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Abstract

Background: Global warming is going to affect both agricultural production and carbon storage in soil worldwide. Given the complexity of the soil-plant-atmosphere continuum, in situ experiments of climate warming are necessary to predict responses of plants and emissions of greenhouse gases (GHG) from soils. Arrays of infrared (IR) heaters have been successfully applied in temperate and tropical agro-ecosystems to produce uniform and large increases in canopy surface temperature across research plots. Because this method had not yet been tested in the Arctic where consequences of global warming on GHG emission are expected to be largest, the objective of this work was to test hexagonal arrays of IR heaters to simulate a homogenous 3 °C warming of the surface, i.e. canopy and visible bare soil, of five 10.5-m2 plots in an Arctic meadow of northern Norway. Results: Our results show that the IR warming setup was able to simulate quite accurately the target + 3 °C, thereby enabling us to simulate the extension of the growing season. Meadow yield increased under warming but only through the lengthening of the growing season. Our research also suggests that, when investigating agricultural systems on the Arctic, it is important to start the warming after the vegetation is established,. Indeed, differential emergence of meadow plants impaired the homogeneity of the warming with patches of bare soil being up to 9.5 °C warmer than patches of vegetation. This created a pattern of soil crusting, which further induced spatial heterogeneity of the vegetation. However, in the Arctic these conditions are rather rare as the soil exposed by snow melt is often covered by a layer of senescent vegetation which shelters the soil from direct radiation. Conclusions: Consistent continuous warming can be obtained on average with IR systems in an Arctic meadow, but homogenous spatial distribution requires that the warming must start after canopy closure.

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Abstract

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.

Abstract

Precise methods for the detection of geologically stored CO2within and above soil surfaces are an impor-tant component of the development of carbon capture and storage (CCS) under terrestrial environments.Although CO2leaks are not expected in well-chosen and operated storage sites, monitoring is required bylegislation and any leakage needs to be quantified under the EU Emissions Trading Directive. The objec-tive of the present research was to test if13C stable isotope motoring of soil and canopy atmosphere CO2increases our detection sensitivity for CCS-CO2as compared with concentration monitoring only. A CO2injection experiment was designed to create a horizontal CO2gradient across 6 m × 3 m plots, which weresown with oats in 2011 and 2012. Injected CO2was methane derived and had an isotopic signature of−46.2‰. The CO2concentrations were measured within the soil profile with passive samplers and at sev-eral heights within the crop canopies. The CO2fluxes and their13C signatures were also measured acrossthe experimental plots. In situ monitoring and gas samples measurements were conducted with a cavityring down spectrometer (CRDS). The plots displayed hot spots of injected-CO2leakage clearly detectableby either concentration or isotopic signature measurements. In addition, the13C signature measurementsallow us to detect injected CO2in plot regions where its presence could not be unequivocally ascertainedbased on concentration measurement alone.