Niina Kuosmanen

Aim: Theories on ecological stability lack the long‐term observational data necessary to comprehend the dynamics of durable and complex ecosystems like forests; consequently, the influence of biodiversity on ecosystem stability remains predominantly unexplained. This study examines the mechanisms of forest community and tree population change using long‐term palaeoecological data, evaluates responses to diverse effects, assesses stability and identifies the conditions that compelled these ecosystems to transition into alternative states. Furthermore, we aim to test whether higher diversity and larger populations promote stability. Location: Central Europe. Taxon: Tracheophytes (spore and pollen‐producing vascular plants). Methods: We analyse a 12,000‐year lacustrine sedimentary record from a mountain lake Černé jezero, located in a spruce‐dominated temperate mountain ecosystem in the Bohemian Forest of Central Europe, utilizing various proxies such as pollen, charcoal and geochemical data. We examined accumulation rates, ecological indices, and climatic and regression models to evaluate biodiversity, disturbances, rates of change, population stability and climate dynamics to identify the drivers of these changes. Results: Our findings indicate that species richness is negatively correlated with tree population stability. Furthermore, we discovered that tree population growth does not always facilitate stability as theorized. Main Conclusions: As mountain forests encounter escalating pressures from climate change and anthropogenic influences, our findings suggest that competition and turnover among species can undermine tree population‐level resilience. Our results also emphasize the necessity of preserving species diversity while acknowledging the potential emerging threats to forest population stability.

Palsa mires are located at the southern border of the permafrost region. Rising temperatures have led to widespread permafrost thaw and rapid palsa and peat plateau degradation. Palsa mires store significant amounts of carbon (C), which is released when permafrost thaws, potentially changing the peatlands from long-term C sinks to temporary C sources. To improve predictions of how palsa mires will respond to ongoing climate change, a better understanding of their past dynamics is vital. Here, we reconstruct the permafrost history of a peat plateau in Karlebotn, northern Norway, using a multiproxy approach. A peat profile was dated by accelerator mass spectrometry radiocarbon method, and analyzed for oribatid mite communities, peat type and peat properties. Oribatid mite analysis is a relatively novel method suggested as a proxy for permafrost initiation. Here, we compared it to more established approaches based on peat characteristics and vegetation changes. Our results suggest that gradual permafrost aggradation at the site began after ca. 1000 calibrated years Before Present (cal year BP; present = 1950 AD) with stable permafrost conditions established by ca. 400 cal year BP. Three peatland succession phases were identified: the first wet fen phase, a transitional phase with wet and dry condition taxa and the last phase dominated by species typical of dry and permafrost-associated conditions. Our results show that integrating oribatid mite analysis into paleoecological studies offers a more robust reconstruction of past permafrost dynamics, thereby enhancing our understanding of the past, present and future development of palsa mires.

Groundwater-influenced, nutrient-rich sloping fens are characteristic of northeastern Finland, where they are affected by both groundwater discharge and surface water inputs, including spring floods. This study examines the geochemical composition of peat pore water in Puukkosuo, a sloping fen underlain by carbonate bedrock, with two objectives: (1) to evaluate the influence of groundwater discharge on peat hydrogeochemistry, and (2) to compare hydrochemical and geochemical signatures with those of northern boreal peatlands underlain by different bedrock types.The 3D structure of the peatland was modeled to understand flow paths within the Peatland basin (Åberg et al. 2025). Four peat cores were collected to characterize peat composition, humification, and geochemistry, alongside pore water samples from the same locations (Erhovaara 2023). Porewater samples from three locations from different depths were analyzed for trace elements, major ion composition, pH, EC, TOC, TC, IC, NO3+NO2, NH4, Tot N, Tot P, stable isotopic composition of water and δ13C (DIC ) to assess groundwater and bedrock influence. Additional surface and groundwater samples were analysed for trace elements and majos ion composition, pH and EC as a reference. High Ca and Mg concentrations, as well as high pH and EC in pore water indicate strong groundwater input, while elevated nutrient levels observed at the western edge of Puukkosuo primarily reflect surface runoff. Although the broader catchment lacks extensive carbonate deposits, the presence of carbonate bedrock beneath Puukkosuo, combined with its sloping morphology, demonstrates that groundwater flow paths significantly shape the hydrogeochemical conditions of the fen.Erhovaara, S., 2023. Carbon accumulation and peat geochemistry in the Puukkosuo fen during the Holocene. MSc. thesis, University of Helsinki. 45 p.Åberg, A., Nurmilaukas, O., Korkka-Niemi, K. & Kultti, S., 2025. Kuusamossa sijaitsevan Puukkosuon maatutkaluotaukseen perustuva 3D-mallinnus. Geological Survey of Finland. GTK Open File Work Report 40/2025. 24 p.

The declining popularity of geosciences in higher education (HE) globally has increased concern about an emerging skills gap in the geoscience workplace. Australia, Canada, the US, the UK, and Italy have observed a decline in graduates, enrolment, and/or applicant numbers of typically 20 to 40% in graduate/undergraduate geoscience programs since 2013. Geoscience educators tend to attribute these trends to negative public perception of geosciences in relation to environmental and climate change and general lack of awareness about societal relevance of the field.The opposite trend has been observed in Finland over the past eight years. Degree programmes in geology or geosciences in Finland have jointly experienced a total increase of ca. 70% both in applicant numbers (2020–2024) and enrolment (2015–2024). The Finnish geoscience education community coined the term “Finnish phenomenon” to describe these positive observations. However, the reasons behind these observations remain to be understood. As the overall applicant numbers to Finnish universities do not follow these trends, education system level effects can most likely be ruled out.This contribution explores some of the activities and changes in the Finnish geoscience higher education processes during the past ca. 10 years that could explain the “Finnish phenomenon”: 1. Changes in the Finnish HE admission systemIn 2015, the Finnish HE application process (joint application system) was transferred to the digital Studyinfo.fi-portal (https://opintopolku.fi/konfo/en/). Since 2022, all geoscience degree programmes have hosted a joint landing page within the portal to enhance the visibility of the field. 2. International Earth Science Olympiad (IESO) activitiesSince 2018, the visibility of geosciences in Finnish schools has been enhanced through the activities of the International Earth Science Olympiad (IESO). National IESO efforts coordinated through the Geological Society of Finland have increased the visibility of geosciences among students and led to success in the international competitions. 3. Upper secondary school collaboration in geosciencesGeosciences are not taught as a separate subject in Finnish upper secondary schools. Since 2020, secondary school collaboration has been systematically enhanced especially at the University of Helsinki through a working group that includes staff, students, City of Helsinki education services, and schoolteachers. 4. The FIN-GEO networkOne of the major joint efforts in the Finnish geoscience education community in recent years has been the FIN-GEO project funded by the Ministry of Education and Culture of Finland in 2021–2023. The FIN-GEO network significantly strengthened cooperation in the education of geosciences, utilizing the mutual research profiling of the parties in the development of educational offerings and the relevance of working life. The annual geoscience first-year questionnaire launched by the FIN-GEO network in 2022 has found that the Studyinfo.fi-portal alongside geoscience-specific media coverage and university webpages have been the most important sources of information for aspiring students. Further analysis of these results is ongoing, but combined the actions listed above appear to have positively affected interest in higher geoscience education, which could serve as a useful template elsewhere as well.

Boreal peatlands play a crucial role in global carbon dynamics as sinks and sources. Groundwater dependent nutrient rich sloping fen ecosystem is a typical morphological peatland type for northeastern Finland. To increase the understanding of the carbon dynamics of these ecosystems we investigate the long-term carbon accumulation pattern in sloping fen in the carbonate bedrock area in northern boreal zone. The study site Puukkosuo is a sloping fen situated in Oulanka in northern boreal zone in NE Finland. Four peat cores were obtained across the study site. All cores were radiocarbon dated for chronological control to calculate the peat accumulation rate. Peat characteristics (peat composition, humification degree, bulk density) and carbon content was analysed to investigate the development of the peatland and long-term carbon storage during the Holocene. The peat accumulation rate, based on radiocarbon dates, bulk density and carbon content were used to calculate the long-term carbon accumulation. To assess the role of basin bathymetry to peatland development and carbon storage, the 3D structure of the Puukkosuo basin was modelled with Leapfrog Geo (Seequent) program based on network of ground penetrating radar (GPR) profiles (5.5 km) across the peatland and reference peat stratigraphy. The records cover the last 9 000 cal yr BP of peatland development and carbon accumulation. The results suggests that the carbon accumulation rate in the basal part of the basin exceeds the average rate in the northern boreal zone, whereas the surface layer demonstrates typical carbon accumulation values. The changes in the accumulation rate are divergent between cores but occur at the same altitudinal level of the basin. Therefore, we conclude that here the bathymetry rather than the accumulation period controls the major carbon accumulation patterns. These results will be further discussed in the presentation.

Palsa mires are located at the southern border of the permafrost zone making them highly sensitive to climate warming. When annual temperature and precipitation conditions are optimal, palsas form and collapse in a natural cycle. However, due to current climate warming, permafrost is widely thawing and palsas are degrading rapidly. In addition to being unique and valuable habitats for many species, palsas store significant amount of ancient carbon (C), which is released by reactivated decomposition processes when permafrost thaws, potentially changing the peatlands temporarily from C sinks to C sources. However, the age and extent of the C released remain uncertain. To predict how palsas will respond to ongoing climate change, understanding of the past dynamics is vital. In this study, we determined the permafrost aggradation date and reconstructed the past dynamics of a palsa in Karlebotn, northern Norway. A peat profile was radiocarbon (14C) dated, and oribatid mite analysis together with a peat type analysis and peat properties (C, nitrogen and bulk density) were performed. Oribatid mites are a diverse group of soil-living arthropods that have shown potential as environmental indicators. Recent findings suggest they can indicate the past initiation of permafrost.Our results suggest that gradual permafrost aggradation at the Karlebotn palsa began after 1500 calibrated years Before Present (cal yr BP; present = 1950 AD) and that at 700 cal yr BP the permafrost conditions had stabilized. Using multiproxy analysis, we identified three phases in the palsa history. The first phase was characterized by moist fen conditions, the second phase was a transition phase with wet and dry condition species occurring together and the last phase was dominated by species adapted to dry conditions, and which are typical in permafrost environments. Our data also indicate that during permafrost conditions, the C accumulation rate was lower than in the early non-permafrost fen stage. While permafrost thaw will temporarily increase C emissions, the C sink capacity may ultimately increase again as the peatland shifts back to a fen stage following ground subsidence.Only few palaeoecological studies exist from Fennoscandia where age of permafrost formation is determined. Most studies have used vegetation succession and peat properties to infer past permafrost presence, however, these methods are associated with uncertainties such as the absence of permafrost indicator plant species. This study provides additional data on historical palsa dynamics with a relatively robust chronology, based on multiple proxies, including oribatid mite community analysis. These findings contribute to our understanding of how palsas are responding to the ongoing and future climate change.

Palaeoecological studies reporting long-term development history of subarctic fens are scarce and overall permafrost-free peatlands located at the immediate vicinity of permafrost zone have deserved little attention in Fennoscandia. We use a multiproxy approach to study millennial-scale dynamics of two peatlands located in Finnish Lapland (Katsapuli and Maader). In addition to study autogenic succession and external forcing, we aimed in resolving the impact of surrounding landscape changes, potentially related to reindeer herding. The pollen data does not indicate major regional-scale vegetation changes but suggest an increase in the proportion of sedges towards modern times and decrease in tree pollen. These, together with an increase in regional fire events based on micro-charcoal and erosion rates measured as sediment mineral component coincide with both colder temperatures (Little Ice Age) and the emergence of reindeer-based pastoralism. The peat macrofossil data of the two profiles suggest a clear and relatively simultaneous local regime shift from sedge-dominated local habitat conditions to a Sphagnum community, where S. lindbergii becomes increasingly dominant towards the present day, suggesting prevalence of relatively moist conditions. In both sites, the regime shift is coeval with the onset of Medieval Climate Anomaly (MCA) climate conditions. Newly- established communities are sustained thereafter. Vegetation changes to Sphagnum mosses resulted in high peat growth rates, thus most of the peat stock is relatively new. Based on these data, we suggest that Sphagnum moss communities are resilient to climate fluctuations and might continue to act as effective carbon accumulation systems under warmer climates.

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants linked to multiple adverse impacts and they are ubiquitous in the Finnish aquatic environment. The Vantaa River watershed is densely populated and constitutes a reserve water source for water supply in the Helsinki Metropolitan area (1 million people). The aim of this research was to quantify PFAS concentrations and test a load estimator software (LOADEST) to determine loads at the mouth of Vantaa River before it flows into the Baltic Sea. Weekly water sampling was conducted near a continuous gauging station (Oulunkylä station) between March 2023 and October 2023 resulting in 28 samples. Water samples were analyzed for 50 PFAS in a commercial laboratory in Finland. Instantaneous daily load (riverine export) of individual and total PFAS (g/day) were calculated from the measured PFAS concentration in the river and daily river discharge data. The USGS application LOADEST was used to calculate individual and total PFAS loads at a daily interval over the monitoring period.Σ50 PFAS concentration averaged 25 ng/L (range was 7-53 ng/L) and Σ50 PFAS load averaged 27 g/day (range was 6-121 g/day). Six PFAS constituted 83,4% of total quantified PFAS, perfluorooctane sulphonic acid (PFOS) and perfluoropentane acid (PFPeA) accounted for 40%. The total Σ50PFAS load at Oulunkylä was 4,7 kg over the entire monitoring period (197 days). In addition, the PFAS yield (kg/km2 yr) calculated by dividing the annual PFAS load by the drainage area was 5.15 10-3 kg/km2 yr in Vantaa River. Statistical measures of model performance indicated that LOADEST models for Σ50PFAS was within acceptable limits, with a Load Bias of –0.5% and a Nash-Sutcliffe Efficiency Index of 0.9. Further monitoring and modeling are warranted as this study shows that LOADEST can successfully be applied to the Vantaa River watershed, and it could be used to track the PFAS load reaching the Baltic Sea and follow the evolution of the system after restriction or ban of individual PFAS in Europe.

Wildfires play a crucial role in northern boreal peatland ecosystems, influencing the functioning of these ecosystems by affecting vegetation composition and biomass, peat accumulation patterns, and soil carbon stocks. Northern peatland ecosystems are under pressure due to climate warming and increasing anthropogenic stress. The frequency and severity of wildfires is predicted to increase in the coming years. Therefore, understanding long-term natural fire dynamics and their effect on peatland functionality will provide crucial information for peatland management and preservation policies. To investigate the long-term fire history of Western Canada and its effect on peat accumulation and vegetation succession, we analyzed macroscopic plant remains and charcoal within peat cores taken from five peatlands in the region. Records of the most recent fire events were derived from fire scars and documented fires in the study area. Regional long-term peatland fire patterns were examined by pooling together macroscopic charcoal records and calculating 100 year moving averages. All studied sites, except the northernmost one, demonstrated repeated fires throughout the past 1500 years, suggesting that fires have been an integral part of the peatland ecosystem in Western Canada. Compiled charcoal records indicated a peak in fire activity, with the highest abundance of charcoal for the period from the 1300s to the 1550s and decreasing fire activity during recent centuries. The clear and consistent post-fire increase in the abundance of Sphagnum mosses suggests a relatively rapid recovery of peatland ecosystems after burning. The regeneration pattern, where pre-fire vegetation repeatedly re-establishes, suggests that from a long-term perspective, fires do not necessarily have a negative effect on peatland functioning and peat accumulation. In conclusion, peatlands could remain as effective carbon sinks if their natural state is secured.