The total organic carbon (TOC) content series from the lake sediment of Minqin Basin (100°57′–104°57′E, 37°48′–39°17′N) in northwestern China, which has a 10 000-year-long paleo-climatic prox...The total organic carbon (TOC) content series from the lake sediment of Minqin Basin (100°57′–104°57′E, 37°48′–39°17′N) in northwestern China, which has a 10 000-year-long paleo-climatic proxy record, was used to analyze the Holocene climate changes in the local region. The proxy record was established in the Sanjiaocheng (SJC), Triangle Town in Chinese, Section (103°20′25″E, 39°00′38″N), which is located at the northwestern boundary of the present Asian summer monsoon in China, and is sensitive to global environmental and climate changes. Applying singular spectrum analysis (SSA) to the TOC series, principal climatic oscillations and periodical changes were studied. The results reveal 3 major patterns of climate change regulated by reconstructed components (RCs). The first pattern is natural long-term trend of climatic change in the local area (Minqin Basin), indicating a relatively wetter stage in early Holocene (starting at 9.5 kaBP), and a relatively dryer stage with a strong lake desiccation and a declined vegetation cover in mid-Holocene (during 7–6 kaBP). From 4.0 kaBP to the present, there has been a gradually decreasing trend in the third reconstructed component (RC3) showing that the local climate changed again into a dryer stage. The second pattern shows millennial-centennial scale oscillations containing cycles of 1 600 and 800 years that have been present throughout almost the entire Holocene period of the last 10 000 years. The third pattern is a millennial-centennial scale variation with a relatively smaller amplitude and unclear cycles showing a nonlinear interaction within the earth’s climate systems.展开更多
Proxy-based reconstructions and climate model simulations of Holocene global annual mean temperatures exhibit divergent trends,leading to the well-known“Holocene temperature conundrum(HTC)”.This discrepancy is most ...Proxy-based reconstructions and climate model simulations of Holocene global annual mean temperatures exhibit divergent trends,leading to the well-known“Holocene temperature conundrum(HTC)”.This discrepancy is most pronounced in the mid-to-high latitudes of the Northern Hemisphere(NH)and has been attributed to either proxy seasonal bias or deficiencies in climate models.Paleoclimate data assimilation(PDA),which integrates proxy records with climate model simulations,provides an advanced method for generating global seasonal temperature reanalysis datasets for the mid-Holocene(MH).Assimilated results indicate that MH Eurasian temperatures are largely independent of the choice of model priors and exhibit significant spatial heterogeneity.Compared to the pre-industrial(PI)period,the MH is characterized by winter and annual mean warming in Europe and high-latitude Eurasia,while the rest of Eurasia experiences cooling.However,this spatial heterogeneity is not well represented in model simulations due to a pronounced winter cooling bias at high latitudes,likely resulting from inadequate representations of vegetation and sea ice feedback mechanisms.As Eurasian proxy records are predominantly concentrated in Europe,this regional imbalance introduces a warm bias in reconstructed winter and annual temperatures intended to represent broader Eurasian temperature changes.These results suggest that the HTC may stem from both the uneven spatial distribution of proxy records and the incomplete representation of internal climate feedbacks in current models.展开更多
The reconstruction of global annual mean temperatures made by the PAGES 2k Consortium in 2019 represents one of the most influential sequences of global climate variability over the Common Era.However,it is still not ...The reconstruction of global annual mean temperatures made by the PAGES 2k Consortium in 2019 represents one of the most influential sequences of global climate variability over the Common Era.However,it is still not clear how the reconstruction can be influenced by the selection of reconstruction methods and the selection of proxy records with different temporal resolutions over different regions.We adopt a widely used Composite-Plus-Scale method to elucidate the effects of the selection of the proxy records on temperature reconstruction.To ensure the uniformity of data,different types of proxy records spanning the past~2000 years from the PAGES 2k proxy network were used to investigate the potential effects of proxy selection in hemispheric and global temperature reconstructions during the past two millennia.The long-term trends,spectral characteristics,and volcanic responses of the annual temperatures were studied based on the reconstructions.Our results reveal a significant cooling trend in the global annual mean temperature using both tree-ring and non-tree-ring records during the 1–1850CE period,and show that the cooling exhibits a stronger trend in the Southern Hemisphere(SH)than that in the Northern Hemisphere(NH).Yet,the long-term trends vary according to different combinations of proxy records.Different reconstructions based on different types of proxies also exhibit different features in terms of volcanic responses and spectral properties.Tree-ring-based temperature reconstructions show stronger cooling responses to tropical volcanic eruptions,while non-tree-ring-based reconstructions suggest less robust volcanic responses,which may be related to dating uncertainties and low temporal resolution of the proxies.Tree-ring width records tend to preserve a substantial proportion of high-frequency(<200 years)variability,whereas non-tree-ring proxies tend to capture a larger fraction of low-frequency(>200 years)variations.Efforts are needed to reduce uncertainties of the temperature reconstruction over the Common Era associated with the insufficient spatiotemporal coverage of the current proxy network,especially for the first millennium and for the SH and tropics,also to develop statistical methods and to improve the signal strength and constrain uncertainties in existing proxy records.展开更多
Microscopic charcoal preserved in sediments of the Lashly Formation(Middle to Late Triassic)of South Victoria Land(SVL),Antarctica provides a proxy record of palaeofire.These charred fragments derived from wood and le...Microscopic charcoal preserved in sediments of the Lashly Formation(Middle to Late Triassic)of South Victoria Land(SVL),Antarctica provides a proxy record of palaeofire.These charred fragments derived from wood and leaf pieces along with spores and pollen grains are part of the buried plant biomass preserved in the shale and carbonaceous shale of fluvial/lacustrine deposits.The evidence of paleofire in Antarctica during the Triassic Period is supported by the presence of a thin bed of silicic tuff interlayered with Dicroidiumbearing shale.The detailed morphology and comparative anatomy of least to high thermally altered plant fragments observed under the light,fluorescence and scanning electron microscope demonstrates the evidence of effect of fire on the vegetation during Middle to Late Triassic(240-200 million years).Most of the charred particles retain identifiable structures with well-preserved to distorted cellular details.Such plant fragments are dark brown,blackish brown,quadrangular-multiangular,equi-dimensional,opaque up to the edges and nonfluorescent.The pollen grains recorded from several sedimentary sequences(but the new data come from only one level i.e.,member C of Lashly Formation)show distorted exinal sculptures and are light to dark brown in colour indicating intensive thermal effect.The detailed microscopic images of such fire-affected plant remains also explain their preservation biases in the sediments.The magnitude of the charred pieces and their abundance peaks from various locations in Allan Hills is related solely to the production and amount of burnt material embodied in the sediments.The high peaks indicate severity of fire and production of maximum charcoal of the standing vegetation in Allan Hills.展开更多
An overview of basic research on climate change in recent years in China is presented. In the past 100 years in China, average annual mean surface air temperature （SAT） has increased at a rate ranging from 0.03℃ （...An overview of basic research on climate change in recent years in China is presented. In the past 100 years in China, average annual mean surface air temperature （SAT） has increased at a rate ranging from 0.03℃ （10 yr）-1 to 0.12℃ （10 yr）-1. This warming is more evident in northern China and is more significant in winter and spring. In the past 50 years in China, at least 27% of the average annual warming has been caused by urbanization. Overall, no significant trends have been detected in annual and/or summer precipitation in China on a whole for the past 100 years or 50 years. Both increases and decreases in frequencies of major extreme climate events have been observed for the past 50 years. The frequencies of extreme temperature events have generally displayed a consistent pattern of change across the country, while the frequencies of extreme precipitation events have shown only regionally and seasonally significant trends. The frequency of tropical cyclone landfall decreased slightly, but the frequency of sand/dust storms decreased significantly. Proxy records indicate that the annual mean SAT in the past a few decades is the highest in the past 400-500 years in China, but it may not have exceeded the highest level of the Medieval Warm Period （1000 1300 AD）. Proxy records also indicate that droughts and floods in eastern China have been characterized by continuously abnormal rainfall periods, with the frequencies of extreme droughts and floods in the 20th century most likely being near the average levels of the past 2000 years. The attribution studies suggest that increasing greenhouse gas （GHG） concentrations in the atmosphere are likely to be a main factor for the observed surface warming nationwide. The Yangtze River and Huaihe River basins underwent a cooling trend in summer over the past 50 years, which might have been caused by increased aerosol concentrations and cloud cover. However, natural climate variability might have been a main driver for the mean and extreme precipitation variations observed over the past century. Climate models generally perform well in simulating the variations of annual mean SAT in China. They have also been used to project future changes in SAT under varied GHG emission scenarios. Large uncertainties have remained in these model-based projections, however, especially for the projected trends of regional precipitation and extreme climate events.展开更多
Whether the Atlantic Meridional Overturning Circulation(AMOC),one of the most vital tipping elements in the Earth’s cli-mate system with far-reaching effects on interhemispheric heat distributions,the carbon cycles,a...Whether the Atlantic Meridional Overturning Circulation(AMOC),one of the most vital tipping elements in the Earth’s cli-mate system with far-reaching effects on interhemispheric heat distributions,the carbon cycles,and a cascade series of hydrocli-matic changes worldwide,is approaching a tipping point has become an increasingly urgent concern[1-4].Climate proxy records arguably suggest that the AMOC is currently at its weakest state over the last millennium,with a marked AMOC weakening trend evident between 1870 and 2020 C.E.[3].A recent physics-based analysis of early warning signals even suggests that an AMOC collapse could occur as early as one year from 2024 C.E.[2].Nevertheless,the IPCC AR6,based on simulations from the Cli-mate Model Intercomparison Project(CMIP),quotes that an AMOC collapse in the 21st century is unlikely(Fig.S1 online)[2].This data-model discrepancy suggests unaccounted-for factors have been influencing AMOC[1].While the AMOC collapse would pose severe cascading impacts on global climate disruption,consider-able uncertainty remains regarding whether and when such an AMOC collapse is coming[2,4,5].One approach to address this challenge lies in a precise comparison of the ongoing AMOC weak-ening with their analogous episodes preserved in paleoclimate records-putting the AMOC weakening into context with a series of presumable AMOC collapse scenarios inferred from Greenland ice core oxygen isotope(d18 O,mainly a proxy of Greenland tem-perature)records[6-8](Fig.S2b online).展开更多
The Holocene epoch spans the interval from~11,700 years ago to the present.During this period,the overall change in global average annual insolation was minimal(~0.01 W m-2),though it was marked by significant regiona...The Holocene epoch spans the interval from~11,700 years ago to the present.During this period,the overall change in global average annual insolation was minimal(~0.01 W m-2),though it was marked by significant regional and seasonal variability.At the same time,atmospheric greenhouse gas concentrations have steadily increased since the mid-Holocene(MH)(~0.46 W m^(-2)).A comprehensive understanding of the evolution of Holocene temperatures in China is crucial for contextualizing current global warming within historical climate periods,and for unraveling the patterns of human-environment interactions over time.Early studies,primarily based on the integration of proxy records,suggested that temperatures in China during the early to mid-Holocene were higher than those of the pre-industrial(Pl)period,giving rise to the widely accepted concept of the"Holocene Thermal Maximum"(HTM)[1].展开更多
We present the major results from studies of fire history over the last 11000 years(Holocene) in southern Sweden, on the basis of palaeoecological analyses of peat sequences from three small peat bogs. The main object...We present the major results from studies of fire history over the last 11000 years(Holocene) in southern Sweden, on the basis of palaeoecological analyses of peat sequences from three small peat bogs. The main objective is to emphasize the value of multiple, continuous sedimentary records of macroscopic charcoal(macro-C) for the reconstruction of local to regional past changes in fire regimes, the importance of multi-proxy studies, and the advantage of model-based estimates of plant cover from pollen data to assess the role of tree composition and human impact in fire history. The chronologies at the three study sites are based on a large number of 14 C dates from terrestrial plant remains and age-depth models are achieved using Bayesian statistics. Fire history is inferred from continuous records of macro-C and microscopic charcoal counts on pollen slides. The Landscape Reconstruction Algorithm(LRA) for pollen-based quantitative reconstruction of local vegetation cover is applied on the three pollen records for plant cover reconstruction over the entire Holocene. The results are as follows:(1) the long-term trends in fire regimes are similar between sites, i.e., frequent fires during the early Holocene until ca. 9 ka BP, low fire frequency during the mid-Holocene, and higher fire frequency from ca. 2.5 ka BP;(2) this broad trend agrees with the overall fire history of northwestern and western Europe north of the Mediterranean area, and is due to climate forcing in the early and mid-Holocene, and to anthropogenic land-use in the late Holocene;(3) the LRA estimates of plant cover at the three sites demonstrate that the relative abundance of pine played a primordial role in the early and mid-Holocene fire history; and(4) the between-site differences in the charcoal records and inferred fire history are due to local factors(i.e., relative abundance of pine, geomorphological setting, and anthropogenic land-use) and taphonomy of charcoal deposition in the small peat bogs. It is shown that continuous macro-C records are most useful to disentangle local from regional-subcontinental fire history, and climate-induced from human-induced fire regimes, and that pollen-based LRA estimates of local plant cover are more adequate than pollen percentages for the assessment of the role of plant composition on fire history.展开更多
基金the National Natural Science Foundation of China (NSFC) (No. 40571169)the NSFC’s Innovation Team Project (No. 40421101), and the NSFC’s Key Program Project (No. 90502008)
文摘The total organic carbon (TOC) content series from the lake sediment of Minqin Basin (100°57′–104°57′E, 37°48′–39°17′N) in northwestern China, which has a 10 000-year-long paleo-climatic proxy record, was used to analyze the Holocene climate changes in the local region. The proxy record was established in the Sanjiaocheng (SJC), Triangle Town in Chinese, Section (103°20′25″E, 39°00′38″N), which is located at the northwestern boundary of the present Asian summer monsoon in China, and is sensitive to global environmental and climate changes. Applying singular spectrum analysis (SSA) to the TOC series, principal climatic oscillations and periodical changes were studied. The results reveal 3 major patterns of climate change regulated by reconstructed components (RCs). The first pattern is natural long-term trend of climatic change in the local area (Minqin Basin), indicating a relatively wetter stage in early Holocene (starting at 9.5 kaBP), and a relatively dryer stage with a strong lake desiccation and a declined vegetation cover in mid-Holocene (during 7–6 kaBP). From 4.0 kaBP to the present, there has been a gradually decreasing trend in the third reconstructed component (RC3) showing that the local climate changed again into a dryer stage. The second pattern shows millennial-centennial scale oscillations containing cycles of 1 600 and 800 years that have been present throughout almost the entire Holocene period of the last 10 000 years. The third pattern is a millennial-centennial scale variation with a relatively smaller amplitude and unclear cycles showing a nonlinear interaction within the earth’s climate systems.
基金supported by the Basic Science Center for Tibetan Plateau Earth System(BSCTPES,41988101)the National Key Research and Development Program of China(2023YFF0805200)the National Natural Science Foundation of China(42101148)。
文摘Proxy-based reconstructions and climate model simulations of Holocene global annual mean temperatures exhibit divergent trends,leading to the well-known“Holocene temperature conundrum(HTC)”.This discrepancy is most pronounced in the mid-to-high latitudes of the Northern Hemisphere(NH)and has been attributed to either proxy seasonal bias or deficiencies in climate models.Paleoclimate data assimilation(PDA),which integrates proxy records with climate model simulations,provides an advanced method for generating global seasonal temperature reanalysis datasets for the mid-Holocene(MH).Assimilated results indicate that MH Eurasian temperatures are largely independent of the choice of model priors and exhibit significant spatial heterogeneity.Compared to the pre-industrial(PI)period,the MH is characterized by winter and annual mean warming in Europe and high-latitude Eurasia,while the rest of Eurasia experiences cooling.However,this spatial heterogeneity is not well represented in model simulations due to a pronounced winter cooling bias at high latitudes,likely resulting from inadequate representations of vegetation and sea ice feedback mechanisms.As Eurasian proxy records are predominantly concentrated in Europe,this regional imbalance introduces a warm bias in reconstructed winter and annual temperatures intended to represent broader Eurasian temperature changes.These results suggest that the HTC may stem from both the uneven spatial distribution of proxy records and the incomplete representation of internal climate feedbacks in current models.
基金supported by the National Natural Science Foundation of China(Grant Nos.42130511,42488201)the“Geo X”Interdisciplinary Research Funds for the Frontiers Science Center for Critical Earth Material Cycling,Nanjing University(Grant Nos.202330029&2023300286)。
文摘The reconstruction of global annual mean temperatures made by the PAGES 2k Consortium in 2019 represents one of the most influential sequences of global climate variability over the Common Era.However,it is still not clear how the reconstruction can be influenced by the selection of reconstruction methods and the selection of proxy records with different temporal resolutions over different regions.We adopt a widely used Composite-Plus-Scale method to elucidate the effects of the selection of the proxy records on temperature reconstruction.To ensure the uniformity of data,different types of proxy records spanning the past~2000 years from the PAGES 2k proxy network were used to investigate the potential effects of proxy selection in hemispheric and global temperature reconstructions during the past two millennia.The long-term trends,spectral characteristics,and volcanic responses of the annual temperatures were studied based on the reconstructions.Our results reveal a significant cooling trend in the global annual mean temperature using both tree-ring and non-tree-ring records during the 1–1850CE period,and show that the cooling exhibits a stronger trend in the Southern Hemisphere(SH)than that in the Northern Hemisphere(NH).Yet,the long-term trends vary according to different combinations of proxy records.Different reconstructions based on different types of proxies also exhibit different features in terms of volcanic responses and spectral properties.Tree-ring-based temperature reconstructions show stronger cooling responses to tropical volcanic eruptions,while non-tree-ring-based reconstructions suggest less robust volcanic responses,which may be related to dating uncertainties and low temporal resolution of the proxies.Tree-ring width records tend to preserve a substantial proportion of high-frequency(<200 years)variability,whereas non-tree-ring proxies tend to capture a larger fraction of low-frequency(>200 years)variations.Efforts are needed to reduce uncertainties of the temperature reconstruction over the Common Era associated with the insufficient spatiotemporal coverage of the current proxy network,especially for the first millennium and for the SH and tropics,also to develop statistical methods and to improve the signal strength and constrain uncertainties in existing proxy records.
基金funded by the National Science Foundation and Birbal Sahni Institute of Palaeobotany.
文摘Microscopic charcoal preserved in sediments of the Lashly Formation(Middle to Late Triassic)of South Victoria Land(SVL),Antarctica provides a proxy record of palaeofire.These charred fragments derived from wood and leaf pieces along with spores and pollen grains are part of the buried plant biomass preserved in the shale and carbonaceous shale of fluvial/lacustrine deposits.The evidence of paleofire in Antarctica during the Triassic Period is supported by the presence of a thin bed of silicic tuff interlayered with Dicroidiumbearing shale.The detailed morphology and comparative anatomy of least to high thermally altered plant fragments observed under the light,fluorescence and scanning electron microscope demonstrates the evidence of effect of fire on the vegetation during Middle to Late Triassic(240-200 million years).Most of the charred particles retain identifiable structures with well-preserved to distorted cellular details.Such plant fragments are dark brown,blackish brown,quadrangular-multiangular,equi-dimensional,opaque up to the edges and nonfluorescent.The pollen grains recorded from several sedimentary sequences(but the new data come from only one level i.e.,member C of Lashly Formation)show distorted exinal sculptures and are light to dark brown in colour indicating intensive thermal effect.The detailed microscopic images of such fire-affected plant remains also explain their preservation biases in the sediments.The magnitude of the charred pieces and their abundance peaks from various locations in Allan Hills is related solely to the production and amount of burnt material embodied in the sediments.The high peaks indicate severity of fire and production of maximum charcoal of the standing vegetation in Allan Hills.
基金supported by the Ministry of Science and Technology of China (Grant Nos. 2007BAC29B02, 2007BAC03A01 and GYHY201206012)
文摘An overview of basic research on climate change in recent years in China is presented. In the past 100 years in China, average annual mean surface air temperature （SAT） has increased at a rate ranging from 0.03℃ （10 yr）-1 to 0.12℃ （10 yr）-1. This warming is more evident in northern China and is more significant in winter and spring. In the past 50 years in China, at least 27% of the average annual warming has been caused by urbanization. Overall, no significant trends have been detected in annual and/or summer precipitation in China on a whole for the past 100 years or 50 years. Both increases and decreases in frequencies of major extreme climate events have been observed for the past 50 years. The frequencies of extreme temperature events have generally displayed a consistent pattern of change across the country, while the frequencies of extreme precipitation events have shown only regionally and seasonally significant trends. The frequency of tropical cyclone landfall decreased slightly, but the frequency of sand/dust storms decreased significantly. Proxy records indicate that the annual mean SAT in the past a few decades is the highest in the past 400-500 years in China, but it may not have exceeded the highest level of the Medieval Warm Period （1000 1300 AD）. Proxy records also indicate that droughts and floods in eastern China have been characterized by continuously abnormal rainfall periods, with the frequencies of extreme droughts and floods in the 20th century most likely being near the average levels of the past 2000 years. The attribution studies suggest that increasing greenhouse gas （GHG） concentrations in the atmosphere are likely to be a main factor for the observed surface warming nationwide. The Yangtze River and Huaihe River basins underwent a cooling trend in summer over the past 50 years, which might have been caused by increased aerosol concentrations and cloud cover. However, natural climate variability might have been a main driver for the mean and extreme precipitation variations observed over the past century. Climate models generally perform well in simulating the variations of annual mean SAT in China. They have also been used to project future changes in SAT under varied GHG emission scenarios. Large uncertainties have remained in these model-based projections, however, especially for the projected trends of regional precipitation and extreme climate events.
基金supported by the State Key Laboratory of Loess Science(SKLLQGZR2401)the National Natural Science Foundation of China(42372218,42488201,and 423B2204)Guangxi Key Science and Technology Innovation Base on Karst Dynamics(KDL&Guangxi202005)。
文摘Whether the Atlantic Meridional Overturning Circulation(AMOC),one of the most vital tipping elements in the Earth’s cli-mate system with far-reaching effects on interhemispheric heat distributions,the carbon cycles,and a cascade series of hydrocli-matic changes worldwide,is approaching a tipping point has become an increasingly urgent concern[1-4].Climate proxy records arguably suggest that the AMOC is currently at its weakest state over the last millennium,with a marked AMOC weakening trend evident between 1870 and 2020 C.E.[3].A recent physics-based analysis of early warning signals even suggests that an AMOC collapse could occur as early as one year from 2024 C.E.[2].Nevertheless,the IPCC AR6,based on simulations from the Cli-mate Model Intercomparison Project(CMIP),quotes that an AMOC collapse in the 21st century is unlikely(Fig.S1 online)[2].This data-model discrepancy suggests unaccounted-for factors have been influencing AMOC[1].While the AMOC collapse would pose severe cascading impacts on global climate disruption,consider-able uncertainty remains regarding whether and when such an AMOC collapse is coming[2,4,5].One approach to address this challenge lies in a precise comparison of the ongoing AMOC weak-ening with their analogous episodes preserved in paleoclimate records-putting the AMOC weakening into context with a series of presumable AMOC collapse scenarios inferred from Greenland ice core oxygen isotope(d18 O,mainly a proxy of Greenland tem-perature)records[6-8](Fig.S2b online).
基金supported by the Basic Science Center for Tibetan Plateau Earth System,the National Natural Science Foundation of China(41988101)。
文摘The Holocene epoch spans the interval from~11,700 years ago to the present.During this period,the overall change in global average annual insolation was minimal(~0.01 W m-2),though it was marked by significant regional and seasonal variability.At the same time,atmospheric greenhouse gas concentrations have steadily increased since the mid-Holocene(MH)(~0.46 W m^(-2)).A comprehensive understanding of the evolution of Holocene temperatures in China is crucial for contextualizing current global warming within historical climate periods,and for unraveling the patterns of human-environment interactions over time.Early studies,primarily based on the integration of proxy records,suggested that temperatures in China during the early to mid-Holocene were higher than those of the pre-industrial(Pl)period,giving rise to the widely accepted concept of the"Holocene Thermal Maximum"(HTM)[1].
基金the financial support from the Faculty of Health and Life Sciences of the Linnaeus University (Kalmar, Sweden)
文摘We present the major results from studies of fire history over the last 11000 years(Holocene) in southern Sweden, on the basis of palaeoecological analyses of peat sequences from three small peat bogs. The main objective is to emphasize the value of multiple, continuous sedimentary records of macroscopic charcoal(macro-C) for the reconstruction of local to regional past changes in fire regimes, the importance of multi-proxy studies, and the advantage of model-based estimates of plant cover from pollen data to assess the role of tree composition and human impact in fire history. The chronologies at the three study sites are based on a large number of 14 C dates from terrestrial plant remains and age-depth models are achieved using Bayesian statistics. Fire history is inferred from continuous records of macro-C and microscopic charcoal counts on pollen slides. The Landscape Reconstruction Algorithm(LRA) for pollen-based quantitative reconstruction of local vegetation cover is applied on the three pollen records for plant cover reconstruction over the entire Holocene. The results are as follows:(1) the long-term trends in fire regimes are similar between sites, i.e., frequent fires during the early Holocene until ca. 9 ka BP, low fire frequency during the mid-Holocene, and higher fire frequency from ca. 2.5 ka BP;(2) this broad trend agrees with the overall fire history of northwestern and western Europe north of the Mediterranean area, and is due to climate forcing in the early and mid-Holocene, and to anthropogenic land-use in the late Holocene;(3) the LRA estimates of plant cover at the three sites demonstrate that the relative abundance of pine played a primordial role in the early and mid-Holocene fire history; and(4) the between-site differences in the charcoal records and inferred fire history are due to local factors(i.e., relative abundance of pine, geomorphological setting, and anthropogenic land-use) and taphonomy of charcoal deposition in the small peat bogs. It is shown that continuous macro-C records are most useful to disentangle local from regional-subcontinental fire history, and climate-induced from human-induced fire regimes, and that pollen-based LRA estimates of local plant cover are more adequate than pollen percentages for the assessment of the role of plant composition on fire history.
