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- Camino-Serrano, Marta, et al.
(författare)
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ORCHIDEE-SOM : Modeling soil organic carbon (SOC) and dissolved organic carbon (DOC) dynamics along vertical soil profiles in Europe
- 2018
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Ingår i: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 11:3, s. 937-957
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Tidskriftsartikel (refereegranskat)abstract
- Current Land Surface Models (LSMs) typically represent soils in a very simplistic way, assuming soil organic carbon (SOC) as a bulk, thus impeding a correct representation of deep soil carbon dynamics. Moreover, LSMs generally neglect the production and export of dissolved organic carbon (DOC) from soils to rivers, leading to overestimations of the potential carbon sequestration on land. These common oversimplified processing of SOC in LSMs is partly responsible for the large uncertainty in the predictions of the soil carbon response to climate change. In this study, we present a new soil carbon module called ORCHIDEE-SOM, embedded within the land surface model ORCHIDEE, which is able to reproduce the DOC and SOC dynamics in a vertically discretized soil to two meters. The model includes processes of biological production and consumption of SOC and DOC, DOC adsorption on- and desorption from soil minerals, diffusion of SOC and DOC and DOC transport with water through and out of the soils to rivers. We evaluated ORCHIDEE-SOM against observations of DOC concentrations and SOC stocks from four European sites with different vegetation covers: a coniferous forest, a deciduous forest, a grassland and a cropland. The model was able to reproduce the SOC stocks along their vertical profiles at the four sites and the DOC concentrations within the range of measurements, with the exception of the DOC concentrations in the upper soil horizon at the coniferous forest. However, the model was not able to fully capture the temporal dynamics of DOC concentrations. Further model improvements should focus on a plant- and depth- dependent parameterization of the new input model parameters, such as the decomposition times of DOC and the microbial carbon use efficiency. We suggest that this new soil module, when parameterized for global simulations, will improve the representation of the global carbon cycle in LSMs, thus helping to constrain the predictions of the future SOC response to global warming.
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| 3. |
- Sigurdsson, Bjarni D., et al.
(författare)
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Geothermal ecosystems as natural climate change experiments : The ForHot research site in Iceland as a case study
- 2016
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Ingår i: Icelandic Agricultural Sciences. - 1670-567X. ; 29:1, s. 53-71
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Tidskriftsartikel (refereegranskat)abstract
- This article describes how natural geothermal soil temperature gradients in Iceland have been used to study terrestrial ecosystem responses to soil warming. The experimental approach was evaluated at three study sites in southern Iceland one grassland site that has been warm for at least 50 years (GO), and another comparable grassland site (GN) and a Sitka spruce plantation (FN) site that have both been warmed since an earthquake took place in 2008. Within each site type, five ca. 50 m long transects, with six permanent study plots each, were established across the soil warming gradients, spanning from unwarmed control conditions to gradually warmer soils. It was attempted to select the plots so the annual warming levels would be ca. +1, +3, +5, +10 and +20 °C within each transect. Results of continuous measurements of soil temperature (Ts) from 2013-2015 revealed that the soil warming was relatively constant and followed the seasonal Ts cycle of the unwarmed control plots. Volumetric water content in the top 5 cm of soil was repeatedly surveyed during 2013-2016. The grassland soils were wetter than the FN soils, but they had sometimes some significant warming-induced drying in the surface layer of the warmest plots, in contrast to FN. Soil chemistry did not show any indications that geothermal water had reached the root zone, but soil pH did increase somewhat with warming, which was probably linked to vegetation changes. As expected, the potential decomposition rate of organic matter increased significantly with warming. It was concluded that the natural geothermal gradients at the ForHot sites in Iceland offered realistic conditions for studying terrestrial ecosystem responses to warming with minimal artefacts.
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| 4. |
- Verlinden, Melanie S., et al.
(författare)
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Favorable effect of mycorrhizae on biomass production efficiency exceeds their carbon cost in a fertilization experiment
- 2018
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 99:11, s. 2525-2534
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Tidskriftsartikel (refereegranskat)abstract
- Biomass production efficiency (BPE), the ratio of biomass production to photosynthesis, varies greatly among ecosystems and typically increases with increasing nutrient availability. Reduced carbon partitioning to mycorrhizal fungi (i.e., per unit photosynthesis) is the hypothesized underlying mechanism, as mycorrhizal abundance and plant dependence on these symbionts typically decrease with increasing nutrient availability. In a mesocosm experiment with Zea mays, we investigated the effect of nitrogen (N) and phosphorus (P) addition and of mycorrhizal inoculation on BPE. Photosynthesis and respiration were measured at mesocosm scale and at leaf scale. The growth of arbuscular mycorrhizal fungi (AMF) was assessed with ingrowth bags while also making use of the difference in δ13C between C4 plants and C3 soil. Mesocosms without AMF, that is, with pasteurized soil, were used to further explore the role of AMF. Plant growth, photosynthesis, and BPE were positively affected by P, but not by N addition. AMF biomass also was slightly higher under P addition, but carbon partitioning to AMF was significantly lower than without P addition. Interestingly, in the absence of AMF, plants that did not receive P died prematurely. Our study confirmed the hypothesis that BPE increases with increasing nutrient availability, and that carbon partitioning to AMF plays a key role in this nutrient effect. The comparison of inoculated vs. pasteurized mesocosms further suggested a lower carbon cost of nutrient uptake via AMF than via other mechanisms under nutrient rich conditions.
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