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- Bergkvist, Bo, et al.
(författare)
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Pools and fluxes of carbon in three Norway spruce ecosystems along a climatic gradient in Sweden
- 2008
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Ingår i: Biogeochemistry. - : Springer Science and Business Media LLC. - 0168-2563 .- 1573-515X. ; 89:1, s. 7-25
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an integrated analysis of organic carbon (C) pools in soils and vegetation, within-ecosystem fluxes and net ecosystem exchange (NEE) in three 40-year old Norway spruce stands along a north-south climatic gradient in Sweden, measured 2001-2004. A process-orientated ecosystem model (CoupModel), previously parameterised on a regional dataset, was used for the analysis. Pools of soil organic carbon (SOC) and tree growth rates were highest at the southernmost site (1.6 and 2.0-fold, respectively). Tree litter production (litterfall and root litter) was also highest in the south, with about half coming from fine roots (< 1 mm) at all sites. However, when the litter input from the forest floor vegetation was included, the difference in total litter input rate between the sites almost disappeared (190-233 g C m(-2) year(-1)). We propose that a higher N deposition and N availability in the south result in a slower turnover of soil organic matter than in the north. This effect seems to overshadow the effect of temperature. At the southern site, 19% of the total litter input to the O horizon was leached to the mineral soil as dissolved organic carbon, while at the two northern sites the corresponding figure was approx. 9%. The CoupModel accurately described general C cycling behaviour in these ecosystems, reproducing the differences between north and south. The simulated changes in SOC pools during the measurement period were small, ranging from -8 g C m(-2) year(-1) in the north to +9 g C m(-2) year(-1) in the south. In contrast, NEE and tree growth measurements at the northernmost site suggest that the soil lost about 90 g C m(-2) year(-1).
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| 2. |
- Holmberg, L, et al.
(författare)
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A search for recall bias in a case-control study of diet and breast cancer
- 1996
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Ingår i: INTERNATIONAL JOURNAL OF EPIDEMIOLOGY. - : OXFORD UNIV PRESS UNITED KINGDOM. - 0300-5771. ; 25:2, s. 235-244
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Tidskriftsartikel (refereegranskat)abstract
- Background. In retrospective studies of dietary habits and breast cancer risk, recall bias is a concern since diet has been publicized as a cause of breast cancer. Methods, In a case-control study of diet and breast cancer risk nested within a cohort of w
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| 5. |
- Ringselle, Björn, et al.
(författare)
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Rhizome fragmentation by vertical disks reduces Elymus repens growth and benefits italian ryegrass-white clover crops
- 2018
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Ingår i: Frontiers in Plant Science. - : Frontiers Media S.A.. - 1664-462X. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Tillage controls perennial weeds, such as Elymus repens, partly because it fragments their underground storage organs. However, tillage is difficult to combine with a growing crop, which limits its application. The aim of this study was to evaluate how soil vertical cutting with minimum soil disturbance and mowing affect the growth and competitive ability of E. repens in a grass–clover crop. A tractor-drawn prototype with vertical disks was used to fragment E. repens rhizomes with minimal soil and crop disturbance. In experiments performed in 2014 and 2015 at a field site close to Uppsala, Sweden, the rhizomes were fragmented before crop sowing (ERF), during crop growth (LRF), or both (ERF+LRF). Fragmentation was combined with repeated mowing (yes/no) and four companion crop treatments (none, Italian ryegrass, white clover, and grass/clover mixture). The results showed that in the grass–clover crop, rhizome fragmentation reduced E. repens rhizome biomass production and increased Italian ryegrass shoot biomass. ERF and LRF both reduced E. repens rhizome biomass by about 38% compared with the control, while ERF+LRF reduced it by 63%. Italian ryegrass shoot biomass was increased by 78% by ERF, 170% by LRF and 200% by ERF+LRF. Repeated mowing throughout the experiment reduced E. repens rhizome biomass by about 75%. Combining repeated mowing with rhizome fragmentation did not significantly increase the control effect compared to mowing alone. We concluded that rhizome fragmentation using vertical disks can be used both before sowing and during crop growth to enhance the controlling effect of grass–clover crops on E. repens.
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