Forests play a critical role in carbon storage and actively mitigate climate change. By fostering biodiversity they offer further intrinsic and economic value through ecosystem functions and services. However, logging and the increasing frequency and intensity of wildfires and pest outbreaks pose significant disturbances to forests. Understanding the interactions between forest cover, biodiversity, and disturbance is essential for determining effective strategies for forest management and conservation. 

To investigate past dynamics in diversity and forest cover, we utilized pollen-based vegetation reconstructions for the Northern Hemisphere over the past 10 000 years. We derived richness and forest cover and computed metrics for forest cover trends, centennial forest cover variability, and disturbance frequency and intensity. We analyzed the relationship of these potential drivers and forest cover and richness using loess models and explored spatio-temporal patterns.

Our findings reveal a negative relationship of richness with forest cover, with maximum richness observed at low to intermediate forest cover values.This indicates a potential tradeoff between high forest cover for optimal carbon storage and high biodiversity. Richness also demonstrates a normal response to centennial forest cover variability, supporting the intermediate disturbance hypothesis. Interestingly, we also find that increasing the cumulative disturbance intensity increases richness. This indicates a positive effect on forest richness from both many small and few large disturbances. This highlights the potential of disturbances to increase and maintain biodiversity in temperate and boreal forest.
These findings could help with designing forest management and conservation measures that align with carbon storage and biodiversity goals.

How to cite: Schild, L. and Herzschuh, U.: Impacts of forest cover and disturbance on Holocene forest biodiversity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19277, https://doi.org/10.5194/egusphere-egu24-19277, 2024.

European landscapes have known a variety of transformations through the Holocene as a consequence of large-scale climate changes and anthropogenic impact. Recent evolution of the European area has seen a recession of agriculture in several regions (e.g. Navarro & Pereira, 2012, Ecosystems ; Perpiña Castillo et al, 2018, European Commission) putting into question what is to happen to the land so abandoned (Fayet et al, 2022 Environmental Science & Policy), for example if more « natural » conditions are to be implemented.

During the Holocene, European forests evolved in response to both climatic and human pressure. This joint evolution makes it hard to understand what the rôle of each factor is. Recent simulations at the global scale show that there could be significant delay between the natural vegetation evolution as computed in climate models and the observed evolution as recorded in palynological assemblages (Dallmeyer et al., 2023).

We aim at exploring the effect of human and climatic impacts on the vegetation evolution in Europe during the Holocene by means of high spatial resolution modelling.

To better understand how human pressure impacted vegetation cover in Europe, initial DGVM simulations were conducted using SEIB model, and were compared to pollen-based reconstruction from the REVEALS database. That way, the difference between simulations (representing european vegetation cover without homo sapiens presence) and data (representing real european vegetation cover) are a mean to evaluate the extent of the human impact. The simulations were running using climatic inputs from the intermediate complexity climatic model iLOVECLIM, using a downscaling approach to increase the spatial resolution and a bias correction method to improve the climate representation over the european area. Using steps of 300 years time windows periods from the begining of the Holocene to the preindustrial period, we present the results of those simulations and the comparaison with the pollen database as well as comparison with another vegetation model to assess the inter-model dispertion. The outcome could help us understand how our species has shaped the lands even before agricultural times as well as the extent of the climate induced vegetation evolution.

References

Navarro, L.M., Pereira, H.M. Rewilding Abandoned Landscapes in Europe. Ecosystems 15, 900–912 (2012). https://doi.org/10.1007/s10021-012-9558-7

Perpiña Castillo, C., Kavalov, B., Diogo, V., Jacobs-Crisioni, C., Batista e Silva, F., Lavalle, C, Agricultural land abandonment in the EU within 2015-2030, JRC113718, European Commission 2018

Fayet, C., Reilly, K., Van Ham, C., Verburg, P. H. (2022) The potential of European abandoned agricultural lands to contribute to the Green Deal objectives: Policy perspectives, Environmental Science & Policy, Volume 133, pages 44-53.

Dallmeyer, A, Kleinen, T, et al The deglacial forest conundrum, Nature Communications, 2022 https://doi.org/10.1038/s41467-022-33646-6

How to cite: Bertrix, I. A., Viovy, N., Sato, H., and Roche, D. M.: Holocene Integrative Vegetation Evolution (HIVE) : dynamical modelling under transient climate conditions in Europe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16394, https://doi.org/10.5194/egusphere-egu24-16394, 2024.

The terrestrial vegetation plays a crucial role in co-regulating global energy, water, carbon, and nutrient cycles. Shifts in vegetation, including changes in forest and peatland areas as well as species distribution, contribute to the large uncertainties in terrestrial ecosystems and their services under increasing disturbances caused by anthropogenic climate change.

To comprehensively assess vegetation responses and feedback to perturbations, particularly regarding carbon-nitrogen cycles and greenhouse gas exchanges, modelling efforts are indispensable. For instance, dynamical vegetation models can be exploited to investigate the terrestrial biogeochemical processes under past climate changes, such as glacial-interglacial transitions. However, such efforts often remain limited by the computational demands of complex Earth system models that struggle to capture multi-millennial timescales, which is further exacerbated by the challenges associated with model validation, leaving the long-term terrestrial vegetation dynamics largely under-constrained.

Here we employ the LPX-Bern model, a cost-efficient Dynamic Global Vegetation Model of intermediate complexity with fully coupled water, carbon, and nitrogen cycles, and present the results for simulations since the last interglacial. We critically evaluate the current model configuration, validated for pre-industrial to present-day conditions, for the last glacial cycle. The challenges in applying the model to these past times, such as the knowledge gaps in process representation, limited data availability for validation, and the limitations in model parameterisations, are addressed. The implications from simulating such long timescales and potentials to enhance the terrestrial biogeochemical processes in DGVMs are discussed. This study thus aims to contribute to advancing model development in carbon-nitrogen cycles for improved future climate projections.

How to cite: Sun, Q. and Joos, F.: Modelling terrestrial vegetation dynamics and carbon-nitrogen cycles over the last glacial using LPX-Bern, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10571, https://doi.org/10.5194/egusphere-egu24-10571, 2024.

Deep-sea pollen records from the Western European margin indicate that regional vegetation oscillated between open forest and steppe during the Last Glacial period (ca. 115-27 ka), in response to the millennial scale climate variability, specifically the Dansgaard-Oeschger, (D-O) cycles and Heinrich events (HE). The magnitude of the forest expansions during D-O warming events was modulated by orbital parameters. However, the vegetation response in the north-western Mediterranean region during this period remains poorly understood due to the fragmentary nature of the available sequences.

In this study, we present a new well-chronologically constrained high-resolution marine pollen record from the Gulf of Lion (MD99-2343, 40°29'N, 4°01'E) documenting the vegetation response in southeastern France during Marine Isotope Stages (MIS) 4 to 2 (ca. 73-27 ka). Initial findings highlight that the extent of the temperate forest expansions in SE France, i.e. the forest colonizing the Rhône valley, in response to D-Os warming events is modulated by precession, as previously indicated by Western European margin pollen records located in the Mediterranean region below 40°N. In Western Europe, the HEs are all characterized by steppe expansions, but the new pollen analysis documents another scenario with an increase in forest cover during HE 6. We hypothesize that the combination of minima in precession and local atmospheric and marine processes in the Gulf of Lion allowed the development of the temperate forest in SE France during HE 6, while the expansion of open environments occurred in Western Europe.

How to cite: Fourcade, T., Sanchez Goñi, M. F., Lesven, J., Lahaye, C., and Philippe, A.: Vegetation response in SE France to the millennial-scale climate variability of the last glacial period, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15920, https://doi.org/10.5194/egusphere-egu24-15920, 2024.

Across the northern East-European Plain, and especially in the Mologa-Sheksna Lowland (MSL), short-term climate variability in the Late Glacial caused significant palaeohydrological alterations, which drove vegetation successions. The MSL is prominent for the dense river and lake network, which have evolved through multiple water level and sedimentation regime oscillations since the Last Glacial Maximum. Extensive bogs inherit morphology of the basins, which had been filled with paleolakes for several millennia until their ultimate drainage in the early Holocene. Correspondingly, intricate morphology of lakes and deltas conditioned mosaic distribution of vegetation across the MSL.

Continuous palaeoenvironmental record for the Holocene in the MSL has been derived from several peat and lacustrine sites. The data regarding the Late Glacial is much more scarce, due to the low abundance of the relevant deposits, and poor state of preservation. Except for the MSL bog plains, pronounced evidence for the short-term palaeoenvironmental offset was discovered in the section of the sand terraces in the Mologa River catchment. The onset of Allerød warming has been traced via an organomineral layer, which was confirmed to have a continuous bedding over the area of 100 km² in the central MSL, as revealed by auger drilling and ground-penetrating radar survey at eight sites. This layer dates back to 13.4– 12.1 cal ka BP, and is represented by interbedding of fine sand with medium decomposed peat. Palynological and plant macrofossil studies of the buried peat from three boreholes reveal several inferences about the formation of this layer and the general palaeohydrology of the MSL in the Late Glacial.

The first palaeoclimatic evidence is provided by the high abundance of spruce pollen and bark pieces, supporting the hypothesis that the layer formation occurred during the Allerød interstadial, which was characterized by a rapid expansion of spruce in the region. Secondly, high abundances of pollen and remains of hydrophytes or hydrophilous lacustrine vascular plants (Cyperaceae, Poaceae, Potamogetonaceae), mosses (Sphagnum sp., Drepanocladus aduncus and Calliergonella cuspidatum) and chara algae indicate lentic shallow water environment or the proximity of the paleolake shoreline. In general, a transition from shallow lacustrine environments, surrounded by spruce-birch forests, to tundra steppes and bogged grasslands can be deduced, based on the pollen spectra and subfossils assemblages. Third, true altitude of the buried peat layer (96.5 – 102.5 m above sea level) may be considered as a limit for the paleolake water level in the Allerød, because it delineates the surface uncovered from water or proximate to the shoreline. Thus, its lowermost discovered position can trace the extent to which the paleolake level had dropped in the Allerød. The peat was rapidly formed and buried during the late Allerød, which makes it a reliable regional isochronous stratigraphic level for the poorly studied Late Glacial sedimentary successions. This level can be used as a reference point for tracing recent short-term climate-environment interactions and effects.

How to cite: Sadokov, D., Kostromina, N., Mazei, N., Bobrov, N., Ding, P., Petrov, A., Savelieva, L., Ruchkin, M., Kuznetsov, A., Tsyganov, A., and Mazei, Y.: Allerød interstadial vegetation and lacustrine palaeoenvironment of the central Mologa-Sheksna Lowland (East-European Plain), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12877, https://doi.org/10.5194/egusphere-egu24-12877, 2024.

Investigations of past biotic responses to rapid climate shifts are useful for developing biological scenarios that may result from future climate change. Vegetation responses to the Younger Dryas (YD) cold climatic reversal, the 8.2 ka cooling event, and the 4.2 ka event are of considerable interest. In this paper, we conduct model simulations of vegetation responses to these rapid climate changes over East Asia, and compare them with pollen-based vegetation records. Our aims were to investigate the vegetation responses to rapid climate changes with different magnitudes and to analyze dominant impact factors on vegetation in East Asia. Our results reveal that all major Plant Functional Types responded to the climate changes, but the magnitude, timing, and impact of their responses varied, with most changes in vegetation composition rather than vegetation type succession. In addition, it was found that after the abrupt cooling events the vegetation did not always recover to the state simulated before the perturbation, suggesting that different vegetation compositions may occur under similar climate conditions. Notably, there was a latitudinal gradient in the magnitude of these cold events in East Asia and in the resulting vegetation response, indicating a more pronounced vegetation responses to the severe cooling in the north and weaker responses to less cooling in the south. Changes in temperature exerted a major influence on the vegetation dynamics in the most high latitude regions, and changes in both temperature and precipitation were responsible for the vegetation changes at mid-to-high-latitudes. Vegetation compositions show a long-lasting effect of abrupt climate changes through eco-physiological and ecosystem demographic processes.

How to cite: Li, H., Chen, C., Zhao, W., and Zhao, Y.: Vegetation responses in East Asia to rapid climate changes: comparisons among the Younger Dryas event, the 8.2ka event, and the 4.2ka event, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15834, https://doi.org/10.5194/egusphere-egu24-15834, 2024.

The vegetation carbon uptake plays an important role in the terrestrial carbon cycle on the Qinghai–Tibet Plateau (QTP), while it is extremely sensitive to the impact of natural external forcings. Until now, there is limited knowledge on the spatial-temporal patterns of vegetation net carbon uptake (VNCU) after the force that caused by tropical volcanic eruptions. Here, we conducted an exhaustive reconstruction of VNCU on the QTP over the last millennium, and used a superposed epoch analysis to characterize the VNCU response of the QTP after the tropical volcanic eruptions. We then further investigated the divergent changes of VNCU response across different elevation gradients and vegetation types, and the impact of teleconnection forcing on VNCU after volcanic eruptions. Within a climatic background, we found that VNCU of the QTP tends to decrease after large volcanic eruptions, lasting until about 3 years, with a maximum decrease value occurring in the following 1 year. The spatial and temporal patterns of the VNCU were mainly driven by the post-eruption climate and moderated by the negative phase trends of El Niño-Southern Oscillation and the Atlantic multidecadal oscillation. In addition, elevation and vegetation types were undeniable driving forces associated with VNCU on QTP. Different water-heat conditions and vegetation types contributed to significant differences in the response and recovery processes of VNCU. Our results emphasized the response and recovery processes of VNCU to volcanic eruptions without the strong anthropogenic forcings, while the influence mechanisms of natural forcing on VNCU should receive more attention.

How to cite: Yong, Z., Wang, Z., Xiong, J., and Tian, J.: Tropical volcanic eruptions reduce vegetation net carbon uptake on the Qinghai–Tibet Plateau under background climate conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5912, https://doi.org/10.5194/egusphere-egu24-5912, 2024.

The Holocene temperature conundrum, marked by inconsistencies between proxy-based reconstructions and transient model simulations, challenges our understanding of Holocene temperature evolution. Reconstructions suggest a cooling trend after the Holocene Thermal Maximum, while model simulations indicate a consistent warming trend due to ice-sheet retreat and rising greenhouse gas concentrations. Various factors, such as seasonal biases and overlooked feedback processes, have been proposed as potential causes for this discrepancy. In this study, we found the impact of vegetation-climate feedback on temperature anomaly patterns in East Asia during the mid-Holocene (6000 BP). By utilizing the fully coupled Earth system model EC-Earth and performing simulations with and without coupled dynamic vegetation, we aim to isolate the influence of vegetation changes on regional temperature patterns. Our findings reveal that vegetation-climate feedback contributed to warming across most of East Asia, resulting in spatially diverse temperature changes during the mid-Holocene and significantly enhanced the model-data agreement. These results highlight the crucial role of vegetation-climate feedback in addressing the Holocene temperature conundrum and emphasize its importance for simulating accurate climate scenarios.

How to cite: Chen, J.: Reconciling East Asia's mid-Holocene temperature discrepancy through vegetation-climate feedback, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4255, https://doi.org/10.5194/egusphere-egu24-4255, 2024.

Global climate change is projected to lead to an expansion of wildfire-prone regions coupled with increase in fire frequency and intensity. In the Western US the characteristic fire season has changed considerably in recent years. Notably, there has been an observed doubling of autumn fire activity, an increase in the occurrence and duration of extreme fire weather conditions, and an intensification of wildfire severity. This trend is expected to persist and intensify with increased warming. For California (CA), climate models predict minimal changes to mean annual precipitation, but a substantial increase in climate volatility on the decadal and sub-centennial scale. This volatility manifests as persistent droughts interrupted by pluvial episodes, creating what is referred to as a 'whiplash climate.' However, predicting how the wildfire regime in CA will evolve with increased climate volatility remains a challenging task.

StalFire is multi-lab collaborative framework (consortium) established to facilitate research focused on utilizing paleoclimate data archived in stalagmites. The primary goal is to provide new insights into paleo-wildfires, with a specific emphasis on assessing the paleoclimate-wildfire relationship in CA across multiple timescales and under different climate states. Drawing upon over a decade of monitoring and stalagmite record development in CA caves exposed to significant fires, this consortium project is guided four research objectives: (1) Monitoring tracer evolution across karst systems to improve conventional proxies and expand the understanding and application of promising new qualitative hydroclimate proxies and fire tracers. (2) Developing aquantified representation  — a forward proxy system model — of the conditions and processes that govern the different proxy signals of past hydroclimate and fire behavior in stalagmites. (3) Expanding and improving existing CA multi-proxy records for stalagmites representing transects of the north-south climate dipole extending from coastal to Sierra Nevada regions. 4) Conducting site-specific to regional proxy-model comparisons and providing quantitative reconstructions of hydroclimate and fire activity in CA over the past 70,000 years. 

We provide a summary of initial results of the StalFire Consortium that focus on developing a 'surface-to-stalagmite' understanding of hydroclimate and fire tracers through monitoring coupled with proxy development (d⁴⁴Ca, fluid inclusion water isotopes, dual clumped isotope, and plant/microbial biomarkers, biomass burning-derived organic molecules like anhydrosugars and polycyclic aromatic hydrocarbons). Finally, we aim for this presentation to encourage discussion among researchers, labs, and work groups involved in paleo-fire coupled with hydroclimate research, from method development to paleorecord analysis.

How to cite: Montañez, I. P., Oster, J. L., Atekwana, E. A., Bowen, G., Burstyn, Y., de Wet, C., Griffith, E. M., Hren, M., Letshele, K. P., Pederzani, S., Scarpitti, E. A., Smolen, J., Wang, Z., and Zyba, A.: StalFire Consortium: Defining the paleoclimate-fire relationship in California across temporal and spatial scales , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13457, https://doi.org/10.5194/egusphere-egu24-13457, 2024.

The southern European Alps are currently suffering from serious drought conditions and wildfires due to climate change. For this reason, paleoenvironmental research is fundamental in this vulnerable region to better understand the interactions between climate, humans, and landscape in the past, which are still largely unknown. Therefore, we established an 8 ka sediment record from Lago di Pusiano in the Brianza region (northern Italy) to reconstruct previous drought and wildfire dynamics since the Neolithic period using biomarker analyses. Specifically, besides well-established geochemical analyses, we use compound-specific hydrogen isotope analyses (δ²H) of n-alkanes to reconstruct hydroclimatic conditions and polycyclic aromatic hydrocarbons (PAHs) to reconstruct fire activities.

Our results show that δ²Hof the terrestrial n‑C₂₉ and n-C₃₁, which both reflect the δ²H signal of the growing season precipitation, is enriched during the Mid Holocene (~8 to 4.2 cal. ka BP), depleted from ~4.2 to 2.5 cal. ka BP and enriched from ~2.5 to 0.4 cal. ka BP. On longer timescales, we interpret our terrestrial δ²H to reflect the isolation-driven temperature change due to northern hemispheric cooling, showing an ongoing depletion in δ²H from the Mid to Late Holocene. However, on shorter timescales, especially during the Late Holocene, terrestrial δ²H can be overprinted by changes in the moisture source of precipitation, which are mostly related to the North Atlantic Oscillation (NAO) and the position of the Westerlies. Compared to the terrestrial n-alkanes, δ²H of the aquatic n‑C₂₅, which reflects the δ²H signal of lake water, is generally more enriched due to lake water evaporation. Consequently, the offset between aquatic and terrestrial δ²H gives a valuable indication about evaporation at Lago di Pusiano and indicates wetter conditions during phases of enriched terrestrial δ²H and dryer conditions during depleted terrestrial δ²H.

PAHs are abundant throughout the sediment core and increase during periods of higher regional human activity (e.g., Bronze Age pile dwellings ~4 cal. ka, Roman settlements ~2 cal. ka, and during Medieval times ~1 cal. ka), especially strongly during industrialization. The occurrence of PAHs in the Pusiano sediments, especially the large amount of high molecular PAHs, indicates significant local fire episodes with biomass combustion at high burning temperatures. The comparison of PAHs and δ²H of n‑alkanes suggests the presence of increased fire activities during wetter periods, possibly due to higher biomass availability as fuel for more extensive wildfires, and/or increased anthropogenic burning due to increased human presence during wetter periods.

How to cite: Danius, L., Strobel, P., Prochnow, M., Zech, R., and Bliedtner, M.: An 8 ka record of drought and fire dynamics in the southern European Alps based on biomarker analyses , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15781, https://doi.org/10.5194/egusphere-egu24-15781, 2024.

Charcoal has been the first choice when studying paleofire and related ecosystem disturbances over decades, because it can be easily obtained, for example, together with pollen. It is used to track changes in local versus regional fire activity (e.g., Vachula et al., 2018; Vachula, 2021, Paleo3). However, despite many progresses in charcoal analyses, specific information about paleofires such as fire intensity partly remains elusive, although such information is highly interesting particularly for archaeological sites where human impacts are expected.

Moossee is a small lake located near Bern (Switzerland) and is a key site to study past interactions between environment and human impacts because the presence of humans is documented at the site by lake pile dwellings since the Neolithic ~7 kyr ago. Moreover, the sedimentary record of this lake covers the last 19 kyr, has an excellent chronological control, and was already extensively studied by pollen and charcoal analyses at high temporal resolution.

We present first results of polycyclic aromatic hydrocarbons (PAHs) in the Moossee sediments covering the Mid and Late Holocene in 30-year resolution. PAHs are a relatively new, innovative proxy showing great potential to investigate fire characteristics and to corroborate charcoal data, since their composition varies depending on multiple factors, such as combustion temperature, intensity, and distance.

Our newly obtained PAH dataset generally agrees with the existing charcoal record from Moossee, although the PAH concentrations reveal a stronger variability in paleofires especially during pre-Roman times (i.e., prior to ~2500 cal. yr BP) where charcoal concentrations are low. However, we find high PAH concentrations during Late Iron Age (~2200 cal. yr BP) coinciding with higher charcoal concentrations related to the founding of a settlement at Bern. PAHs are dominated by low molecular weight compounds (molecular mass 152 to 202) until ~1300 cal. yr BP. The predominance of light PAHs together with low microscopic charcoal concentrations likely indicates local fire activity. This is also supported by new spatial calibrations suggesting that the distribution of light PAHs is spatially rather limited (Vachula et al., 2022, Paleo3). With the beginning of the Middle Ages (~1300 cal. yr BP), high molecular weight PAHs (molecular mass 252 to 278) are dominant documenting higher burning temperatures and increasing regional fire intensity, which is in line with increased charcoal influx. This coincides with increasing human impact across the Swiss Plateau. A massive increase of PAHs with a simultaneous drop in charcoal concentrations since 150 cal. yr BP can be attributed to the industrialization and the combustion of fossil fuels.

In conclusion, our preliminary high-resolution PAH dataset from Moossee provides valuable new information that are only partly recorded by the already existing charcoal and pollen data. Thus, PAHs have great potential for studying paleofire history at Moossee, although more evaluation of the PAHs and their differences to charcoal is necessary. During the upcoming months, we will extend this PAH dataset with high-resolution compound-specific deuterium analyses on leaf waxes to further investigate links between hydroclimatic dynamics, environmental changes and the presence of paleofires at Moossee.

How to cite: Rittmeier, L., Prochnow, M., Strobel, P., Bliedtner, M., Rey, F., Tinner, W., and Zech, R.: Refining Holocene environmental change and human impacts at Moossee, Switzerland, by exploring polycyclic aromatic hydrocarbons as innovative proxies for paleofire, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16656, https://doi.org/10.5194/egusphere-egu24-16656, 2024.

Peatlands are important ecosystems for carbon storage, storing an estimated 25-30% of global soil carbon despite covering just 3% of Earth’s terrestrial surface. These ecosystems are under increasing pressure due to human activity and climate change, which threaten to turn peatlands from being carbon stores to sources. Human activities such as peat draining are extremely damaging to peatland hydrology, and fire was often used by people as a tool for land management clearance in the past. Fire is one of the foremost forces impacting peatlands, as it destroys surface peat and the subsequent release of stored carbon. Fire frequency is predicted to increase due to more frequent and severe droughts in some areas, and increasing human activity in areas where peat can form (particularly in the Northern Hemisphere). These trends, if realised, can accelerate climate warming as previously stored carbon is released into the atmosphere.

The focus of this study, Mustjärve bog, is an ombrotrophic peat bog located in northwest Estonia. Our project aims to assess changes in peatland fire regimes, vegetation dynamics, and hydrology to evaluate how the resilience of the site has changed over time within the context of relative changes in climate and human activity. A peat core was analysed using multiple palaeoecological proxies at high resolution (1 cm contiguous samples), to reconstruct past fire frequency, vegetation, and hydrological change over the past ~2500 years at the site. We also used historical data (population, past climate, and archaeological records) to better understand the drivers of changes uncovered in the palaeoecological record.

Our data reveals a distinct anthropogenic signal from ~700 CE onwards, coincident with increasing population and expanding land exploitation. Human activity from ~700 CE to ~1800 CE causes an increase in local fire events, culminating in lowered carbon accumulation rates, lowered water tables and higher peat bulk density. This trend continued until ~1950 CE, when there was a recovery in carbon accumulation and water table depth. Mustjärve’s vegetation history was predominantly Sphagnum, with Sphagnum Sect. Acutifolia indicative of drier conditions becoming much more prevalent from ca. 200 BC onwards, possibly owing to changes in water table depth. In the last 150 years, arboreal taxa such as Pinus sylvestris and Betula nana have encroached onto the bog, reflecting a decreasing water table and increased human activity that has impacted hydrological conditions, such as peat draining. We find little evidence for a significant climate influence on Mustjärve bog, as anthropogenic pressures on the site appear to dominate over the palaeoclimatic signal.

How to cite: Roberts, H., Andrews, L., Amon, L., Heinsalu, A., Kołaczek, P., Marcisz, K., Słowiński, M., Stivrins, N., Veski, S., and Lamentowicz, M.: Impact of human activity and fire on vegetation, hydrology, and carbon accumulation in Mustjärve bog, Northwest Estonia (PEATFLAMES), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8157, https://doi.org/10.5194/egusphere-egu24-8157, 2024.

Pollen analysis of the MAR03-02 core from the Aegean Sea (38°03.97'N, 26°22.30'E), western Türkiye allows us to reconstruct paleo-vegetation patterns and paleo-climate dynamics of the surrounding territory since the Late Glacial Period. We present palynological record from the topmost 2.8 m of a sediment core (MAR03-02) collected in the Aegean Sea, covering the last 20.7 ka. Variation in Mediterranean/temperate forests and herb/step plants indicates major climatic shifts connected to Heinrich Stadial 1, Bølling-Allerød, Younger Dryas, and the Holocene Climatic Optimum as well as some Rapid Climate Changes such as the 9.4, 8.2 and 5.9 ka events, Medieval Warm Period and Little Ice Age during the Holocene. In the cold and dry periods, low Arboreal Pollen (AP) and high amounts of herbaceous and steppe plants, including Artemisia, Cyperaceae, and Asteraceae Chichorioideae were recorded.  In warmer periods, high AP which was mainly characterized by deciduous Quercus, and low herbaceous/steppe plants dominated in the region. A warm-temperate and Mediterranean trees, consisted of mainly deciduous Quercus and Quercus ilex-type, reached the maximum level from the onset of the Holocene to 6 ka, which corresponded to the Holocene Climate Optimum. The pollen records show similarities with regional proxy records. Anthropogenic impacts occurred clearly during the last 2 ka when cultivated plants become prominent in the pollen records (e.g. Olea europea and Pistacia).

How to cite: Kolbüken, M., Biltekin, D., Aksu, A. E., Hiscott, R., Arıkan, B., and Yakupoğlu, N.: Vegetation and Climate Patterns of Western Türkiye since the Late Glacial Period Based on Pollen Records in the Aegean Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6575, https://doi.org/10.5194/egusphere-egu24-6575, 2024.

Dansgaard-Oeschger (D-O) cycles had profound impacts on climates of the northern hemisphere in the last glacial period. However, knowledge of terrestrial climatic responses in western North America and consequently vegetation responses to climatic extremes (e.g., highly variable paleohydroclimate and wildfire events) remains limited. Analysis of organic molecular traces (i.e., plant lipids and fire markers) in speleothems is one of the most promising ways to investigate feedbacks between climatic extremes and vegetation changes. Fire-derived markers, such as polyaromatic hydrocarbons (PAHs) and levoglucosan (LG), a derivative of plant cellulose burning, are increasingly applied as proxies of paleofires in speleothem records. Here, we present a new record of plant lipids, LG, and PAHs from a precisely dated and well-studied stalagmite (~55-67 ka) collected from McLean’s Cave (ML-2) in the Sierra Nevada foothills, CA (Oster et al. 2014). The variation of PAHs over the interval 62 to 67 ka corresponds with variations in stalagmite δ¹³C during the D-O stadials and interstadials 15-18. The highest concentration of low (≤ 4 rings) and high (≥ 5 rings) molecular weight PAHs as well as LG is found between ~64.25-63.75 ka, suggesting elevated wildfire events during D-O interstadial 18. Dehydroabietic acid (abietane-type acid) is predominantly produced from conifers, and its highest concentration occurs at 63.75 ka and then decreases from 63.5 to 62 ka. The study of modern plants (e.g., Kozłowska et al., 2022) shows that abietane-type acid accumulates at lower radiation and cooler climates and declines in heat and drought due to its antioxidative role in protecting cell membranes from stress-induced damage. The variation of dehydroabietic acid followed the changes in stalagmite δ¹³C between 64 and 62 ka (Oster et al., 2014), implying changes in coniferous input affected by the wet and dry cycles (D-O stadials and interstadial 18). This highlights the ability of organic molecular records archived in stalagmites to capture the links between wildfire activity, vegetation, and hydroclimate in central California during D-O cycles.   

Reference:

Kozłowska, W., Matkowski, A., Zielińska, S., 2022. Light Intensity and Temperature Effect on Salvia yangii (B. T. Drew) Metabolic Profile in vitro. Frontiers in Plant Science 13. https://doi.org/10.3389/fpls.2022.888509

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How to cite: Wang, Z., Smolen, J., Zyba, A., Scarpitti, E. A., Oster, J. L., Montañez, I. P., and Hren, M.: Variations of fire events and vegetation in the western Sierra Nevada archived in speleothems during Dansgaard–Oeschger (D–O) cycles , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11926, https://doi.org/10.5194/egusphere-egu24-11926, 2024.