ALBERT

Description: Here, we provide the raw pollen data archived in three Siberian lake sediment cores spanning the mid-Holocene to the present (7.6-0 cal ka BP), from northern typical tundra to southern open larch forest in the Omoloy region. There are three cores: 1. 14-OM-20B, Lat. / °: 70.53, Lon. / °: 132.91, Ele. / m a.s.l.: 52, Modern vegetation: open larch forest, Lake area / km2: 0.26, Maximal depth / m: 3.4 2. 14-OM-02B, Lat. / °: 70.72, Lon. / °: 132.67, Ele. / m a.s.l.: 58, Modern vegetation: forest tundra, Lake area / km2: 0.08, Maximal depth / m: 3.5 3. 14-OM-12A, Lat. / °: 70.96, Lon. / °: 132.57, Ele. / m a.s.l.: 60, Modern vegetation: tundra, Lake area / km2: 0.09, Maximal depth / m: 4.5 Three lake sediment cores, 14OM12A (33 cm long), 14OM02B (49.5 cm long) and 14OM20B (86 cm long), were recovered from three sites using a UWITEC gravity corer (6 cm internal diameter) equipped with a hammer tool in July 2014. From the three cores, 16 bulk organic carbon samples were selected because of the lack of macrofossil remains and radiocarbon dated using accelerator mass spectrometry (AMS) at Poznań radiocarbon laboratory of Adam Mickiewicz University, Poland. In addition, 30 freeze-dried samples per core at 0.25 or 0.5 cm intervals between 0 and 15 cm were analysed for 210Pb/137Cs at the Liverpool University Environmental Radioactivity Laboratory. In this project, we analyse pollen and sedaDNA (Liu et al., 2020; doi:10.5061/dryad.69p8cz900) from three lake sediment cores from the Omoloy region in north-eastern Siberia (northern Yakutia), which are currently surrounded by different vegetation types ranging from typical tundra to open larch forest. First, our aim is to compare sedaDNA with the pollen data to see whether both methods track the same pattern with respect to compositional changes and diversity changes across the northern Russian treeline zone or are complementary to each other. Second, we reconstruct the mid- to late-Holocene changes of vegetation composition along a north–south transect. Third, we use the sedaDNA data to reconstruct variations in species richness and relate this to vegetation and climate change.

Description: Understanding the resilience of African savannas to global change requires quantitative information on long-term vegetation dynamics. Here we present a reconstruction of past vegetation cover of the northern Namibian savanna obtained after applying the REVEALS model to fossil pollen data from Lake Otjikoto. We also present modern pollen and vegetation data used to calculate pollen productivity estimates for the major Namibian savanna taxa Acacia (Senegalia, Vachellia), Combretaceae, Dichrostachys, Grewia and Poaceae. Data were collected at 10 sites along a rainfall gradient in north central Namibia. Modern pollen was extracted from soil samples collected from plots at the different sites. Vegetation data were extracted from satellite images covering a 1.5 km radius from the plots where pollen was collected. The mean cover of the studied taxa was calculated by 100 m rings.

Description: In total 16 branches of three individuals were cut in the field into 10 cm-long pieces and dried. Samples were sanded using sandpaper and decreasing grain size until the surface was even and the tree rings clearly visible and then scanned at 4800 dpi on a flatbed scanner. Tree rings were counted in Coorecorder (Cybis Elektronik & Data AB) at the oldest part and the middle pieces, and for the longest branch at four positions.

Description: Vegetation surveys were carried out in Northwest Territories, Yukon and British Columbia in Canada. The study area is within the boreal forest biome and is partially underlain by permafrost soils. The aim was to record the projective ground vegetation in different boreal forest types studied during the CA-Land_2022_NWCanada field campaign in July and August 2022. Ground vegetation was surveyed for different vegetation types within a circular forest plot of 15m radius. Depending on the heterogeneity of the forest plot, multiple vegetation types (VA, VB, or VC) were chosen for survey. The assignment of a vegetation type is always unique to a site. Their cover on the circular forest plot was recorded in percent. In total, 46 vegetation types at 32 forest plots were assessed. All data were collected by scientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) Germany, and the University of Potsdam Germany.

Description: Field investigations were performed in four areas: a treeless mountainous tundra (16-KP-04; Lake Rauchuagytgyn area), tundra-taiga transition zone (16-KP-01, Lake Ilirney area) and a northern taiga (18-BIL-01, 18-BIL-02). In total, 39 sites were investigated. The sites were placed to cover different vegetation communities that characterise central Chukotka. Fifteen-meter radius sample plots (sites) were demarcated in the most homogeneous locations. Heterogeneity was accommodated by roughly assorting vegetation into two to three vegetation types per sampling plot. Within each area of roughly estimated vegetation types we selected one 0.5 x 0.5 m subplot for representative ground-layer above-ground biomass (ABG) harvesting (major taxa and other). For moss and lichen AGB harvesting inside 0.5 x 0.5 m subplots representative 0.1 x 0.1 m subplots were chosen. All harvested AGB samples were weighed fresh in the field. In general, AGB samples with a weight of more than 15 g were subsampled. All samples were oven dried (60 °C, 24 h for ground-layer and moss and lichen samples, 48 h for shrub and tree branch samples) and weighed again. This dataset contains the raw data of dry weight for each sub-ground vegetation type sampling plot. All data was collected by scientists from Alfred Wegener Institute (AWI), Helmholtz Centre for Polar and Marine Research and University of Potsdam, Germany, The Institute for Biological problems of the Cryolithozone, Russian Academy of Sciences, Siberian branch, and The Institute of Natural Sciences, North-Eastern Federal University of Yakutsk, Yakutsk, Russia. The AGB data calculations for the plot area including tree and tall shrubs can be found at https://doi.org/10.1594/PANGAEA.923719.