Modelling five years of weather-driven variation of GPP in a boreal forest

Mäkelä, Annikki; Kolari, Pasi; Karimäki, Janne; Nikinmaa, Eero; Perämäki, Martti; Hari, Pertti

doi:10.1016/j.agrformet.2006.08.017

Cited by 97 publications

(74 citation statements)

References 36 publications

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“…To account for lag effects between the response of to temperature variations we allow again for the lag effect using the lag-parameter α applied to T S (Eq. 9) as it has proven to be significant in similar light use efficiency model approaches as proposed by Mäkelä et al (2006Mäkelä et al ( , 2008 for sites in temperate and boreal climates. However, in cases of W being the main driver of as it is the case in semi-arid climates, the lag function is applied to W instead of T S .…”

Section: Formulating the Generalized Modelmentioning

confidence: 99%

Identification of a general light use efficiency model for gross primary production

Horn

Schulz

2011

Biogeosciences

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Abstract. Non-stationary and non-linear dynamic time series analysis tools are applied to multi-annual eddy covariance and micrometeorological data from 44 FLUXNET sites to derive a light use efficiency model for gross primary production on a daily basis. The extracted typical behaviour of the canopies in response to meteorological forcing leads to a model formulation allowing for a variable influence of the environmental drivers temperature and moisture availability modulating the light use efficiency. Thereby, the model is applicable to a broad range of vegetation types and climatic conditions. The proposed model explains large proportions of the variation of the gross carbon uptake at the study sites while the optimized set of six parameters is well defined. With the parameters showing explainable and meaningful relations to site-specific environmental conditions, the model has the potential to serve as basis for general regionalization strategies for large scale carbon flux predictions.

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Section: Formulating the Generalized Modelmentioning

confidence: 99%

Identification of a general light use efficiency model for gross primary production

Horn

Schulz

2011

Biogeosciences

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“…Mammarella et al, 2009). Total ecosystem respiration (TER) and GPP were extracted from the measured NEE as described in Mäkelä et al (2006). EC flux measurements used in this study for model evaluation have also been published in Suni et al (2003), Ilvesniemi et al (2009), andIlvesniemi et al (2010).…”

Section: Description Of Site Properties and Measurementsmentioning

confidence: 99%

Challenges for evaluating process-based models of gas exchange

Grote

Korhonen²,

Mammarella³

2011

For. syst.

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Physiologically-based (or process-based) models are commonly applied to describe plant responses mechanistically in dependence on environmental conditions. They are increasingly evaluated with eddy-covariance measurements that integrate carbon and water exchange of an area of several hectares (called the fetch). However, almost all models applied to date in such exercises have considered only the dominant tree species and neglected other species that contributed to the measured gas exchange rates-either in separate patches or in mixture. This decreases the transferability of the model from one site to another because the contributions from other species might be different. It is therefore a major challenge in modeling today to separate the measured gas exchanges by sources.In this study, a detailed physiologically-based biosphere model is applied that allows distinguishing between tree species in mixed forests, considering them as «vegetation cohorts» that interact with each other. The sensitivity of the model to different assumptions about how different tree species contribute to an integrated measurement of standscale gas exchange is investigated. The model exercise is carried out for a forest site in Finland with dominant Scots pine but presence of significant amounts of Norway spruce and birch. The results demonstrate that forest structure affects simulated gas exchange rates indicating a possible importance of considering differences in physiological properties at the species level. It is argued that the variation of stand structure within the range of eddy-covariance measurements should be better accounted for in models and that inventory measurements need to consider this variation.Key words: forest structure; understorey; physiologically-oriented model; eddy-flux measurements; sensitivity analysis. ResumenRetos para la evaluación de modelos basados en procesos de intercambio de gases en rodales con diversas especies Los modelos con base fisiológica (o basados en procesos) se aplican habitualmente para describir las respuestas de la planta mecanísticamente dependiendo de las condiciones ambientales. Son evaluados cada vez más frecuentemente con mediciones de eddy-covariance que integran el intercambio de carbono y el agua de una superficie de varias hectáreas. Sin embargo, casi todos los modelos aplicados hasta la fecha han considerado sólo las especies arbóreas dominantes y se han descuidado otras especies que contribuyen a las tasas de intercambio gaseosos medidas-ya sea en zonas separadas o en mezcla. Esto disminuye la posibilidad de transferir el modelo de un sitio a otro debido a que las contribuciones de otras especies pueden ser diferentes. Por tanto, es un reto importante en la modelización separar el intercambio gaseoso medido por fuente emisora.En este estudio, se aplica un modelo detallado con base fisiológica de la biosfera que permite distinguir entre las especies de árboles en bosques mixtos, considerándolas como «cohortes de vegetación» que interaccionan unos con otros. Se estudia l...

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“…Pelkonen and Hari, 1980;Suni et al, 2003). Therefore, the annual balance is affected especially by the temperature in the autumns and springs (Mäkelä et al, 2006). During those periods, the difference in temperature sensitivity of photosynthesis and respiration processes is an important controller of the carbon balance.…”

Section: Introductionmentioning

confidence: 99%

“…The model results suggested that the reason for elevated carbon losses in warm autumns is the stronger positive temperature sensitivity of TER compared to GPP. In the autumn, the day length has been used as a proxy for GPP limitation Mäkelä et al, 2006;Bergeron et al, 2007). Thus, any changes in temperature are likely to be more strongly reflected in respiration rate rather than in assimilation.…”

mentioning

confidence: 99%

Autumn temperature and carbon balance of a boreal Scots pine forest in Southern Finland

et al. 2010

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Abstract. We analyzed the dynamics of carbon balance components: gross primary production (GPP) and total ecosystem respiration (TER), of a boreal Scots pine forest in Southern Finland. The main focus is on investigations of environmental drivers of GPP and TER and how they affect the inter-annual variation in the carbon balance in autumn (September-December). We used standard climate data and CO 2 exchange measurements collected by the eddy covariance (EC) technique over 11 years. EC data revealed that increasing autumn temperature significantly enhances TER: the temperature sensitivity was 9.5 gC m −2 • C −1 for the period September-October (early autumn when high radiation levels still occur) and 3.8 gC m −2 • C −1 for NovemberDecember (late autumn with suppressed radiation level). The cumulative GPP was practically independent of the temperature in early autumn. In late autumn, air temperature could explain part of the variation in GPP but the temperature sensitivity was very weak, less than 1 gC m −2 • C −1 . Two models, a stand photosynthesis model (COCA) and a global vegetation model (ORCHIDEE), were used for estimating stand GPP and its sensitivity to the temperature. The ORCHIDEE model was tested against the observations of GPP derived from EC data. The stand photosynthesis model COCA predicted that under a predescribed 3-6 • C temperature increase, the temperature sensitivity of 4-5 gC m −2 • C −1 in GPP may appear in early autumn. The analysis by the ORCHIDEE model revealed the model sensitivity to the temporal treatCorrespondence to: T. Vesala (timo.vesala@helsinki.fi) ment of meteorological forcing. The model predictions were similar to observed ones when the site level 1/2-hourly time step was applied, but the results calculated by using daily meteorological forcing, interpolated to 1/2-hourly time step, were biased. This is due to the nonlinear relationship between the processes and the environmental factors.

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Modelling five years of weather-driven variation of GPP in a boreal forest

Cited by 97 publications

References 36 publications

Identification of a general light use efficiency model for gross primary production

Identification of a general light use efficiency model for gross primary production

Challenges for evaluating process-based models of gas exchange

Autumn temperature and carbon balance of a boreal Scots pine forest in Southern Finland

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