| 1. |
- Holmstrup, Martin, et al.
(författare)
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Long-term and realistic global change manipulations had low impact on diversity of soil biota in temperate heathland
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- In a dry heathland ecosystem we manipulated temperature (warming), precipitation (drought) and atmospheric concentration of CO2 in a full-factorial experiment in order to investigate changes in below-ground biodiversity as a result of future climate change. We investigated the responses in community diversity of nematodes, enchytraeids, collembolans and oribatid mites at two and eight years of manipulations. We used a structural equation modelling (SEM) approach analyzing the three manipulations, soil moisture and temperature, and seven soil biological and chemical ariables. The analysis revealed a persistent and positive effect of elevated CO2 on litter C:N ratio. After two years of treatment, the fungi to bacteria ratio was increased by warming, and the diversities within oribatid mites, collembolans and nematode groups were all affected by elevated CO2 mediated through increased litter C:N ratio. After eight years of treatment, however, the CO2-increased litter C:N ratio did not influence the diversity in any of the four fauna groups. The number of significant correlations between treatments, food source quality, and soil biota diversities was reduced from six to three after two and eight years, respectively. These results suggest a remarkable resilience within the soil biota against global climate change treatments in the long term.
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| 2. |
- Mortensen, Louise Hindborg, et al.
(författare)
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Effect of ash application on the decomposer food web and N mineralization in a Norway spruce plantation
- 2020
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 715
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Tidskriftsartikel (refereegranskat)abstract
- In the face of global climate change there is an increasing demand for biofuel, which exerts pressure on production and thus management of biofuel plantations. The intensification of whole-tree harvest from biofuel plantations increases export of nutrients. Returning ash from biofuel combustion to the forest plantations can amend the soil nutrient status and thus facilitate sustainable forest management. However, ash affects the forest floor decomposer food web, potentially changing organic matter turnover, carbon sequestration and nitrogen availability. Our aim was to examine the response of decomposer organisms, food web structure and nitrogen mineralization function after ash application. In a coniferous forest plantation amended with 0, 3, 4.5 or 6 t ash ha− 1, we sampled in several depths of the forest floor for key organisms of the decomposer food web (fungal biomass, 0–12 cm; bacteria, protozoa, nematodes and enchytraeids, 0–3 cm and 3–6 cm; microarthropods and earthworms, 0–5 cm), 2, 14 and 26 months after ash application. We used structural equation modelling (SEM) to detangle the direct and indirect effects of ash application on organisms in the decomposer food web and on nitrogen availability. We found that ash increased the abundance of bacteria and protozoa, as well as the inorganic nitrogen pool at 0–3 cm depth, whereas the effect of ash was negligible at 3–6 cm depth. Earthworm abundance increased, whereas enchytraeid abundance decreased 2 years after ash application. The structural equation modelling showed that ash application stimulated the bacterial feeding pathway and increased nitrogen mineralization. Contrary, ash had a negative effect on fungal biomass at the first sampling, however, this effect subdued over time. Our results suggest that as the soil decomposer food web is resilient to ash application, this is a viable option for sustainable management of biofuel plantations.
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| 3. |
- Vestergård, Mette, et al.
(författare)
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Enhanced priming of old, not new soil carbon at elevated atmospheric CO2
- 2016
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 100, s. 140-148
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Tidskriftsartikel (refereegranskat)abstract
- Rising atmospheric CO2 concentrations accompanied by global warming and altered precipitation patterns calls for assessment of long-term effects of these global changes on carbon (C) dynamics in terrestrial ecosystems, as changes in net C exchange between soil and atmosphere will impact the atmospheric CO2 concentration profoundly. In many ecosystems, including the heath/grassland system studied here, increased plant production at elevated CO2 increase fresh C input from litter and root exudates to the soil and concurrently decrease soil N availability. Supply of labile C to the soil may accelerate the decomposition of soil organic C (SOC), a phenomenon termed 'the priming effect', and the priming effect is most pronounced at low soil N availability. Hence, we hypothesized that priming of SOC decomposition in response to labile C addition would increase in soil exposed to long-term elevated CO2 exposure. Further, we hypothesized that long-term warming would enhance SOC priming rates, whereas drought would decrease the priming response. We incubated soil from a long-term, full-factorial climate change field experiment, with the factors elevated atmospheric CO2 concentration, warming and prolonged summer drought with either labile C (sucrose) or water to assess the impact of labile C on SOC dynamics. We used sucrose with a 13C/12C signature that is distinct from that of the native SOC, which allowed us to assess the contribution of these two C sources to the CO2 evolved. Sucrose induced priming of SOC, and the priming response was higher in soil exposed to long-term elevated CO2 treatment. Drought tended to decrease the priming response, whereas long-term warming did not affect the level of priming significantly. We were also able to assess whether SOC-derived primed C in elevated CO2 soil was assimilated before or after the initiation of the CO2 treatment 8 years prior to sampling, because CO2 concentrations were raised by fumigating the experimental plots with pure CO2 that was 13C-depleted compared to ambient CO2. Surprisingly, we conclude that sucrose addition primed decomposition of relatively old SOC fractions, i.e. SOC assimilated more than 8 years before sampling.
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