| 11. |
- Hyvonen, R., et al.
(författare)
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The likely impact of elevated [CO2], nitrogen deposition, increased temperature and management on carbon sequestration in temperate and boreal forest ecosystems: a literature review
- 2007
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Ingår i: New Phytologist. - Cambridge : Wiley. - 0028-646X .- 1469-8137. ; 173:3, s. 463-480
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Forskningsöversikt (refereegranskat)abstract
- Temperate and boreal forest ecosystems contain a large part of the carbon stored on land, in the form of both biomass and soil organic matter. Increasing atmospheric [CO2], increasing temperature, elevated nitrogen deposition and intensified management will change this C store. Well documented single-factor responses of net primary production are: higher photosynthetic rate (the main [CO2] response); increasing length of growing season (the main temperature response); and higher leaf-area index (the main N deposition and partly [CO2] response). Soil organic matter will increase with increasing litter input, although priming may decrease the soil C stock initially, but litter quality effects should be minimal (response to [CO2], N deposition, and temperature); will decrease because of increasing temperature; and will increase because of retardation of decomposition with N deposition, although the rate of decomposition of high-quality litter can be increased and that of low-quality litter decreased. Single-factor responses can be misleading because of interactions between factors, in particular those between N and other factors, and indirect effects such as increased N availability from temperature-induced decomposition. In the long term the strength of feedbacks, for example the increasing demand for N from increased growth, will dominate over short-term responses to single factors. However, management has considerable potential for controlling the C store.
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| 12. |
- Högberg, Peter, et al.
(författare)
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High temporal resolution tracing of photosynthate carbon from the tree canopy to forest soil microorganisms
- 2008
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Ingår i: New Phytologist. - : New Phytologist Trust. - 0028-646X .- 1469-8137. ; 177:1, s. 220-228
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Tidskriftsartikel (refereegranskat)abstract
- • Half of the biological activity in forest soils is supported by recent tree photosynthate, but no study has traced in detail this flux of carbon from the canopy to soil microorganisms in the field.• Using 13CO2, we pulse-labelled over 1.5 h a 50-m2 patch of 4-m-tall boreal Pinus sylvestris forest in a 200-m3 chamber.• Tracer levels peaked after 24 h in soluble carbohydrates in the phloem at a height of 0.3 m, after 2–4 d in soil respiratory efflux, after 4–7 d in ectomycorrhizal roots, and after 2–4 d in soil microbial cytoplasm. Carbon in the active pool in needles, in soluble carbohydrates in phloem and in soil respiratory efflux had half-lives of 22, 17 and 35 h, respectively. Carbon in soil microbial cytoplasm had a half-life of 280 h, while the carbon in ectomycorrhizal root tips turned over much more slowly. Simultaneous labelling of the soil with showed that the ectomycorrhizal roots, which were the strongest sinks for photosynthate, were also the most active sinks for soil nitrogen.• These observations highlight the close temporal coupling between tree canopy photosynthesis and a significant fraction of soil activity in forests.
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| 13. |
- Kostiainen, K., et al.
(författare)
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Stem wood properties of mature Norway spruce after 3 years of continuous exposure to elevated [CO2] and temperature
- 2009
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 15:2, s. 368-379
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Tidskriftsartikel (refereegranskat)abstract
- The objective of the study was to investigate the interactive effects of elevated atmospheric carbon dioxide concentration, [CO2], and temperature on the wood properties of mature field-grown Norway spruce (Picea abies (L.) Karst.) trees. Material for the study was obtained from an experiment in Flakaliden, northern Sweden, where trees were grown for 3 years in whole-tree chambers at ambient (365 ÎŒmol mol-1) or elevated [CO2] (700 ÎŒmol mol-1) and ambient or elevated air temperature (ambient +5.6°C in winter and ambient +2.8°C in summer). Elevated temperature affected both wood chemical composition and structure, but had no effect on stem radial growth. Elevated temperature decreased the concentrations of acetone-soluble extractives and soluble sugars, while mean and earlywood (EW) cell wall thickness and wood density were increased. Elevated [CO2] had no effect on stem wood chemistry or radial growth. In wood structure, elevated [CO2] decreased EW cell wall thickness and increased tracheid radial diameter in latewood (LW). Some significant interactions between elevated [CO2] and temperature were found in the anatomical and physical properties of stem wood (e.g. microfibril angle, and LW cell wall thickness and density). Our results show that the wood material properties of mature Norway spruce were altered under exposure to elevated [CO2] and temperature, although stem radial growth was not affected by the treatments. © 2008 The Authors Journal compilation © 2008 Blackwell Publishing.
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| 16. |
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| 18. |
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| 19. |
- Rubin, D., et al.
(författare)
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Looking Beyond Lambda with the Union Supernova Compilation
- 2009
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 695, s. 391-403
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Tidskriftsartikel (refereegranskat)abstract
- The recent robust and homogeneous analysis of the world's supernova distance-redshift data, together with cosmic microwave background and baryon acoustic oscillation data—provides a powerful tool for constraining cosmological models. Here we examine particular classes of scalar field, modified gravity, and phenomenological models to assess whether they are consistent with observations even when their behavior deviates from the cosmological constant Λ. Some models have tension with the data, while others survive only by approaching the cosmological constant, and a couple are statistically favored over Λ cold dark matter. Dark energy described by two equation-of-state parameters has considerable phase space to avoid Λ and next-generation data will be required to constrain such physics, with the level of complementarity between probes varying with cosmology.
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| 20. |
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