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It is important to quantify carbon decomposition to assess the reforestation impact on the forest floor C stocks. Estimating the loss of C stock in a short-term perspective requires measuring changes in soil respiration. This is not trivial due to the contribution of both soil microbes and vegetation to the measured CO2 flux. However, C stable isotopes can be used to partition the respiration and potentially to assess how much of the recalcitrant C stock in the forest floor is lost. Here, we measured the soil respiration at two forest sites where different regeneration methods were applied, along with an intact forest soil for reference. In so doing, we used a closed dynamic chamber for measuring respiration and the 13C composition of the emitted CO2. The chamber measurements were then supplemented with the soil organic carbon analysis and its δ13C content. The mean δ13C-CO2 estimates for the source of the CO2 were -26.4, -27.9 and -29.5‰, for the forest, unploughed and ploughed, respectively. The 13C of the soil organic carbon did, not differ significantly between sites. The higher soil respiration rate at the forest, as compared to the unploughed site, could be attributed to the autotrophic respiration by the forest floor vegetation.

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Chamber measurements of trace gas fluxes between the land surface and the atmosphere have been conducted for almost a century. Different chamber techniques, including static and dynamic, have been used with varying degrees of success in estimating greenhouse gases (CO2, CH4, N2O) fluxes. However, all of these have certain disadvantages which have either prevented them from providing an adequate estimate of greenhouse gas exchange or restricted them to be used under limited conditions. Generally, chamber methods are relatively low in cost and simple to operate. In combination with the appropriate sample allocations, chamber methods are adaptable for a wide variety of studies from local to global spatial scales, and they are particularly well suited for in situ and laboratory-based studies. Consequently, chamber measurements will play an important role in the portfolio of the Pan-European long-term research infrastructure Integrated Carbon Observation System. The respective working group of the Integrated Carbon Observation System Ecosystem Monitoring Station Assembly has decided to ascertain standards and quality checks for automated and manual chamber systems instead of defining one or several standard systems provided by commercial manufacturers in order to define minimum requirements for chamber measurements. The defined requirements and recommendations related to chamber measurements are described here.

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Research infrastructures play a key role in launching a new generation of integrated long-term, geographically distributed observation programmes designed to monitor climate change, better understand its impacts on global ecosystems, and evaluate possible mitigation and adaptation strategies. The pan-European Integrated Carbon Observation System combines carbon and greenhouse gas (GHG; CO2, CH4, N2O, H2O) observations within the atmosphere, terrestrial ecosystems and oceans. High-precision measurements are obtained using standardised methodologies, are centrally processed and openly available in a traceable and verifiable fashion in combination with detailed metadata. The Integrated Carbon Observation System ecosystem station network aims to sample climate and land-cover variability across Europe. In addition to GHG flux measurements, a large set of complementary data (including management practices, vegetation and soil characteristics) is collected to support the interpretation, spatial upscaling and modelling of observed ecosystem carbon and GHG dynamics. The applied sampling design was developed and formulated in protocols by the scientific community, representing a trade-off between an ideal dataset and practical feasibility. The use of open-access, high-quality and multi-level data products by different user communities is crucial for the Integrated Carbon Observation System in order to achieve its scientific potential and societal value.

Sammendrag

Sammendrag: Denne rapporten gir en oppdatert oversikt over tiltakspotensiale for tiltak som jordbruket kan iverksette for å redusere klimagassutslipp. Det er tiltak innen dagens produksjonsystemer og struktur som er vektlagt. Det er sammenlignet med vurderinger gjort i rapporten «Landbruk og klimaendringer» fra 2016. Effekt av tiltak, gjennomføringsgrad og forutsetninger for gjennomføring til 2030 er prioritert.

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Extensive draining at tropical ombrotrophic peatlands in Southeast Asia has made these landscapes a global ‘hot spots’ for greenhouse gas emissions. Management practices and fires have changed substrate status, which affects microbial processes. Here, we present data on how change in management practices affect carbon (C) mineralization processes at these soils. We compared the C mineralization potentials of undrained swamp forest peat to those of abandoned peat (deforested, drained and burned peatlands in degraded condition) at various depths, with and without additional substrates (glucose, glutamate and nitrate), under oxic and anoxic conditions through ex situ experiments. Carbon mineralization (CO2 and CH4 production) rates were higher in the forest peat, with higher litter deposition and C availability. Production rates decreased with peat depth coinciding with decreasing availability of labile C. Consequently, the increase in production rates after labile substrate addition was relatively modest in forest peat as compared to the abandoned site and from the top layers as compared to deeper layers. Methanogenesis had little importance in total C loss. Adding labile C and nitrogen (N) enhanced heterotrophic CO2 production more than only addition of N. Surprisingly, oxygen availability did not limit CO2 production rates, but anoxic respiration also yielded substantial rates, especially at the forest peat. Flooding of these sites will therefore reduce, but not completely cease, peat C-loss. Reintroduced vegetation and fertilization in abandoned peatlands can enrich the peat with labile C and N compounds and thus lead to increased microbiological activity.

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The water management system of cultivated paddy rice soils is one of the most important factors affecting the respective magnitudes of CH4 and N2O emissions. We hypothesized an effect of past management on soil microbial communities and greenhouse gas (GHG) production potential. The ob- jectives of this study were to i) assess the influence of water management history on GHG production and microbial community structure, ii) relate GHG production to the microbial communities involved in CH4 and N2O production inhabiting the different soils. Moreover, the influence of different soil condi- tioning procedures on GHG production was determined. To reach these aims, we compared four soils with different water management history, using dried and sieved, pre-incubated and fresh soils. Soil conditioning procedures strongly affected GHG production: drying and sieving induced the highest production rates and the largest differences among soil types, probably through the release of labile substrates. Conversely, soil pre-incubation tended to homogenize and level out the differences among soils. The water management history strongly affected microbial community structure, which was itself tightly linked to CH4 and N2O production. N2O production was the highest in aerobic soil, which also exhibited the strongest evidence for active nitrifying communities (NirK). Drying and rewetting aerobic soil enhanced the production of nitrate, which was further reduced to N2O through denitrification. As expected, CH4 production was the lowest in aerobic soil, which showed a less abundant archaeal com- munity. This work supports the hypothesis that microbial communities in paddy soils progressively adapt to water management practices, thereby reinforcing potential differences in GHGs production.

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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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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