This study investigates the soil organic carbon (SOC) and whole tree biomass carbon (C), soil bulk density (BD) as well as changes in these parameters in afforested areas in Latvia. The study covered 24 research sites in afforested areas—juvenile forest stands dominated by Scots pine, Norway spruce and Silver birch. The initial measurements were conducted in 2012 and repeated in 2021. The results show that afforestation mostly leads to a general decrease in soil BD and SOC stock in 0–40 cm soil layer and an increase in C stock in tree biomass across afforested areas with various tree species, soil types, and former land uses. The physical and chemical properties of the soil could explain the differences in changes in soil BD and SOC caused by afforestation, as well as the impact of past land use may have persisted. When comparing the changes in SOC stock with the increase in C stock in tree biomass due to afforestation, taking into account the decrease in soil BD and the resulting elevation of soil surface level, the afforested areas at juvenile development stage can be considered a net C sink.

The aim of this study was to evaluate the impact of groundwater level, soil temperature and general soil chemistry on greenhouse gas (GHG)—carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O)—fluxes from tree stems in deciduous stands with nutrient-rich naturally wet and drained peat soils. In total, nine sample plots were established in the central and north-eastern part of Latvia. The studied tree species were silver birch (Betula pendula Roth.) and black alder (Alnus glutinosa (L.) Gaertb.). Tree stands of different ages and tree dimensions were selected for the study. GHG fluxes were measured with a circular-type non-transparent chamber of fixed area and volume, which was connected to the “Gasmet DX4040” mobile spectrometer. Ambient and soil temperature at a depth of 10 cm were measured, soil parameters (pH and content of carbon (C), nitrogen (N), potassium (K), phosphorus (P)) down to 30 cm depth were analyzed, and groundwater levels and weather conditions (wind, cloudiness, precipitation) were determined. The study found that CO₂ fluxes from tree stems show a distinct seasonal pattern and a strong positive correlation with soil temperature. Significant differences in CO₂ fluxes were found between temperature ranges below and above 5 °C, indicating that this temperature represents a threshold value. CH₄ emissions from the tree stems increased with increasing groundwater levels. The impact of groundwater level becomes insignificant if the depth of the groundwater exceeds 30 cm. No significant N₂O fluxes from tree stems were detected for most of the study period, except for March, April and June in black alder stands. As with CH₄, N₂O emissions exhibit an increase as groundwater levels rise. The C and N contents in soil have a significant impact on N₂O fluxes from tree stems. There is a tendency for the N₂O flux to increase along with increasing C and N contents in soil.

Within this study, we evaluated the fine root (trees and understory vegetation combined) morphological traits, fine root production (FRP), and carbon (C) input with fine root litter in forest stands (dominated by either coniferous or deciduous trees) and clearcut areas (previously dominated by coniferous trees) with nutrient-rich organic soils. The study was conducted in 26 sites in hemiboreal forest land in Latvia and summarizes the results obtained in a two-year study (2020–2022) using the root ingrowth method. Traits and production of fine roots varied significantly depending on forest development stage (stand or clearcut area), dominant tree species type (coniferous or deciduous), and soil drainage status (drained or naturally wet). According to the results of the second study year, mean FRP among groups of study sites varied from 0.58 ± 0.13 to 1.38 ± 0.28 t ha⁻¹ yr⁻¹, while C input with fine root litter ranged from 0.28 ± 0.06 to 0.68 ± 0.14 t C ha⁻¹ yr⁻¹. More than half (59 ± 4%) of the total FRP occurred in the upper 0–20 cm soil layer. FRP tended to correlate positively with soil C/N ratio and negatively with soil pH and soil nutrient concentration. Incubating ingrowth cores for at least two years is strongly recommended to accurately estimate annual FRP and C input. This helps to avoid potential underestimation that may occur when using results of only one incubation year (12 months after ingrowth core installation). This study provided new insights into the dynamics and traits of fine roots and will help to improve the accuracy of C flow estimation in hemiboreal forests with nutrient-rich organic soils in Latvia.

Latvia's forest reference level (FRL) should take in account the future impact of dynamic age-related forest characteristics in order to avoid unduly constraining the forest management intensity as a core element of sustainable forest management practice, with the aim of maintaining or strengthening long-term carbon sinks. The basic for calculations of GHG projections is AGM (Forest growth model) and EPIM (Emissions Projections and Inventory Model). The scope of the study is to verify applicability of the AGM model in elaboration of the forestry projections for elaboration of the FRL according to regulation (EU) 2018/841.

This study aimed to assess soil organic carbon (SOC) concentration and stock in mineral soils in cropland and grassland in Latvia, considering soil groups and texture classes. It covered 197 sites across Latvia (152 in cropland, 45 in grassland). Soil profile description and sampling (at depths of 0–10 cm, 10–20 cm, and 20–40 cm) were conducted between 2021 and 2023. Laboratory analyses included soil bulk density (SBD), total carbon (TC), total nitrogen (TN), carbonate content, pH, and extractable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg). SOC stock was calculated, and correlations with other soil parameters were determined. In cropland sites, Arenosols and Stagnosols had the lowest SOC concentration and stock, while Gleysols and Phaeozems had the highest. In grassland sites, Retisols exhibited the lowest SOC concentration in the 0–20 cm layer, while Planosols had the highest SOC concentration in this layer. Conversely, in the 20–40 cm layer, Retisols showed the highest SOC concentration, while Gleysols had the lowest concentration. Regarding SOC stock in grassland sites, Planosols exhibited the highest values, while the lowest values were observed for Retisols and Umbrisols. Contrary to our hypothesis that grassland exhibits higher SOC stock than cropland, our results show the reverse for Phaeozems, the dominant WRB soil group in this study: a higher average SOC concentration and stock in cropland compared to grassland. However, very low occurrence of some soil groups and lack of some soil groups for grassland sites hinders the correct interpretation of these results, and further investigations are required in future studies.

Peat erosion has a significant impact on soil fertility, agricultural productivity, and climate change dynamics. Through this process, the topsoil rich in organic matter and carbon (C) is removed and can travel long distances, causing a net C loss. Additionally, peat undergoes oxidation, resulting in further C loss. In our study, we evaluated C losses from 11 peat extraction fields in two study sites, abandoned for more than 15 years and overgrown by vegetation of different densities. We used high-resolution airborne laser scanning point clouds and multispectral aerial images acquired periodically within a 9-year period, as well as chemical analyses of the topsoil layer. In our study, we found a strong correlation between peat subsidence, C loss, and the vegetation density (NDVI value). NDVI also determines most of the uncertainty in elevation data. We found also that both erosion and peat subsidence are significant sources of C losses from peat extraction sites. At a site monitored for over 9 years, our estimated ground elevation changes ranged from 0.1 cm y⁻¹ to 0.58 cm y⁻¹; however, at a different site monitored over a 4-year period, the values ranged from 2.14 cm y⁻¹ to 5.72 cm y⁻¹. Accordingly, the mean annual C losses varied from 0.06 to 0.22 kg C m⁻² y⁻¹ and from 1.21 to 3.57 kg C m⁻² y⁻¹.