Balzarolo M., Peñuelas J., Filella I., Portillo-Estrada M., Ceulemans R. (2018) Assessing ecosystem isoprene emissions by hyperspectral remote sensing. Remote Sensing. 10: 0-0.EnllaçDoi: 10.3390/rs10071086
This study examined the relationship between foliar isoprene emissions, light use efficiency and photochemical reflectance index (PRI) throughout the canopy profile and explored the contribution of xanthophyll cycle pigments versus other carotenoid pigments to the isoprene/PRI relationship. Foliar isoprene emissions within the canopy profile were measured in a high-density poplar plantation in Flanders (Belgium) during the 2016 growing season. The results confirmed that PRI was a promising estimator of isoprene emissions at canopy level. Interestingly, xanthophyll cycle pigments contributed more to isoprene biosynthesis than chlorophyll and drove the isoprene/PRI relationship. The simple independent pigment index and novel defined indices, such as the hyperspectral isoprene index and simple hyperspectral isoprene index, showed promising results and could be suitable estimators of isoprene emissions due to their strong relationship with the xanthophyll pool. © 2018 by the authors.
Fernández-Martínez M., Llusià J., Filella I., Niinemets Ü., Arneth A., Wright I.J., Loreto F., Peñuelas J. (2018) Nutrient-rich plants emit a less intense blend of volatile isoprenoids. New Phytologist. 220: 773-784.EnllaçDoi: 10.1111/nph.14889
The emission of isoprenoids (e.g. isoprene and monoterpenes) by plants plays an important defensive role against biotic and abiotic stresses. Little is known, however, about the functional traits linked to species-specific variability in the types and rates of isoprenoids emitted and about possible co-evolution of functional traits with isoprenoid emission type (isoprene emitter, monoterpene emitter or both). We combined data for isoprene and monoterpene emission rates per unit dry mass with key functional traits (foliar nitrogen (N) and phosphorus (P) concentrations, and leaf mass per area) and climate for 113 plant species, covering the boreal, wet temperate, Mediterranean and tropical biomes. Foliar N was positively correlated with isoprene emission, and foliar P was negatively correlated with both isoprene and monoterpene emission rate. Nonemitting plants generally had the highest nutrient concentrations, and those storing monoterpenes had the lowest concentrations. Our phylogenetic analyses found that the type of isoprenoid emission followed an adaptive, rather than a random model of evolution. Evolution of isoprenoids may be linked to nutrient availability. Foliar N and P are good predictors of the type of isoprenoid emission and the rate at which monoterpenes, and to a lesser extent isoprene, are emitted. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust
Filella I., Zhang C., Seco R., Potosnak M., Guenther A., Karl T., Gamon J., Pallardy S., Gu L., Kim S., Balzarolo M., Fernandez-Martinez M., Penuelas J. (2018) A MODIS photochemical reflectance index (PRI) as an estimator of isoprene emissions in a temperate deciduous forest. Remote Sensing. 10: 0-0.EnllaçDoi: 10.3390/rs10040557
The quantification of isoprene and monoterpene emissions at the ecosystem level with available models and field measurements is not entirely satisfactory. Remote-sensing techniques can extend the spatial and temporal assessment of isoprenoid fluxes. Detecting the exchange of biogenic volatile organic compounds (BVOCs) using these techniques is, however, a very challenging goal. Recent evidence suggests that a simple remotely sensed index, the photochemical reflectance index (PRI), which is indicative of light-use efficiency, relative pigment levels and excess reducing power, is a good indirect estimator of foliar isoprenoid emissions. We tested the ability of PRI to assess isoprenoid fluxes in a temperate deciduous forest in central USA throughout the entire growing season and under moderate and extreme drought conditions. We compared PRI time series calculated with MODIS bands to isoprene emissions measured with eddy covariance. MODIS PRI was correlated with isoprene emissions for most of the season, until emissions peaked. MODIS PRI was also able to detect the timing of the annual peak of emissions, even when it was advanced in response to drought conditions. PRI is thus a promising index to estimate isoprene emissions when it is complemented by information on potential emission. It may also be used to further improve models of isoprene emission under drought and other stress conditions. Direct estimation of isoprene emission by PRI is, however, limited, because PRI estimates LUE, and the relationship between LUE and isoprene emissions can be modified by severe stress conditions. © 2018 by the authors.
Schauman S., Verger A., Filella I., Peñuelas J. (2018) Characterisation of functional-trait dynamics at high spatial resolution in a mediterranean forest from sentinel-2 and ground-truth data. Remote Sensing. 10: 0-0.EnllaçDoi: 10.3390/rs10121874
The characterisation of functional-trait dynamics of vegetation from remotely sensed data complements the structural characterisation of ecosystems. In this study we characterised for the first time the spatial heterogeneity of the intra-annual dynamics of the fraction of absorbed photosynthetically active radiation (FAPAR) as a functional trait of the vegetation in Prades Mediterranean forest in Catalonia, Spain. FAPAR was derived from the Multispectral Instrument (MSI) on the Sentinel-2 satellite and validated by comparison with the ground measurements acquired in June 2017 at the annual peak of vegetation activity. The validation results showed that most of points were distributed along the 1:1 line, with no bias nor scattering: R2 = 0.93, p < 0.05; with a root mean square error of 0.03 FAPAR (4.3%). We classified the study area into nine vegetation groups with different dynamics of FAPAR using a methodology that is objective and repeatable over time. This functional classification based on the annual magnitude (FAPAR-M) and the seasonality (FAPAR-CV) from the data on one year (2016-2017) complements structural classifications. The internal heterogeneity of the FAPAR dynamics in each land-cover type is attributed to the environmental and to the specific species composition variability. A spatial autoregressive (SAR) model for the main type of land cover, evergreen holm oak forest (Quercus ilex), indicated that topographic aspect, slope, height, and the topographic aspect x slope interaction accounted for most of the spatial heterogeneity of the functional trait FAPAR-M, thus improving our understanding of the explanatory factors of the annual absorption of photosynthetically active radiation by the vegetation canopy for this ecosystem. © 2018 by the authors.
Bornez, K., Verger, A., Filella, I., Penuelas, J. (2017) Land surface phenology from Copernicus Global Land time series. 2017 9th International Workshop on the Analysis of Multitemporal Remote Sensing Images, MultiTemp 2017. : 0-0.EnllaçDoi: 10.1109/Multi-Temp.2017.8035262
Farré-Armengol G., Filella I., Llusià J., Peñuelas J. (2017) β-Ocimene, a Key Floral and Foliar Volatile Involved in Multiple Interactions between Plants and Other Organisms. Molecules (Basel, Switzerland). 22: 0-0.EnllaçDoi: 10.3390/molecules22071148
β-Ocimene is a very common plant volatile released in important amounts from the leaves and flowers of many plant species. This acyclic monoterpene can play several biological functions in plants, by potentially affecting floral visitors and also by mediating defensive responses to herbivory. The ubiquity and high relative abundance of β-ocimene in the floral scents of species from most plant families and from different pollination syndromes (ranging from generalism to specialism) strongly suggest that this terpenoid may play an important role in the attraction of pollinators to flowers. We compiled abundant evidence from published studies that supports β-ocimene as a generalist attractant of a wide spectrum of pollinators. We found no studies testing behavioural responses of pollinators to β-ocimene, that could directly demonstrate or deny the function of β-ocimene in pollinator attraction; but several case studies support that the emissions of β-ocimene in flowers of different species follow marked temporal and spatial patterns of emission, which are typical from floral volatile organic compound (VOC) emissions that are involved in pollinator attraction. Furthermore, important β-ocimene emissions are induced from vegetative plant tissues after herbivory in many species, which have relevant functions in the establishment of tritrophic interactions. We thus conclude that β-ocimene is a key plant volatile with multiple relevant functions in plants, depending on the organ and the time of emission. Experimental behavioural studies on pure β-ocimene conducted with pollinating insects will be necessary to prove the assumptions made here.
Peñuelas, J., Sardans, J., Filella, I., Estiarte, M., Llusià, J., Ogaya, R., Carnicer, J., Bartrons, M., Rivas-Ubach, A., Grau, O., Peguero, G., Margalef, O., Pla-Rabés, S., Stefanescu, C., Asensio, D., Preece, C., Liu, L., Verger, A., Barbeta, A., Achotegui-Castells, A., Gargallo-Garriga, A., Sperlich, D., Farré-Armengol, G., Fernández-Martínez, M., Liu, D., Zhang, C., Urbina, I., Camino-Serrano, M., Vives-Ingla, M., Stocker, B.D., Balzarolo, M., Guerrieri, R., Peaucelle, M., Marañón-Jiménez, S., Bórnez-Mejías, K., Mu, Z., Descals, A., Castellanos, A., Terradas, J. (2017) Impacts of global change on Mediterranean forests and their services. Forests. 8: 0-0.EnllaçDoi: 10.3390/f8120463
Zhang, C., Filella, I., Liu, D., Ogaya, R., Llusià, J., Asensio, D., Peñuelas, J. (2017) Photochemical Reflectance Index (PRI) for detecting responses of diurnal and seasonal photosynthetic activity to experimental drought and warming in a Mediterranean shrubland. Remote Sensing. 9: 0-0.EnllaçDoi: 10.3390/rs9111189
Zhang, C., Preece, C., Filella, I., Farré-Armengol, G., Peñuelas, J. (2017) Assessment of the response of photosynthetic activity of Mediterranean evergreen oaks to enhanced drought stress and recovery by using PRI and R690/R630. Forests. 8: 0-0.EnllaçDoi: 10.3390/f8100386
Farré-Armengol, G., Filella, I., Llusia, J., Peñuelas, J. (2016) Bidirectional Interaction between Phyllospheric Microbiotas and Plant Volatile Emissions. Trends in Plant Science. 21: 854-860.EnllaçDoi: 10.1016/j.tplants.2016.06.005
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