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Papers by Cristina Aponte
International Journal of Wildland Fire, 2016
Forest Ecology and Management, 2016
We synthesise a series of independent but integrated studies on the functioning of a mixed Medite... more We synthesise a series of independent but integrated studies on the functioning of a mixed Mediterranean oak forest to demonstrate the tree-soil interactions underpinning a positive feedback process that sustains the coexistence of two oak species. The studies focused on the foliar functional traits, plant regeneration patterns, biogeochemical cycles, soil microbial biomass and ectomycorrhizal (ECM) fungal diversity associated with the co-dominant evergreen Quercus suber and deciduous Quercus canariensis in a Mediterranean forest in southern Spain.
Soil microbial populations influence the pool of nutrients available for plants, immobililizing i... more Soil microbial populations influence the pool of nutrients available for plants, immobililizing inorganic resources in their biomass and releasing them when population declines. The asynchrony between these nutrient retention-mobilization cycles and plant resources ...
... and Agrobiology, CSIC, PO Box 1052, 41080, Seville, Spain, teodoro@irnase.csic.es, maitedn@ir... more ... and Agrobiology, CSIC, PO Box 1052, 41080, Seville, Spain, teodoro@irnase.csic.es, maitedn@irnase.csic.es, aponte@irnase.csic.es ... siliqua 16 Populus alba 27 Retama sphaerocarpa 6 Callicotome villosa 17 Phillyrea angustifolia 28 Rubus ulmifolius 7 Erica arborea 18 ...
Mediterranean oak forests have a high ecologic and economic value. The sustainability these fores... more Mediterranean oak forests have a high ecologic and economic value. The sustainability these forests relies on the symbiosis established between tree species and tomycorrhizal (EM) fungal community. Oaks provide fungi with photosynthesized products that are used to generate ...
... María T. Domínguez1, Cristina Aponte 1, Ignacio M. Pérez-Ramos1, Luís V. García1, Rafael Vill... more ... María T. Domínguez1, Cristina Aponte 1, Ignacio M. Pérez-Ramos1, Luís V. García1, Rafael Villar2 and Teodoro Marañón1 1 Instituto de ... L. Cs Cistaceae Shrub Evergreen ECT Calicotome villosa (Poir.) Link Cv Fabaceae Shrub Summer deciduous N-FIX Erica arborea L. Ea ...
Centennial cork oaks (Quercus suber L.) are spread in the sandy soils of Doñana (SW Spain). They ... more Centennial cork oaks (Quercus suber L.) are spread in the sandy soils of Doñana (SW Spain). They are remnants from the formerly extended oak forests that were overexploited during the XVII-XX centuries. After the protection of the area as Biological Reserve forty years ago, all silvicultural practices such as cutting, pruning and cork extraction ceased. At the same time, seven species of wading birds began to nest on the centennial oaks located in the marsh edge, forming a big colony. We hypothesize that colonial nesting birds are ...
Since early 90's, a severe decline of aged cork oak populations has been observed in the are... more Since early 90's, a severe decline of aged cork oak populations has been observed in the area called “La Vera” at Doñana National Park in southern Spain. At the current rate of mortality, cork oaks are predicted to be extincted in just a few decades. Oak decline seems to include various factors. One of the most evident causes of the decline is the pressure of a big colony of tree-nesting wading birds, as long as the large amounts of bird dejections could modify soil properties and the ecology of their mycoflora. On the other hand, it was ...
Fires affect wide areas and their effects can be successfully estimated from a range of remote se... more Fires affect wide areas and their effects can be successfully estimated from a range of remote sensing sensors, with synthetic aperture radars (SAR) being of particular interest due to their sensitivity to forest vertical structure, global availability and independence of cloud cover or solar elevation. Previous studies have demonstrated the sensitivity to fire effects of L-band SAR sensors using post-fire datasets and empirical modeling. This study proposed an innovative method for estimating fire severity by combining pre- and post-fire SAR datasets within a change detection framework to compute a novel index, the Radar Burn Ratio (RBR). More importantly, a standardized RBR was developed and tested over seven temperate forest types located on three continents with above ground biomass values ranging from 30 to over 500 t ha− 1. RBR standardization allowed for common thresholds to be defined and subsequently used for estimating the Composite Burn Index (CBI, a measure of fire impact) without the need for a priori information (i.e., in situ data) on local post-fire conditions. The estimation accuracy of the standardized RBR was compared to locally-calibrated empirical models based on field CBI data. The results showed similar estimation errors and a strong agreement with the reference in situ data (i.e., Cohen's weighted kappa > 0.61). The RBR index most sensitive to fire severity was based on the cross-polarized channel applied under dry environmental conditions. Under wet conditions the estimation accuracy was considerably lower. The methods proposed in this study are particularly valuable for rapid fire severity assessments at regional to global scales, requiring only that RBR thresholds be calibrated for a range of environments and that CBI scores be related to fuel consumption for each forest type.
Timely information on spatial variation of live fuel moisture is critical for fire risk assessmen... more Timely information on spatial variation of live fuel moisture is critical for fire risk assessment and behaviour modelling. Using an airborne synthetic aperture radar system, the sensitivity of radar data to live fuel (i.e. canopy foliage) moisture was evaluated. Field and airborne measurements were collected over a 3-week period in a semiarid Australian forest dominated by white cypress pine (Callitris glaucophylla). Linear regression models were used to relate equivalent water thickness and live fuel moisture content to backscatter intensity and polarimetric decomposition components. Results showed that radar systems can provide estimates of live fuel moisture with similar or better accuracies for both equivalent water thickness (R2 = 0.7–0.8, root mean squared error (RMSE) = 15%) and live fuel moisture content (R2 = 0.6–0.7, RMSE = 10%) than those achieved in previous studies using optical-based vegetation indices. It was also possible to estimate soil moisture under the forest canopy with accuracies of 0.05 volume/volume (v v–1) (R2 = 0.5–0.6). This is particularly relevant in the context of fire management because moisture availability of fine fuels is related to soil water content.
Monitoring fire effects at landscape level is viable from remote sensing platforms providing repe... more Monitoring fire effects at landscape level is viable from remote sensing platforms providing repeatable and
consistent measurements. Previous studies have estimated fire severity using optical and synthetic aperture radar
(SAR) sensors, but to our knowledge, none have compared their effectiveness. Our study carried out such a
comparison by using change detection indices computed from pre- and post-fire L-band space borne SAR datasets
to estimate fire severity for seven fires located on three continents. Such indices were related to field estimated
fire severity through empirical models, and their estimation accuracy was compared. Empirical models based on
the joint use of optical and radar indices were also evaluated. The results showed that, optical based indices
provided more accurate fire severity estimates. On average, overall accuracy increased from 61% (SAR) to 76%
(optical) for high biomass forests. For low biomass forests (i.e., above ground biomass levels below the L-band
saturation point), radar indices provided comparable results, with overall accuracy being only slightly lower when
compared to optical indices (69% vs. 73%). The joint use of optical and radar indices decreased the estimation
error and reduced misclassification of unburnt forest by 9% for eucalypt and 3% for coniferous forests.
Additional keywords: Landsat, ALOS PALSAR, L-band, radar, accuracy assessment, radar-optical synergy, CBI
International Journal of Wildland Fire, 2016
Forest Ecology and Management, 2016
We synthesise a series of independent but integrated studies on the functioning of a mixed Medite... more We synthesise a series of independent but integrated studies on the functioning of a mixed Mediterranean oak forest to demonstrate the tree-soil interactions underpinning a positive feedback process that sustains the coexistence of two oak species. The studies focused on the foliar functional traits, plant regeneration patterns, biogeochemical cycles, soil microbial biomass and ectomycorrhizal (ECM) fungal diversity associated with the co-dominant evergreen Quercus suber and deciduous Quercus canariensis in a Mediterranean forest in southern Spain.
Soil microbial populations influence the pool of nutrients available for plants, immobililizing i... more Soil microbial populations influence the pool of nutrients available for plants, immobililizing inorganic resources in their biomass and releasing them when population declines. The asynchrony between these nutrient retention-mobilization cycles and plant resources ...
... and Agrobiology, CSIC, PO Box 1052, 41080, Seville, Spain, teodoro@irnase.csic.es, maitedn@ir... more ... and Agrobiology, CSIC, PO Box 1052, 41080, Seville, Spain, teodoro@irnase.csic.es, maitedn@irnase.csic.es, aponte@irnase.csic.es ... siliqua 16 Populus alba 27 Retama sphaerocarpa 6 Callicotome villosa 17 Phillyrea angustifolia 28 Rubus ulmifolius 7 Erica arborea 18 ...
Mediterranean oak forests have a high ecologic and economic value. The sustainability these fores... more Mediterranean oak forests have a high ecologic and economic value. The sustainability these forests relies on the symbiosis established between tree species and tomycorrhizal (EM) fungal community. Oaks provide fungi with photosynthesized products that are used to generate ...
... María T. Domínguez1, Cristina Aponte 1, Ignacio M. Pérez-Ramos1, Luís V. García1, Rafael Vill... more ... María T. Domínguez1, Cristina Aponte 1, Ignacio M. Pérez-Ramos1, Luís V. García1, Rafael Villar2 and Teodoro Marañón1 1 Instituto de ... L. Cs Cistaceae Shrub Evergreen ECT Calicotome villosa (Poir.) Link Cv Fabaceae Shrub Summer deciduous N-FIX Erica arborea L. Ea ...
Centennial cork oaks (Quercus suber L.) are spread in the sandy soils of Doñana (SW Spain). They ... more Centennial cork oaks (Quercus suber L.) are spread in the sandy soils of Doñana (SW Spain). They are remnants from the formerly extended oak forests that were overexploited during the XVII-XX centuries. After the protection of the area as Biological Reserve forty years ago, all silvicultural practices such as cutting, pruning and cork extraction ceased. At the same time, seven species of wading birds began to nest on the centennial oaks located in the marsh edge, forming a big colony. We hypothesize that colonial nesting birds are ...
Since early 90's, a severe decline of aged cork oak populations has been observed in the are... more Since early 90's, a severe decline of aged cork oak populations has been observed in the area called “La Vera” at Doñana National Park in southern Spain. At the current rate of mortality, cork oaks are predicted to be extincted in just a few decades. Oak decline seems to include various factors. One of the most evident causes of the decline is the pressure of a big colony of tree-nesting wading birds, as long as the large amounts of bird dejections could modify soil properties and the ecology of their mycoflora. On the other hand, it was ...
Fires affect wide areas and their effects can be successfully estimated from a range of remote se... more Fires affect wide areas and their effects can be successfully estimated from a range of remote sensing sensors, with synthetic aperture radars (SAR) being of particular interest due to their sensitivity to forest vertical structure, global availability and independence of cloud cover or solar elevation. Previous studies have demonstrated the sensitivity to fire effects of L-band SAR sensors using post-fire datasets and empirical modeling. This study proposed an innovative method for estimating fire severity by combining pre- and post-fire SAR datasets within a change detection framework to compute a novel index, the Radar Burn Ratio (RBR). More importantly, a standardized RBR was developed and tested over seven temperate forest types located on three continents with above ground biomass values ranging from 30 to over 500 t ha− 1. RBR standardization allowed for common thresholds to be defined and subsequently used for estimating the Composite Burn Index (CBI, a measure of fire impact) without the need for a priori information (i.e., in situ data) on local post-fire conditions. The estimation accuracy of the standardized RBR was compared to locally-calibrated empirical models based on field CBI data. The results showed similar estimation errors and a strong agreement with the reference in situ data (i.e., Cohen's weighted kappa > 0.61). The RBR index most sensitive to fire severity was based on the cross-polarized channel applied under dry environmental conditions. Under wet conditions the estimation accuracy was considerably lower. The methods proposed in this study are particularly valuable for rapid fire severity assessments at regional to global scales, requiring only that RBR thresholds be calibrated for a range of environments and that CBI scores be related to fuel consumption for each forest type.
Timely information on spatial variation of live fuel moisture is critical for fire risk assessmen... more Timely information on spatial variation of live fuel moisture is critical for fire risk assessment and behaviour modelling. Using an airborne synthetic aperture radar system, the sensitivity of radar data to live fuel (i.e. canopy foliage) moisture was evaluated. Field and airborne measurements were collected over a 3-week period in a semiarid Australian forest dominated by white cypress pine (Callitris glaucophylla). Linear regression models were used to relate equivalent water thickness and live fuel moisture content to backscatter intensity and polarimetric decomposition components. Results showed that radar systems can provide estimates of live fuel moisture with similar or better accuracies for both equivalent water thickness (R2 = 0.7–0.8, root mean squared error (RMSE) = 15%) and live fuel moisture content (R2 = 0.6–0.7, RMSE = 10%) than those achieved in previous studies using optical-based vegetation indices. It was also possible to estimate soil moisture under the forest canopy with accuracies of 0.05 volume/volume (v v–1) (R2 = 0.5–0.6). This is particularly relevant in the context of fire management because moisture availability of fine fuels is related to soil water content.
Monitoring fire effects at landscape level is viable from remote sensing platforms providing repe... more Monitoring fire effects at landscape level is viable from remote sensing platforms providing repeatable and
consistent measurements. Previous studies have estimated fire severity using optical and synthetic aperture radar
(SAR) sensors, but to our knowledge, none have compared their effectiveness. Our study carried out such a
comparison by using change detection indices computed from pre- and post-fire L-band space borne SAR datasets
to estimate fire severity for seven fires located on three continents. Such indices were related to field estimated
fire severity through empirical models, and their estimation accuracy was compared. Empirical models based on
the joint use of optical and radar indices were also evaluated. The results showed that, optical based indices
provided more accurate fire severity estimates. On average, overall accuracy increased from 61% (SAR) to 76%
(optical) for high biomass forests. For low biomass forests (i.e., above ground biomass levels below the L-band
saturation point), radar indices provided comparable results, with overall accuracy being only slightly lower when
compared to optical indices (69% vs. 73%). The joint use of optical and radar indices decreased the estimation
error and reduced misclassification of unburnt forest by 9% for eucalypt and 3% for coniferous forests.
Additional keywords: Landsat, ALOS PALSAR, L-band, radar, accuracy assessment, radar-optical synergy, CBI