Modelling leaf gas exchange in holm-oak trees in southern Spain

Infante, Juan Manuel; Damesin, Claire; Rambal, Serge; Fernández-Alés, Rocı́o

doi:10.1016/s0168-1923(99)00033-7

Cited by 36 publications

(24 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For instance, integrating θ variation in BA site in the first 3 m depth and at 13.3 m of distance -the half of mean distance among trees with 18 trees ha −1 -, the transpiration rate estimated for the summer period was 7 265 L ha with 34% canopy cover versus 18 trees ha −1 and 21% in BA site) [16,17]. Hence, although θ varied little during summer, the huge volume of soil explored by Q. ilex root system [29], allows trees to uptake a high volume of water, 19.3, 43.3 and 37.4% from the first, second and third meter depth, respectively.…”

Section: Deep Water Consumption By Treesmentioning

confidence: 99%

“…The spacing of trees in dehesas is advantageous in terms of water potential and CO 2 assimilation rates at leaf and tree scale along the summer [16,28], compared to other holm-oak forest systems [39,40]. Joffre et al [22] pointed out that the dehesa structure follows an ecohydrological equilibrium sensu Eagleson [8], who hypothesised that water limits natural vegetation systems, providing a canopy density that produces both minimum water stress and maximum biomass.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effets de chênes verts isolés sur les variations spatiales et temporelles de l’humidité du sol dans les dehesas du centre-ouest de l’Espagne

Cubera

Moreno

2007

Ann. For. Sci.

View full text Add to dashboard Cite

-The spatial and temporal evolution of soil water content (θ) in Quercus ilex dehesas has been investigated to determine how trees modify the soil water dynamics and the nature of tree-grass interactions in terms of soil water use in these ecosystems. Soil physical parameters and θ were measured at different distances from the tree trunk (2−30 m) in the upper 300 cm of soil. les valeurs moyennes de θ furent plus élevées au-delà de la canopée que sous les arbres. La diminution de θ au-delà de la canopée des arbres a continué à diminuer encore en été lorsque les plantes herbacées étaient sèches, suggérant un prélèvement d'eau par les arbres. Nos résultats suggèrent alors que les arbres peuvent utiliser de l'eau localisée loin deux même à des distances de 20 m. et qu'ils sont très dépendants des réserves d'eau en profondeur (100−300 cm) pendant la fin du printemps et en été, ce qui contribue à diminuer la concurrence pour l'eau entre arbres et strate herbacée.contenu en eau du sol / TDR / Quercus ilex / chênaie / interaction arbre-herbacées

show abstract

Section: Deep Water Consumption By Treesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effets de chênes verts isolés sur les variations spatiales et temporelles de l’humidité du sol dans les dehesas du centre-ouest de l’Espagne

Cubera

Moreno

2007

Ann. For. Sci.

View full text Add to dashboard Cite

show abstract

“…When soil or atmospheric water is insufficient, leaf stomatal conductance reduces and correspondingly CO 2 fixation is limited (Dang et al, 1997;Hogg et al, 2000;Grant et al, 2006a). Extensive studies have demonstrated the influence of SWC on C fixation at leaf (Infante et al, 1999;Lawlor, 1995) and canopy (Reichstein et al, 2002;Rambal et al, 2003) levels. For three Mediterranean evergreen forests, drought caused lightsaturated ecosystem gross C fixation and day-time averaged canopy conductance to decline by up to 90% and ecosystem water-use efficiency relative to the gross C fixation to decrease (Reichstein et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Modeling the impact of drought on canopy carbon and water fluxes for a subtropical evergreen coniferous plantation in southern China through parameter optimization using an ensemble Kalman filter

Wang

et al. 2010

Biogeosciences

View full text Add to dashboard Cite

Abstract. Soil and atmospheric water deficits have significant influences on CO 2 and energy exchanges between the atmosphere and terrestrial ecosystems. Model parameterization significantly affects the ability of a model to simulate carbon, water, and energy fluxes. In this study, an ensemble Kalman filter (EnKF) and observations of gross primary productivity (GPP) and latent heat (LE) fluxes were used to optimize model parameters significantly affecting the calculation of these fluxes for a subtropical coniferous plantation in southeastern China. The optimized parameters include the maximum carboxylation rate (Vc max ), the slope in the modified Ball-Berry model (M) and the coefficient determining the sensitivity of stomatal conductance to atmospheric water vapor deficit (D 0 ). Optimized Vc max and M showed larger variations than D 0 . Seasonal variations of Vc max and Mwere more pronounced than the variations between the two years. Vc max and M were associated with soil water content (SWC). During dry periods, SWC at the 20 cm depth explained 61% and 64% of variations of Vc max and M, respectively. EnKF parameter optimization improved the simulations of GPP, LE and SH, mainly during dry periods. After parameter optimization using EnKF, the variations of GPP, LE and SH explained by the model increased by 1% to 4% at half-hourly steps and by 3% to 5% at daily time steps. Further efforts are needed to differentiate the real causes of parameter variations and improve the ability of models to describe the change of stomatal conductance with net photosynthesis rate and the sensitivity of photosynthesis capacity to soil water stress under different environmental conditions.

show abstract

“…Algunos autores han obtenido valores próximos o superiores a 3 m 2 m -2 , pero en masas densas de encina (Bussotti et al, 2002;Hoff et al, 2002). Sin embargo, en trabajos realizados en dehesas de encina los valores son muy próximos a los observados en este trabajo, así Infante et al, (1999) obtuvieron valores entre 1,6 y 2,5 m 2 m -2 , en formaciones de densidad parecida a las de este trabajo. El bajo valor de LAI obtenido pudo estar influenciado por el mal estado del arbolado, ya que la parcela presenta síntomas de decaimiento, con defoliaciones parciales y fenómenos de puntisecado, muy frecuentes en la dehesas de Andalucía (Navarro Cerrillo et al, 2004).…”

Section: Discussionunclassified

LIDAR-based estimation of leaf area index on Holm oak [Quercus ilex L. subsp. ballota (Desf.) Samp.] trees

Bonilla¹

2010

For. syst.

View full text Add to dashboard Cite

IntroducciónLIDAR (Light Detection And Ranging) es una tecnología emergente en el campo de los sensores láser, capaz de generar con gran rapidez alta densidad de datos georeferenciados con una precisión al menos igual que la obtenida por los métodos tradicionales sobre el terreno, pero significativamente más rápido (Renslow et al., 2000). Aunque los métodos de campo son generalmente más precisos, la relación entre el error y la eficacia en la adquisición hace que los datos LIDAR sean considerados una alternativa real a los métodos tradicionales. Se trata de equipos formados por sen- = 0,60 (RMSE = 0,16) y R 2 = 0,62 (RMSE = 0,21) para ecuaciones de tipo cuadrático y potencial respectivamente. Las variaciones entre el LAI de campo y el LAI LIDAR pueden atribuirse a la distribución de las hojas en la copa, la interferencia de elementos leñosos como ramas y ramillas, y la distribución vertical de los elementos de la copa. Las técnicas LIDAR han mostrado un resultado satisfactorio en el cálculo de LAI en encina, aunque su generalización depende de su coste y de la facilidad para ser aplicados sobre superficies grandes.Palabras clave: dehesas, teledetección, parámetros foliares, estructura de copa. Abstract LIDAR-based estimation of leaf area index on Holm oak [Quercus ilex L. subsp. ballota (Desf.) Samp.] treesThe aim of this paper was to estimate Leaf Area Index (LAI) of Quercus ilex by calculating the laser-intercepted rate through the forest canopy using LiDAR data. LAI was measured in 40 trees with a hemispheric camera (NIKON Coolpix 4500) and coincided with the acquisition of LIDAR data. The LiDAR-derived LAI LIDAR was then estimated by applying a value of the inverse of the coefficient of extinction of 1 / K = 1.48. The in-field LAI values varied between 1.01 m 2 m -2 and 1.61 m 2 m -2 . From a comparison of the LiDAR-derived to the field-derived LAI, the coefficients of the determination for the coefficient of extinction of 1.48 was R 2 = 0.60 (RMSE = 0.16) for quadratic and R 2 = 0.62 (RMSE = 0.21) for potential correlations. The change in accuracy was attributed to the density of leaves, the interference by stems, and the vertical number of branches in the forest stands. The LIDAR sensor technique gives a satisfactory result in the obtainment of leaf parameters in Holm oak trees, although its generalisation on field studies depends on its cost and suitability to be applied over large surfaces.

show abstract

Modelling leaf gas exchange in holm-oak trees in southern Spain

Cited by 36 publications

References 48 publications

Effets de chênes verts isolés sur les variations spatiales et temporelles de l’humidité du sol dans les dehesas du centre-ouest de l’Espagne

Effets de chênes verts isolés sur les variations spatiales et temporelles de l’humidité du sol dans les dehesas du centre-ouest de l’Espagne

Modeling the impact of drought on canopy carbon and water fluxes for a subtropical evergreen coniferous plantation in southern China through parameter optimization using an ensemble Kalman filter

LIDAR-based estimation of leaf area index on Holm oak [Quercus ilex L. subsp. ballota (Desf.) Samp.] trees

Contact Info

Product

Resources

About