Alluvial soils have high importance for both agriculture and biodiversity; however, these soils can also contribute to greenhouse gas (GHG) emissions including carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4). In this study, we examined GHG fluxes of three grassland and two cropland sites with alluvial soils in Abava river floodplain, Latvia (Europe). Soil CO2 fluxes representing heterotrophic respiration (Rhet) were determined using a portable CO2 gas analyser, while ecosystem respiration (Reco), soil CH4 and N2O fluxes were quantified using a manual closed chamber method combined with gas chromatography. Most alluvial soils acted as source of GHG emissions with the exception of two grassland site where annual CH4 exchange reflected a slight CH4 removal from the atmosphere. Mean total GHG emissions (sum of net CO2, CH4 and N2O) were 7.0 +/- 3.3 t CO2 eq./ha/year in grassland sites and 14.5 +/- 4.8 t CO2 eq./ha/year in cropland sites. Net CO2 contributed the most to total annual GHG emissions with mean values of 6.2 +/- 3.3 t CO2/ha/year in grassland and 13.6 +/- 4.8 t CO2/ha/year in cropland sites. Although the number of study sites is limited, the results support that, in the context of climate change mitigation, grassland represents a more climate-friendly type of floodplain land use than cropland in the hemiboreal region.

Dissolved organic carbon (DOC) export from drained organic forest soils represents a substantial but still insufficiently operationalised pathway of carbon loss in greenhouse gas (GHG) accounting frameworks. Although DOC-derived downstream CO2 emissions are acknowledged in international guidelines, their routine inclusion in national inventories is constrained by data intensity and model complexity. This study presents a pragmatic, inventory-oriented modelling workflow designed to quantify DOC export and associated nutrient losses from drained organic soils using widely available meteorological, hydrological and spatial datasets. The approach combines Penman-Monteith based estimation of reference evapotranspiration with a simplified water-balance framework to derive monthly and annual run-off at the catchment or a field scale. DOC and nutrient exports can be calculated by coupling modelled run-off with measured monthly concentrations, allowing rapid updating as new water-quality data become available. The workflow was parametrised and tested using multi-year field datasets from hemiboreal drained peatland sites in Latvia, including forest stands, agricultural land and abandoned peat extraction areas monitored within the scope of LIFE OrgBalt and other projects. Results demonstrate pronounced differences in DOC export among land-use types, driven jointly by evapotranspiration control on run-off and land-use-specific DOC concentration. Annual DOC exports in drained organic forest soils were generally below the default emission factor from the 2013 IPCC Wetlands Supplement (0.31 t C·ha-1·yr-1), with the nationally derived factor for forest land (0.22 t C·ha-1·yr-1) approximately 30% lower. The method additionally yields nutrient export estimates relevant to water quality assessment: mean annual total nitrogen export across study sites was 15.52 ± 9.47 kg·ha-1·yr-1, indicating substantial losses from drained organic soils under forest land use. By deliberately avoiding data-intensive process-based carbon models, the proposed workflow fills the gap between detailed site studies and operational GHG accounting. It provides an implementable basis for integration DOC-related C losses and nutrient export into national inventories and drainage maintenance planning, thereby supporting both climate-mitigation reporting and evidence-based land and water management in drained organic soils.

This case study quantifies greenhouse gas (GHG) flux responses of nutrient-rich peatland forest soils to regenerative felling followed by excavator-based site preparation that created deep furrows (local drainage lines) intended to modify the post-harvest water regime. The study was implemented in three over-wet peatland forest sites (non-drained), where gas-exchange measurements were continued before and after felling and furrow installation using an established experimental layout with sampling points distributed at different distances from the furrow. Fluxes of soil carbon dioxide (CO2) representing both heterotrophic and total respiration, methane (CH₄), and nitrous oxide (N2O) were measured alongside controlling environmental variables (air/soil temperature and groundwater level), enabling attribution of observed changes to hydroclimatic and disturbance drivers. In plots where deep furrows were installed, mean soil GHG emissions increased by a factor of 1.7, from 242 ± 40 to 401 ± 110 mg CO2-eq m-2·h-1; the magnitude of increase scaled with the achieved drawdown of groundwater level, ranging from modest lowering (15 to 23 cm) associated with a smaller increase (220 ± 17 to 339 ± 33 mg CO2-eq m-2·h-1) to strong drawdown (≈10 ± 15 to 42 ± 26 cm) associated with an increase of 240 mg CO2-eq m-2·h-1, corresponding to emissions that were 1.8 times higher than before treatment. Despite CO2 dominating the overall balance, CH₄ decreased markedly after furrow installation, with an average reduction of approximately eleven-fold, whereas N2O increased by approximately 88%, yielding a net post-harvest increase in the integrated balance (1.42 to 1.74 t CO2-eq ha-1). The temporal pattern suggested that short-term emission elevations may be driven substantially by fresh harvest residues and rapidly responding ground vegetation, rather than groundwater change alone, highlighting the need for longer monitoring to separate transient disturbance pulses from persistent drainage effects. These results provide empirical constraints for improving national-scale emission factor development and for evaluating trade-offs between mitigating CH₄ via aeration and stimulating CO2/N2O following regenerative harvesting on peat soils.

Abstract. Greenhouse gas (GHG) emissions from organic soils are a key component of land-use-related emissions, particularly in countries with large areas of organic soils. Temperate-zone forest soils remain less studied in GHG research than boreal soils. However, recent work has expanded coverage in the northeastern temperate region, which, under the Köppen–Geiger climate classification, shares key climatic characteristics with the southern boreal region (Dfb). This study synthesised updated GHG flux data to evaluate carbon balance and emissions from forest organic soils in the Dfb zone, stratified by drainage status, nutrient availability, and dominant tree species. Such stratification revealed CO2 source-sink patterns, which encourage the ecological relevance of using these categories for data aggregation. The dominant tree species reflected nutrient status: drained coniferous and deciduous stands have been reported as CO2 sources, emitting 0.03 ± 0.55 and 0.47 ± 0.29 t CO2‑C ha−1 year−1, respectively, though soils tended to shift toward CO2 sinks in stands older than 25 years. In contrast, undrained soils have generally been observed to function as CO2 sinks, although not necessarily in all sites. However, this stratification was less informative for CH4 and N2O. CH4 fluxes were primarily determined by water table level rather than by other site variables, whereas N2O showed a tendency toward elevated emissions in deciduous stands, irrespective of drainage status.

This review evaluates the current state of knowledge on the use of wood fibres and related woody materials as partial substitutes for peat in substrates used for forest nursery production, with particular emphasis on container seedlings. The review was prepared as a structured narrative synthesis of the available literature, focusing on substrate composition, physical and chemical properties, tree seedling growth, root development, water regime, fertilisation, operational handling, economic aspects and remaining research needs. The available evidence shows that wood fibres are technically promising components of peat-reduced growing media, but their performance depends strongly on the raw-material origin, processing method, substrate proportion, tree species, and cultivation management. The most reliable results have been obtained with partial substitution systems, whereas peat-free solutions remain species-specific and require careful optimisation of irrigation, nitrogen supply, pH control, and substrate quality. Although wood-based materials may improve resource efficiency and, under favourable local conditions, reduce substrate costs, wider implementation is constrained by variable material quality, limited standardisation and insufficient operational-scale validation. The main remaining research need is to define species-specific application thresholds and management protocols and to link nursery performance with outplanting success and full production economics under commercial conditions.

Tree stumps are a potentially significant source of renewable energy, but their extraction may result in significant adverse impacts on ecosystems. To assess mid-term effects (up to 8 years after harvesting) of stump removal on nutrient status and young stand development in mesotrophic Latvian hemiboreal forests, we evaluated soil and soil solution chemistry, subsequent young stand growth, and foliar micro- and macroelement status in five sites where above-ground whole-tree harvesting (WTH) was compared to above-ground WTH with additional stump biomass removal (WTH + SB). Post-harvest soil organic carbon stocks and C/N ratio declined more after the WTH + SB than after WTH while soil nitrogen stocks increased. No additional acidification of the soil solution caused by stump removal was observed, and the inconsistent pattern of nutrient concentration change in soil solution (partial increase of phosphates, calcium and magnesium in WTH + SB relative to WTH, no clear response of nitrates) reflected site-specific conditions. N concentration in planted Norway spruce needles did not differ consistently between the treatments, and foliar nutrient concentrations of the regenerated stands were mostly within the typical range of similar forest site types in Latvia. Mean tree height was significantly greater after WTH compared to WTH + SB in sites with monodominant regeneration.

While forests are generally regarded as beneficial for water quality, forest management can significantly impact water quality, even if sustainable forest management practices are applied. Fellings alter water balance and nutrient cycling, while forest roads with impermeable surfaces fragment ecosystems and enhance runoff. Road construction often requires extensive landscape modification and material relocation, which increases substance leaching and erosion. In the present study, water quality parameters and nutrient export were monitored over eight years (2016-2023) in a forested catchment (2212 ha) and its sub-catchments. During this period, 15.8 km of forest roads were constructed, and fellings occurred across 18.8% of the catchment. Fellings increased nitrogen compound concentrations and export, with effects persisting for four-five years. Runoff patterns strongly controlled the export of total nitrogen, calcium, and dissolved organic carbon. The onset of fellings and higher felling intensities raised total suspended solids levels, though high variability masked statistical significance. Calcium and potassium concentrations also increased during periods of more intense felling, though their export patterns closely followed runoff dynamics. Road construction increased calcium and total suspended solids concentrations.

Soil disturbance by forwarding machinery can create ruts that alter soil structure, aeration and microtopographic water redistribution, thereby shifting post-harvest greenhouse gas (GHG) fluxes. This study assessed the short-term GHG effect of forwarding ruts in forest clearcuts on organic and moist mineral soils and developed a remote-sensing workflow to characterise rut extent for upscaling. Chamber-based measurements of CO2, CH₄ and N2O were carried out in 2022-2024 in six trial objects (four on organic soils and two on mineral soils), with paired sampling in ruts and adjacent undisturbed control microsites located ca. 4-5 m from ruts; organic-soil sites were harvested in winter 2022 and the monitoring design ensured multi-season post-harvest time series (including pre-harvest data availability for part of the organic-soil sites). Across organic-soil clearcuts, the combined CO2 + CH4 + N2O flux expressed as CO2 equivalents was higher in ruts (537.1 ± 130.1 mg CO2-eq·m-2·h-1) than in controls (402.2 ± 33.1 mg CO2-eq·m-2·h-1), i.e. a 33.5% increase, with the response attributed to rut-induced wetter and more anaerobic conditions that enhance CH₄ production while constraining aerobic CO2 formation. In moist mineral soils, the rut–control increase in total GHG flux was smaller (16.7%), indicating pronounced soil-type dependence. For operational monitoring, a LiDAR–DEM approach with automated rut detection and classification (including cross-profile based depth/width characterisation) was applied at regional scale; in 38 clearcut stands on peatland forest types, ruts were observed in 24 stands ( ≥ 30 m of ruts deeper than 20 cm), and automated mapping underestimated rut length by ~37% relative to manual interpretation, highlighting the need for calibration and auxiliary constraints (e.g., machine GPS tracks) when scaling rut-related GHG impacts.

Peatland forests play a significant, yet highly variable, role in atmospheric methane (CH4) and nitrous oxide (N2O) emissions. Drainage reduces CH4 but increases N2O fluxes from nutrient-rich soils, creating complex climate trade-offs. To refine regional climate strategies, a clearer understanding of soil fluxes and influencing factors across forest types in the hemiboreal zone is needed. This study presents two years of soil flux and environmental data collected from 2020 to 2023 using manual chambers at 18 drained (DF) and 7 undrained (UF) sites, with different tree species, in Estonia, Latvia, and Lithuania. Soil water‑table depth was the primary control on annual CH4 exchange; DF sites acted as CH4 sinks (–4.6 kg ha–1 y–1), whereas UF sites were net sources (38.2 kg ha–1 y–1). In contrast, N2O emissions occurred at all sites, averaging 5.9 kg ha–1 y–1 in DF and 1.4 kg ha–1 y–1 in UF soils. Within DF sites, Myrtillus‑type pine stands exhibited the lowest N2O fluxes, while alder stands showed the highest, followed by birch- and spruce-dominated stands, reflecting differences in hydrology, pH, and C/N ratios of the soil. Our findings reveal significantly lower CH4 and moderately higher N2O emissions from DF soils than the IPCC Tier 1 temperate zone emission factor (EF), which has thus far been used for the hemiboreal zone. This study can improve national GHG inventories using specific information. We recommend applying Baltic region-specific EFs, as the mean annual CH4 and N2O emissions showed no significant difference across the three countries.

Abstract. Degraded peatlands are among the largest land-based sources of greenhouse gas emissions in the European Union (EU). In response, the EU’s climate change mitigation targets are driving efforts to reduce emissions and enhance carbon sequestration within the land-use sector. A significant challenge is the high emissions from organic soils, particularly those degraded by peat extraction and agriculture. This has sparked discussions on appropriate mitigation strategies. Rewetting is gaining attention, and concerns persist that afforestation may hinder rewetting efforts, thereby reducing climate change mitigation potential. However, such concerns often oversimplify both measures. Though many perceive afforestation and rewetting as competing strategies, these measures should ideally and alternately be implemented based on distinct local conditions and goals in different regions. This perspective evaluates their advantages and limitations using evidence from boreal and temperate peatlands. The paper highlights underappreciated, evidence-based arguments to support more nuanced stakeholder discussions and promote complementary, context-appropriate implementation of the measures.

Greenhouse gas (GHG) flux responses to regenerative felling are strongly mediated by peatland hydrology, yet empirical contrasts between non-drained peatland forests and drained peatland forests remain underrepresented in operational forestry decision-making. This case study quantifies soil carbon dioxide (CO2), methane (CH₄) and nitrous oxide (N2O) fluxes in naturally wet peatland forests and drained peatland forests in Latvia, comparing mature stands with adjacent clear-felled areas (regenerative felling). Flux measurements were collected during 2021-2024, with regenerative felling implemented in 2022 at the studied sites. Mean soil GHG fluxes (as CO2 equivalents, abbreviated as CO2e) increased after felling in both site types, but the magnitude and gas structure differed markedly. In drained peatland forests, CO2e increased by 32% from 232 to 307 mg CO2eq·m-2·h-1 (20.3 to 26.9 t CO2eq·ha-1·yr-1), whereas in non-drained peatland forests it increased by 120% from 234 to 514 mg CO2eq·m-2·h-1 (20.5 to 45.0 t CO2eq·ha-1·yr-1). The stronger response in non-drained peatland forests was primarily driven by CH₄, rising from 0.95 to 5.22 mg CH₄·m-2·h-1, consistent with post-harvest water-table rise and enhanced anaerobic microsites reported in other temperate/boreal clear-fell studies. In contrast, the drained peatland forest response was comparatively moderate and more closely associated with CO2-dominated decomposition dynamics typical of drained organic soils. These results indicate that regenerative felling can generate substantially higher short-term climate forcing on naturally wet peat soils than on drained peat soils, implying that harvest planning on peatlands should explicitly account for site hydrology and the CH₄-sensitive post-harvest period.

Abstract. The growing reliance on nature-based solutions for climate change mitigation has increased the need for robust methods to assess soil greenhouse gas (GHG: CO2, CH4, N2O) emissions. A key challenge is the upscaling of site-specific observations to improve predictions of the spatial distribution and magnitude of soil GHG fluxes. Upscaling is hindered by the laborious, costly, and time-consuming nature of soil flux measurements at the scale needed to generate sufficiently large datasets. Fourier-transform infrared (FTIR) spectroscopy is a cost-effective, high-throughput method that has demonstrated its ability to predict soil physicochemical properties. Since the magnitude of soil GHG fluxes is strongly influenced by these properties, FTIR may also serve as a basis for predicting soil GHG fluxes. In this study, we evaluated whether FTIR calibration models can be developed to predict soil GHG fluxes and organic matter decomposition rates directly from mid-infrared spectra. FTIR calibration and cross-validation were performed using soil samples collected across 20 wetland study sites in six European countries and linked to measured soil GHG fluxes and decomposition rates at the corresponding sampling sites. The results demonstrated that FTIR can be calibrated to reliably predict soil decomposition rates and heterotrophic respiration standardised at a given soil temperature. For decomposition rates, the root mean square error (RMSE) of FTIR-predicted values was 0.01 dd⁻1, corresponding to approximately 17–53 % of the interquartile range of observed rates. For heterotrophic respiration, the RMSE of 18 mg CO2–C m⁻2 h⁻1 corresponded to 21–64 % of the interquartile flux range. The findings also indicate FTIR's potential to identify biogeochemical risk areas or potential hotspots of CH4 and N2O emissions, effectively mapping the substrate-driven 'ultimate' controls even when 'proximate' environmental triggers (e.g., water table fluctuations) are absent.

Organic peat soils, common in boreal, temperate, and tropical wet climate zones, represent one of the largest natural terrestrial carbon reservoirs. Europe has approximately 33 million hectares of organic soils, with 4.2% managed and 3.7% unmanaged. Grasslands, constituting 17.8% of managed organic soils (1.1% in Baltic countries), are often subjected to drainage, a common practice transforming these carbon-rich environments into significant greenhouse gas (GHG) sources. The drainage process alters nutrient cycling, impacting microbial activities that control nitrous oxide (N2O), methane (CH4), and other GHG production and consumption. Our research aims to quantify CH4 and N2O emissions from grasslands on organic soils in the hemiboreal zone and evaluate to which extent they are regulated by drainage depth. Furthermore, this research contributes to the broader goal of sustainable agriculture and effective climate change mitigation strategies by updating and addressing the pressing need for updated region-specific emission factors (EF). The default IPCC (2014) Tier 1 EFs for grasslands on drained organic soils in the temperate zone are based on values from only seven sites presented in two publications. So far, there is no information from the hemiboreal zone in which the Baltic countries are located. To address these objectives, we conducted continuous field measurements in different periods in the years 2016–2023 in 14 sites in the Baltic Countries (Estonia, Latvia, Lithuania). The full-year study periods cover the winter and growing seasons to capture seasonal dynamics. We divided the grasslands into groups: deep drained and shallow drained grasslands, and, as a reference, two undrained grasslands. We have taken the IPCC distribution as a basis, where deep drained sites have a mean groundwater level (GWL) of more than -30 cm and shallow drained sites with a mean GWL of less than -30 cm. Soil N2O and CH4 fluxes from the soil were measured using the manual dark static chamber technique, with the number of measurement subplots ranging from 5 to 9. The frequency of measurements varied, being conducted biweekly (Estonia) and monthly (Latvia, Lithuania). During each gas sampling session, soil water content (SWC) and soil temperature (Tsoil) were measured manually at each monitoring point close to the GHG measurement subplots. Additionally, GWL parameters such as pH, electrical conductivity, and oxygen concentration were manually measured during each sampling session. Water samples for chemical analysis were taken once a month from the sampling wells to analyze. At the conference, updated EFs for Baltic countries, the soil N2O and CH4 flux dynamics, and their relation to the GWL will be presented.

Peatland ecosystem degradation and changes made in hydrology by artificial drainage may affect the biogeochemistry of peatlands and, together with projected global warming, may lead to significant changes in greenhouse gas (GHG) fluxes. Drainage of peatlands increases organic matter's aerobic decomposition, changes native vegetation, and may decrease the storage of C. The vegetative characteristics of forest ecosystem types may change a net GHG sink peatland to a source in drained organic soils.However, soil CH4 and N2O fluxes in peatlands are spatially and temporally (interannual, seasonal) variable, and detailed data from drained nutrient-rich organic soils in the hemiboreal zone is lacking. We conducted a study spanned over two years comprising drained (n=18) and undrained (n=7) peatland forests with dominant tree species of Scots pine (Pinus sylvestris), Norway spruce (Picea abies), birch (Betula sp.), and black alder (Alnus glutinosa) spread across Estonia, Latvia, and Lithuania. Instantaneous fluxes of CH4 and N2O were measured monthly for the whole year using the manual static chamber method. Environmental parameters in soil, such as soil water level (WTL), moisture, and temperatures at depths (0-40 cm), were monitored continuously, and detailed soil chemical analyses were conducted. To constrain the factors regulating temporal fluxes of various environmental conditions and differentiate annual emissions between land use in the Baltic region.The results show that all drained forest soils were annual CH4 sinks (−37.0 ± 4.5 μg C m−‍2 h−‍1), while undrained forests were emitters on average 388.5 ± 142. Mean annual CH4 uptake is significantly higher in deep-drained soils −45.5 ± 3.6 μg C m−‍2 h−‍1 (WTL > −50cm) than in poorly drained soils (p

Abstract. Drainage of organic soils is associated with increasing soil carbon (C) efflux, which is typically linked to losses in soil C stock. In previous studies, drained organic forest soils have been reported as both C sinks and sources depending on, e.g., soil nutrient and moisture regime. However, most of the earlier research was done in boreal region, and both the magnitude of C efflux and the impact of soil moisture regime on soil C stock are likely to vary across different climatic conditions and ecosystems, depending further on vegetation. A two-year study was conducted in hemiboreal forest stands with nutrient-rich organic soil (including current and former peatlands) and a range of dominant tree species (black alder, birch, Norway spruce, Scots pine) in the Baltic states (Estonia, Latvia, Lithuania). In this study, we analysed the C balance of organic soil in drained (19) and undrained (7) sites. To assess the C balance, soil respiration was measured along with evaluation of C influx into the soil through aboveground and belowground litter. To characterize the sites and factors influencing the C fluxes, we analysed soil temperature, water table level, physical and chemical parameters of soil and soil water. On average, no changes in soil C stocks (0.45±0.50 t C ha⁻¹ year⁻¹) were observed in drained sites dominated by black alder, birch, or Norway spruce, while drained Scots pine sites showed soil C removals with a mean rate of 2.77±0.36 t C ha⁻¹ year⁻¹. In undrained birch- and spruce-dominated sites, soil functioned as mean C sink at 1.33±0.72 t C ha⁻¹ year⁻¹, while the undrained black alder stands showed an uncertain C balance of 1.12±2.47 t C ha⁻¹ year⁻¹. The variability in C balances were influenced by the nutrient-rich soil exhibiting a wide range of nutrient conditions and organic matter quality. Thus, indicating that soil macronutrient concentrations and pH can determine whether the soil functions as a C source or sink.

Peatlands play an important role in global climate regulation and carbon (C) cycling. To evaluate the potential effect of peatland restoration on greenhouse gas (GHG) emission mitigation, and preservation of peat C stock or enhancement of atmospheric carbon dioxide (CO2) sequestration, we used a manual chamber method to measure soil heterotrophic respiration CO2 emissions (Rhet) and ecosystem GHG emissions. Ecosystem emission measurements included methane (CH4), nitrous oxide (N2O) emissions and forest floor CO2 emissions (Rfloor) in forested peatlands or ecosystem CO2 emissions (Reco) in peatlands without tree cover. Measurements of Reco and Rfloor were conducted using chambers that included all vegetation present in the ecosystem or ground vegetation, respectively. Rhet measurements were performed after the removal of ground vegetation and litter layer and trenching of the roots. In addition to GHG emission measurements, C input into the soil with vegetation litter was estimated, and environmental variables (including soil temperature and moisture, groundwater level, water chemistry and others) that potentially can affect the magnitude of GHG emissions were monitored. The monitoring was initiated in 2023 and continued in 2024 at seven study sites located in raised bogs within the hemiboreal vegetation zone of Europe, specifically in Latvia. Study sites included different habitats of pristine peatlands, restored peatlands through rewetting, and areas in both strong and weak drainage impact zones where the development of woody vegetation characteristic of the forest ecosystem has occurred. Preliminary results of GHG emission measurements show that the annualized monthly mean ecosystem gross GHG emissions, expressed in CO2 equivalents (excluding C sequestration by vegetation), ranged from 9.7 to 45.9 t CO2 eq. ha−1 year−1 in degraded (drained) peatlands, while in restored (including rewetted) peatland GHG emissions ranged from 11.0 to 25.3 t CO2 eq. ha−1 year−1.Acknowledgements: The research was conducted within the scope of the European Commission LIFE Climate Action Programme Project “Peatland restoration for greenhouse gas emission reduction and carbon sequestration in the Baltic Sea region” (LIFE21 - CCM - LV - LIFE PeatCarbon, Project number: 101074396).

Drainage of organic soils is associated with increasing soil carbon dioxide (CO2) efflux, which is typically linked to losses in soil carbon (C) stock. In previous studies, drained organic forest soils have been reported as both CO2 sinks and CO2 sources depending on, e.g., soil nutrient and moisture regime. However, most of the earlier research was done in the boreal zone, and both the magnitude of CO2 efflux and the impact of soil moisture regime on soil C stock are likely to vary across different climatic conditions and ecosystems, depending further on vegetation. A 2-year study was conducted in hemiboreal forest stands with nutrient-rich organic soil (including current and former peatlands) and a range of dominant tree species (black alder, birch, Norway spruce, Scots pine) in the Baltic states (Estonia (EE), Latvia (LV), Lithuania (LT)). In this study, we analyzed the CO2 balance of organic soil in drained (19) and undrained (7) sites. To assess the CO2 balance, soil respiration was measured along with the evaluation of CO2 influx into the soil through aboveground (aGV) and belowground (bGV) litter. To characterize the sites and factors influencing the CO2 fluxes, we analyzed soil temperature, soil water table level (WTL), and physical and chemical parameters of soil and soil water. Irrespective of drainage status, the soils functioned as both CO2 sinks and CO2 sources. On average, a close-to-neutral soil CO2 balance (+0.45 +/- 0.50 tCO2-Cha-1yr-1) was observed in drained sites dominated by black alder, birch, or Norway spruce, while drained Scots pine sites showed soil CO2 removals with a mean rate of +2.77 +/- 0.36 tCO2-Cha-1yr-1. In undrained birch- and spruce-dominated sites, soil functioned as a mean CO2 sink at +1.33 +/- 0.72 tCO2-Cha-1yr-1, while the undrained black alder stands showed an uncertain CO2 balance of +1.12 +/- 2.47 tCO2-Cha-1yr-1. Variation in the soil CO2 balance was related to soil macronutrient concentrations and pH: forest types characterized by lower nutrient availability showed greater soil CO2 sink. The reported soil CO2 balance values may be used as regional emission factors (EFs).

This study investigated the impact of forest fertilization on ground vegetation in deciduous and conifer stands across different forest site types (forests with drained mineral soils, forests with drained organic soils, and dry upland forests), stand age groups (young, middle-aged, and pre-mature), and fertilizer types (ammonium nitrate (NH4NO3) and wood ash alone, and both together). Ground vegetation was surveyed one to three years after fertilizer application, with the projected ground cover of individual species in the moss and herb layers determined. Thus, results reflect short-term impact of fertilization. Species richness and diversity (Shannon diversity index, H′) were compared between fertilized and control (unfertilized) plots. The results show that species diversity in the moss layer of silver birch stands was significantly affected by fertilization, while species richness was significantly influenced by the interaction between fertilization and forest site type. Differences between control and fertilized plots in birch stands suggest a potentially negative response of the moss layer to fertilization. In contrast, no significant effect of fertilization was observed in Norway spruce stands, where site type and stand age emerged as significant factors. In Scots pine stands, where NH4NO3 was applied alone, fertilization had a significant impact on both species richness and diversity in the herb layer. In the moss layer, a marginally significant effect was found for the interaction between fertilization and stand age. NH4NO3 alone appeared to enhance herb layer richness, although its effect on species diversity was more variable. Our study highlights the context-dependent nature of fertilization effects on species richness and diversity in Latvian hemiboreal forest ecosystems.