Pub Date : 2023-02-28DOI: 10.1177/09596836231151834
Alejandra I. Domic, M. E. de Porras, J. Capriles, Andrés Zamora-Allendes, S. Ivory, A. Maldonado
The Late-Holocene history of hydroclimatic variability in the Atacama Desert offers insights into the effects of precipitation and humans on ecosystems in one of the most extremely arid regions of the world. However, understanding the effects of regional precipitation variability in relation to local ecological stressors remains to be fully resolved. Here, we present a pollen-based qualitative precipitation reconstruction derived from fossil rodent middens recovered from two sites near Laguna Roja (LRO; n = 25) and Isluga (ISL; n = 15) in the Atacama highlands (19°S) of northern Chile. At LRO, the fossil pollen record shows multi-centennial hydroclimatic anomalies during the last millennium, with wetter than present phases at 1155–1130, 865–670, and 215–80 cal yrs BP, and similar to present conditions between 1005 and 880 cal yrs BP. In contrast, the ISL record shows a wet phase during 1115–840 cal yrs BP, suggesting that meso-ecological processes were as important in vegetation turnover as regional hydroclimate anomalies. Wetter conditions derived from LRO partially overlap with the Medieval Climate Anomaly (865–670 cal yrs BP) and with the latest part of the Little Ice Age (215–80 cal yrs BP). Furthermore, no strong anthropogenic signal was identified possibly related to the remote location of the records. Palynological diversity analyses evidence increasing diversification of plant communities during wet events at both sites. In correlation to existing regional hydroclimatic records from the Western Andes, our precipitation reconstruction verifies that centennial-scale changes in the strength of the South American Summer Monsoon (SASM) and partial influence of El Niño-like (ENSO) conditions drove vegetation turnover in the Atacama Desert during the last millennium.
{"title":"Precipitation variability, vegetation turnover, and anthropogenic disturbance over the last millennium in the Atacama highlands of northern Chile (19°S)","authors":"Alejandra I. Domic, M. E. de Porras, J. Capriles, Andrés Zamora-Allendes, S. Ivory, A. Maldonado","doi":"10.1177/09596836231151834","DOIUrl":"https://doi.org/10.1177/09596836231151834","url":null,"abstract":"The Late-Holocene history of hydroclimatic variability in the Atacama Desert offers insights into the effects of precipitation and humans on ecosystems in one of the most extremely arid regions of the world. However, understanding the effects of regional precipitation variability in relation to local ecological stressors remains to be fully resolved. Here, we present a pollen-based qualitative precipitation reconstruction derived from fossil rodent middens recovered from two sites near Laguna Roja (LRO; n = 25) and Isluga (ISL; n = 15) in the Atacama highlands (19°S) of northern Chile. At LRO, the fossil pollen record shows multi-centennial hydroclimatic anomalies during the last millennium, with wetter than present phases at 1155–1130, 865–670, and 215–80 cal yrs BP, and similar to present conditions between 1005 and 880 cal yrs BP. In contrast, the ISL record shows a wet phase during 1115–840 cal yrs BP, suggesting that meso-ecological processes were as important in vegetation turnover as regional hydroclimate anomalies. Wetter conditions derived from LRO partially overlap with the Medieval Climate Anomaly (865–670 cal yrs BP) and with the latest part of the Little Ice Age (215–80 cal yrs BP). Furthermore, no strong anthropogenic signal was identified possibly related to the remote location of the records. Palynological diversity analyses evidence increasing diversification of plant communities during wet events at both sites. In correlation to existing regional hydroclimatic records from the Western Andes, our precipitation reconstruction verifies that centennial-scale changes in the strength of the South American Summer Monsoon (SASM) and partial influence of El Niño-like (ENSO) conditions drove vegetation turnover in the Atacama Desert during the last millennium.","PeriodicalId":50402,"journal":{"name":"Holocene","volume":"33 1","pages":"536 - 549"},"PeriodicalIF":2.4,"publicationDate":"2023-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46213213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-28DOI: 10.1177/09596836231157061
Seungki Kwak, K. Park, Gyoung-Ah Lee
This study investigates Neolithic subsistence on Jeju Island in Korea during the Early Holocene. Gosanri, our main site, provides evidence of the Early Holocene peopling to the Island by 10,000 cal. BP with pottery making tradition, while the Neolithic sites appeared in the Korean peninsula only 2000 years later. Gosanri and most of the Early Holocene sites, collectively called the Incipient Neolithic (10,000–8000 cal. BP), are located along the coastal lines of Jeju, and thus Incipient Neolithic people were assumed to conduct marine-based subsistence activities. This assumption has not been tested partly as most sites did not preserve any organic remains that can reflect diet. We examine this unanswered question by providing direct evidence on diet through the compound specific isotope analysis on pottery and by examining the stone tool compositions for procuring food. Our analyses suggest that Early Holocene islanders relied on terrestrial resource substantially. The proximity to the coast is not a self-sufficient evidence for the assumption of marine-oriented diet. Instead, the seasonality of food resources, the seasonal climate fluctuation, and the locational merit to a quarry, all equally affected Jeju islanders’ diet preference and subsistence practice. Overall Gosanri provides another convincing case of the broad-spectrum resource use to the transition to the Early Holocene.
{"title":"Early Holocene dietary patterns on the Neolithic Jeju Island, South Korea: Evidence from stone tools and stable carbon isotope analysis","authors":"Seungki Kwak, K. Park, Gyoung-Ah Lee","doi":"10.1177/09596836231157061","DOIUrl":"https://doi.org/10.1177/09596836231157061","url":null,"abstract":"This study investigates Neolithic subsistence on Jeju Island in Korea during the Early Holocene. Gosanri, our main site, provides evidence of the Early Holocene peopling to the Island by 10,000 cal. BP with pottery making tradition, while the Neolithic sites appeared in the Korean peninsula only 2000 years later. Gosanri and most of the Early Holocene sites, collectively called the Incipient Neolithic (10,000–8000 cal. BP), are located along the coastal lines of Jeju, and thus Incipient Neolithic people were assumed to conduct marine-based subsistence activities. This assumption has not been tested partly as most sites did not preserve any organic remains that can reflect diet. We examine this unanswered question by providing direct evidence on diet through the compound specific isotope analysis on pottery and by examining the stone tool compositions for procuring food. Our analyses suggest that Early Holocene islanders relied on terrestrial resource substantially. The proximity to the coast is not a self-sufficient evidence for the assumption of marine-oriented diet. Instead, the seasonality of food resources, the seasonal climate fluctuation, and the locational merit to a quarry, all equally affected Jeju islanders’ diet preference and subsistence practice. Overall Gosanri provides another convincing case of the broad-spectrum resource use to the transition to the Early Holocene.","PeriodicalId":50402,"journal":{"name":"Holocene","volume":"33 1","pages":"695 - 706"},"PeriodicalIF":2.4,"publicationDate":"2023-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45949106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-18DOI: 10.1177/09596836231151823
Sabine Prader, L. Gillson, B. Chase, M. Hoffman
Fynbos and afrotemperate forest exist as alternate stable states in the Cape Floristic Region of South Africa. In parts of Table Mountain National Park, afrotemperate forest has expanded in recent decades. The aim of this project was to explore the drivers of this change and distinguish whether this expansion represents a recovery of forest after previous clearance during the 18th century or is a novel expansion of forest range that resulted from policies of fire suppression in the 20th century. To determine the relationships between forest and fynbos and its key drivers, pollen, non-pollen palynomorphs, charcoal, stable isotope ratios (δ13C) and major and trace elements were analysed from late-Holocene sediments extracted from Orange Kloof. Pollen data show that forest cover has fluctuated over the past 3690 years. At the start of the record, under drier conditions from 1670 BCE to ~170 CE, forests contracted, and dry, asteraceous fynbos dominated the landscape. Around ~170 CE there was a shift to ericaceous fynbos as water availability increased. Weak signals of Khoekhoen pastoralists may be visible in the record around 50 CE, indicated by increased spores and charcoal. A regime shift towards increased dominance of the forest occurred ~250 CE, associated with wetter climate. Clear anthropogenic signals are associated with European settlement from 1650 CE. Reinforced by human clearance of forest, fynbos expanded during the cool conditions of the late phase of Little Ice Age (~1750–1850 CE). Forest expansion in the 20th century likely reflects fire suppression and recovery from past forest clearance. Fire needs to be managed accordingly if further expansion of forest into fynbos is to be curbed.
{"title":"Late-Holocene fynbos-forest dynamics in Orange Kloof, Table Mountain National Park, South Africa","authors":"Sabine Prader, L. Gillson, B. Chase, M. Hoffman","doi":"10.1177/09596836231151823","DOIUrl":"https://doi.org/10.1177/09596836231151823","url":null,"abstract":"Fynbos and afrotemperate forest exist as alternate stable states in the Cape Floristic Region of South Africa. In parts of Table Mountain National Park, afrotemperate forest has expanded in recent decades. The aim of this project was to explore the drivers of this change and distinguish whether this expansion represents a recovery of forest after previous clearance during the 18th century or is a novel expansion of forest range that resulted from policies of fire suppression in the 20th century. To determine the relationships between forest and fynbos and its key drivers, pollen, non-pollen palynomorphs, charcoal, stable isotope ratios (δ13C) and major and trace elements were analysed from late-Holocene sediments extracted from Orange Kloof. Pollen data show that forest cover has fluctuated over the past 3690 years. At the start of the record, under drier conditions from 1670 BCE to ~170 CE, forests contracted, and dry, asteraceous fynbos dominated the landscape. Around ~170 CE there was a shift to ericaceous fynbos as water availability increased. Weak signals of Khoekhoen pastoralists may be visible in the record around 50 CE, indicated by increased spores and charcoal. A regime shift towards increased dominance of the forest occurred ~250 CE, associated with wetter climate. Clear anthropogenic signals are associated with European settlement from 1650 CE. Reinforced by human clearance of forest, fynbos expanded during the cool conditions of the late phase of Little Ice Age (~1750–1850 CE). Forest expansion in the 20th century likely reflects fire suppression and recovery from past forest clearance. Fire needs to be managed accordingly if further expansion of forest into fynbos is to be curbed.","PeriodicalId":50402,"journal":{"name":"Holocene","volume":"33 1","pages":"592 - 604"},"PeriodicalIF":2.4,"publicationDate":"2023-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49148085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-11DOI: 10.1177/09596836231151828
N. Fagel, P. Pedreros, Denisse Álvarez, Isabel Israde Alcántara, Ignacio Vega Alay, O. Namur, A. Araneda, S. Schmidt, G. Lepoint, R. Urrutia
The environmental variability of Northern Chilean Patagonia during the last millennia is evaluated using a multi-proxy analysis of sediment cores from Lake Esponja (45°S 72°W) to decipher if the sediment deposition is controlled by volcanic eruptions, landslides induced by earthquake or heavy rainfall. The lake is located in a glacio-tectonic valley in Patagonia. The organic-rich clayey silt sediment with low biogenic silica content was analysed for grain size, magnetic susceptibility, organic matter, biogenic silica content and diatom assemblages, mineralogy (X-ray diffraction), organic (IRMS C and N analyses) and inorganic (XRF core-scanner) geochemistry and glass shard major composition (Microprobe, SEM). The combination of 210Pb, 137Cs, 14C and tephrochronology indicates an averaged accumulation rate of 0.4 mm/year, leading to a record of ~3.5 kyr within 154 cm. The sedimentary geochemistry records changes in volcanic supplies, diatom productivity and detrital inputs. The sediments were interrupted by millimetric to centimetric layers corresponding to tephra deposition related to explosive eruptions of nearby volcanoes Macá, Melimoyu and Hudson. Concerning the diatoms, the dominant planktonic species (80–150 cm) are replaced by benthic species in a transition interval (55–80 cm) and then by Surirella spp. in the upper core. This last genus indicates a closure of the basin ~2 ka ago, probably related to an uplift linked to a rejuvenation of the Mañihuales fault. This local change could reflect regional tectonic instability. Indeed, a partial earthquake rupture occurred around ~AD100 along the southern part of the Valdivia segment, recorded as a mass transport deposit in Aysén fjord sedimentation. The fine detrital input varies over time with more variable Si/Al values in the lower part of the LEs14 core than in the upper 80 cm. The higher values may reflect wetter conditions, leading to an higher lake level and more turbid conditions in agreement with changes in diatom assemblages.
{"title":"Volcanic, tectonic and climate controls on lacustrine sedimentary supplies over the last millenia in NE Chilean Patagonia (Lake Esponja, Aysen, 45°S)","authors":"N. Fagel, P. Pedreros, Denisse Álvarez, Isabel Israde Alcántara, Ignacio Vega Alay, O. Namur, A. Araneda, S. Schmidt, G. Lepoint, R. Urrutia","doi":"10.1177/09596836231151828","DOIUrl":"https://doi.org/10.1177/09596836231151828","url":null,"abstract":"The environmental variability of Northern Chilean Patagonia during the last millennia is evaluated using a multi-proxy analysis of sediment cores from Lake Esponja (45°S 72°W) to decipher if the sediment deposition is controlled by volcanic eruptions, landslides induced by earthquake or heavy rainfall. The lake is located in a glacio-tectonic valley in Patagonia. The organic-rich clayey silt sediment with low biogenic silica content was analysed for grain size, magnetic susceptibility, organic matter, biogenic silica content and diatom assemblages, mineralogy (X-ray diffraction), organic (IRMS C and N analyses) and inorganic (XRF core-scanner) geochemistry and glass shard major composition (Microprobe, SEM). The combination of 210Pb, 137Cs, 14C and tephrochronology indicates an averaged accumulation rate of 0.4 mm/year, leading to a record of ~3.5 kyr within 154 cm. The sedimentary geochemistry records changes in volcanic supplies, diatom productivity and detrital inputs. The sediments were interrupted by millimetric to centimetric layers corresponding to tephra deposition related to explosive eruptions of nearby volcanoes Macá, Melimoyu and Hudson. Concerning the diatoms, the dominant planktonic species (80–150 cm) are replaced by benthic species in a transition interval (55–80 cm) and then by Surirella spp. in the upper core. This last genus indicates a closure of the basin ~2 ka ago, probably related to an uplift linked to a rejuvenation of the Mañihuales fault. This local change could reflect regional tectonic instability. Indeed, a partial earthquake rupture occurred around ~AD100 along the southern part of the Valdivia segment, recorded as a mass transport deposit in Aysén fjord sedimentation. The fine detrital input varies over time with more variable Si/Al values in the lower part of the LEs14 core than in the upper 80 cm. The higher values may reflect wetter conditions, leading to an higher lake level and more turbid conditions in agreement with changes in diatom assemblages.","PeriodicalId":50402,"journal":{"name":"Holocene","volume":"33 1","pages":"518 - 535"},"PeriodicalIF":2.4,"publicationDate":"2023-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47664255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-09DOI: 10.1177/09596836231151821
Nannan Li, F. Yu, F. Chambers, Zhaoquan Huang, Wen-Chiang Lin, Zilong Zhu, Huanjie Yang, Jiaqi Lin
Holocene paleoclimate reconstructions and comparisons largely rely on accurate age-depth modeling. However, uncertainties in chronology, such as those caused by sparse radiocarbon dates, will hamper inter-core comparisons and correlations, and might result in misleading “cause and consequence” conclusions. This study aimed to find a solution to increase the comparability and minimize the uncertainty of wetland chronology as much as possible. Sediment cores were recovered and radiocarbon dated from the Lianhuachi wetland located in Southeastern China. Humification degree and loss-on-ignition (LOI) were determined using colorimetric and combustion methods respectively. Our data were compared with previously published datasets obtained in the same wetland. The results show that independent humification profiles from the Lianhuachi wetland displayed high similarities. This high similarity between the humification profiles allowed us to transfer radiocarbon ages from one core to another using sequence slotting correlation. Applying the humification-based chronology refinement method to all sediment cores resulted in an improvement in the correlation coefficients between the same but independently measured proxy sequences from the wetland, which suggests both the inter- and intra-core comparability was improved. Because determining peat humification degree is easy, inexpensive, and time-saving, we suggest that humification can serve as a tool that can be used to correlate different cores and to transfer published radiocarbon ages within the same wetland (peatland) or in a comparable geological setting, to establish a more robust chronology of these comparable cores. The degree of peat humification can thus serve as a relative dating technique to refine the chronology of wetland (including peatland) records.
{"title":"A humification-based method toward refining Holocene radiocarbon chronologies: Wetland records from southeastern China","authors":"Nannan Li, F. Yu, F. Chambers, Zhaoquan Huang, Wen-Chiang Lin, Zilong Zhu, Huanjie Yang, Jiaqi Lin","doi":"10.1177/09596836231151821","DOIUrl":"https://doi.org/10.1177/09596836231151821","url":null,"abstract":"Holocene paleoclimate reconstructions and comparisons largely rely on accurate age-depth modeling. However, uncertainties in chronology, such as those caused by sparse radiocarbon dates, will hamper inter-core comparisons and correlations, and might result in misleading “cause and consequence” conclusions. This study aimed to find a solution to increase the comparability and minimize the uncertainty of wetland chronology as much as possible. Sediment cores were recovered and radiocarbon dated from the Lianhuachi wetland located in Southeastern China. Humification degree and loss-on-ignition (LOI) were determined using colorimetric and combustion methods respectively. Our data were compared with previously published datasets obtained in the same wetland. The results show that independent humification profiles from the Lianhuachi wetland displayed high similarities. This high similarity between the humification profiles allowed us to transfer radiocarbon ages from one core to another using sequence slotting correlation. Applying the humification-based chronology refinement method to all sediment cores resulted in an improvement in the correlation coefficients between the same but independently measured proxy sequences from the wetland, which suggests both the inter- and intra-core comparability was improved. Because determining peat humification degree is easy, inexpensive, and time-saving, we suggest that humification can serve as a tool that can be used to correlate different cores and to transfer published radiocarbon ages within the same wetland (peatland) or in a comparable geological setting, to establish a more robust chronology of these comparable cores. The degree of peat humification can thus serve as a relative dating technique to refine the chronology of wetland (including peatland) records.","PeriodicalId":50402,"journal":{"name":"Holocene","volume":"33 1","pages":"605 - 615"},"PeriodicalIF":2.4,"publicationDate":"2023-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47461197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-08DOI: 10.1177/09596836231151827
M. Constantine, Xiaohong Zhu, Haidee R. Cadd, S. Mooney
The drivers of fire regimes prior to the European occupation of Australia are still contentious, with some advocating regimes dominated by anthropogenic ignitions and others advocating a climate source or mixture of these elements. Here, we examine an 850-year history of fire regimes at Lake Werri Berri in south-east Australia, prior to and following European occupation. Macroscopic charcoal and FTIR spectroscopy were used to infer broad changes of the fire regime in proximity to the lake. We found little change through much of the 850-year period and most interesting, no apparent change following the initial displacement of Indigenous peoples and the introduction of farming and woodcutting to the region by Europeans. From the mid-20th Century onwards, there was an increase in both area burnt and fire severity or intensity, likely the result of increased fuel load and connectivity following an extended period of increased precipitation and heavier recreational land usage, which likely led to an increase in anthropogenic ignitions.
{"title":"The transition from an Indigenous to a European influenced fire regime at Lake Werri Berri, south-east Australia","authors":"M. Constantine, Xiaohong Zhu, Haidee R. Cadd, S. Mooney","doi":"10.1177/09596836231151827","DOIUrl":"https://doi.org/10.1177/09596836231151827","url":null,"abstract":"The drivers of fire regimes prior to the European occupation of Australia are still contentious, with some advocating regimes dominated by anthropogenic ignitions and others advocating a climate source or mixture of these elements. Here, we examine an 850-year history of fire regimes at Lake Werri Berri in south-east Australia, prior to and following European occupation. Macroscopic charcoal and FTIR spectroscopy were used to infer broad changes of the fire regime in proximity to the lake. We found little change through much of the 850-year period and most interesting, no apparent change following the initial displacement of Indigenous peoples and the introduction of farming and woodcutting to the region by Europeans. From the mid-20th Century onwards, there was an increase in both area burnt and fire severity or intensity, likely the result of increased fuel load and connectivity following an extended period of increased precipitation and heavier recreational land usage, which likely led to an increase in anthropogenic ignitions.","PeriodicalId":50402,"journal":{"name":"Holocene","volume":"33 1","pages":"505 - 517"},"PeriodicalIF":2.4,"publicationDate":"2023-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41644407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-31DOI: 10.1177/09596836231151801
T. Utescher, Sushma Prasad, Nils Riedel, M. Stebich
Diversity of Plant Functional Types (PFTs) along a sediment core drilled in Lonar Crater Lake, Central India, is analysed, based on previously published pollen data for a total of 115 depth levels and covering the past 9.2 kyr. Our results support concepts of a dominantly humid period persisting until ca. 5 ka, succeeded by a significantly drier phase with weaker monsoon, including various prominent drying pulses. Throughout the Holocene, plant diversity at Lonar was composed of a variable proportion of herbaceous PFTs (ca. 40–60%) and mainly angiosperm woody PFTs. Changes in herbaceous diversity account for a considerable part of the observed PFT data variability. PCA analysis reveals a total of four partly alternating diversity associations (DAs) interpretable in terms of vegetation spanning from drier Savanna and dry deciduous forest to (semi-) evergreen woody vegetation, mainly recorded in older strata. It is shown that the succession of the DAs is largely triggered by climate change inferred from other proxies. Correlation analysis with geochemical data testifies that the diversity signal obtained is largely unaffected by sedimentary processes and detrital inflow, highlighting the potential of this archive to reflect ‘true’ diversity signals, rather than artefacts of sedimentary processes. While warm and humid conditions promoted diversity, drying and weak monsoon tended to cause diversity loss. In contrast, the relative diversity of dry herbs increased during drier periods. Short-term variability in our data is evident in varying diversity percentages of single PFTs and their ratios. Changing ratios of dry on mesic herbs, the relation of shrub and tree diversity, tropical on temperate PFTs, and total plant diversity are likely related to solar cycles. Evidence for recurrent cooling episodes through solar forcing comes from the observed coincidence of Grand Solar Minima and minima in the tropical/temperate PFT ratio.
{"title":"Diversity patterns of plant functional types in the Holocene of Central India: A case study on the Lonar Crater Lake pollen record","authors":"T. Utescher, Sushma Prasad, Nils Riedel, M. Stebich","doi":"10.1177/09596836231151801","DOIUrl":"https://doi.org/10.1177/09596836231151801","url":null,"abstract":"Diversity of Plant Functional Types (PFTs) along a sediment core drilled in Lonar Crater Lake, Central India, is analysed, based on previously published pollen data for a total of 115 depth levels and covering the past 9.2 kyr. Our results support concepts of a dominantly humid period persisting until ca. 5 ka, succeeded by a significantly drier phase with weaker monsoon, including various prominent drying pulses. Throughout the Holocene, plant diversity at Lonar was composed of a variable proportion of herbaceous PFTs (ca. 40–60%) and mainly angiosperm woody PFTs. Changes in herbaceous diversity account for a considerable part of the observed PFT data variability. PCA analysis reveals a total of four partly alternating diversity associations (DAs) interpretable in terms of vegetation spanning from drier Savanna and dry deciduous forest to (semi-) evergreen woody vegetation, mainly recorded in older strata. It is shown that the succession of the DAs is largely triggered by climate change inferred from other proxies. Correlation analysis with geochemical data testifies that the diversity signal obtained is largely unaffected by sedimentary processes and detrital inflow, highlighting the potential of this archive to reflect ‘true’ diversity signals, rather than artefacts of sedimentary processes. While warm and humid conditions promoted diversity, drying and weak monsoon tended to cause diversity loss. In contrast, the relative diversity of dry herbs increased during drier periods. Short-term variability in our data is evident in varying diversity percentages of single PFTs and their ratios. Changing ratios of dry on mesic herbs, the relation of shrub and tree diversity, tropical on temperate PFTs, and total plant diversity are likely related to solar cycles. Evidence for recurrent cooling episodes through solar forcing comes from the observed coincidence of Grand Solar Minima and minima in the tropical/temperate PFT ratio.","PeriodicalId":50402,"journal":{"name":"Holocene","volume":"33 1","pages":"491 - 504"},"PeriodicalIF":2.4,"publicationDate":"2023-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42895180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-31DOI: 10.1177/09596836231151833
C. Åkesson, C. McMichael, S. León-Yánez, M. Bush
A high-resolution paleoecological record provides a 2690 year-long fossil pollen and charcoal history from Lake Ayauchi, Ecuador, in lowland Amazonia. The record begins with a landscape that is already partially deforested and in which maize is being grown. Dated charcoal fragments from local soils coincide with fire events and peaks of land clearance seen in the lake sediment record. After c. AD 550 grass pollen becomes less abundant, as a broad array of forest types show small increases in abundance. Between c. AD 750 and 1280, Zea mays pollen was at its most abundant. Although maize cultivation continued until the AD 1700s, forest pollen abundance showed a significant increase at c. AD 1260. Another transition at c. AD 1420, which saw a transition from dominance by early successional taxa and an increase in mid-successional elements, suggests the onset of reduced human activity at the site. Fossil maize is found in a lower proportion of samples, disappearing altogether for a century in the late 1700s. Forest taxa increase in abundance and charcoal disappears from the record at c. AD 1790. These data suggest a complex social history prior to and following European arrival with phases of forest clearing and episodes of apparent regrowth at c. AD 500, 950, and 1260. Increased forest pollen after c. AD 1260 and a reduction in maize pollen abundance suggests some abandonment, with a second, relatively late, depopulation following European Conquest (c. AD 1790). Evidence is not found supporting reforestation associated with European arrival.
{"title":"Late-Holocene maize cultivation, fire, and forest change at Lake Ayauchi, Amazonian Ecuador","authors":"C. Åkesson, C. McMichael, S. León-Yánez, M. Bush","doi":"10.1177/09596836231151833","DOIUrl":"https://doi.org/10.1177/09596836231151833","url":null,"abstract":"A high-resolution paleoecological record provides a 2690 year-long fossil pollen and charcoal history from Lake Ayauchi, Ecuador, in lowland Amazonia. The record begins with a landscape that is already partially deforested and in which maize is being grown. Dated charcoal fragments from local soils coincide with fire events and peaks of land clearance seen in the lake sediment record. After c. AD 550 grass pollen becomes less abundant, as a broad array of forest types show small increases in abundance. Between c. AD 750 and 1280, Zea mays pollen was at its most abundant. Although maize cultivation continued until the AD 1700s, forest pollen abundance showed a significant increase at c. AD 1260. Another transition at c. AD 1420, which saw a transition from dominance by early successional taxa and an increase in mid-successional elements, suggests the onset of reduced human activity at the site. Fossil maize is found in a lower proportion of samples, disappearing altogether for a century in the late 1700s. Forest taxa increase in abundance and charcoal disappears from the record at c. AD 1790. These data suggest a complex social history prior to and following European arrival with phases of forest clearing and episodes of apparent regrowth at c. AD 500, 950, and 1260. Increased forest pollen after c. AD 1260 and a reduction in maize pollen abundance suggests some abandonment, with a second, relatively late, depopulation following European Conquest (c. AD 1790). Evidence is not found supporting reforestation associated with European arrival.","PeriodicalId":50402,"journal":{"name":"Holocene","volume":"33 1","pages":"550 - 561"},"PeriodicalIF":2.4,"publicationDate":"2023-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42957885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：