Vergotti M.J., Fernández-Martínez M., Kefauver S.C., Janssens I.A., Peñuelas J. (2019) Weather and trade-offs between growth and reproduction regulate fruit production in European forests. Agricultural and Forest Meteorology. 279: 0-0.EnllaçDoi: 10.1016/j.agrformet.2019.107711
Some tree species have a highly variable year-to-year pattern of reproduction which has repercussions for the entire ecosystem. Links between meteorological variability, fruit production and crown cover, and trade-offs between reproduction and vegetative growth, remain elusive, despite a long history of research. We explored how meteorological conditions determined variations in fruit production and crown cover and how remotely sensed vegetation indices, such as the enhanced vegetation index (EVI), may be used to characterize the fluctuations in fruit production. We used data for fruit production from six European tree species (Abies alba, Picea abies, Pseudotsuga menziesii, Fagus sylvatica, Quercus petraea and Q. robur) growing in monospecific stands, EVI and seasonal meteorological variables (precipitation and temperature) for 2002–2010. Weather accounted for fruit production better than EVI. Deciduous trees were more responsive to weather than evergreens, most notably to different seasonal temperatures, which were positively correlated mainly with crown cover and fruit production in deciduous species. Our results also suggested different patterns of relationships between fruit production, crown cover and weather, indicating different strategies of resource management. These patterns indicated a possible internal trade-off in evergreens, with resources allocated to either growth or reproduction. In contrast, in deciduous species we found no evidence for such a trade-off between vegetative growth and reproduction. © 2019 Elsevier B.V.
Diaz-de-Quijano M., Kefauver S., Ogaya R., Vollenweider P., Ribas À., Peñuelas J. (2016) Visible ozone-like injury, defoliation, and mortality in two Pinus uncinata stands in the Catalan Pyrenees (NE Spain). European Journal of Forest Research. 135: 687-696.EnllaçDoi: 10.1007/s10342-016-0964-9
Ozone concentrations in the Pyrenees have exceeded the thresholds for forest protection since 1994. We surveyed the severity of visible O3 injuries, crown defoliation, and tree mortality of Pinus uncinata, the dominant species in subalpine forests in this mountain range, along two altitudinal and O3 gradients in the central Catalan Pyrenees and analysed their relationships with the local environmental conditions. The severity of visible O3 injuries increased with increasing mean annual [O3] when summer water availability was high (summer precipitation/potential evapotranspiration above 0.96), whereas higher [O3] did not produce more visible injuries during drier conditions. Mean crown defoliation and tree mortality ranged between 20.4–66.4 and 0.6–29.6 %, respectively, depending on the site. Both were positively correlated with the accumulated O3 exposure during the last 5 years and with variables associated with soil–water availability, which favours greater O3 uptake by increasing stomatal conductance. The results indicate that O3 contributed to the crown defoliation and tree mortality, although further research is clearly warranted to determine the contributions of the multiple stress factors to crown defoliation and mortality in P. uncinata stands in the Catalan Pyrenees. © 2016, Springer-Verlag Berlin Heidelberg.
Kefauver S.C., Filella I., Zhang C., Penuelas J. (2015) Linking OMI HCHO and MODIS PRI satellite data with BVOCS emissions in NE Spain. International Geoscience and Remote Sensing Symposium (IGARSS). 2015-November: 2661-2664.EnllaçDoi: 10.1109/IGARSS.2015.7326360
Volatile organic compounds (VOCs) play several important roles on tropospheric chemical composition. Biogenic VOCs (BVOCs) are the largest source of NMVOCs (non-methane VOCs), accounting for the release of up to 10% of total C fixed by plants in photosynthesis. As isoprene is often the dominant source of atmospheric formaldehyde (HCHO) detected using satellite sensors, it is often correlated directly to satellite HCHO observations without accounting for other HCHO sources. Here we investigate the importance of quantifying monoterpene emissions when linking remotely sensed HCHO vertical columns to terrestrial BVOCs emissions at four different ecosystems in NE Spain where monoterpene-isoprene emissions ratios are known to be unusually high. Average HCHO yield for present monoterpenes was approximately 29% compared to 45% for isoprene. Including monoterpene HCHO yield contributions in total atmospheric HCHO concentrations improved correlations from R2 of 0.35 to 0.66 and R2 of 0.56 to 0.89 when comparing OMI HCHO and MODIS PRI satellite with HCHO field measurements, respectively. © 2015 IEEE.
Kefauver S.C., Filella I., Penuelas J. (2014) Remote sensing of atmospheric biogenic volatile organic compounds (BVOCs) via satellite-based formaldehyde vertical column assessments. International Journal of Remote Sensing. 35: 7519-7542.EnllaçDoi: 10.1080/01431161.2014.968690
Global vegetation is intrinsically linked to atmospheric chemistry and climate, and better understanding vegetation–atmosphere interactions can allow scientists to not only predict future change patterns, but also to suggest future policies and adaptations to mediate vegetation feedbacks with atmospheric chemistry and climate. Improving global and regional estimates of biogenic volatile organic compound (BVOCs) emissions is of great interest for their biological and environmental effects and possible positive and negative feedbacks related to climate change and other vectors of global change. Multiple studies indicate that BVOCs are on the rise, and with near 20 years of global remote sensing of formaldehyde (HCHO), the immediate and dominant BVOC atmospheric oxidation product, the accurate and quantitative linkage of BVOCs with plant ecology, atmospheric chemistry, and climate change is of increasing relevance. The remote sensing of BVOCs, via HCHO in a three step process, suffers from an additive modelling error, but improvements in each of the steps have reduced this error by over a multiplication factor improvement compared to estimates without remote sensing. Differential optical absorption spectroscopy (DOAS) measurement of the HCHO slant columns from spectral absorption properties has been adapted to include the correction of numerous spectral artefacts and intricately refined for each of a series of sensors of increasing spectral and spatial resolution. Conversion of HCHO slant to HCHO vertical columns using air mass factors (AMFs) has been improved with the launch of new sensors and the incorporation of radiative transfer and chemical transport models (CTM). The critical process of linking HCHO to BVOC emissions and filtering non-biogenic emissions to explicitly quantify biogenic emissions has also greatly improved. This critical last step in down-scaling from global satellite coverage to local biogenic emissions now benefits from the increasing precision and near-explicitness of available CTMs as well as the increasing availability of global remote-sensing data sets needed to proportionally assign the HCHO column to different related biogenic (global plant functional type and land cover classifications), atmospheric (dust, aerosols, clouds, other trace gases), climate (temperature, wind, precipitation), and anthropogenic (fire, biomass burning) factors.
Kefauver S.C., Penuelas J., Ribas A., Diaz-De-Quijano M., Ustin S. (2014) Using Pinus uncinata to monitor tropospheric ozone in the Pyrenees. Ecological Indicators. 36: 262-271.EnllaçDoi: 10.1016/j.ecolind.2013.07.024
Field metrics were investigated using the conifer species Pinus uncinata for the biomonitoring of tropospheric ozone in the Pyrenees of Catalonia, Spain. The Ozone Injury Index (OII) was investigated piecewise for improvement as a biomonitoring field metric for using sensitive conifer species to monitor tropospheric ozone across variable environmental conditions. The OII employs a weighted average of visual chlorotic mottling (VI), needle whorl retention (RET), needle length (LGT), and crown death (CD). Of note, VI includes subcomponents VI-Amount (% of symptomatic needles) and VI-Severity (% of chlorotic mottling on symptomatic needles) and RET includes the FWHORL subcomponent (average fraction of needles retained per whorl). All components and subcomponents of the OII correlated better to multiple year ozone exposure compared to single year ozone exposure measurements. VI-Severity and FWHORL modeled over half the variability of the three year average of ambient ozone concentrations (P < 0.0001, R2 = 0.53, RMSE = 2.73). Combining the biomonitoring metrics with GIS models related to landscape-scale variability in plant water relations resulted in considerable improvement in the ozone exposure model explanatory power (P < 0.0001, R2 = 0.90, RMSE = 1.35) including the parameters VI-Amount, VI-Severity, elevation, slope and topographic curvature. © 2013 Elsevier Ltd. All rights reserved.
Kefauver S.C., Penuelas J., Ustin S. (2013) Using topographic and remotely sensed variables to assess ozone injury to conifers in the Sierra Nevada (USA) and Catalonia (Spain). Remote Sensing of Environment. 139: 138-148.EnllaçDoi: 10.1016/j.rse.2013.07.037
The capacity to remotely identify impacts of ozone on conifers in California, USA and Catalonia, Spain was investigated using remote sensing and terrain-driven GIS analyses related to plant water relations and ozone uptake. The Ozone Injury Index (OII) field metric applied to Pinus ponderosa and Pinus jeffreyi in the USA and adapted to Pinus uncinata in Spain included visible chlorotic mottling, needle retention, needle length, and crown depth. Species classifications of AVIRIS and CASI hyperspectral imagery all approached 80% overall accuracy for the target bioindicator species. Remote sensing vegetation indices correlated best with longer-wavelength SWIR indices from the AVIRIS data in California, with the exception of the Photosynthetic Reflectance Index (PRI) correlation with the OII Visual Component (OIIVI), which was also the highest direct correlation in Catalonia. In Catalonia, the OIIVI alone and its subparts correlated better with the CASI data than with the full OII, namely the PRI (R2=0.28, p=0.0044 for OIIVI-amount and R2=0.33 and p=0.0016 for OIIVI-severity). Stepwise regression models of ozone injury developed using remote sensing indices combined with terrain-derived GIS variables were significant for OII in California (R2=0.59, p<0.0001) and in Catalonia (R2=0.68, p<0.0001 for OIIVI). Multiple regression models of ozone injury including a three year average of O3 exposure were significant both with imaging spectroscopy indices alone (R2=0.56, p<0.0001) and with topographic variables added (R2=0.77, p<0.0001) in Catalonia. Applying the multivariate models to image classifications could provide useful maps useful for ozone impact monitoring but requires further validation before being considered operational. © 2013 Elsevier Inc.
Peñuelas J, Filella I, Estiarte M, Ogaya R, Llusià J, Sardans J, Jump A, Carnicer J, Rico L, Garbulsky M, Coll M, Díaz de Quijano M, Seco R, Rivas-Ubach A, Kefauver S, Barbeta A, Achoategui A, Mejía-Chang M, Gallardo A, Farre G, Fernández M, Terradas J (2012) Ecosystemic and biospheric interactions with carbon cycle. In Carbon dioxide budget: processes and tendencies symposium. Universitat Politècnica de Catalunya, May 23-25.
Kefauver S.C., Penuelas J., Ustin S.L. (2012) Applications of hyperspectral remote sensing and GIS for assessing forest health and air pollution. International Geoscience and Remote Sensing Symposium (IGARSS). : 3379-3382.EnllaçDoi: 10.1109/IGARSS.2012.6350696
The objective of this project is the assessment of air pollution impacts on conifer health in the Sierra Nevada of California, USA and the Pyrenees of Catalonia, Spain using remote sensing indices of forest health in conjunction with GIS analyses of the variability various stressors across natural landscape gradients. The Ozone Injury Index (OII) field metric applied to P. ponderosa and P. jeffreyi in the USA and adapted to P. uncinata in Spain included chlorotic mottling, needle retention, needle length, and crown depth. Species-level classifications of AVIRIS and CASI hyperspectral imagery were all near 80% overall accuracy for the target bioindicator species. Combining remote sensing indices with GIS variables related to microsite ozone uptake variability produced improved regressions for Catalonia (R2=0.68, p<0.0001) and California (R2=0.56, p<0.0001). Multiple regression models for the ozone injury visual component (VI) alone performed much better than the full OII in Catalonia combining the remote sensing index PRI and a three year average of ambient ozone (R2=0.56, p<0.0001) and better still when including GIS variables (R2=0.77, p<0.0001). © 2012 IEEE.
Kefauver S.C., Peñuelas J., Ustin S.L. (2012) Improving assessments of tropospheric ozone injury to Mediterranean montane conifer forests in California (USA) and Catalonia (Spain) with GIS models related to plant water relations. Atmospheric Environment. 62: 41-49.EnllaçDoi: 10.1016/j.atmosenv.2012.08.013
The impacts of tropospheric ozone on conifer health in the Sierra Nevada of California, USA, and the Pyrenees of Catalonia, Spain, were measured using field assessments and GIS variables of landscape gradients related to plant water relations, stomatal conductance and hence to ozone uptake. Measurements related to ozone injury included visible chlorotic mottling, needle retention, needle length, and crown depth, which together compose the Ozone Injury Index (OII). The OII values observed in Catalonia were similar to those in California, but OII alone correlated poorly to ambient ozone in all sites. Combining ambient ozone with GIS variables related to landscape variability of plant hydrological status, derived from stepwise regressions, produced models with R 2 = 0.35, p = 0.016 in Catalonia, R 2 = 0.36, p < 0.001 in Yosemite and R 2 = 0.33, p = 0.007 in Sequoia/Kings Canyon National Parks in California. Individual OII components in Catalonia were modeled with improved success compared to the original full OII, in particular visible chlorotic mottling (R 2 = 0.60, p < 0.001). The results show that ozone is negatively impacting forest health in California and Catalonia and also that modeling ozone injury improves by including GIS variables related to plant water relations. Capsule: Models of ozone injury improve significantly when combining ambient ozone mixing ratios and field assessment of ozone impacts with GIS variables related to plant water relations. © 2012 Elsevier Ltd.
Kefauver SC, Peñuelas J, Ustin S (2012) Applications of hyperspectral remote sensing and GIS for assessing forest health and air pollution. Oral presentation at the International Geoscience and Remote Sensing Symposium (IGARSS IEEE), Munich, Germany. July 22-27.
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