Research Center del Fuego

Toledo, Spain

Research Center del Fuego

Toledo, Spain

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de Dios V.R.,University of Western Sydney | de Dios V.R.,Research Center del Fuego | Goulden M.L.,University of California at Irvine | Ogle K.,Arizona State University | And 15 more authors.
Global Change Biology | Year: 2012

It is often assumed that daytime patterns of ecosystem carbon assimilation are mostly driven by direct physiological responses to exogenous environmental cues. Under limited environmental variability, little variation in carbon assimilation should thus be expected unless endogenous plant controls on carbon assimilation, which regulate photosynthesis in time, are active. We evaluated this assumption with eddy flux data, and we selected periods when net ecosystem exchange (NEE) was decoupled from environmental variability in seven sites from highly contrasting biomes across a 74° latitudinal gradient over a total of 36 site-years. Under relatively constant conditions of light, temperature, and other environmental factors, significant diurnal NEE oscillations were observed at six sites, where daily NEE variation was between 20% and 90% of that under variable environmental conditions. These results are consistent with fluctuations driven by the circadian clock and other endogenous processes. Our results open a promising avenue of research for a more complete understanding of ecosystem fluxes that integrates from cellular to ecosystem processes. © 2012 Blackwell Publishing Ltd.


Resco V.,Research Center del Fuego | Querejeta J.I.,CSIC - Center of Edafology and Applied Biology of the Segura | Ogle K.,University of Wyoming | Voltas J.,University of Lleida | And 8 more authors.
Biology Letters | Year: 2010

Stable isotopes and their potential for detecting various and complex ecosystem processes are attracting an increasing number of scientists. Progress is challenging, particularly under global change scenarios, but some established views have been challenged. The IX meeting of the Spanish Association of Terrestrial Ecology (AAET, Úbeda, 18-22 October 2009) hosted a symposium on the ecology of stable isotopes where the linear mixing model approach of partitioning sinks and sources of carbon and water fluxes within an ecosystem was challenged, and new applications of stable isotopes for the study of plant interactions were evaluated. Discussion was also centred on the need for networks that monitor ecological processes using stable isotopes and key ideas for fostering future research with isotopes. © 2009 The Royal Society.


Reverter B.R.,University of Granada | Reverter B.R.,Centro Andaluz Of Medio Ambiente Ceama | Sanchez-Canete E.P.,CSIC - Estación Experimental De Zonas Áridas | Resco V.,Research Center del Fuego | And 4 more authors.
Biogeosciences | Year: 2010

Two years of continuous measurements of net ecosystem exchange (NEE) using the eddy covariance technique were made over a Mediterranean alpine shrubland. This ecosystem was found to be a net source of CO2 (+ 52 ± 7 g C m-2 and + 48 ± 7 g C m-2 for 2007 and 2008) during the two-year study period. To understand the reasons underlying this net release of CO2 into the atmosphere, we analysed the drivers of seasonal variability in NEE over these two years. We observed that the soil water availability - driven by the precipitation pattern - and the photosynthetic photon flux density (PPFD) are the key factors for understanding both the carbon sequestration potential and the duration of the photosynthetic period during the growing season. Finally, the effects of the self-heating correction to CO2 and H2O fluxes measured with the open-path infrared gas analyser were evaluated. Applying the correction turned the annual CO2 budget in 2007 from a sink (-135 ± 7 g C m -2) to a source (+ 52 ± 7 g C m-2). The magnitude of this change is larger than reported previously and is shown to be due to the low air density and cold temperatures at this high elevation study site. © Author(s) 2010.


Resco V.,Research Center del Fuego | Ferrio J.P.,University of Lleida | Carreira J.A.,University of Jaén | Calvo L.,University of León | And 10 more authors.
Plant Ecology and Diversity | Year: 2011

We review the relevance and use of stable isotopes for the study of plant community succession. Stable isotope measurements provide information on the origin of resources acquired by plants, the processes governing resource uptake and transformation, and the physiological and environmental conditions of plant growth. When combined with measurements of the stable isotope ratio values of soil microbial biomass, soil organic matter and plant litter, isotope measurements of plants can indicate effects of successional changes on ecosystem processes. However, their application to questions of plant succession and ecosystem change is limited by the degree to which the underlying assumptions are met in each study, and complementary measures may be required, depending upon the question of interest. First, we discuss the changes that occur in the stable isotope composition of plants and ecosystems with ontogeny and species replacements, as well as their potential evolutionary significance. Second, we discuss the imprints of plant competition and facilitation on leaf and wood tissue, as well as how stable isotopes can provide novel insights on the mechanisms underlying plant interactions. Finally, we discuss the capacity for stable isotope measurements to serve as a proxy record for past disturbances such as fire, logging and cyclones. © 2011 Botanical Society of Scotland and Taylor & Francis.


Sun W.,University of Wyoming | Sun W.,Washington State University | Resco V.,University of Wyoming | Resco V.,Research Center del Fuego | Williams D.G.,University of Wyoming
Oecologia | Year: 2010

The C isotope composition of leaf dark-respired CO2 (δ13Cl) integrates short-term metabolic responses to environmental change and is potentially recorded in the isotopic signature of ecosystem-level respiration. Species differences in photosynthetic pathway, resource acquisition and allocation patterns, and associated isotopic fractionations at metabolic branch points can influence δ13Cl, and differences are likely to be modified by seasonal variation in drought intensity. We measured δ13Cl in two deep-rooted C3 trees (Prosopis velutina and Celtis reticulata), and two relatively shallow-rooted perennial herbs (a C3 dicot Viguiera dentata and a C4 grass Sporobolus wrightii) in a floodplain savanna ecosystem in southeastern Arizona, USA during the dry pre-monsoon and wet monsoon seasons. δ13Cl decreased during the nighttime and reached minimum values at pre-dawn in all species. The magnitude of nocturnal shift in δ13Cl differed among species and between pre-monsoon and monsoon seasons. During the pre-monsoon season, the magnitude of the nocturnal shift in δ13Cl in the deep-rooted C3 trees P. velutina (2.8 ± 0.4‰) and C. reticulata (2.9 ± 0.2‰) was greater than in the C3 herb V. dentata (1.8 ± 0.4‰) and C4 grass S. wrightii (2.2 ± 0.4‰). The nocturnal shift in δ13Cl in V. dentata and S. wrightii increased to 3.2 ± 0.1‰ and 4.6 ± 0.6‰, respectively, during the monsoon season, but in C3 trees did not change significantly from pre-monsoon values. Cumulative daytime net CO2 uptake was positively correlated with the magnitude of the nocturnal decline in δ13Cl across all species, suggesting that nocturnal δ13Cl may be controlled by 13C/12C fractionations associated with C substrate availability and C metabolite partitioning. Nocturnal patterns of δ13Cl in dominant plant species in the semiarid savanna apparently have predictable responses to seasonal changes in water availability, which is important for interpreting and modeling the C isotope signature of ecosystem-respired CO2. © 2010 Springer-Verlag.


Johansen K.,University of Queensland | Tiede D.,University of Salzburg | Blaschke T.,University of Salzburg | Arroyo L.A.,Research Center del Fuego | Phinn S.,University of Queensland
Remote Sensing | Year: 2011

This research presents a time-effective approach for mapping streambed and riparian zone extent from high spatial resolution LiDAR derived products, i.e., digital terrain model, terrain slope and plant projective cover. Geographic object based image analysis (GEOBIA) has proven useful for feature extraction from high spatial resolution image data because of the capacity to reduce effects of reflectance variations of pixels making up individual objects and to include contextual and shape information. This functionality increases the likelihood of developing transferable and automated mapping approaches. LiDAR data covered parts of the Werribee Catchment in Victoria, Australia, which is characterized by urban, agricultural, and forested land cover types. Field data of streamside vegetation structure and physical form properties were used for both calibration of the mapping routines and validation of the mapping results. To improve the transferability of the rule set, the GEOBIA approach was developed for an area representing different riparian zone environments, i.e., urbanized, agricultural and hilly forested areas. Results show that mapping streambed extent (R2 = 0.93, RMSE = 3.6 m, n = 35) and riparian zone extent (R2 = 0.74, RMSE = 3.9, n = 35) from LiDAR derived products can be automated using GEOBIA to enable derivation of spatial information in an accurate and time-effective manner suited for natural resource management agencies. © 2011 by the authors.


Johansen K.,University of Queensland | Tiede D.,University of Salzburg | Blaschke T.,University of Salzburg | Phinn S.,University of Queensland | And 2 more authors.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2010

This research presents a time-effective approach for mapping streambed and riparian zone extent from high spatial resolution LiDAR derived products, i.e. digital terrain model, terrain slope and plant projective cover. Geographic object based image analysis (GEOBIA) has proven useful for feature extraction from high spatial resolution image data because of the capacity to reduce effects of reflectance variations of pixels making up individual objects and to include contextual and shape information. This functionality increases the likelihood of generalizing classification rules, which may lead to the development of automated mapping approaches. The LiDAR data were captured in May 2005 with 1.6 m point spacing and included first and last returns and an intensity layer. The returns were classified as ground and non-ground points by the data provider. The data covered parts of the Werribee Catchment in Victoria, Australia, which is characterized by urban, agricultural, and forested land cover types. Field data of streamside vegetation structure and physical form properties were obtained in April 2008. The field data were used both for calibration of the mapping routines and to validate the mapping results. To improve the transferability of the rule set, the GEOBIA approach was developed for an area representing different riparian zone environments, i.e. urbanised areas, agricultural areas, and hilly forested areas. Results show that mapping streambed extent (R2 = 0.93, RMSE = 3.6 m, n = 35) and riparian zone extent (R2 = 0.74, RMSE = 3.9, n = 35) from LiDAR derived products can be automated using GEOBIA. This work lays the foundation for automatic feature extraction of biophysical properties of riparian zones to enable derivation of spatial information in an accurate and time-effective manner suited for natural resource management agencies.


Pascual C.,Technical University of Madrid | Garcia-Montero L.G.,Technical University of Madrid | Arroyo L.A.,Research Center Del Fuego | Garcia-Abril A.,Technical University of Madrid
Annals of Forest Science | Year: 2013

Context: Forest structure characterisation approaches using LiDAR data and object-based image analysis remain scarce to forestry agencies as these automated procedures usually require the use of expensive software and highly skilled analysts. The integration of forest expert opinion into semi-automated approaches would simplify the access of forest managers to new technologies and would allow the incorporation of personal experience and the introduction of specific forest management criteria. Aim: The aim of this study is to explore new alternatives to a previously published automated approach based on LiDAR data and object-based image analysis. Methods: We compare four approaches, ranging from null to high incorporation of expert opinion and from fully automated to fully manual. These four approaches consist of three stages: (1) forest stand identification from LiDAR models, (2) forest stand classification into forest structure classes (manual and based on cluster analysis), and (3) validation. Results: Quantitative attributes for validation (i.e. hypsographs and percentiles) provided slightly lower degree of separability for forest structure classes, in the mixed procedures with increasing incorporation of expert opinion than for the fully automated approach. Conclusions: The new mixed approaches proposed are comparable to the automated procedures for the characterisation of forest structure in heterogeneous pine forest stands. They also offer additional advantages: (1) they make it possible to give a specific management focus and (2) they provide accessibility by the forest managers to the source of LiDAR information. © 2012 INRA / Springer-Verlag France.


Hernando A.,Technical University of Madrid | Arroyo L.A.,Research Center del Fuego | Velazquez J.,Technical University of Madrid | Velazquez J.,Catholic University of Avila | Tejera R.,Technical University of Madrid
Photogrammetric Engineering and Remote Sensing | Year: 2012

Natura 2000 is a European network of protected areas established under the Habitats Directive (92/43/EEC). According to the Habitats Directive, habitat maps must be periodically updated, which requires the development of cost- and time-efficient mapping practices. In this study, we propose a methodology for habitat mapping using very high spatial resolution (QuickBird) images with Object-Based Image Analysis (OBIA). We classified five segmentation levels: level 5 incorporated the prior knowledge of the study area into the analysis; level 4 and 1 were used to identify arable areas and land covers, respectively. The information contained in levels 1, 4, and 5 was then combined to classify plant species in level 2. Finally, habitats were classified in level 3 using level 2 class-related features. The habitat map obtained had an overall accuracy of 86.3 percent. Classification accuracies were higher for treeand pasture-dominated habitats than for shrub-dominated habitats. © 2012 American Society for Photogrammetry and Remote Sensing.


PubMed | Research Center del Fuego
Type: Journal Article | Journal: Biology letters | Year: 2010

Stable isotopes and their potential for detecting various and complex ecosystem processes are attracting an increasing number of scientists. Progress is challenging, particularly under global change scenarios, but some established views have been challenged. The IX meeting of the Spanish Association of Terrestrial Ecology (AAET, Ubeda, 18-22 October 2009) hosted a symposium on the ecology of stable isotopes where the linear mixing model approach of partitioning sinks and sources of carbon and water fluxes within an ecosystem was challenged, and new applications of stable isotopes for the study of plant interactions were evaluated. Discussion was also centred on the need for networks that monitor ecological processes using stable isotopes and key ideas for fostering future research with isotopes.

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