| 1. |
- Luyssaert, S., et al.
(författare)
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CO2 balance of boreal, temperate, and tropical forests derived from a global database
- 2007
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 13:12, s. 2509-2537
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Forskningsöversikt (refereegranskat)abstract
- Terrestrial ecosystems sequester 2.1 Pg of atmospheric carbon annually. A large amount of the terrestrial sink is realized by forests. However, considerable uncertainties remain regarding the fate of this carbon over both short and long timescales. Relevant data to address these uncertainties are being collected at many sites around the world, but syntheses of these data are still sparse. To facilitate future synthesis activities, we have assembled a comprehensive global database for forest ecosystems, which includes carbon budget variables (fluxes and stocks), ecosystem traits (e.g. leaf area index, age), as well as ancillary site information such as management regime, climate, and soil characteristics. This publicly available database can be used to quantify global, regional or biome-specific carbon budgets; to re-examine established relationships; to test emerging hypotheses about ecosystem functioning [e.g. a constant net ecosystem production (NEP) to gross primary production (GPP) ratio]; and as benchmarks for model evaluations. In this paper, we present the first analysis of this database. We discuss the climatic influences on GPP, net primary production (NPP) and NEP and present the CO2 balances for boreal, temperate, and tropical forest biomes based on micrometeorological, ecophysiological, and biometric flux and inventory estimates. Globally, GPP of forests benefited from higher temperatures and precipitation whereas NPP saturated above either a threshold of 1500 mm precipitation or a mean annual temperature of 10 degrees C. The global pattern in NEP was insensitive to climate and is hypothesized to be mainly determined by nonclimatic conditions such as successional stage, management, site history, and site disturbance. In all biomes, closing the CO2 balance required the introduction of substantial biome-specific closure terms. Nonclosure was taken as an indication that respiratory processes, advection, and non-CO2 carbon fluxes are not presently being adequately accounted for.
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| 2. |
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| 3. |
- 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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| 4. |
- Grelle, A., et al.
(författare)
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Large carbon-sink potential by Kyoto forests in Sweden - A case study on willow plantations
- 2007
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Ingår i: Tellus Series B-Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 59:5, s. 910-918
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Tidskriftsartikel (refereegranskat)abstract
- Fluxes of CO were measured in a 75-ha short-rotation willow plantation at Enkoping, central Sweden. The plantation was irrigated with wastewater for fertilization and water-filtering purposes. The harvested biomass was used locally for combined heat and power production. The plantation was a sink of ca. 8 tonnes C ha(-1) during 2003, of which ca. 50% was estimated to be attributed to fertilization. Biomass increment by shoot growth was 5 tonnes C ha-1 during the same year. Belowground carbon allocation was estimated to 3 tonnes C ha(-1) yr(-1) by a model that relates carbon allocation to shoot growth. Thus, the ecosystem carbon balance was closed by these estimations. The carbon uptake by the willow plantation was 5.5 times as high compared to a normally managed spruce forest, but only half as high as from an experimental, well-roanaged willow plantation in the same region. This illustrates the vast potential of short-rotation willow plantations for CO2 uptake from the atmosphere.
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| 5. |
- Lagergren, Fredrik, et al.
(författare)
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Net primary production and light use efficiency in a mixed coniferous forest in Sweden
- 2005
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Ingår i: Plant, Cell and Environment. - : Wiley. - 0140-7791 .- 1365-3040. ; 28:3, s. 412-423
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Tidskriftsartikel (refereegranskat)abstract
- Simple light use efficiency (epsilon) models of net primary production (NPP) have recently been given great attention (NPP = epsilon x absorbed photosynthetically active radiation). The underlying relationships have, however, not been much studied on a time step less than a month. In this study daily NPP was estimated as the sum of net ecosystem exchange (NEE) and heterotrophic respiration (R-h) of a mixed pine and spruce forest in Sweden. NEE was measured by eddy correlation technique and R-h was estimated from measurements of forest floor respiration (R-f) and the root share of R-f. The total yearly NPP was on average 810 g C m(-2) year(-1) for 3 years and yearly epsilon was between 0.58 and 0.71 g C MJ(-1), which is high in comparison with other studies. There was a seasonal trend in epsilon with a relatively constant level of approximately 0.90 g C MJ(-1) from April to September Daily NPP did not increase for daily intercepted radiation above 6 MJ m(-2) d(-1), indicating that between-years variation in NPP is not directly dependent on total Q(i). The light was most efficiently used at an average daytime temperature of around 15 degreesC. At daytime vapour pressure deficit above 1400 Pa epsilon was reduced by approximately 50%.
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| 6. |
- Lindroth, Anders, et al.
(författare)
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Gudrun - en kolbomb
- 2005
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Ingår i: Miljöforskning : Formas tidning för ett uthålligt samhälle. - 1650-4925. ; 5-6, s. 22-24
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 7. |
- Lindroth, Anders, et al.
(författare)
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Measurement of net ecosystem exchange, productivity and respiration in three spruce forests in Sweden shows unexpectedly large soil carbon losses
- 2008
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Ingår i: Biogeochemistry. - : Springer Science and Business Media LLC. - 0168-2563 .- 1573-515X. ; 89:1, s. 43-60
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Tidskriftsartikel (refereegranskat)abstract
- Measurement of net ecosystem exchange was made using the eddy covariance method above three forests along a north-south climatic gradient in Sweden: Flakaliden in the north, Knottasen in central and Asa in south Sweden. Data were obtained for 2 years at Flakaliden and Knottasen and for one year at Asa. The net fluxes (N-ep) were separated into their main components, total ecosystem respiration (R-t) and gross primary productivity (P-g). The maximum half-hourly net uptake during the heart of the growing season was highest in the southernmost site with -0.787 mg CO2 m(-2) s(-1) followed by Knottasen with -0.631 mg CO2 m(-2) s(-1) and Flakaliden with -0.429 mg CO2 m(-2) s(-1). The maximum respiration rates during the summer were highest in Knottasen with 0.245 mg CO2 m(-2) s(-1) while it was similar at the two other sites with 0.183 mg CO2 m(-2) s(-1). The annual N-ep ranged between uptake of -304 g C m(-2) year(-1) (Asa) and emission of 84 g C m(-2) year(-1) (Knottasen). The annual R-t and P-g ranged between 793 to 1253 g C m(-2)year(-1) and -875 to -1317 g C m(-2) year(-1), respectively. Biomass increment measurements in the footprint area of the towers in combination with the measured net ecosystem productivity were used to estimate the changes in soil carbon and it was found that the soils were losing on average 96-125 g C m(-2)year(-1). The most plausible explanation for these losses was that the studied years were much warmer than normal causing larger respiratory losses. The comparison of net primary productivity and P-g showed that ca 60% of P-g was utilized for autotrophic respiration.
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| 8. |
- Magnani, F, et al.
(författare)
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The human footprint in the carbon cycle of temperate and boreal forests
- 2007
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Ingår i: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885. ; 447, s. 848-850
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Tidskriftsartikel (refereegranskat)abstract
- Temperate and boreal forests in the Northern Hemisphere cover an area of about 2 times 107 square kilometres and act as a substantial carbon sink (0.6–0.7 petagrams of carbon per year)1. Although forest expansion following agricultural abandonment is certainly responsible for an important fraction of this carbon sink activity, the additional effects on the carbon balance of established forests of increased atmospheric carbon dioxide, increasing temperatures, changes in management practices and nitrogen deposition are difficult to disentangle, despite an extensive network of measurement stations2, 3. The relevance of this measurement effort has also been questioned4, because spot measurements fail to take into account the role of disturbances, either natural (fire, pests, windstorms) or anthropogenic (forest harvesting). Here we show that the temporal dynamics following stand-replacing disturbances do indeed account for a very large fraction of the overall variability in forest carbon sequestration. After the confounding effects of disturbance have been factored out, however, forest net carbon sequestration is found to be overwhelmingly driven by nitrogen deposition, largely the result of anthropogenic activities5. The effect is always positive over the range of nitrogen deposition covered by currently available data sets, casting doubts on the risk of widespread ecosystem nitrogen saturation6 under natural conditions. The results demonstrate that mankind is ultimately controlling the carbon balance of temperate and boreal forests, either directly (through forest management) or indirectly (through nitrogen deposition).
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| 9. |
- Sagerfors, J., et al.
(författare)
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Annual CO2 exchange between a nutrient-poor, minerotrophic, boreal mire and the atmosphere
- 2008
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Ingår i: Journal of Geophysical Research-Biogeosciences. - 0148-0227 .- 2169-8961. ; 113:G1
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Tidskriftsartikel (refereegranskat)abstract
- [1] Mires are key landscape elements at high latitudes and have certainly accumulated carbon during the Holocene, but their current carbon balance at the present time is very unclear. The major carbon flux is the land-atmosphere CO2 exchange and full-year data are still limited. Here we present data from 3 a (2001-2003) of continuous Eddy Covariance measurements at Degero Stormyr (64 degrees 11'N, 19 degrees 33'E) an oligotrophic, minerotrophic mire in Sweden. The climate at the site is defined as cold temperate humid, with 30-a annual precipitation and temperature means of 523 mm and +1.2 degrees C, respectively, while the mean temperatures in July and January are +14.7 degrees C and -12.4 degrees C, respectively. The length of the vegetation period was 153 +/- 15 d during the measured years. The minerotrophic mire represented a net sink for the vertical exchange of atmospheric CO2-C during the 3 a, with an average net uptake of 55 +/- 7 g ( mean +/- SD) CO2-C m(-2) a(-1). The growing season average uptake was 92 +/- 10 g CO2-C m(-2), of which approximately 40% ( 37 +/- 5 g CO2-C m(-2)) was lost during the nongrowing season. The daily average uptake over the growing season was 0.65 +/- 0.57, 0.73 +/- 0.61, and 0.68 +/- 0.62 g CO2-C m(-2) d(-1) in 2001, 2002, and 2003, respectively. The daily average net uptake for the month with highest uptake was 1.10 +/- 0.33, 1.11 +/- 0.63, and 1.22 +/- 0.55 g CO2-C m(-2) d(-1) in July 2001, July 2002, and June 2003, respectively. The daily average efflux during the nongrowing season was 0.14 +/- 0.28, 0.15 +/- 0.20, and 0.20 +/- 0.19 g CO2-C m(-2) d(-1) in the years 2001, 2002, and 2003, respectively.
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