Description: Due to methodological challenges there are only a few studies that focus on macrophyte dynamics in large lakes despite their notable role in a lake's ecosystem functioning. This study investigates composition and productivity changes of the submerged vegetation of Lake Karakul, Pamir Mountains (Tajikistan), using sedimentary ancient DNA metabarcoding and elemental (C/N) and isotopic (d13C, d15N) measurements of Stuckenia cf. pamirica ((Baagøe) Z.Kaplan; Potamogetonaceae) leaf remains. No Stuckenia cf. pamirica leaf remains were found for 28.7 to 26.1 cal ka BP, when both Potamogetonaceae and Chara (L.) DNA sequences were recorded, suggesting sparse submerged vegetation at the coring site. This agrees with the inference of a deep lake reached using geochemical proxies. From 26.1 to 17.5 cal ka BP a few macrophyte remains and high numbers of Potamogetonaceae sequences were recovered: lake level was probably low, as suggested by other studies on the lake. Another phase of increased numbers of Chara sequences and the absence of Stuckenia cf. pamirica leaf remains was found between 17.5 and 12.2 cal ka BP, which coincides with a lake-level transgression at Lake Karakul as indicated by paleo-shoreline investigations. Analyses of macrophyte remains reveal intermediate paleo-productivity from 6.9 cal ka BP and high paleo-productivity from 2.2 cal ka BP onwards. From comparisons with other studies, we suggest that lake-level changes are the main driver for the submerged vegetation composition and productivity at the coring site in Lake Karakul and underline our conclusions by depicting the present-day distribution of Stuckenia cf. pamirica and Chara within the lake.

Description: We present results of analyses on a sediment core from Lake Karakul, located in the eastern Pamir Mountains, Tajikistan. The core spans the last ~29 cal ka. We investigated and assessed processes internal and external to the lake to infer changes in past moisture availability. Among the variables used to infer lake-external processes, high values of grain-size end-member (EM) 3 (wide grain-size distribution that reflects fluvial input) and high Sr/Rb and Zr/Rb ratios (coinciding with coarse grain sizes), are indicative of moister conditions. High values in EM1, EM2 (peaks of small grain sizes that reflect long-distance dust transport or fine, glacially derived clastic input) and TiO 2 (terrigenous input) are thought to reflect greater influence of dry air masses, most likely of Westerly origin. High input of dust from distant sources, beginning before the Last Glacial Maximum (LGM) and continuing to the late glacial, reflects the influence of dry Westerlies, whereas peaks in fluvial input suggest increased moisture availability. The early to early-middle Holocene is characterised by coarse mean grain sizes, indicating constant, high fluvial input and moister conditions in the region. A steady increase in terrigenous dust and a decrease in fluvial input from 6.6 cal ka BP onwards points to the Westerlies as the predominant atmospheric circulation through to present, and marks a return to drier and even arid conditions in the area. Proxies for productivity (TOC, TOC/TN, TOC Br ), redox potential (Fe/Mn) and changes in the endogenic carbonate precipitation (TIC, d18 O) indicate changes within the lake. Low productivity characterised the lake from the late Pleistocene until 6.6 cal ka BP, but productivity increased rapidly afterwards. Lake level remained low until the LGM, but water depth increased to a maximum during the late glacial and remained high into the early Holocene. Subsequently, the water level decreased to its present stage. Today the lake system is mainly climatically controlled, but the depositional regime is also driven by internal limnogeological processes.

Description: Datasets that provide high-resolution palaeoenvironmental information during the last glacial maximum in Chukotka, Arctic Siberia are limited. This data compilation comprises multiproxy data extracted from sediment core EN18218 obtained from Arctic glacial lake Rauchuagytgyn (67.7922°N, 168.7312°E) by piston coring during the Chukotka 2018 expedition. The dataset covers the late Pleistocene and Holocene (ca. 29 cal. ka BP). Observations within this dataset include 14C radiocarbon dates, hydrochemistry observations, sedimentological observations (water content, bulk density, grain-size, sediment color, biogeochemistry (Total sulphur (TS), Total carbon (TC), Total organic carbon (TOC), Total inorganic carbon (TIC)), X-ray fluorescence (XRF) based sediment-geochemistry and magnetic susceptibility measurements. Radiocarbon dating was performed with accelerator mass spectrometry (AMS) using the Mini Carbon Dating System (MICADAS) at AWI Bremerhaven, Germany. Water content and bulk density were measured according to the volumetric methods of Avnimelech et al, (2001). Sediment grain-size was measured using a Malvern Mastersizer 3000 laser diffraction particle analyser. Biogeochemical parameters were obtained using a Vario SoliTOC cube elemental analyser "Elementar Corp., Germany) and Eltra Carbon and Sulfur determinator (Eltra GmbH, Germany). XRF and color scanning was performed using an Avaatech core-scanner and line-scanner attachment. Magnetic susceptibility measurements were performed with a Bartington MS2E spot reading sensor. A full description of methodological procedures used within this study is provided in the publication (Vyse et al., in review).

Description: Arctic and alpine treelines worldwide differ in their reactions to climate change. A northward advance of or densification within the treeline ecotone will likely influence climate-vegetation feedback mechanisms. In our study, which was conducted in the Taimyr Depression in the North Siberian Lowlands, w present a combined field- and model-based approach helping us to better understand the population processes involved in the responses of the whole treeline ecotone, spanning from closed forest to single-tree tundra, to climate warming. Using information on stand structure, tree age, and seed quality and quantity from seven sites, we investigate effects of intra-specific competition and seed availability on the specific impact of recent climate warming on larch stands. Field data show that tree density is highest in the forest-tundra, and average tree size decreases from closed forest to single-tree tundra. Age-structure analyses indicate that the trees in the closed forest and forest-tundra have been present for at least ~240 years. At all sites except the most southerly ones, past establishment is positively correlated with regional temperature increase. In the single-tree tundra however, a change in growth form from krummholz to erect trees, beginning ~130 years ago, rather than establishment date has been recorded. Seed mass decreases from south to north, while seed quantity increases. Simulations with LAVESI (Larix Vegetation Simulator) further suggest that relative density changes strongly in response to a warming signal in the forest-tundra while intra-specific competition limits densification in the closed forest and seed limitation hinders densification in the single-tree tundra. We find striking differences in strength and timing of responses to recent climate warming. While forest-tundra stands recently densified, recruitment is almost non-existent at the southern and northern end of the ecotone due to autecological processes. Palaeo-treelines may therefore be inappropriate to infer past temperature changes at a fine scale. Moreover, a lagged treeline response to past warming will, via feedback mechanisms, influence climate change in the future.

Description: Datasets that provide palaeoenvironmental information extending beyond marine isotope stage 3 (MIS3) in Chukotka, far east Russia are limited. This data compilation comprises multiproxy sediment-geochemical, sedimentological and preliminary biological data from sediment core EN18208 obtained from lake Ilirney (67°21'N, 168°19'E), Chukotka by piston coring during the Chukotka 2018 expedition. Observations within this dataset include radiocarbon and optically stimulated luminescence (OSL) dates, X-ray fluorescence (XRF) based sediment-geochemistry, sedimentological observations (water content, bulk density, grain-size, biogeochemistry (Total carbon (TC), Total nitrogen (TN), Total organic carbon (TOC)), mineralogy) and preliminary biological data (Diatom percentages from smear slides and diatom benthic/planktonic ratios from diatom slides). The provided data compilation provides observations permitting the palaeoenvironmental reconstruction of lake Ilirney since 53.4 ka BP during the late Pleistocene.