Eight years of continuous carbon fluxes measurements in a Portuguese eucalypt stand under two main events: Drought and felling

Rodrigues, Abel; Pita, Gabriel; Mateus, João; Kurz‐Besson, Cathy; Casquilho, Miguel; Cerasoli, Sofia; Gomes, Alberto Azevedo; Pereira, J. S.

doi:10.1016/j.agrformet.2010.12.007

Cited by 36 publications

(14 citation statements)

References 45 publications

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“…For example, RE follows the same dynamic patterns as GPP from daily to seasonal scales (Krishnan et al, 2009; et al, 2011; Thomas et al, 2009). Annually, GPP and RE are both enhanced in humid years, but repressed in dry years (Hussain et al, 2011;Rodrigues et al, 2011); especially, both of them are remarkably reduced in extreme drought years Reichstein et al, 2007a).…”

Section: Introductionmentioning

confidence: 88%

Covariation between gross primary production and ecosystem respiration across space and the underlying mechanisms: A global synthesis

Chen

Zhu

et al. 2015

Agricultural and Forest Meteorology

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a b s t r a c tGross primary production (GPP) and ecosystem respiration (RE) are two important processes in the terrestrial carbon cycle. Understanding the relationships between GPP and RE across space, as well as the underlying mechanisms, is helpful for understanding the terrestrial carbon cycle and predicting the global carbon budget. In this study, we investigated the correlation between the spatial variations in GPP and RE by compiling carbon flux data from 264 sites across the Asian, European, North American, South American, African, and Oceanian regions. The results indicated that GPP and RE covaried across space regionally and globally (P < 0.001). The spatial variations in GPP explained 66-98% of the variations in RE in the six regions (approximately explained 60-76% when considered the effects of self-correlation caused by current flux partitioning algorithm), and it explained 90% of RE variations at the global scale (about 70% when considered the effects of self-correlation). RE/GPP values were not significantly different among the six regions or between the two hemispheres. RE/GPP values consistently averaged at 0.87 ± 0.04 along the spatial variations in climate and vegetation index. This covariation between GPP and RE across space is largely attributed to the parallel responses of GPP and RE to the common climatic and vegetation factors, but the underlying mechanism lies in productivity as the primary and direct substrate supplier for respiration which fundamentally constrains RE. These results suggest that the variation in photosynthate availability is the dominant driver for respiration across space and that this process must be fully considered in the cross-site RE comparisons.

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Section: Introductionmentioning

confidence: 88%

Covariation between gross primary production and ecosystem respiration across space and the underlying mechanisms: A global synthesis

Chen

Zhu

et al. 2015

Agricultural and Forest Meteorology

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“…Duursama et al, 2009;Grote et al, 2011;Rodrigues et al, 2011), the variation of the overall in-and outflow of carbon between the years is mostly small, indicating that drought plays only a minor role as a limiting condition at this site. Although RWC frequently drops below the threshold value in summer (most frequent in the pure stand, least often in the mixed stand), it falls only seldom below 0.5 [in average 17 (PP), 5 (ED), and 9 (MS) days per year].…”

Section: Carbon Balancementioning

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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“…A trend towards extreme events in the form of droughts is observed due to a more heterogeneous distribution of precipitation throughout the year (Zeppel et al, 2014;García-Barrón et al, 2013). These types of changes in precipitation regime have been reported as strongly affecting the local water balance (Rodrigues et al, 2011;Vaz et al, 2010;Grant et al, 2010) and carbon sink strength (Pérez-Ramos et al, 2013;Pereira et al, 2007;Granier et al, 2007;Ciais et al, 2005) of ecosystems in semi-arid regions, and are expected to increase with proceeding climate change (Bussotti et al, 2013;Guerreiro et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Drought impact on carbon and water cycling in a Mediterranean <i>Quercus suber</i> L. woodland during the extreme drought event in 2012

et al. 2014

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Abstract. Savannah-type ecosystems account for 26-30 % of global gross primary productivity GPP, with water being one of the major driving factors. In Europe, savannah-type woodlands cover an area of about 1.5 million ha. Here, the recent past has shown a significant decrease in precipitation P in winter and spring as well as a decrease in total annual precipitation. Strong effects on local water balance and carbon sink strength have thus been reported due to changes in precipitation regime.The objective of this study is to quantify the impact of the extreme drought event in 2012 on the water balance, gross primary productivity and carbon sink strength of a typical Portuguese cork-oak woodland (montado) compared to the wet year of 2011. Physiological responses of the dominant tree species Quercus suber (L.) are disentangled employing combined photosynthesis and stomatal conductance modelling.Precipitation effectiveness ET/P increased from 86 % in 2011 to 122 % in the 2012 dry year due to deep soil or groundwater access of the Q. suber trees leaving no water for groundwater replenishment. Understorey and overstorey GPP were strongly reduced, by 53 and 28 %, respectively, in 2012 compared to 2011, due to the late onset of the autumn rains in 2011 and an additional severe winter/spring drought. However, the ecosystem was still a carbon sink in both years, but with a 38 % reduced sink strength under extreme drought in 2012 compared to 2011. The combined photosynthesis-stomatal conductance model yielded the best results if it was allowed to adjust photosynthetic and stomatal parameters simultaneously. If stomatal response was modelled with the Leuning approach, which allows for a different sensitivity to vapour pressure deficit, the stomatal model parameters were highly coupled. A change in either of the parameters needed to be compensated by the other to guarantee a stable sensitivity of stomatal conductance to assimilation, independent of variations in vapour pressure deficit. The Q. suber trees showed a 37 % reduced stomatal conductance during the drought period of 2012 compared to 2011, due to water supply limitations. In response to reduced leafinternal CO 2 availability, the trees strongly reduced the apparent maximum carboxylation rate by 43 % in 2012 compared to 2011. Unexpectedly, the optimum temperature T opt of the maximum electron transport rate decreased during the drought period, enhancing the susceptibility of the trees to high temperature stress during the summer.Our results suggest that, if the trend of decreasing annual precipitation and changed precipitation patterns on the Iberian Peninsula continues, sustained effects on local groundwater reservoirs, understorey species composition and tree mortality have to be expected in the long term.Published by Copernicus Publications on behalf of the European Geosciences Union. A. Piayda et al.: Drought impact on carbon and water cyclingTo model the effect of drought on the montado ecosystem successfully, variable apparent maximum carboxylation rate V c,max...

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Eight years of continuous carbon fluxes measurements in a Portuguese eucalypt stand under two main events: Drought and felling

Cited by 36 publications

References 45 publications

Covariation between gross primary production and ecosystem respiration across space and the underlying mechanisms: A global synthesis

Covariation between gross primary production and ecosystem respiration across space and the underlying mechanisms: A global synthesis

Challenges for evaluating process-based models of gas exchange

Drought impact on carbon and water cycling in a Mediterranean <i>Quercus suber</i> L. woodland during the extreme drought event in 2012

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Eight years of continuous carbon fluxes measurements in a Portuguese eucalypt stand under two main events: Drought and felling

Cited by 36 publications

References 45 publications

Covariation between gross primary production and ecosystem respiration across space and the underlying mechanisms: A global synthesis

Covariation between gross primary production and ecosystem respiration across space and the underlying mechanisms: A global synthesis

Challenges for evaluating process-based models of gas exchange

Drought impact on carbon and water cycling in a Mediterranean &lt;i&gt;Quercus suber&lt;/i&gt; L. woodland during the extreme drought event in 2012

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About

Drought impact on carbon and water cycling in a Mediterranean <i>Quercus suber</i> L. woodland during the extreme drought event in 2012