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Link between black carbon, fires, climate change, and human activity during the Holocene period shown in the loess-paleosol sequence from Henan, China

Published online by Cambridge University Press:  07 March 2017

Yan Mu*
Affiliation:
Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
Xiaoguang Qin
Affiliation:
Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
Lei Zhang
Affiliation:
Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China University of Chinese Academy of Sciences, Beijing 100049, China
Bing Xu
Affiliation:
Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
*
*Corresponding author at: Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China. E-mail address: [email protected] (Y. Mu).

Abstract

Henan was the site of development for several ancient cultures during the Holocene. In this study, black carbon (BC) in the Holocene sediment is compared with known climatic changes and cultural events to provide information concerning the link between fire, climatic changes, and human activity in Xiangcheng. Prior to 8000 cal yr BP, the occurrence of fires was low under cold and dry climatic conditions. The BC content in 8000–1000calyrBP indicates a gradual increase in fire, with two peak values at 7500calyrBP and 3500 cal yr BP. The first peak correlates to the development of the Peiligang culture, and the second peak correlates to the development of wet and warm climate conditions along with the appearance of the Xia–Shang dynasties. Increases in fire activity could therefore be attributed to climate change and the development of human civilization in the region. Another sharp increase in fires around 1000calyrBP was consistent with a sharp increase in population during the Tang dynasty.

Type
Research Article
Copyright
Copyright © University of Washington. Published by Cambridge University Press, 2017 

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References

Ahmed, T., Dutkiewicz, V.A., Shareef, A., Tuncel, G., Tuncel, S., Husain, L., 2009. Measurement of black carbon (BC) by an optical method and a thermal-optical method: intercomparison for four sites. Atmospheric Environment 43, 63056311.CrossRefGoogle Scholar
Ali, A.A., Higuera, P.E., Bergeron, Y., Carcaillet, C., 2009. Comparing fire-history interpretations based on area, number and estimated volume of macroscopic charcoal in lake sediments. Quaternary Research 72, 462468.CrossRefGoogle Scholar
An, J., 1989. The discussion on the social features of the Longshan culture in Henan area. [In Chinese.] Cultural Relics of Central China 1, 2024.Google Scholar
An, Z.S., Kukla, G., Porter, S.C., Xiao, J.L., 1991. Late Quaternary dust flow on the Chinese Loess Plateau. Catena 18, 125132.CrossRefGoogle Scholar
Bird, M.I., Cali, J.A., 1998. A million-year record of fire in sub-Saharan Africa. Nature 394, 767769.CrossRefGoogle Scholar
Cao, J.J., Zhu, C.S., Chow, J.C., Liu, W.G., Han, Y.M., Watson, J.G., 2008. Stable carbon and oxygen isotopic composition of carbonate in fugitive dust in the Chinese Loess Plateau. Atmospheric Environment 42, 91189122.CrossRefGoogle Scholar
Carcaillet, C., 1998. A spatially precise study of Holocene fire history, climate and human impact within the Maurienne valley, North French Alps. Journal of Ecology 86, 384396.CrossRefGoogle Scholar
Carcaillet, C., Almquist, H., Asnong, H., Bradshaw, R.H.W., Carrion, J.S., Gaillard, M.J., Gajewski, K., et al., 2002. Holocene biomass burning and global dynamics of the carbon cycle. Chemosphere 49, 845863.CrossRefGoogle ScholarPubMed
Chen, F., Chen, X., Chen, J., Zhou, A., Wu, D., Tang, L., Zhang, X., Huang, X., Yu, J., 2014. Holocene vegetation history, precipitation changes and Indian Summer Monsoon evolution documented from sediments of Xingyun Lake, south-west China. Journal of Quaternary Science 29, 661674.CrossRefGoogle Scholar
Chow, J.C., Watson, J.G., Chen, L.W.A., Arnott, W.P., Moosmuller, H., Fung, K., 2004. Equivalence of elemental carbon by thermal/optical reflectance and transmittance with different temperature protocols. Environmental Science & Technology 38, 44144422.CrossRefGoogle ScholarPubMed
Chow, J.C., Watson, J.G., Pritchett, L.C., Pierson, W.R., Frazier, C.A., Purcell, R.G., 1993. The DRI thermal/optical reflectance carbon analysis system: description, evaluation and applications in U.S. air quality studies. Atmospheric Environment, Part A: General Topics 27, 11851201.CrossRefGoogle Scholar
Clark, J.S., 1988. Stratigraphic charcoal analysis on petrographic thin-sections: application to fire history in northwestern Minnesota. Quaternary Research 30, 8191.CrossRefGoogle Scholar
Daniau, A.L., Bartlein, P.J., Harrison, S.P., Prentice, I.C., Brewer, S., Friedlingstein, P., Harrison-Prentice, T.I., et al., 2012. Predictability of biomass burning in response to climate changes. Global Biogeochemical Cycles 26, GB4007. http://dx.doi.org/10.1029/2011GB004249.CrossRefGoogle Scholar
Daniau, A.L., Harrison, S.P., Bartlein, P.J., 2010. Fire regimes during the Last Glacial. Quaternary Science Reviews 29, 29182930.CrossRefGoogle Scholar
Dennison, P.E., Moritz, M.A., Taylor, R.S., 2008. Evaluating predictive models of critical live fuel moisture in the Santa Monica Mountains, California. International Journal of Wildland Fire 17, 1827.CrossRefGoogle Scholar
Dickens, A.F., Gélinas, Y., Masiello, C.A., Wakeham, S., Hedges, M.M., 2004. Reburial of fossil organic carbon in marine sediments. Nature 427, 336339.CrossRefGoogle ScholarPubMed
Ding, Z.L., Yu, Z.W., Yang, S.L., Sun, J.M., Xiong, S.F., Liu, T.S., 2001. Coeval changes in grain size and sedimentation rate of eolian loess, the Chinese Loess Plateau. Geophysical Research Letters 28, 20972100.CrossRefGoogle Scholar
Dykoski, C.A., Edwards, R.L., Cheng, H., Yuan, D.X., Cai, Y.J., Zhang, M.L., Lin, Y.S., Qing, J.M., 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, 7186.CrossRefGoogle Scholar
Elmquist, M., Gustafsson, Ö., Andersson, P., 2004. Quantification of sedimentary black carbon using the chemothermal oxidation method: an evaluation of ex situ pretreatments and standard additions approaches. Limnology and Oceanography: Methods 2, 417427.Google Scholar
Fowler, C., Konopik, E., 2007. The history of fire in the southern United States. Human Ecology Review 14, 165176.Google Scholar
Fried, J.S., Torn, M.S., Mills, E., 2004. The impact of climate change on wildfire severity: a regional forecast for northern California. Climatic Change 64, 169191.CrossRefGoogle Scholar
Gasse, F., Arnold, M., Fontes, J.C., Fort, M., Gibert, E., Huc, A., Li, B., et al., 1991. A 13000-year climate record from western Tibet. Nature 353, 742745.CrossRefGoogle Scholar
Gelinas, Y., Prentice, K.M., Baldock, J.A., Hedges, J.I., 2001. An improved thermal oxidation method for the quantification of soot/graphitic black carbon in sediments and soils. Environmental Science & Technology 35, 35193525.CrossRefGoogle ScholarPubMed
Griffin, J.J., Goldberg, E.D., 1983. Impact of fossil-fuel combustion on sediments of Lake Michigan: a reprise. Environmental Science & Technology 17, 244245.CrossRefGoogle Scholar
Han, Y.N., Cao, J.J., An, Z.S., Chow, J.C., Watson, J.G., Jin, Z., Fung, K., Liu, S.X., 2007a. Evaluation of the thermal/optical reflectance method for quantification of elemental carbon in sediments. Chemosphere 69, 526533.CrossRefGoogle ScholarPubMed
Han, Y.M., Cao, J.J., Chow, J.C., Watson, J.G., An, Z.S., Jin, Z.D., Fung, K.C., Liu, S.X., 2007b. Evaluation of the thermal/optical reflectance method for discrimination between char- and soot-EC. Chemosphere 69, 569574.CrossRefGoogle ScholarPubMed
Han, Y.M., Cao, J.J., Chow, J.C., Watson, J.G., An, Z.S., Liu, S.X., 2009a. Elemental carbon in urban soils and road dusts in Xi’an, China and its implication for air pollution. Atmospheric Environment 43, 24642470.CrossRefGoogle Scholar
Han, Y.M., Cao, J.J., Posmentier, E.S., Chow, J.C., Watson, J.G., Fung, K.K., Jin, Z.D., Liu, S.X., An, Z.S., 2009b. The effect of acidification on the determination of elemental carbon, char-, and soot-elemental carbon in soils and sediments. Chemosphere 75, 9299.CrossRefGoogle ScholarPubMed
Han, Y.M., Han, Z.W., Cao, J.J., Chow, J.C., Watson, J.G., An, Z.S., Liu, S.X., Zhang, R.J., 2008. Distribution and origin of carbonaceous aerosol over a rural high-mountain lake area, northern China and its transport significance. Atmospheric Environment 42, 24052414.CrossRefGoogle Scholar
Han, Y.M., Marlon, J.R., Cao, J.J., Jin, Z.D., An, Z.S., 2012. Holocene linkages between char, soot, biomass burning and climate from Lake Daihai, China. Global Biogeochemical Cycles 26, GB4017. http://dx.doi.org/10.1029/2011GB004197.CrossRefGoogle Scholar
Hansen, A.D.A., Kapustin, V.N., Kopeikin, V.M., Gillette, D.A., Bodhaine, B.A., 1993. Optical absorption by aerosol black carbon and dust in desert region of Central Asia, Atmospheric Environment. Part A: General Topics 27, 25272531.Google Scholar
Huang, C.C., Pang, J.L., 2002. Abruptly increased climatic aridity and its social impact on the Loess Plateau of China at 3100 a B.P. Journal of Arid Environments 52, 8799.CrossRefGoogle Scholar
Huang, C.C., Pang, J.L., Chen, S.E., Su, H.X., Han, J., Cao, Y.F., Zhao, W.Y., Tan, Z.H., 2006. Charcoal records of fire history in the Holocene loess–soil sequences over the southern Loess Plateau of China. Palaeogeography, Palaeoclimatology, Palaeoecology 239, 2844.CrossRefGoogle Scholar
Hsieh, Y.P., Bugna, G.C., 2008. Analysis of black carbon in sediments and soils using multi-element scanning thermal analysis (MESTA). Organic Geochemistry 39, 15621571.CrossRefGoogle Scholar
Jacobson, M.Z., 2001. Strong radiative heating due to the mixing state of black carbon in atmospheric aerosols. Nature 409, 695697.CrossRefGoogle Scholar
Kim, S.K., Kaplan, L.A., Benner, R., Hatcher, P.G., 2004. Hydrogen deficient molecules in natural riverine water samples—evidence for existence for black carmbon in DOM. Marine Chemistry 92, 225234.CrossRefGoogle Scholar
Kuhlbusch, T.A.J., Crutzen, P.J., 1995. Toward a global estimate of black carbon in residues of vegetation fires representing a sink of atmospheric CO2 and a source of O2. Global Biogeochemical Cycles 9, 491501.CrossRefGoogle Scholar
Lim, B., Cachier, H., 1996. Determination of black carbon by chemical oxidation and thermal treatment in recent marine and lake sediments and Cretaceous-Tertiary clays. Chemical Geology 131, 143154.CrossRefGoogle Scholar
Liu, Z., Wen, X., Brady, E.C., Otto-Bliesner, B., Yu, G., Lu, H.Y., Cheng, H., et al., 2014. Chinese cave records and the East Asia Summer Monsoon. Quaternary Science Reviews 83, 115128.CrossRefGoogle Scholar
Long, C.J., Whitlock, C., Bartlein, P.J., Millspaugh, S.H., 1998. A 9000-year fire history from the Oregon Coast Range, based on a high-resolution charcoal study. Canadian Journal of Forest Research 28, 774787.CrossRefGoogle Scholar
Lu, H., Zhang, J., 2008. Neolithic cultural evolution and Holocene climate change in the Guanzhong basin, Shaanxi, China. [In Chinese.] Quaternary Sciences 28, 10501060.Google Scholar
Lu, W., Wu, B., 1999. Relationship between the paleoculture and paleoclimate in middle of China in Neolithic age. [In Chinese.] Scientia Geographica Sinica 19, 6972.Google Scholar
Mao, W.S., Wang, Q.Q., Ge, X.M., Jing, Y., Du, Y.C., Cao, Y.Y., 2006. Analysis of Meiyu characteristics and general circulation over the Changjiang-Huaihe River valley in Recent 116 years. Meteorological Monthly 6, 8490.Google Scholar
Mao, W.S., Wang, Q.Q., Ma, H., Shen, G.F., 2008. Temporal evolution and spatial distribution characteristics of Meiyu in Changjiang-Huaihe valley. Journal of Nanjing Institute of Meteorlog 31, 116122 (in Chinese).Google Scholar
Marlon, J.R., Bartlein, P.J., Daniau, A.L., Harrison, S.P., Maezumi, S.Y., Power, M.J., Tinner, W., Vanniere, B., 2013. Global biomass burning: a synthesis and review of Holocene paleofire records and their controls. Quaternary Science Reviews 65, 525.CrossRefGoogle Scholar
Marlon, J.R., Bartlein, P.J., Walsh, M.K., Harrison, S.P., Brown, K.J., Edwards, M.E., Higuera, P.E., et al., 2009. Wildfire responses to abrupt climate change in North America. Proceedings of the National Academy of Sciences of the United States of America 106, 25192524.CrossRefGoogle ScholarPubMed
Marlon, J., Bartlein, P.J., Whitlock, C., 2006. Fire-fuel-climate linkages in the northwestern USA during the Holocene. Holocene 16, 10591071.CrossRefGoogle Scholar
Masiello, C.A., Druffel, E.R.M., 1998. Black carbon in deep-sea sediments. Science 280, 19111913.CrossRefGoogle ScholarPubMed
Menon, S., Hansen, J., Nazarenko, L., Luo, Y.F., 2002. Climate effects of black carbon aerosols in China and India. Science 297, 22502253.CrossRefGoogle ScholarPubMed
Mooney, S.D., Harrison, S.P., Bartlein, P.J., Daniau, A.L., Stevenson, J., Brownlie, K.C., Buckman, S., et al., 2011. Late Quaternary fire regimes of Australasia. Quaternary Science Reviews 30, 2846.CrossRefGoogle Scholar
Mu, Y., Qin, X.G., Zhang, L., Xu, B., 2014. A preliminary study of Holocene climate change and human adaptation in the Horqin region. Acta Geologica Sinica (English Edition) 88, 17841791.CrossRefGoogle Scholar
Mu, Y., Qin, X.G., Zhang, L., Xu, B., 2016. Holocene climate change evidence from high-resolution loess/paleosol records and the linkage to fire–climate change–human activities in the Horqin dunefield in northern China. Journal of Asian Earth Sciences 121, 18.CrossRefGoogle Scholar
Muri, G., Cermelj, B., Faganeli, J., Brancelj, A., 2002. Black carbon in Slovenian alpine lacustrine sediments. Chemosphere 46, 12251234.CrossRefGoogle ScholarPubMed
Ohlson, M., Dahlberg, B., Okland, T., Brown, K.J., Halvorsen, R., 2009. The charcoal carbon pool in boreal forest soils. Nature Geoscience 2, 692695.CrossRefGoogle Scholar
Pinter, N., Fiedel, S., Keeley, J.E., 2011. Fire and vegetation shifts in the Americas at the vanguard of Paleoindian migration. Quaternary Science Reviews 30, 269272.CrossRefGoogle Scholar
Poot, A., Quik, J.T.K., Veld, H., Koelmans, A.A., 2009. Quantification methods of Black Carbon: comparison of Rock-Eval analysis with traditional methods. Journal of Chromatography A 1216, 613622.CrossRefGoogle ScholarPubMed
Preston, C.M., Schmidt, M.W.I., 2006. Black (pyrogenic) carbon: a synthesis of current knowledge and uncertainties with special consideration of boreal regions. Biogeosciences 3, 397420.CrossRefGoogle Scholar
Pyne, S.J., Andrews, P.L., Laven, R.D., 1996. Introduction to Wildland Fire. John Wiley and Sons, New York.Google Scholar
Qin, S.G., Tang, J., Wen, Y.P., 2001. Black carbon and its importance in climate change studies. Meteorology 27, 37.Google Scholar
Qin, X., Zhang, L., Mu, Y., 2015. The Holocene climatic changes of the Huaihe River semi-humid region in the north and south transition zone of the eastern China. Quaternary Sciences 35, 15091524.Google Scholar
Ramanathan, V., Carmichael, G., 2008. Global and regional climate changes due to black carbon. Nature Geoscience 4, 221227.CrossRefGoogle Scholar
Randerson, J.T., Liu, H., Flanner, M.G., Chambers, S.D., Jin, Y., Hess, P.G., Pfister, G., et al., 2006. The impact of boreal forest fire on climate warming. Science 314, 11301132.CrossRefGoogle ScholarPubMed
Ruddiman, W.F., 2003. The anthropogenic greenhouse era began thousands of years ago. Climatic Change 61, 261293.CrossRefGoogle Scholar
Ruddiman, W.F., 2007. The early anthropogenic hypothesis: challenges and responses. Reviews of Geophysics 45, RG4001. http://dx.doi.org/10.1029/2006RG000207.CrossRefGoogle Scholar
Schmidt, M.W.I., Noack, A.G., 2000. Black carbon in soils and sediments: analysis, distribution, implications, and current challenges. Global Biogeochemical Cycles 14, 777793.CrossRefGoogle Scholar
Simpson, J.M., Hatcher, G.P., 2004. Overestimates of black carbon in soils and sediments. Naturwissenschaften 91, 436440.CrossRefGoogle ScholarPubMed
Sun, X.S., Peng, P.A., Song, J.Z., Zhiang, G., Hu, J.F., 2008. Sedimentary record of black carbon in the Pearl River estuary and adjacent northern South China Sea. Geochemistry 23, 24643472.Google Scholar
Tan, M., 2014. Circulation effect: response of precipitation delta O-18 to the ENSO cycle in monsoon regions of China. Climate Dynamics 42, 10671077.CrossRefGoogle Scholar
Tan, Z.H., Han, Y.M., Cao, J.J., Huang, C.C., An, Z.S., 2015. Holocene wildfire history and human activity from high-resolution charcoal and elemental black carbon records in the Guanzhong basin of the Loess Plateau, China. Quaternary Science Reviews 109, 7687.CrossRefGoogle Scholar
van der Kaars, S., Wang, X., Kershaw, P., Guichard, F., Setiabudi, D.A., 2000. A Late Quaternary palaeoecological record from the Banda Sea, Indonesia: patterns of vegetation, climate and biomass burning in Indonesia and northern Australia. Palaeogeography, Palaeoclimatology, Palaeoecology 155, 135153.CrossRefGoogle Scholar
Verardo, D.J., Ruddiman, W.F., 1996. Late Pleistocene charcoal in tropical Atlantic deep-sea sediments: climatic and geochemical signiflcance. Geology 24, 855857.2.3.CO;2>CrossRefGoogle Scholar
Vinther, B.M., Clausen, H.B., Johnsen, S.J., Rasmussen, S.O., Andersen, K.K., Buchardt, S.L., Dahl-Jense, D., et al., 2006. A synchronized dating of three Greenland ice cores throughout the Holocene. Journal of Geophysical Research 111, D13102. http://dx.doi.org/10.1029/2005JD006921.CrossRefGoogle Scholar
Wang, X., Ding, Z.L., Peng, P.A., 2012. Changes in fire regimes on the Chinese Loess Plateau since the last glacial maximum and implications for linkages to paleoclimate and past human activity. Palaeogeography, Palaeoclimatology, Palaeoecology 315, 6174.CrossRefGoogle Scholar
Wang, X., Peng, P.A., Ding, Z.L., 2005. Black carbon records in Chinese Loess Plateau over the last two glacial cycles and implications for paleofires. Palaeogeography, Palaeoclimatology, Palaeoecology 223, 919.CrossRefGoogle Scholar
Wang, X., Xiao, J.L., Cui, L.L., Ding, Z.L., 2013. Holocene changes in fire frequency in the Daihai Lake region (north-central China): indications and implications for an important role of human activity. Quaternary Science Reviews 59, 1829.CrossRefGoogle Scholar
Wang, Z., 2007. History of Sui Tang and Five Dynasties. Zhonghua Book Company, Beijing.Google Scholar
Wei, X., 2012. Archaeological discoveries and studies of the Neolithic age in Henan since the founding of New China. [In Chinese.] Huaxia Archaeology 2, 2548.Google Scholar
Whitlock, C., Bartlein, P.J., 2003. Holocene fire activity as a record of past environmental change. In: Gillespie, A., Porter, S.C. (Eds.), Developments in Quaternary Science. Vol. 1. Elsevier, Amsterdam, pp. 479490.Google Scholar
Whitlock, C., Moreno, P.I., Bartlein, P., 2007. Climatic controls of Holocene fire patterns in southern South America. Quaternary Research 68, 2836.CrossRefGoogle Scholar
Wolbach, W.S., Anders, E., 1989. Elemental carbon in sediments: determination and isotopic analysis in the presence of kerogen. Geochimica et Cosmochimica Acta 53, 16371647.CrossRefGoogle Scholar
Xu, J., Mo, D., Wang, H., Zhou, K., 2013. Preliminary research of environment archaeology in Zhenshui River, Xinmi City, Henan. [In Chinese.] Quaternary Sciences 33, 954964.Google Scholar
Xu, M., Tian, H., 2005. The relationship between the atmosphere vapor transportation and rainfall over Huaihe River basin during the Meiyu period in 2003. Scientia Meteorological Sinica 25, 265271.Google Scholar
Yang, Y., Shen, C.D., Yi, W.X., Sun, Y.M., Liu, D.S., Liu, T.S., 2001. The elemental carbon record in Weinan loess section since the last 21 ka. Chinese Science Bulletin 46, 15411544.CrossRefGoogle Scholar
Yang, Y., Sun, G., 2002. The Xu discussion on the status of the Central Plains civilization in the Chinese ancient civilization from the archaeological discovery. [In Chinese.] Cultural Relics of Central China 6, 3342.Google Scholar
Zaady, E., Offcer, Z.Y., Shachak, M., 2001. The content and contributions of deposited eolian organic matter in a dry land ecosystem of the Negev Desert, Israel. Atmospheric Environment 35, 769776.CrossRefGoogle Scholar
Zhang, E.L., Sun, W.W., Zhao, C., Wang, Y.B., Xue, B., Shen, J., 2015. Linkages between climate, fire and vegetation in southwest China during the last 18.5 ka based on a sedimentary record of black carbon and its isotopic composition. Palaeogeography, Palaeoclimatology, Palaeoecology 435, 8694.CrossRefGoogle Scholar
Zhang, J.H., Kong, Z.C., Du, N.Q., 1997. Charocoal analysis and fire changes at Dongganchi of Fangshan in Beijing since 15000 a B.P. Acta Pytoecologica Sinica 21, 161168 (in Chinese).Google Scholar
Zheng, A.Q., Su, Y.X., Zhao, J.D., 2007. Review on black carbon aerosol. Energy Environmental Protection 21, 49.Google Scholar
Zhou, B., Shen, C.D., Sun, W.D., Zheng, H.B., Yang, Y., Sun, Y.B., An, Z.S., 2007. Elemental carbon record of paleofire history on the Chinese Loess Plateau during the last 420 ka and its response to environmental and climate changes. Palaeogeography, Palaeoclimatology, Palaeoecology 252, 617625.CrossRefGoogle Scholar
Zhou, W.J., Donahue, D., Porter, S.C., et al., 1996. Variability of monsoon climate in East Asia at the end of the last glaciation. Quaternary Research 46, 219229.Google Scholar