Increasing net CO2 uptake by a Danish beech forest during the period from 1996 to 2009

Pilegaard, Kim; Ibrom, Andreas; Courtney, Michael; Hummelshøj, P.; Jensen, N.O.

doi:10.1016/j.agrformet.2011.02.013

Cited by 141 publications

(100 citation statements)

References 40 publications

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“…Recent data for 2011 are consistent with these trends. This contrasts with the observed increasing NEP trend of 23 g C m −2 yr −1 observed over 14 yr in a similarly aged beech stand in Denmark, attributed to increasing GPP (Pilegaard et al, 2011).…”

Section: Annual C Budget Of Woodlands In Britain and Irelandcontrasting

confidence: 54%

“…The importance of indirect climatic events such as insectinduced canopy defoliation is becoming evident from the growing network of long-term forest EC studies (Allard et al, 2008;Pilegaard et al, 2011). In this study the observed reduction in NEP that occurred in 2009 and 2010 could in part be attributed to the major outbreak of defoliating moth caterpillars, which caused a significant reduction in peak LAI.…”

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confidence: 66%

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Inter-annual variation of carbon uptake by a plantation oak woodland in south-eastern England

et al. 2012

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Abstract. The carbon balance of an 80-yr-old deciduous oak plantation in the temperate oceanic climate of the south-east of Great Britain was measured by eddy covariance over 12 yr (1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010). The mean annual net ecosystem productivity (NEP) was 486 g C m −2 yr −1 (95 % CI of ±73 g C m −2 yr −1 ), and this was partitioned into a gross primary productivity (GPP) of 2034 ± 145 g C m −2 yr −1 , over a 165 (± 6) day growing season, and an annual loss of carbon through respiration and decomposition (ecosystem respiration, R eco ) of 1548 ± 122 g C m −2 yr −1 . Although the maximum variation of NEP between years was large (333 g C m −2 yr −1 ), the ratio of R eco /GPP remained relatively constant (0.76 ± 0.02 CI). Some anomalies in the annual patterns of the carbon balance could be linked to particular weather events, such as low summer solar radiation and low soil moisture content (values below 30 % by volume). The European-wide heat wave and drought of 2003 did not reduce the NEP of this woodland because of good water supply from the surface-water gley soil. The inter-annual variation in estimated intercepted radiation only accounted for ∼ 47 % of the variation in GPP, although a significant relationship (p < 0.001) was found between peak leaf area index and annual GPP, which modified the efficiency with which incident radiation was used in net CO 2 uptake. Whilst the spring start and late autumn end of the net CO 2 uptake period varied substantially (range of 24 and 27 days respectively), annual GPP was not related to growing season length. Severe outbreaks of defoliating moth caterpillars, mostly Tortrix viridana L. and Operophtera brumata L., caused considerable damage to the forest canopy in 2009 and 2010, resulting in reduced GPP in these two years. Inter-annual variation in the sensitivity of R eco to temperature was found to be strongly related to summer soil moisture content. The eddy covariance estimates of NEP closely matched mensurationbased estimates, demonstrating that this forest was a substantial sink of carbon over the 12-yr measurement period.

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Section: Annual C Budget Of Woodlands In Britain and Irelandcontrasting

confidence: 54%

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confidence: 66%

Inter-annual variation of carbon uptake by a plantation oak woodland in south-eastern England

et al. 2012

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“…Moisture can affect the relation between NEE and temperature either directly by limiting respiration or by changing the transport processes of heat and CO 2 . Another reason for negative correlations between NEE and temperature has been revealed by Pilegaard et al (2011). They found a change of the correlation sign (from positive to negative) during leaf fall related to an increase of substrate availability.…”

Section: Correlation Between Nighttime Nee and Temperaturementioning

confidence: 94%

On the choice of the driving temperature for eddy-covariance carbon dioxide flux partitioning

et al. 2012

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Abstract. Networks that merge and harmonise eddycovariance measurements from many different parts of the world have become an important observational resource for ecosystem science. Empirical algorithms have been developed which combine direct observations of the net ecosystem exchange of carbon dioxide with simple empirical models to disentangle photosynthetic (GPP) and respiratory fluxes (R eco ). The increasing use of these estimates for the analysis of climate sensitivities, model evaluation and calibration demands a thorough understanding of assumptions in the analysis process and the resulting uncertainties of the partitioned fluxes. The semi-empirical models used in flux partitioning algorithms require temperature observations as input, but as respiration takes place in many parts of an ecosystem, it is unclear which temperature input -air, surface, bole, or soil at a specific depth -should be used. This choice is a source of uncertainty and potential biases.In this study, we analysed the correlation between different temperature observations and nighttime NEE (which equals nighttime respiration) across FLUXNET sites to understand the potential of the different temperature observations as input for the flux partitioning model. We found that the differences in the correlation between different temperature data streams and nighttime NEE are small and depend on the selection of sites. We investigated the effects of the choice of the temperature data by running two flux partitioning algorithms with air and soil temperature. We found the time lag (phase shift) between air and soil temperatures explains the differences in the GPP and R eco estimates when using either air or soil temperatures for flux partitioning. The impact of the source of temperature data on other derived ecosystem parameters was estimated, and the strongest impact was found for the temperature sensitivity. Overall, this study suggests that the choice between soil or air temperature must be made on site-by-site basis by analysing the correlation between temperature and nighttime NEE. We recommend using an ensemble of estimates based on different temperature observations to account for the uncertainty due to the choice of temperature and to assure the robustness of the temporal patterns of the derived variables.

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“…The sites covered various climates and ecosystems representative of the European continent and were each dominated by a single tree or grass species. The forest sites are Hyytiälä in Finland Portillo-Estrada et al, 2013), Männikjärve in Estonia (Carter et al, 2012;Portsmuth et al, 2005), Sorø in Denmark (Pilegaard et al, 2011), and Speulderbos in the Netherlands (Portillo-Estrada et al, 2013), while the grassland sites are Easter Bush in the UK (Jones et al, 2011) and Bugac in Hungary (Machon et al, 2015). The details of the sites are provided in Table 1.…”

Section: Study Sitesmentioning

confidence: 99%

Climatic controls on leaf litter decomposition across European forests and grasslands revealed by reciprocal litter transplantation experiments

et al. 2016

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Abstract. Carbon (C) and nitrogen (N) cycling under future climate change is associated with large uncertainties in litter decomposition and the turnover of soil C and N. In addition, future conditions (especially altered precipitation regimes and warming) are expected to result in changes in vegetation composition, and accordingly in litter species and chemical composition, but it is unclear how such changes could potentially alter litter decomposition. Litter transplantation experiments were carried out across six European sites (four forests and two grasslands) spanning a large geographical and climatic gradient (5.6-11.4 • C in annual temperature 511-878 mm in precipitation) to gain insight into the climatic controls on litter decomposition as well as the effect of litter origin and species.The decomposition k rates were overall higher in warmer and wetter sites than in colder and drier sites, and positively correlated with the litter total specific leaf area. Also, litter N content increased as less litter mass remained and decay went further.Surprisingly, this study demonstrates that climatic controls on litter decomposition are quantitatively more important than species or site of origin. Cumulative climatic variables, precipitation, soil water content and air temperature (ignoring days with air temperatures below zero degrees Celsius), were appropriate to predict the litter remaining mass during decomposition (M r ). M r and cumulative air temperature were found to be the best predictors for litter carbon and nitrogen remaining during the decomposition. Using mean annual air temperature, precipitation, soil water content and Published by Copernicus Publications on behalf of the European Geosciences Union. M. Portillo-Estrada et al.: Climatic controls on leaf litter decompositionlitter total specific leaf area as parameters we were able to predict the annual decomposition rate (k) accurately.

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Increasing net CO2 uptake by a Danish beech forest during the period from 1996 to 2009

Cited by 141 publications

References 40 publications

Inter-annual variation of carbon uptake by a plantation oak woodland in south-eastern England

Inter-annual variation of carbon uptake by a plantation oak woodland in south-eastern England

On the choice of the driving temperature for eddy-covariance carbon dioxide flux partitioning

Climatic controls on leaf litter decomposition across European forests and grasslands revealed by reciprocal litter transplantation experiments

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