TY - JOUR
A1 - Dietze, Elisabeth
A1 - Mangelsdorf, Kai
A1 - Andreev, Andrei
A1 - Karger, Cornelia
A1 - Schreuder, Laura T.
A1 - Hopmans, Ellen C.
A1 - Rach, Oliver
A1 - Sachse, Dirk
A1 - Wennrich, Volker
A1 - Herzschuh, Ulrike
T1 - Relationships between low-temperature fires, climate and vegetation during three late glacials and interglacials of the last 430 kyr in northeastern Siberia reconstructed from monosaccharide anhydrides in Lake El’gygytgyn sediments
JF - Climate of the Past
N2 - Landscapes in high northern latitudes are assumed to be highly sensitive to future global change, but the rates and long-term trajectories of changes are rather uncertain. In the boreal zone, fires are an important factor in climate-vegetation interactions and biogeochemical cycles. Fire regimes are characterized by small, frequent, low-intensity fires within summergreen boreal forests dominated by larch, whereas evergreen boreal forests dominated by spruce and pine burn large areas less frequently but at higher intensities. Here, we explore the potential of the monosaccharide anhydrides (MA) levoglucosan, mannosan and galactosan to serve as proxies of low-intensity biomass burning in glacial-to-interglacial lake sediments from the high northern latitudes. We use sediments from Lake El'gygytgyn (cores PG 1351 and ICDP 5011-1), located in the far north-east of Russia, and study glacial and interglacial samples of the last 430 kyr (marine isotope stages 5e, 6, 7e, 8, 11c and 12) that had different climate and biome configurations. Combined with pollen and non-pollen palynomorph records from the same samples, we assess how far the modern relationships between fire, climate and vegetation persisted during the past, on orbital to centennial timescales. We find that MAs attached to particulates were well-preserved in up to 430 kyr old sediments with higher influxes from low-intensity biomass burning in interglacials compared to glacials. MA influxes significantly increase when summergreen boreal forest spreads closer to the lake, whereas they decrease when tundra-steppe environments and, especially, Sphagnum peatlands spread. This suggests that low-temperature fires are a typical characteristic of Siberian larch forests also on long timescales. The results also suggest that low-intensity fires would be reduced by vegetation shifts towards very dry environments due to reduced biomass availability, as well as by shifts towards peatlands, which limits fuel dryness. In addition, we observed very low MA ratios, which we interpret as high contributions of galactosan and mannosan from biomass sources other than those currently monitored, such as the moss-lichen mats in the understorey of the summergreen boreal forest. Overall, sedimentary MAs can provide a powerful proxy for fire regime reconstructions and extend our knowledge of long-term natural fire-climate-vegetation feedbacks in the high northern latitudes.
KW - molecular tracers
KW - organic aerosols
KW - emission factors
KW - carbonaceous aerosols
KW - pollen records
KW - core PG1351
KW - biomass
KW - holocene
KW - levoglucosan
KW - charcoal
Y1 - 2020
U6 - https://doi.org/10.5194/cp-16-799-2020
SN - 1814-9332
SN - 1814-9324
VL - 16
IS - 2
SP - 788
EP - 818
PB - Copernicus Publications
CY - Göttingen
ER -
TY - JOUR
A1 - Miesner, Timon
A1 - Herzschuh, Ulrike
A1 - Pestryakova, Luidmila Agafyevna
A1 - Wieczorek, Mareike
A1 - Zakharov, Evgenii S.
A1 - Kolmogorov, Alexei I.
A1 - Davydova, Paraskovya V.
A1 - Kruse, Stefan
T1 - Forest structure and individual tree inventories of northeastern Siberia along climatic gradients
JF - Earth system science data : ESSD
N2 - We compile a data set of forest surveys from expeditions to the northeast of the Russian Federation, in Krasnoyarsk Krai, the Republic of Sakha (Yakutia), and the Chukotka Autonomous Okrug (59-73 degrees N, 97-169 degrees E), performed between the years 2011 and 2021. The region is characterized by permafrost soils and forests dominated by larch (Larix gmelinii Rupr. and Larix cajanderi Mayr).
Our data set consists of a plot database describing 226 georeferenced vegetation survey plots and a tree database with information about all the trees on these plots. The tree database, consisting of two tables with the same column names, contains information on the height, species, and vitality of 40 289 trees. A subset of the trees was subject to a more detailed inventory, which recorded the stem diameter at base and at breast height, crown diameter, and height of the beginning of the crown.
We recorded heights up to 28.5 m (median 2.5 m) and stand densities up to 120 000 trees per hectare (median 1197 ha(-1)), with both values tending to be higher in the more southerly areas. Observed taxa include Larix Mill., Pinus L., Picea A. Dietr., Abies Mill., Salix L., Betula L., Populus L., Alnus Mill., and Ulmus L.
In this study, we present the forest inventory data aggregated per plot. Additionally, we connect the data with different remote sensing data products to find out how accurately forest structure can be predicted from such products. Allometries were calculated to obtain the diameter from height measurements for every species group. For Larix, the most frequent of 10 species groups, allometries depended also on the stand density, as denser stands are characterized by thinner trees, relative to height. The remote sensing products used to compare against the inventory data include climate, forest biomass, canopy height, and forest loss or disturbance. We find that the forest metrics measured in the field can only be reconstructed from the remote sensing data to a limited extent, as they depend on local properties. This illustrates the need for ground inventories like those data we present here.
The data can be used for studying the forest structure of northeastern Siberia and for the calibration and validation of remotely sensed data.
Y1 - 2022
U6 - https://doi.org/10.5194/essd-14-5695-2022
SN - 1866-3508
SN - 1866-3516
VL - 14
IS - 12
SP - 5695
EP - 5716
PB - Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Kruse, Stefan
A1 - Stünzi, Simone Maria
A1 - Boike, Julia
A1 - Langer, Moritz
A1 - Gloy, Josias
A1 - Herzschuh, Ulrike
T1 - Novel coupled permafrost-forest model (LAVESI-CryoGrid v1.0) revealing the interplay between permafrost, vegetation, and climate across eastern Siberia
JF - Geoscientific model development : GMD ; an interactive open access journal of the European Geosciences Union
N2 - Boreal forests of Siberia play a relevant role in the global carbon cycle. However, global warming threatens the existence of summergreen larch-dominated ecosystems, likely enabling a transition to evergreen tree taxa with deeper active layers. Complex permafrost-vegetation interactions make it uncertain whether these ecosystems could develop into a carbon source rather than continuing atmospheric carbon sequestration under global warming. Consequently, shedding light on the role of current and future active layer dynamics and the feedbacks with the apparent tree species is crucial to predict boreal forest transition dynamics and thus for aboveground forest biomass and carbon stock developments. Hence, we established a coupled model version amalgamating a one-dimensional permafrost multilayer forest land-surface model (CryoGrid) with LAVESI, an individual-based and spatially explicit forest model for larch species (Larix Mill.), extended for this study by including other relevant Siberian forest species and explicit terrain.
Following parameterization, we ran simulations with the coupled version to the near future to 2030 with a mild climate-warming scenario. We focus on three regions covering a gradient of summergreen forests in the east at Spasskaya Pad, mixed summergreen-evergreen forests close to Nyurba, and the warmest area at Lake Khamra in the southeast of Yakutia, Russia. Coupled simulations were run with the newly implemented boreal forest species and compared to runs allowing only one species at a time, as well as to simulations using just LAVESI. Results reveal that the coupled version corrects for overestimation of active layer thickness (ALT) and soil moisture, and large differences in established forests are simulated. We conclude that the coupled version can simulate the complex environment of eastern Siberia by reproducing vegetation patterns, making it an excellent tool to disentangle processes driving boreal forest dynamics.
Y1 - 2022
U6 - https://doi.org/10.5194/gmd-15-2395-2022
SN - 1991-959X
SN - 1991-9603
VL - 15
IS - 6
SP - 2395
EP - 2422
PB - Copernicus
CY - Göttingen
ER -
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 - 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, 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 -
TY - JOUR
A1 - Courtin, Jérémy
A1 - Andreev, Andrei
A1 - Raschke, Elena
A1 - Bala, Sarah
A1 - Biskaborn, Boris
A1 - Liu, Sisi
A1 - Zimmermann, Heike
A1 - Diekmann, Bernhard
A1 - Stoof-Leichsenring, Kathleen R.
A1 - Pestryakova, Luidmila Agafyevna
A1 - Herzschuh, Ulrike
T1 - Vegetation changes in Southeastern Siberia during the late pleistocene and the holocene
JF - Frontiers in Ecology and Evolution
N2 - Relationships between climate, species composition, and species richness are of particular importance for understanding how boreal ecosystems will respond to ongoing climate change. This study aims to reconstruct changes in terrestrial vegetation composition and taxa richness during the glacial Late Pleistocene and the interglacial Holocene in the sparsely studied southeastern Yakutia (Siberia) by using pollen and sedimentary ancient DNA (sedaDNA) records. Pollen and sedaDNA metabarcoding data using the trnL g and h markers were obtained from a sediment core from Lake Bolshoe Toko. Both proxies were used to reconstruct the vegetation composition, while metabarcoding data were also used to investigate changes in plant taxa richness. The combination of pollen and sedaDNA approaches allows a robust estimation of regional and local past terrestrial vegetation composition around Bolshoe Toko during the last similar to 35,000 years. Both proxies suggest that during the Late Pleistocene, southeastern Siberia was covered by open steppe-tundra dominated by graminoids and forbs with patches of shrubs, confirming that steppe-tundra extended far south in Siberia. Both proxies show disturbance at the transition between the Late Pleistocene and the Holocene suggesting a period with scarce vegetation, changes in the hydrochemical conditions in the lake, and in sedimentation rates. Both proxies document drastic changes in vegetation composition in the early Holocene with an increased number of trees and shrubs and the appearance of new tree taxa in the lake's vicinity. The sedaDNA method suggests that the Late Pleistocene steppe-tundra vegetation supported a higher number of terrestrial plant taxa than the forested Holocene. This could be explained, for example, by the "keystone herbivore" hypothesis, which suggests that Late Pleistocene megaherbivores were able to maintain a high plant diversity. This is discussed in the light of the data with the broadly accepted species-area hypothesis as steppe-tundra covered such an extensive area during the Late Pleistocene.
KW - last glacial
KW - Holocene
KW - Lake Bolshoe Toko
KW - paleoenvironments
KW - sedimentary ancient DNA
KW - metabarcoding
KW - trnL
KW - pollen
Y1 - 2021
U6 - https://doi.org/10.3389/fevo.2021.625096
SN - 2296-701X
VL - 9
PB - Frontiers Media
CY - Lausanne
ER -
TY - JOUR
A1 - Heim, Birgit
A1 - Lisovski, Simeon
A1 - Wieczorek, Mareike
A1 - Morgenstern, Anne
A1 - Juhls, Bennet
A1 - Shevtsova, Iuliia
A1 - Kruse, Stefan
A1 - Boike, Julia
A1 - Fedorova, Irina
A1 - Herzschuh, Ulrike
T1 - Spring snow cover duration and tundra greenness in the Lena Delta, Siberia
BT - two decades of MODIS satellite time series (2001-2021)
JF - Environmental research letters
N2 - The Lena Delta in Siberia is the largest delta in the Arctic and as a snow-dominated ecosystem particularly vulnerable to climate change.
Using the two decades of MODerate resolution Imaging Spectroradiometer satellite acquisitions, this study investigates interannual and spatial variability of snow-cover duration and summer vegetation vitality in the Lena Delta.
We approximated snow by the application of the normalized difference snow index and vegetation greenness by the normalized difference vegetation index (NDVI). We consolidated the analyses by integrating reanalysis products on air temperature from 2001 to 2021, and air temperature, ground temperature, and the date of snow-melt from time-lapse camera (TLC) observations from the Samoylov observatory located in the central delta.
We extracted spring snow-cover duration determined by a latitudinal gradient. The 'regular year' snow-melt is transgressing from mid-May to late May within a time window of 10 days across the delta.
We calculated yearly deviations per grid cell for two defined regions, one for the delta, and one focusing on the central delta. We identified an ensemble of early snow-melt years from 2012 to 2014, with snow-melt already starting in early May, and two late snow-melt years in 2004 and 2017, with snow-melt starting in June. In the times of TLC recording, the years of early and late snow-melt were confirmed.
In the three summers after early snow-melt, summer vegetation greenness showed neither positive nor negative deviations. Whereas, vegetation greenness was reduced in 2004 after late snow-melt together with the lowest June monthly air temperature of the time series record. Since 2005, vegetation greenness is rising, with maxima in 2018 and 2021.
The NDVI rise since 2018 is preceded by up to 4 degrees C warmer than average June air temperature. The ongoing operation of satellite missions allows to monitor a wide range of land surface properties and processes that will provide urgently needed data in times when logistical challenges lead to data gaps in land-based observations in the rapidly changing Arctic.
KW - Arctic vegetation
KW - tundra
KW - snow cover duration
KW - NDVI
KW - NDSI
KW - MODIS
KW - Lena Delta
Y1 - 2022
U6 - https://doi.org/10.1088/1748-9326/ac8066
SN - 1748-9326
VL - 17
IS - 8
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Herzschuh, Ulrike
A1 - Li, Chenzhi
A1 - Boehmer, Thomas
A1 - Postl, Alexander K.
A1 - Heim, Birgit
A1 - Andreev, Andrei A.
A1 - Cao, Xianyong
A1 - Wieczorek, Mareike
A1 - Ni, Jian
T1 - LegacyPollen 1.0
BT - a taxonomically harmonized global late Quaternary pollen dataset of 2831 records with standardized chronologies
JF - Earth system science data : ESSD
N2 - Here we describe the LegacyPollen 1.0, a dataset of 2831 fossil pollen records with metadata, a harmonized taxonomy, and standardized chronologies.
A total of 1032 records originate from North America, 1075 from Europe, 488 from Asia, 150 from Latin America, 54 from Africa, and 32 from the Indo-Pacific.
The pollen data cover the late Quaternary (mostly the Holocene). The original 10 110 pollen taxa names (including variations in the notations) were harmonized to 1002 terrestrial taxa (including Cyperaceae), with woody taxa and major herbaceous taxa harmonized to genus level and other herbaceous taxa to family level.
The dataset is valuable for synthesis studies of, for example, taxa areal changes, vegetation dynamics, human impacts (e.g., deforestation), and climate change at global or continental scales.
The harmonized pollen and metadata as well as the harmonization table are available from PANGAEA (https://doi.org/10.1594/PANGAEA.929773; Herzschuh et al., 2021). R code for the harmonization is provided at Zenodo (https://doi.org/10.5281/zenodo.5910972; Herzschuh et al., 2022) so that datasets at a customized harmonization level can be easily established.
Y1 - 2022
U6 - https://doi.org/10.5194/essd-14-3213-2022
SN - 1866-3508
SN - 1866-3516
VL - 14
IS - 7
SP - 3213
EP - 3227
PB - Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Mayer, Dennis
A1 - Lever, Fabiano
A1 - Picconi, David
A1 - Metje, Jan
A1 - Ališauskas, Skirmantas
A1 - Calegari, Francesca
A1 - Düsterer, Stefan
A1 - Ehlert, Christopher
A1 - Feifel, Raimund
A1 - Niebuhr, Mario
A1 - Manschwetus, Bastian
A1 - Kuhlmann, Marion
A1 - Mazza, Tommaso
A1 - Robinson, Matthew Scott
A1 - Squibb, Richard James
A1 - Trabattoni, Andrea
A1 - Wallner, Måns
A1 - Saalfrank, Peter
A1 - Wolf, Thomas J. A.
A1 - Gühr, Markus
T1 - Following excited-state chemical shifts in molecular ultrafast x-ray photoelectron spectroscopy
JF - Nature Communications
N2 - The conversion of photon energy into other energetic forms in molecules is accompanied by charge moving on ultrafast timescales. We directly observe the charge motion at a specific site in an electronically excited molecule using time-resolved x-ray photoelectron spectroscopy (TR-XPS). We extend the concept of static chemical shift from conventional XPS by the excited-state chemical shift (ESCS), which is connected to the charge in the framework of a potential model. This allows us to invert TR-XPS spectra to the dynamic charge at a specific atom. We demonstrate the power of TR-XPS by using sulphur 2p-core-electron-emission probing to study the UV-excited dynamics of 2-thiouracil. The method allows us to discover that a major part of the population relaxes to the molecular ground state within 220–250 fs. In addition, a 250-fs oscillation, visible in the kinetic energy of the TR-XPS, reveals a coherent exchange of population among electronic states.
Y1 - 2022
U6 - https://doi.org/10.1038/s41467-021-27908-y
SN - 2041-1723
N1 - These authors contributed equally: D. Mayer, F. Lever.
A Publisher Correction to this article was published on 09 March 2022.
This article has been updated.
VL - 13
PB - Springer Nature
CY - Berlin
ER -