| 1. |
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| 2. |
- Franz, D, et al.
(author)
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Towards long-term standardised carbon and greenhouse gas observations for monitoring Europe´s terrestrial ecosystems: a review
- 2018
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In: International Agrophysics. - : Walter de Gruyter GmbH. - 0236-8722 .- 2300-8725. ; 32, s. 439-455
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Journal article (peer-reviewed)abstract
- Research infrastructures play a key role in launching a new generation of integrated long-term, geographically distributed observation programmes designed to monitor climate change, better understand its impacts on global ecosystems, and evaluate possible mitigation and adaptation strategies. The pan-European Integrated Carbon Observation System combines carbon and greenhouse gas (GHG; CO2, CH4, N2O, H2O) observations within the atmosphere, terrestrial ecosystems and oceans. High-precision measurements are obtained using standardised methodologies, are centrally processed and openly available in a traceable and verifiable fashion in combination with detailed metadata. The Integrated Carbon Observation System ecosystem station network aims to sample climate and land-cover variability across Europe. In addition to GHG flux measurements, a large set of complementary data (including management practices, vegetation and soil characteristics) is collected to support the interpretation, spatial upscaling and modelling of observed ecosystem carbon and GHG dynamics. The applied sampling design was developed and formulated in protocols by the scientific community, representing a trade-off between an ideal dataset and practical feasibility. The use of open-access, high-quality and multi-level data products by different user communities is crucial for the Integrated Carbon Observation System in order to achieve its scientific potential and societal value.
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| 3. |
- Luyssaert, S., et al.
(author)
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CO2 balance of boreal, temperate, and tropical forests derived from a global database
- 2007
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In: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 13:12, s. 2509-2537
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Research review (peer-reviewed)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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| 4. |
- Grelle, A., et al.
(author)
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Evaporation components of a boreal forest : variations during the growing season
- 1997
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In: Journal of Hydrology. - 0022-1694 .- 1879-2707. ; 197:1-4, s. 70-87
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Journal article (peer-reviewed)abstract
- To improve the understanding of interactions between the boreal forest and the climate system as a key issue for global climate change, the water budget of a mixed pine and spruce forest in central Sweden was estimated by measurements of the water flux components and the total evaporation flux during the period 16 May-31 October 1995. Total evaporation was measured using eddy correlation and the components were obtained using measurements of precipitation, throughfall, tree transpiration, and forest floor evaporation. On a daily basis, tree transpiration was the dominant evaporation component during the vegetation period. However, it could be efficiently blocked by a wet canopy associated with large interception evaporation. The accumulated total evaporation was 399 mm, transpiration was 243 mm, forest floor evaporation was 56 mm and interception evaporation was 74 mm. The accumulated sum of interception, transpiration, and floor evaporation was 51 mm larger than the actual measured total evaporation. This difference was mainly attributed to the fact that transpiration was measured in a rather dense 50-year-old stand while total evaporation represented the average conditions of older, roughly 100-year-old stands. To compare eddy-correlation measurements with small-scale measurements of evaporation components, a source area analysis was made to select the flux data that give the best representation of the investigated stand. Especially under stable atmospheric conditions the requirements for surface homogeneity were very high and extreme care had to be taken to be aware of the flux source areas. Canopy water storage was determined by two methods: by the water balance of the canopy, which gave a result of 3.3 mm; and by the so-called minimum method based on plots of throughfall versus precipitation, which gave a much lower value of 1.5 mm. Seasonal interception evaporation constituted 30% of the precipitation.
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| 5. |
- Halldin, S, et al.
(author)
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Continuous long-term measurements of soil-plant-atmosphere variables at an agricultural site
- 1999
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In: AGRICULTURAL AND FOREST METEOROLOGY. - : ELSEVIER SCIENCE BV. - 0168-1923. ; 98-9, s. 75-102
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Journal article (peer-reviewed)abstract
- It is a major challenge in modem science to decrease the uncertainty in predictions of global climate change. One of the largest uncertainties in present-day global climate models resides with the understanding of processes in the soil-vegetation-atmosphe
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| 6. |
- Lundin, Lars-Christer, et al.
(author)
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Continuous long-term measurements of soil-plant-atmosphere variables at a forest site
- 1999
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In: Agricultural and Forest Meteorology. - 0168-1923 .- 1873-2240. ; 98-99, s. 53-73
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Journal article (peer-reviewed)abstract
- It is a major challenge in modem science to decrease the uncertainty in predictions of global climate change. One of the largest uncertainties in present-day global climate models resides with the understanding of processes in the soil-vegetation-atmosphere-transfer (SVAT) system. Continuous, long-term data are needed in order to correctly quantify balances of water, energy and CO2 in this system and to correctly model it. It is the objective of this paper to demonstrate how a combined system of existing sensor, computer, and network technologies could be set up to provide continuous and reliable long-term SVAT-process data from a forested site under almost all environmental conditions. The Central Tower Site (CTS) system was set up in 1993-1994 in a 25 m high boreal forest growing on a highly heterogeneous till soil with a high content of stones and blocks. It has successfully monitored relevant states and fluxes in the system, such as atmospheric fluxes of momentum, heat, water vapour and CO2, atmospheric profiles of temperature, water vapour, CO2, short-and long-wave radiation, heat storage in soil and trees, sap-dow and a variety of ecophysiological properties, soil-water contents and tensions, and groundwater levels, rainfall and throughfall. System uptime has been more than 90% for most of its components during the first 5 years of operation. Results from the first 5 years of operation include e.g., budgets for energy, water and CO2, information on important but rarely occurring events such as evaporation from snow-covered canopies, and reactions of the forest to extreme drought. The carbon budget shows that the forest may be a sink of carbon although it is still growing. The completeness of the data has made it possible to test the internal consistency of SVAT models. The pioneering set-up at the CTS has been adopted by a large number of SVAT-monitoring sites around the world. Questions concerning tower maintenance, long-term calibration plans, maintenance of sensors and data-collection system, and continuous development of the computer network to keep it up to date are, however, only partly of interest as a research project in itself. It is thus difficult to get it funded from usual research-funding agencies. The full value of data generated by the CTS system can best be appreciated after a decade or more of continuous operation. Main uses of the data would be to evaluate how SVAT models handle the natural variability of climate conditions, quantification of water. carbon and energy budgets during various weather conditions, rind development of new parameterisation schemes in global and regional climate models.
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| 7. |
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| 8. |
- Ast, Anne, et al.
(author)
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mHTT Seeding Activity : A Marker of Disease Progression and Neurotoxicity in Models of Huntington's Disease
- 2018
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In: Molecular Cell. - : Elsevier BV. - 1097-2765. ; 71:5, s. 6-688
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Journal article (peer-reviewed)abstract
- Self-propagating, amyloidogenic mutant huntingtin (mHTT) aggregates may drive progression of Huntington's disease (HD). Here, we report the development of a FRET-based mHTT aggregate seeding (FRASE) assay that enables the quantification of mHTT seeding activity (HSA) in complex biosamples from HD patients and disease models. Application of the FRASE assay revealed HSA in brain homogenates of presymptomatic HD transgenic and knockin mice and its progressive increase with phenotypic changes, suggesting that HSA quantitatively tracks disease progression. Biochemical investigations of mouse brain homogenates demonstrated that small, rather than large, mHTT structures are responsible for the HSA measured in FRASE assays. Finally, we assessed the neurotoxicity of mHTT seeds in an inducible Drosophila model transgenic for HTTex1. We found a strong correlation between the HSA measured in adult neurons and the increased mortality of transgenic HD flies, indicating that FRASE assays detect disease-relevant, neurotoxic, mHTT structures with severe phenotypic consequences in vivo. Ast et al. present the development of a FRET-based aggregate seeding (FRASE) assay that facilitates the detection and quantification of mHTT seeding activity (HSA) in complex biosamples. They show that HSA is detectable in brains of presymptomatic Huntington's disease (HD) mice and correlates with disease progression and neurotoxicity in HD transgenic flies.
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| 9. |
- Cienciala, E, et al.
(author)
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Canopy transpiration from a boreal forest in Sweden during a dry year
- 1997
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In: AGRICULTURAL AND FOREST METEOROLOGY. - : ELSEVIER SCIENCE BV. - 0168-1923. ; 86:3-4, s. 157-167
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Journal article (other academic/artistic)abstract
- Estimation of areal evapotranspiration is crucial for the parameterization of the soil-vegetation-atmosphere interface in climate models and for the assessment of land-use changes on water resources. Present knowledge on how areal forest evapotranspiratio
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| 10. |
- Gottschalk, L, et al.
(author)
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Scale aggregation - comparison of flux estimates from NOPEX
- 1999
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In: AGRICULTURAL AND FOREST METEOROLOGY. - : ELSEVIER SCIENCE BV. - 0168-1923. ; 98-9, s. 103-119
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Journal article (peer-reviewed)abstract
- The NOPEX two concentrated field efforts (CFEs) (June 1994 and April-July 1995) provide high quality data sets for the Boreal environment. The analysis of these data with traditional meteorological and hydrological approaches allow estimations of fluxes o
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| 11. |
- Grelle, A, et al.
(author)
-
Seasonal variation of boreal forest surface conductance and evaporation
- 1999
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In: AGRICULTURAL AND FOREST METEOROLOGY. - : ELSEVIER SCIENCE BV. - 0168-1923. ; 98-9, s. 563-578
-
Journal article (peer-reviewed)abstract
- Long term measurements (June 1994 to December 1996) of evaporation were made in a boreal forest in central Sweden. Fluxes were measured continuously with eddy-correlation systems from a 100 m tower. Surface conductance and potential evaporation were estim
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| 12. |
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| 13. |
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| 14. |
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| 15. |
- Hyvonen, R., et al.
(author)
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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
-
In: New Phytologist. - Cambridge : Wiley. - 0028-646X .- 1469-8137. ; 173:3, s. 463-480
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Research review (peer-reviewed)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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| 16. |
- Iritz, Z, et al.
(author)
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Test of a modified Shuttleworth-Wallace estimate of boreal forest evaporation
- 1999
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In: AGRICULTURAL AND FOREST METEOROLOGY. - : ELSEVIER SCIENCE BV. - 0168-1923. ; 98-9, s. 605-619
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Journal article (peer-reviewed)abstract
- A modified version of the two-layer Shuttleworth-Wallace approach was used to simulate evaporation from a mixed 50-100 years oldboreal forest stand in central Sweden. It was tested against eddy correlation flux measurements from the Northern hemisphere cl
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| 17. |
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| 18. |
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| 19. |
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| 20. |
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| 21. |
- Molder, M, et al.
(author)
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Flux-profile relationships over a boreal forest - roughness sublayer corrections
- 1999
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In: AGRICULTURAL AND FOREST METEOROLOGY. - : ELSEVIER SCIENCE BV. - 0168-1923. ; 98-9, s. 645-658
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Journal article (peer-reviewed)abstract
- Calculation of fluxes from profile measurements above forest stands have for some time been considered unfeasible and profiles have primarily been used to only characterise the lowest part of the planetary boundary layer. Extension of traditional theory t
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| 22. |
- Nemitz, E, et al.
(author)
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Standardisation of eddy-covariance flux measurements of methane and nitrous oxide
- 2018
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In: International Agrophysics. - : Walter de Gruyter GmbH. - 0236-8722 .- 2300-8725. ; 32, s. 517-549
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Journal article (peer-reviewed)abstract
- Commercially available fast-response analysers for methane (CH4) and nitrous oxide (N2O) have recently become more sensitive, more robust and easier to operate. This has made their application for long-term flux measurements with the eddycovariance method more feasible. Unlike for carbon dioxide (CO2) and water vapour (H2O), there have so far been no guidelines on how to optimise and standardise the measurements. This paper reviews the state-of-the-art of the various steps of the measurements and discusses aspects such as instrument selection, setup and maintenance, data processing as well as the additional measurements needed to aid interpretation and gap-filling. It presents the methodological protocol for eddy covariance measurements of CH4 and N2O fluxes as agreed for the ecosystem station network of the pan-European Research Infrastructure Integrated Carbon Observation System and provides a first international standard that is suggested to be adopted more widely. Fluxes can be episodic and the processes controlling the fluxes are complex, preventing simple mechanistic gap-filling strategies. Fluxes are often near or below the detection limit, requiring additional care during data processing. The protocol sets out the best practice for these conditions to avoid biasing the results and long-term budgets. It summarises the current approach to gap-filling.
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| 23. |
- Peichl, M., et al.
(author)
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Energy exchange and water budget partitioning in a boreal minerogenic mire
- 2013
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In: Journal of Geophysical Research-Biogeosciences. - : American Geophysical Union (AGU). - 0148-0227 .- 2169-8953. ; 118:1, s. 1-13
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Journal article (peer-reviewed)abstract
- [1] This study investigated patterns and controls of the seasonal and inter-annual variations in energy fluxes (i.e., sensible heat, H, and latent heat, λE) and partitioning of the water budget (i.e., precipitation, P; evapotranspiration, ET; discharge, Q; and soil water storage, ∆S) over five years (2001–2005) in a boreal oligotrophic fen in northern Sweden based on continuous eddy covariance, water table level (WTL), and weir measurements. For the growing season (May 1 to September 31), the 5year averages (± standard deviation) of the midday (10:00 to 14:00h) Bowen ratio (β, i.e., H/λE) was 0.86±0.08. Seasonal and inter-annual variability of β was mainly driven by λE which itself was strongly controlled by both weather (i.e., vapor pressure deficit, D, and net radiation, Rn) and physiological parameters (i.e., surface resistance). During the growing season, surface resistance largely exceeded aerodynamic resistance, which together with low mean values of the actual ET to potential ET ratio (0.55±0.05) and Priestley-Taylor α (0.89) suggests significant physiological constrains on ET in this well-watered fen. Among the water budget components, the inter-annual variability of ET was lower (199 to 298mm) compared to Q (225 to 752mm), with each accounting on average for 34 and 65% of the ecosystem water loss, respectively. The fraction of P expended into ET was negatively correlated to P and positively to Rn. Although a decrease in WTL caused a reduction of the surface conductance, the overall effect of WTL on ET was limited. Non-growing season (October 1 to April 30) fluxes of H, λE, and Q were significant representing on average −67%, 13%, and 61%, respectively, of their growing season sums (negative sign indicates opposite flux direction between the two seasons). Overall, our findings suggest that plant functional type composition, P and Rn dynamics (i.e., amount and timing) were the major controls on the partitioning of the mire energy and water budgets. This has important implications for the regional climate as well as for ecosystem development, nutrient, and carbon dynamics.
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| 24. |
- Rasmus, S., et al.
(author)
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Estimation of winter leaf area index and sky view fraction for snow modelling in boreal coniferous forests : Consequences on snow mass and energy balance
- 2013
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In: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 27:20, s. 2876-2891
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Journal article (peer-reviewed)abstract
- Leaf area index (LAI) and canopy coverage are important parameters when modelling snow process in coniferous forests, controlling interception and transmitting radiation. Estimates of LAI and sky view factor show large variability depending on the estimation method used, and it is not clear how this is reflected in the calculated snow processes beneath the canopy. In this study, the winter LAI and sky view fraction were estimated using different optical and biomass-based approximations in several boreal coniferous forest stands in Fennoscandia with different stand density, age and site latitude. The biomass-based estimate of LAI derived from forest inventory data was close to the values derived from the optical measurements at most sites, suggesting that forest inventory data can be used as input to snow hydrological modelling. Heterogeneity of tree species and site fertility, as well as edge effects between different forest compartments, caused differences in the LAI estimates at some sites. A snow energy and mass balance model (SNOWPACK) was applied to detect how the differences in the estimated values of the winter LAI and sky view fraction were reflected in simulated snow processes. In the simulations, an increase in LAI and a decrease in sky view fraction changed the snow surface energy balance by decreasing shortwave radiation input and increasing longwave radiation input. Changes in LAI and sky view fraction affected directly snow accumulation through altered throughfall fraction and indirectly snowmelt through the changed surface energy balance. Changes in LAI and sky view fraction had a greater impact on mean incoming radiation beneath the canopy than on other energy fluxes. Snowmelt was affected more than snow accumulation. The effect of canopy parameters on evaporation loss from intercepted snow was comparable with the effect of variation in governing meteorological variables such as precipitation intensity and air temperature.
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| 25. |
- Tanja, S, et al.
(author)
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Air temperature triggers the recovery of evergreen boreal forest photosynthesis in spring
- 2003
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In: Global Change Biology. - : Wiley. - 1354-1013. ; 9:10, s. 1410-1426
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Journal article (peer-reviewed)abstract
- The timing of the commencement of photosynthesis (P-*) in spring is an important determinant of growing-season length and thus of the productivity of boreal forests. Although controlled experiments have shed light on environmental mechanisms triggering release from photoinhibition after winter, quantitative research for trees growing naturally in the field is scarce. In this study, we investigated the environmental cues initiating the spring recovery of boreal coniferous forest ecosystems under field conditions. We used meteorological data and above-canopy eddy covariance measurements of the net ecosystem CO2 exchange (NEE) from five field stations located in northern and southern Finland, northern and southern Sweden, and central Siberia. The within- and intersite variability for P-* was large, 30-60 days. Of the different climate variables examined, air temperature emerged as the best predictor for P-* in spring. We also found that 'soil thaw', defined as the time when near-surface soil temperature rapidly increases above 0degreesC, is not a useful criterion for P-*. In one case, photosynthesis commenced 1.5 months before soil temperatures increased significantly above 0degreesC. At most sites, we were able to determine a threshold for air-temperature-related variables, the exceeding of which was required for P-*. A 5-day running-average temperature (T-5) produced the best predictions, but a developmental-stage model (S) utilizing a modified temperature sum concept also worked well. But for both T-5 and S, the threshold values varied from site to site, perhaps reflecting genetic differences among the stands or climate-induced differences in the physiological state of trees in late winter/early spring. Only at the warmest site, in southern Sweden, could we obtain no threshold values for T-5 or S that could predict P-* reliably. This suggests that although air temperature appears to be a good predictor for P-* at high latitudes, there may be no unifying ecophysiological relationship applicable across the entire boreal zone.
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| 26. |
- Grelle, A., et al.
(author)
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Large carbon-sink potential by Kyoto forests in Sweden - A case study on willow plantations
- 2007
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In: Tellus Series B-Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 59:5, s. 910-918
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Journal article (peer-reviewed)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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| 27. |
- Gustafsson, David, et al.
(author)
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Boreal forest surface parameterization in the ECMWF model - 1D test with NOPEX long-term data
- 2003
-
In: Journal of applied meteorology (1988). - 0894-8763 .- 1520-0450. ; 42:1, s. 95-112
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Journal article (peer-reviewed)abstract
- The objective of the present study was to assess the performance and recent improvements of the land surface scheme used operationally in the European Centre for Medium-Range Weather Forecasts (ECMWF) in a Scandinavian boreal forest climate/ecosystem. The previous (the 1999 scheme of P. Viterbo and A. K. Betts) and the new (Tiled ECMWF Surface Scheme for Exchange Processes over Land, TESSEL) surface schemes were validated by single-column runs against data from NOPEX (Northern Hemisphere Climate-Processes Land-Surface Experiment). Driving and validation datasets were prepared for a 3-yr period (1994-96). The new surface scheme, with separate surface energy balances for subgrid fractions (tiling), improved predictions of seasonal as well as diurnal variation in surface energy fluxes in comparison with the old scheme. Simulated wintertime evaporation improved significantly as a consequence of the introduced additional aerodynamic resistance for evaporation from snow lying under high vegetation. Simulated springtime evaporation also improved because the limitation of transpiration in frozen soils was now accounted for. However, downward sensible heat flux was still underestimated during winter, especially at nighttime, whereas soil temperatures were underestimated in winter and overestimated in summer. The new scheme also underestimated evaporation during dry periods in summer, whereas soil moisture was overestimated. Sensitivity tests showed that further improvements of simulated surface heat fluxes and soil temperatures could be obtained by calibration of parameters governing the coupling between the surface and the atmosphere and the ground heat flux, and parameters governing the water uptake by the vegetation. Model performance also improved when the seasonal variation in vegetation properties was included.
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| 28. |
- Lagergren, Fredrik, et al.
(author)
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Net primary production and light use efficiency in a mixed coniferous forest in Sweden
- 2005
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In: Plant, Cell and Environment. - : Wiley. - 0140-7791 .- 1365-3040. ; 28:3, s. 412-423
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Journal article (peer-reviewed)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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| 29. |
- Lindroth, Anders, et al.
(author)
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Gudrun - en kolbomb
- 2005
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In: Miljöforskning : Formas tidning för ett uthålligt samhälle. - 1650-4925. ; 5-6, s. 22-24
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Journal article (pop. science, debate, etc.)
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| 30. |
- Lindroth, Anders, et al.
(author)
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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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In: Biogeochemistry. - : Springer Science and Business Media LLC. - 0168-2563 .- 1573-515X. ; 89:1, s. 43-60
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Journal article (peer-reviewed)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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| 31. |
- Lindroth, Anders, et al.
(author)
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Skogars kolbalans
- 2002
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In: [Publication information missing].
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Journal article (pop. science, debate, etc.)
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| 32. |
- Magnani, F, et al.
(author)
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The human footprint in the carbon cycle of temperate and boreal forests
- 2007
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In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885. ; 447, s. 848-850
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Journal article (peer-reviewed)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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| 33. |
- Sagerfors, J., et al.
(author)
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Annual CO2 exchange between a nutrient-poor, minerotrophic, boreal mire and the atmosphere
- 2008
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In: Journal of Geophysical Research-Biogeosciences. - 0148-0227 .- 2169-8961. ; 113:G1
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Journal article (peer-reviewed)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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