@article{CaoNiHerzschuhetal.2013, author = {Cao, Xianyong and Ni, Jian and Herzschuh, Ulrike and Wang, Yongbo and Zhao, Yan}, title = {A late quaternary pollen dataset from eastern continental Asia for vegetation and climate reconstructions set up and evaluation}, series = {Review of palaeobotany and palynology : an international journal}, volume = {194}, journal = {Review of palaeobotany and palynology : an international journal}, number = {13}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0034-6667}, doi = {10.1016/j.revpalbo.2013.02.003}, pages = {21 -- 37}, year = {2013}, abstract = {A total of 271 pollen records were selected from a large collection of both raw and digitized pollen spectra from eastern continental Asia (70 degrees-135 degrees E and 18 degrees-55 degrees N). Following pollen percentage recalculations, taxonomic homogenization, and age-depth model revision, the pollen spectra were interpolated at a 500-year resolution and a taxonomically harmonized and temporally standardized fossil pollen dataset established with 226 pollen taxa, covering the last 22 cal lea. Of the 271 pollen records, 85\% were published since 1990, with reliable chronologies and high temporal resolutions; of these, 50\% have raw data with complete pollen assemblages, ensuring the quality of this dataset The pollen records available for each 500-year time slice are well distributed over all main vegetation types and climatic zones of the study area, making their pollen spectra suitable for paleovegetation and paleoclimate research. Such a dataset can be used as an example for the development of similar datasets for other regions of the world.}, language = {en} } @article{CaoHerzschuhTelfordetal.2014, author = {Cao, Xianyong and Herzschuh, Ulrike and Telford, Richard J. and Ni, Jian}, title = {A modern pollen-climate dataset from China and Mongolia: assessing its potential for climate reconstruction}, series = {Review of palaeobotany and palynology : an international journal}, volume = {211}, journal = {Review of palaeobotany and palynology : an international journal}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0034-6667}, doi = {10.1016/j.revpalbo.2014.08.007}, pages = {87 -- 96}, year = {2014}, abstract = {A modern pollen dataset from China and Mongolia (18-52 degrees N, 74-132 degrees E) is investigated for its potential use in climate reconstructions. The dataset includes 2559 samples, 229 terrestrial pollen taxa and four climatic variables - mean annual precipitation (P-ann): 35-2091 mm, mean annual temperature (T-ann): -12.1-25.8 degrees C, mean temperature in the coldest month (Mt(co).): -33.8-21.7 degrees C, and mean temperature in the warmest month (Mt(wa)): 03-29.8 degrees C. Modern pollen-climate relationships are assessed using canonical correspondence analysis (CCA), Huisman-Olff-Fresco (HOF) models, the modern analogue technique (MAT), and weighted averaging partial least squares (WA-PLS). Results indicate that P-ann is the most important climatic determinant of pollen distribution and the most promising climate variable for reconstructions, as assessed by the coefficient of determination between observed and predicted environmental values (r(2)) and root mean square error of prediction (RMSEP). Mt(co) and Mt(wa) may be reconstructed too, but with caution. Samples from different depositional environments influence the performance of cross-validation differently, with samples from lake sediment-surfaces and moss polsters having the best fit with the lowest RMSEP. The better model performances of MAT are most probably caused by spatial autocorrelation. Accordingly, the WA-PLS models of this dataset are deemed most suitable for reconstructing past climate quantitatively because of their more reliable predictive power. (C) 2014 Elsevier B.V. All rights reserved.}, language = {en} } @article{CaoTianAndreevetal.2020, author = {Cao, Xianyong and Tian, Fang and Andreev, Andrei and Anderson, Patricia M. and Lozhkin, Anatoly V. and Bezrukova, Elena and Ni, Jian and Rudaya, Natalia and Stobbe, Astrid and Wieczorek, Mareike and Herzschuh, Ulrike}, title = {A taxonomically harmonized and temporally standardized fossil pollen dataset from Siberia covering the last 40 kyr}, series = {Earth System Science Data}, volume = {12}, journal = {Earth System Science Data}, number = {1}, publisher = {Copernics Publications}, address = {Katlenburg-Lindau}, issn = {1866-3508}, doi = {10.5194/essd-12-119-2020}, pages = {119 -- 135}, year = {2020}, abstract = {Pollen records from Siberia are mostly absent in global or Northern Hemisphere synthesis works. Here we present a taxonomically harmonized and temporally standardized pollen dataset that was synthesized using 173 palynological records from Siberia and adjacent areas (northeastern Asia, 42-75 degrees N, 50-180 degrees E). Pollen data were taxonomically harmonized, i.e. the original 437 taxa were assigned to 106 combined pollen taxa. Age-depth models for all records were revised by applying a constant Bayesian age-depth modelling routine. The pollen dataset is available as count data and percentage data in a table format (taxa vs. samples), with age information for each sample. The dataset has relatively few sites covering the last glacial period between 40 and 11.5 ka (calibrated thousands of years before 1950 CE) particularly from the central and western part of the study area. In the Holocene period, the dataset has many sites from most of the area, with the exception of the central part of Siberia. Of the 173 pollen records, 81 \% of pollen counts were downloaded from open databases (GPD, EPD, PANGAEA) and 10 \% were contributions by the original data gatherers, while a few were digitized from publications. Most of the pollen records originate from peatlands (48 \%) and lake sediments (33 \%). Most of the records (83 \%) have >= 3 dates, allowing the establishment of reliable chronologies. The dataset can be used for various purposes, including pollen data mapping (example maps for Larix at selected time slices are shown) as well as quantitative climate and vegetation reconstructions. The datasets for pollen counts and pollen percentages are available at https://doi.org/10.1594/PANGAEA.898616 (Cao et al., 2019a), also including the site information, data source, original publication, dating data, and the plant functional type for each pollen taxa.}, language = {en} } @article{KoenigZhenHelmingetal.2014, author = {Koenig, H. J. and Zhen, L. and Helming, K. and Uthes, S. and Yang, L. and Cao, Xianyong and Wiggering, Hubert}, title = {Assessing the impact of the sloping land conversion programme on rural sustainability in Guyuan, Western China}, series = {Land degradation \& development}, volume = {25}, journal = {Land degradation \& development}, number = {4}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1085-3278}, doi = {10.1002/ldr.2164}, pages = {385 -- 396}, year = {2014}, abstract = {The goal of China's sloping land conversion programme (SLCP) is to combat soil erosion and to reduce rural poverty. An ex-ante assessment of possible SLCP impacts was conducted with a focus on rural sustainability, taking the drought-prone region of Guyuan in Western China as an example. The Framework for Participatory Impact Assessment (FoPIA) was used to conduct two complementary impact assessments, one assessing SLCP impacts at regional level and a second one assessing alternative forest management options, to explore possible trade-offs among the economic, social and environmental dimensions of sustainability. Regional stakeholders assessed the SLCP to be capable of reducing soil erosion but felt it negatively affected rural employment, and a further continuation of the Programme was advocated. Assessment of three forest management scenarios by scientists showed that an orientation towards energy forests is potentially beneficial to all three sustainability dimensions. Ecological forests had disproportionate positive impacts on environmental functions and adverse impact on the other two sustainability dimensions. Economic forests were assessed to serve primarily the economic and social sustainability dimensions, while environmental impacts were still tolerable. The FoPIA results were evaluated against the available literature on the SLCP. Overall, the assessment results appeared to be reasonable, but the results of the regional stakeholders appeared to be too optimistic compared with the more critical assessment of the scientists. The SLCP seems to have the potential to tackle soil erosion but requires integrated forest management to minimize the risk of water stress while contributing to economic and social benefits in Guyuan. Copyright (C) 2012 John Wiley \& Sons, Ltd.}, language = {en} } @article{TianCaoDallmeyeretal.2018, author = {Tian, Fang and Cao, Xianyong and Dallmeyer, Anne and Lohmann, Gerrit and Zhang, Xu and Ni, Jian and Andreev, Andrei and Anderson, Patricia M. and Lozhkin, Anatoly V. and Bezrukova, Elena and Rudaya, Natalia and Xu, Qinghai and Herzschuh, Ulrike}, title = {Biome changes and their inferred climatic drivers in northern and eastern continental Asia at selected times since 40 cal ka BP}, series = {Vegetation History and Archaeobotany}, volume = {27}, journal = {Vegetation History and Archaeobotany}, number = {2}, publisher = {Springer}, address = {New York}, issn = {0939-6314}, doi = {10.1007/s00334-017-0653-8}, pages = {365 -- 379}, year = {2018}, abstract = {Recent global warming is pronounced in high-latitude regions (e.g. northern Asia), and will cause the vegetation to change. Future vegetation trends (e.g. the "arctic greening") will feed back into atmospheric circulation and the global climate system. Understanding the nature and causes of past vegetation changes is important for predicting the composition and distribution of future vegetation communities. Fossil pollen records from 468 sites in northern and eastern Asia were biomised at selected times between 40 cal ka bp and today. Biomes were also simulated using a climate-driven biome model and results from the two approaches compared in order to help understand the mechanisms behind the observed vegetation changes. The consistent biome results inferred by both approaches reveal that long-term and broad-scale vegetation patterns reflect global- to hemispheric-scale climate changes. Forest biomes increase around the beginning of the late deglaciation, become more widespread during the early and middle Holocene, and decrease in the late Holocene in fringe areas of the Asian Summer Monsoon. At the southern and southwestern margins of the taiga, forest increases in the early Holocene and shows notable species succession, which may have been caused by winter warming at ca. 7 cal ka bp. At the northeastern taiga margin (central Yakutia and northeastern Siberia), shrub expansion during the last deglaciation appears to prevent the permafrost from thawing and hinders the northward expansion of evergreen needle-leaved species until ca. 7 cal ka bp. The vegetation-climate disequilibrium during the early Holocene in the taiga-tundra transition zone suggests that projected climate warming will not cause a northward expansion of evergreen needle-leaved species.}, language = {en} } @article{DallmeyerClaussenNietal.2017, author = {Dallmeyer, Anne and Claussen, Martin and Ni, Jian and Cao, Xianyong and Wang, Yongbo and Fischer, Nils and Pfeiffer, Madlene and Jin, Liya and Khon, Vyacheslav and Wagner, Sebastian and Haberkorn, Kerstin and Herzschuh, Ulrike}, title = {Biome changes in Asia since the mid-Holocene}, series = {Climate of the past : an interactive open access journal of the European Geosciences Union}, volume = {13}, journal = {Climate of the past : an interactive open access journal of the European Geosciences Union}, number = {2}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1814-9324}, doi = {10.5194/cp-13-107-2017}, pages = {107 -- 134}, year = {2017}, abstract = {The large variety of atmospheric circulation systems affecting the eastern Asian climate is reflected by the complex Asian vegetation distribution. Particularly in the transition zones of these circulation systems, vegetation is supposed to be very sensitive to climate change. Since proxy records are scarce, hitherto a mechanistic understanding of the past spatio-temporal climate-vegetation relationship is lacking. To assess the Holocene vegetation change and to obtain an ensemble of potential mid-Holocene biome distributions for eastern Asia, we forced the diagnostic biome model BIOME4 with climate anomalies of different transient Holocene climate simulations performed in coupled atmosphere-ocean(-vegetation) models. The simulated biome changes are compared with pollen-based biome records for different key regions. In all simulations, substantial biome shifts during the last 6000 years are confined to the high northern latitudes and the monsoon-westerly wind transition zone, but the temporal evolution and amplitude of change strongly depend on the climate forcing. Large parts of the southern tundra are replaced by taiga during the mid-Holocene due to a warmer growing season and the boreal treeline in northern Asia is shifted northward by approx. 4 degrees in the ensemble mean, ranging from 1.5 to 6 degrees in the individual simulations, respectively. This simulated treeline shift is in agreement with pollen-based reconstructions from northern Siberia. The desert fraction in the transition zone is reduced by 21\% during the mid-Holocene compared to pre-industrial due to enhanced precipitation. The desert-steppe margin is shifted westward by 5 degrees (1-9 degrees in the individual simulations). The forest biomes are expanded north-westward by 2 degrees, ranging from 0 to 4 degrees in the single simulations. These results corroborate pollen-based reconstructions indicating an extended forest area in north-central China during the mid-Holocene. According to the model, the forest-to-non-forest and steppe-to-desert changes in the climate transition zones are spatially not uniform and not linear since the mid-Holocene.}, language = {en} } @article{NiCaoJeltschetal.2014, author = {Ni, Jian and Cao, Xianyong and Jeltsch, Florian and Herzschuh, Ulrike}, title = {Biome distribution over the last 22,000 yr in China}, series = {Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences}, volume = {409}, journal = {Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0031-0182}, doi = {10.1016/j.palaeo.2014.04.023}, pages = {33 -- 47}, year = {2014}, abstract = {Patterns of past vegetation changes over time and space can help facilitate better understanding of the interactions among climate, ecosystem, and human impact. Biome changes in China over the last 22,000 yr (calibrated radiocarbon date, a BP) were numerically reconstructed by using a standard approach of pollen-plant functional type-biome assignment (biomization). The biomization procedure involves pollen data from 2434 surface sites and 228 fossil sites with a high quality of pollen count and C-14 dating, 51 natural and three anthropogenic plant functional types (PFTs), as well as 19 natural and one anthropogenic biome. Surface pollen-based reconstruction of modern natural biome patterns is in good agreement (74.4\%) with actual vegetation distribution in China. However, modem large-scale anthropogenic biome reconstruction has not been successful based on the current setup of three anthropogenic PFTs (plantation, secondary, and disturbed PFT) because of the limitation of non-species level pollen identification and the difficulty in the clear assignment of disturbed PFTs. The non-anthropogenic biome distributions of 44 time slices at 500-year intervals show large-scale discrepant and changed vegetation patterns from the last glacial maximum (LGM) to the Holocene throughout China. From 22 ka BP to 19 ka BP, temperate grassland, xerophytic shrubland, and desert dominated northern China, whereas cold or cool forests flourished in central China. Warm-temperate evergreen forests were restricted to far southern China, and tropical forests were absent During 18.5 ka BP to 12 ka BP, cold, cool, and dry biomes extended to some parts of northern, westem, and eastern China. Warm-temperate evergreen and mixed forests gradually expanded to occupy the whole of southern China. A slight northward shift of forest biomes occurred from 15 ka BP to 12 lea BP. During 11.5 ka BP to 9 ka BP, temperate grassland and shrubland gradually stretched to northern and western China. Cold and cool forests widely expanded into northern and central China, as well as in the northern margin of South China along with temperate deciduous forest. Since the early mid-Holocene (approximately 8.5 ka BP to 5.5 ka BP), all forest biomes shifted northward at the expense of herbaceous and shrubby biomes. Simultaneously, cold and cool forest biomes occupied the marginal areas of the Tibetan Plateau and the high mountains in western China. During the middle to late Holocene, from 5 ka to the present, temperate grassland and xerophytic shrubland expanded to the south and east, whereas temperate deciduous forests slightly shifted southward. After 3 lea BP, forest biomes were absent in western China and on the Tibetan plateau surface. Dramatic biome shifts from the LGM to the Holocene were observed in the forest-grassland ecotone and transitional zones between temperate and subtropical climates, between subtropical and tropical regions, and in the mountainous margins of the eastern Tibetan Plateau. Evidence showed more human disturbances during the late Holocene. More pollen records and historical documents are therefore further needed to understand fully the human disturbance-induced large-scale forest changes. In addition, more classifications of anthropogenic biome or land cover, more distinct assignment of pollen taxa to anthropogenic PFTs, and more effective numerical and/or mechanistic techniques in building large-scale human disturbances are required. (C) 2014 Elsevier B.V. All rights reserved.}, language = {en} } @article{ZhangXuGaillardetal.2016, author = {Zhang, Shengrui and Xu, Qinghai and Gaillard, Marie-Jose and Cao, Xianyong and Li, Jianyong and Zhang, Liyan and Li, Yuecong and Tian, Fang and Zhou, Liping and Lin, Fengyou and Yang, Xiaolan}, title = {Characteristic pollen source area and vertical pollen dispersal and deposition in a mixed coniferous and deciduous broad-leaved woodland in the Changbai mountains, northeast China}, series = {Vegetation History and Archaeobotany}, volume = {25}, journal = {Vegetation History and Archaeobotany}, publisher = {Springer}, address = {New York}, issn = {0939-6314}, doi = {10.1007/s00334-015-0532-0}, pages = {29 -- 43}, year = {2016}, abstract = {Pollen influx (number of pollen grains cm\&\#8722;2 year\&\#8722;1) can objectively reflect the dispersal and deposition features of pollen within a certain time and space, and is often used as a basis for the quantitative reconstruction of palaeovegetation; however, little is known about the features and mechanisms of vertical dispersal of pollen. Here we present the results from a 5 year (2006-2010) monitoring program using pollen traps placed at different heights from ground level up to 60 m and surface soil samples in a mixed coniferous and deciduous broad-leaved woodland in the Changbai mountains, northeastern China. The pollen percentages and pollen influx from the traps have very similar characteristics to the highest values for Betula, Fraxinus, Quercus and Pinus, among the tree taxa and Artemisia, Chenopodiaceae and Asteraceae among the herb taxa. Pollen influx values vary significantly with height and show major differences between three distinct layers, above-canopy (\&\#8805;32 m), within the trunk layer (8 \&\#8804; 32 m) and on the ground (0 m). These differences in pollen influx are explained by differences in (i) the air flows in each of these layers and (ii) the fall speed of pollen of the various taxa. We found that the pollen recorded on the ground surface is a good representation of the major part of the pollen transported in the trunk space of the woodland. Comparison of the pollen influx values with the theoretical, calculated "characteristic pollen source area" (CPSA) of 12 selected taxa indicates that the pollen deposited on the ground surface of the woodland is a fair representation with 85-90 \% of the total pollen deposited at a wind speed of 2.4 m s\&\#8722;1 coming from within ca. 1-5 km for Pinus and Quercus, ca. 5-10 km for Ulmus, Tilia, Oleaceae and Betula, ca. 20-40 km for Fraxinus, Poaceae, Chenopodiaceae, Populus and Salix, and ca. 30-60 km for Artemisia; it is also a good representation with 90-98 \% of the total pollen deposited coming from within 60 km at a wind speed of 2.4 m s\&\#8722;1, or 100 km at a wind speed: 6 m s\&\#8722;1, for the 12 selected taxa used in the CPSA calculation. Furthermore, comparison with the vegetation map of the area around the sampling site shows that the pollen deposited on the ground represents all plant communities which grow in the study area within 70 km radius of the sampling site. In this study, the pollen percentages obtained from the soil surface samples are significantly biased towards pollen taxa with good preservation due to thick and robust pollen walls. Therefore, if mosses are available instead, soil samples should be avoided for pollen studies, in particular for the study of pollen-vegetation relationships, the estimation of pollen productivities and quantitative reconstruction of past vegetation. The results also indicate that the existing model of pollen dispersal and deposition, Prentice's model, provides a fair description of the actual pollen dispersal and deposition in this kind of woodland, which suggests that the application of the landscape reconstruction algorithm would be relevant for reconstruction of this type of woodland in the past.}, language = {en} } @article{LiPostlBoehmeretal.2022, author = {Li, Chenzhi and Postl, Alexander K. and B{\"o}hmer, Thomas and Cao, Xianyong and Dolman, Andrew M. and Herzschuh, Ulrike}, title = {Harmonized chronologies of a global late Quaternary pollen dataset (LegacyAge 1.0)}, series = {Earth system science data : ESSD}, volume = {14}, journal = {Earth system science data : ESSD}, number = {3}, publisher = {Copernics Publications}, address = {Katlenburg-Lindau}, issn = {1866-3508}, doi = {10.5194/essd-14-1331-2022}, pages = {1331 -- 1343}, year = {2022}, abstract = {We present a chronology framework named LegacyAge 1.0 containing harmonized chronologies for 2831 pollen records (downloaded from the Neotoma Paleoecology Database and the supplementary Asian datasets) together with their age control points and metadata in machine-readable data formats. All chronologies use the Bayesian framework implemented in Bacon version 2.5.3. Optimal parameter settings of priors (accumulation.shape, memory.strength, memory.mean, accumulation.rate, and thickness) were identified based on information in the original publication or iteratively after preliminary model inspection. The most common control points for the chronologies are radiocarbon dates (86.1 \%), calibrated by the latest calibration curves (IntCal20 and SHCal20 for the terrestrial radiocarbon dates in the Northern Hemisphere and Southern Hemisphere and Marine20 for marine materials). The original publications were consulted when dealing with outliers and inconsistencies. Several major challenges when setting up the chronologies included the waterline issue (18.8\% of records), reservoir effect (4.9 \%), and sediment deposition discontinuity (4.4 \%). Finally, we numerically compare the LegacyAge 1.0 chronologies to those published in the original publications and show that the reliability of the chronologies of 95.4\% of records could be improved according to our assessment. Our chronology framework and revised chronologies provide the opportunity to make use of the ages and age uncertainties in synthesis studies of, for example, pollen-based vegetation and climate change. The LegacyAge 1.0 dataset, including metadata, datings, harmonized chronologies, and R code used, is openaccess and available at PANGAEA (https://doi.org/10.1594/PANGAEA.933132; Li et al., 2021) and Zenodo (https://doi.org/10.5281/zenodo.5815192; Li et al., 2022), respectively.}, language = {en} } @article{HuangPengRudayaetal.2018, author = {Huang, Xiaozhong and Peng, Wei and Rudaya, Natalia and Grimm, Eric C. and Chen, Xuemei and Cao, Xianyong and Zhang, Jun and Pan, Xiaoduo and Liu, Sisi and Chen, Chunzhu and Chen, Fahu}, title = {Holocene vegetation and climate dynamics in the Altai Mountains and Surrounding Areas}, series = {Geophysical research letters}, volume = {45}, journal = {Geophysical research letters}, number = {13}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1029/2018GL078028}, pages = {6628 -- 6636}, year = {2018}, abstract = {A comprehensive understanding of the regional vegetation responses to long-term climate change will help to forecast Earth system dynamics. Based on a new well-dated pollen data set from Kanas Lake and a review on the published pollen records in and around the Altai Mountains, the regional vegetation dynamics and forcing mechanisms are discussed. In the Altai Mountains, the forest optimum occurred during 10-7ka for the upper forest zone and the tree line decline and/or ecological shifts were caused by climatic cooling from around 7ka. In the lower forest zone, the forest reached an optimum in the middle Holocene, and then increased openness of the forest, possibly caused by both climate cooling and human activities, took place in the late Holocene. In the lower basins or plains around the Altai Mountains, the development of protograssland or forest benefited from increasing humidity in the middle to late Holocene. Plain Language Summary In the Altai Mountains and surrounding area of central Asia, the previous studies of the Holocene paleovegetation and paleoclimate studies did not discuss the different ecological limiting factors for the vegetation in high mountains and low-elevation areas due to limited data. With accumulating fossil pollen data and surface pollen data, it is possible to understand better the geomorphological effect on the vegetation and discrepancies of vegetation/forest responses to large-scale climate forcing, and it is also possible to get reliable quantitative reconstructions of climate. Here our new pollen data and review on the published fossil pollen data will help us to look into the past climate change and vertical evolution of vegetation in this important area of the Northern Hemisphere. Based on our study, it can be concluded that the growth of taiga forest in the wetter areas may be promoted under a future warmer climate, while the forest in the relatively dry areas is liable to decline, and the different vegetation dynamics will contribute to future high-resolution coupled vegetation-climate model for Earth system modelling.}, language = {en} }