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Climate change is one of the greatest environmental, social and economic challenges of our days and warming of the climate system is unequivocal. Greenhouse gases (GHG) emissions caused by human activities are the most significant driver of the observed climate changes since the mid- 20th century. Managed nutrient rich organic soils are one of the largest key sources of GHG emissions in Boreal and Temperate cool and Moist (TCM) climate regions in Europe. In these regions managed organic soils usually are drained forests and fens or mires that when efficiently drained can increase GHG emissions. The total area of managed organic soils in EU is 34.5 mill. ha (7% of the EU area). Organic soils can have high GHG emission as well as carbon storage potential depending on chosen management strategies. Based on the research and results obtained within the framework of the LIFE program project “Demonstration of climate change mitigation potential of nutrient rich organic soils in Baltic States and Finland” (LIFE OrgBalt), the authors have developed a functional land management model – a tool for sustainable and climate friendly management of nutrient rich organic soils. The model is designed to allow the user to assess the performance of organic soils depending on the planned land use type (scenario), based on the land use performance criteria: financial return, economic return, financial deficit and the optimal amount of public funding, reduction of GHG emissions and ecosystem services assessment. Based on the findings and using the developed model, it is possible to implement deliberative management decisions of managed nutrient rich organic soils, to evaluate potential management costs, plan the expected financial return, assess the benefits of climate mitigation and take into account nature values. [ABSTRACT FROM AUTHOR]

Latvia is one of the leaders in production and use of forest biofuel in Europe. The rapid increase of forest biofuel market raises questions about sustainability of the supply chains and contribution of the forest biofuel produced in Latvia to the climate change mitigation. Sustainability of forest biofuel is addressed in multiple recent international political initiatives; particularly, the European 2030 climate and energy package and the nature restoration regulation. Climate change mitigation potential of forest biofuel is surrounded by multiple speculations, which have to be addressed by comprehensive evaluation of greenhouse gas (GHG) emissions due to production and delivery of forest biofuel. According to the study results, average GHG emissions due to delivery of harvesting residues from the state forests correspond to 1.4 kg CO2 eq GJ-1, including forwarding, comminution and delivery to a 68 km distance. This is significantly less than the default values provided in the regulation (EC) 2018/2001, particularly during the delivery of forest biofuel. GHG emissions due to delivery of forest biofuel from removal of vegetation in abandoned farmlands are 1.9 kg CO2 eq GJ-1, from forest drainage ditches - 1.7 kg CO2 eq GJ-1, from pre-commercial thinning - 2.1 kg CO2 eq GJ-1. Estimation of the GHG emissions is complicated by limited information on some of the sources and productivity. Building of the system for collection of activity data is a crucial task for transparent demonstration of GHG emissions and the effect of applied mitigation measures. [ABSTRACT FROM AUTHOR]

A prototype of a mower-chipper typeharvester was developed for cutting small stems in cooperation between LSFRI Silava and SIA Laflora. The prototype produces chips and eco-pellets of various lengths in short rotation coppice, shelter belts and overgrown agricultural lands. The innovative element of the harvester is use of gravity force (bending of stems by a tractor own weight and formation of bunch of shoots with header and underframe) to feed in circular saws and chipper, thus significantly reducing energy demand for bending of shoots into the chipper, which is the most energy demanding operation in other commercial willow harvesters. Time studies were implemented in Skrīveri region in August 2022 in short rotation coppice fields established in 2011. Willows of tree different ages (1, 3 and 5 years) were harvested. The main factor influencing productivity in the study sites was growing stock of the coppice crops. The driving speed of the base machine cannot be significantly increased to avoid clogging of the chipper infeed and to retain good quality of chips; therefore, reduction of growing stock cannot be compensated with faster driving in the field. It was also noted that wood chip quality becomes significantly worse if the stump diameter of an average shoot is less than 1 cm and the saw blades are more often blocked by thin, flexible shoots. Similarly, clogging related issues were found in the 5 year old plantation. Optimal work conditions were in the 3 year old coppice crop; however, the driving speed of the base machine (MTZ82 tractor) was still too high. The recommended speed in such conditions is 0.8-1.2 km·h-1. The yield obtained in the tests under these conditions in the 3 year old coppice crop was 2.4 tons of dry matter per hour. The productivity could be raised by increasing the power of the base machine. There is still space for technical improvements to avoid clogging of material in the chipper and jamming of saw blades, as well as to improve the quality of chips. [ABSTRACT FROM AUTHOR]

The study finds out the forest machine operators' opinion about the need for refresher courses, the quality of the courses, the knowledge and skills gained as a result of attending the courses. As part of the research, a questionnaire was compiled and sent to forest machine operators who have attended courses at the Forest Machine Operator Training Center in the last 4 years to improve their professional skills. The questionnaire was prepared and sent electronically at the end of 2021. Within two months, the questionnaire was completed by 147 operators. The aim of the survey is to find out the operators' opinion about attending refresher courses, and whether operators acquire the necessary knowledge and skills in refresher courses, which would increase their productivity. Among the surveyed operators, operators in the age group up to 30 years with work experience on the respective machine under 5 years were more interested in refresher courses, while operators in the age group over 41 years of age having work experience over 5 years were less interested in the refresher courses. It was found that 30% of forwarders and 33% of CTL (Cut-To-Length) harvester operators attend refresher courses on their initiative, while all forwarders operators and 65% of harvester operators attend refresher courses on the initiative of the employer. 75% of forwarder operators and 66% of harvester operators stated that they had acquired additional new knowledge and skills as a result of their training, as a result of which their professional qualification level as well as productivity increased. [ABSTRACT FROM AUTHOR]

Flooded Land is defined as water bodies where human activities have caused changes in the amount of surface area covered by water, typically through water level regulation. Former peat extraction fields are a type of flooded lands which are often mentioned as significant source of greenhouse gas (GHG) emissions. In Latvia, the area of flooded lands in former peat extraction fields is 5.3 kha. The aim of the study is to evaluate GHG emissions from flooded former peat extraction fields to define that the flooded lands are the key source of GHG emissions and approve that further studies are necessary to elaborate country specific emission factors. The study is implemented in three areas in central part of the country, where peat extraction was stopped 25-35 years ago. Measures continued for 12 months, in 9 subplots, each was represented by 3 measurement points. Water and air temperature, as well as water level was measured during the study. According to the study results, flooded areas are a significant source of CO2 emissions (967±107 kg CO2-C ha-1 yr-1); however, the most significant agent of GHG emissions in flooded areas is methane (CH4) - 435±98 kg CH4-C kg ha-1 yr-1. Flooded areas are not significant source of nitrous oxide (N2O) emissions. The net emissions from flooded areas are 18.1±3.7 tons CO2 eq ha-1 yr-1. According to the study results, flooded lands are a significant (one of the largest) source of emissions, and further studies are necessary to improve GHG modelling solutions and activity data. [ABSTRACT FROM AUTHOR]

Wood ash contains most of the nutrients necessary for development of plants, as well as soil microorganisms. It is well studied that application of wood ash improves forest growth in peatlands and significantly increases biomass production in the forest floor; however, there is limited knowledge on the shortterm impact on the soil GHG (CO2, N2O, CH4) fluxes after application of wood ash, specifically, if different doses of the wood ash are applied. The scope of the study is to determine short term (2 months) effect of application of 2, 5 and 10 tons⋅ha-1 of hardened and fresh wood ash in peat from abandoned peatland -- southern part of Kaigu mire (former raised bog). The study is implemented in controlled conditions (temperature and moisture) in a greenhouse. Peat from abandoned peatland is filled into 50 cm deep plastic boxes (area 50 x 70 cm) simulating 50 cm deep peat layer. The same amount of water is added regularly in all boxes to ensure that moisture level in peat remains close to natural conditions at the beginning of the experiment in control boxes. GHG fluxes are measured using Gasmet DX4040 FTIR analyser and opaque chambers. Measurement period 30 min. Measurements are repeated at least once per week. According to the study results directly after application of fresh wood ash peat acts as net sink of CO2 due to consumption of CO2 in chemical reactions; however, already in the second week after the application CO2 emissions from soil increase, while carbon losses from treated boxes in average were smaller by 59% in comparison to control boxes. No significant effect of wood ash is found on CH4 and N2O emissions and no significant difference was found between hardened and fresh wood ash. [ABSTRACT FROM AUTHOR]

The aim of the study is to evaluate greenhouse gas (GHG) fluxes from stems in black alder (Alnus glutinosa (L.) Gaertn.) and birch (Betula pendula Roth) stands with drained and naturally wet nutrient rich peat soils, as well as to evaluate correlation between the GHG fluxes, soil temperature and groundwater level. The study was implemented in 8 forest stands -- three black alder stands with nutrient rich peat soil (stand types according to national classification -- Dryopterioso-caricosa and Filipendulosa) and 5 birch stands with peat soil (stand type Oxalidosa turf. mel. and Dryopterioso-caricosa). Measurement of GHG fluxes was continued for 12 months using Gasmet DX4040 FTIR analyser and removable non-transparent chambers of fixed volume and area. GHG fluxes were measured at 0.5, 1.0 and 1.5 m height on 3 trees in every stand. According to the study results the average CH4 emissions from stem surface in birch stands are 6.9 ± 6.2 g CO2 eq m-2⋅yr-1 and in black alder stands 1.0 ± 3.2 g CO2 eq m-2⋅yr-1. Groundwater level significantly effects CH4 emissions -- if it remains above 15 cm during summer, the CH4 emissions from stem increases to 84.0 ± 25.2 g CO2 eq. m-2⋅yr-1. Tree stems in drained peat soils are not a source of CH4 emissions. According to the study results tree stems in peat soils are not producing N2O emissions. [ABSTRACT FROM AUTHOR]

The study aims to determine the applicability of the StanForD 2010 standard in the analysis of the impact of CTL harvester operator training on productivity. The productivity of harvester operators is affected by factors such as tree species, diameter, type of felling, terrain, operator experience, qualifications, and several other factors. However, there are not many studies that, in addition to the above-mentioned factors, have analyzed the impact of periodic training of operators on productivity. The study uses automatically obtained harvester production data from logging service providers. Data are from the John Deere harvester for the period July 2021 to December 2022. The harvester worked in cleaning cutting in the territory of the South Kurzeme forest district. The study used data acquired by two operators who received refresher training during the study period. Harvester Operator No. 1, has work experience of 6 years, and Operator No. 2 has work experience 12 years. Data on the development of four different species of trees in the two months before and two months after the training were used to determine the impact of operator training on productivity. Operator productivity was analyzed in three diameter groups for all species and separately for each tree species. The study found that using the automatically obtained data Operator No. 1 and Operator No. 2 average productivity after training increased by 7% and 29%, respectively. However, the effect of different stem diameters and tree species on productivity changes has been found. Operator No. 1 showed a decrease in productivity when processing deciduous trees in separate diameter groups, while Operator No. 2 showed a decrease in labour productivity in some conifer diameter groups. An indepth data analysis is needed to find out the reasons for the decline in productivity by expanding the data set used. [ABSTRACT FROM AUTHOR]

Forest mineral soil is one of the terrestrial carbon pools, and changes in forest management practices can affect the carbon stock in forest soil. The purpose of the study is to estimate temporal fertilization impact on mineral soil organic carbon stock, depending on fertilizers applied, forest stand type, different dominant tree species of the stands. Coniferous and birch forest stands with mineral soil in the central and eastern part of Latvia were selected for the experiment. The fertilizers used were wood ash and nitrogen containing mineral fertilizer. No significant differences in organic carbon stock in O horizon were detected 2–5 years after fertilization. A tendency of smaller organic carbon stock in upper mineral soil layers (0–10 cm, 10–20 cm) was found in most part of objects. Significantly smaller organic carbon stock was found in upper mineral soil layers (0–10 cm and 10–20 cm) in birch stands with wet mineral soil treated with ammonium nitrate if compared to the control plots, possibly due to a different soil moisture regime of forest stands. The positive and significant correlations between soil organic carbon and nitrogen stocks were found in most part of the objects. [ABSTRACT FROM AUTHOR]

The study compares 9 forest management scenarios in birch plantations in cropland and grassland with mineral and organic soils. Calculation period is 40 years for all scenarios. The study proves that establishment of birch plantations leads to reduction of greenhouse gas (GHG) emissions by 317-1776 tons of CO2 eq. ha-1 or 7.9-44.4 tons of CO2 eq. ha-1 per year. The reduction of GHG emissions in birch plantations is significantly influenced by growth conditions - in organic soils GHG emission reduction is 6 times higher than in mineral soils. In plantations with mineral soils most of the GHG emission reductions occur during 40 years after the establishment. In organic soils GHG emission reduction continues steadily due to reduction in GHG emissions from soils compared to alternative management scenarios (grassland or cropland). Harvested wood products and the substitution effect of biofuels play an important role in reducing GHG emissions, in particular through the assumption that wood products are recycled into biofuels at the end of their useful life. Recommended type of soil preparation in the most cases is mounding, but taking into account soil scarification costs, the number of target trees in the plantation must be reduced (down to 1500 per ha-1). Early tending, felling of young stands and regenerative felling must also be adapted to growing conditions by managing more intensively areas with fertile soils and less intensively - plantations with poor soils. In more fertile soils higher planting density may increase CO2 removals in the middle term. When planting 1500-2000 seedlings ha-1, moderately fertile soils ensures higher CO2 removals. According to the study results establishment of birch plantations in farmland is one of the most effective solutions for reducing GHG emissions in the land use, land use change and forestry (LULUCF), as well as in agriculture sector, especially, if organic soils are afforested. [ABSTRACT FROM AUTHOR]

The aim of the study is to clarify the compliance of machinery information systems used by Latvian logging service providers with the requirements of the Forest Machine Data and Communications Standard StanForD 2010. For determining the number of logging machines and structure registered in Latvia, data from the State Technical Control Agency of Latvia (VTUA) has been used. This dataset includes 2094 registered machinery units from which 1663 units recorded as harvesters and forwarders are distributed for data processing. Using the national AS Latvian State Forests (LSF) database, where 541 machinery units have been recorded, of which 239 harvesters and 302 forwarders, it is determined what and how many machines already use the standard StanForD 2010, how many machines can implement it and which machines are not suitable for the implementation of StanForD 2010. The study showed that the VTUA register does not fully reflect the true quantity of harvesting machines in Latvia and does not provide information about the use of machines. The LSF data provide reliable information on the possibilities of using StanForD 2010 in harvesters in national forests. From the harvesters working in the country’s forests, 52% of the machines uses the StanForD 2010 standard. Work should be continued to clarify the possible use of the standard in the machines working in private forests. Similarly, work should be continued with dealers of harvesting machines to identify models for which it is possible to adjust the StanForD 2010 standard and what the cost of adapting the indicative information systems is. [ABSTRACT FROM AUTHOR]

The aim of the study is to evaluate carbon stock in litter and organic forest soils in Latvia as well as to characterize accumulation of carbon in litter in afforested lands. The study is providing empirically valid information about soil and litter carbon changes for the National greenhouse gas (GHG) inventory by using data from National forest inventory (NFI), forest soil monitoring demonstration project BioSoil and other studies. The study proves significance of organic forest soil carbon pool in Latvia and demonstrates necessity to extend NFI incorporated forest soil monitoring program to improve data on soil density in wet organic soils, as well as to integrate data characterizing water regime in forests. The acquired data also proves that the conservative approach of calculation of carbon stock changes in litter in afforested lands applied in the Latvia’s National GHG inventory avoids overestimation of CO2 removals. The data on litter carbon stock collected in this study is sufficient to estimate total carbon stock for stands dominated by most common tree species and long term impact of changes of species composition. Measurements of organic soil and litter thickness should be continued by NFI and integrated with more detailed soil monitoring to increase accuracy of carbon stock estimates and gather data necessary for verification of modelling data, particularly in afforested lands and due to change of dominant species. [ABSTRACT FROM AUTHOR]

The aim of this study is to detect and to analyse individual trees and their heightin young and mature coniferous forest stands using local maxima method based on LiDAR (Light Detecting and Ranging) data, which are currently being obtained for the territory of Latvia. Empirical data about the tree height and number of trees for this study are obtained from the National forest inventory (NFI) sample plots and additional surveying is not conducted. LiDAR data are obtained from the Latvian Geospatial Information Agency. LiDAR surveying is done separately from NFI measurements. Sample plots are selected so that LiDAR data are obtained within 1 calendar year leeway from field measurements forNFI surveying of sample plots. Step by step instructions on the applied method are included in this paper. Average tree height and number of trees are compared between the remotely obtained and in field measurements based data sets. The best results are achieved in determination of the average tree height in mature forest stands. Remote sensing based data on the height and numberof trees in young forests is less accurate because of insufficient density of LiDAR point cloud and possible spatial offset of study plots in the NFI database. In order to obtain results with higher accuracy, LiDAR data with higher point density are needed. [ABSTRACT FROM AUTHOR]

The aim of the study is to evaluate the impact of drainage on soil carbon stock in a transitional mire drained for forestry. The study site is located in the central part of Latvia representing hemiboreal vegetation zone. Site was drained in 1960. It is located in a catchment area of the river Veseta. An undrained site at the same catchment area was chosen for control (ca. 2.5 km between sites). In both sites, the depth of peat is 4 - 4.5 m. Drained site is dominated by coniferous trees. Soil samples collected in 2014 were used to determine bulk density and carbon content, and to calculate soil carbon stock. Samples were collected down to 80 cm depth. Ground surface elevation was measured before and several times after the drainage to determine peat subsidence. Carbon stock has increased by 0.3 tons ha-1 yr¹ after drainage, although peat has subsided on average by 26 cm (13 - 48 cm). Subsidence was mainly caused by physical shrinkage of peat not by organic matter oxidation. Drainage was followed by compaction of aerated soil layer, which has caused most of the subsidence, especially during the first years after drainage. Soil bulk density has increased almost twice at soil surface layer 0 - 10 cm (from 75 kg m³ to 141 kg m³). Differences decrease at deeper sampling depths. It is concluded that drainage is not always followed by reduction of carbon stock in soil. Increased above and below ground litter production rates may offset accelerated decomposition of organic matter after drainage. [ABSTRACT FROM AUTHOR]

Waste water sewage sludge is one of municipal waste materials that could be used for nutrient recycling in agriculture, plantation forestry or re-cultivated areas. Sewage sludge contains at least 80 % of water and nutrient rich organic materials what could be used for fertilization of bare soils or for energy production instead of landing on landfills. The de-watering process of sludge by using the impulse method has less energy consumption and higher content of dry matter in the final product is reached in comparison with traditional drying. The aim of the study is to elaborate a method for sewage sludge drying, which allows saving the biological value of final organic material. Impulse interval, frequency, air pressure and temperature in the camera are the key factors for an economically effective process and reaching of qualitative final product. The product could be used for fertilization of non-food products, tree planting, perennial grasses for seed production etc. If sludge contains too high concentration of heavy metals, it could be burned for energy production, and just ashes deponent on landfills. The technological and energy consumption aspects of the methods were analyzed. For sewage sludge containing a low content of heavy metals. Drying is more sustainable after - and pretreatment methods before recycling of plant nutrient elements included in sludge organic material for farming. Transport of dried material is more economical as fresh mass, as well dry material does not smell. The barriers for implementation of these technologies into common practice are more political than technical. [ABSTRACT FROM AUTHOR]

Agroforestry, an ecologically and environmentally sustainable type of land use, offers great opportunity to sequestrate carbon in above- and below-ground carbon pools. Aspens (Populus spp.) are accepted as an agriculture energy crop with rotation period up to 5 years in Latvia since 2011. The research aim was to determine the productivity and removals of CO2 in a hybrid aspen (Populus tremula L. x P.tremuloides Michx.) plantation during the 5 years rotation period after managing the plantation as an agroforestry system together with perennial crops - reed canary grass (Phalaris arundinacea L.), festulolium (x Festulolium pabulare) and fodder galega (Galega orientalis Lam.), as intercrop, and fertilized with biogas production residues (30 tonnes.ha-1), wastewater sludge (10 tonnesDM.ha-1) and wood ash (6 tonnesDM.ha-1). The most important impact on the plantation's productivity has selection of the clone, although relevant impact on the tree growth was observed for fertilizer application and the type of intercrop. The most significant impact on the growth of the most productive clone No 4 demonstrated fertilization with biogas production residues and waste water sludge - 0.3-4.2 fresh tonnes of additional biomass compared to control without intercrop and without fertilizer. Comparing different intercrops, the best results were obtained with galega and red canary grass - 3.3 and 3.7 fresh tonnes of biomass higher stock in comparison to control unfertilized plots. The best combination was clone No 4 fertilized with wastewater sludge or biogas fermentation residues in combination with reed canary grass (Phalaris arundinacea L.) intercrop - 16.4 fresh tonnes of biomass (42 MWh of primary energy per hectare) or 16.5 tonnes.ha-1 of CO2 removed in above ground biomass (8.5 tonnesDM.ha-1). This study demonstrated that soil bulk density and organic carbon stock in upper soil layers decreased significantly during the 5 years after establishment of the fertilized hybrid aspen plantation in carbon rich mineral agricultural soil. [ABSTRACT FROM AUTHOR]

The aim of the study is to develop a methodology for assessment of the area and properties of buffer zones around drainage ditches and areas surrounding protective belts around natural streams, for transformation into "biomass factories". In Latvia and neighboring countries, these buffer zones have significant biofuel production, as well as climate change mitigation and nutrient retention potential. A GIS based algorithm using various data sources to obtain information about conditions and land use in buffer zones has been created. Spatial data about drainage diches and surrounding areas are obtained from the Latvian Rural Support Service, Corine land cover, State Forest Service and Latvian Geospatial Information Agency. In this study 15-meter buffers are defined for soil scarification, planting, tending, harvesting and biomass production for energy and other appliances. Using the methodology elaborated within this study, 706797 features of buffer polygons (buffer sides) were identified, each labelled with a unique number. Each polygon is labelled with a number that determines from which ditch line the buffer is derived. Total area of the generated buffers -- 167532 ha. The data obtained can make a significant contribution to assessing the potential of buffer zones suitable for establishment of shelter belts. [ABSTRACT FROM AUTHOR]

Rewetting grasslands with organic soils is an effective environmental strategy aimed at restoring natural water levels, crucial for mitigating GHG emissions. This process involves reintroducing water to previously drained or degraded peatlands, which helps in re-establishing wetland ecosystems. According to results of other studies rewetting slows down the decomposition of organic matter, significantly reducing carbon dioxide (CO2) emissions; however, can increase methane (CH4) emissions. Additionally, it supports biodiversity, enhances water quality, and can create new habitats for wetland species. This practice plays a vital role in climate change mitigation and ecosystem restoration. Our case study is implemented in former grassland near Smiltene, which was rewetted by closing culvert passing P27 road in late 80-ies during reconstruction of the road. Since that time the area is accumulating water from surrounding forests and farmlands. We measured GHG fluxes, groundwater, temperature, and other environmental parameters for two years once per month using the closed chamber method. Two-year measurements result that nearly 20-40 years after rewetting the grassland is still a significant source of GHG emissions – 6.04 tons CO2-C·ha-1 ·yr-1, 0.62 kg CH4·ha-1 ·yr-1 and 0.67 kg N2O·ha-1 ·yr-1. The net emissions from soil equal to 22.87 tons CO2·ha-1 ·yr-1. This is about twice less than from cropland, but about the same level of emissions as in grassland according to other studies implemented in Latvia. Thus, our study does not provide evidence that rewetting can reduce GHG emissions from organic soil. [ABSTRACT FROM AUTHOR]

Clear-felling, a predominant method for forest regeneration in areas with wet soils, has profound implications for greenhouse gas (GHG) emissions. This technique, by removing the forest cover, exposes the soil to increased sunlight, which can raise soil temperatures and enhance decomposition rates. Consequently, this process can significantly boost the emissions of carbon dioxide (CO2) and nitrous oxide (N2O). The absence of canopy cover also impacts soil moisture due to the decrease in plant transpiration, potentially leading to conditions that promote anaerobic processes in wet soils, thereby increasing methane (CH4) emissions. We monitored soil GHG (CO2, CH4, N2O) emissions in clear-felling sites before and after the harvesting. The study findings reveal a notable increase in CO2 emissions following the harvest, with an average rise of 226 mg CO2·m-2 ·h-1, representing a 120% increase. The CO2 emissions from mineral and organic soils did not significantly differ. While clear-felling had minimal impact on CH4 emissions from mineral soils, emissions from organic soils saw approximately a sixfold increase. Meanwhile, N2O emissions remained largely unchanged in both soil types post-clear-felling. When converted to CO2 equivalents, the emission results reveal a significant elevation in GHG emissions postclear-felling, particularly from organic soils which witnessed a near threefold increase, whereas emissions from mineral soils roughly doubled. The study results highlight the implications of even-aged forest management strategies on wet soil GHG emissions. [ABSTRACT FROM AUTHOR]

The scope of the study is to determine the effect of drainage of mineral soil in forest on nitrous oxide (N2O) and methane (CH4) emissions from soil. We evaluated N2O and CH4 fluxes from soil in pine and birch stands with moderately fertile drained and naturally wet mineral soil. The N2O and CH4 fluxes in naturally wet and drained mineral forest soils are crucial for understanding their respective roles in climate change dynamics and informing sustainable land management practices that can mitigate greenhouse gas emissions. The study was implemented in eighteen stands. We took gas samples periodically (once per month in average) using the opaque chamber method (45 measurement points in total) during 18 months period. Samples were analysed in laboratory using the gas chromatography method. It was assumed that N2O and CH4 fluxes are constant during the whole rotation period, while the average annual fluxes were calculated as sum of average monthly fluxes. We also measured the groundwater (GW) depth, soil and air temperature during the gas sampling and periodically took water samples from perforated water wells for chemical analyses. We found that all measurement sites are net sinks of CH4 removals and sources of N2O emissions. We did not find higher CH4 emissions in wet soil; however, one of the measurement years contained also one of the driest vegetation seasons, and GW level was deeper than usually, potentially resulting in reduction of CH4 emissions. We did not find correlation between the air temperature and N2O or CH4 emissions, as well as between the groundwater level and efflux of these gases. However, higher groundwater level in wet areas is associated with periodic extremes of N2O and CH4 emissions, which cannot be expressed by regression equations. If these extremes are considered, then wet mineral soils are a significant source of N2O emissions, however, they can also be omitted as a non-anthropogenic source. [ABSTRACT FROM AUTHOR]

Assessment of changes in carbon (C) stocks in mineral soils typically relies on the steady-state C stock values, which are influenced by various long-term land-use and management scenarios. This conventional approach limits understanding of the short-term soil C balance, including in lands not subject to land-use or management changes. Additionally, the role of the soil moisture condition impact on the mineral soil C balance is not broadly studied. To enhance our understanding of the effects of the soil moisture on C balances of mineral soils, this research conducted soil CO2 emission monitoring in forests with both drained and naturally wet mineral soils. The study was implemented across 18 forest sites with dominant species of aspen (Populus tremula L), birch (Betula pendula Roth, Betula pubescens Ehrh.), black alder (Alnus glutinosa (L.) Gärtner) and Scots pine (Pinus sylvestris L.). Emission monitoring was performed using the closed static opaque chamber method. Concurrent measurements of the soil temperature and the groundwater level depth were also conducted. Our research revealed that CO2 emissions resulting from soil respiration in both naturally wet and drained soils showed no notable differences, indicating that the mineral soil moisture regime has a minimal impact on C outflows from these soils. This finding implies that the C balance in mineral soils is largely dictated by the influx of C from vegetation residues and litter. Thus, for the conservation or enhancement of C stocks in mineral soils, maintaining the soil moisture regime that optimizes the decomposition and accumulation of vegetation litter is essential. [ABSTRACT FROM AUTHOR]

Organic soils are the largest source of GHG emissions in Latvia producing the amount of emissions comparable with the whole energy sector. Organic soils in cropland and grassland alone release about 4.5 mill. tonnes of CO2 eq. annually, which is nearly twice as big as the total emissions from the agriculture sector in Latvia. The reduction of the emissions from the organic soils is the primary target to implement the climate neutrality target in the post-2050 period in LULUCF sector. One of the issues in reporting of GHG emissions from organic soils is different definitions of organic soils, e.g. Latvia is using the Intergovernmental Panel on Climate Change (IPCC) definition (at least 10 cm deep peat layer and at least 12% of carbon content in upper 20 cm of the topsoil), while other countries use different criteria, e.g., at least 30 cm or 40 cm deep peat layer. The scope of this study is evaluating the effect of the peat layer thickness on GHG fluxes in grasslands. The study results proved that increase of the peat layer depth is associated with a trend of increase of CO2 and CH4 emissions. There is also strong correlation between CH4 emissions and the groundwater depth and soil temperature and CO2 emissions. N2O emissions are correlating with nitrogen content in soil. In the study sites soil turns into net source of CH4 emissions if the depth of peat layer exceeds 40 cm. The study results point that the peat depth should be considered as one of the parameters in accounting of GHG emissions. [ABSTRACT FROM AUTHOR]

The European Union (EU) has proposed legislative revisions to achieve climate neutrality in EU by 2050. The Land Use, Land-Use Change and Forestry (LULUCF) Regulation, adopted in 2018, is being revised to ensure that accounted greenhouse gas (GHG) emissions from LULUCF are balanced by equivalent accounted removals of carbon dioxide (CO2) from the atmosphere. This study focuses on the impact of targeted tree introduction in agricultural land in Latvia, specifically afforestation of drained organic soil and implementation of agroforestry systems (riparian buffer strips), on national GHG reduction targets for the LULUCF sector. The potential contributions of selected measures were evaluated using evaluation methods including GHG emissions factors based on the Intergovernmental Panel on Climate Change (IPCC) guidelines and recent scientific studies. The study differentiated between different land use categories by GHG emissions from soil and CO2 removals in living biomass, dead wood, litter, mineral soil, and organic soil. Basic scenarios were compared with additional scenarios that included afforestation of drained organic soils and implementation of agroforestry systems. The study analysed the possibilities of achieving LULUCF sector goals for 2030, 2035, and 2050 with the selected scenarios. According to the basic scenarios, the LULUCF sector has been a continuous source of GHG emissions since 2019, partly compensated by forest management by 2040, but after 2040 forest management becomes a source of GHG emissions as well. The study shows that afforestation of organic soils currently used for agricultural production can reduce GHG emissions and ensure the achievement of national LULUCF targets for 2021-2025, with a significant decrease in GHG emissions by 3.9 million t CO2 eq. during the 2021-2025 period if compared to the basic scenario. However, the study finds that national target of net GHG removals is not achieved for 2026-2030 according to both basic and afforestation scenarios if no additional measures, e.g., establishment of the shelter belts, are implemented. [ABSTRACT FROM AUTHOR]

The aim of the study is to evaluate the impact of the accumulating grapple on forwarding productivity in thinning in comparison to the standard grapple and to evaluate potential areas of application of accumulating grapples. Trials were conducted in 3 coniferous stands on nutrient-poor mineral soil with the total area of 15.2 ha. Two work methods are compared in the study - forwarding with a John Deere 1110D ECO III forwarder, equipped either with an accumulating grapple (first method) or a standard grapple (second method). According to the study results the use of the standard grapple results in slight increase of productivity (2.3 % per load and 1.4 % per m3 of logs). The difference is not significant, however additional trials are recommended to compare both grapples in more fertile forest stands with a larger number of assortments and extracted volumes, also in regenerative felling. According to the study results the prime forwarding cost is 9.4 EUR m-3, if the standard grapple is used and 9.5 EUR m-3, if the accumulating grapple is used. The difference is not significant. No significant difference is found between the methods also in terms of damages to the remaining trees. [ABSTRACT FROM AUTHOR]

The aim of the study was to evaluate the impact of the harvester head feed roller type on the fuel consumption and productivity during the spring season. This study compares feed rollers with moving metal plates on rubber shock absorbers (Moipu plate wheel rollers, hereinafter named - gentle feed rollers) and feed rollers with large round spikes (hereinafter named - conventional feed rollers). The study was conducted in Vidusdaugava forestry (forests managed by the Joint Stock Company Latvia State Forests). A total area of 18.69 ha or 19 felling sites were logged in the final felling with gentle feed rollers and 20.29 ha or 15 felling sites - with conventional feed rollers. Harvested spruce saw logs were delivered to Rettenmeier Baltic Timber Ltd, pine sawlogs to IKEA Industry Latvia Ltd and veneer logs to Latvijas Finieris Ltd. APonsse Ergo harvester manufactured in 2008 with a standard H7 felling head was used in the study. Logging tests were carried out in the spring and early summer, using standard logging work tasks with both feed roller types. According to the data from the harvester onboard computer the productivity was 27 m³·h-1 using the gentle feed rollers and 33 m3·h-1 using the conventional feed rollers. However, the comparison of productivity while processing the trees of the same diameter demonstrated slightly weaker performance with the gentle feed rollers. The difference is statistically significant if the tree diameter at the breast height is below 20 cm. Further studies are necessary to investigate the productivity depending on the season and felling type. Fuel consumption using the gentle feed rollers was 18.02 l·h-1 and using the conventional feed rollers it was 16.75 l·h-1. Fuel consumption by the roller type has a significant impact on both mean values (tStat = 2.6 > tCrit = 1.64) and data dispersion (F = 0.9 > FCrit = 0.8). [ABSTRACT FROM AUTHOR]

The impact of climatic and genetic factors on needle cast damage, as well as relationship between the degree of damage and survival and growth of trees was evaluated in the study. The analysis was done in two series of experiments, both established in two locations in Latvia (central and eastern part). Needle cast damage (in 5 grade scale) as well as the height and height increment, diameter of root collar and survival of trees were assessed. Results suggest that the degree of needle cast damage was influenced by the genetic, as well as climatic factors, and also their interaction. The average degree of needle cast damage in experiment of open-pollinated families was 4.7 ± 0.01 in central and 4.6 ± 0.03 in eastern Latvia; in the experiment of control-crossed families it was 4.6 ± 0.02 in central and 3.4 ± 0.04 in eastern Latvia. The impact of genetics on the needle cast damage degree was statistically significant (p<0.05), and this effect was observed when any of growth traits (diameter, height or height increment) was used as a covariate in analysis. Results suggest the potential to select more resistant families, since the genetic correlation of grade of the damage between locations was significant (r = 0.40 - 0.72) and therefore improve also the growth of trees, since the grade of the damage had a negative correlation with growth traits both at provenance and family mean level (r = -0.69 and r = -0.42; p<0.01). [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated the occurrence of different needle cast (Lophodermium spp.) species in young Scots pine Pinus sylvestris L. stands in different regions of Latvia. The impact of these fungi has been known also historically, but is predicted to increase in future due to climate changes that are forecasted to have a positive impact on presence and vigour of various species of fungi. The aim of the study was to characterize the needle cast damage in young Scots pine stands in central Latvia. Material was collected in 12 Scots pine stands at the age of 3 to 26 years in 28 plots with a total area of 8.1 ha in the middle of two consecutive growing seasons (years 2012 and 2013). The impact of disease was visually assessed using a 5 grade scale, depending on the proportion of damaged (brown) one-year old needles. Incidence of damaged trees (P, %) and damage intensity (R, %) was calculated and used to characterize the occurrence and severity of the infection in the stands as well as its link to other stand parameters. Damage incidence (ranging from 20 to 100%), as well as the intensity (from 4 to 35%) was slightly (incidence-also significantly) higher in 2013 in comparison to 2012; correlation between those two parameters was strong in both years (r = 0.94 and r = 0.84, respectively). The stand age, density (ranging from 1200 to 6900 trees ha-1) and tree height did not significantly correlate with the damage incidence or intensity. Forest type (Hylocomiosa or Myrtillosa mel.) was not a significant factor, too. [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated the occurrence of different needle cast (Lophodermium spp.) species in young Scots pine Pinus sylvestris L. stands in different regions of Latvia. The impact of these fungi has been known also historically, but is predicted to increase in future due to climate changes that are forecasted to have a positive impact on presence and vigour of various species of fungi. The aim of the study was to characterize the needle cast damage in young Scots pine stands in central Latvia. Material was collected in 12 Scots pine stands at the age of 3 to 26 years in 28 plots with a total area of 8.1 ha in the middle of two consecutive growing seasons (years 2012 and 2013). The impact of disease was visually assessed using a 5 grade scale, depending on the proportion of damaged (brown) one-year old needles. Incidence of damaged trees (P, %) and damage intensity (R, %) was calculated and used to characterize the occurrence and severity of the infection in the stands as well as its link to other stand parameters. Damage incidence (ranging from 20 to 100%), as well as the intensity (from 4 to 35%) was slightly (incidence-also significantly) higher in 2013 in comparison to 2012; correlation between those two parameters was strong in both years (r = 0.94 and r = 0.84, respectively). The stand age, density (ranging from 1200 to 6900 trees ha-1) and tree height did not significantly correlate with the damage incidence or intensity. Forest type (Hylocomiosa or Myrtillosa mel.) was not a significant factor, too. [ABSTRACT FROM AUTHOR]

The impact of climatic and genetic factors on needle cast damage, as well as relationship between the degree of damage and survival and growth of trees was evaluated in the study. The analysis was done in two series of experiments, both established in two locations in Latvia (central and eastern part). Needle cast damage (in 5 grade scale) as well as the height and height increment, diameter of root collar and survival of trees were assessed. Results suggest that the degree of needle cast damage was influenced by the genetic, as well as climatic factors, and also their interaction. The average degree of needle cast damage in experiment of open-pollinated families was 4.7 ± 0.01 in central and 4.6 ± 0.03 in eastern Latvia; in the experiment of control-crossed families it was 4.6 ± 0.02 in central and 3.4 ± 0.04 in eastern Latvia. The impact of genetics on the needle cast damage degree was statistically significant (p<0.05), and this effect was observed when any of growth traits (diameter, height or height increment) was used as a covariate in analysis. Results suggest the potential to select more resistant families, since the genetic correlation of grade of the damage between locations was significant (r = 0.40 - 0.72) and therefore improve also the growth of trees, since the grade of the damage had a negative correlation with growth traits both at provenance and family mean level (r = -0.69 and r = -0.42; p<0.01). [ABSTRACT FROM AUTHOR]