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From Space to Soil: Revealing Environmental Water with Cosmic-Ray Neutron Sensing
No full textThe Cosmic-ray neutron sensing (CRNS) technique is a modern technological solution that facilitates continuous measurement of the average water content in the environment, including soil, snow, and vegetation. The sensor monitors an area of 10 to 15 hectares and soil depths up to 50 centimeters. This configuration enables the non-invasive and field-scale measurement of the soil water content or snow water equivalent that is insensitive to small-scale heterogeneities. The method has the potential to serve as an alternative to conventional in-situ sensors or costly soil or snow samples, while also demonstrating the capability to bridge the gap between point measurements and remote sensing data in both horizontal and vertical directions.The passive CRNS technology measures the natural cosmogenic background radiation and detects changes in the moderation of cosmic-ray induced fast neutrons by hydrogen atoms. The neutron radiation measured with CRNS originates primarily from high-energy cosmic rays that interact with nuclei in the Earth's atmosphere, producing secondary particles such as neutrons. These secondary neutrons penetrate the atmosphere and interact with the soil, where their moderation is influenced by the hydrogen content, including soil moisture. CRNS is flexible and robust because it operates non-invasively and requires no direct soil contact, making it suitable for diverse terrains and conditions. Additionally, it is largely unaffected by small-scale soil heterogeneity and provides continuous, real-time data with minimal maintenance. The CRNS can also be employed on mobile platforms for the purpose of on-demand soil moisture mapping at the field, regional, or even national scale. Presently, a network of CRNS stations being established on global scale, with several hundred sensors already in operation. In this presentation, we will examine recent experiments and prospective future applications of CRNS, with the objective of extending the boundaries of this technology
Restoration of a Degraded Raised Bog: Implications for Carbon Flux and Hydrological Recovery
No full textPeatlands are globally important carbon stores that provide a range of ecological, climatic, and socio-economic benefits. However, large-scale peat extraction, drainage for agriculture, and conversion to forestry have changed many peatlands from long-term carbon sinks into carbon sources. While some of the best remaining examples of intact raised bogs in Western Europe occur on the island of Ireland, a large majority are degraded. In recent years, Ireland has undertaken an extensive programme of peatland restoration, with works carried out across approximately 30,000 ha of drained raised bog to enhance biodiversity and contribute towards international greenhouse gas reduction commitments. Understanding the impacts of such restoration efforts on peatland hydrology, carbon dynamics, and biodiversity is essential to ensure that measures are effective and achieving the outcomes required. This study presents data from the restoration of a drained area of All Saints Bog, a Natura 2000 raised bog site. Restoration measures included ditch blocking, re-profiling degraded areas, and contour bund construction with adjustable drains to regulate the hydrology. The effects of restoration are evaluated using a combination of eddy covariance, chamber measurements, water level monitoring, and remote sensing over a four-year period from 2021 to 2024. This period incorporated one year of pre-restoration, two years of active restoration, and one year of post-restoration. Hydrologically, restoration efforts appear to have been successful, with widespread rewetting across much of the site, recreating the conditions for active peat formation and the slow recovery of Sphagnum moss locally present. However, we found an approximate two-fold increase in net carbon fluxes between pre- and post-restoration, rising from 1.14 t CO₂-C ha⁻¹ y⁻¹ in 2021 to 2.37 t CO₂-C ha⁻¹ y⁻¹ in 2024. Furthermore, chamber-based spatial measurements showed a higher emission contribution from contour bunds compared to bare peat. Consequently, a programme of Sphagnum translocation and inoculation is planned for 2025 to hasten vegetation recovery. This long-term investigation will deepen our understanding of effective restoration efforts, which will provide insights to guide the development of future restoration strategies
Contribution of emerging aquatic insects to lateral transfers of Carbon and Nutrients: significance for the integrated landscape budget along a gradient of agricultural pressure
No full textBiogeochemists usually consider the matter fluxes from land to streams and rivers and, no or negligible fluxes in the opposite direction. However, winged aquatic insects emerging from water bodies (e.g. lakes, ponds, perennial and ephemeral streams, wetlands) are recognized to provide nutritional subsidies to terrestrial consumers. Therefore, we hypothesized that nutrient (N, P) and carbon exports by emergent aquatic insects can be substantial to adjacent terrestrial ecosystems. Especially, we assumed these exports to increase with the density of the hydrographic network. Moreover, we advocate that the quantification of these lateral biotic fluxes of matter between terrestrial and aquatic ecosystems will improve element budgets at the landscape scale. We quantified these lateral fluxes to compare them to the input and output fluxes at the catchment scale for five sites along a gradient of agricultural intensification. The sites have different agricultural contexts and were selected within the French Long-Term Socio-Ecological Research network of Zones Ateliers (LTSER RZA, ZA Brest Iroise, Loire and Armorique). On each site, a headwater stream and its adjacent landscape were monitored for identification and quantification of emerging aquatic insects. Quantification of the corresponding biomass (abundance and diversity) relied on trapping insects using sticky traps at different distances from their aquatic sources during the emergence season. Input and output fluxes were determined for the smallest catchment nested within the sampling site for which agricultural and water quality data were available. Landscape features, agricultural pressures, and when available data on stream water quality were compared within nested catchments. Our results showed that in catchments with higher river nutrient exports due to agricultural activities, the stream network supplies relatively high production of emerging aquatic insects, which support a feedback flux of N and C to adjacent (0 to 100 m from source) terrestrial ecosystem
Demonstration in Ramon LTER site of the compensation hypothesis providing an alternative scenario to desertification
No full textClimate changes bring a new era in which hot dry areas become even hotter and drier. This leads to state shifts and specifically desertification processes. Desertification includes the state shifts from non-desert to deserts and within deserts reduction of primary productivity. Studying shifts in ecosystem states and desertification requires long term ecosystem research and monitoring (LTERM). This can take decades and because temporal variability of precipitation in deserts is very high, it is difficult to distinguish between noise and trends. Space for time substitution is a tool aiding LTER research. Specifically hyper-arid ecosystems (HAE), the driest deserts on earth, are a good tool to study possible scenarios of climate changes. Understanding structure and function of HAE allows us to imagine possible dynamics that can occur in wetter ecosystems.Our new assertion is that if extreme climate change drives arid lands to function under alternate extreme conditions, then arid land ecosystems will function like an HAE as an alternative state, rather than progress to desertification. To support our assertion, we developed a conceptual framework of HAEs that includes a geo-hydrological “abiotic engine” that drives HAE function by soil moisture diversity and plant functional groups. Based on this conceptual framework, we suggest incorporating two new hypotheses in climate change studies to advance our understanding of responses of large-scale, water-limited ecosystems:Hydro-climatic extremes in water-limited ecosystems will reduce the degree of resource conservation by slope ecosystems due to reduction in plant cover and soil. The decreased ecosystem function on the slope will be compensated for by increasing the effect of the abiotic engine on the ephemeral stream, thus enhancing meta-ecosystem functioning in the ephemeral stream.In water-limited ecosystems, climate change toward hydro-climatic extremes will rescale the dominant hydro-ecological processes of pulse–reserve, source–sink, and connectivity along the semiarid, arid, and HA gradients in two ways:shrinking of both spatial and temporal dimensions; and shrinking in the temporal dimension and expanding in the spatial dimensions.The first rescaling trajectory is related to biodiversity–ecosystem function and the second to the abiotic engine processes.The forecasted increased frequency and intensity of extreme climatic events may strongly affect ecosystem structure and function in the future. It is unclear how ecosystems will function in the long run over a large spatial scale under a new extreme water cycle. This open question calls for a conceptual framework as a fundamental basis for theoretical and experimental exploration of ecosystem function on a large scale driven by an extreme climate envelope. We investigated hyper-arid ecosystems (HAEs) as natural tangible models that already function under an extreme climatic envelope. The results indicate that unique geological settings can retain runoff water from a single significant flash flood that is sufficient to sustain perennials even during drought years. We calculated a water balance for a large rain event and found that 38% of the rain water infiltrated to the main riverbed which supports local trees, 46% exited the watershed to a larger river and only 19% were lost to either evaporation or the bare slopes. We propose a modified pulse–reserve mechanism that provides water to large acacia trees during the hot dry summer in hyperarid areas
Estimating patch-level fluxes from UAV measurements over a structured wetland through atmospheric inversion coupled to large-eddy simulations
No full textMany natural ecosystems are composed of heterogeneous patches differentiated by e.g., topography, wetness levels or vegetation composition. The resulting small-scale variability in surface-atmosphere exchange fluxes is hard to quantify, since small-scale observations like flux chambers are usually episodic, while larger-scale observations such as eddy-covariance towers integrate over larger footprints, and therefore produce an effective net flux of the mixed landscape. Approaches to decompose such an effective flux signal into patch-level component fluxes would allow to better understand control factors and mechanisms governing the flux rates, and therefore improve estimates of net fluxes, and potential flux trajectories under future climate.In this study, we combine high-resolution modelling of the atmospheric boundary layer with inverse modelling concepts to constrain land-atmosphere exchange fluxes at local to landscape scales, and explore relationships between different land cover types within heterogeneous landscapes and the net exchange processes between surface and atmosphere. We use EULAG (EUlerian LAGrangian), an established Large-Eddy Simulation model, to simulate high-resolution flow patterns induced by heterogeneous permafrost surfaces, and benchmark the spatial variability of modeled concentrations using data from uncrewed Aerial Vehicles (UAV)-based grid surveys of gas concentrations. We then optimize for surface fluxes associated with each patch by applying atmospheric inversion techniques.We present a case study at Stordalen Mire in subarctic Sweden, where we conducted UAV measurements of carbon dioxide mole fractions, and implement this inversion method to differentiate the flux rate signatures from different patch types. The inferred fluxes were subsequently validated with patch-level chamber measurements of carbon dioxide, showing a good match between modeled and observed concentrations. In addition, this method shows a potential in decomposing eddy-covariance fluxes into landcover fluxes, thus inferring flux budgets variability between patches. Our novel technique shows promising results in estimating patch type flux heterogeneity while facilitating the application of inversion methods to high resolution atmospheric models
Hydrologic and Ecological Consequences of Changing Snowmelt Patterns in the East River Catchment
No full textMountainous watersheds are increasingly experiencing snowpack decline and warmer winters. Several studies have shown that earlier and diminished snowpack alters streamflow and runoff dynamics while also affecting groundwater reserves. These changes in the hydrologic cycle —particularly early snowmelt and reduced snowpack—are hypothesized to disrupt coupled plant-microbial interactions, possibly due to the temporal discontinuity between microbial nutrient release and vegetation greening around the snowmelt period. This study aims to quantify how variations in snowmelt timing and snowpack depth influence nitrogen fluxes and plant phenology along a lower montane hillslope site in the East River catchment, Crested Butte, CO. Specifically, we compare nitrogen cycling and plant dynamics across three hydrologic conditions observed at the site: an average snow year (2016), a deep snowpack year (2017), and a sparse, early-melting snowpack year (2018). To achieve this, we developed a hillslope-to-floodplain transect model using ecosys — a comprehensive plant ecosystem model that integrates surface energy exchange, microbial metabolism, vegetation phenology/physiology, and lateral and vertical hydrologic and biogeochemical fluxes. Our results indicate that in low-snow years, surface soil water deficits suppress forb production while favoring deep-rooting shrubs, thereby altering vegetation nitrogen demand. In contrast, in high-snow years, soil and saprolite water availability extends into the monsoon season, sustaining forb growth. Furthermore, we find that monsoon timing and temperatures during the vernal window play a critical role in regulating plant productivity and the growing season length. Overall, these findings highlight the strong spatial and temporal linkages between snowmelt-driven nutrient release and plant phenology along the hillslope, underscoring the broader implications of shifting snow dynamics on watershed-scale ecosystem function
Carbon and Water Fluxes in a Temperate Scots Pine Chronosequence Study in Poland: An EC Measurement Story from an ICOS-Aspiring Country
No full textLong-term measurements of greenhouse gases, and consequently the carbon, water, and nitrogen cycles, have been the focus of numerous studies for decades. Currently, the most accurate and widely used method for real-time, spatially-averaged estimates of these fluxes is the eddy covariance technique (EC). Over time, individual sites across Europe have been integrated into the Integrated Carbon Observation System (ICOS), creating a network with standardized measurement and data processing protocols, thereby producing high-quality, directly comparable results. Since forests play a major role in the land CO2 sink both globally and in Europe, there is naturally a substantial number of forest EC sites within ICOS. However, there are still well-equipped research sites that, for various reasons, are not yet included in this network. A notable example is Poland, the ninth largest country in Europe by area (and seventh by population), which also marks the eastern border of the European Union.In this presentation, we aim to highlight the most interesting results from a network of Scots pine forest sites in Poland, which have been measuring EC CO2 and H2O fluxes for periods ranging from a few to over 10 years. The primary goal is not only to share the results of our analysis but also to explore new collaboration opportunities with the eLTER network to fully utilize the potential of our sites beyond greenhouse gas fluxes.To provide context for why Scots pine (Pinus sylvestris) was chosen for the Polish network, it is the most widespread pine species globally and the second most distributed conifer after the common juniper (Juniperus communis). Its natural Euro-Asian range spans vast areas, and in Poland, Scots pine dominates 58.6% of the total forest area. Additionally, the mean age of Scots pine trees in Poland is 62 years, meaning that most of them are mature stands. After several years of continuous EC and basic meteorological measurements, complemented by carbon stock inventories in soil and biomass, we addressed the following research questions:What is the nature of the relationship between the age of temperate, managed Scots pine stands, and their sequestration abilities (chronosequence approach)? At what age do these stands reach their maximum sequestration potential?Does the classic forest inventory-based carbon accumulation in woody biomass align with the EC-derived Net Ecosystem Exchange estimates at both annual (based on dendrometers) and multiannual (forest inventory) scales?Additional questions related specifically to the impact of different forest management practices on the carbon budget of temperate Scots pine forests were also explored and will be discussed here.In conclusion, although the presented Scots pine EC sites are not yet part of ICOS, the results may be of significant interest to other forest site Principal Investigators (PIs) in this network. This comprehensive, long-term dataset on carbon and water flux exchange between the atmosphere and one of Europe’s most common forest tree species holds relevance not only for climate-related impacts but also for socio-economic factors, as Scots pine is a crucial wood source species
Behind the Spatio-Temporal Variation in Spectral Chlorophyll Fluorescence of Boreal Species
No full textBoreal forests constitute about one-third of all the global forest area (Brandt et al. 2013). Capturing a significant portion of global atmospheric CO2 (Beer et al. 2010, Thurner et al. 2016, Thurner et al. 2013), boreal forests play a key role in the global carbon cycle (Anav et al. 2015). However, monitoring photosynthetic activity in these forests is difficult with traditional greenness or vegetation indices, particularly due to the dominance of evergreen species and thus relatively little seasonal variation in greenness (Magney et al. 2019). Fortunately, emerging studies suggest that chlorophyll-a fluorescence (ChlF) can improve our ability to track photosynthetic processes in evergreen-dominated ecosystems (Walther et al. 2016, Magney et al. 2019). However, the relationship between ChlF and photosynthesis (or at a larger scale, between Sun-Induced Fluorescence, SIF, and gross primary productivity, GPP) is dependent on various factors, both physical and physiological. Therefore, to fully interpret the information provided by ChlF, it is crucial to develop a thorough understanding and quantitative framework of the mechanisms linking ChlF measurements to photosynthesis at various scales.In our study performed at SMEAR-II Hyytälä forestry field station (61⁰ 31’ North 24⁰17’ East, southern Finland) and published in 2023 (Rajewicz et al. 2023), we established what factors affected spatial variation in spectral ChlF among leaves in a boreal forest and whether these effects vary over time (spring recovery of photosynthesis). Simultaneously, we also established what factors affect temporal variation in spectral ChlF and whether these effects differ between species and across the canopy light gradient (different canopy positions).We investigated a range of factors potentially driving variation in leaf spectral ChlF across three dominant Boreal evergreen species and different light environments (spatial variation), as well as during the period of spring recovery of photosynthesis (temporal variation). Measurements were conducted on two conifers—Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L.)—and the broadleaf shrub, lingonberry (Vaccinium vitis-idaea L.). The focus on evergreen species, combining conifers and broadleaf species, facilitated a deeper understanding of the relationships between foliar traits and ChlF over time, particularly regarding the influence of leaf morphology and light gradient within the canopy. Data collection occurred biweekly from February to July 2017, encompassing 10 measurement points. Alongside leaf spectral ChlF, leaf samples were analyzed to retrieve a wide range of traits:Photosynthetic traits (e.g., Fv/Fm, maximum quantum yield photochemistry, and NPQS, sustained non-photochemical quenching); Morphological traits (e.g., Specific Leaf Area, SLA); andFoliar pigment traits (e.g. Cab, total chlorophyll a + b, and Zea/Cab, zeaxanthin to chlorophyll a + b ratio). Moreover, Digital Hemispherical Photography (DHP) was used to assess the light environment and its spatio-temporal dynamics. Our results revealed that the spatial variation in spectral ChlF was influenced by different factors throughout the spring recovery period of photosynthesis. Notably, leaf morphology (represented by SLA) and the local light environment (GLI) stood out as continuous and strong contributors, showing a consistent and significant correlation with ChlF variation across the entire study period. This baseline, time-independent element in ChlF magnitude indicates that foliar factors, such as SLA and potentially other factors influenced by GLI, should be considered when interpreting ChlF variations. Meanwhile, temporal variation in spectral ChlF was influenced by different factors across leaves within the forest. For exposed needles and lingonberry, ChlF magnitude followed seasonal patterns of NPQS, while shaded needles exhibited a compensatory relationship between NPQS and PQS. In this study, we highlighted the complex nature of factors influencing spectral ChlF across space and time, suggesting that no single factor should be considered in isolation. Consequently, more long-term, comprehensive studies are needed to provide comparable ChlF data across species, light environments, and biomes. Although focused on boreal forests, our findings can encourage similar research in other biomes. By integrating ground-based physiological observations with ecosystem modeling, our study offers a framework for understanding species-level responses and their implications for forest function and resilience. The inclusion of spectral ChlF in monitoring networks like eLTER or ICP Forests would enhance our ability to track ecosystem responses to global change. Moreover, incorporating species-specific physiological diversity into predictive models of forest carbon cycling will improve accuracy in forecasting forest carbon sequestration and resilience under climate extremes, informing forest management and conservation strategies
Can seasonal waterlogging alter carbon stability in boreal mineral soils?
No full textSoil minerals play an essential role in organic matter (OM) stabilization by reducing its bioavailability thereby slowing its turnover time, and contributing to long-term carbon (C) storage (Lavallee et al. 2019). In humid soils, iron (Fe) and aluminum (Al) oxides are particularly significant contributors to C stabilization (Rasmussen et al. 2018, Salonen et al. 2024). However, Fe oxides are sensitive to changes in soil oxidation-reduction (redox) state. Accordingly, temporary waterlogging leading to anaerobic conditions may result in reductive Fe dissolution, potentially compromising the ability of soils to stabilize OM (Huang et al. 2021). Increased OM availability could thus lead to increased soil CO₂ fluxes, although soil water saturation is traditionally thought to suppress C mineralization (Huang et al. 2021, Moyano et al. 2013. So far, it remains unknown whether the dissolution of Fe-bound OM during temporary anaerobic conditions significantly impacts the C cycle in boreal mineral soils, which are increasingly susceptible to off-season waterlogging due to climate change.We studied the impact of off-season waterlogging on coupled Fe and C dynamics in two distinct arable mineral soils in a 1.5-year long soil monolith experiment. The experiment consisted of three alternating growing and off-seasons, and it was conducted under controlled greenhouse conditions. In total 32 soil monoliths (d 15.2 cm, h 63 cm) were collected from two fields with silty clay and sandy loam texture in southern Finland. During the growing seasons, barley (Hordeum vulgare) was grown in all monoliths while Tall Fescue (Festuca arundinacea) was under sown into half of the monoliths as an overwintering cover crop. After barley harvest, half of the monoliths underwent an excessive irrigation treatment, inducing water saturation for approximately 50 days, while the remaining monoliths served as controls, maintaining soil moisture at 50% water filled pore space. Soil moisture, temperature and redox potential were measured continuously at three soil depths (10, 30 & 50 cm). During the off-seasons, porewater samples were collected from the saturation treatment at the same depths for analysis of dissolved C, nitrogen (N) and Fe. CO2 and CH4 fluxes were measured with a dark manual chamber. After the experiment, the monoliths were destructively sampled for determination of Fe-associated OC (Fe-OC), mineral associated OC and the total C and N contents in the entire soil profile (along with other analyses not detailed here).Waterlogging induced reducing conditions in both soils within one to two weeks which was accompanied by reductive Fe dissolution, especially in silty clay soil. However, the porewater Fe concentrations remained low (max 10 µmol l-1) (Kronberg et al. 2024) and accordingly, repeated waterlogging resulted only a slight and statistically insignificant reduction in soil Fe-OC content in silty clay and no changes in sandy loam soil. No clear differences between the water treatments were found in the total mineral associated OC content in neither soil. Waterlogging altered CO₂ flux dynamics but had no effect on cumulative emissions. No significant CH4 production was observed (Kronberg et al. in revision). In conclusion, our preliminary results suggest that off-season waterlogging at soil temperature +4–12 °C may have minimal impact on the ability of soil minerals to stabilize C in cultivated boreal mineral soils. However, increasing the length or the frequency of waterlogging events could alter this outcome. Additionally, the long-term effects remain to be studied as the combined changes in soil C inputs, soil structure and chemistry of soil constituents could potentially alter soil C sequestration
Evaluating spatially explicit carbon-neutrality for boreal landscapes and regions
No full textThe challenges posed by climate change, biodiversity loss and harmful land-use are deeply interconnected. Successful co-managing of these drivers requires innovative methods that can prioritize and target management actions against multiple criteria, while also enabling evaluation of greenhouse gas (GHG) emissions from different sources and integrated land use planning. The EU aims at reaching carbon neutrality by 2050 and Finland by 2035. We have conducted spatially explicit integrated modelling and evaluation in boreal landscapes and regions in Finland, considering national climate and biodiversity targets and sustainable forestry strategies. Results of three spatially distributed model systems (FRES, PREBAS, Zonation) were integrated to evaluate the potential to reach these goals at both national and regional scale in Finland, by simultaneously considering protection targets of the EU biodiversity strategy. We used different spatial databases and scenarios until 2050 based on mitigation measures of the national climate and energy strategy, forestry policies and predicted climate change. We then evaluated how implementation of these scenarios would affect GHG fluxes, carbon storages, and the possibility to reach the carbon neutrality target (Fig. 1 , Forsius et al. 2023, Holmberg et al. 2023, Junttila et al. 2023). Forested areas important for biodiversity protection were identified based on spatial prioritization. The policy-relevant aim has been to provide detailed spatial, scenario-based information at different scales for key end-users (e.g., communities, provinces, forestry districts, ministries, Alam et al. (2023)). This information can be used for e.g., regional land-use and energy strategy planning/management, and sustainability assessment. We have used data from eLTER/ICOS sites for model developments and evaluation (Forsius et al. 2021). Key general conclusions from our studies are:The potential to reach carbon neutrality in the different administrative regions in Finland varies widely.Reaching both the national and most regional carbon neutrality targets by 2035 assuming current forest harvesting levels is challenging.Integrated evaluation of biodiversity and climate targets enables development of cost-efficient measures.Carbon sequestration of forests is enhanced with climate change, but uncertainties caused by disturbances increase also.Key aims for future work are to develop process descriptions in our model systems, conduct uncertainty modelling and assessment, and continue co-operation with regional actors to evaluate regional targets