TY - JOUR
A1 - Radosavljevic, Boris
A1 - Lantuit, Hugues
A1 - Knoblauch, Christian
A1 - Couture, Nicole
A1 - Herzschuh, Ulrike
A1 - Fritz, Michael
T1 - Arctic nearshore sediment dynamics - an example from Herschel Island - Qikiqtaruk, Canada
JF - Journal of marine science and engineering
N2 - Increasing arctic coastal erosion rates imply a greater release of sediments and organic matter into the coastal zone. With 213 sediment samples taken around Herschel Island-Qikiqtaruk, Canadian Beaufort Sea, we aimed to gain new insights on sediment dynamics and geochemical properties of a shallow arctic nearshore zone. Spatial characteristics of nearshore sediment texture (moderately to poorly sorted silt) are dictated by hydrodynamic processes, but ice-related processes also play a role. We determined organic matter (OM) distribution and inferred the origin and quality of organic carbon by C/N ratios and stable carbon isotopes delta C-13. The carbon content was higher offshore and in sheltered areas (mean: 1.0 wt.%., S.D.: 0.9) and the C/N ratios also showed a similar spatial pattern (mean: 11.1, S.D.: 3.1), while the delta C-13 (mean: -26.4 parts per thousand VPDB, S.D.: 0.4) distribution was more complex. We compared the geochemical parameters of our study with terrestrial and marine samples from other studies using a bootstrap approach. Sediments of the current study contained 6.5 times and 1.8 times less total organic carbon than undisturbed and disturbed terrestrial sediments, respectively. Therefore, degradation of OM and separation of carbon pools take place on land and continue in the nearshore zone, where OM is leached, mineralized, or transported beyond the study area.
KW - permafrost
KW - Arctic Ocean
KW - stable carbon isotopes
KW - nitrogen
KW - sediment
KW - chemistry
KW - sediment dynamics
KW - Beaufort Sea
KW - grain size
Y1 - 2022
U6 - https://doi.org/10.3390/jmse10111589
SN - 2077-1312
VL - 10
IS - 11
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Hébert, Raphaël
A1 - Herzschuh, Ulrike
A1 - Laepple, Thomas
T1 - Millennial-scale climate variability over land overprinted by ocean temperature fluctuations
JF - Nature geoscience
N2 - Variations in regional temperature have widespread implications for society, but our understanding of the amplitude and origin of long-term natural variability is insufficient for accurate regional projections. This is especially the case for terrestrial temperature variability, which is currently thought to be weak over long timescales. By performing spectral analysis on climate reconstructions, produced using sedimentary pollen records from the Northern Hemisphere over the last 8,000 years, coupled with instrumental data, we provide a comprehensive estimate of regional temperature variability from annual to millennial timescales. We show that short-term random variations are overprinted by strong ocean-driven climate variability on multi-decadal and longer timescales. This may cause substantial and potentially unpredictable regional climatic shifts in the coming century, in contrast to the relatively muted and homogeneous warming projected by climate models. Due to the marine influence, regions characterized by stable oceanic climate at sub-decadal timescales experience stronger long-term variability, and continental regions with higher sub-decadal variability show weaker long-term variability. This fundamental relationship between the timescales provides a unique insight into the emergence of a marine-driven low-frequency regime governing terrestrial climate variability and sets the basis to project the amplitude of temperature fluctuations on multi-decadal timescales and longer.
Temperature variability over land is enhanced by ocean temperature fluctuations on millennial timescales, with implications for regional-scale climate change, according to an analysis of Northern Hemisphere proxy records and observations.
Y1 - 2022
U6 - https://doi.org/10.1038/s41561-022-01056-4
SN - 1752-0894
SN - 1752-0908
VL - 15
IS - 11
SP - 899
PB - Nature portfolio
CY - Berlin
ER -
TY - JOUR
A1 - Dallmeyer, Anne
A1 - Kleinen, Thomas
A1 - Claussen, Martin
A1 - Weitzel, Nils
A1 - Cao, Xianyong
A1 - Herzschuh, Ulrike
T1 - The deglacial forest conundrum
JF - Nature Communications
N2 - How fast the Northern Hemisphere (NH) forest biome tracks strongly warming climates is largely unknown. Regional studies reveal lags between decades and millennia. Here we report a conundrum: Deglacial forest expansion in the NH extra-tropics occurs approximately 4000 years earlier in a transient MPI-ESM1.2 simulation than shown by pollen-based biome reconstructions. Shortcomings in the model and the reconstructions could both contribute to this mismatch, leaving the underlying causes unresolved. The simulated vegetation responds within decades to simulated climate changes, which agree with pollen-independent reconstructions. Thus, we can exclude climate biases as main driver for differences. Instead, the mismatch points at a multi-millennial disequilibrium of the NH forest biome to the climate signal. Therefore, the evaluation of time-slice simulations in strongly changing climates with pollen records should be critically reassessed. Our results imply that NH forests may be responding much slower to ongoing climate changes than Earth System Models predict.
Deglacial forest expansion in the Northern Hemisphere poses a conundrum: Model results agree with the climate signal but are several millennia ahead of reconstructed forest dynamics. The underlying causes remain unsolved.
Y1 - 2022
U6 - https://doi.org/10.1038/s41467-022-33646-6
SN - 2041-1723
VL - 13
IS - 1
PB - Nature Publishing Group UK
CY - [London]
ER -
TY - JOUR
A1 - Li, Zhen
A1 - Wang, Yongbo
A1 - Herzschuh, Ulrike
A1 - Cao, Xianyong
A1 - Ni, Jian
A1 - Zhao, Yan
T1 - Pollen-based biome reconstruction on the Qinghai-Tibetan Plateau during the past 15,000 years
JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences
N2 - Reconstruction of past vegetation change is critical for better understanding the potential impact of future global change on the fragile alpine ecosystems of the Qinghai-Tibetan Plateau (QTP). In this paper, pollen assemblages comprising 58 records from the QTP, spanning the past 15 kyrs, were collected to reconstruct biome compositions using a standard approach. Six forest biomes were identified mainly on the southeastern plateau, exhibiting a pattern of gradual expansion along the eastern margin during early to mid-Holocene times. The alpine meadow biome was separately identified based on an updated scheme, and showed notable westward expansions towards lower latitudes and higher altitudes during early Holocene times. Consistent patterns of migration could also be identified for the alpine steppe biome, which moved eastward during the late Holocene after 4 ka. As the dominant biome type, temperate steppe was distributed widely over the QTP with minor migration patterns, except for a progressive expansion to lower altitudes in the late Holocene times. The desert biome was inferred mainly as covering the northwestern plateau and the Qaidam Basin, in relatively restricted areas. The spatial distribution of the reconstructed biomes represent the large-scale vegetation gradient on the QTP. Monsoonal precipitation expressed predominant controls on the development of alpine ecosystems, while the variations in desert vegetation responded to regional moisture brought by the mid-latitude Westerlies. Temperature changes played relatively minor roles in the variations of alpine vegetation, but exerted more significant impacts on the forest biomes.
KW - biomization
KW - pollen
KW - vegetation migration
KW - Qinghai-Tibetan Plateau
KW - holocene
Y1 - 2022
U6 - https://doi.org/10.1016/j.palaeo.2022.111190
SN - 0031-0182
SN - 1872-616X
VL - 604
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - Herzschuh, Ulrike
A1 - Böhmer, Thomas
A1 - Li, Chenzhi
A1 - Cao, Xianyong
A1 - Hébert, Raphaël
A1 - Dallmeyer, Anne
A1 - Telford, Richard J.
A1 - Kruse, Stefan
T1 - Reversals in temperature-precipitation correlations in the Northern Hemisphere extratropics during the Holocene
JF - Geophysical research letters
N2 - Future precipitation levels remain uncertain because climate models have struggled to reproduce observed variations in temperature-precipitation correlations. Our analyses of Holocene proxy-based temperature-precipitation correlations and hydrological sensitivities from 2,237 Northern Hemisphere extratropical pollen records reveal a significant latitudinal dependence and temporal variations among the early, middle, and late Holocene. These proxy-based variations are largely consistent with patterns obtained from transient climate simulations (TraCE21k). While high latitudes and subtropical monsoon areas show mainly stable positive correlations throughout the Holocene, the mid-latitude pattern is temporally and spatially more variable. In particular, we identified a reversal from positive to negative temperature-precipitation correlations in the eastern North American and European mid-latitudes from the early to mid-Holocene that mainly related to slowed down westerlies and a switch to moisture-limited convection under a warm climate. Our palaeoevidence of past temperature-precipitation correlation shifts identifies those regions where simulating past and future precipitation levels might be particularly challenging.
Y1 - 2022
U6 - https://doi.org/10.1029/2022GL099730
SN - 0094-8276
SN - 1944-8007
VL - 49
IS - 22
PB - American Geophysical Union
CY - Washington
ER -
TY - JOUR
A1 - Schulte, Luise
A1 - Li, Chenzhi
A1 - Lisovski, Simeon
A1 - Herzschuh, Ulrike
T1 - Forest-permafrost feedbacks and glacial refugia help explain the unequal distribution of larch across continents
JF - Journal of biogeography
N2 - Aim: The continental-scale distribution of plant functional types, such as evergreen and summergreen needle-leaf forest, is assumed to be determined by contemporary climate. However, the distribution of summergreen needle-leaf forest of larch (Larix Mill.) differs markedly between the continents, despite relatively similar climatic conditions. The reasons for these differences are little understood. Our aim is to identify potential triggers and drivers of the current distribution patterns by comparing species' bioclimatic niches, glacial refugia and postglacial recolonization patterns.
Location: Northern hemisphere.
Taxon: Species of the genus Larix (Mill.).
Methods: We compare species distribution and dominance using species ranges and sites of dominance, as well as their occurrence on modelled permafrost extent, and active layer thickness (ALT). We compare the bioclimatic niches and calculate the niche overlap between species, using the same data in addition to modern climate data. We synthesize pollen, macrofossil and ancient DNA palaeo-evidence of past Larix occurrences of the last 60,000 years and track differences in distribution patterns through time.
Results: Bioclimatic niches show large overlaps between Asian larch species and American Larix laricina. The distribution across various degrees of permafrost extent is distinctly different for Asian L. gmelinii and L. cajanderi compared to the other species, whereas the distribution on different depths of ALT is more similar among Asian and American species. Northern glacial refugia for Larix are only present in eastern Asia and Alaska.
Main Conclusion: The dominance of summergreen larches in Asia, where evergreen conifers dominate most of the rest of the boreal forests, is dependent on the interaction of several factors which allows Asian L. gmelinii and L. cajanderi to dominate where these factors coincide. These factors include the early postglacial spread out of northern glacial refugia in the absence of competitors as well as a positive feedback mechanism between frozen ground and forest.
KW - bioclimatic niche
KW - glacial refugia
KW - larch
KW - Larix
KW - permafrost
KW - phylogeography
KW - postglacial recolonization
Y1 - 2022
U6 - https://doi.org/10.1111/jbi.14456
SN - 0305-0270
SN - 1365-2699
VL - 49
IS - 10
SP - 1825
EP - 1838
PB - Wiley
CY - Hoboken
ER -
TY - JOUR
A1 - Kruse, Stefan
A1 - Herzschuh, Ulrike
T1 - Regional opportunities for tundra conservation in the next 1000 years
JF - eLife
N2 - The biodiversity of tundra areas in northern high latitudes is threatened by invasion of forests under global warming. However, poorly understood nonlinear responses of the treeline ecotone mean the timing and extent of tundra losses are unclear, but policymakers need such information to optimize conservation efforts. Our individual-based model LAVESI, developed for the Siberian tundra-taiga ecotone, can help improve our understanding. Consequently, we simulated treeline migration trajectories until the end of the millennium, causing a loss of tundra area when advancing north. Our simulations reveal that the treeline follows climate warming with a severe, century-long time lag, which is overcompensated by infilling of stands in the long run even when temperatures cool again. Our simulations reveal that only under ambitious mitigation strategies (relative concentration pathway 2.6) will ~30% of original tundra areas remain in the north but separated into two disjunct refugia.
KW - Larix gmelinii
KW - Larix cajanderi
KW - nonlinear response
KW - treeline ecotone
KW - tundra
KW - Ecology
KW - Short Report
Y1 - 2022
U6 - https://doi.org/10.7554/eLife.75163
SN - 2050-084X
VL - 11
PB - eLife Sciences Publications
CY - Cambridge
ER -
TY - JOUR
A1 - van Geffen, Femke
A1 - Heim, Birgit
A1 - Brieger, Frederic
A1 - Geng, Rongwei
A1 - Shevtsova, Iuliia A.
A1 - Schulte, Luise
A1 - Stuenzi, Simone M.
A1 - Bernhardt, Nadine
A1 - Troeva, Elena
A1 - Pestryakova, Luidmila A.
A1 - Zakharov, Evgenii S.
A1 - Pflug, Bringfried
A1 - Herzschuh, Ulrike
A1 - Kruse, Stefan
T1 - SiDroForest: a comprehensive forest inventory of Siberian boreal forest investigations including drone-based point clouds, individually labeled trees, synthetically generated tree crowns, and Sentinel-2 labeled image patches
JF - Earth system science data
N2 - The SiDroForest (Siberian drone-mapped forest inventory) data collection is an attempt to remedy the scarcity of forest structure data in the circumboreal region by providing adjusted and labeled tree-level and vegetation plot-level data for machine learning and upscaling purposes. We present datasets of vegetation composition and tree and plot level forest structure for two important vegetation transition zones in Siberia, Russia; the summergreen-evergreen transition zone in Central Yakutia and the tundra-taiga transition zone in Chukotka (NE Siberia). The SiDroForest data collection consists of four datasets that contain different complementary data types that together support in-depth analyses from different perspectives of Siberian Forest plot data for multi-purpose applications. i. Dataset 1 provides unmanned aerial vehicle (UAV)-borne data products covering the vegetation plots surveyed during fieldwork (Kruse et al., 2021, ). The dataset includes structure-from-motion (SfM) point clouds and red-green-blue (RGB) and red-green-near-infrared (RGN) orthomosaics. From the orthomosaics, point-cloud products were created such as the digital elevation model (DEM), canopy height model (CHM), digital surface model (DSM) and the digital terrain model (DTM). The point-cloud products provide information on the three-dimensional (3D) structure of the forest at each plot. Dataset 2 contains spatial data in the form of point and polygon shapefiles of 872 individually labeled trees and shrubs that were recorded during fieldwork at the same vegetation plots (van Geffen et al., 2021c, ). The dataset contains information on tree height, crown diameter, and species type. These tree and shrub individually labeled point and polygon shapefiles were generated on top of the RGB UVA orthoimages. The individual tree information collected during the expedition such as tree height, crown diameter, and vitality are provided in table format. This dataset can be used to link individual information on trees to the location of the specific tree in the SfM point clouds, providing for example, opportunity to validate the extracted tree height from the first dataset. The dataset provides unique insights into the current state of individual trees and shrubs and allows for monitoring the effects of climate change on these individuals in the future. Dataset 3 contains a synthesis of 10 000 generated images and masks that have the tree crowns of two species of larch ( and ) automatically extracted from the RGB UAV images in the common objects in context (COCO) format (van Geffen et al., 2021a, ). As machine-learning algorithms need a large dataset to train on, the synthetic dataset was specifically created to be used for machine-learning algorithms to detect Siberian larch species. Larix gmeliniiLarix cajanderiDataset 4 contains Sentinel-2 (S-2) Level-2 bottom-of-atmosphere processed labeled image patches with seasonal information and annotated vegetation categories covering the vegetation plots (van Geffen et al., 2021b, ). The dataset is created with the aim of providing a small ready-to-use validation and training dataset to be used in various vegetation-related machine-learning tasks. It enhances the data collection as it allows classification of a larger area with the provided vegetation classes. The SiDroForest data collection serves a variety of user communities.
The detailed vegetation cover and structure information in the first two datasets are of use for ecological applications, on one hand for summergreen and evergreen needle-leaf forests and also for tundra-taiga ecotones. Datasets 1 and 2 further support the generation and validation of land cover remote-sensing products in radar and optical remote sensing. In addition to providing information on forest structure and vegetation composition of the vegetation plots, the third and fourth datasets are prepared as training and validation data for machine-learning purposes. For example, the synthetic tree-crown dataset is generated from the raw UAV images and optimized to be used in neural networks. Furthermore, the fourth SiDroForest dataset contains S-2 labeled image patches processed to a high standard that provide training data on vegetation class categories for machine-learning classification with JavaScript Object Notation (JSON) labels provided. The SiDroForest data collection adds unique insights into remote hard-to-reach circumboreal forest regions.
Y1 - 2022
U6 - https://doi.org/10.5194/essd-14-4967-2022
SN - 1866-3508
SN - 1866-3516
VL - 14
IS - 11
SP - 4967
EP - 4994
PB - Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Jia, Weihan
A1 - Anslan, Sten
A1 - Chen, Fahu
A1 - Cao, Xianyong
A1 - Dong, Hailiang
A1 - Dulias, Katharina
A1 - Gu, Zhengquan
A1 - Heinecke, Liv
A1 - Jiang, Hongchen
A1 - Kruse, Stefan
A1 - Kang, Wengang
A1 - Li, Kai
A1 - Liu, Sisi
A1 - Liu, Xingqi
A1 - Liu, Ying
A1 - Ni, Jian
A1 - Schwalb, Antje
A1 - Stoof-Leichsenring, Kathleen R.
A1 - Shen, Wei
A1 - Tian, Fang
A1 - Wang, Jing
A1 - Wang, Yongbo
A1 - Wang, Yucheng
A1 - Xu, Hai
A1 - Yang, Xiaoyan
A1 - Zhang, Dongju
A1 - Herzschuh, Ulrike
T1 - Sedimentary ancient DNA reveals past ecosystem and biodiversity changes on the Tibetan Plateau: overview and prospects
JF - Quaternary science reviews : the international multidisciplinary research and review journal
N2 - Alpine ecosystems on the Tibetan Plateau are being threatened by ongoing climate warming and intensified human activities. Ecological time-series obtained from sedimentary ancient DNA (sedaDNA) are essential for understanding past ecosystem and biodiversity dynamics on the Tibetan Plateau and their responses to climate change at a high taxonomic resolution. Hitherto only few but promising studies have been published on this topic. The potential and limitations of using sedaDNA on the Tibetan Plateau are not fully understood. Here, we (i) provide updated knowledge of and a brief introduction to the suitable archives, region-specific taphonomy, state-of-the-art methodologies, and research questions of sedaDNA on the Tibetan Plateau; (ii) review published and ongoing sedaDNA studies from the Tibetan Plateau; and (iii) give some recommendations for future sedaDNA study designs. Based on the current knowledge of taphonomy, we infer that deep glacial lakes with freshwater and high clay sediment input, such as those from the southern and southeastern Tibetan Plateau, may have a high potential for sedaDNA studies. Metabarcoding (for microorganisms and plants), metagenomics (for ecosystems), and hybridization capture (for prehistoric humans) are three primary sedaDNA approaches which have been successfully applied on the Tibetan Plateau, but their power is still limited by several technical issues, such as PCR bias and incompleteness of taxonomic reference databases. Setting up high-quality and open-access regional taxonomic reference databases for the Tibetan Plateau should be given priority in the future. To conclude, the archival, taphonomic, and methodological conditions of the Tibetan Plateau are favorable for performing sedaDNA studies. More research should be encouraged to address questions about long-term ecological dynamics at ecosystem scale and to bring the paleoecology of the Tibetan Plateau into a new era.
KW - Sedimentary ancient DNA (sedaDNA)
KW - Tibetan Plateau
KW - Environmental DNA
KW - Taphonomy
KW - Ecosystem
KW - Biodiversity
KW - Paleoecology
KW - Paleogeography
Y1 - 2022
U6 - https://doi.org/10.1016/j.quascirev.2022.107703
SN - 0277-3791
SN - 1873-457X
VL - 293
PB - Elsevier
CY - Oxford
ER -
TY - JOUR
A1 - Li, Chenzhi
A1 - Postl, Alexander K.
A1 - Böhmer, Thomas
A1 - Cao, Xianyong
A1 - Dolman, Andrew M.
A1 - Herzschuh, Ulrike
T1 - Harmonized chronologies of a global late Quaternary pollen dataset (LegacyAge 1.0)
JF - Earth system science data : ESSD
N2 - 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.
Y1 - 2022
U6 - https://doi.org/10.5194/essd-14-1331-2022
SN - 1866-3508
SN - 1866-3516
VL - 14
IS - 3
SP - 1331
EP - 1343
PB - Copernics Publications
CY - Katlenburg-Lindau
ER -