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Yun Zhang - One of the best experts on this subject based on the ideXlab platform.
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Holocene climate events inferred from modern and Fossil Pollen records in Butuo Lake, Eastern Qinghai–Tibetan Plateau
Climatic Change, 2015Co-Authors: Yun Zhang, Zhaochen Kong, Qi-bin Zhang, Zhenjing YangAbstract:Expansion of the spatial coverage of Pollen data is essential to improve understanding of Holocene climate variation. To address this, we collected 25 surface and 72 Fossil samples from Butuo Lake in the eastern Qinghai–Tibetan Plateau, China. We reconstructed the vegetation history of the region through detrended correspondence analysis (DCA) of the Pollen data. Based on the results of this analysis, we divided the samples into five Pollen zones (alpine sparse cushion vegetation, alpine scrub, alpine meadow, montane scrub meadow, and montane coniferous forest) corresponding to the major vegetation types. The observed temporal changes in vegetation (as indicated by the DCA of surface and Fossil Pollen spectra results, ratios of Artemisia to Cyperaceae (A/Cy), the sum of percentages of dryness indicators (SDI), and percentages of main Pollen types) and modern Pollen–climate transfer function (developed using the weighted averaging partial least squares regression method (WAPLS)) yield a sensitive record of Holocene monsoonal climate change in the area. During 11,140–8700, 8000–6000, and 5600–1780 cal. yr BP, the climate was wet and the vegetation was dominated by alpine meadow, indicating the occurrence of a strong southwest Asian monsoon that spanned almost the entire Holocene. Notably, two major cold and drought episodes are detected at 8700–8000 and 6000–5600 cal. yr BP, with vegetation dominated by alpine steppe, suggesting that the southwest Asian monsoon was extremely weak during these periods. The data will improve understanding of long-term variations of the southwest Asian monsoon in the region.
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holocene climate events inferred from modern and Fossil Pollen records in butuo lake eastern qinghai tibetan plateau
Climatic Change, 2015Co-Authors: Yun Zhang, Zhaochen Kong, Qi-bin Zhang, Zhenjing YangAbstract:Expansion of the spatial coverage of Pollen data is essential to improve understanding of Holocene climate variation. To address this, we collected 25 surface and 72 Fossil samples from Butuo Lake in the eastern Qinghai–Tibetan Plateau, China. We reconstructed the vegetation history of the region through detrended correspondence analysis (DCA) of the Pollen data. Based on the results of this analysis, we divided the samples into five Pollen zones (alpine sparse cushion vegetation, alpine scrub, alpine meadow, montane scrub meadow, and montane coniferous forest) corresponding to the major vegetation types. The observed temporal changes in vegetation (as indicated by the DCA of surface and Fossil Pollen spectra results, ratios of Artemisia to Cyperaceae (A/Cy), the sum of percentages of dryness indicators (SDI), and percentages of main Pollen types) and modern Pollen–climate transfer function (developed using the weighted averaging partial least squares regression method (WAPLS)) yield a sensitive record of Holocene monsoonal climate change in the area. During 11,140–8700, 8000–6000, and 5600–1780 cal. yr BP, the climate was wet and the vegetation was dominated by alpine meadow, indicating the occurrence of a strong southwest Asian monsoon that spanned almost the entire Holocene. Notably, two major cold and drought episodes are detected at 8700–8000 and 6000–5600 cal. yr BP, with vegetation dominated by alpine steppe, suggesting that the southwest Asian monsoon was extremely weak during these periods. The data will improve understanding of long-term variations of the southwest Asian monsoon in the region.
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multivariate analysis of modern and Fossil Pollen data from the central tianshan mountains xinjiang nw china
Climatic Change, 2013Co-Authors: Yun Zhang, Zhaochen Kong, Hui ZhangAbstract:To interpret past vegetation and climate changes from Pollen data, we need to reveal the degree of similarity between modern analogues and Fossil Pollen spectra, which would help us predict the future climate and vegetation. Ninety surface Pollen samples across six vegetation zones along an altitudinal gradient from 460 to 3510 m and 44 Fossil samples at Caotan Lake were collected in the central Tianshan Mountains, northern Xinjiang, China. Discriminant analyses results, Fossil Pollen and phytolith assemblages were then used to reconstruct palaeovegetation and palaeoclimate in the area. The 90 surface samples were divided into six Pollen zones (alpine cushion, alpine and subalpine meadow, montane Tianshan spruce forest, forest-steppe ecotone, Artemisia desert, typical desert), corresponding to the major vegetation types in the area. These zones follow a climatic gradient of increasing precipitation with increasing elevation. Paleovegetation reconstructed from 44 Fossil Pollen assemblages through discriminant analysis reflects the regional vegetation shifted from typical desert to Artemisia desert since 4640 cal. year BP in the Caotan Lake wetland. The Fossil Pollen and phytolith record also reveal the arid climate has not fundamentally changed in the period. But a dry-wet-dry local climate oscillation since 2700 cal. year BP has a fundamental influence on local wetland vegetation dynamics and peat accumulation of the Caotan wetland. Modern wetland landscape and surface Pollen assemblages from the Ebinur Lake Wetland Nature Reserve provide further evidence for ferns and Betula growing in the Caotan Lake wetland during the historical period.
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Multivariate analysis of modern and Fossil Pollen data from the central Tianshan Mountains, Xinjiang, NW China
Climatic Change, 2013Co-Authors: Yun Zhang, Zhaochen Kong, Hui ZhangAbstract:To interpret past vegetation and climate changes from Pollen data, we need to reveal the degree of similarity between modern analogues and Fossil Pollen spectra, which would help us predict the future climate and vegetation. Ninety surface Pollen samples across six vegetation zones along an altitudinal gradient from 460 to 3510 m and 44 Fossil samples at Caotan Lake were collected in the central Tianshan Mountains, northern Xinjiang, China. Discriminant analyses results, Fossil Pollen and phytolith assemblages were then used to reconstruct palaeovegetation and palaeoclimate in the area. The 90 surface samples were divided into six Pollen zones (alpine cushion, alpine and subalpine meadow, montane Tianshan spruce forest, forest-steppe ecotone, Artemisia desert, typical desert), corresponding to the major vegetation types in the area. These zones follow a climatic gradient of increasing precipitation with increasing elevation. Paleovegetation reconstructed from 44 Fossil Pollen assemblages through discriminant analysis reflects the regional vegetation shifted from typical desert to Artemisia desert since 4640 cal. year BP in the Caotan Lake wetland. The Fossil Pollen and phytolith record also reveal the arid climate has not fundamentally changed in the period. But a dry-wet-dry local climate oscillation since 2700 cal. year BP has a fundamental influence on local wetland vegetation dynamics and peat accumulation of the Caotan wetland. Modern wetland landscape and surface Pollen assemblages from the Ebinur Lake Wetland Nature Reserve provide further evidence for ferns and Betula growing in the Caotan Lake wetland during the historical period. Copyright Springer Science+Business Media Dordrecht 2013
Hui Zhang - One of the best experts on this subject based on the ideXlab platform.
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multivariate analysis of modern and Fossil Pollen data from the central tianshan mountains xinjiang nw china
Climatic Change, 2013Co-Authors: Yun Zhang, Zhaochen Kong, Hui ZhangAbstract:To interpret past vegetation and climate changes from Pollen data, we need to reveal the degree of similarity between modern analogues and Fossil Pollen spectra, which would help us predict the future climate and vegetation. Ninety surface Pollen samples across six vegetation zones along an altitudinal gradient from 460 to 3510 m and 44 Fossil samples at Caotan Lake were collected in the central Tianshan Mountains, northern Xinjiang, China. Discriminant analyses results, Fossil Pollen and phytolith assemblages were then used to reconstruct palaeovegetation and palaeoclimate in the area. The 90 surface samples were divided into six Pollen zones (alpine cushion, alpine and subalpine meadow, montane Tianshan spruce forest, forest-steppe ecotone, Artemisia desert, typical desert), corresponding to the major vegetation types in the area. These zones follow a climatic gradient of increasing precipitation with increasing elevation. Paleovegetation reconstructed from 44 Fossil Pollen assemblages through discriminant analysis reflects the regional vegetation shifted from typical desert to Artemisia desert since 4640 cal. year BP in the Caotan Lake wetland. The Fossil Pollen and phytolith record also reveal the arid climate has not fundamentally changed in the period. But a dry-wet-dry local climate oscillation since 2700 cal. year BP has a fundamental influence on local wetland vegetation dynamics and peat accumulation of the Caotan wetland. Modern wetland landscape and surface Pollen assemblages from the Ebinur Lake Wetland Nature Reserve provide further evidence for ferns and Betula growing in the Caotan Lake wetland during the historical period.
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Multivariate analysis of modern and Fossil Pollen data from the central Tianshan Mountains, Xinjiang, NW China
Climatic Change, 2013Co-Authors: Yun Zhang, Zhaochen Kong, Hui ZhangAbstract:To interpret past vegetation and climate changes from Pollen data, we need to reveal the degree of similarity between modern analogues and Fossil Pollen spectra, which would help us predict the future climate and vegetation. Ninety surface Pollen samples across six vegetation zones along an altitudinal gradient from 460 to 3510 m and 44 Fossil samples at Caotan Lake were collected in the central Tianshan Mountains, northern Xinjiang, China. Discriminant analyses results, Fossil Pollen and phytolith assemblages were then used to reconstruct palaeovegetation and palaeoclimate in the area. The 90 surface samples were divided into six Pollen zones (alpine cushion, alpine and subalpine meadow, montane Tianshan spruce forest, forest-steppe ecotone, Artemisia desert, typical desert), corresponding to the major vegetation types in the area. These zones follow a climatic gradient of increasing precipitation with increasing elevation. Paleovegetation reconstructed from 44 Fossil Pollen assemblages through discriminant analysis reflects the regional vegetation shifted from typical desert to Artemisia desert since 4640 cal. year BP in the Caotan Lake wetland. The Fossil Pollen and phytolith record also reveal the arid climate has not fundamentally changed in the period. But a dry-wet-dry local climate oscillation since 2700 cal. year BP has a fundamental influence on local wetland vegetation dynamics and peat accumulation of the Caotan wetland. Modern wetland landscape and surface Pollen assemblages from the Ebinur Lake Wetland Nature Reserve provide further evidence for ferns and Betula growing in the Caotan Lake wetland during the historical period. Copyright Springer Science+Business Media Dordrecht 2013
Zhaochen Kong - One of the best experts on this subject based on the ideXlab platform.
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Holocene climate events inferred from modern and Fossil Pollen records in Butuo Lake, Eastern Qinghai–Tibetan Plateau
Climatic Change, 2015Co-Authors: Yun Zhang, Zhaochen Kong, Qi-bin Zhang, Zhenjing YangAbstract:Expansion of the spatial coverage of Pollen data is essential to improve understanding of Holocene climate variation. To address this, we collected 25 surface and 72 Fossil samples from Butuo Lake in the eastern Qinghai–Tibetan Plateau, China. We reconstructed the vegetation history of the region through detrended correspondence analysis (DCA) of the Pollen data. Based on the results of this analysis, we divided the samples into five Pollen zones (alpine sparse cushion vegetation, alpine scrub, alpine meadow, montane scrub meadow, and montane coniferous forest) corresponding to the major vegetation types. The observed temporal changes in vegetation (as indicated by the DCA of surface and Fossil Pollen spectra results, ratios of Artemisia to Cyperaceae (A/Cy), the sum of percentages of dryness indicators (SDI), and percentages of main Pollen types) and modern Pollen–climate transfer function (developed using the weighted averaging partial least squares regression method (WAPLS)) yield a sensitive record of Holocene monsoonal climate change in the area. During 11,140–8700, 8000–6000, and 5600–1780 cal. yr BP, the climate was wet and the vegetation was dominated by alpine meadow, indicating the occurrence of a strong southwest Asian monsoon that spanned almost the entire Holocene. Notably, two major cold and drought episodes are detected at 8700–8000 and 6000–5600 cal. yr BP, with vegetation dominated by alpine steppe, suggesting that the southwest Asian monsoon was extremely weak during these periods. The data will improve understanding of long-term variations of the southwest Asian monsoon in the region.
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holocene climate events inferred from modern and Fossil Pollen records in butuo lake eastern qinghai tibetan plateau
Climatic Change, 2015Co-Authors: Yun Zhang, Zhaochen Kong, Qi-bin Zhang, Zhenjing YangAbstract:Expansion of the spatial coverage of Pollen data is essential to improve understanding of Holocene climate variation. To address this, we collected 25 surface and 72 Fossil samples from Butuo Lake in the eastern Qinghai–Tibetan Plateau, China. We reconstructed the vegetation history of the region through detrended correspondence analysis (DCA) of the Pollen data. Based on the results of this analysis, we divided the samples into five Pollen zones (alpine sparse cushion vegetation, alpine scrub, alpine meadow, montane scrub meadow, and montane coniferous forest) corresponding to the major vegetation types. The observed temporal changes in vegetation (as indicated by the DCA of surface and Fossil Pollen spectra results, ratios of Artemisia to Cyperaceae (A/Cy), the sum of percentages of dryness indicators (SDI), and percentages of main Pollen types) and modern Pollen–climate transfer function (developed using the weighted averaging partial least squares regression method (WAPLS)) yield a sensitive record of Holocene monsoonal climate change in the area. During 11,140–8700, 8000–6000, and 5600–1780 cal. yr BP, the climate was wet and the vegetation was dominated by alpine meadow, indicating the occurrence of a strong southwest Asian monsoon that spanned almost the entire Holocene. Notably, two major cold and drought episodes are detected at 8700–8000 and 6000–5600 cal. yr BP, with vegetation dominated by alpine steppe, suggesting that the southwest Asian monsoon was extremely weak during these periods. The data will improve understanding of long-term variations of the southwest Asian monsoon in the region.
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multivariate analysis of modern and Fossil Pollen data from the central tianshan mountains xinjiang nw china
Climatic Change, 2013Co-Authors: Yun Zhang, Zhaochen Kong, Hui ZhangAbstract:To interpret past vegetation and climate changes from Pollen data, we need to reveal the degree of similarity between modern analogues and Fossil Pollen spectra, which would help us predict the future climate and vegetation. Ninety surface Pollen samples across six vegetation zones along an altitudinal gradient from 460 to 3510 m and 44 Fossil samples at Caotan Lake were collected in the central Tianshan Mountains, northern Xinjiang, China. Discriminant analyses results, Fossil Pollen and phytolith assemblages were then used to reconstruct palaeovegetation and palaeoclimate in the area. The 90 surface samples were divided into six Pollen zones (alpine cushion, alpine and subalpine meadow, montane Tianshan spruce forest, forest-steppe ecotone, Artemisia desert, typical desert), corresponding to the major vegetation types in the area. These zones follow a climatic gradient of increasing precipitation with increasing elevation. Paleovegetation reconstructed from 44 Fossil Pollen assemblages through discriminant analysis reflects the regional vegetation shifted from typical desert to Artemisia desert since 4640 cal. year BP in the Caotan Lake wetland. The Fossil Pollen and phytolith record also reveal the arid climate has not fundamentally changed in the period. But a dry-wet-dry local climate oscillation since 2700 cal. year BP has a fundamental influence on local wetland vegetation dynamics and peat accumulation of the Caotan wetland. Modern wetland landscape and surface Pollen assemblages from the Ebinur Lake Wetland Nature Reserve provide further evidence for ferns and Betula growing in the Caotan Lake wetland during the historical period.
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Multivariate analysis of modern and Fossil Pollen data from the central Tianshan Mountains, Xinjiang, NW China
Climatic Change, 2013Co-Authors: Yun Zhang, Zhaochen Kong, Hui ZhangAbstract:To interpret past vegetation and climate changes from Pollen data, we need to reveal the degree of similarity between modern analogues and Fossil Pollen spectra, which would help us predict the future climate and vegetation. Ninety surface Pollen samples across six vegetation zones along an altitudinal gradient from 460 to 3510 m and 44 Fossil samples at Caotan Lake were collected in the central Tianshan Mountains, northern Xinjiang, China. Discriminant analyses results, Fossil Pollen and phytolith assemblages were then used to reconstruct palaeovegetation and palaeoclimate in the area. The 90 surface samples were divided into six Pollen zones (alpine cushion, alpine and subalpine meadow, montane Tianshan spruce forest, forest-steppe ecotone, Artemisia desert, typical desert), corresponding to the major vegetation types in the area. These zones follow a climatic gradient of increasing precipitation with increasing elevation. Paleovegetation reconstructed from 44 Fossil Pollen assemblages through discriminant analysis reflects the regional vegetation shifted from typical desert to Artemisia desert since 4640 cal. year BP in the Caotan Lake wetland. The Fossil Pollen and phytolith record also reveal the arid climate has not fundamentally changed in the period. But a dry-wet-dry local climate oscillation since 2700 cal. year BP has a fundamental influence on local wetland vegetation dynamics and peat accumulation of the Caotan wetland. Modern wetland landscape and surface Pollen assemblages from the Ebinur Lake Wetland Nature Reserve provide further evidence for ferns and Betula growing in the Caotan Lake wetland during the historical period. Copyright Springer Science+Business Media Dordrecht 2013
Surangi W. Punyasena - One of the best experts on this subject based on the ideXlab platform.
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Improving the taxonomy of Fossil Pollen using convolutional neural networks and superresolution microscopy.
Proceedings of the National Academy of Sciences of the United States of America, 2020Co-Authors: Ingrid Romero, Michael A. Urban, Francisca E. Oboh-ikuenobe, Shu Kong, Charless C. Fowlkes, Carlos Jaramillo, Carlos D'apolito, Surangi W. PunyasenaAbstract:Taxonomic resolution is a major challenge in palynology, largely limiting the ecological and evolutionary interpretations possible with deep-time Fossil Pollen data. We present an approach for Fossil Pollen analysis that uses optical superresolution microscopy and machine learning to create a quantitative and higher throughput workflow for producing palynological identifications and hypotheses of biological affinity. We developed three convolutional neural network (CNN) classification models: maximum projection (MPM), multislice (MSM), and fused (FM). We trained the models on the Pollen of 16 genera of the legume tribe Amherstieae, and then used these models to constrain the biological classifications of 48 Fossil Striatopollis specimens from the Paleocene, Eocene, and Miocene of western Africa and northern South America. All models achieved average accuracies of 83 to 90% in the classification of the extant genera, and the majority of Fossil identifications (86%) showed consensus among at least two of the three models. Our Fossil identifications support the paleobiogeographic hypothesis that Amherstieae originated in Paleocene Africa and dispersed to South America during the Paleocene-Eocene Thermal Maximum (56 Ma). They also raise the possibility that at least three Amherstieae genera (Crudia, Berlinia, and Anthonotha) may have diverged earlier in the Cenozoic than predicted by molecular phylogenies.
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Airyscan superresolution microscopy: A high-throughput alternative to electron microscopy for the visualization and analysis of Fossil Pollen
Review of Palaeobotany and Palynology, 2020Co-Authors: Ingrid Romero, Michael A. Urban, Surangi W. PunyasenaAbstract:Abstract Airyscan confocal superresolution microscopy is a new optical technique that can detect morphological features smaller than the diffraction limit of light. It captures both the external and internal ornamentation of modern and Fossil Pollen. Airyscan combines the ease of use of optical microscopy methods, such as confocal and brightfield microscopy (BM), with the high-resolution imaging of electron microscopy (EM). Modern and Fossil Pollen grains were imaged using Airyscan, BM, and EM to assess the viability of Airyscan as an alternative for EM. Our results demonstrate that: (1) Airyscan can capture diagnostic features of extant and Fossil Pollen similar to EM; (2) one-to-one comparisons of Airyscan images with other optical methods are possible (e.g., BM and conventional confocal); (3) Airyscan captures three-dimensional data, allowing reconstruction of Pollen grains in different views; and (4) the time and effort required for Airyscan imaging is significantly less than that for EM. This paper demonstrates that Airyscan superresolution microscopy is a high-throughput alternative for morphological analyses of Pollen specimens.
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Fossil Pollen and spores in paleoecology
Vertebrate Paleobiology and Paleoanthropology, 2018Co-Authors: Luke Mander, Surangi W. PunyasenaAbstract:The discipline of paleoecology is a multidisciplinary field that uses geological and biological evidence to investigate the past occurrence, distribution and abundance of species and populations on timescales ranging from hundreds to hundreds of millions of years. In this way, paleoecology is broadly concerned with the ecology of the past. In this article, we discuss how paleoecological data are derived from assemblages of Fossil Pollen and spores, which are dispersed by plants as part of their life cycles, and how this material can be used to reconstruct paleoenvironments. We outline how Pollen and spores can be analyzed and classified, and explore the potential strengths and weaknesses of paleoecological data, before considering technological and methodological developments that may play a role in the future development of this discipline.
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CVPR Workshops - Spatially Aware Dictionary Learning and Coding for Fossil Pollen Identification
2016 IEEE Conference on Computer Vision and Pattern Recognition Workshops (CVPRW), 2016Co-Authors: Shu Kong, Surangi W. Punyasena, Charless C. FowlkesAbstract:We propose a robust approach for performing automatic species-level recognition of Fossil Pollen grains in microscopy images that exploits both global shape and local texture characteristics in a patch-based matching methodology. We introduce a novel criteria for selecting meaningful and discriminative exemplar patches. We optimize this function during training using a greedy submodular function optimization framework that gives a near-optimal solution with bounded approximation error. We use these selected exemplars as a dictionary basis and propose a spatially-aware sparse coding method to match testing images for identification while maintaining global shape correspondence. To accelerate the coding process for fast matching, we introduce a relaxed form that uses spatiallyaware soft-thresholding during coding. Finally, we carry out an experimental study that demonstrates the effectiveness and efficiency of our exemplar selection and classification mechanisms, achieving 86.13% accuracy on a difficult fine-grained species classification task distinguishing three types of Fossil spruce Pollen 1.
Ingrid Romero - One of the best experts on this subject based on the ideXlab platform.
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Improving the taxonomy of Fossil Pollen using convolutional neural networks and superresolution microscopy.
Proceedings of the National Academy of Sciences of the United States of America, 2020Co-Authors: Ingrid Romero, Michael A. Urban, Francisca E. Oboh-ikuenobe, Shu Kong, Charless C. Fowlkes, Carlos Jaramillo, Carlos D'apolito, Surangi W. PunyasenaAbstract:Taxonomic resolution is a major challenge in palynology, largely limiting the ecological and evolutionary interpretations possible with deep-time Fossil Pollen data. We present an approach for Fossil Pollen analysis that uses optical superresolution microscopy and machine learning to create a quantitative and higher throughput workflow for producing palynological identifications and hypotheses of biological affinity. We developed three convolutional neural network (CNN) classification models: maximum projection (MPM), multislice (MSM), and fused (FM). We trained the models on the Pollen of 16 genera of the legume tribe Amherstieae, and then used these models to constrain the biological classifications of 48 Fossil Striatopollis specimens from the Paleocene, Eocene, and Miocene of western Africa and northern South America. All models achieved average accuracies of 83 to 90% in the classification of the extant genera, and the majority of Fossil identifications (86%) showed consensus among at least two of the three models. Our Fossil identifications support the paleobiogeographic hypothesis that Amherstieae originated in Paleocene Africa and dispersed to South America during the Paleocene-Eocene Thermal Maximum (56 Ma). They also raise the possibility that at least three Amherstieae genera (Crudia, Berlinia, and Anthonotha) may have diverged earlier in the Cenozoic than predicted by molecular phylogenies.
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Airyscan superresolution microscopy: A high-throughput alternative to electron microscopy for the visualization and analysis of Fossil Pollen
Review of Palaeobotany and Palynology, 2020Co-Authors: Ingrid Romero, Michael A. Urban, Surangi W. PunyasenaAbstract:Abstract Airyscan confocal superresolution microscopy is a new optical technique that can detect morphological features smaller than the diffraction limit of light. It captures both the external and internal ornamentation of modern and Fossil Pollen. Airyscan combines the ease of use of optical microscopy methods, such as confocal and brightfield microscopy (BM), with the high-resolution imaging of electron microscopy (EM). Modern and Fossil Pollen grains were imaged using Airyscan, BM, and EM to assess the viability of Airyscan as an alternative for EM. Our results demonstrate that: (1) Airyscan can capture diagnostic features of extant and Fossil Pollen similar to EM; (2) one-to-one comparisons of Airyscan images with other optical methods are possible (e.g., BM and conventional confocal); (3) Airyscan captures three-dimensional data, allowing reconstruction of Pollen grains in different views; and (4) the time and effort required for Airyscan imaging is significantly less than that for EM. This paper demonstrates that Airyscan superresolution microscopy is a high-throughput alternative for morphological analyses of Pollen specimens.