perren et al., 2012; Hobbs et al., 2010; Saros et al., 2011; Yan et al., 2018).
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Previous research has been conducted using pollen from lake to reconstruct the vegetation
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change. Research has mainly focused on the millennium to millennium scale (e.g. Xiao et al.,
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2012; Xiao et al., 2015; Song et al., 2018). There are very few vegetation and climate
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reconstructions focused on the changes that have occurred during the last 200 years. There are also
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many different interpretations for the pollen indicators, such as the increasing Pinus pollen found
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in coastal and off shore areas that indicates fluvial water transport (Yang et al., 2016; Song et al.,
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2017). In the general mountain area, there is a trending cold climate (Song et al., 2018). However,
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in the alpine lake area, especially in the treeline area, the increasing Pinus pollen is exhibiting an
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upward treeline movement (Li et al., 2019). In the same study, the use of pollen and diatom
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analyses to reconstruct the lake ecosystem and nearby vegetation changes in the alpine lake area
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are even scarcer.
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In the southeast margin of the Tibetan Plateau of southwestern China, there are a large number
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of alpine lakes. Previous studies using diatom and algal pigment inferred past environmental
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changes, which suggested that there has been an increasing tendency of climate warming and
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widespread nutrient loading on lakes across the region during the last two hundred years (e.g.
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Wang et al ., 2011; Hu et al., 2014; Kong et al., 2017). However, the research about the ecosystem
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change in the lake and the adjacent region are very scarce in the same study, which prevent our
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understanding for the possible relationship between the ecosystem change in the lake and the
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adjacent region.
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In this study, we used these methods of pollen and diatom to investigate the Tingming Lake
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ecosystem and nearby vegetation changes during the last 170 years to understand the possible
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causes and mechanisms under the background of global climate change.
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2. Geographical background and site description
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Tingming Lake (26035’40”, 99001’30”) is an alpine lake in the western Yunnan Province on the
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southeast edge of the Qinghai-Tibet Plateau, a transition zone from the Hengduan Mountain to the
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Yunnan-Guizhou Plateau (Fig. 1). It lies at an altitude of 3779 m a.s.l. and is very minimally
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impacted by human activity. The maximum depth of the lake is approximately 19.2 m. The
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maximum length of the lake is about 0.84 km and the maximum width is 0.2 km, being about 1.5
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km2. The drainage area is also relatively small, the main source of the sediments come from the
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nearby mountain, and is hydrologically recharged by precipitation, surface runoff, and seasonal
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inflows from the nearby mountain.
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The study region is characterized by an Indian Monsoon climate that is mainly affected by the
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warm-humid airflow from the Indian Ocean and Bengal Bay in summer and by the southern
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branch of the westerly in winter (Xiao et al., 2014). According to the average climatic data from
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the adjacent area, the mean annual temperature in the study area is 2.5 oC and the average annual
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precipitation is about 910 mm (Xiao et al., 2011; Xiao et al., 2014).
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There is an altitudinal gradient in the research area with notable vegetation belts in the alpine
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area in Yunnan (Xiao et al., 2014). The vegetation is mid-montane humid evergreen broadleaved
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forest from 2400-2900 m that is mainly composed of Lithocarpus craibianus, Lithocarpus
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confertifolia, Lithocarpus hancei, and Schima argentea. From approximately 2800-3200 m, the
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vegetation is mainly composed of Tsuga, Abies, Lithocarpus, Betula, Acer, Rhododendron, and
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Sinarundinaria. From about 3100-3900 m, the vegetation is mainly composed of Abies and Picea.
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The forest line is at about 3900 m. Above the forest line, the vegetation is mainly composed of
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alpine Rhododendron shrubland, Kobresia meadow, and alpine tundra (Editorial Board of
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Sichuan’s vegetation, 1980; Wu et al., 1987; Xiao et al., 2014). Generally, the human influence is
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most notable below about 2500 m, where agriculture crops and limited forest cover presents
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vegetation mainly composed of Pinus yunnanensis and Quercus (Xiao et al., 2014).
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3 Materials and methods
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3.1 Coring and sample preparation
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The sediment core of HZY-2 (26035’35.7”, 99001’27.29”) in this study were taken from
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Tingming Lake in 2017. The water depth was 16.1 m. It was taken using a Kajak gravity corer,
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and sampled at 0.5 cm intervals in the field. The sediments mainly consist of darkish clay. In this
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study, the core was drilled about 35 cm from the lake. We only analyzed the upper 22 cm, due to
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the age data limitation.
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3.2 137Cs and 210Pb dating The
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Cs,
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Ra, and
210
Pb dating were performed at the Nanjing Institute of Geography and
Limnology, Chinese Academy of Sciences. Each subsample was 0.5 cm thick and weighed
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between approximately 0.4~2.2 g when freeze-dried. The weight of the samples was used to
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calculate the dry bulk density that is defined as the dry mass per unit wet volume (Sun et al.,
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2018).
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3.3 Palynological and diatom analyses
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The palynological analyses were performed using approximately 2 g of dried sample and one
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tablet of Lycopodium spores (27637±563 grains per tablet). All samples were treated with 10%
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HCl, 10% NaOH, and 2.1 g/cm3 of heavy liquid flotation. The samples were sieved using a 7 µm
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mesh sieve and were identified under ×400 magnification using an Olympus microscope. Each
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sample counted more than 300 grains of pollen and spores. There are not non-pollen
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palynomorphs (algae, cyanobacteria) in the pollen slides. Approximately 0.04 g of dried sample
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were used for the diatom analyses. All samples were treated with 10% HCl and 30% H2O2. The
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diatom valves were counted using an Olympus microscope with an oil immersion objective
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(magnification ×1000). Each sample contained more than 300 counted valves.
125 126
4 Results
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4.1 Age dating and chronologies
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In this study, the 137 Cs data with a peak at a depth of 4.75 cm, indicated at possible date of 1963
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AD in Yunnan, China (Sun et al., 2018). Therefore, we chose the Constant Rate of Supply (CRS)
130
model to calculate the chronologies (Sun et al., 2018) (Fig. 2). The CRS model assumes that the
131
supply of
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vary through time, because many reasons can influence the supply rate of 210Pbex in the lake, such
210
Pbex to the lacustrine sediment was constant, however, the accumulation rate could
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as the increase of organic matters, turbidity currents caused by flood and earthquake events (Sun
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et al., 2018). The 137Cs chronostratigraphic markers for the peak of 137Cs corresponding to the year
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1963 can be incorporated into the CRS model as composite CRS Model to improve the final result.
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The age data were corrected using the cumulative mass rates (g/cm2y-1) (Sun et al., 2018; Hu et al.,
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2014).
138 139
The results showed that the lowest age data was about 1826 AD at a depth of 22.25 m and the sedimentary rates were mainly in the range of 0.1-0.5 cm/yr.
140 141
4.2 Palynology and palynological spectrum
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The palynological data was divided into the following five groups based on their relationship
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with the parent plant and biotope: conifer arboreal pollen (CAP), broad leaf arboreal pollen (BAP),
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shrub(S), terrestrial Herb (TH), aquatic herb (AH), and fern spore (FS) (Fig. 3). The principal
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pollen and spore taxa are shown in the pollen diagrams. Based on the results from the CONISS
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analysis (Grimm, 1991, 1992) and age data, we divided the palynological spectrum into zones I
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and II (Fig. 3)
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Zone I (21.75–9.75 m, 1845–1938 AD).
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In zone I, the proportions of CAP, BAP, S, TH, AH, and FS were approximately 12.8%, 49.6%,
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8.6%, 29.0% 5.6%, and 12.8%, respectively (Fig. 4). Most of the CAP was from Pinus and Tsuga,
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with average proportions of approximately 7.5% and 1.8%, respectively. The BAP was
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predominantly from Quercus (evergreen), Quercus (deciduous), and Alnus, with average
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proportions of about 20.8%, 10.4%, and 7.2%, respectively. Most of the S and TH were from
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Rhododendron, Betula, Ranunculaceae, Cyperaceae, and Gramineae, with average proportions of
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approximately 4.6%, 3.2%, 7.2%, 5.9%, and 4.2%, respectively. The AH and FS were mainly from
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Potamogetonaceae and Polypodiaceae, with average proportion of about 4.8% and 8.8%,
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respectively.
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Zone II (9.75–0 m, 1938–2016 AD).
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In zone II, the proportions of CAP, BAP, S, TH, AH, and FS were approximately 18.5%, 55.0%,
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8.6%, 26.6% 3.3%, and 9.8%, respectively. The CAP mainly consisted of Pinus and Tsuga, with
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average proportions of approximately 10.6% and 6.3%, respectively. Most of the BAP was from
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Quercus (evergreen), Quercus (deciduous), and Alnus, with average proportions of about 19.7%,
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8.5%, and 11.4%, respectively. The S and TH were mainly from Rhododendron, Betula,
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Ranunculaceae, Cyperaceae, and Gramineae, with average proportions of approximately 2.7%,
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2.9%, 2.5%, 6.7%, and 4.9%, respectively. The Potamogetonaceae and Polypodiaceae were
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mainly part of AH and FS, with average proportion of about 2.5% and 6.1%, respectively.
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4.3 Diatom and diatom spectrum
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The diatom data was divided into three groups based on the general habitat (Torbinson and
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Kawecka, 2005; Yan et al., 2018; Li et al., 2018), namely, epiphytic diatom (E diatom), benthic
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diatom (B diatom), and plankton diatom (P diatom). The principle genus and species are shown in
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Fig. 4. The diatom spectrum also references the pollen zones from the results of the CONISS
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analysis (Grimm, 1991, 1992) and age data.
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Zone I (21.75–9.75 m, 1845–1938AD)
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In this zone, the proportions of E diatom, B diatom, and P diatom were 42.8%, 11.1% and
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45.9%, respectively. The dominant species were Achnanthes curtissima and Achnanthes
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Minutissima, with 4.0% and 7.1% in the E diatom group, respectively. In the B diatom group, the
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dominant species were Diatoma sp, Navicula spp with 1.9% and 2.3%, respectively. In the P
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diatom, group the primary species were Aulacoseira alpigena and Cyclotella bodanica with 18.9%
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and 21.7%, respectively.
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Zone II (9.75–0 m, 1938–2016AD)
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In this zone, the proportions of E diatom, B diatom, and P diatom were 22.8%, 26.3%, and
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50.8%, respectively. However, there were some differences compared with zone I. In the E diatom
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group, the dominant species were Achnanthes minutissima and Gomphonema spp with 7.2% and
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2.7%, respectively. The dominant species in the B diatom group were Diatoma sp and Navicula
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spp, with 2.2% and 1.9%, respectively. In the P diatom group, the primary species were
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Aulacoseira alpigena and Cyclotella bodanica, with 9.6% and 37.9%, respectively.
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5 Discussion
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5.1 Vegetation history and treeline movements in the Tingming Lake area
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In the nearby area of Tingming Lake, the vegetation has changed from alpine forest to alpine
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shrub, and finally to alpine meadow and tundra with increasing altitude. From 1845 AD to present,
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the vegetation has in response to natural environmental changes without impacted by human
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activity. There is a rice planting area in the Yunnan Province, however, it is a very scarce
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Gramineae (>40 µm) pollen source recorded in the lake. Additionally, the proportion of CAP
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increased, but S and TH clearly decreased. The proportion of the tree pollens of Pinus and Alnus
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obviously increased and the shrub and TH pollen of Rhododendron and Ranunculaceae obviously
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decreased.
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If the treeline shifts downward to the lakeshore, the shrunken alpine forest and expanded shrub
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meadow areas are expected to input less arboreal pollen, especially Pinus, and more shrub and
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herbaceous pollen, such as, Rhododendron and Ranunculaceae. On the contrary, when the
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vegetation belts move upwards with the conifer forest expanding, the lower limit of the alpine
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shrub and meadow are expected to migrate to the upper slopes, far away from the lakeshore. In
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that case, the shrub and herbaceous pollen would be expected to decrease with increased arboreal
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pollen in the lake (Li et al., 2019). The vegetation change also showed that the treeline and the
210
vegetation belt generally moved upward from 1845 AD to present. The Basomtso in the Tibetan
211
Plateau also has an increased trend in the treeline recorded by increased Pinus pollen after 200 cal
212
yr BP (Li et al., 2019). Liang et al. (2011) reported a minor change in the fir tree‐line position on
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the southeastern Tibetan Plateau after 200 years and an upward tree-line prophase rise due to
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climate warming (Körner, 2003; Holtmeier and Broll, 2007; Harsch et al., 2009).
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5.2 Ecosystem change in Tingming Lake
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The alpine lake environment has changed since 1845 AD. The proportion of P diatoms
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generally increased, and the B and E diatoms relatively decreases compared to the period from
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1938–2016 AD and 1845–1938 AD (Fig. 4). This phenomenon suggests that the lake level was
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rising (Smol and Stoermer, 2010). However, it also may be caused by increased nutrient input that
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stimulates the phytoplankton diatoms and B diatom growth of algae. This limits the light that can
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reach the submerged aquatic plants, inhibiting their ability to photosynthesize and causing
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macrophyte loss (Irvine et al., 1989; Smol and Stoermer, 2010). Meanwhile, the aquatic herb (AH)
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decrease can also arise from two different causes. However, there was a relatively high proportion
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of Aulacoseira (Aul alpigena, Aul valida et al) in 1845–1938 AD that has generally decreased
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since 1938 AD. In general, Aulacoseira thrives in a lake environment with increased turbulence
227
and corresponding nutrient increases during low water stages (Smol and Stoermer, 2010).
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Therefore, the decreased proportion of Aulacoseira perhaps was caused by the rising lake level.
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The decreased fern spores were perhaps also caused by a similar reason. Because the lake level
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was rising, the lake size increased. The sediment cores were collected relatively far from the lake
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shore. Thus, less ferns were transported to the drilling location. The increased percentage of
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Cyclotella bodanica also suggests an increase in the lake level (Li et al., 2018).
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The other diatom species were relatively stable. However, for the P diatoms, there was an
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obvious increase in Cyclotella bodanica and a decrease in Aulacoseira alpigena (Fig. 5). The lake
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changed from a slightly acidic, cold, and oligotrophic low lake to a relatively less acidic, warm,
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and lower nutrient concentration lake (Brache et al., 2008; Li et al ., 2018). In the pollen diagram,
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there was an increasing percentage of Alnus that indicated enhanced microbial nitrogen fixation in
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the soil and indirectly impacted the lake ecosystem through an increased nutrient flux
239
(Pedziszewska et al., 2015; Li et al., 2018). In that case, there was increased flux of nutrients, but
240
there was still a relatively warm and lower nutrient concentration in the Tingming Lake. Therefore,
241
the ecosystem change in the lake was perhaps mainly caused by rising lake water levels from
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warming and wetter climate.
243 244
5.3 Comparison of the pollen and diatom record in the ecosystem and climate change
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The vegetation and lake ecosystem variations were both recorded by the pollen and diatoms
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since 1845 AD. For the mountain vegetation change, there was a general changing trend, such as
247
increased Pinus, Tsuga, and Alnus, and decreased Carya, Rhododendron, and Ranunculaceae,
248
along with others (Fig. 3). The pollen spectrum indicated general climate warming. The diatom
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record in the Tingming Lake ecosystem also displayed similar warming indicators such as the
250
increased P/N-P value, Cyclotella bodanica, and decreased Aulacoseira alpigena (Figs. 4 and 5).
251
Additionally, the general rising lake level suggests a general increase in precipitation. Therefore,
252
the climate is gradually warming and becoming wetter in the research area.
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Comparison of the pollen and diatom records with sea surface temperatures (SST) and
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temperatures across China, Asia, and the globe showed a very similar trend (Climate Change
255
Center of China Meteorological Administration, 2019) (Fig. 6). Perhaps the pollen and diatom
256
record in the ecosystem and climate changes mainly arose from global warming. Generally, the
257
vegetation change followed the global warming trend. However, there are several alternative
258
explanations. Some researchers suggest that catchment-mediated atmospheric nitrogen deposition
259
drives ecological change in alpine lakes in SE Tibet, such as Shade Co and Moon Lake (Hu et al.,
260
2014). Paleolimnological studies have shown that increased Nr deposition is one of the important
261
factors for environmental change (Galloway et al., 2008), especially, in alpine regions without
262
direct human distribution (Wolfe et al., 2003).
263
In this study, the pollen and diatom recorded climate changes were very similar and
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corresponded to other records from the SST, China, Asia, and the globe. The ecosystem changes in
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the lake and the adjacent region identified climate change as the possible culprit although the
266
diatom biodiversity response to climate was nonlinear (Yan et al., 2018).
267 268
6 Conclusion
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In this study, the pollen and diatom record for the ecosystem of Tingming Lake and the adjacent
270
region was investigated. The pollen record for the vegetation change showed that the treeline and
271
the vegetation belt generally moved upward since 1845 AD. The diatom record indicated the lake
272
level was rising along with a warmer climate during this period. Comparison of the pollen and
273
diatom records with other records suggests that the ecosystem changes in the lake and the adjacent
274
region are mainly impacted by a warming and wetter climate.
275 276
Acknowledgments
277
This study was supported by the Chinese Natural Science Foundation of China (No. 41806077)
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and the Chinese National Key Research and Development Program (No.2016YFA0600500). We
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thanks two anonymous reviewers and Dr. Marian Berihuete Azorin to help us to improve the
280
manuscript.
281 282
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Xiao, X., Shen, J., Wang, S., 2011. Spatial variation of modern pollen from surface lake sediments
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northwestern Yunnan Province, southwestern China. Quaternary Science Reviews 86, 35-48.
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Xiao, X., Shen, J., Haberle, S., Han, Y., Xue, B., Zhang, E., Wang, S., Tong, G., 2015. Vegetation,
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fire, and climate history during the last 18500 cal a BP in south-western Yunnan Province, China.
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Yan, Y., Wang, L., Li, J., Li, J., Zou, Y., Zhang, J., Li, P., Liu, Y., Xu, B., Gu, Z., Wan, X., 2018.
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Diatom response to climatic warming over the last 200 years: A record from Gonghai Lake, North
377
China, Palaeogeography, Palaeoclimatology, Palaeoecology 495, 48-59.
378 379
Caption:
380
1. The location of Tingming Lake. A. The vegetation in China. B. The shape and bathymetric
381
contour of Tingming Lake.
382
2. The age model for the core. A. The variation of
383
data. C. The age-depth model using dry mass accumulation rates (DMAR).
384
3. The pollen profile and pollen spectrum.
385
4. The diatom profile and diatom spectrum.
386
5. Comparison of the selected pollen and diatom data. N-P/P= (Epiphytic+Benthic)/Planktonic.
387
6. Comparison of the regional environment with the possible impact factors. A. Global
388
temperature anomaly from 1870-2018 (relative average value from 1981-2010 AD). B. China
389
temperature anomaly from 1901-2018 (relative average value from 1981-2010 AD). C. Asian
390
temperature anomaly from 1901-2018 (relative average value from 1981-2010 AD). D. Global
391
temperature anomaly from 1850-2018 (relative average value from 1850-1900 AD). The data are
392
from the reported of Climate Change Center of China Meteorological Administration (2019).
393 394 395 396
137
Cs data. B. The variation of the total
210
Pb
A
70 o E
90 o E
80 o E
120 o E
110 o E
100 o E
130 o E
140 o E
B
45 o N
26 o 16'48"
1
2
3 2
26 o 15'22"
4 5 7
35 o N
8 9
1 2 3 4 5
25 o N
8 9
9
26 13'55" 26 o 12'29"
6
Ting Ming Lake
HZY-2
o
0
400 km
Cold-temperate coniferous forest 6 Temperate grassland 7 Conifer and deciduous mixed forest 8 Temperate deser t 9 Warm-temperate deciduous broad-leaved forest
26 o 11'02" 26 o 09'36" 99 o 31'41"E 99 o 34'34"E 99 o 37'26"E
Evergreen and deciduous broad-leaved mixed forest Alpine vegetation Subtropical evergreen broad-leaved forest Tropical seasonal rain forest and tropical rain forest
a
b
0
c
d
e
0
0
0
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5
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30
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35 200
400 600 137 Cs (Bq/kg)
800
0
1000 2000 3000 4000 5000 Total 210 Pb (Bq/kg)
35
35 0
1000 2000 3000 4000 5000 Excess 210 Pb (Bq/kg)
0.04 0.035 0.03 0.025 0.02 0.015 0.01
30
30
35
35
0
DMAR (g cm - 2 y - 1 )
1963
50
100 150 200 250 300 226 Ra (Bq/kg)
1800 1840 1880 1920 1960 2000 Year (AD)
Age (relatively 1950 yr) 20
30
40
50
60 70 80 90 100 110
Depth (cm)
-60
-40 -30 -20
-10
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20 20 20 20 20 20 20 20 20 40 20 40 60 20 20 40
qu
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ria
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ub
Terrestrial herb
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C
Сoniferous AP Fern spore
1
-50 2
3
4
5
6
II
7
8
10 9
11
12
13
14
15
16
17
I
18
19
20
21
22
20
age (relatively 1950 yr) 10
20
30
40
50
Depth (cm)
-40 -30 -20
-10
0
60 19
70 80 90 100 20
22
20 20 40 60 20 40 60 20 20
nk
ic to
th
ne
la
Zo
P
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n
Benthic
B
ch A nan ch t h A nan es ch t c h u A nan es rti ch t le ss h C nan es van ima ym t m d h C be es inu eri ym ll s ti a u ss C be m ba im ym ll ic to a a r m G be sil oce o om lla es p id h e G ph sp ica al s a om o p n G ph em om o n a G ph em gra om o n a ci E ph em pa lis un o r n a vu E otia em tac lu un m e a ke E otia xig sp i un p f ua E otia alla un m x E otia us var un s cic . gr ol oe Fr otia p a ag s va nla p i Fr la p r. n d ag ria tr ic id a Fr ila ca en ag ria pu tu la Fr ila br cin ag ria ev a i i s c sm la o t a ria ns A ll F co tru no ra n e s n C mo gila tru s c al e on on ria ens on s D ve tru ia eis eis to s v nt en Fr m p itr er s ea u a p s s p N p av N icu av la N icu ang av la u N icu sp sta ei la d N ium spp itz S sch ur i i af P on in tic n ol A ula ul a ac ria os sp ei p ra A al ul pi a ge C co na yc se lo ir te a lla va bo lid da a ni ca Ta be E lla pi py sp tic
A
Epipytic Plankton
0
-60 1
-50 2
3
4
5
6
II
7
8
10 9
11
12
13
14
15
16
17
I
18
21
40 60
Terrestrial herb
Shrub
Broadleaf AP
Coniferous AP
0
Fern spore
N-P/P
Aquatic herb
Vegetation
Planktonic
Benthic
Epipytic
Cyclotella bodanica
Aulacoseira alpigena
Lake ecosystem
1 -60 2 -50 3 -40 -30 -20
4 5
-10
7
0
8 9 10
Depth (cm)
age (relatively 1950 yr)
6
1938 AD
10 11 12 13
20
14 15
30 40 50
16 17 18
60
19
70
20
80 90 100 110 120 130
21
1845 AD
22 23
20
20
40
60
20
40
60
20
20
40
60
0.4
0.8
1.2
1.6
20
20
40
20
40
60
20
20
40
ca
na
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ge
da
pi ei
lla
ra
bo
al yc C
P P/
lo
te
os ac ul A
N-
l ea or rb ra fe ni Co
Age (yr) 2020
SST
China
Asian
Global
Age (yr) 2020
2000
2000
1980
1980
1960
1960 1938AD
1940
1940
1920
1920
1900
1900
1880
1880
1860
1845AD -0.4-0.2 0 0.20.4 -2 1840 a 0 10 20 30 40 4 8 12 16 20 24 28 10 20 30 40 50 60 0.4 0.8 1.2 1.6 2 This study
-1
0 b
1 -1.5 -1 -0.5 0 0.5 1 -0.4 0 c
1860 0.4 0.8 1.2 d
Conflict of interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The authors declare the following financial interests/personal relationships which may be considered as potential competing interests.
Sincerely,
On behalf of all authors
Bing Song
S1040-6182(19)30930-9
DOI:
https://doi.org/10.1016/j.quaint.2019.12.006
Reference:
JQI 8086
To appear in:
Quaternary International
Received Date: 29 August 2019 Revised Date:
3 December 2019
Accepted Date: 4 December 2019
Please cite this article as: Song, B., Kong, L., Hu, Z., Wang, Q., Yang, X., Pollen and diatom record of climate and environmental change over the last 170 years in Tingming Lake, Yunnan Province, SW China, Quaternary International, https://doi.org/10.1016/j.quaint.2019.12.006. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
1
Pollen and diatom record of climate and environmental change over the last 170 years in
2
Tingming Lake, Yunnan Province, SW China
3 4
Bing Song1*, Lingyang Kong1, Zhujun Hu2, Qian Wang1, Xiangdong Yang1
5 6
1 State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and
7
Limnology, Chinese Academy of Sciences, Nanjing, 210008, PR China
8
2 School of Geography Science, Nanjing Normal University, Nanjing, China
9 10 11 12 13 14 15 16 17 18 19 20 21 22
Email: Bing Song [email protected]; [email protected]
23
Abstract:
24
The south-east margin of the Qinghai-Tibet Plateau is highly sensitive to global environmental
25
changes. Even near treeline lake areas that are very minimally impacted by human activity are
26
sensitive to these global changes. In this study, we used pollen and diatom analyses to reconstruct
27
the past vegetation, ecosystem, and climate changes. The pollen record was used to indicate
28
vegetation changes and showed that the treeline and the vegetation belt have been generally
29
moving upward from 1845 AD to the present. The diatom record showed that the lake level was
30
rising along with a warming climate during this period. Comparison of the pollen and diatom
31
records with other records suggests that the ecosystem change in the lake and the adjacent region
32
are perhaps mainly impacted by the warming climate.
33 34
Keywords: Pollen, Diatom, Alpine lake, Climate change, Vegetation
35 36
1. Introduction
37
Climate is one of the most important driver of ecological and vegetation changes (Parmesan and
38
Yohe, 2003; Song et al., 2018; Yan et al., 2018). Pollen and diatom analyses of lake sediments are
39
powerful tools for assessing the effects of climate change on lake ecosystems and the nearby
40
vegetation (Xiao et al., 2015; Yan et al., 2018). Previous research using diatoms to reconstruct the
41
lake ecosystem has yielded different results. Yan et al. (2018) suggest that the lake ecosystem
42
responses to rapid climate warming and that the response of diatom biodiversity to climate is a
43
nonlinear process. However, Hu et al. (2014) suggest that catchment-mediated atmospheric
44
nitrogen deposition drives ecological change in the alpine lakes in SE Tibet. Even within the same
45
diatom species, such as the Cyclotella taxa, there are different interpretations. Some researches
46
suggest the planktonic diatom Cyclotella taxa has increased remarkably in diatom assemblages in
47
alpine, boreal, temperate, and arctic areas in response to climate warming (Gerten and Adrian,
48
2002; Perren et al., 2003; Smol et al., 2005; Enache et al., 2011; Yan et al., 2018), but some
49
paleolimnological records from several regions show a decrease in the relative trend (Perren and
50
Douglas, 2009, Perren et al., 2012; Hobbs et al., 2010; Saros et al., 2011; Yan et al., 2018).
51
Previous research has been conducted using pollen from lake to reconstruct the vegetation
52
change. Research has mainly focused on the millennium to millennium scale (e.g. Xiao et al.,
53
2012; Xiao et al., 2015; Song et al., 2018). There are very few vegetation and climate
54
reconstructions focused on the changes that have occurred during the last 200 years. There are also
55
many different interpretations for the pollen indicators, such as the increasing Pinus pollen found
56
in coastal and off shore areas that indicates fluvial water transport (Yang et al., 2016; Song et al.,
57
2017). In the general mountain area, there is a trending cold climate (Song et al., 2018). However,
58
in the alpine lake area, especially in the treeline area, the increasing Pinus pollen is exhibiting an
59
upward treeline movement (Li et al., 2019). In the same study, the use of pollen and diatom
60
analyses to reconstruct the lake ecosystem and nearby vegetation changes in the alpine lake area
61
are even scarcer.
62
In the southeast margin of the Tibetan Plateau of southwestern China, there are a large number
63
of alpine lakes. Previous studies using diatom and algal pigment inferred past environmental
64
changes, which suggested that there has been an increasing tendency of climate warming and
65
widespread nutrient loading on lakes across the region during the last two hundred years (e.g.
66
Wang et al ., 2011; Hu et al., 2014; Kong et al., 2017). However, the research about the ecosystem
67
change in the lake and the adjacent region are very scarce in the same study, which prevent our
68
understanding for the possible relationship between the ecosystem change in the lake and the
69
adjacent region.
70
In this study, we used these methods of pollen and diatom to investigate the Tingming Lake
71
ecosystem and nearby vegetation changes during the last 170 years to understand the possible
72
causes and mechanisms under the background of global climate change.
73 74
2. Geographical background and site description
75
Tingming Lake (26035’40”, 99001’30”) is an alpine lake in the western Yunnan Province on the
76
southeast edge of the Qinghai-Tibet Plateau, a transition zone from the Hengduan Mountain to the
77
Yunnan-Guizhou Plateau (Fig. 1). It lies at an altitude of 3779 m a.s.l. and is very minimally
78
impacted by human activity. The maximum depth of the lake is approximately 19.2 m. The
79
maximum length of the lake is about 0.84 km and the maximum width is 0.2 km, being about 1.5
80
km2. The drainage area is also relatively small, the main source of the sediments come from the
81
nearby mountain, and is hydrologically recharged by precipitation, surface runoff, and seasonal
82
inflows from the nearby mountain.
83
The study region is characterized by an Indian Monsoon climate that is mainly affected by the
84
warm-humid airflow from the Indian Ocean and Bengal Bay in summer and by the southern
85
branch of the westerly in winter (Xiao et al., 2014). According to the average climatic data from
86
the adjacent area, the mean annual temperature in the study area is 2.5 oC and the average annual
87
precipitation is about 910 mm (Xiao et al., 2011; Xiao et al., 2014).
88
There is an altitudinal gradient in the research area with notable vegetation belts in the alpine
89
area in Yunnan (Xiao et al., 2014). The vegetation is mid-montane humid evergreen broadleaved
90
forest from 2400-2900 m that is mainly composed of Lithocarpus craibianus, Lithocarpus
91
confertifolia, Lithocarpus hancei, and Schima argentea. From approximately 2800-3200 m, the
92
vegetation is mainly composed of Tsuga, Abies, Lithocarpus, Betula, Acer, Rhododendron, and
93
Sinarundinaria. From about 3100-3900 m, the vegetation is mainly composed of Abies and Picea.
94
The forest line is at about 3900 m. Above the forest line, the vegetation is mainly composed of
95
alpine Rhododendron shrubland, Kobresia meadow, and alpine tundra (Editorial Board of
96
Sichuan’s vegetation, 1980; Wu et al., 1987; Xiao et al., 2014). Generally, the human influence is
97
most notable below about 2500 m, where agriculture crops and limited forest cover presents
98
vegetation mainly composed of Pinus yunnanensis and Quercus (Xiao et al., 2014).
99 100
3 Materials and methods
101
3.1 Coring and sample preparation
102
The sediment core of HZY-2 (26035’35.7”, 99001’27.29”) in this study were taken from
103
Tingming Lake in 2017. The water depth was 16.1 m. It was taken using a Kajak gravity corer,
104
and sampled at 0.5 cm intervals in the field. The sediments mainly consist of darkish clay. In this
105
study, the core was drilled about 35 cm from the lake. We only analyzed the upper 22 cm, due to
106
the age data limitation.
107 108 109 110
3.2 137Cs and 210Pb dating The
137
Cs,
226
Ra, and
210
Pb dating were performed at the Nanjing Institute of Geography and
Limnology, Chinese Academy of Sciences. Each subsample was 0.5 cm thick and weighed
111
between approximately 0.4~2.2 g when freeze-dried. The weight of the samples was used to
112
calculate the dry bulk density that is defined as the dry mass per unit wet volume (Sun et al.,
113
2018).
114 115
3.3 Palynological and diatom analyses
116
The palynological analyses were performed using approximately 2 g of dried sample and one
117
tablet of Lycopodium spores (27637±563 grains per tablet). All samples were treated with 10%
118
HCl, 10% NaOH, and 2.1 g/cm3 of heavy liquid flotation. The samples were sieved using a 7 µm
119
mesh sieve and were identified under ×400 magnification using an Olympus microscope. Each
120
sample counted more than 300 grains of pollen and spores. There are not non-pollen
121
palynomorphs (algae, cyanobacteria) in the pollen slides. Approximately 0.04 g of dried sample
122
were used for the diatom analyses. All samples were treated with 10% HCl and 30% H2O2. The
123
diatom valves were counted using an Olympus microscope with an oil immersion objective
124
(magnification ×1000). Each sample contained more than 300 counted valves.
125 126
4 Results
127
4.1 Age dating and chronologies
128
In this study, the 137 Cs data with a peak at a depth of 4.75 cm, indicated at possible date of 1963
129
AD in Yunnan, China (Sun et al., 2018). Therefore, we chose the Constant Rate of Supply (CRS)
130
model to calculate the chronologies (Sun et al., 2018) (Fig. 2). The CRS model assumes that the
131
supply of
132
vary through time, because many reasons can influence the supply rate of 210Pbex in the lake, such
210
Pbex to the lacustrine sediment was constant, however, the accumulation rate could
133
as the increase of organic matters, turbidity currents caused by flood and earthquake events (Sun
134
et al., 2018). The 137Cs chronostratigraphic markers for the peak of 137Cs corresponding to the year
135
1963 can be incorporated into the CRS model as composite CRS Model to improve the final result.
136
The age data were corrected using the cumulative mass rates (g/cm2y-1) (Sun et al., 2018; Hu et al.,
137
2014).
138 139
The results showed that the lowest age data was about 1826 AD at a depth of 22.25 m and the sedimentary rates were mainly in the range of 0.1-0.5 cm/yr.
140 141
4.2 Palynology and palynological spectrum
142
The palynological data was divided into the following five groups based on their relationship
143
with the parent plant and biotope: conifer arboreal pollen (CAP), broad leaf arboreal pollen (BAP),
144
shrub(S), terrestrial Herb (TH), aquatic herb (AH), and fern spore (FS) (Fig. 3). The principal
145
pollen and spore taxa are shown in the pollen diagrams. Based on the results from the CONISS
146
analysis (Grimm, 1991, 1992) and age data, we divided the palynological spectrum into zones I
147
and II (Fig. 3)
148 149
Zone I (21.75–9.75 m, 1845–1938 AD).
150
In zone I, the proportions of CAP, BAP, S, TH, AH, and FS were approximately 12.8%, 49.6%,
151
8.6%, 29.0% 5.6%, and 12.8%, respectively (Fig. 4). Most of the CAP was from Pinus and Tsuga,
152
with average proportions of approximately 7.5% and 1.8%, respectively. The BAP was
153
predominantly from Quercus (evergreen), Quercus (deciduous), and Alnus, with average
154
proportions of about 20.8%, 10.4%, and 7.2%, respectively. Most of the S and TH were from
155
Rhododendron, Betula, Ranunculaceae, Cyperaceae, and Gramineae, with average proportions of
156
approximately 4.6%, 3.2%, 7.2%, 5.9%, and 4.2%, respectively. The AH and FS were mainly from
157
Potamogetonaceae and Polypodiaceae, with average proportion of about 4.8% and 8.8%,
158
respectively.
159 160
Zone II (9.75–0 m, 1938–2016 AD).
161
In zone II, the proportions of CAP, BAP, S, TH, AH, and FS were approximately 18.5%, 55.0%,
162
8.6%, 26.6% 3.3%, and 9.8%, respectively. The CAP mainly consisted of Pinus and Tsuga, with
163
average proportions of approximately 10.6% and 6.3%, respectively. Most of the BAP was from
164
Quercus (evergreen), Quercus (deciduous), and Alnus, with average proportions of about 19.7%,
165
8.5%, and 11.4%, respectively. The S and TH were mainly from Rhododendron, Betula,
166
Ranunculaceae, Cyperaceae, and Gramineae, with average proportions of approximately 2.7%,
167
2.9%, 2.5%, 6.7%, and 4.9%, respectively. The Potamogetonaceae and Polypodiaceae were
168
mainly part of AH and FS, with average proportion of about 2.5% and 6.1%, respectively.
169 170
4.3 Diatom and diatom spectrum
171
The diatom data was divided into three groups based on the general habitat (Torbinson and
172
Kawecka, 2005; Yan et al., 2018; Li et al., 2018), namely, epiphytic diatom (E diatom), benthic
173
diatom (B diatom), and plankton diatom (P diatom). The principle genus and species are shown in
174
Fig. 4. The diatom spectrum also references the pollen zones from the results of the CONISS
175
analysis (Grimm, 1991, 1992) and age data.
176
177
Zone I (21.75–9.75 m, 1845–1938AD)
178
In this zone, the proportions of E diatom, B diatom, and P diatom were 42.8%, 11.1% and
179
45.9%, respectively. The dominant species were Achnanthes curtissima and Achnanthes
180
Minutissima, with 4.0% and 7.1% in the E diatom group, respectively. In the B diatom group, the
181
dominant species were Diatoma sp, Navicula spp with 1.9% and 2.3%, respectively. In the P
182
diatom, group the primary species were Aulacoseira alpigena and Cyclotella bodanica with 18.9%
183
and 21.7%, respectively.
184 185
Zone II (9.75–0 m, 1938–2016AD)
186
In this zone, the proportions of E diatom, B diatom, and P diatom were 22.8%, 26.3%, and
187
50.8%, respectively. However, there were some differences compared with zone I. In the E diatom
188
group, the dominant species were Achnanthes minutissima and Gomphonema spp with 7.2% and
189
2.7%, respectively. The dominant species in the B diatom group were Diatoma sp and Navicula
190
spp, with 2.2% and 1.9%, respectively. In the P diatom group, the primary species were
191
Aulacoseira alpigena and Cyclotella bodanica, with 9.6% and 37.9%, respectively.
192 193
5 Discussion
194
5.1 Vegetation history and treeline movements in the Tingming Lake area
195
In the nearby area of Tingming Lake, the vegetation has changed from alpine forest to alpine
196
shrub, and finally to alpine meadow and tundra with increasing altitude. From 1845 AD to present,
197
the vegetation has in response to natural environmental changes without impacted by human
198
activity. There is a rice planting area in the Yunnan Province, however, it is a very scarce
199
Gramineae (>40 µm) pollen source recorded in the lake. Additionally, the proportion of CAP
200
increased, but S and TH clearly decreased. The proportion of the tree pollens of Pinus and Alnus
201
obviously increased and the shrub and TH pollen of Rhododendron and Ranunculaceae obviously
202
decreased.
203
If the treeline shifts downward to the lakeshore, the shrunken alpine forest and expanded shrub
204
meadow areas are expected to input less arboreal pollen, especially Pinus, and more shrub and
205
herbaceous pollen, such as, Rhododendron and Ranunculaceae. On the contrary, when the
206
vegetation belts move upwards with the conifer forest expanding, the lower limit of the alpine
207
shrub and meadow are expected to migrate to the upper slopes, far away from the lakeshore. In
208
that case, the shrub and herbaceous pollen would be expected to decrease with increased arboreal
209
pollen in the lake (Li et al., 2019). The vegetation change also showed that the treeline and the
210
vegetation belt generally moved upward from 1845 AD to present. The Basomtso in the Tibetan
211
Plateau also has an increased trend in the treeline recorded by increased Pinus pollen after 200 cal
212
yr BP (Li et al., 2019). Liang et al. (2011) reported a minor change in the fir tree‐line position on
213
the southeastern Tibetan Plateau after 200 years and an upward tree-line prophase rise due to
214
climate warming (Körner, 2003; Holtmeier and Broll, 2007; Harsch et al., 2009).
215 216
5.2 Ecosystem change in Tingming Lake
217
The alpine lake environment has changed since 1845 AD. The proportion of P diatoms
218
generally increased, and the B and E diatoms relatively decreases compared to the period from
219
1938–2016 AD and 1845–1938 AD (Fig. 4). This phenomenon suggests that the lake level was
220
rising (Smol and Stoermer, 2010). However, it also may be caused by increased nutrient input that
221
stimulates the phytoplankton diatoms and B diatom growth of algae. This limits the light that can
222
reach the submerged aquatic plants, inhibiting their ability to photosynthesize and causing
223
macrophyte loss (Irvine et al., 1989; Smol and Stoermer, 2010). Meanwhile, the aquatic herb (AH)
224
decrease can also arise from two different causes. However, there was a relatively high proportion
225
of Aulacoseira (Aul alpigena, Aul valida et al) in 1845–1938 AD that has generally decreased
226
since 1938 AD. In general, Aulacoseira thrives in a lake environment with increased turbulence
227
and corresponding nutrient increases during low water stages (Smol and Stoermer, 2010).
228
Therefore, the decreased proportion of Aulacoseira perhaps was caused by the rising lake level.
229
The decreased fern spores were perhaps also caused by a similar reason. Because the lake level
230
was rising, the lake size increased. The sediment cores were collected relatively far from the lake
231
shore. Thus, less ferns were transported to the drilling location. The increased percentage of
232
Cyclotella bodanica also suggests an increase in the lake level (Li et al., 2018).
233
The other diatom species were relatively stable. However, for the P diatoms, there was an
234
obvious increase in Cyclotella bodanica and a decrease in Aulacoseira alpigena (Fig. 5). The lake
235
changed from a slightly acidic, cold, and oligotrophic low lake to a relatively less acidic, warm,
236
and lower nutrient concentration lake (Brache et al., 2008; Li et al ., 2018). In the pollen diagram,
237
there was an increasing percentage of Alnus that indicated enhanced microbial nitrogen fixation in
238
the soil and indirectly impacted the lake ecosystem through an increased nutrient flux
239
(Pedziszewska et al., 2015; Li et al., 2018). In that case, there was increased flux of nutrients, but
240
there was still a relatively warm and lower nutrient concentration in the Tingming Lake. Therefore,
241
the ecosystem change in the lake was perhaps mainly caused by rising lake water levels from
242
warming and wetter climate.
243 244
5.3 Comparison of the pollen and diatom record in the ecosystem and climate change
245
The vegetation and lake ecosystem variations were both recorded by the pollen and diatoms
246
since 1845 AD. For the mountain vegetation change, there was a general changing trend, such as
247
increased Pinus, Tsuga, and Alnus, and decreased Carya, Rhododendron, and Ranunculaceae,
248
along with others (Fig. 3). The pollen spectrum indicated general climate warming. The diatom
249
record in the Tingming Lake ecosystem also displayed similar warming indicators such as the
250
increased P/N-P value, Cyclotella bodanica, and decreased Aulacoseira alpigena (Figs. 4 and 5).
251
Additionally, the general rising lake level suggests a general increase in precipitation. Therefore,
252
the climate is gradually warming and becoming wetter in the research area.
253
Comparison of the pollen and diatom records with sea surface temperatures (SST) and
254
temperatures across China, Asia, and the globe showed a very similar trend (Climate Change
255
Center of China Meteorological Administration, 2019) (Fig. 6). Perhaps the pollen and diatom
256
record in the ecosystem and climate changes mainly arose from global warming. Generally, the
257
vegetation change followed the global warming trend. However, there are several alternative
258
explanations. Some researchers suggest that catchment-mediated atmospheric nitrogen deposition
259
drives ecological change in alpine lakes in SE Tibet, such as Shade Co and Moon Lake (Hu et al.,
260
2014). Paleolimnological studies have shown that increased Nr deposition is one of the important
261
factors for environmental change (Galloway et al., 2008), especially, in alpine regions without
262
direct human distribution (Wolfe et al., 2003).
263
In this study, the pollen and diatom recorded climate changes were very similar and
264
corresponded to other records from the SST, China, Asia, and the globe. The ecosystem changes in
265
the lake and the adjacent region identified climate change as the possible culprit although the
266
diatom biodiversity response to climate was nonlinear (Yan et al., 2018).
267 268
6 Conclusion
269
In this study, the pollen and diatom record for the ecosystem of Tingming Lake and the adjacent
270
region was investigated. The pollen record for the vegetation change showed that the treeline and
271
the vegetation belt generally moved upward since 1845 AD. The diatom record indicated the lake
272
level was rising along with a warmer climate during this period. Comparison of the pollen and
273
diatom records with other records suggests that the ecosystem changes in the lake and the adjacent
274
region are mainly impacted by a warming and wetter climate.
275 276
Acknowledgments
277
This study was supported by the Chinese Natural Science Foundation of China (No. 41806077)
278
and the Chinese National Key Research and Development Program (No.2016YFA0600500). We
279
thanks two anonymous reviewers and Dr. Marian Berihuete Azorin to help us to improve the
280
manuscript.
281 282
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377
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378 379
Caption:
380
1. The location of Tingming Lake. A. The vegetation in China. B. The shape and bathymetric
381
contour of Tingming Lake.
382
2. The age model for the core. A. The variation of
383
data. C. The age-depth model using dry mass accumulation rates (DMAR).
384
3. The pollen profile and pollen spectrum.
385
4. The diatom profile and diatom spectrum.
386
5. Comparison of the selected pollen and diatom data. N-P/P= (Epiphytic+Benthic)/Planktonic.
387
6. Comparison of the regional environment with the possible impact factors. A. Global
388
temperature anomaly from 1870-2018 (relative average value from 1981-2010 AD). B. China
389
temperature anomaly from 1901-2018 (relative average value from 1981-2010 AD). C. Asian
390
temperature anomaly from 1901-2018 (relative average value from 1981-2010 AD). D. Global
391
temperature anomaly from 1850-2018 (relative average value from 1850-1900 AD). The data are
392
from the reported of Climate Change Center of China Meteorological Administration (2019).
393 394 395 396
137
Cs data. B. The variation of the total
210
Pb
A
70 o E
90 o E
80 o E
120 o E
110 o E
100 o E
130 o E
140 o E
B
45 o N
26 o 16'48"
1
2
3 2
26 o 15'22"
4 5 7
35 o N
8 9
1 2 3 4 5
25 o N
8 9
9
26 13'55" 26 o 12'29"
6
Ting Ming Lake
HZY-2
o
0
400 km
Cold-temperate coniferous forest 6 Temperate grassland 7 Conifer and deciduous mixed forest 8 Temperate deser t 9 Warm-temperate deciduous broad-leaved forest
26 o 11'02" 26 o 09'36" 99 o 31'41"E 99 o 34'34"E 99 o 37'26"E
Evergreen and deciduous broad-leaved mixed forest Alpine vegetation Subtropical evergreen broad-leaved forest Tropical seasonal rain forest and tropical rain forest
a
b
0
c
d
e
0
0
0
0
5
5
5
5
10
10
10
10
10
15
15
15
15
15
20
20
20
20
20
25
25
25
25
25
5
30
30
30
35 200
400 600 137 Cs (Bq/kg)
800
0
1000 2000 3000 4000 5000 Total 210 Pb (Bq/kg)
35
35 0
1000 2000 3000 4000 5000 Excess 210 Pb (Bq/kg)
0.04 0.035 0.03 0.025 0.02 0.015 0.01
30
30
35
35
0
DMAR (g cm - 2 y - 1 )
1963
50
100 150 200 250 300 226 Ra (Bq/kg)
1800 1840 1880 1920 1960 2000 Year (AD)
Age (relatively 1950 yr) 20
30
40
50
60 70 80 90 100 110
Depth (cm)
-60
-40 -30 -20
-10
0
10
20 20 20 20 20 20 20 20 20 40 20 40 60 20 20 40
qu
st
ria
lh
er Fe ati rn c h sp erb Zo or ne e
A
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Aquatic herb
ub
Terrestrial herb
Te r
Shrub
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S
up P res in s us a ce ae A bi es Ts + ug P a ice a E up Q hor ue b rc iac us e (e ae g) Q ue rc us C an C sta as n A tan ops ln e i us a s/ Li th Ju gl U an lm s Li us qu C ida ar m R ya ba ub r R iac ho e B do ae et d u e G la nd ra ro n G min ra e m a A in e rt e e R mi ae an si 40 un a cu C la om ce H po ae um s i C lus tae ru C cife he r a P np e ol o d y C go iac yp n e er um ae ac Th ea al e P ict ot ru Ty a m m p og M ha eto yr na P iop ce ol h ae yp yl od lum ia Tr ce ile ae t H e ic s rio P te pte C ris ris on ife ro us A P B ro ad le af A P
C
Сoniferous AP Fern spore
1
-50 2
3
4
5
6
II
7
8
10 9
11
12
13
14
15
16
17
I
18
19
20
21
22
20
age (relatively 1950 yr) 10
20
30
40
50
Depth (cm)
-40 -30 -20
-10
0
60 19
70 80 90 100 20
22
20 20 40 60 20 40 60 20 20
nk
ic to
th
ne
la
Zo
P
en
n
Benthic
B
ch A nan ch t h A nan es ch t c h u A nan es rti ch t le ss h C nan es van ima ym t m d h C be es inu eri ym ll s ti a u ss C be m ba im ym ll ic to a a r m G be sil oce o om lla es p id h e G ph sp ica al s a om o p n G ph em om o n a G ph em gra om o n a ci E ph em pa lis un o r n a vu E otia em tac lu un m e a ke E otia xig sp i un p f ua E otia alla un m x E otia us var un s cic . gr ol oe Fr otia p a ag s va nla p i Fr la p r. n d ag ria tr ic id a Fr ila ca en ag ria pu tu la Fr ila br cin ag ria ev a i i s c sm la o t a ria ns A ll F co tru no ra n e s n C mo gila tru s c al e on on ria ens on s D ve tru ia eis eis to s v nt en Fr m p itr er s ea u a p s s p N p av N icu av la N icu ang av la u N icu sp sta ei la d N ium spp itz S sch ur i i af P on in tic n ol A ula ul a ac ria os sp ei p ra A al ul pi a ge C co na yc se lo ir te a lla va bo lid da a ni ca Ta be E lla pi py sp tic
A
Epipytic Plankton
0
-60 1
-50 2
3
4
5
6
II
7
8
10 9
11
12
13
14
15
16
17
I
18
21
40 60
Terrestrial herb
Shrub
Broadleaf AP
Coniferous AP
0
Fern spore
N-P/P
Aquatic herb
Vegetation
Planktonic
Benthic
Epipytic
Cyclotella bodanica
Aulacoseira alpigena
Lake ecosystem
1 -60 2 -50 3 -40 -30 -20
4 5
-10
7
0
8 9 10
Depth (cm)
age (relatively 1950 yr)
6
1938 AD
10 11 12 13
20
14 15
30 40 50
16 17 18
60
19
70
20
80 90 100 110 120 130
21
1845 AD
22 23
20
20
40
60
20
40
60
20
20
40
60
0.4
0.8
1.2
1.6
20
20
40
20
40
60
20
20
40
ca
na
ni
ge
da
pi ei
lla
ra
bo
al yc C
P P/
lo
te
os ac ul A
N-
l ea or rb ra fe ni Co
Age (yr) 2020
SST
China
Asian
Global
Age (yr) 2020
2000
2000
1980
1980
1960
1960 1938AD
1940
1940
1920
1920
1900
1900
1880
1880
1860
1845AD -0.4-0.2 0 0.20.4 -2 1840 a 0 10 20 30 40 4 8 12 16 20 24 28 10 20 30 40 50 60 0.4 0.8 1.2 1.6 2 This study
-1
0 b
1 -1.5 -1 -0.5 0 0.5 1 -0.4 0 c
1860 0.4 0.8 1.2 d
Conflict of interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The authors declare the following financial interests/personal relationships which may be considered as potential competing interests.
Sincerely,
On behalf of all authors
Bing Song