Abstract. The influence of global warming on soil organic matter (SOM) dynamics in terrestrial ecosystems remains unclear. In this study, we combined soil fractionation with isotope analyses to examine SOM dynamics after nine years of experimental warming in a North America tallgrass prairie. Soil samples from the control plots and the warmed plots were separated into four aggregate sizes (>2000 µm, 250-2000 µm, 53-250 µm, and <53 µm), and three density fractions (free light fraction -LF, intra-aggregate particulate organic matter -iPOM, and mineral-associated organic matter -mSOM). All fractions were analyzed for their carbon (C) and nitrogen (N) content, and δ 13 C and δ 15 N values. Warming did not significantly effect soil aggregate distribution and stability but increased C 4 -derived C input into all fractions with the greatest in LF. Warming also stimulated decay rates of C in whole soil and all aggregate sizes. C in LF turned over faster than that in iPOM in the warmed soils. The δ 15 N values of soil fractions were more enriched in the warmed soils than those in the control, indicating that warming accelerated loss of soil N. The δ 15 N values changed from low to high, while C:N ratios changed from high to low in the order LF, iPOM, and mSOM due to increased degree of decomposition and mineral association. Overall, warming increased the input of C 4 -derived C by 11.6 %, which was offset by the accelerated loss of soil C. Our results suggest that global warming simultaneously stimulates C input via shift in species composition and decomposition of SOM, resulting in negligible net change in soil C.

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Articles you may be interested inLarge magnetocaloric effect with a wide working temperature span in the R2CoGa3 (R=Gd, Dy, and Ho) compounds Large magnetocaloric effects over a wide temperature range in MnCo1−xZnxGe Magnetocaloric effect of Ho-, Dy-, and Er-based bulk metallic glasses in helium and hydrogen liquefaction temperature range Appl.The compound Ho 2 In exhibits two successive magnetic phase transitions: a spin-reorientation transition at T SR = 32 K and a magnetic-ordering transition at T C = 85 K. The maximum reversible −⌬S M values are 6.3 and 11.2 J/kg K at T SR and T C , respectively, for a field change of 5 T. These two −⌬S M peaks with the same sign are partly overlapping, which results in a wide temperature interval with appreciable magnetocaloric effect. The results on Ho 2 In indicate that materials with successive SR and magnetic-ordering transitions may constitute an important new class of magnetic refrigerants since they work in a wider temperature range than the conventional refrigerant materials.

In Fe0.8Mn1.5As compound, an external magnetic field induces a metamagnetic transition from an antiferromagnetic phase to a ferrimagnetic phase above Ts=285K, leading to large magnetocaloric effects around room temperature. Instead of showing inverse magnetocaloric effects, the sign of the entropy change ΔSM in the compound is unexpectedly negative, revealing a different mechanism. The maximum value of ΔSM is 6.2J∕kgK at 287.5K for a magnetic field change of 5T. The study on systems with antiferromagnetism-related metamagnetic transitions may open an important field in searching good materials for room-temperature magnetic refrigeration.

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Articles you may be interested inPhase transformations of nano-sized cubic boron nitride to white graphene and white graphite Appl. Phys. Lett. 104, 093104 (2014); 10.1063/1.4867256 Microstructures and the corresponding magnetic properties of half-doped Nd 0.5 Sr 0.5 MnO 3 films J. Appl. Phys.

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