cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.30896020
title: Effects of ice-wedge degradation and warming on Arctic tundra vegetation across a climatic gradient using a nitrogen-based model

description: Ice-wedge polygons in Arctic tundra landscapes influence hydrology, nutrients, thermal regimes, and vegetation. Ice-wedges are particularly vulnerable to warming events, and widespread degradation has been observed in recent decades. While increased vegetation growth is predicted to offset some of the nutrient losses from thawing Arctic soils, evolving Arctic vegetation carbon and nitrogen stocks are poorly understood. To explore effects of warming and ice-wedge degradation on Arctic vegetation, we used aboveground plant biomass data from stages of ice-wedge degradation at two northern Arctic tundra sites (Jago River and Prudhoe Bay, AK) to parameterize and test a nutrient-based, plant community and ecosystem model (ArcVeg) incorporating ice-wedges within a landscape for different Arctic tundra locations. Warming increased both aboveground and belowground biomass but introducing ice-wedge degradation led to shrub loss and a shift from terrestrial moss and shrub-dominated communities to aquatic moss and graminoid-dominated communities. In northern locations, degradation reduced vegetation C and N stocks due to biomass loss, whereas at the southern location, total plant C and N increased substantially due to moss proliferation. Model predictions suggest that ice-wedge degradation effects are accentuated under warming, and southern Arctic tundra aquatic moss proliferation may offset or even exceed biomass lost.
DOI: 10.6084/m9.figshare.30896020.v1
title: Effects of ice-wedge degradation and warming on Arctic tundra vegetation across a climatic gradient using a nitrogen-based model

description: Ice-wedge polygons in Arctic tundra landscapes influence hydrology, nutrients, thermal regimes, and vegetation. Ice-wedges are particularly vulnerable to warming events, and widespread degradation has been observed in recent decades. While increased vegetation growth is predicted to offset some of the nutrient losses from thawing Arctic soils, evolving Arctic vegetation carbon and nitrogen stocks are poorly understood. To explore effects of warming and ice-wedge degradation on Arctic vegetation, we used aboveground plant biomass data from stages of ice-wedge degradation at two northern Arctic tundra sites (Jago River and Prudhoe Bay, AK) to parameterize and test a nutrient-based, plant community and ecosystem model (ArcVeg) incorporating ice-wedges within a landscape for different Arctic tundra locations. Warming increased both aboveground and belowground biomass but introducing ice-wedge degradation led to shrub loss and a shift from terrestrial moss and shrub-dominated communities to aquatic moss and graminoid-dominated communities. In northern locations, degradation reduced vegetation C and N stocks due to biomass loss, whereas at the southern location, total plant C and N increased substantially due to moss proliferation. Model predictions suggest that ice-wedge degradation effects are accentuated under warming, and southern Arctic tundra aquatic moss proliferation may offset or even exceed biomass lost.
DOI: 10.6084/m9.figshare.30309686
title: Sea-level driven isolation of glacial plant refugia revealed by submerged lake sediment from the Bering Land Bridge and St. Matthew Island

description: Bering Land Bridge (BLB) climate and vegetation during the Last Glacial Maximum (LGM) remains largely understudied, given challenges associated with collecting records from the submerged BLB. Previous records, confined to the margins of the modern land area and adjacent shelf, reveal conflicting interpretations of Beringian vegetation during the LGM. Here, we reconstruct LGM vegetation, sedimentology, and stable isotopes from a central BLB paleo-lake (Lake Knebel, LK) and compare it with a Holocene peat record from nearby St. Matthew Island (SMI). Results show strong similarities between LGM and late Holocene pollen assemblages, although with differences in relative taxonomic abundance. LGM communities are consistent with a cold and dry steppe or herb tundra environment but suggest the possibility of localized Betula presence in low-lying areas. LK’s bedded lacustrine stratigraphy transitions into undisturbed marine sediments by ~19 ka, providing a maximum limiting age of the transgression. Shrub absence on SMI today and during the Holocene is consistent with island isolation before ~14 to 15 ka, when Betula expanded rapidly at most sites with Bølling-Allerød warming. The combined vegetation evidence indicates preservation of LGM tundra and steppe vegetation assemblages on SMI, suggesting that island vegetation communities may provide additional constraints on the timing of sea level transgression.
DOI: 10.6084/m9.figshare.30309686.v1
title: Sea-level driven isolation of glacial plant refugia revealed by submerged lake sediment from the Bering Land Bridge and St. Matthew Island

description: Bering Land Bridge (BLB) climate and vegetation during the Last Glacial Maximum (LGM) remains largely understudied, given challenges associated with collecting records from the submerged BLB. Previous records, confined to the margins of the modern land area and adjacent shelf, reveal conflicting interpretations of Beringian vegetation during the LGM. Here, we reconstruct LGM vegetation, sedimentology, and stable isotopes from a central BLB paleo-lake (Lake Knebel, LK) and compare it with a Holocene peat record from nearby St. Matthew Island (SMI). Results show strong similarities between LGM and late Holocene pollen assemblages, although with differences in relative taxonomic abundance. LGM communities are consistent with a cold and dry steppe or herb tundra environment but suggest the possibility of localized Betula presence in low-lying areas. LK’s bedded lacustrine stratigraphy transitions into undisturbed marine sediments by ~19 ka, providing a maximum limiting age of the transgression. Shrub absence on SMI today and during the Holocene is consistent with island isolation before ~14 to 15 ka, when Betula expanded rapidly at most sites with Bølling-Allerød warming. The combined vegetation evidence indicates preservation of LGM tundra and steppe vegetation assemblages on SMI, suggesting that island vegetation communities may provide additional constraints on the timing of sea level transgression.
DOI: 10.6084/m9.figshare.30142358
title: 6,000 years of vegetation and fire history at the timberline ecotone site Drakolimni Smolikas in the Pindos Mountains, northwestern Greece

description: The vegetation history and the onset of agricultural exploitation of the mountainous areas of Greece are mostly unstudied. We present a paleoecological study of the timberline ecotone site Drakolimni Smolikas at 2,140 m.a.s.l. in the Pindos Mountains. Through pollen, spores, stomata, algae cells, macrofossils, microscopic charcoal analysis, magnetic susceptibility, X-ray fluorescence, and a radiocarbon-dated chronology, we reconstruct the vegetation, fire, and environmental history of Mount Smolikas over the past 6,200 years. Additionally, we estimate July temperature trends through chironomid analysis. This multiproxy procedure allows us to analyze the linkages between climate, vegetation, fire, and land use. Coeval downward shifts of the timberline and increases of crops and weeds suggest anthropogenic control of the timberline altitude. Our results indicate the presence of pastoralism on Mount Smolikas since at least the Late Bronze Age, possibly the Neolithic, much earlier than previously thought. Despite the early human disturbance, and a ca. 2°C mean July air temperature decrease from the Holocene Thermal Maximum to the Late Holocene, the vegetation structure and composition around our site remained surprisingly resilient. The landscape was always dominated by sparse Bosnian pine (<i>Pinus heldreichii</i>) forests and the lake was situated within the timberline ecotone throughout most of the record.
DOI: 10.6084/m9.figshare.30142358.v1
title: 6,000 years of vegetation and fire history at the timberline ecotone site Drakolimni Smolikas in the Pindos Mountains, northwestern Greece

description: The vegetation history and the onset of agricultural exploitation of the mountainous areas of Greece are mostly unstudied. We present a paleoecological study of the timberline ecotone site Drakolimni Smolikas at 2,140 m.a.s.l. in the Pindos Mountains. Through pollen, spores, stomata, algae cells, macrofossils, microscopic charcoal analysis, magnetic susceptibility, X-ray fluorescence, and a radiocarbon-dated chronology, we reconstruct the vegetation, fire, and environmental history of Mount Smolikas over the past 6,200 years. Additionally, we estimate July temperature trends through chironomid analysis. This multiproxy procedure allows us to analyze the linkages between climate, vegetation, fire, and land use. Coeval downward shifts of the timberline and increases of crops and weeds suggest anthropogenic control of the timberline altitude. Our results indicate the presence of pastoralism on Mount Smolikas since at least the Late Bronze Age, possibly the Neolithic, much earlier than previously thought. Despite the early human disturbance, and a ca. 2°C mean July air temperature decrease from the Holocene Thermal Maximum to the Late Holocene, the vegetation structure and composition around our site remained surprisingly resilient. The landscape was always dominated by sparse Bosnian pine (<i>Pinus heldreichii</i>) forests and the lake was situated within the timberline ecotone throughout most of the record.
DOI: 10.6084/m9.figshare.29128253
title: Ongoing regime shift on subarctic Disko Island, Greenland

description: Significant amounts of soil organic carbon (SOC) are stored in high-latitude soils and are greatly impacted by climate change. Here, we studied soil profiles collected from Disko Island, Greenland, to investigate recent regime shifts, including organic soil initiation and expansion. Our results show newly initiated (age &lt;1950) organic soils overlying the mineral soils in new areas or expansion of older organic soils. We also found signs of vegetation shift in which <i>Sphagnum</i> mosses have become established on sedge habitats. These changes could be linked with the recent warming and longer growing seasons. Both regime shifts have implications for SOC storage, and SOC stock analyses further suggested that, considering their young age and thin organic layer, our sites may store equivalent amounts of carbon or even more than previous studies have found in the area. If conditions for organic soil accumulation continue to improve, our sites may form significant future carbon sinks and stores.
DOI: 10.6084/m9.figshare.29128253.v1
title: Ongoing regime shift on subarctic Disko Island, Greenland

description: Significant amounts of soil organic carbon (SOC) are stored in high-latitude soils and are greatly impacted by climate change. Here, we studied soil profiles collected from Disko Island, Greenland, to investigate recent regime shifts, including organic soil initiation and expansion. Our results show newly initiated (age &lt;1950) organic soils overlying the mineral soils in new areas or expansion of older organic soils. We also found signs of vegetation shift in which <i>Sphagnum</i> mosses have become established on sedge habitats. These changes could be linked with the recent warming and longer growing seasons. Both regime shifts have implications for SOC storage, and SOC stock analyses further suggested that, considering their young age and thin organic layer, our sites may store equivalent amounts of carbon or even more than previous studies have found in the area. If conditions for organic soil accumulation continue to improve, our sites may form significant future carbon sinks and stores.
DOI: 10.6084/m9.figshare.29656676
title: A 15,800 year record of productivity, carbon accumulation and environmental change at Eight Mile Lake and its catchment, central Alaska

description: Despite their efficient burial of organic carbon (OC), the role of high-latitude lakes in storing and processing OC under changing climates is poorly understood. We investigate a 15,800 year sedimentary record from Eight Mile Lake, central Alaska, to understand how paleoclimate influenced productivity and OC storage. We compare our data (physical and biogeochemical properties) to data from terrestrial soil cores in the watershed and find three distinct depositional phases. From 15.8–11.7 ka lake sediment accumulated rapidly with the highest OC accumulation rates (OCAR), comparable to Holocene organic-rich soils in the catchment, and promoted by high burial efficiency and enhanced erosion. From 11.7–5.5 ka proportionally more aquatic organic matter accumulated under stable climate conditions. From 5.5 ka – present, lacustrine OCAR was low but with high century-scale variability, suggesting variable erosion and transport with increased moisture, concurrent with loess and organic-rich soil buildup on the hillslope. Our findings demonstrate that factors promoting syngenetic permafrost growth and terrestrial OCAR (primarily temperature and geomorphology) differ from those promoting OCAR in high-latitude lakes (primarily sedimentation rates). Overall, we present a unique pairing of Holocene lake sediment and soil records, highlighting the importance of burial efficiency on OCAR in high-latitude lakes.
DOI: 10.6084/m9.figshare.29656676.v1
title: A 15,800 year record of productivity, carbon accumulation and environmental change at Eight Mile Lake and its catchment, central Alaska

description: Despite their efficient burial of organic carbon (OC), the role of high-latitude lakes in storing and processing OC under changing climates is poorly understood. We investigate a 15,800 year sedimentary record from Eight Mile Lake, central Alaska, to understand how paleoclimate influenced productivity and OC storage. We compare our data (physical and biogeochemical properties) to data from terrestrial soil cores in the watershed and find three distinct depositional phases. From 15.8–11.7 ka lake sediment accumulated rapidly with the highest OC accumulation rates (OCAR), comparable to Holocene organic-rich soils in the catchment, and promoted by high burial efficiency and enhanced erosion. From 11.7–5.5 ka proportionally more aquatic organic matter accumulated under stable climate conditions. From 5.5 ka – present, lacustrine OCAR was low but with high century-scale variability, suggesting variable erosion and transport with increased moisture, concurrent with loess and organic-rich soil buildup on the hillslope. Our findings demonstrate that factors promoting syngenetic permafrost growth and terrestrial OCAR (primarily temperature and geomorphology) differ from those promoting OCAR in high-latitude lakes (primarily sedimentation rates). Overall, we present a unique pairing of Holocene lake sediment and soil records, highlighting the importance of burial efficiency on OCAR in high-latitude lakes.
DOI: 10.6084/m9.figshare.28777339
title: Plasticity in colonization and mycorrhizal benefit in the common Arctic species <i>Avenella flexuosa</i> in response to grazing

description: Arctic grasslands are intensively grazed. The common grass <i>Avenella flexuosa</i> is particularly common in grazed areas, but the mechanisms of its adaptation to grazing are not fully known. We tested whether the plasticity of arbuscular mycorrhizal symbiosis in <i>Avenella flexuosa</i> roots contributes to its adaptation to grazing. We observed a clear decline in arbuscular mycorrhizal symbiont root colonization in <i>Avenella flexuosa</i> as a response to grazing in arctic meadow ecosystems in Northern Fennoscandia. In the greenhouse, arbuscular mycorrhizal fungi and fine endophytes responded negatively to fertilization, while the effect of removing foliage was marginally significant. These results indicate that the negative effect of reindeer grazing on arbuscular mycorrhizal frequency in <i>Avenella flexuosa</i> in field are mechanistically caused by increased nitrogen availability rather than consumption of foliage. The benefit of the symbiosis was positive for both plant and the fungus in the greenhouse as indicated by colonization and mycorrhizal benefit to the plant. However, when defoliated, the fungus maintained its benefits and the plant lost significantly, whereas when fertilized, the plant maintained its benefits and the fungus lost significantly. Reducing resource allocation to mycorrhiza while keeping the mycorrhizal benefits unchanged may at least partially explain <i>Avenella flexuosa</i> adaptation to grazing.
DOI: 10.6084/m9.figshare.28777339.v1
title: Plasticity in colonization and mycorrhizal benefit in the common Arctic species <i>Avenella flexuosa</i> in response to grazing

description: Arctic grasslands are intensively grazed. The common grass <i>Avenella flexuosa</i> is particularly common in grazed areas, but the mechanisms of its adaptation to grazing are not fully known. We tested whether the plasticity of arbuscular mycorrhizal symbiosis in <i>Avenella flexuosa</i> roots contributes to its adaptation to grazing. We observed a clear decline in arbuscular mycorrhizal symbiont root colonization in <i>Avenella flexuosa</i> as a response to grazing in arctic meadow ecosystems in Northern Fennoscandia. In the greenhouse, arbuscular mycorrhizal fungi and fine endophytes responded negatively to fertilization, while the effect of removing foliage was marginally significant. These results indicate that the negative effect of reindeer grazing on arbuscular mycorrhizal frequency in <i>Avenella flexuosa</i> in field are mechanistically caused by increased nitrogen availability rather than consumption of foliage. The benefit of the symbiosis was positive for both plant and the fungus in the greenhouse as indicated by colonization and mycorrhizal benefit to the plant. However, when defoliated, the fungus maintained its benefits and the plant lost significantly, whereas when fertilized, the plant maintained its benefits and the fungus lost significantly. Reducing resource allocation to mycorrhiza while keeping the mycorrhizal benefits unchanged may at least partially explain <i>Avenella flexuosa</i> adaptation to grazing.
DOI: 10.6084/m9.figshare.28270567
title: The thermal structure of small and shallow Arctic Fennoscandian lakes

description: A continuous three-year field study, focusing on the thermal regime and the heat budget of twelve shallow Arctic lakes in northwest Finland, was conducted between 2019 and 2022. The results reveal diverse thermal regimes among these lakes, ranging from cold monomictic to discontinuous cold polymictic and dimictic patterns, reflecting the unique lake responses to their environmental settings. The heat budget of these lakes was predominantly influenced by the strong seasonality of the radiation balance, with latent and sensible heat fluxes consistently exhibiting negative values during the ice-free period, peaking in the summer or late fall. Air temperature and solar radiation were the primary drivers affecting lake thermal structures, at both local and regional scales. The influence of wind speed and cloudiness was more significant for lakes in the treeless tundra, but their regional impact remains relatively weak, along with the impact of precipitation. Additionally, we emphasize the critical role of lake location, geography, and morphology, and particularly altitude, lake size, and water column transparency, in determining changes in stratification and mixing dynamics, overshadowing the influence of lake depth. In conclusion, this study provides new insights into the evolving thermal dynamics of lakes in the European Arctic.
DOI: 10.6084/m9.figshare.28270567.v1
title: The thermal structure of small and shallow Arctic Fennoscandian lakes

description: A continuous three-year field study, focusing on the thermal regime and the heat budget of twelve shallow Arctic lakes in northwest Finland, was conducted between 2019 and 2022. The results reveal diverse thermal regimes among these lakes, ranging from cold monomictic to discontinuous cold polymictic and dimictic patterns, reflecting the unique lake responses to their environmental settings. The heat budget of these lakes was predominantly influenced by the strong seasonality of the radiation balance, with latent and sensible heat fluxes consistently exhibiting negative values during the ice-free period, peaking in the summer or late fall. Air temperature and solar radiation were the primary drivers affecting lake thermal structures, at both local and regional scales. The influence of wind speed and cloudiness was more significant for lakes in the treeless tundra, but their regional impact remains relatively weak, along with the impact of precipitation. Additionally, we emphasize the critical role of lake location, geography, and morphology, and particularly altitude, lake size, and water column transparency, in determining changes in stratification and mixing dynamics, overshadowing the influence of lake depth. In conclusion, this study provides new insights into the evolving thermal dynamics of lakes in the European Arctic.
DOI: 10.6084/m9.figshare.30418275
title: Geochemical evidence for the origin of late Quaternary loess, Seward Peninsula, Alaska

description: Loess is the most widespread surficial deposit in the state of Alaska. Although loess of last glacial age is common in mid-continental North America, records of last glacial loess in Alaska have been elusive. Here we report a record of last glacial loess on the Seward Peninsula, along with studies of a transect of loess localities also thought to date to the last glacial period. Highly diverse hypotheses on the origin of loess on the Seward Peninsula include local volcanic rocks and mountain ranges to the north and south, as well as offshore deposits. We present particle size and mineralogical and geochemical data that indicate that the most likely sources for loess in this part of eastern Beringia are glaciogenic silt particles of the Kobuk River and Noatak River, both of which drain the Brooks Range to the northeast. Northeasterly paleowinds were therefore responsible for loess on the Seward Peninsula. Such winds probably occurred during late summer or early autumn, when river discharge was at a minimum but temperatures were still above freezing. Northeasterly winds during the last glacial period are in good agreement with a recent paleoclimate model.
DOI: 10.6084/m9.figshare.30418275.v1
title: Geochemical evidence for the origin of late Quaternary loess, Seward Peninsula, Alaska

description: Loess is the most widespread surficial deposit in the state of Alaska. Although loess of last glacial age is common in mid-continental North America, records of last glacial loess in Alaska have been elusive. Here we report a record of last glacial loess on the Seward Peninsula, along with studies of a transect of loess localities also thought to date to the last glacial period. Highly diverse hypotheses on the origin of loess on the Seward Peninsula include local volcanic rocks and mountain ranges to the north and south, as well as offshore deposits. We present particle size and mineralogical and geochemical data that indicate that the most likely sources for loess in this part of eastern Beringia are glaciogenic silt particles of the Kobuk River and Noatak River, both of which drain the Brooks Range to the northeast. Northeasterly paleowinds were therefore responsible for loess on the Seward Peninsula. Such winds probably occurred during late summer or early autumn, when river discharge was at a minimum but temperatures were still above freezing. Northeasterly winds during the last glacial period are in good agreement with a recent paleoclimate model.