81 results on '"Pacheco-Labrador, J."'
Search Results
2. Heatwave breaks down the linearity between sun-induced fluorescence and gross primary production
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Martini, D, Sakowska, K, Wohlfahrt, G, Pacheco-Labrador, J, van der Tol, C, Porcar-Castell, A, Magney, T, Carrara, A, Colombo, R, El-Madany, T, Gonzalez-Cascon, R, Martin, M, Julitta, T, Moreno, G, Rascher, U, Reichstein, M, Rossini, M, Migliavacca, M, Martini D., Sakowska K., Wohlfahrt G., Pacheco-Labrador J., van der Tol C., Porcar-Castell A., Magney T. S., Carrara A., Colombo R., El-Madany T. S., Gonzalez-Cascon R., Martin M. P., Julitta T., Moreno G., Rascher U., Reichstein M., Rossini M., Migliavacca M., Martini, D, Sakowska, K, Wohlfahrt, G, Pacheco-Labrador, J, van der Tol, C, Porcar-Castell, A, Magney, T, Carrara, A, Colombo, R, El-Madany, T, Gonzalez-Cascon, R, Martin, M, Julitta, T, Moreno, G, Rascher, U, Reichstein, M, Rossini, M, Migliavacca, M, Martini D., Sakowska K., Wohlfahrt G., Pacheco-Labrador J., van der Tol C., Porcar-Castell A., Magney T. S., Carrara A., Colombo R., El-Madany T. S., Gonzalez-Cascon R., Martin M. P., Julitta T., Moreno G., Rascher U., Reichstein M., Rossini M., and Migliavacca M.
- Abstract
Sun-induced fluorescence in the far-red region (SIF) is increasingly used as a remote and proximal-sensing tool capable of tracking vegetation gross primary production (GPP). However, the use of SIF to probe changes in GPP is challenged during extreme climatic events, such as heatwaves. Here, we examined how the 2018 European heatwave (HW) affected the GPP–SIF relationship in evergreen broadleaved trees with a relatively invariant canopy structure. To do so, we combined canopy-scale SIF measurements, GPP estimated from an eddy covariance tower, and active pulse amplitude modulation fluorescence. The HW caused an inversion of the photosynthesis–fluorescence relationship at both the canopy and leaf scales. The highly nonlinear relationship was strongly shaped by nonphotochemical quenching (NPQ), that is, a dissipation mechanism to protect from the adverse effects of high light intensity. During the extreme heat stress, plants experienced a saturation of NPQ, causing a change in the allocation of energy dissipation pathways towards SIF. Our results show the complex modulation of the NPQ–SIF–GPP relationship at an extreme level of heat stress, which is not completely represented in state-of-the-art coupled radiative transfer and photosynthesis models.
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- 2022
3. Performance of Singular Spectrum Analysis in Separating Seasonal and Fast Physiological Dynamics of Solar-Induced Chlorophyll Fluorescence and PRI Optical Signals
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Biriukova, K, Pacheco-Labrador, J, Migliavacca, M, Mahecha, M, Gonzalez-Cascon, R, Martin, M, Rossini, M, Biriukova K., Pacheco-Labrador J., Migliavacca M., Mahecha M. D., Gonzalez-Cascon R., Martin M. P., Rossini M., Biriukova, K, Pacheco-Labrador, J, Migliavacca, M, Mahecha, M, Gonzalez-Cascon, R, Martin, M, Rossini, M, Biriukova K., Pacheco-Labrador J., Migliavacca M., Mahecha M. D., Gonzalez-Cascon R., Martin M. P., and Rossini M.
- Abstract
High temporal resolution measurements of solar-induced chlorophyll fluorescence (F) and the Photochemical Reflectance Index (PRI) encode vegetation functioning. However, these signals are modulated by time-dependent processes. We tested the applicability of the Singular Spectrum Analysis (SSA) for disentangling fast components (physiology-driven) and slow components (controlled by structural and biochemical properties) from PRI, far-red F (F760), and far-red apparent fluorescence yield (Fy∗760). The proof of concept was developed on spectral and flux time series simulated with the Soil Canopy Observation of Photochemistry and Energy fluxes (SCOPE) model. This allowed the evaluation of SSA decomposition against variables that are independent of physiology or are modified by it. Slow SSA-decomposed components of PRI and Fy∗760 showed high correlations with the reference variables (R2 = 0.97 and 0.96, respectively). Fast SSA-decomposed components of PRI and Fy∗760 were better related to the physiological reference variables than the original signals during periods when leaf area index (LAI) was above 1 m2 m−2. The method was also successfully applied to predict light-use efficiency (LUE) from the fast SSA-decomposed components of PRI (R2 = 0.70) and Fy∗760 (R2 = 0.68) when discarding data modeled with LAI < 1 m2 m−2 and short-wave radiation Rin < 250 W m−2. The method was then tested on data acquired in a Mediterranean grassland. In this case, the fast SSA-decomposed component of apparent LUE∗ showed a stronger correlation with the fast SSA-decomposed component of Fy∗760 (R2 = 0.42) than with original Fy∗760 (R2 = 0.01). SSA-based approach is a promising tool for decoupling physiological information from measurements acquired with automated proximal sensing systems.
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- 2021
4. Challenging the link between functional and spectral diversity with radiative transfer modeling and data
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Pacheco-Labrador, J., Migliavacca, M., Ma, X., Mahecha, Miguel Dario, Carvalhais, N., Weber, U., Benavides, R., Bouriaud, O., Barnoaiea, I., Coomes, D.A., Bohn, Friedrich, Kraemer, Guido, Heiden, U., Huth, Andreas, Wirth, C., Pacheco-Labrador, J., Migliavacca, M., Ma, X., Mahecha, Miguel Dario, Carvalhais, N., Weber, U., Benavides, R., Bouriaud, O., Barnoaiea, I., Coomes, D.A., Bohn, Friedrich, Kraemer, Guido, Heiden, U., Huth, Andreas, and Wirth, C.
- Abstract
In a context of accelerated human-induced biodiversity loss, remote sensing (RS) is emerging as a promising tool to map plant biodiversity from space. Proposed approaches often rely on the Spectral Variation Hypothesis (SVH), linking the heterogeneity of terrestrial vegetation to the variability of the spectroradiometric signals. Yet, due to observational limitations, the SVH has been insufficiently tested, remaining unclear which metrics, methods, and sensors could provide the most reliable estimates of plant biodiversity. Here we assessed the potential of RS to infer plant biodiversity using radiative transfer simulations and inversion. We focused specifically on “functional diversity,” which represents the spatial variability in plant functional traits. First, we simulated vegetation communities and evaluated the information content of different functional diversity metrics (FDMs) derived from their optical reflectance factors (R) or the corresponding vegetation “optical traits,” estimated via radiative transfer model inversion. Second, we assessed the effect of the spatial resolution, the spectral characteristics of the sensor, and signal noise on the relationships between FDMs derived from field and remote sensing datasets. Finally, we evaluated the plausibility of the simulations using Sentinel-2 (multispectral, 10 m pixel) and DESIS (hyperspectral, 30 m pixel) imagery acquired over sites of the Functional Significance of Forest Biodiversity in Europe (FunDivEUROPE) network. We demonstrate that functional diversity can be inferred both by reflectance and optical traits. However, not all the FDMs tested were suited for assessing plant functional diversity from RS. Rao's Q index, functional dispersion, and functional richness were the best-performing metrics. Furthermore, we demonstrated that spatial resolution is the most limiting RS feature. In agreement with simulations, Sentinel-2 imagery provided better estimates of plant diversity than DESIS, despite the c
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- 2022
5. Sun-induced chlorophyll fluorescence II: Review of passive measurement setups, protocols, and their application at the leaf to canopy level
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Aasen, H, Van Wittenberghe, S, Medina, N, Damm, A, Goulas, Y, Wieneke, S, Hueni, A, Malenovsky, Z, Alonso, L, Pacheco-Labrador, J, Cendrero-Mateo, M, Tomelleri, E, Burkart, A, Cogliati, S, Rascher, U, Arthur, A, Aasen H., Van Wittenberghe S., Medina N. S., Damm A., Goulas Y., Wieneke S., Hueni A., Malenovsky Z., Alonso L., Pacheco-Labrador J., Cendrero-Mateo M. P., Tomelleri E., Burkart A., Cogliati S., Rascher U., Arthur A. M., Aasen, H, Van Wittenberghe, S, Medina, N, Damm, A, Goulas, Y, Wieneke, S, Hueni, A, Malenovsky, Z, Alonso, L, Pacheco-Labrador, J, Cendrero-Mateo, M, Tomelleri, E, Burkart, A, Cogliati, S, Rascher, U, Arthur, A, Aasen H., Van Wittenberghe S., Medina N. S., Damm A., Goulas Y., Wieneke S., Hueni A., Malenovsky Z., Alonso L., Pacheco-Labrador J., Cendrero-Mateo M. P., Tomelleri E., Burkart A., Cogliati S., Rascher U., and Arthur A. M.
- Abstract
Imaging and non-imaging spectroscopy employed in the field and from aircraft is frequently used to assess biochemical, structural, and functional plant traits, as well as their dynamics in an environmental matrix. With the increasing availability of high-resolution spectroradiometers, it has become feasible to measure fine spectral features, such as those needed to estimate sun-induced chlorophyll fluorescence (F), which is a signal related to the photosynthetic process of plants. The measurement of F requires highly accurate and precise radiance measurements in combination with very sophisticated measurement protocols. Additionally, because F has a highly dynamic nature (compared with other vegetation information derived from spectral data) and low signal intensity, several environmental, physiological, and experimental aspects have to be considered during signal acquisition and are key for its reliable interpretation. The European Cooperation in Science and Technology (COST) Action ES1309 OPTIMISE has produced three articles addressing the main challenges in the field of F measurements. In this paper, which is the second of three, we review approaches that are available to measure F from the leaf to the canopy scale using ground-based and airborne platforms. We put specific emphasis on instrumental aspects, measurement setups, protocols, quality checks, and data processing strategies. Furthermore, we review existing techniques that account for atmospheric influences on F retrieval, address spatial scaling effects, and assess quality checks and the metadata and ancillary data required to reliably interpret retrieved F signals.
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- 2019
6. Sun-induced chlorophyll fluorescence III: Benchmarking retrieval methods and sensor characteristics for proximal sensing
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Cendrero-Mateo, M, Wieneke, S, Damm, A, Alonso, L, Pinto, F, Moreno, J, Guanter, L, Celesti, M, Rossini, M, Sabater, N, Cogliati, S, Julitta, T, Rascher, U, Goulas, Y, Aasen, H, Pacheco-Labrador, J, Arthur, A, Cendrero-Mateo M. P., Wieneke S., Damm A., Alonso L., Pinto F., Moreno J., Guanter L., Celesti M., Rossini M., Sabater N., Cogliati S., Julitta T., Rascher U., Goulas Y., Aasen H., Pacheco-Labrador J., Arthur A. M., Cendrero-Mateo, M, Wieneke, S, Damm, A, Alonso, L, Pinto, F, Moreno, J, Guanter, L, Celesti, M, Rossini, M, Sabater, N, Cogliati, S, Julitta, T, Rascher, U, Goulas, Y, Aasen, H, Pacheco-Labrador, J, Arthur, A, Cendrero-Mateo M. P., Wieneke S., Damm A., Alonso L., Pinto F., Moreno J., Guanter L., Celesti M., Rossini M., Sabater N., Cogliati S., Julitta T., Rascher U., Goulas Y., Aasen H., Pacheco-Labrador J., and Arthur A. M.
- Abstract
The interest of the scientific community on the remote observation of sun-induced chlorophyll fluorescence (SIF) has increased in the recent years. In this context, hyperspectral ground measurements play a crucial role in the calibration and validation of future satellite missions. For this reason, the European cooperation in science and technology (COST) Action ES1309 OPTIMISE has compiled three papers on instrument characterization, measurement setups and protocols, and retrieval methods (current paper). This study is divided in two sections; first, we evaluated the uncertainties in SIF retrieval methods (e.g., Fraunhofer line depth (FLD) approaches and spectral fitting method (SFM)) for a combination of of-the-shelf commercial spectrometers. Secondly, we evaluated how an erroneous implementation of the retrieval methods increases the uncertainty in the estimated SIF values. Results show that the SFM approach applied to high-resolution spectra provided the most reliable SIF retrieval with a relative error (RE) ≤ 6% and < 5% for F 687 and F 760 , respectively. Furthermore, although the SFM was the least affected by an inaccurate definition of the absorption spectral window (RE = 5%) and/or interpolation strategy (RE = 15-30%), we observed a sensitivity of the SIF retrieval for the simulated training data underlying the SFM model implementation.
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- 2019
7. Nitrogen and phosphorus effect on sun-induced fluorescence and gross primary productivity in mediterranean grassland
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Martini, D, Pacheco-Labrador, J, Perez-Priego, O, van der Tol, C, El-Madany, T, Julitta, T, Rossini, M, Reichstein, M, Christiansen, R, Rascher, U, Moreno, G, Pilar Martin, M, Yang, P, Carrara, A, Guan, J, Gonzalez-Cascon, R, Migliavacca, M, Martini D., Pacheco-Labrador J., Perez-Priego O., van der Tol C., El-Madany T. S., Julitta T., Rossini M., Reichstein M., Christiansen R., Rascher U., Moreno G., Pilar Martin M., Yang P., Carrara A., Guan J., Gonzalez-Cascon R., Migliavacca M., Martini, D, Pacheco-Labrador, J, Perez-Priego, O, van der Tol, C, El-Madany, T, Julitta, T, Rossini, M, Reichstein, M, Christiansen, R, Rascher, U, Moreno, G, Pilar Martin, M, Yang, P, Carrara, A, Guan, J, Gonzalez-Cascon, R, Migliavacca, M, Martini D., Pacheco-Labrador J., Perez-Priego O., van der Tol C., El-Madany T. S., Julitta T., Rossini M., Reichstein M., Christiansen R., Rascher U., Moreno G., Pilar Martin M., Yang P., Carrara A., Guan J., Gonzalez-Cascon R., and Migliavacca M.
- Abstract
Sun-Induced fluorescence at 760 nm (F760) is increasingly being used to predict gross primary production (GPP) through light use efficiency (LUE) modeling, even though the mechanistic processes that link the two are not well understood. We analyzed the effect of nitrogen (N) and phosphorous (P) availability on the processes that link GPP and F760 in a Mediterranean grassland manipulated with nutrient addition. To do so, we used a combination of process-based modeling with Soil-Canopy Observation of Photosynthesis and Energy (SCOPE), and statistical analyses such as path modeling. With this study, we uncover the mechanisms that link the fertilization-driven changes in canopy nitrogen concentration (N%) to the observed changes in F760 and GPP. N addition changed plant community structure and increased canopy chlorophyll content, which jointly led to changes in photosynthetic active radiation (APAR), ultimately affecting both GPP and F760. Changes in the abundance of graminoids, (%graminoids) driven by N addition led to changes in structural properties of the canopy such as leaf angle distribution, that ultimately influenced observed F760 by controlling the escape probability of F760 (Fesc). In particular, we found a change in GPP-F760 relationship between the first and the second year of the experiment that was largely driven by the effect of plant type composition on Fesc, whose best predictor is %graminoids. The P addition led to a statistically significant increase on light use efficiency of fluorescence emission (LUEf), in particular in plots also with N addition, consistent with leaf level studies. The N addition induced changes in the biophysical properties of the canopy that led to a trade-off between surface temperature (Ts), which decreased, and F760 at leaf scale (F760leaf,fw), which increased. We found that Ts is an important predictor of the light use efficiency of photosynthesis, indicating the importance of Ts in LUE modeling approaches to predict GPP
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- 2019
8. Multiple-constraint inversion of SCOPE. Evaluating the potential of GPP and SIF for the retrieval of plant functional traits
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Pacheco-Labrador, J, Perez-Priego, O, El-Madany, T, Julitta, T, Rossini, M, Guan, J, Moreno, G, Carvalhais, N, Martin, M, Gonzalez-Cascon, R, Kolle, O, Reischtein, M, van der Tol, C, Carrara, A, Martini, D, Hammer, T, Moossen, H, Migliavacca, M, Pacheco-Labrador J., Perez-Priego O., El-Madany T. S., Julitta T., Rossini M., Guan J., Moreno G., Carvalhais N., Martin M. P., Gonzalez-Cascon R., Kolle O., Reischtein M., van der Tol C., Carrara A., Martini D., Hammer T. W., Moossen H., Migliavacca M., Pacheco-Labrador, J, Perez-Priego, O, El-Madany, T, Julitta, T, Rossini, M, Guan, J, Moreno, G, Carvalhais, N, Martin, M, Gonzalez-Cascon, R, Kolle, O, Reischtein, M, van der Tol, C, Carrara, A, Martini, D, Hammer, T, Moossen, H, Migliavacca, M, Pacheco-Labrador J., Perez-Priego O., El-Madany T. S., Julitta T., Rossini M., Guan J., Moreno G., Carvalhais N., Martin M. P., Gonzalez-Cascon R., Kolle O., Reischtein M., van der Tol C., Carrara A., Martini D., Hammer T. W., Moossen H., and Migliavacca M.
- Abstract
The most recent efforts to provide remote sensing (RS) estimates of plant function rely on the combination of Radiative Transfer Models (RTM) and Soil-Vegetation-Atmosphere Transfer (SVAT) models, such as the Soil-Canopy Observation Photosynthesis and Energy fluxes (SCOPE) model. In this work we used ground spectroradiometric and chamber-based CO2 flux measurements in a nutrient manipulated Mediterranean grassland in order to: 1) develop a multiple-constraint inversion approach of SCOPE able to retrieve vegetation biochemical, structural as well as key functional traits, such as chlorophyll concentration (Cab), leaf area index (LAI), maximum carboxylation rate (Vcmax) and the Ball-Berry sensitivity parameter (m); and 2) compare the potential of the of gross primary production (GPP) and sun-induced fluorescence (SIF), together with up-welling Thermal Infrared (TIR) radiance and optical reflectance factors (RF), to estimate such parameters. The performance of the proposed inversion method as well as of the different sets of constraints was assessed with contemporary measurements of water and heat fluxes and leaf nitrogen content, using pattern-oriented model evaluation. The multiple-constraint inversion approach proposed together with the combination of optical RF and diel GPP and TIR data provided reliable estimates of parameters, and improved predicted water and heat fluxes. The addition of SIF to this scheme slightly improved the estimation of m. Parameter estimates were coherent with the variability imposed by the fertilization and the seasonality of the grassland. Results revealed that fertilization had an impact on Vcmax, while no significant differences were found for m. The combination of RF, SIF and diel TIR data weakly constrained functional traits. Approaches not including GPP failed to estimate LAI; however GPP overestimated Cab in the dry period. These problems might be related to the presence of high fractions of senescent leaves in the grassland. The pr
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- 2019
9. Photosynthesis-sun induced fluorescence relationship in a Mediterranean grassland
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Martini, D, Pacheco-Labrador, J, Perez-Priego, O, Van Der Tol, C, El Madany, T, Julitta, T, Rossini, M, Gitelson, A, Reichstein, M, Migliavacca, M, Martini D., Pacheco-Labrador J., Perez-Priego O., Van Der Tol C., El Madany T., Julitta T., Rossini M., Gitelson A., Reichstein M., Migliavacca M., Martini, D, Pacheco-Labrador, J, Perez-Priego, O, Van Der Tol, C, El Madany, T, Julitta, T, Rossini, M, Gitelson, A, Reichstein, M, Migliavacca, M, Martini D., Pacheco-Labrador J., Perez-Priego O., Van Der Tol C., El Madany T., Julitta T., Rossini M., Gitelson A., Reichstein M., and Migliavacca M.
- Abstract
Sun induced fluorescence at 760 nm (F 760 ) has shown to provide a valid approach to quantify gross primary production (GPP) at various scales, however the relationship between GPP and F 760 is influenced by the escape probability of fluorescence (Fesc), a variable which is not still fully understood. Combining radiative transfer modelling approaches, by means of the SCOPE model, and a data driven methodology based on variable selection methods we identify the predictors of Fesc, focusing on the effect of functional and structural traits. We show that Fesc is mainly predicted by structural variables such as fraction of grasses and near infrared reflectance. Building on the analysis of the predictor of Fesc, LUE p and LUE f we present a semi-empirical model formulation based only on optical data that significantly improves the GPP prediction.
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- 2018
10. Assessing the use of multiple constraints and ancillary data to support scope model inversion in a experimental grassland
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Pacheco-Labrador, J, Carvalhais, N, Perez-Priego, O, El-Madany, T, Rossini, M, Julitta, T, Moreno, G, Gonzalez-Cascon, R, Pilar Martin, M, Reichstein, M, Carrara, A, Guanter, L, Migliavacca, M, Pacheco-Labrador J., Carvalhais N., Perez-Priego O., El-Madany T. S., Rossini M., Julitta T., Moreno G., Gonzalez-Cascon R., Pilar Martin M., Reichstein M., Carrara A., Guanter L., Migliavacca M., Pacheco-Labrador, J, Carvalhais, N, Perez-Priego, O, El-Madany, T, Rossini, M, Julitta, T, Moreno, G, Gonzalez-Cascon, R, Pilar Martin, M, Reichstein, M, Carrara, A, Guanter, L, Migliavacca, M, Pacheco-Labrador J., Carvalhais N., Perez-Priego O., El-Madany T. S., Rossini M., Julitta T., Moreno G., Gonzalez-Cascon R., Pilar Martin M., Reichstein M., Carrara A., Guanter L., and Migliavacca M.
- Abstract
The SCOPE model embeds the state of art for coupling soil vegetation atmosphere transfer (SVAT) and radiative transfer models (RTM). For that reason the FLuorescence EXplorer (FLEX) mission selected this model to derive vegetation properties through inversion. However inverse problem is often ill-posed, providing equally likely solutions and hence inflating the uncertainty of the retrieved parameters. In this work we test the use of different priors based on ancillary measurements and literature to support multiple-constrain inversion of SCOPE. Results show that prior information on the relationships between variables such as leaf chlorophyll content (Cab), leaf carotenoids content (Cca), leaf water content (Cw) and/or maximum carboxylation rate (Vcmax) reduce inversion uncertainties and overfitting, and should be sampled/estimated together with optical data.
- Published
- 2018
11. Effects of varying solar-view geometry and canopy structure on solar-induced chlorophyll fluorescence and PRI
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Biriukova, K, Celesti, M, Evdokimov, A, Pacheco-Labrador, J, Julitta, T, Migliavacca, M, Giardino, C, Miglietta, F, Colombo, R, Panigada, C, Rossini, M, Biriukova, Khelvi, Celesti, Marco, Evdokimov, Anton, Pacheco-Labrador, Javier, Julitta, Tommaso, Migliavacca, Mirco, Giardino, Claudia, Miglietta, Franco, Colombo, Roberto, Panigada, Cinzia, Rossini, Micol, Biriukova, K, Celesti, M, Evdokimov, A, Pacheco-Labrador, J, Julitta, T, Migliavacca, M, Giardino, C, Miglietta, F, Colombo, R, Panigada, C, Rossini, M, Biriukova, Khelvi, Celesti, Marco, Evdokimov, Anton, Pacheco-Labrador, Javier, Julitta, Tommaso, Migliavacca, Mirco, Giardino, Claudia, Miglietta, Franco, Colombo, Roberto, Panigada, Cinzia, and Rossini, Micol
- Abstract
The increasing amount of continuous time series of solar-induced fluorescence (SIF) and vegetation indices (e.g. Photochemical Reflectance Index, PRI) acquired with high temporal (sub-minute) frequencies is foreseen to allow tracking of the structural and physiological changes of vegetation in a variety of ecosystems. Coupled with observations of CO2, water, and energy fluxes from eddy covariance flux towers, these measurements can bring new insights into the remote monitoring of ecosystem functioning. However, continuously changing solar-view geometry imposes directional effects on diurnal cycles of the fluorescence radiance in the observation direction (F) and PRI, controlled by structural and biochemical vegetation properties. An improved understanding of these variations can potentially help to disentangle directional responses of vegetation from physiological ones in the continuous long-term optical measurements and, therefore, allow to deconvolve the physiological information relevant to ecosystem functioning. Moreover, this will also be useful for better interpreting and validating F and PRI satellite products (e.g., from the upcoming ESA FLEX mission). Many previous studies focused on the characterization of reflectance directionality, but only a handful of studies investigated directional effects on F and vegetation indices related to plant physiology. The aim of this study is to contribute to the understanding of red (F687) and far-red (F760) fluorescence and PRI anisotropy based on field spectroscopy data and simulations with the Soil-Canopy Observation of Photochemistry and Energy fluxes (SCOPE) model. We present an extensive dataset of multi-angular measurements of F and PRI collected at canopy level with a high-resolution instrument (FloX, JB Hyperspectral Devices UG, Germany) over different ecosystems: Mediterranean grassland, alfalfa, chickpea and rice. We found, that F760 and F687 directional responses of horizontally homogeneous canopies are charac
- Published
- 2020
12. Estimación de variables esenciales de la vegetación en un ecosistema de dehesa utilizando factores de reflectividad simulados estacionalmente
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Martín, M. P., primary, Pacheco-Labrador, J., additional, González-Cascón, R., additional, Moreno, G., additional, Migliavacca, M., additional, García, M., additional, Yebra, M., additional, and Riaño, D., additional
- Published
- 2020
- Full Text
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13. EVALUATING THE POTENTIAL OF DESIS TO INFER PLANT TAXONOMICAL AND FUNCTIONAL DIVERSITIES IN EUROPEAN FORESTS.
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Pacheco-Labrador, J., Weber, U., Ma, X., Mahecha, M. D., Carvalhais, N., Wirth, C., Huth, A., Bohn, F. J., Kraemer, G., Heiden, U., FunDivEUROPE members, and Migliavacca, M.
- Subjects
SPECTRAL reflectance ,REMOTE sensing ,ENVIRONMENTAL degradation ,FOREST biodiversity ,SENSE data ,SURFACE of the earth - Abstract
Tackling the accelerated human-induced biodiversity loss requires tools able to map biodiversity and its changes globally. Remote sensing (RS) offers unique capabilities of characterizing Earth surfaces; therefore, it could map plant biodiversity continuously and globally. This approach is supported by the Spectral Variation Hypothesis (SVH), which states that spectra and species (taxonomic and trait) diversities are linked through environmental heterogeneity. In this work, we evaluate the capability of the DESIS hyperspectral imager to capture plant diversity patterns as measured in dedicated plots of the network FunDivEUROPE. We computed functional and taxonomical diversity metrics from field taxonomic, structural, and foliar measurements in vegetation plots sampled in Spain and Romania. In addition, we also computed functional diversity metrics both from the DESIS reflectance factors and from vegetation parameters estimated via inversion of a radiative transfer model. Results showed that only metrics computed from spectral reflectance were able to capture taxonomic variability in the area. However, the lack of sensitivity was related to the insufficient plot size and the lack of spatial match between remote sensing and field data, but also the differences between the information contained in the field traits and remote sensing data, and the potential uncertainties in the remote estimates of vegetation parameters. Thus, while DESIS showed some sensitivity to plant diversity, further efforts are needed to deploy suitable biodiversity evaluation and validation plots and networks that support the development of biodiversity remote sensing products. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
14. Spatio-Temporal Relationships between Optical Information and Carbon Fluxes in a Mediterranean Tree-Grass Ecosystem
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Pacheco-Labrador, J., El-Madany, T., Martín, M., Migliavacca, M., Rossini, M., Carrara, A., Zarco-Tejada, P., Ministerio de Economía y Competitividad (España), Ministerio de Ciencia e Innovación (España), Federal Ministry of Economics and Technology (Germany), Pacheco-Labrador, Javier [0000-0003-3401-7081], Carrara, Arnaud [0000-0002-9095-8807], Martín, M. Pilar [0000-0002-5563-8461], Zarco-Tejada, Pablo J. [0000-0003-1433-6165], Pacheco Labrador, J, El Madany, T, Martín, M, Migliavacca, M, Rossini, M, Carrara, A, Zarco Tejada, P, Pacheco-Labrador, Javier, Carrara, Arnaud, Martín, M. Pilar, and Zarco-Tejada, Pablo J.
- Subjects
Light use efficiency ,Remote Sensing (RS) ,fPAR ,Science ,F PAR ,Footprint ,footprint ,MODIS GPP ,Semi-empirical GPP model ,Mismatch ,FPAR ,light use efficiency ,PRI ,Gross Primary Production (GPP) ,Earth and Planetary Sciences (all) ,mismatch ,semi-empirical GPP model - Abstract
Spatio-temporal mismatches between Remote Sensing (RS) and Eddy Covariance (EC) data as well as spatial heterogeneity jeopardize terrestrial Gross Primary Production (GPP) modeling. This article combines: (a) high spatial resolution hyperspectral imagery; (b) EC footprint climatology estimates; and (c) semi-empirical models of increasing complexity to analyze the impact of these factors on GPP estimation. Analyses are carried out in a Mediterranean Tree-Grass Ecosystem (TGE) that combines vegetation with very different physiologies and structure. Half-hourly GPP (GPP) were predicted with relative errors ~36%. Results suggest that, at EC footprint scale, the ecosystem signals are quite homogeneous, despite tree and grass mixture. Models fit using EC and RS data with high degree of spatial and temporal match did not significantly improved models performance; in fact, errors were explained by meteorological variables instead. In addition, the performance of the different models was quite similar. This suggests that none of the models accurately represented light use efficiency or the fraction of absorbed photosynthetically active radiation. This is partly due to model formulation; however, results also suggest that the mixture of the different vegetation types might contribute to hamper such modeling, and should be accounted for GPP models in TGE and other heterogeneous ecosystems., This research was funded by the following projects: FLUχPEC “Monitoring changes in water and carbon fluxes from remote and proximal sensing in a Mediterranean dehesa ecosystem” (http://www.lineas.cchs.csic.es/fluxpec) (CGL2012-34383, Spanish Ministry of Economy and Competitiveness), DEHESHyrE Transnational Access Project (EUFAR), MaNiP “MAnipulation NItrogen and Phosporous” (https://www.bgc-jena.mpg.de/bgi/index.php/Research/ManipProject) (MPI-BGC and the Alexander Von Humsboldt Foundation through the Markus Reichstein Prize), BIOSPEC “Linking spectral information at different spatial scales with biophysical parameters of Mediterranean vegetation in the context of Global Change” (http://www.lineas.cchs.csic.es/biospec) (CGL2008-02301/CLI, Ministry of Science and Innovation) and CEOS-Spain (http://ceosspain.lpi.uv.es/home/project) (AYA2011-29334-C02-01, Ministry of Economy and Competitiveness); FLUχPEC: “Monitoring changes in water and carbon fluxes from remote and proximal sensing in Mediterranean “dehesa” ecosystem” (http://www.lineas.cchs.csic.es/ fluxpec) (CGL2012-34383, Spanish Ministry of Economy and Competitiveness); and the EnMAP project MoReDEHESHyReS “Modelling Responses of Dehesas with Hyperspectral Remote Sensing” (Contract No. 50EE1621) (https://www.bgc-jena.mpg.de/bgi/index.php/Research/MoReDEHESHyReS) (German Aerospace Center (DLR) and the German Federal Ministry of Economic Affairs and Energy
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- 2017
15. Improving the performance of 3-D radiative transfer model FLIGHT to simulate optical properties of a tree-grass ecosystem
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Melendo-Vega, J. R., Martín, M. P., Pacheco-Labrador, J., González Cascon, María Rosario, Moreno, G., Pérez, F., Migliavacca, M., García, M., North, P., Riaño, D., Melendo-Vega, J. R., Martín, M. P., Pacheco-Labrador, J., González Cascon, María Rosario, Moreno, G., Pérez, F., Migliavacca, M., García, M., North, P., and Riaño, D.
- Abstract
The 3-D Radiative Transfer Model (RTM) FLIGHT can represent scattering in open forest or savannas featuring underlying bare soils. However, FLIGHT might not be suitable for multilayered tree-grass ecosystems (TGE), where a grass understory can dominate the reflectance factor (RF) dynamics due to strong seasonal variability and low tree fractional cover. To address this issue, we coupled FLIGHT with the 1-D RTM PROSAIL. The model is evaluated against spectral observations of proximal and remote sensing sensors: the ASD Fieldspec® 3 spectroradiometer, the Airborne Spectrographic Imager (CASI) and the MultiSpectral Instrument (MSI) onboard Sentinel-2. We tested the capability of both PROSAIL and PROSAIL+FLIGHT to reproduce the variability of different phenological stages determined by 16-year time series analysis of Moderate Resolution Imaging Spectroradiometer-Normalized Difference Vegetation Index (MODIS-NDVI). Then, we combined concomitant observations of biophysical variables and RF to test the capability of the models to reproduce observed RF. PROSAIL achieved a Relative Root Mean Square Error (RRMSE) between 6% to 32% at proximal sensing scale. PROSAIL+FLIGHT RRMSE ranged between 7% to 31% at remote sensing scales. RRMSE increased in periods when large fractions of standing dead material mixed with emergent green grasses —especially in autumn—; suggesting that the model cannot represent the spectral features of this material. PROSAIL+FLIGHT improves RF simulation especially in summer and at mid-high view angles.
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- 2018
16. Using near-infrared-enabled digital repeat photography to track structural and physiological phenology in Mediterranean tree-grass ecosystems
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Luo, Y., El-Madany, T. S., Filippa, G., Ma, X., Ahrens, B., Carrara, A., González Cascon, María Rosario, Cremonese, E., Galvagno, M., Hammer, T. W., Pacheco-Labrador, J., Martín, M. P., Moreno, G., Perez-Priego, O., Reichstein, M., Richardson, A. D., Römermann, C., Migliavacca, M., Luo, Y., El-Madany, T. S., Filippa, G., Ma, X., Ahrens, B., Carrara, A., González Cascon, María Rosario, Cremonese, E., Galvagno, M., Hammer, T. W., Pacheco-Labrador, J., Martín, M. P., Moreno, G., Perez-Priego, O., Reichstein, M., Richardson, A. D., Römermann, C., and Migliavacca, M.
- Abstract
Tree–grass ecosystems are widely distributed. However, their phenology has not yet been fully characterized. The technique of repeated digital photographs for plant phenology monitoring (hereafter referred as PhenoCam) provide opportunities for long-term monitoring of plant phenology, and extracting phenological transition dates (PTDs, e.g., start of the growing season). Here, we aim to evaluate the utility of near-infrared-enabled PhenoCam for monitoring the phenology of structure (i.e., greenness) and physiology (i.e., gross primary productivity—GPP) at four tree–grass Mediterranean sites. We computed four vegetation indexes (VIs) from PhenoCams: (1) green chromatic coordinates (GCC), (2) normalized difference vegetation index (CamNDVI), (3) near-infrared reflectance of vegetation index (CamNIRv), and (4) ratio vegetation index (CamRVI). GPP is derived from eddy covariance flux tower measurement. Then, we extracted PTDs and their uncertainty from different VIs and GPP. The consistency between structural (VIs) and physiological (GPP) phenology was then evaluated. CamNIRv is best at representing the PTDs of GPP during the Green-up period, while CamNDVI is best during the Dry-down period. Moreover, CamNIRv outperforms the other VIs in tracking growing season length of GPP. In summary, the results show it is promising to track structural and physiology phenology of seasonally dry Mediterranean ecosystem using near-infrared-enabled PhenoCam. We suggest using multiple VIs to better represent the variation of GPP.
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- 2018
17. Estimation of real evapotranspiration (ETR) and potential evapotranspiration (ETP) in the southwest of the Buenos Aires Province (Argentina) using MODIS images
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Melendo-Vega, J., Martín, M., Vilar del Hoyo, L., Pacheco-Labrador, J., Echavarría, P., and Martínez-Vega, J.
- Abstract
Using regression analysis between actual evapotranspiration (ETR) and potential evapotranspiration (ETP) values obtained in seven meteorological observatories and remote sensing derived data from MODIS images (Surface temperature and Normalized Difference Vegetation Index - NDVI) models for estimating ETR and ETP in the southwest of the Buenos Aires Province (Argentina) were developed for the 2000–2014 period. Both models were satisfactorily evaluated in the meteorological observatories used. A regression model was adjusted for ETR with a determination coefficient of 0,6959. Regression model was nonlinear in the case of the ETP variable with a determination coefficient of 0,8409. The individual regression analysis for each meteorological observatories explicate the behavior of the regression for the total data set of ETR and ETP. According to these results, the utility of remote sensing in determination of ETR and ETP in areas without meteorological data was confirmed.
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- 2017
18. Estimating Leaf and Canopy Biochemistry Variables in Mediterranean Holm OAK (Quercus ILEX) from Proximal and Airborne Hyperspectral Data
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Gonzalez-Cascon, R., primary, Pacheco-Labrador, J., additional, Moreno, G., additional, Migliavacca, M., additional, and Martin, M.P., additional
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- 2018
- Full Text
- View/download PDF
19. Spatio-temporal relationships between optical information and carbon fluxes in a mediterranean tree-grass ecosystem
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Pacheco Labrador, J, El Madany, T, Martín, M, Migliavacca, M, Rossini, M, Carrara, A, Zarco Tejada, P, Zarco Tejada, P., ROSSINI, MICOL, Pacheco Labrador, J, El Madany, T, Martín, M, Migliavacca, M, Rossini, M, Carrara, A, Zarco Tejada, P, Zarco Tejada, P., and ROSSINI, MICOL
- Abstract
Spatio-temporal mismatches between Remote Sensing (RS) and Eddy Covariance (EC) data as well as spatial heterogeneity jeopardize terrestrial Gross Primary Production (GPP) modeling. This article combines: (a) high spatial resolution hyperspectral imagery; (b) EC footprint climatology estimates; and (c) semi-empirical models of increasing complexity to analyze the impact of these factors on GPP estimation. Analyses are carried out in a Mediterranean Tree-Grass Ecosystem (TGE) that combines vegetation with very different physiologies and structure. Half-hourly GPP (GPPhh) were predicted with relative errors ~36%. Results suggest that, at EC footprint scale, the ecosystem signals are quite homogeneous, despite tree and grass mixture. Models fit using EC and RS data with high degree of spatial and temporal match did not significantly improved models performance; in fact, errors were explained by meteorological variables instead. In addition, the performance of the different models was quite similar. This suggests that none of the models accurately represented light use efficiency or the fraction of absorbed photosynthetically active radiation. This is partly due to model formulation; however, results also suggest that the mixture of the different vegetation types might contribute to hamper such modeling, and should be accounted for GPP models in TGE and other heterogeneous ecosystems
- Published
- 2017
20. Estimación de variables biofísicas del pastizal en un ecosistema de dehesa a partir de espectro-radiometría de campo e imágenes hiperespectrales aeroportadas
- Author
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Ministerio de Ciencia e Innovación, Ministerio de Economía y Competitividad, Melendo-Vega, J. R., Martín, M. P., Vilar del Hoyo, L., Pacheco-Labrador, J., Echavarría, P., Martínez-Vega, J., Ministerio de Ciencia e Innovación, Ministerio de Economía y Competitividad, Melendo-Vega, J. R., Martín, M. P., Vilar del Hoyo, L., Pacheco-Labrador, J., Echavarría, P., and Martínez-Vega, J.
- Abstract
[EN] The aim of this paper is the estimation of biophysical vegetation parameters from its optical properties. The variables Fuel Moisture Content (FMC), Canopy Water Content (CWC), Leaf Area Index (LAI), dry matter (Cm) and AboveGround Biomass (AGB) were estimated in the laboratory from vegetation samples collected simultaneously with the acquisition of spectral data from the Compact Airborne Spectrographic Imager (CASI) sensor and the field spectroradiometer ASD FieldSpec® 3. Spectral vegetation indices found in the literature were computed from hyperspectral data. Their linear relationships with the biophysical variables measured in the field were analysed. Results show consistent relationships between analysed biophysical parameters and spectral indices, mainly those using SWIR and red-egde bands which reveal the importance of these spectral regions for the estimation of biophysical variables in herbaceous covers. Determination coefficients (R2) above 0.91 and RRMSE of 21.4% have been obtained for the spectral indexes calculated whit ASD data, and 0.91 R2 and RRMSE of 15.5% for the spectral indexes calculated whit CASI data., [ES] Este trabajo aborda la estimación de variables biofísicas de un pastizal de dehesa a partir de información óptica generada por sensores próximos y remotos. Las variables de contenido de humedad del combustible (FMC), contenido de agua del dosel (CWC), índice de área foliar (LAI), materia seca (Cm) y biomasa superficial (AGB) fueron estimadas en laboratorio a partir de muestras de vegetación tomadas simultáneamente a la adquisición de datos hiperespectrales del sensor Compact Airbone Spectrographic Imager (CASI) y del espectro-radiómetro de campo ASD FieldSpec®3. A partir de la información espectral se han calculado diversos índices extraídos de la literatura y se han analizado las relaciones lineales existentes con las variables biofísicas medidas en campo. Los resultados muestran relaciones consistentes entre las variables biofísicas y los índices espectrales, especialmente en el caso de los índices basados en bandas del infrarrojo medio de onda corta (SWIR) y del red-edge, poniendo de manifiesto la importancia de estas regiones en la estimación de variables biofísicas en cubiertas de pastizal. Se han obteniendo coeficientes de determinación (R2) superiores a 0,91 y un error cuadrático medio relativo (RRMSE) de 21,4%, para los índices espectra-les calculados con datos ASD; yR2 de 0,91 y RRMSE de 15,5% para los índices espectrales calculados con datos CASI.
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- 2017
21. Sun induced fluorescence – GPP and ET dynamics in a tree/grass ecosystem
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Martini, D, Pacheco-Labrador, J, El-Madany, T, Julitta, T, Biriukova, K, Sippel, S, Mahecha, M, Migliavacca, M, Martini, D, Pacheco-Labrador, J, El-Madany, T, Julitta, T, Biriukova, K, Sippel, S, Mahecha, M, and Migliavacca, M
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- 2017
22. Plant functional traits and canopy structure control the relationship between photosynthetic CO2 uptake and far-red sun-induced fluorescence in a Mediterranean grassland under different nutrient availability
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Migliavacca, M, Perez Priego, O, Rossini, M, El Madany, T, Moreno, G, van der Tol, C, Rascher, U, Berninger, A, Bessenbacher, V, Burkart, A, Carrara, A, Fava, F, Guan, J, Hammer, T, Henkel, K, Juarez Alcalde, E, Julitta, T, Kolle, O, Martín, M, Musavi, T, Pacheco Labrador, J, Pérez Burgueño, A, Wutzler, T, Zaehle, S, Reichstein, M, Reichstein, M., ROSSINI, MICOL, Migliavacca, M, Perez Priego, O, Rossini, M, El Madany, T, Moreno, G, van der Tol, C, Rascher, U, Berninger, A, Bessenbacher, V, Burkart, A, Carrara, A, Fava, F, Guan, J, Hammer, T, Henkel, K, Juarez Alcalde, E, Julitta, T, Kolle, O, Martín, M, Musavi, T, Pacheco Labrador, J, Pérez Burgueño, A, Wutzler, T, Zaehle, S, Reichstein, M, Reichstein, M., and ROSSINI, MICOL
- Abstract
Sun-induced fluorescence (SIF) in the far-red region provides a new noninvasive measurement approach that has the potential to quantify dynamic changes in light-use efficiency and gross primary production (GPP). However, the mechanistic link between GPP and SIF is not completely understood. We analyzed the structural and functional factors controlling the emission of SIF at 760 nm (F760) in a Mediterranean grassland manipulated with nutrient addition of nitrogen (N), phosphorous (P) or nitrogen–phosphorous (NP). Using the soil–canopy observation of photosynthesis and energy (SCOPE) model, we investigated how nutrient-induced changes in canopy structure (i.e. changes in plant forms abundance that influence leaf inclination distribution function, LIDF) and functional traits (e.g. N content in dry mass of leaves, N%, Chlorophyll a+b concentration (Cab) and maximum carboxylation capacity (Vcmax)) affected the observed linear relationship between F760 and GPP. We conclude that the addition of nutrients imposed a change in the abundance of different plant forms and biochemistry of the canopy that controls F760. Changes in canopy structure mainly control the GPP–F760 relationship, with a secondary effect of Cab and Vcmax. In order to exploit F760 data to model GPP at the global/regional scale, canopy structural variability, biodiversity and functional traits are important factors that have to be considered.
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- 2017
23. Evolution of spectral behavior and chemical composition in the tree canopy of a dehesa ecosystem
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González-Cascón, R., Pacheco-Labrador, J., Martín, M. P., Ministerio de Ciencia e Innovación (España), Ministerio de Economía y Competitividad (España), Martín, M.P [0000-0002-5563-8461], González-Cascón, Rosario [0000-0003-3468-0967], Pacheco-Labrador, Javier [0000-0003-3401-7081], Martín, M.P, González-Cascón, Rosario, and Pacheco-Labrador, Javier
- Subjects
Chlorophyll ,Nutrientes foliares ,lcsh:G1-922 ,Reflectividad de hoja intacta ,Clorofilas1 ,LWC ,Espectro-radiometría de campo ,Intact leaf reflectance ,SLM ,Foliar nutrients ,Quercus ilex ,Clorofila ,Field spectroscopy ,lcsh:Geography (General) - Abstract
[EN] In the context of the BIOSPEC and FLUXPEC projects(http://www.lineas.cchs.csic.es/fluxpec/), spectral and biophysical variables measurements at leaf level have been conducted in the tree canopy of a holm oak dehesa (Quercus ilex) ecosystem during four vegetative periods. Measurements of bi-conical reflectance factor of intact leaf (ASD Fieldspec 3® spectroradiometer), specific leaf mass (SLM), leaf water content (LWC), nutrient (N, P, K, Ca, Mg, Mn, Fe, and Zn) and chlorophyll concentration were performed. The spectral measurements have been related with the biophysical variables by stepwise and partial least squares regression analyses. These analyses allowed to identify the spectral bands and regions that best explain the evolution of the biophysical variables and to estimate the nutrient contents during the leaf maturation process. Statistically significant estimates of the majority of the variables studied were obtained. Wavelengths that had the highest contributions explaining the chemical composition of the forest canopy were located in spectral regions of the red edge, the green visible region, and the shortwave infrared, [ES] : En el contexto de los proyectos BIOSPEC y FLUXPEC (http://www.lineas.cchs.csic.es/fluxpec/), se han realizado mediciones espectrales y de variables biofísicas a nivel de hoja en el dosel arbóreo de una dehesa de encina (Quercus ilex) durante cuatro períodos vegetativos. Se han llevado a cabo mediciones de reflectividad bi-cónica de hoja intacta (ASD Fieldspec 3® spectroradiometer), masa foliar específica (SLM), contenido de agua (LWC), concentraciones de nutrientes (N, P, K, Ca, Mg, Mn, Fe, y Zn) y clorofilas. Las mediciones espectrales se han relacionado con las variables biofísicas mediante análisis de regresión múltiple por pasos (SWR) y regresión de mínimos cuadrados parciales (PLSR). Estos análisis han permitido identificar las bandas y regiones espectrales que explican la evolución de las variables biofísicas y estimar los contenidos de nutrientes a lo largo del proceso de maduración de las hojas en la copa. Se han obtenido modelos estadísticamente significativos para la mayoría de las variables foliares estudiadas. Las longitudes de onda que aportan mayor información sobre la composición química del dosel, se encuentran en las regiones espectrales del límite del rojo, la región verde del visible y el infrarrojo medio de onda corta (SWIR)., Este trabajo ha sido financiado por los proyectos BIOSPEC (CGL2008-02301/CLI, Ministerio de Ciencia e innovación) y FLUXPEC (CGL-2012- 34383, Ministerio de Economía y Competitividad). Agradecemos a los equipos de investigación y trabajo que han participado en ambos proyectos su ayuda durante las campañas de muestreo y las mediciones de campo, así como al personal del Laboratorio de Ecología Forestal del CIFORINIA por su colaboración en los análisis foliares
- Published
- 2016
24. Estimación de variables biofísicas del pastizal en un ecosistema de dehesa a partir de espectro-radiometría de campo e imágenes hiperespectrales aeroportadas
- Author
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Melendo-Vega, J. R., primary, Martín, M. P., additional, Vilar del Hoyo, L., additional, Pacheco-Labrador, J., additional, Echavarría, P., additional, and Martínez-Vega, J., additional
- Published
- 2017
- Full Text
- View/download PDF
25. Evolution of spectral behavior and chemical composition in the tree canopy of a dehesa ecosystem
- Author
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González Cascon, María Rosario, Pacheco-Labrador, J., Martín, M. P., González Cascon, María Rosario, Pacheco-Labrador, J., and Martín, M. P.
- Abstract
In the context of the BIOSPEC and FLUXPEC projects (http//www.lineas.cchs.csic.es/fluxpec/), spectral and biophysical variables measurements at leaf level have been conducted in the tree canopy of a holm oak dehesa (Quercus ilex) ecosystem during four vegetative periods. Measurements of bi-conical reflectance factor of intact leaf (ASD Fieldspec 3® spectroradiometer), specific leaf mass (SLM), leaf water content (LWC), nutrient (N, P, K, Ca, Mg, Mn, Fe, and Zn) and chlorophyll concentration were performed. The spectral measurements have been related with the biophysical variables by stepwise and partial least squares regression analyses. These analyses allowed to identify the spectral bands and regions that best explain the evolution of the biophysical variables and to estimate the nutrient contents during the leaf maturation process. Statistically significant estimates of the majority of the variables studied were obtained. Wavelengths that had the highest contributions explaining the chemical composition of the forest canopy were located in spectral regions of the red edge, the green visible region, and the shortwave infrared.
- Published
- 2016
26. Evolution of spectral behavior and chemical composition in the tree canopy of a dehesa ecosystem
- Author
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Ministerio de Ciencia e Innovación, Ministerio de Economía y Competitividad, González-Cascón, R., Pacheco-Labrador, J., Martín, M. P., Ministerio de Ciencia e Innovación, Ministerio de Economía y Competitividad, González-Cascón, R., Pacheco-Labrador, J., and Martín, M. P.
- Abstract
Revista oficial de la Asociación Española de Teledetección, [EN] In the context of the BIOSPEC and FLUXPEC projects (http://www.lineas.cchs.csic.es/fluxpec/), spectral and biophysical variables measurements at leaf level have been conducted in the tree canopy of a holm oak dehesa (Quercus ilex) ecosystem during four vegetative periods. Measurements of bi-conical reflectance factor of intact leaf (ASD Fieldspec 3® spectroradiometer), specific leaf mass (SLM), leaf water content (LWC), nutrient (N, P, K, Ca, Mg, Mn, Fe, and Zn) and chlorophyll concentration were performed. The spectral measurements have been related with the biophysical variables by stepwise and partial least squares regression analyses. These analyses allowed to identify the spectral bands and regions that best explain the evolution of the biophysical variables and to estimate the nutrient contents during the leaf maturation process. Statistically significant estimates of the majority of the variables studied were obtained. Wavelengths that had the highest contributions explaining the chemical composition of the forest canopy were located in spectral regions of the red edge, the green visible region, and the shortwave infrared., [ES] En el contexto de los proyectos BIOSPEC y FLUXPEC (http://www.lineas.cchs.csic.es/fluxpec/), se han rea-lizado mediciones espectrales y de variables biofísicas a nivel de hoja en el dosel arbóreo de una dehesa de encina (Quercus ilex) durante cuatro períodos vegetativos. Se han llevado a cabo mediciones de reflectividad bi-cónica de hoja intacta (ASD Fieldspec 3®spectroradiometer), masa foliar específica (SLM), contenido de agua (LWC), concen-traciones de nutrientes (N, P, K, Ca, Mg, Mn, Fe, y Zn) y clorofilas. Las mediciones espectrales se han relacionado con las variables biofísicas mediante análisis de regresión múltiple por pasos (SWR) y regresión de mínimos cuadrados parciales (PLSR). Estos análisis han permitido identificar las bandas y regiones espectrales que explican la evolución de las variables biofísicas y estimar los contenidos de nutrientes a lo largo del proceso de maduración de las hojas en la copa. Se han obtenido modelos estadísticamente significativos para la mayoría de las variables foliares estudiadas. Las longitudes de onda que aportan mayor información sobre la composición química del dosel, se encuentran en las regiones espectrales del límite del rojo, la región verde del visible y el infrarrojo medio de onda corta (SWIR).
- Published
- 2016
27. Evolución del comportamiento espectral y la composición química en el dosel arbóreo de una dehesa
- Author
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González-Cascón, R., primary, Pacheco-Labrador, J., additional, and Martín, M. P., additional
- Published
- 2016
- Full Text
- View/download PDF
28. ISAAC : A REXUS STUDENT EXPERIMENT TO DEMONSTRATE AN EJECTION SYSTEM WITH PREDEFINED DIRECTION
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Balmer, G., Berquand, A., Company-Vallet, E., Granberg, V., Grigore, V., Ivchenko, Nickolay, Kevorkov, R., Lundkvist, E., Olentsenko, Georgi, Pacheco-Labrador, J., Tibert, Gunnar, Yuan, Yunxia, Balmer, G., Berquand, A., Company-Vallet, E., Granberg, V., Grigore, V., Ivchenko, Nickolay, Kevorkov, R., Lundkvist, E., Olentsenko, Georgi, Pacheco-Labrador, J., Tibert, Gunnar, and Yuan, Yunxia
- Abstract
ISAAC - Infrared Spectroscopy to Analyse the middle Atmosphere Composition was a student experiment launched from SSC's Esrange Space Centre, Sweden, on 29th May 2014, on board the sounding rocket REXUS 15 in the frame of the REXUS/BEXUS programme. The main focus of the experiment was to implement an ejection system for two large Free Falling Units (FFUs) (240 mm x 80 mm) to be ejected from a spinning rocket into a predefined direction. The system design relied on a spring-based ejection system. Sun and angular rate sensors were used to control and time the ejection. The flight data includes telemetry from the Rocket Mounted Unit (RMU), received and saved during flight, as well as video footage from the GoPro camera mounted inside the RMU and recovered after the flight. The FFUs' direction, speed and spin frequency as well as the rocket spin frequency were determined by analyzing the video footage. The FFU-Rocket-Sun angles were 64.3 degrees and 104.3 degrees, within the required margins of 90 degrees +/- 45 degrees. The FFU speeds were 3.98 m/s and 3.74 m/s, lower than the expected 5 +/- 1 m/s. The FFUs' spin frequencies were 1.38 Hz and 1.60 Hz, approximately half the rocket's spin frequency. The rocket spin rate slightly changed from 3.163 Hz before the ejection to 3.117 Hz after the ejection of the two FFUs. The angular rate, sun sensor data and temperature on the inside of the rocket module skin were also recorded. The experiment design and results of the data analysis are presented in this paper., QC 20160608
- Published
- 2015
29. EUROSPEC: At the interface between remote-sensing and ecosystem CO2 flux measurements in Europe
- Author
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Porcar Castell, A, Mac Arthur, A, Rossini, M, Eklundh, L, Pacheco Labrador, J, Anderson, K, Balzarolo, M, Martín, M, Jin, H, Tomelleri, E, Cerasoli, S, Sakowska, K, Hueni, A, Julitta, T, Nichol, C, Vescovo, L, Vescovo, L., ROSSINI, MICOL, JULITTA, TOMMASO, Porcar Castell, A, Mac Arthur, A, Rossini, M, Eklundh, L, Pacheco Labrador, J, Anderson, K, Balzarolo, M, Martín, M, Jin, H, Tomelleri, E, Cerasoli, S, Sakowska, K, Hueni, A, Julitta, T, Nichol, C, Vescovo, L, Vescovo, L., ROSSINI, MICOL, and JULITTA, TOMMASO
- Abstract
Resolving the spatial and temporal dynamics of gross primary productivity (GPP) of terrestrial ecosystems across different scales remains a challenge. Remote sensing is regarded as the solution to upscale point observations conducted at the ecosystem level, using the eddy covariance (EC) technique, to the landscape and global levels. In addition to traditional vegetation indices, the photochemical reflectance index (PRI) and the emission of solar-induced chlorophyll fluorescence (SIF), now measurable from space, provide a new range of opportunities to monitor the global carbon cycle using remote sensing. However, the scale mismatch between EC observations and the much coarser satellite-derived data complicate the integration of the two sources of data. The solution is to establish a network of in situ spectral measurements that can act as a bridge between EC measurements and remote-sensing data. In situ spectral measurements have already been conducted for many years at EC sites, but using variable instrumentation, setups, and measurement standards. In Europe in particular, in situ spectral measurements remain highly heterogeneous. The goal of EUROSPEC Cost Action ES0930 was to promote the development of common measuring protocols and new instruments towards establishing best practices and standardization of these measurements. In this review we describe the background and main tradeoffs of in situ spectral measurements, review the main results of EUROSPEC Cost Action, and discuss the future challenges and opportunities of in situ spectral measurements for improved estimation of local and global estimates of GPP over terrestrial ecosystems.
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- 2015
30. EUROSPEC: at the interface between remote-sensing and ecosystem CO2 flux measurements in Europe
- Author
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Porcar-Castell, A., Mac Arthur, A., Rossini, M., Eklundh, Lars, Pacheco-Labrador, J., Anderson, K., Balzarolo, M., Martín, M.P., Jin, Hongxiao, Tomelleri, E., Cerasoli, S., Sakowska, K., Hueni, A., Julitta, T., Nichol, C. J., Vescovo, L., Porcar-Castell, A., Mac Arthur, A., Rossini, M., Eklundh, Lars, Pacheco-Labrador, J., Anderson, K., Balzarolo, M., Martín, M.P., Jin, Hongxiao, Tomelleri, E., Cerasoli, S., Sakowska, K., Hueni, A., Julitta, T., Nichol, C. J., and Vescovo, L.
- Abstract
Resolving the spatial and temporal dynamics of gross primary productivity (GPP) of terrestrial ecosystems across different scales remains a challenge. Remote sensing is regarded as the solution to upscale point observations conducted at the ecosystem level, using the eddy covariance (EC) technique, to the landscape and global levels. In addition to traditional vegetation indices, the photochemical reflectance index (PRI) and the emission of solar-induced chlorophyll fluorescence (SIF), now measurable from space, provide a new range of opportunities to monitor the global carbon cycle using remote sensing. However, the scale mismatch between EC observations and the much coarser satellite-derived data complicates the integration of the two sources of data. The solution is to establish a network of in situ spectral measurements that can act as bridge between EC measurements and remote sensing data. In situ spectral measurements have been already conducted for many years at EC sites, but using variable instrumentation, setups, and measurement standards. In Europe in particular, in situ spectral measurements remain highly heterogeneous. The goal of EUROSPEC Cost Action ES0930 was to promote the development of common measuring protocols and new instruments towards establishing best practices and standardization of in situ spectral measurements. In this review we describe the background and main tradeoffs of in situ spectral measurements, review the main results of EUROSPEC Cost Action, and discuss the future challenges and opportunities of in situ spectral measurements for improved estimation of local and global carbon cycle.
- Published
- 2015
31. Seasonal variation in grass water content estimated from proximal sensing and MODIS time series in a Mediterranean Fluxnet site
- Author
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Mendiguren, G., Pilar Martin, M., Nieto Solana, Hector, Pacheco-Labrador, J., Jurdao, S., Mendiguren, G., Pilar Martin, M., Nieto Solana, Hector, Pacheco-Labrador, J., and Jurdao, S.
- Published
- 2015
32. EUROSPEC: at the interface between remote-sensing and ecosystem CO<sub>2</sub> flux measurements in Europe
- Author
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Porcar-Castell, A., primary, Mac Arthur, A., additional, Rossini, M., additional, Eklundh, L., additional, Pacheco-Labrador, J., additional, Anderson, K., additional, Balzarolo, M., additional, Martín, M. P., additional, Jin, H., additional, Tomelleri, E., additional, Cerasoli, S., additional, Sakowska, K., additional, Hueni, A., additional, Julitta, T., additional, Nichol, C. J., additional, and Vescovo, L., additional
- Published
- 2015
- Full Text
- View/download PDF
33. Seasonal variation in grass water content estimated from proximal sensing and MODIS time series in a Mediterranean Fluxnet site
- Author
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Mendiguren, G., primary, Pilar Martín, M., additional, Nieto, H., additional, Pacheco-Labrador, J., additional, and Jurdao, S., additional
- Published
- 2015
- Full Text
- View/download PDF
34. Seasonal variation in vegetation water content estimated from proximal sensing and MODIS time series in a Mediterranean Fluxnet site
- Author
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Mendiguren, G., primary, Martín, M. P., additional, Nieto, H., additional, Pacheco-Labrador, J., additional, and Jurdao, S., additional
- Published
- 2015
- Full Text
- View/download PDF
35. Understanding the optical responses of leaf nitrogen in Mediterranean Holm oak (Quercus ilex) using field spectroscopy
- Author
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Pacheco-Labrador, J., González Cascon, María Rosario, Martín, M. P., Riaño, D., Pacheco-Labrador, J., González Cascon, María Rosario, Martín, M. P., and Riaño, D.
- Abstract
The direct estimation of nitrogen (N) in fresh vegetation is challenging due to its weak influence on leaf reflectance and the overlaps with absorption features of other compounds. Different empirical modelsrelate in this work leaf nitrogen concentration ([N]Leaf) on Holm oak to leaf reflectance as well as derivedspectral indices such as normalized difference indices (NDIs), the three bands indices (TBIs) and indices previously used to predict leaf N and chlorophyll. The models were calibrated and assessed their accuracy, robustness and the strength of relationship when other biochemicals were considered. Red edge was the spectral region most strongly correlated with [N]Leaf, whereas most of the published spectral indexesdid not provide accurate estimations. NDIs and TBIs based models could achieve robust and acceptableaccuracies (TBI1310,1720,730 R2= 0.76, [0.64,0.86]; RMSE (%) = 9.36, [7.04,12.83]). These models sometimesincluded indices with bands close to absorption features of N bonds or nitrogenous compounds, but also of other biochemicals. Models were independently and inter-annually validated using the bootstrap method, which allowed discarding those models non-robust across different years. Partial correlationanalysis revealed that spectral estimators did not strongly respond to [N]Leaf but to other leaf variablessuch as chlorophyll and water, even if bands close to absorption features of N bonds or compounds werepresent in the models. © 2013 Elsevier B.V.
- Published
- 2014
36. Inter-comparison of hemispherical conical reflectance factors (HCRF) measured with four fibre-based spectrometers
- Author
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Anderson, K, Rossini, M, Pacheco Labrador, J, Balzarolo, M, Mac Arthur, A, Fava, F, Julitta, T, Vescovo, L, ROSSINI, MICOL, FAVA, FRANCESCO PIETRO, JULITTA, TOMMASO, Vescovo, L., Anderson, K, Rossini, M, Pacheco Labrador, J, Balzarolo, M, Mac Arthur, A, Fava, F, Julitta, T, Vescovo, L, ROSSINI, MICOL, FAVA, FRANCESCO PIETRO, JULITTA, TOMMASO, and Vescovo, L.
- Abstract
We describe the results of an experiment designed to compare the radiometric performance of four different spectroradiometers in ideal field conditions. A carefully designed experiment where instruments were simultaneously triggered was used to measure the Hemispherical Conical Reflectance Factors (HCRF) of four targets of varying reflectance. The experiment was in two parts. Stage 1 covered a 2 hour period finishing at solar noon, where 50 measurements of the targets were collected in sequence. Stage 2 comprised 10 rapid sequential measurements over each target. We applied a method for normalising full width half maximum (FWHM) differences between the instruments, which was a source of variability in the raw data. The work allowed us to determine data reproducibility, and we found that lower-cost instruments (Ocean Optics and PP Systems) produced data of similar radiometric quality to those manufactured by Analytical Spectral Devices (ASD –here we used the ASD FieldSpec Pro) in the spectral range 400-850 nm, which is the most significant region for research communities interested in measuring vegetation dynamics. Over the longer time-series there were changes in HCRF caused by the structural and spectral characteristics of some targets.
- Published
- 2013
37. Inter-comparison of hemispherical conical reflectance factors (HCRF) measured with four fibre-based spectrometers
- Author
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Anderson, K., primary, Rossini, M., additional, Pacheco-Labrador, J., additional, Balzarolo, M., additional, Mac Arthur, A., additional, Fava, F., additional, Julitta, T., additional, and Vescovo, L., additional
- Published
- 2013
- Full Text
- View/download PDF
38. EUROSPEC: at the interface between remote-sensing and ecosystem CO2 flux measurements in Europe.
- Author
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Porcar-Castell, A., Mac Arthur, A., Rossini, M., Eklundh, L., Pacheco-Labrador, J., Anderson, K., Balzarolo, M., Martín, M. P., Jin, H., Tomelleri, E., Cerasoli, S., Sakowska, K., Hueni, A., Julitta, T., Nichol, C. J., and Vescovo, L.
- Subjects
PHOTOCHEMISTRY ,CHLOROPHYLL spectra ,VEGETATION & climate ,CARBON cycle ,PRIMARY productivity (Biology) ,CARBON dioxide & the environment ,REMOTE sensing - Abstract
Resolving the spatial and temporal dynamics of gross primary productivity (GPP) of terrestrial ecosystems across different scales remains a challenge. Remote sensing is regarded as the solution to upscale point observations conducted at the ecosystem level, using the eddy covariance (EC) technique, to the landscape and global levels. In addition to traditional vegetation indices, the photochemical reflectance index (PRI) and the emission of solarinduced chlorophyll fluorescence (SIF), now measurable from space, provide a new range of opportunities to monitor the global carbon cycle using remote sensing. However, the scale mismatch between EC observations and the much coarser satellite-derived data complicate the integration of the two sources of data. The solution is to establish a network of in situ spectral measurements that can act as a bridge between EC measurements and remote-sensing data. In situ spectral measurements have already been conducted for many years at EC sites, but using variable instrumentation, setups, and measurement standards. In Europe in particular, in situ spectral measurements remain highly heterogeneous. The goal of EUROSPEC Cost Action ES0930 was to promote the development of common measuring protocols and new instruments towards establishing best practices and standardization of these measurements. In this review we describe the background and main tradeoffs of in situ spectral measurements, review the main results of EUROSPEC Cost Action, and discuss the future challenges and opportunities of in situ spectral measurements for improved estimation of local and global estimates of GPP over terrestrial ecosystems. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
39. Seasonal variation in vegetation water content estimated from proximal sensing and MODIS time series in a Mediterranean Fluxnet site.
- Author
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Mendiguren, G., Martín, M. P., Nieto, H., Pacheco-Labrador, J., and Jurdao, S.
- Subjects
VEGETATION & climate ,PLANT water requirements ,ESTIMATION theory ,CLIMATE change ,MODIS (Spectroradiometer) - Abstract
This study evaluates three different metrics of vegetation water content estimated from proximal sensing and MODIS satellite imagery: Fuel Moisture Content (FMC), Equivalent Water Thickness (EWT) and Canopy Water Content (CWC). Dry matter (Dm) and Leaf area Index (LAI) were also analyzed in order to connect FMC with EWT and EWT with CWC, respectively. This research took place in a Fluxnet site located in Mediterranean wooded grassland (dehesa) ecosystem in Las Majadas del Tietar (Spain). Results indicated that FMC and EWT showed lower spatial variation than CWC. The spatial variation within the MODIS pixel was not as critical as its temporal trend, so to capture better the variability, fewer plots should be sampled but more times. Due to the high seasonal Dm variability, a constant annual value would not work to predict EWT from FMC. Relative root mean square error (RRMSE) evaluated the performance of nine spectral indices to compute each variable. VARI provided the worst results in all cases. For proximal sensing, GEMI worked best for both FMC (RRMSE = 34.5 %) and EWT (RRMSE = 27.43 %) while NDII and GVMI performed best for CWC (RRMSE = 30.27% and 31.58% respectively). For MODIS data, results were a bit better with EVI as the best predictor for FMC (RRMSE = 33.81 %) and CWC (RRMSE = 27.56 %) and GEMI for EWT (RRMSE = 24.6 %). To explain these differences, proximal sensing measures only grasslands at nadir view angle, but MODIS includes also trees, their shades, and other artifacts at up to 20_ view angle. CWC was better predicted than the other two water content variables, probably because CWC depends on LAI, which is highly correlated to the spectral indices. Finally, these empirical methods outperformed FMC and CWC products based on radiative transfer model inversion. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
40. Global modeling diurnal gross primary production from OCO-3 solar-induced chlorophyll fluorescence
- Author
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Zhaoying Zhang, Luis Guanter, Albert Porcar-Castell, Micol Rossini, Javier Pacheco-Labrador, Yongguang Zhang, Zhang, Z, Guanter, L, Porcar-Castell, A, Rossini, M, Pacheco-Labrador, J, and Zhang, Y
- Subjects
Diurnal GPP ,GEO/04 - GEOGRAFIA FISICA E GEOMORFOLOGIA ,Hysteresi ,Soil Science ,Geology ,Computers in Earth Sciences ,ANN ,OCO-3 SIF ,SIFtotal - Abstract
Photosynthesis plays a crucial role in regulating the global carbon cycle and mitigating climate change. The diurnal variation in photosynthesis provides key information on the responses of ecosystems to environmental drivers, but there is a critical gap in the large-scale estimation of diurnal photosynthesis. In the last decade, satellite estimates of solar-induced chlorophyll fluorescence (SIF) have been found to mimic the seasonality of photosynthesis. Recently, the deployment of the Orbiting Carbon Observatory-3 (OCO-3) on the International Space Station has provided the opportunity to retrieve SIF at different times of the day. Here we utilized OCO-3 measurements to estimate and analyze diurnal cycles of SIF and gross primary production (GPP) at the global scale. We first mitigated the sun-sensor geometry effects on nadir-mode OCO-3 SIF (SIFnadir) at the sub-diurnal scale (hourly) by deriving the total canopy SIF emission (SIFtotal) using radiative transfer theory. Next, we generated the spatially and temporally continuous hourly SIFnadir and SIFtotal using artificial neural networks under clear-sky conditions, whose extrapolation ability was evaluated using the data from independent years. Compared with SIFnadir, the diurnal relationship between clear-sky SIFtotal and GPP from 38 homogeneous flux sites had smaller variations in the slope (the coefficient of variation was 0.07 vs 0.19). In addition, a correction to account for the bias between clear-sky and overcast conditions was used to estimate all-sky GPP from clear-sky SIFtotal and the resulting GPP was strongly correlated with tower GPP (R2 = 0.75; RMSE = 3.53 μmol/m2/s). Our results demonstrated that the new OCO-3 SIF trained GPP product (GPPSIF) was able to depict the diurnal pattern of photosynthesis globally, capturing also the physiologically hysteresis or afternoon depression of photosynthesis. By doing so, hourly GPPSIF has the potential to improve the modeling of terrestrial photosynthesis and the projection of the global carbon cycle under climate change.
- Published
- 2023
41. Heatwave breaks down the linearity between sun-induced fluorescence and gross primary production
- Author
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David Martini, Karolina Sakowska, Georg Wohlfahrt, Javier Pacheco‐Labrador, Christiaan van der Tol, Albert Porcar‐Castell, Troy S. Magney, Arnaud Carrara, Roberto Colombo, Tarek S. El‐Madany, Rosario Gonzalez‐Cascon, María Pilar Martín, Tommaso Julitta, Gerardo Moreno, Uwe Rascher, Markus Reichstein, Micol Rossini, Mirco Migliavacca, Department of Water Resources, Faculty of Geo-Information Science and Earth Observation, UT-I-ITC-WCC, Martini, D, Sakowska, K, Wohlfahrt, G, Pacheco-Labrador, J, van der Tol, C, Porcar-Castell, A, Magney, T, Carrara, A, Colombo, R, El-Madany, T, Gonzalez-Cascon, R, Martin, M, Julitta, T, Moreno, G, Rascher, U, Reichstein, M, Rossini, M, Migliavacca, M, Viikki Plant Science Centre (ViPS), Department of Forest Sciences, Ecosystem processes (INAR Forest Sciences), Forest Ecology and Management, and Institute for Atmospheric and Earth System Research (INAR)
- Subjects
0106 biological sciences ,Chlorophyll ,extreme events ,010504 meteorology & atmospheric sciences ,Physiology ,sun-induced fluorescence ,Plant Science ,01 natural sciences ,Fluorescence ,photosynthesi ,heatwave ,Photosynthesis ,extreme event ,Ecosystem ,0105 earth and related environmental sciences ,4112 Forestry ,gross primary production (GPP) ,15. Life on land ,nonphotochemical quenching ,ddc:580 ,13. Climate action ,ITC-ISI-JOURNAL-ARTICLE ,1181 Ecology, evolutionary biology ,Seasons ,010606 plant biology & botany ,Environmental Monitoring - Abstract
Sun-induced fluorescence in the far-red region (SIF) is increasingly used as a remote and proximal-sensing tool capable of tracking vegetation gross primary production (GPP). However, the use of SIF to probe changes in GPP is challenged during extreme climatic events, such as heatwaves. Here, we examined how the 2018 European heatwave (HW) affected the GPP-SIF relationship in evergreen broadleaved trees with a relatively invariant canopy structure. To do so, we combined canopy-scale SIF measurements, GPP estimated from an eddy covariance tower, and active pulse amplitude modulation fluorescence. The HW caused an inversion of the photosynthesis-fluorescence relationship at both the canopy and leaf scales. The highly nonlinear relationship was strongly shaped by nonphotochemical quenching (NPQ), that is, a dissipation mechanism to protect from the adverse effects of high light intensity. During the extreme heat stress, plants experienced a saturation of NPQ, causing a change in the allocation of energy dissipation pathways towards SIF. Our results show the complex modulation of the NPQ-SIF-GPP relationship at an extreme level of heat stress, which is not completely represented in state-of-the-art coupled radiative transfer and photosynthesis models.
- Published
- 2021
42. Performance of Singular Spectrum Analysis in Separating Seasonal and Fast Physiological Dynamics of Solar-Induced Chlorophyll Fluorescence and PRI Optical Signals
- Author
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Miguel D. Mahecha, Khelvi Biriukova, Rosario Gonzalez-Cascon, Javier Pacheco-Labrador, Micol Rossini, Mirco Migliavacca, M. Pilar Martín, Biriukova, K, Pacheco-Labrador, J, Migliavacca, M, Mahecha, M, Gonzalez-Cascon, R, Martin, M, and Rossini, M
- Subjects
0106 biological sciences ,Atmospheric Science ,Time series ,010504 meteorology & atmospheric sciences ,Ecology ,Dynamics (mechanics) ,Paleontology ,Soil Science ,Forestry ,solar-induced chlorophyll fluorescence ,Aquatic Science ,singular spectrum analysi ,Photochemical Reflectance Index ,01 natural sciences ,photochemical reflectance index ,SCOPE ,Environmental science ,time serie ,Biological system ,Chlorophyll fluorescence ,Singular spectrum analysis ,010606 plant biology & botany ,0105 earth and related environmental sciences ,Water Science and Technology - Abstract
High temporal resolution measurements of solar-induced chlorophyll fluorescence (F) and the Photochemical Reflectance Index (PRI) encode vegetation functioning. However, these signals are modulated by time-dependent processes. We tested the applicability of the Singular Spectrum Analysis (SSA) for disentangling fast components (physiology-driven) and slow components (controlled by structural and biochemical properties) from PRI, far-red F (F760), and far-red apparent fluorescence yield (Fy∗760). The proof of concept was developed on spectral and flux time series simulated with the Soil Canopy Observation of Photochemistry and Energy fluxes (SCOPE) model. This allowed the evaluation of SSA decomposition against variables that are independent of physiology or are modified by it. Slow SSA-decomposed components of PRI and Fy∗760 showed high correlations with the reference variables (R2=0.97 and 0.96, respectively). Fast SSA-decomposed components of PRI and Fy∗760 were better related to the physiological reference variables than the original signals during periods when leaf area index (LAI) was above 1m2m−2. The method was also successfully applied to predict light-use efficiency (LUE) from the fast SSA-decomposed components of PRI (R2=0.70) and Fy∗760 (R2=0.68) when discarding data modeled with LAI 
- Published
- 2021
43. Effects of varying solar-view geometry and canopy structure on solar-induced chlorophyll fluorescence and PRI
- Author
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Marco Celesti, Khelvi Biriukova, Tommaso Julitta, Claudia Giardino, Anton Evdokimov, Javier Pacheco-Labrador, Roberto Colombo, Micol Rossini, Franco Miglietta, Cinzia Panigada, Mirco Migliavacca, Biriukova, K, Celesti, M, Evdokimov, A, Pacheco-Labrador, J, Julitta, T, Migliavacca, M, Giardino, C, Miglietta, F, Colombo, R, Panigada, C, and Rossini, M
- Subjects
Canopy ,010504 meteorology & atmospheric sciences ,Forward scatter ,Solar-induced chlorophyll fluorescence ,0211 other engineering and technologies ,Eddy covariance ,Geometry ,02 engineering and technology ,Management, Monitoring, Policy and Law ,Photochemical Reflectance Index ,01 natural sciences ,Multi-angular ,SCOPE ,Radiative transfer ,Computers in Earth Sciences ,Leaf area index ,021101 geological & geomatics engineering ,0105 earth and related environmental sciences ,Earth-Surface Processes ,Global and Planetary Change ,BRDF ,Hyperspectral ,Radiance ,Environmental science ,Bidirectional reflectance distribution function ,PRI - Abstract
The increasing amount of continuous time series of solar-induced fluorescence (SIF) and vegetation indices (e.g. Photochemical Reflectance Index, PRI) acquired with high temporal (sub-minute) frequencies is foreseen to allow tracking of the structural and physiological changes of vegetation in a variety of ecosystems. Coupled with observations of CO2, water, and energy fluxes from eddy covariance flux towers, these measurements can bring new insights into the remote monitoring of ecosystem functioning. However, continuously changing solar-view geometry imposes directional effects on diurnal cycles of the fluorescence radiance in the observation direction (F) and PRI, controlled by structural and biochemical vegetation properties. An improved understanding of these variations can potentially help to disentangle directional responses of vegetation from physiological ones in the continuous long-term optical measurements and, therefore, allow to deconvolve the physiological information relevant to ecosystem functioning. Moreover, this will also be useful for better interpreting and validating F and PRI satellite products (e.g., from the upcoming ESA FLEX mission). Many previous studies focused on the characterization of reflectance directionality, but only a handful of studies investigated directional effects on F and vegetation indices related to plant physiology. The aim of this study is to contribute to the understanding of red (F687) and far-red (F760) fluorescence and PRI anisotropy based on field spectroscopy data and simulations with the Soil-Canopy Observation of Photochemistry and Energy fluxes (SCOPE) model. We present an extensive dataset of multi-angular measurements of F and PRI collected at canopy level with a high-resolution instrument (FloX, JB Hyperspectral Devices UG, Germany) over different ecosystems: Mediterranean grassland, alfalfa, chickpea and rice. We found, that F760 and F687 directional responses of horizontally homogeneous canopies are characterized by higher values in the backscatter direction with a maximum in the hotspot and lower values in the forward scatter direction. The PRI exhibited similar response due to its sensitivity to sunlit-shaded canopy fractions. As confirmed by radiative transfer forward simulations, we show that in the field measurements leaf inclination distribution function controls the shape of F and PRI anisotropic response (bowl-like/dome-like shapes), while leaf area index and the ratio of leaf width to canopy height affect the magnitude and the width of the hotspot. Finally, we discuss the implications of off-nadir viewing geometry for continuous ground measurements. F observations under oblique viewing angles showed up to 67 % difference compared to nadir observations, therefore, we suggest maintaining nadir viewing geometry for continuous measurements of F and vegetation indices. Alternatively, a correction scheme should be developed and tested against multi-angular measurements to properly account for anisotropy of canopy F and PRI observations. The quantitative characterization of these effects in varying illumination geometries for different canopies that was performed in this study will also be useful for the validation of remote sensing F and PRI products at different spatial and temporal scales.
- Published
- 2020
44. Multiple-constraint inversion of SCOPE. Evaluating the potential of GPP and SIF for the retrieval of plant functional traits
- Author
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Jin-Hong Guan, Tommaso Julitta, Markus Reischtein, Tiana W. Hammer, Gerardo Moreno, Rosario Gonzalez-Cascon, Nuno Carvalhais, David Martini, Tarek S. El-Madany, M. Pilar Martín, Olaf Kolle, Oscar Perez-Priego, Javier Pacheco-Labrador, Micol Rossini, Mirco Migliavacca, Arnaud Carrara, Christiaan van der Tol, Heiko Moossen, Ministerio de Ciencia, Innovación y Universidades (España), Ministerio de Economía y Competitividad (España), European Commission, González-Cascón, Rosario, Pacheco-Labrador, Javier, Carrara, Arnaud, Martín, M. Pilar, Pérez Priego, Oscar, González-Cascón, Rosario [0000-0003-3468-0967], Pacheco-Labrador, Javier [0000-0003-3401-7081], Carrara, Arnaud [0000-0002-9095-8807], Martín, M. Pilar [0000-0002-5563-8461], Pérez Priego, Oscar [0000-0002-3138-3177], Department of Water Resources, Faculty of Geo-Information Science and Earth Observation, UT-I-ITC-WCC, Pacheco-Labrador, J, Perez-Priego, O, El-Madany, T, Julitta, T, Rossini, M, Guan, J, Moreno, G, Carvalhais, N, Martin, M, Gonzalez-Cascon, R, Kolle, O, Reischtein, M, van der Tol, C, Carrara, A, Martini, D, Hammer, T, Moossen, H, and Migliavacca, M
- Subjects
010504 meteorology & atmospheric sciences ,0208 environmental biotechnology ,Eddy covariance ,Soil Science ,Inverse transform sampling ,02 engineering and technology ,01 natural sciences ,ITC-HYBRID ,SCOPE inversion ,Thermal ,Radiative transfer ,Plant functional traits ,Computers in Earth Sciences ,Leaf area index ,0105 earth and related environmental sciences ,Remote sensing ,2. Zero hunger ,SIF ,Primary production ,Hyperspectral imaging ,Geology ,Inversion (meteorology) ,15. Life on land ,Mediterranean grassland ,020801 environmental engineering ,Hyperspectral ,13. Climate action ,ITC-ISI-JOURNAL-ARTICLE ,Radiance ,Environmental science ,Nutrient availability ,Plant functional trait ,GPP - Abstract
The most recent efforts to provide remote sensing (RS) estimates of plant function rely on the combination of Radiative Transfer Models (RTM) and Soil-Vegetation-Atmosphere Transfer (SVAT) models, such as the SoilCanopy Observation Photosynthesis and Energy fluxes (SCOPE) model. In this work we used ground spectroradiometric and chamber-based CO2 flux measurements in a nutrient manipulated Mediterranean grassland in order to: 1) develop a multiple-constraint inversion approach of SCOPE able to retrieve vegetation biochemical, structural as well as key functional traits, such as chlorophyll concentration (Cab), leaf area index (LAI), maximum carboxylation rate (Vcmax) and the Ball-Berry sensitivity parameter (m); and 2) compare the potential of the of gross primary production (GPP) and sun-induced fluorescence (SIF), together with up-welling Thermal Infrared (TIR) radiance and optical reflectance factors (RF), to estimate such parameters. The performance of the proposed inversion method as well as of the different sets of constraints was assessed with contemporary measurements of water and heat fluxes and leaf nitrogen content, using pattern-oriented model evaluation. The multiple-constraint inversion approach proposed together with the combination of optical RF and diel GPP and TIR data provided reliable estimates of parameters, and improved predicted water and heat fluxes. The addition of SIF to this scheme slightly improved the estimation of m. Parameter estimates were coherent with the variability imposed by the fertilization and the seasonality of the grassland. Results revealed that fertilization had an impact on Vcmax, while no significant differences were found for m. The combination of RF, SIF and diel TIR data weakly constrained functional traits. Approaches not including GPP failed to estimate LAI; however GPP overestimated Cab in the dry period. These problems might be related to the presence of high fractions of senescent leaves in the grassland. The proposed inversion approach together with pattern-oriented model evaluation open new perspectives for the retrieval of plant functional traits relevant for land surface models, and can be utilized at various research sites where hyperspectral remote sensing imagery and eddy covariance flux measurements are simultaneously taken, JPL, MM, and MR acknowledge the EnMAP project MoReDEHESHyReS “Modelling Responses of Dehesas with Hyperspectral Remote Sensing” (Contract No. 50EE1621, German Aerospace Center (DLR) and the German Federal Ministry of Economic Affairs and Energy). DM, MM and MR received funding from the European Union’s Horizon 2020 research and innovation programme via the TRUSTEE project under the Marie Skłodowska-Curie grant agreement No. 721995. Authors acknowledge the Alexander von Humboldt Foundation for supporting this research with the Max-Planck Prize to Markus Reichstein; SynerTGE “Landsat-8 + Sentinel-2: exploring sensor synergies for monitoring and modelling key vegetation biophysical variables in tree-grass ecosystems” (CGL2015-69095-R, Spanish Ministry of Science, Innovation and Universities); and FLUχPEC “Monitoring changes in water and carbon fluxes from remote and proximal sensing in Mediterranean ‘dehesa’ ecosystem” (CGL2012- 34383, Spanish Ministry of Economy and Competitiveness). Authors are very thankful to Dr. Karl Segl and Prof. Dr. Luis Guanter for their support with the EnMAP end-to-end simulator; as well as the MPI-BGC Freiland Group and especially Martin Hertel as well as Ramón LópezJiménez (CEAM) for technical assistance. We are grateful to all the colleagues from MPI-BGC, University of Extremadura, University of Milano-Bicocca, SpecLab-CSIC, INIA and CEAM which have collaborated in any of the field and laboratory works. We acknowledge the Majadas de Tiétar city council for its support.
- Published
- 2019
45. Nitrogen and Phosphorus Effect on Sun-Induced Fluorescence and Gross Primary Productivity in Mediterranean Grassland
- Author
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Tommaso Julitta, C. van der Tol, Rune Christiansen, Peiqi Yang, David Martini, Uwe Rascher, Micol Rossini, Oscar Perez-Priego, Markus Reichstein, Tarek S. El-Madany, Mirco Migliavacca, Javier Pacheco-Labrador, Jin-Hong Guan, Rosario Gonzalez-Cascon, M. Pilar Martín, Gerardo Moreno, Arnaud Carrara, European Commission, Ministerio de Economía y Competitividad (España), Federal Ministry of Economics and Technology (Germany), Carrara, Arnaud [0000-0002-9095-8807], Martín, M. Pilar [0000-0002-5563-8461], Pacheco-Labrador, Javier [0000-0003-3401-7081], Pérez Priego, Oscar [0000-0002-3138-3177], Martini, D, Pacheco-Labrador, J, Perez-Priego, O, van der Tol, C, El-Madany, T, Julitta, T, Rossini, M, Reichstein, M, Christiansen, R, Rascher, U, Moreno, G, Pilar Martin, M, Yang, P, Carrara, A, Guan, J, Gonzalez-Cascon, R, Migliavacca, M, UT-I-ITC-WCC, Faculty of Geo-Information Science and Earth Observation, Department of Water Resources, Carrara, Arnaud, Martín, M. Pilar, Pacheco-Labrador, Javier, and Pérez Priego, Oscar
- Subjects
0106 biological sciences ,Canopy ,010504 meteorology & atmospheric sciences ,Nitrogen ,Science ,chemistry.chemical_element ,sun-induced fluorescence (SIF) ,gross primary production (GPP) ,fertilization ,nitrogen ,phosphorus ,light use efficiency ,SCOPE ,canopy structure ,gross primary production (gpp) ,Photosynthetic efficiency ,Photosynthesis ,01 natural sciences ,Nutrient ,scope ,0105 earth and related environmental sciences ,2. Zero hunger ,Light use efficiency ,Phosphorus ,Primary production ,Phosphoru ,15. Life on land ,Gross primary production (GPP) ,sun-induced fluorescence (sif) ,Sun-induced fluorescence (SIF) ,chemistry ,Agronomy ,Photosynthetically active radiation ,ITC-ISI-JOURNAL-ARTICLE ,Fertilization ,Leaf angle distribution ,General Earth and Planetary Sciences ,ddc:620 ,Canopy structure ,ITC-GOLD ,010606 plant biology & botany - Abstract
Sun-Induced fluorescence at 760 nm (F760) is increasingly being used to predict gross primary production (GPP) through light use efficiency (LUE) modeling, even though the mechanistic processes that link the two are not well understood. We analyzed the effect of nitrogen (N) and phosphorous (P) availability on the processes that link GPP and F760 in a Mediterranean grassland manipulated with nutrient addition. To do so, we used a combination of process-based modeling with Soil-Canopy Observation of Photosynthesis and Energy (SCOPE), and statistical analyses such as path modeling. With this study, we uncover the mechanisms that link the fertilization-driven changes in canopy nitrogen concentration (N%) to the observed changes in F760 and GPP. N addition changed plant community structure and increased canopy chlorophyll content, which jointly led to changes in photosynthetic active radiation (APAR), ultimately affecting both GPP and F760. Changes in the abundance of graminoids, (%graminoids) driven by N addition led to changes in structural properties of the canopy such as leaf angle distribution, that ultimately influenced observed F760 by controlling the escape probability of F760 (Fesc). In particular, we found a change in GPP¿F760 relationship between the first and the second year of the experiment that was largely driven by the effect of plant type composition on Fesc, whose best predictor is %graminoids. The P addition led to a statistically significant increase on light use efficiency of fluorescence emission (LUEf), in particular in plots also with N addition, consistent with leaf level studies. The N addition induced changes in the biophysical properties of the canopy that led to a trade-off between surface temperature (Ts), which decreased, and F760 at leaf scale (F760leaf,fw), which increased. We found that Ts is an important predictor of the light use efficiency of photosynthesis, indicating the importance of Ts in LUE modeling approaches to predict GPP, The project received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 721995. The authors acknowledge the Alexander von Humboldt Foundation for supporting this research with the Max-Planck Prize to Markus Reichstein, and the EUFAR TA project DEHESHyrE (EU FP7 Program), the EnMAP project “MoReDEHESHyReS” (Contract No. 50EE1621, German Aerospace Center (DLR) and German Federal Ministry of Economic Affairs and Energy), SynerTGE (CGL2015-69095-R, MINECO/FEDER, UE) and FLUχPEC (CGL2012-34383, Spanish Ministry of Economy and Competitiveness). This work was supported by a research grant (18968) from VILLUM FONDEN
- Published
- 2019
46. Sun-induced chlorophyll fluorescence II: Review of passive measurement setups, protocols, and their application at the leaf to canopy level
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Aasen, Helge, Van Wittenberghe, Shari, Medina, Neus Sabater, Damm, Alexander, Goulas, Yves, Wieneke, Sebastian, Hueni, Andreas, Malenovský, Zbyněk, Alonso, Luis, Pacheco-Labrador, Javier, Cendrero-Mateo, M Pilar, Tomelleri, Enrico, Burkart, Andreas, Cogliati, Sergio, Rascher, Uwe, Mac Arthur, Alasdair, Aasen, H, Van Wittenberghe, S, Medina, N, Damm, A, Goulas, Y, Wieneke, S, Hueni, A, Malenovsky, Z, Alonso, L, Pacheco-Labrador, J, Cendrero-Mateo, M, Tomelleri, E, Burkart, A, Cogliati, S, Rascher, U, Arthur, A, University of Zurich, and Aasen, Helge
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Vegetation ,UFSP13-8 Global Change and Biodiversity ,FIS/06 - FISICA PER IL SISTEMA TERRA E PER IL MEZZO CIRCUMTERRESTRE ,Science ,1900 General Earth and Planetary Sciences ,GEO/12 - OCEANOGRAFIA E FISICA DELL'ATMOSFERA ,Sun-induced fluorescence ,Spectroradiometer ,Spectrometer ,Radiance ,Reflectance ,Remote sensing ,FLEX ,GEO/11 - GEOFISICA APPLICATA ,10122 Institute of Geography ,GEO/10 - GEOFISICA DELLA TERRA SOLIDA ,General Earth and Planetary Sciences ,ddc:620 ,910 Geography & travel - Abstract
Imaging and non-imaging spectroscopy employed in the field and from aircraft is frequently used to assess biochemical, structural, and functional plant traits, as well as their dynamics in an environmental matrix. With the increasing availability of high-resolution spectroradiometers, it has become feasible to measure fine spectral features, such as those needed to estimate sun-induced chlorophyll fluorescence (F), which is a signal related to the photosynthetic process of plants. The measurement of F requires highly accurate and precise radiance measurements in combination with very sophisticated measurement protocols. Additionally, because F has a highly dynamic nature (compared with other vegetation information derived from spectral data) and low signal intensity, several environmental, physiological, and experimental aspects have to be considered during signal acquisition and are key for its reliable interpretation. The European Cooperation in Science and Technology (COST) Action ES1309 OPTIMISE has produced three articles addressing the main challenges in the field of F measurements. In this paper, which is the second of three, we review approaches that are available to measure F from the leaf to the canopy scale using ground-based and airborne platforms. We put specific emphasis on instrumental aspects, measurement setups, protocols, quality checks, and data processing strategies. Furthermore, we review existing techniques that account for atmospheric influences on F retrieval, address spatial scaling effects, and assess quality checks and the metadata and ancillary data required to reliably interpret retrieved F signals. ISSN:2072-4292
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- 2019
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47. Sun-induced chlorophyll fluorescence III: benchmarking retrieval methods and sensor characteristics for proximal sensing
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Sebastian Wieneke, Luis Guanter, Alasdair Mac Arthur, Marco Celesti, Neus Sabater, Francisco de Assis de Carvalho Pinto, M. Pilar Cendrero-Mateo, Javier Pacheco-Labrador, Yves Goulas, Jose Moreno, Tommaso Julitta, Micol Rossini, Luis Alonso, Alexander Damm, Helge Aasen, Sergio Cogliati, Uwe Rascher, Cendrero-Mateo, M, Wieneke, S, Damm, A, Alonso, L, Pinto, F, Moreno, J, Guanter, L, Celesti, M, Rossini, M, Sabater, N, Cogliati, S, Julitta, T, Rascher, U, Goulas, Y, Aasen, H, Pacheco-Labrador, J, Arthur, A, University of Zurich, and Cendrero-Mateo, M Pilar
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010504 meteorology & atmospheric sciences ,Computer science ,Economics ,Ground spectrometers ,Science ,0211 other engineering and technologies ,Context (language use) ,02 engineering and technology ,Ground spectrometer ,01 natural sciences ,Spectral line ,Retrieval method ,Approximation error ,Sun-induced chlorophyll fluorescence ,Sensitivity (control systems) ,910 Geography & travel ,Chlorophyll fluorescence ,021101 geological & geomatics engineering ,0105 earth and related environmental sciences ,Remote sensing ,Retrieval methods ,Spectrometer ,1900 General Earth and Planetary Sciences ,Hyperspectral imaging ,sun-induced chlorophyll fluorescence ,ground spectrometers ,retrieval methods ,3. Good health ,10122 Institute of Geography ,FISICA APLICADA ,Line (geometry) ,General Earth and Planetary Sciences ,ddc:620 ,Interpolation - Abstract
[EN] The interest of the scientific community on the remote observation of sun-induced chlorophyll fluorescence (SIF) has increased in the recent years. In this context, hyperspectral ground measurements play a crucial role in the calibration and validation of future satellite missions. For this reason, the European cooperation in science and technology (COST) Action ES1309 OPTIMISE has compiled three papers on instrument characterization, measurement setups and protocols, and retrieval methods (current paper). This study is divided in two sections; first, we evaluated the uncertainties in SIF retrieval methods (e.g., Fraunhofer line depth (FLD) approaches and spectral fitting method (SFM)) for a combination of off-the-shelf commercial spectrometers. Secondly, we evaluated how an erroneous implementation of the retrieval methods increases the uncertainty in the estimated SIF values. Results show that the SFM approach applied to high-resolution spectra provided the most reliable SIF retrieval with a relative error (RE) 6% and, This article is based upon work from COST Action ES1309 OPTIMISE, supported by COST (European Cooperation in Science and Technology; www.cost.eu).Cendrero-Mateo M.P. and Alonso L. are currently funded by AVANFLEX project (Advanced Products for the FLEX mission), no ESP2016-79503-C2-1-P, Ministry of Economy and Competitiveness, Spain. Wieneke S. is currently funded by the individual fellowship of the European Union's H2020 Marie Sklodowska-Curie actions under the grant agreement ReSPEc no [795299]. Goulas Y. is currently funded by the ECOFLUO project (In-situ Remote Sensing of Chlorophyll Fluorescence to Monitor Carbon Dynamics in Ecosystems in support of the FLEX mission), no 4500058116 and 4500058229, Centre National d'Etudes Spatiales (CNES), France. Mac Arthur, A. was funded by the UK's NERC/NCEO Field Spectroscopy Facility, at the University of Edinburgh. Pacheco-Labrador, J. was supported by the EnMAP project MoReDEHESHyReS "Modelling Responses of Dehesas with Hyperspectral Remote Sensing" (Contract No. 50EE1621, German Aerospace Center (DLR) and the German Federal Ministry of Economic Affairs and Energy) and the Alexander von Humboldt Foundation via Max-Planck Prize to Markus Reichstein.
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- 2019
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48. Photosynthesis-sun induced fluorescence relationship in a Mediterranean grassland
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Markus Reichstein, Tommaso Julitta, Mirco Migliavacca, Tarek El Madany, Oscar Perez-Priego, David Martini, Christiaan van der Tol, Javier Pacheco-Labrador, Micol Rossini, Anatoly A. Gitelson, Department of Water Resources, Faculty of Geo-Information Science and Earth Observation, UT-I-ITC-WCC, Martini, D, Pacheco-Labrador, J, Perez-Priego, O, Van Der Tol, C, El Madany, T, Julitta, T, Rossini, M, Gitelson, A, Reichstein, M, and Migliavacca, M
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0106 biological sciences ,Mediterranean climate ,geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,22/3 OA procedure ,Primary production ,Atmospheric model ,Fesc ,Atmospheric sciences ,Photosynthesis ,Sun induced fluorescence ,01 natural sciences ,Fluorescence ,Grassland ,Functional trait ,Principal component analysis ,Radiative transfer ,GPP ,SCOPE model ,Canopy structure ,Functional traits ,010606 plant biology & botany ,0105 earth and related environmental sciences ,Mathematics - Abstract
Sun induced fluorescence at 760 nm (F 760 ) has shown to provide a valid approach to quantify gross primary production (GPP) at various scales, however the relationship between GPP and F760 is influenced by the escape probability of fluorescence (Fesc), a variable which is not still fully understood. Combining radiative transfer modelling approaches, by means of the SCOPE model, and a data driven methodology based on variable selection methods we identify the predictors of Fesc, focusing on the effect of functional and structural traits. We show that Fesc is mainly predicted by structural variables such as fraction of grasses and near infrared reflectance. Building on the analysis of the predictor of Fesc, LUE p and LUE f we present a semi-empirical model formulation based only on optical data that significantly improves the GPP prediction.
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- 2018
49. Assessing the use of multiple constraints and ancillary data to support scope model inversion in a experimental grassland
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Luis Guanter, Gerardo Moreno, M. Pilar Martín, Mirco Migliavacca, Nuno Carvalhais, Markus Reichstein, Arnaud Carrara, Javier Pacheco-Labrador, Micol Rossini, Oscar Perez-Priego, Tarek S. El-Madany, Tommaso Julitta, Rosario Gonzalez-Cascon, Pacheco-Labrador, J, Carvalhais, N, Perez-Priego, O, El-Madany, T, Rossini, M, Julitta, T, Moreno, G, Gonzalez-Cascon, R, Pilar Martin, M, Reichstein, M, Carrara, A, Guanter, L, and Migliavacca, M
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0106 biological sciences ,Discrete mathematics ,010504 meteorology & atmospheric sciences ,Inversion (meteorology) ,Atmospheric model ,Overfitting ,Inverse problem ,Prior information ,01 natural sciences ,Plant trait ,Ancillary data ,SCOPE ,Prior probability ,Radiative transfer ,Model inversion ,010606 plant biology & botany ,0105 earth and related environmental sciences ,Mathematics - Abstract
The SCOPE model embeds the state of art for coupling soil vegetation atmosphere transfer (SVAT) and radiative transfer models (RTM). For that reason the FLuorescence EXplorer (FLEX) mission selected this model to derive vegetation properties through inversion. However inverse problem is often ill-posed, providing equally likely solutions and hence inflating the uncertainty of the retrieved parameters. In this work we test the use of different priors based on ancillary measurements and literature to support multiple-constrain inversion of SCOPE. Results show that prior information on the relationships between variables such as leaf chlorophyll content $(C_{\text{ab}})$ , leaf carotenoids content $(C_{\text{ca}})$ , leaf water content $(C_{\mathrm{w}})$ and/or maximum carboxylation rate $(V_{\text{cmax}})$ reduce inversion uncertainties and overfitting, and should be sampled/estimated together with optical data.
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- 2018
50. Plant functional traits and canopy structure control the relationship between photosynthetic CO2 uptake and far-red sun-induced fluorescence in a Mediterranean grassland under different nutrient availability
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Anna Berninger, Tommaso Julitta, Talie Musavi, M. Pilar Martín, Francesco Fava, Andreas Burkart, Kathrin Henkel, Markus Reichstein, Arnaud Carrara, Mirco Migliavacca, Christiaan van der Tol, Sönke Zaehle, Javier Pacheco-Labrador, Thomas Wutzler, Olaf Kolle, Tiana W. Hammer, Oscar Perez-Priego, Tarek S. El-Madany, Micol Rossini, Uwe Rascher, Gerardo Moreno, Andrea Pérez‐Burgueño, Jin-Hong Guan, Verena Bessenbacher, Enrique Juarez‐Alcalde, European Commission, Martín, M. Pilar [0000-0002-5563-8461], Pérez Prieto, Oscar [0000-0002-3138-3177], Carrara, Arnaud [0000-0002-9095-8807], Pacheco-Labrador, Javier [0000-0003-3401-7081], Martín, M. Pilar, Pérez Prieto, Oscar, Carrara, Arnaud, Pacheco-Labrador, Javier, Department of Water Resources, Faculty of Geo-Information Science and Earth Observation, UT-I-ITC-WCC, Migliavacca, M, Perez Priego, O, Rossini, M, El Madany, T, Moreno, G, van der Tol, C, Rascher, U, Berninger, A, Bessenbacher, V, Burkart, A, Carrara, A, Fava, F, Guan, J, Hammer, T, Henkel, K, Juarez Alcalde, E, Julitta, T, Kolle, O, Martín, M, Musavi, T, Pacheco Labrador, J, Pérez Burgueño, A, Wutzler, T, Zaehle, S, and Reichstein, M
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Canopy ,Mediterranean climate ,Chlorophyll a ,Soil–canopy observation of photosynthesis and energy (SCOPE) mode ,010504 meteorology & atmospheric sciences ,Physiology ,0211 other engineering and technologies ,02 engineering and technology ,Plant Science ,Biology ,Gross primary productivity (GPP) ,Photosynthesis ,01 natural sciences ,chemistry.chemical_compound ,Nutrient ,soil–canopy observation of photosynthesis and energy (SCOPE) model ,Abundance (ecology) ,Leaf inclination distribution function ,Botany ,functional trait ,021101 geological & geomatics engineering ,0105 earth and related environmental sciences ,Far‐red sun‐induced fluorescence ,Primary production ,Far-red ,far-red sun-induced fluorescence ,22/4 OA procedure ,Nutrient manipulation ,chemistry ,Agronomy ,ITC-ISI-JOURNAL-ARTICLE ,Canopy structure ,Functional traits - Abstract
Sun-induced fluorescence (SIF) in the far-red region provides a new noninvasive measurement approach that has the potential to quantify dynamic changes in light-use efficiency and gross primary production (GPP). However, the mechanistic link between GPP and SIF is not completely understood. We analyzed the structural and functional factors controlling the emission of SIF at 760 nm (F760) in a Mediterranean grassland manipulated with nutrient addition of nitrogen (N), phosphorous (P) or nitrogen¿phosphorous (NP). Using the soil¿canopy observation of photosynthesis and energy (SCOPE) model, we investigated how nutrient-induced changes in canopy structure (i.e. changes in plant forms abundance that influence leaf inclination distribution function, LIDF) and functional traits (e.g. N content in dry mass of leaves, N%, Chlorophyll a+b concentration (Cab) and maximum carboxylation capacity (Vcmax)) affected the observed linear relationship between F760 and GPP. We conclude that the addition of nutrients imposed a change in the abundance of different plant forms and biochemistry of the canopy that controls F760. Changes in canopy structure mainly control the GPP¿F760 relationship, with a secondary effect of Cab and Vcmax. In order to exploit F760 data to model GPP at the global/regional scale, canopy structural variability, biodiversity and functional traits are important factors that have to be considered., The authors acknowledge the Alexander von Humboldt Foundation for supporting this research with the Max-Planck Prize to Markus Reichstein, and the EUFAR TA project DEHESHyrE (EU FP7 Program). We acknowledge the Majadas de Tietar city council for its support. The authors acknowledge the Freiland Group and in particular Martin Hertel from MPI-Jena and Ramon Lopez-Jimenez (CEAM) for technical assistance. The authors thank the anonymous referee and the editor for their comments on the work, Alessandro Cescatti for discussions about the results and Silvana Schott for the graphics.
- Published
- 2017
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