Simon Weldon

Forsker

(+47) 407 69 197
simon.weldon@nibio.no

Sted
Ås - Bygg O43

Besøksadresse
Oluf Thesens vei 43, 1433 Ås (Varelevering: Elizabeth Stephansens vei 23)

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Sorption of nutrients such as NH4+ is often quoted as a critical property of biochar, explaining its value as a soil amendment and a filter material. However, published values for NH4+ sorption to biochar vary by more than 3 orders of magnitude, without consensus as to the source of this variability. This lack of understanding greatly limits our ability to use quantitative sorption measurements towards product design. Here, our objective was to conduct a quantitative analysis of the sources of variability, and infer which biochar traits are more favourable to high sorption capacity. To do so, we conducted a standardized remodelling exercise of published batch sorption studies using Langmuir sorption isotherm. We excluded studies presenting datasets that either could not be reconciled with the standard Langmuir sorption isotherm or generated clear outliers. Our analysis indicates that the magnitude of sorption capacity of unmodified biochar for NH4+ is lower than previously reported, with a median of 4.2 mg NH4+ g−1 and a maximum reported sorption capacity of 22.8 mg NH4+ g−1. Activation resulted in a significant relative improvement in sorption capacity, but absolute improvements remain modest, with a maximum reported sorption of 27.56 mg NH4+ g−1 for an activated biochar. Methodology appeared to substantially impact sorption estimates, especially practices such as pH control of batch sorption solution and ash removal. Our results highlight some significant challenges in the quantification of NH4+ sorption by biochar and our curated data set provides a potentially valuable scale against which future estimates can be assessed.

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Peatlands have acted as net CO2 sinks over millennia, exerting a global climate cooling effect. Rapid warming at northern latitudes, where peatlands are abundant, can disturb their CO2 sink function. Here we show that sensitivity of peatland net CO2 exchange to warming changes in sign and magnitude across seasons, resulting in complex net CO2 sink responses. We use multiannual net CO2 exchange observations from 20 northern peatlands to show that warmer early summers are linked to increased net CO2 uptake, while warmer late summers lead to decreased net CO2 uptake. Thus, net CO2 sinks of peatlands in regions experiencing early summer warming, such as central Siberia, are more likely to persist under warmer climate conditions than are those in other regions. Our results will be useful to improve the design of future warming experiments and to better interpret large-scale trends in peatland net CO2 uptake over the coming few decades.

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Biochar has been shown to reduce nitrous oxide (N2O) emissions from soils, but the effect is highly variable across studies and the mechanisms are under debate. To improve our mechanistic understanding of biochar effects on N2O emission, we monitored kinetics of NO, N2O and N2 accumulation in anoxic slurries of a peat and a mineral soil, spiked with nitrate and amended with feedstock dried at 105 °C and biochar produced at 372, 416, 562 and 796 °C at five different doses. Both soils accumulated consistently less N2O and NO in the presence of high-temperature chars (BC562 and BC796), which stimulated reduction of denitrification intermediates to N2, particularly in the acid peat. This effect appeared to be strongly linked to the degree of biochar carbonisation as predicted by the H:C ratio of the char. In addition, biochar surface area and pH were identified as important factors, whereas ash content and CEC played a minor role. At low pyrolysis temperature, the biochar effect was soil dependent, suppressing N2O accumulation in the mineral soil, but enhancing it in the peat soil. This contrast was likely due to the labile carbon content of low temperature chars, which contributed to immobilise N in the mineral soil, but stimulated denitrification and N2O emission in the peat soil. We conclude that biochar with a high degree of carbonisation, high pH and high surface area is best suited to supress N2O emission from denitrification, while low temperature chars risk supporting incomplete denitrification.

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I denne rapporten har vi undersøkt i hvilken grad restaurering av myr kan bidra til ny karbonlagring og samtidig reduserte klimagassutslipp. Et litteraturstudium viser at drenert myr er en langt større kilde til CO2-utslipp enn både naturlig og restaurert myr. Årsaken til den høye CO2-emisjonen i drenert myr er lavere grunnvannstand, tilgang på oksygen og økt jordrespirasjon. Høy grunnvannstand i naturlig og restaurert myr motvirker jordrespirasjonen og bidrar til lagring av karbon i jorda. Restaurering av myr vil derfor som regel redusere karbontapet, og kan, avhengig av forholdene på stedet, gjenskape området til et karbonsluk.

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Greenhouse gas (GHGs) emissions from peatlands contribute significantly to ongoing climate change because of human land use. To develop reliable and comprehensive estimates and predictions of GHG emissions from peatlands, it is necessary to have GHG observations, including carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), that cover different peatland types globally. We synthesize published peatland studies with field GHG flux measurements to identify gaps in observations and suggest directions for future research. Although GHG flux measurements have been conducted at numerous sites globally, substantial gaps remain in current observations, encompassing various peatland types, regions and GHGs. Generally, there is a pressing need for additional GHG observations in Africa, Latin America and the Caribbean regions. Despite widespread measurements of CO2 and CH4, studies quantifying N2O emissions from peatlands are scarce, particularly in natural ecosystems. To expand the global coverage of peatland data, it is crucial to conduct more eddy covariance observations for long-term monitoring. Automated chambers are preferable for plot-scale observations to produce high temporal resolution data; however, traditional field campaigns with manual chamber measurements remain necessary, particularly in remote areas. To ensure that the data can be further used for modeling purposes, we suggest that chamber campaigns should be conducted at least monthly for a minimum duration of one year with no fewer than three replicates and measure key environmental variables. In addition, further studies are needed in restored peatlands, focusing on identifying the most effective restoration approaches for different ecosystem types, conditions, climates, and land use histories.

Sammendrag

Rapporten er utarbeidet på oppdrag for Rogaland fylkeskommune og viser mengden og fordelingen av karbonrikt areal i Rogaland. Den viser også utslipps- og opptak av klimagasser angitt i tonn CO2-ekvivalenter fra nåværende bruk, historisk endret bruk og planlagt fremtidig nedbygging. Rapporten diskuterer videre utviklingen fremover i lys av historiske utviklingstrekk i arealbruk og arealbruksendringer i Rogaland. Analysen bygger på datagrunnlaget som brukes i det nye kommunevise klimagassregnskapet for arealbrukssektoren, samt en sammenstilling av kommunenes gjeldende arealplaner ved inngangen til 2023.

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Peatlands cover only 3–4% of the Earth’s surface, but they store nearly 30% of global soil carbon stock. This significant carbon store is under threat as peatlands continue to be degraded at alarming rates around the world. It has prompted countries worldwide to establish regulations to conserve and reduce emissions from this carbon rich ecosystem. For example, the EU has implemented new rules that mandate sustainable management of peatlands, critical to reaching the goal of carbon neutrality by 2050. However, a lack of information on the extent and condition of peatlands has hindered the development of national policies and restoration efforts. This paper reviews the current state of knowledge on mapping and monitoring peatlands from field sites to the globe and identifies areas where further research is needed. It presents an overview of the different methodologies used to map peatlands in nine countries, which vary in definition of peat soil and peatland, mapping coverage, and mapping detail. Whereas mapping peatlands across the world with only one approach is hardly possible, the paper highlights the need for more consistent approaches within regions having comparable peatland types and climates to inform their protection and urgent restoration. The review further summarises various approaches used for monitoring peatland conditions and functions. These include monitoring at the plot scale for degree of humification and stoichiometric ratio, and proximal sensing such as gamma radiometrics and electromagnetic induction at the field to landscape scale for mapping peat thickness and identifying hotspots for greenhouse gas (GHG) emissions. Remote sensing techniques with passive and active sensors at regional to national scale can help in monitoring subsidence rate, water table, peat moisture, landslides, and GHG emissions. Although the use of water table depth as a proxy for interannual GHG emissions from peatlands has been well established, there is no single remote sensing method or data product yet that has been verified beyond local or regional scales. Broader land-use change and fire monitoring at a global scale may further assist national GHG inventory reporting. Monitoring of peatland conditions to evaluate the success of individual restoration schemes still requires field work to assess local proxies combined with remote sensing and modeling. Long-term monitoring is necessary to draw valid conclusions on revegetation outcomes and associated GHG emissions in rewetted peatlands, as their dynamics are not fully understood at the site level. Monitoring vegetation development and hydrology of restored peatlands is needed as a proxy to assess the return of water and changes in nutrient cycling and biodiversity.

Sammendrag

NIBIO har overvåket og vurdert risikoaspektene ved tungmetallopptak i matplanter gjennom et kunnskapsutviklingsprosjekt som rapporteres her. NIBIO foreslår at det foretas en systematisk kartlegging av alunskiferjord basert på kjemiske analyser. Dette vil dokumentere omfanget samt redusere risiko for overskridelser ved å øke forutsigbarheten for dyrkere. Videre vil det være et viktig grunnlag for å vurdere hvordan EUs nye grenseverdier kan håndteres i Norge, herunder situasjoner med grønsaksavlinger som overskrider grenseverdiene. Sistnevnte vil være av stor betydning for grønnsaksprodusenter i alunskiferområder.

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Sorption of nutrients such as NH4+ is often quoted as a critical property of biochar, explaining its value as a soil amendment and a filter material. However, published values for NH4+ sorption to biochar vary by more than 3 orders of magnitude, without consensus as to the source of this variability. This lack of understanding greatly limits our ability to use quantitative sorption measurements towards product design. Here, our objective was to conduct a quantitative analysis of the sources of variability, and infer which biochar traits are more favourable to high sorption capacity. To do so, we conducted a standardized remodelling exercise of published batch sorption studies using Langmuir sorption isotherm. We excluded studies presenting datasets that either could not be reconciled with the standard Langmuir sorption isotherm or generated clear outliers. Our analysis indicates that the magnitude of sorption capacity of unmodified biochar for NH4+ is lower than previously reported, with a median of 4.2 mg NH4+ g−1 and a maximum reported sorption capacity of 22.8 mg NH4+ g−1. Activation resulted in a significant relative improvement in sorption capacity, but absolute improvements remain modest, with a maximum reported sorption of 27.56 mg NH4+ g−1 for an activated biochar. Methodology appeared to substantially impact sorption estimates, especially practices such as pH control of batch sorption solution and ash removal. Our results highlight some significant challenges in the quantification of NH4+ sorption by biochar and our curated data set provides a potentially valuable scale against which future estimates can be assessed.

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En oppsummering av utredning som tar hensyn til både vitenskapelige funn og praktisk erfaring viser: Positive effekter mht. forbedring av jordkvalitet, men begrenset avlingseffekt i Norden Samlete funn fra internasjonal forskning viser generelt at biokull bidrar positivt til både forbedring av jordkvalitet og avling. Forskning fra Norge og Norden viser en beskjeden positiv effekt på jordkvalitet, og ingen effekt på planteavling når ubehandlet biokull ble tiført dyrkingsjorda. Innblanding av biokull i næringsrik biorest (fra biogassanlegg) har enten ingen eller en liten positiv effekt på planteavlinger, og vi anbefaler mer forskning for optimalisering for slik bruk. Biokull kan forbedre komposteringprosesser og redusere klimagassutslipp under kompostering Biokull bidrar positivt til forbedring av komposteringsprosesser, og de fleste studier viser en reduksjon i produksjon av N2O og CH4 under kompostering med biokull, samt redusert tap av NH3. Effekten av biokull er størst når biokull tilsettes ved oppstart av en komposteringsprosess. Biokulltilsetning gir raskere kompostering og et mer stabilt og hygienisert produkt. Kompost-biokull-blandinger gir ikke økt planteavling sammenlignet med kompost uten biokull. Biokull i gjødselvarer kan gi økt avling, og bedre utnytelse av næringsstoffer, men teknologien trenger videre utvikling og det finnes ingen slike produkter på markedet i Norge. Internasjonal forskning viser at når biokull brukes som del av en gjødselvare, øker avlingene i snitt med ca. 17% sammenlignet med kontrollbehandlinger med samme mengde N-gjødsling, men uten biokull. Binding av næringsstoffer på biokulloverflater krever mer avansert teknologi enn opprinnelig antatt. Mens mye forskning pågår internasjonalt og i Norge, har vi ingen produkter på markedet i Norge for utprøving. Utvikling av biokullfilter for gjenvinning av NH3 i gjødselværer kan også bli en lovende teknologi. Biokull i fôr til husdyr kan bedre dyrehelse Tilskudd av biokull i dietten til fjørfe, svin og drøvtyggere har vist å kunne bedre dyrehelse og redusere sykdom forårsaket av en rekke patogene bakterier. Undersøkelsene er utenlandske, og det er ikke gjennomført forsøk i Norge som kan vise slike resultater. Forsøk gjennomført av NIBIO viser at tilsetning av 2 % biokull i fôret til lam i 6 uker ikke påvirket totalt fôropptak. Tilsetning av biokull ved fôring av smågris utført på gårder i Innlandet viste redusert forekomst av diaré, og i noen tilfeller vektøkning. Ellers varierte resultatene mellom dyreinnsett, uten klare positive eller negative effekter. Varierende effekter på binding av tungmetaller, avhengig av jordtype og type biokull Forsøk med ulike typer forurenset og naturlig tungmetallrik jord (bl.a. alunskiferjord) der biokull ble tilsatt for å redusere opptak i planter, har vist varierende effekt mht. ulike tungmetaller, ulike typer biokull og ulike typer jord og planter. Biokull med gode bindingsegenskaper bør testes for å optimalisere denne anvendelsen.

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Background Biochar-based fertilizer products (BCF) have been reported to increase both crop yield and N-use efficiency. Such positive effects are often assumed to result from the slow-release of N adsorbed on BCF structures. However, a careful review of the literature suggests that actual mechanisms remain uncertain, which hampers the development of efficient BCF products. Scope Here, we aim at reviewing BCF mechanisms responsible for enhanced N uptake by plants, and evaluate the potential for further improvement. We review the capacity of biochar structures to adsorb and release N forms, the biochar properties supporting this effect, and the methods that have been proposed to enhance this effect. Conclusions Current biochar products show insufficient sorption capacity for the retention of N forms to support the production of slow-release BCFs of high enough N concentration. Substantial slow-release effects appear to require conventional coating technology. Sorption capacity can be improved through activation and additives, but currently not to the extent needed for concentrated BCFs. Positive effects of commercial BCFs containing small amount of biochar appear to result from pyrolysis-derived biostimulants. Our review highlights three prospects for improving N retention: 1) sorption of NH3 gas on specifically activated biochar, 2) synergies between biochar and clay porosities, which might provide economical sorption enhancement, and 3) physical loading of solid N forms within biochar. Beyond proof of concept, quantitative nutrient studies are needed to ascertain that potential future BCFs deliver expected effects on both slow-release and N use efficiency.

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Peatlands have acted as net CO2 sinks over millennia, exerting a global climate cooling effect. Rapid warming at northern latitudes, where peatlands are abundant, can disturb their CO2 sink function. Here we show that sensitivity of peatland net CO2 exchange to warming changes in sign and magnitude across seasons, resulting in complex net CO2 sink responses. We use multiannual net CO2 exchange observations from 20 northern peatlands to show that warmer early summers are linked to increased net CO2 uptake, while warmer late summers lead to decreased net CO2 uptake. Thus, net CO2 sinks of peatlands in regions experiencing early summer warming, such as central Siberia, are more likely to persist under warmer climate conditions than are those in other regions. Our results will be useful to improve the design of future warming experiments and to better interpret large-scale trends in peatland net CO2 uptake over the coming few decades.

Sammendrag

Biochar-based fertilizer products (BCF) are receiving increasing attention as potential win-win solutions for mitigating climate change and improving agricultural production. BCFs are reported to increase yields through increased N use efficiency, an effect which is often assumed to result from the slow-release of adsorbed N forms into the soil. Here, we review the magnitude of this effect, the potential for further improvement and the need to consider other mechanisms in product development. Current high-N commercial BCFs are mostly physical blends of biochar and mineral fertilizer, with little evidence of slow-release effects supported by sorption mechanisms. For such products, the main effect potentially results from root-growth promoting factors and from increases in soil pH and Eh and stimulation of beneficial micro-organisms in the rhizosphere, which all result in an increase in uptake of specific nutrients. Our reanalysis of literature data indicates that the median sorption capacity of untreated biochar for mineral N forms requires applying 200 times more biochar than N fertilizer. This ratio needs reducing by at least an order of magnitude for producing efficient sorption-based BCFs. Activation of biochar with acids and oxidizing agents, as reported in many studies, appears to only marginally increase sorption capacity in absolute values. Fixation of clay and organics within the porous structure of biochar appears a more promising technology, suggesting that macro- and mesoporosity is a key biochar property that deserves greater scrutiny and research towards making efficient sorption-based BCFs. Mechanisms of action and dose responses need to be more systematically studied in order to devise products that combine positive effects and can be used within realistic agronomic management practices. Long-term effects resulting from accumulated annual inputs of BCF also need to be better evaluated in terms of nutrient cycling and the progressive improvement of soil health.

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Limiting temperature rise below 2 °C requires large deployment of Negative Emission Technologies (NET) to capture and store atmospheric CO2. Compared to other types of NETs, biochar has emerged as a mature option to store carbon in soils while providing several co-benefits and limited trade-offs. Existing life-cycle assessment studies of biochar systems mostly focus on climate impacts from greenhouse gasses (GHGs), while other forcing agents, effects on soil emissions, other impact categories, and the implications of a large-scale national deployment are rarely jointly considered. Here, we consider all these aspects and quantify the environmental impacts of application to agricultural soils of biochar from forest residues available in Norway considering different scenarios (including mixing of biochar with synthetic fertilizers and bio-oil sequestration for long-term storage). All the biochar scenarios deliver negative emissions under a life-cycle perspective, ranging from -1.72 ± 0.45 tonnes CO2-eq. ha−1 yr−1 to -7.18 ± 0.67 tonnes CO2-eq. ha−1 yr−1 (when bio-oil is sequestered). Estimated negative emissions are robust to multiple climate metrics and a large range of uncertainties tested with a Monte-Carlo analysis. Co-benefits exist with crop yields, stratospheric ozone depletion and marine eutrophication, but potential trade-offs occur with tropospheric ozone formation, fine particulate formation, terrestrial acidification and ecotoxicity. At a national level, biochar has the potential to offset between 13% and 40% of the GHG emissions from the Norwegian agricultural sector. Overall, our study shows the importance of integrating emissions from the supply chain with those from agricultural soils to estimate mitigation potentials of biochar in specific regional contexts.

Sammendrag

Several scientific groups have concluded that the use of biochar as an on-farm management tool for carbon sequestration should be further investigated. Review articles also pinpoint the use of biochar to reduce greenhouse gas emissions from the entire agricultural production, and this should be studied using whole-chain models. Biochar is added to animal diets with the main purpose of enhancing animal health. There are indications that biochar fed to ruminants may reduce enteric methane emission. Twenty-four ewe lambs were fed one of two diets, a control diet (no biochar) and a biochar diet (1.4% biochar). There were no differences in dry matter intake and average daily growth rate between animals. An expected reduction in enteric methane emissions from animals fed the biochar diet was not detected. We conclude that the effect on enteric methane emissions may depend on structure and properties of the biochar offered. We suggest further research on biomass and pyrolysis of biochar to accommodate several properties as a feed additive for farm animals.

Sammendrag

At the Norwegian Institute of Bioeconomy Research (NIBIO, formerly Bioforsk), biochar has been a topic of research since 2009 through both laboratory and field studies. Initial results demonstrated that biochar produced from clean biomass is safe to use on agricultural soils, and that pyrolysis temperatures of ≥370 °C are necessary for producing biochar that is resistant to decomposition on a timescale of 100 years. Further work identified the chemical transformations that are responsible for biochar stability and contributed to finding the best indicator of this stability. Throughout the years, we have had close collaboration with industry and farmers in Norway, where now industrial networks are in action and there is financial support for the implementation of biochar technology. Despite the convincing benefits of biochar as a climate mitigation solution, it has only slowly advanced beyond the research stage, notably because its effect on yield are too modest. There is therefore a need for win-win biochar solutions benefiting both food production and climate mitigation. Such a solution is the development of biochar fertilizers, which capitalizes on the capacity of biochar to capture and release nutrients. As biochar properties largely depend on pyrolysis conditions and feedstock properties, our current work contributes to the selective design of biochars for the purpose of improving nutrient use efficiency.

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Biochar has been shown to reduce nitrous oxide (N2O) emissions from soils, but the effect is highly variable across studies and the mechanisms are under debate. To improve our mechanistic understanding of biochar effects on N2O emission, we monitored kinetics of NO, N2O and N2 accumulation in anoxic slurries of a peat and a mineral soil, spiked with nitrate and amended with feedstock dried at 105 °C and biochar produced at 372, 416, 562 and 796 °C at five different doses. Both soils accumulated consistently less N2O and NO in the presence of high-temperature chars (BC562 and BC796), which stimulated reduction of denitrification intermediates to N2, particularly in the acid peat. This effect appeared to be strongly linked to the degree of biochar carbonisation as predicted by the H:C ratio of the char. In addition, biochar surface area and pH were identified as important factors, whereas ash content and CEC played a minor role. At low pyrolysis temperature, the biochar effect was soil dependent, suppressing N2O accumulation in the mineral soil, but enhancing it in the peat soil. This contrast was likely due to the labile carbon content of low temperature chars, which contributed to immobilise N in the mineral soil, but stimulated denitrification and N2O emission in the peat soil. We conclude that biochar with a high degree of carbonisation, high pH and high surface area is best suited to supress N2O emission from denitrification, while low temperature chars risk supporting incomplete denitrification.

Sammendrag

Biochar is a carbon-rich material that, due to its inherent resistance to decomposition, is primarily developed with the aim of sequestering carbon in soil. Despite the convincing benefits of biochar as a climate mitigation solution, it has not yet advanced much beyond the research stage, notably because its effect on yield are too modest. Therefore, there is a need for win-win biochar solutions benefiting both food production and climate mitigation. Such a solution is the development of biochar fertilizers, which capitalizes on the capacity of biochar to capture and release nutrients. This effect is largely attributed to the porous structure and large surface area of biochar, with surface charges and ash content also appearing to play a role. The nutrient-retaining capacity of biochar appears to vary among studies investigating different types of biochar exposed to different types of nutrients (mineral anions and cations, organic molecules) under different conditions. In the present study, we will report on a meta-analysis of published biochar properties that are associated with controlling the sorption of nutrients. As biochar properties largely depend on pyrolysis conditions and feedstock properties, this work contributes to the selective design of biochars for the purpose of improving nutrient use efficiency.

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Heavy metal contamination of crop lands surrounding mines in North Vietnam is a major environmental issue for both farmers and the population as a whole. Technology for the production of biochar at a village and household level has been successfully introduced into Vietnamese villages. This study was undertaken to determine if rice straw biochar produced in simple drum ovens could remediate contaminated land. Tests were also carried out to determine if biochar and apatite mixed together could be more effective than biochar alone. Incubation trials were carried out over 90 days in pots to determine the total changes in exchangeable Cd, Pb and Zn. Detailed tests were carried out to determine the mechanisms that bound the heavy metals to the biochar. It was found that biochar at 5% (BC5) and the mixture of biochar and apatite at 3% (BCA3) resulted in the greatest reduction of exchangeable forms of Cd, Pb and Zn. The increase in soil pH caused by adding biochar and apatite created more negative charge on the soil surface that promoted Pb, Zn and Cd adsorption. Heavy metals were mainly bound in the organic, Fe/Mn and carbonate fractions of the biochar and the mixture of biochar and apatite by either ion exchange, adsorption, dissolution/precipitation and through substitution of cations in large organic molecules.

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The application of biochar to soils is a promising technique for increasing soil organic C and offsetting GHG emissions. However, large-scale adoption by farmers will likely require the proof of its utility to improve plant growth and soil quality. In this context, we conducted a four-year field experiment between October 2010 to October 2014 on a fertile silty clay loam Albeluvisol in Norway to assess the impact of biochar on soil physical properties, soil microbial biomass, and oat and barley yield. The following treatments were included: Control (soil), miscanthus biochar 8 t C ha1 (BC8), miscanthus straw feedstock 8 t C ha1 (MC8), and miscanthus biochar 25 t C ha1 (BC25). Average volumetric water content at field capacity was significantly higher in BC25 when compared to the control due to changes in BD and total porosity. The biochar amendment had no effect on soil aggregate (2–6 mm) stability, pore size distribution, penetration resistance, soil microbial biomass C and N, and basal respiration. Biochar did not alter crop yields of oat and barley during the four growing seasons. In order to realize biochar’s climate mitigation potential, we suggest future research and development efforts should focus on improving the agronomic utility of biochar in engineered fertilizer and soil amendment products.

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Extreme winter events that damage vegetation are considered an important climatic cause of arctic browning—a reversal of the greening trend of the region—and possibly reduce the carbon uptake of northern ecosystems. Confirmation of a reduction in CO2 uptake due to winter damage, however, remains elusive due to a lack of flux measurements from affected ecosystems. In this study, we report eddy covariance fluxes of CO2 from a peatland in northern Norway and show that vegetation CO2 uptake was delayed and reduced in the summer of 2014 following an extreme winter event earlier that year. Strong frost in the absence of a protective snow cover—its combined intensity unprecedented in the local climate record—caused severe dieback of the dwarf shrub species Calluna vulgaris and Empetrum nigrum. Similar vegetation damage was reported at the time along ~1000 km of coastal Norway, showing the widespread impact of this event. Our results indicate that gross primary production (GPP) exhibited a delayed response to temperature following snowmelt. From snowmelt up to the peak of summer, this reduced carbon uptake by 14 (0–24) g C m−2 (~12% of GPP in that period)—similar to the effect of interannual variations in summer weather. Concurrently, remotely-sensed NDVI dropped to the lowest level in more than a decade. However, bulk photosynthesis was eventually stimulated by the warm and sunny summer, raising total GPP. Species other than the vulnerable shrubs were probably resilient to the extreme winter event. The warm summer also increased ecosystem respiration, which limited net carbon uptake. This study shows that damage from a single extreme winter event can have an ecosystem-wide impact on CO2 uptake, and highlights the importance of including winter-induced shrub damage in terrestrial ecosystem models to accurately predict trends in vegetation productivity and carbon sequestration in the Arctic and sub-Arctic.

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Management of peat soils is regionally important as they cover large land areas and have important but conflicting ecosystems services. A recent management trend for drained peatlands is the control of greenhouse gases (GHG) by changes in agricultural practices, peatland restoration or paludiculture. Due to complex antagonistic controls of moisture, water table management can be difficult to use as a method for controlling GHG emissions. Past studies show that there is no obvious relationship between GHG emission rates and crop type, tillage intensity or fertilization rates. For drained peat soils, the best use options can vary from rewetting with reduced emission to efficient short term use to maximize the profit per amount of greenhouse gas emitted. The GHG accounting should consider the entire life cycle of the peatland and the socio-economic benefits peatlands provide locally. Cultivating energy crops is a viable option especially for wet peat soils with poor drainage, but harvesting remains a challenge due to tractability of wet soils. Paludiculture in lowland floodplains can be a tool to mitigate regional flooding allowing water to be stored on these lands without much harm to crops. This can also increase regional biodiversity providing important habitats for birds and moisture tolerant plant species. However, on many peatlands rewetting is not possible due to their position in the landscape and the associated difficulty to maintain a high stable water table. While the goal of rewetting often is to encourage the return of peat forming plants and the ecosystem services they provide such as carbon sequestration, it is not well known if these plants will grow on peat soils that have been altered by the process of drainage and management. Therefore, it is important to consider peat quality and hydrology when choosing management options. Mapping of sites is recommended as a management tool to guide actions. The environmental status and socio-economic importance of the sites should be assessed both for continued cultivation but also for other ecosystem services such as restoration and hydrological functions (flood control). Farmers need advice, tools and training to find the best after-use option. Biofuels might provide a cost-efficient after use option for some sites. Peat extraction followed by rewetting might provide a sustainable option as rewetting is often easier if the peat is removed, starting the peat accumulation from scratch. Also this provides a way to finance the after-use. As impacts of land use are uncertain, new policies should consider multiple benefits and decisions should be based on scientific evidence and field scale observations. The need to further understand the key processes and long term effects of field scale land use manipulations is evident. The recommended actions for peatlands should be based on local condition and socio-economic needs to outline intermediate and long term plans.

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Rapporten viser resultatene fra vegetasjonsundersøkelser og klimagassutslipp på et prøvefelt for restaurering av dyrket myr som er tatt ut av drift. Tidligere dyrking av hatt effekt på vegetasjonen i lang tid. Etter 35 år ute av drift er vegetasjonen fortsatt mer lik dyrket enn udyrket myr. Blokkering av kanaler har ført til høyere grunnvannsstand og reduserte CO2-utslipp. Utslippene av metan var negativt (ikke signifikant) korrelert med grunnvannstanden og var dessuten korrelert med frekvensen av svampvevede plantearter. Permanent høytstående grunnvann og rask etablering av opprinnelig myrvegetasjon ser ut til å være en forutsetning for framtidig karbonbinding og lave klimagassutslipp fra restaurert myr.

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I denne rapporten har vi undersøkt i hvilken grad restaurering av myr kan bidra til ny karbonlagring og samtidig reduserte klimagassutslipp. Et litteraturstudium viser at drenert myr er en langt større kilde til CO2-utslipp enn både naturlig og restaurert myr. Årsaken til den høye CO2-emisjonen i drenert myr er lavere grunnvannstand, tilgang på oksygen og økt jordrespirasjon. Høy grunnvannstand i naturlig og restaurert myr motvirker jordrespirasjonen og bidrar til lagring av karbon i jorda. Restaurering av myr vil derfor som regel redusere karbontapet, og kan, avhengig av forholdene på stedet, gjenskape området til et karbonsluk.

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Sammendrag

NIBIO har gjennomført et pilotprosjekt med restaurering av tidligere dyrket myr på Smøla. Høytstående grunnvann og re-etablering av opprinnelig myrvegetasjon er de viktigste faktorene for å øke karbonlagringen og reduserer klimagassutslippene.

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Northern peatlands hold large amounts of organic carbon (C) in their soils and are as such important in a climate change context. Blanket bogs, i.e. nutrient-poor peatlands restricted to maritime climates, may be extra vulnerable to global warming since they require a positive water balance to sustain their moss dominated vegetation andCsink functioning. This study presents a 4.5 year record of land– atmosphere carbon dioxide (CO2) exchange from the Andøya blanket bog in northern Norway. Compared with other peatlands, the Andøya peatland exhibited low flux rates, related to the low productivity of the dominating moss and lichen communities and the maritime settings that attenuated seasonal temperature variations. It was observed that under periods of high vapour pressure deficit, net ecosystem exchange was reduced, which was mainly caused by a decrease in gross primary production. However, no persistent effects of dry conditions on theCO2 exchange dynamics were observed, indicating that under present conditions and within the range of observed meteorological conditions the Andøya blanket bog retained its Cuptake function. Continued monitoring of these ecosystem types is essential in order to detect possible effects of a changing climate. peatland, carbon, blanket bog, eddy covariance, climate change, net ecosystem exchange

Sammendrag

Studies examining the effect of biochar on N2O turnover in soil have demonstrated that biochar affects both the rate and product ratio of denitrification. The mechanisms proposed include pH effects on N2O reductase , sorption of N2O and electron shuttling to N2O reductases. Recent studies suggest that pyrolysis alters the redox chemistry of biochar leading to the formation of redox active compounds which are thought to mediate the observed suppression of N2O in biochar amended soil. Redox active components however may not only be of significance to biological processes but also catalyze abiotic reactions of N-species which could confound the estimation of biological effects. Here we report experiments designed to examined abiotic interaction between biochar and NO in anoxic water slurries with biochar of increasing pyrolysis temperature. We determined the fate of NO added to the headspace of closed anoxic bottles using high frequency measurements of NO, N2O and N2. Our initial results show a swift disappearance of added NO which can not entirely be attributed to sorption to the biochar. Small but constant quantities of N2O were generated after NO addition indicating abiotic turnover of NO by biochar. NO is an important signal molecule in the regulation of denitrification and hence it is important to elucidate possible abiotic feedbacks of NO reactions in soil. The results will be discussed relative to the redox properties of the biochars tested.

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Sammendrag

Rapporten viser resultatene fra et forsøk med restaurering av dyrket myr som er tatt ut av drift, samt måling av utslipp klimagasser før og etter restaurering. Det ble målt store utslipp av CO2 flere år etter at driften opphørt. Metanutslippene varierte sterkt mens utslippene av lystgass var svært lave. Gjentetting av kanaler kan være en enkel og billig metode for tilbakeføre tidligere dyrket myr til naturlig tilstand, men førte ikke til reduksjon i CO2-utslipp eller økning i metanutslipp det første året. Flere års målinger er nødvendig for å få sikrere resultater av effekter av restaurering av myr i Norge.

Sammendrag

Myr kan fungere som et betydelig lager, eller kilde til, atmosfærisk karbon og spiller derfor en viktig rolle i den globale strålingsbalansen. Bioforsk har i samarbeid med UMB satt i gang utvikling av flere forskningsprosjekter for å studere klimagassutslipp fra myr, med spesiell vekt på virkning av jordbruksdrift.