Farré-Armengol G., Filella I., Llusia J., Primante C., Peñuelas J. (2015) Enhanced emissions of floral volatiles by Diplotaxis erucoides (L.) in response to folivory and florivory by Pieris brassicae (L.). Biochemical Systematics and Ecology. 63: 51-58.LinkDoi: 10.1016/j.bse.2015.09.022
The main function of floral emissions of volatile organic compounds (VOCs) in entomophilous plants is to attract pollinators. Floral blends, however, can also contain volatile compounds with defensive functions. These defensive volatiles are specifically emitted when plants are attacked by pathogens or herbivores. We characterized the changes in the floral emissions of Diplotaxis erucoides induced by folivory and florivory by Pieris brassicae. Plants were continually subjected to folivory, florivory and folivory + florivory treatments for two days. We measured floral emissions with proton transfer reaction/mass spectroscopy (PTR-MS) at different times during the application of the treatments. The emissions of methanol, ethyl acetate and another compound, likely 3-butenenitrile, increased significantly in response to florivory. Methanol and 3-butenenitrile increased 2.4- and 26-fold, respectively, in response to the florivory treatment. Methanol, 3-butenenitrile and ethyl acetate increased 3-, 100- and 9-fold, respectively, in response to the folivory + florivory treatment. Folivory alone had no detectable effect on floral emissions. All VOC emissions began immediately after attack, with no evidence of delayed induction in any of the treatments. Folivory and florivory had a synergistic effect when applied together, which strengthened the defensive response when the attack was extended to the entire plant. © 2015 Elsevier Ltd.
Fernandez J.D., Lorite J., Bosch J., Gomez J.M. (2015) Variation in the reproductive success of a narrow endemic plant: Effects of geographical distribution, abiotic conditions and pollinator community composition. Basic and Applied Ecology. 16: 375-385.LinkDoi: 10.1016/j.baae.2015.02.006
Geographic variation in reproductive output determines plant distribution. In this study, we investigate the geographic structure and the factors affecting reproductive success throughout the life cycle of the near-threatened crucifer Erysimum popovii across its entire distribution range. We worked in 21 populations, in which we measured fruit set, seed set, seed weight, seed germination in the laboratory, germination time, seedling emergence in the field, seedling survival and fecundity. We also sampled the pollinator assemblages visiting E. popovii at each site, as well as some population characteristics (population size and density, flower density of E. popovii and other co-occurring species, and rainfall). Germination success in the laboratory was very high (range: 0.56-0.98), but seedling emergence in the field was low (0.005-0.32). Beefly visitation rate was positively related to seedling emergence, whereas visitation rate by ants, beetles and other minor pollinator groups was negatively related to fruit set and positively related to germination time. Populations in sites with high density of co-occurring flowers produced fewer fruits. Most variables related to reproductive output varied widely across populations, but this variation did not show a clear regional structure. The low seedling survival may constitute a bottleneck for the recruitment of this species. Overall, less than 0.2% of the ovules produced developed into reproductive individuals. Our results suggest a metapopulation structure for E. popovii. © 2015 Gesellschaft für Ökologie.
Fernandez-Martinez M., Garbulsky M., Penuelas J., Peguero G., Espelta J.M. (2015) Temporal trends in the enhanced vegetation index and spring weather predict seed production in Mediterranean oaks. Plant Ecology. 216: 1061-1072.LinkDoi: 10.1007/s11258-015-0489-1
The extremely year-to-year variable production of seeds (masting) is an extended plant reproductive behaviour important for forest dynamics and food webs. The dependence of these episodes of massive seed production on recently or long-term photosynthesised carbohydrates, however, remains controversial. In this paper, we explore whether vegetation (tree canopy) changes, detected using EVI as a proxy of leaf area and photosynthetic capacity, can provide a reliable estimation of seed production. To complete this analysis, we also explored the effect of weather both in the trends of EVI and in acorn crop size. To this end, we compared the trends of the EVI and acorn production over 10 years (2000–2009) in five stands of Quercus ilex L. in Barcelona (Catalonia, NE Spain). We found that acorn production was mainly driven by a combination of: (i) a minimum initial threshold in the EVI values, (ii) an increase in EVI in the 9 ± 4 months prior to reproduction, and (iii) appropriate weather conditions (low water stress) during spring. These results indicated, apparently for the first time, that reproduction in masting species could be detected and partly predicted by remotely sensed vegetative indices. Our results suggested that this particular reproductive behaviour in Mediterranean oaks was driven by a combination of two factors, i.e. good and improving vegetation conditions, as shown by a minimum initial threshold and the increase in EVI needed for large seed crops, and the need of wet weather conditions during spring. Moreover, our results fully supported recent studies that have associated short-term photosynthate production with seed production. © 2015, Springer Science+Business Media Dordrecht.
Fernández-Martínez M., Vicca S., Janssens I.A., Sardans J., Luyssaert S., Campioli M., Chapin F.S., Ciais P., Malhi Y., Obersteiner M., Papale D., Piao S.L., Reichstein M., Rodà F., Peñuelas J. (2015) Reply to 'Uncertain effects of nutrient availability on global forest carbon balance' and 'Data quality and the role of nutrients in forest carbon-use efficiency'. Nature Climate Change. 5: 960-961.LinkDoi: 10.1038/nclimate2794
[No abstract available]
Fu Y.H., Zhao H., Piao S., Peaucelle M., Peng S., Zhou G., Ciais P., Huang M., Menzel A., Peñuelas J., Song Y., Vitasse Y., Zeng Z., Janssens I.A. (2015) Declining global warming effects on the phenology of spring leaf unfolding. Nature. 526: 104-107.LinkDoi: 10.1038/nature15402
Earlier spring leaf unfolding is a frequently observed response of plants to climate warming. Many deciduous tree species require chilling for dormancy release, and warming-related reductions in chilling may counteract the advance of leaf unfolding in response to warming. Empirical evidence for this, however, is limited to saplings or twigs in climate-controlled chambers. Using long-term in situ observations of leaf unfolding for seven dominant European tree species at 1,245 sites, here we show that the apparent response of leaf unfolding to climate warming (S T, expressed in days advance of leaf unfolding per °C warming) has significantly decreased from 1980 to 2013 in all monitored tree species. Averaged across all species and sites, S T decreased by 40% from 4.0 ± 1.8 days °C-1 during 1980-1994 to 2.3 ± 1.6 days °C-1 during 1999-2013. The declining S T was also simulated by chilling-based phenology models, albeit with a weaker decline (24-30%) than observed in situ. The reduction in S T is likely to be partly attributable to reduced chilling. Nonetheless, other mechanisms may also have a role, such as 'photoperiod limitation' mechanisms that may become ultimately limiting when leaf unfolding dates occur too early in the season. Our results provide empirical evidence for a declining S T, but also suggest that the predicted strong winter warming in the future may further reduce S T and therefore result in a slowdown in the advance of tree spring phenology. © 2015 Macmillan Publishers Limited. All rights reserved.
Garcia-Forner N., Adams H.D., Sevanto S., Collins A.D., Dickman L.T., Hudson P.J., Zeppel M.J., Jenkins M.W., Powers H., Martinez-Vilalta J., Mcdowell N.G. (2015) Responses of two semiarid conifer tree species to reduced precipitation and warming reveal new perspectives for stomatal regulation. Plant, Cell and Environment. : 0-0.LinkDoi: 10.1111/pce.12588
Relatively anisohydric species are predicted to be more predisposed to hydraulic failure than relatively isohydric species, as they operate with narrower hydraulic safety margins. We subjected co-occurring anisohydric Juniperus monosperma and isohydric Pinus edulis trees to warming, reduced precipitation, or both, and measured their gas exchange and hydraulic responses. We found that reductions in stomatal conductance and assimilation by heat and drought were more frequent during relatively moist periods, but these effects were not exacerbated in the combined heat and drought treatment. Counter to expectations, both species exhibited similar gs temporal dynamics in response to drought. Further, whereas P.edulis exhibited chronic embolism, J.monosperma showed very little embolism due to its conservative stomatal regulation and maintenance of xylem water potential above the embolism entry point. This tight stomatal control and low levels of embolism experienced by juniper refuted the notion that very low water potentials during drought are associated with loose stomatal control and with the hypothesis that anisohydric species are more prone to hydraulic failure than isohydric species. Because direct association of stomatal behaviour with embolism resistance can be misleading, we advocate consideration of stomatal behaviour relative to embolism resistance for classifying species drought response strategies. © 2015 John Wiley & Sons Ltd.
Gargallo-Garriga A., Sardans J., Perez-Trujillo M., Oravec M., Urban O., Jentsch A., Kreyling J., Beierkuhnlein C., Parella T., Penuelas J. (2015) Warming differentially influences the effects of drought on stoichiometry and metabolomics in shoots and roots. New Phytologist. : 0-0.LinkDoi: 10.1111/nph.13377
Plants in natural environments are increasingly being subjected to a combination of abiotic stresses, such as drought and warming, in many regions. The effects of each stress and the combination of stresses on the functioning of shoots and roots have been studied extensively, but little is known about the simultaneous metabolome responses of the different organs of the plant to different stresses acting at once. We studied the shift in metabolism and elemental composition of shoots and roots of two perennial grasses, Holcus lanatus and Alopecurus pratensis, in response to simultaneous drought and warming. These species responded differently to individual and simultaneous stresses. These responses were even opposite in roots and shoots. In plants exposed to simultaneous drought and warming, terpenes, catechin and indole acetic acid accumulated in shoots, whereas amino acids, quinic acid, nitrogenous bases, the osmoprotectants choline and glycine betaine, and elements involved in growth (nitrogen, phosphorus and potassium) accumulated in roots. Under drought, warming further increased the allocation of primary metabolic activity to roots and changed the composition of secondary metabolites in shoots. These results highlight the plasticity of plant metabolomes and stoichiometry, and the different complementary responses of shoots and roots to complex environmental conditions. © 2015 New Phytologist Trust.
Gibb H., Sanders N.J., Dunn R.R., Watson S., Photakis M., Abril S., Andersen A.N., Angulo E., Armbrecht I., Arnan X., Baccaro F.B., Bishop T.R., Boulay R., Castracani C., Del Toro I., Delsinne T., Diaz M., Donoso D.A., Enriquez M.L., Fayle T.M., Feener D.H., Fitzpatrick M.C., Gomez C., Grasso D.A., Groc S., Heterick B., Hoffmann B.D., Lach L., Lattke J., Leponce M., Lessard J.-P., Longino J., Lucky A., Majer J., Menke S.B., Mezger D., Mori A., Munyai T.C., Paknia O., Pearce-Duvet J., Pfeiffer M., Philpott S.M., De Souza J.L.P., Tista M., Vasconcelos H.L., Vonshak M., Parr C.L. (2015) Climate mediates the effects of disturbance on ant assemblage structure. Proceedings of the Royal Society B: Biological Sciences. 282: 0-0.LinkDoi: 10.1098/rspb.2015.0418
Many studies have focused on the impacts of climate change on biological assemblages, yet little is known about howclimate interacts with other major anthropogenic influences on biodiversity, such as habitat disturbance. Using a unique global database of 1128 local ant assemblages, we examined whether climate mediates the effects of habitat disturbance on assemblage structure at a global scale. Species richness and evenness were associated positively with temperature, and negatively with disturbance. However, the interaction among temperature, precipitation and disturbance shaped species richness and evenness. The effectwas manifested through a failure of species richness to increase substantially with temperature in transformed habitats at low precipitation. At low precipitation levels, evenness increased with temperature in undisturbed sites, peaked at medium temperatures in disturbed sites and remained low in transformed sites. In warmer climates with lower rainfall, the effects of increasing disturbance on species richness and evenness were akin to decreases in temperature of up to 98C. Anthropogenic disturbance and ongoing climate change may interact in complicated ways to shape the structure of assemblages, with hot, arid environments likely to be at greatest risk. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
Gil-Tena A., De Caceres M., Ernoult A., Butet A., Brotons L., Burel F. (2015) Agricultural landscape composition as a driver of farmland bird diversity in Brittany (NW France). Agriculture, Ecosystems and Environment. 205: 79-89.LinkDoi: 10.1016/j.agee.2015.03.013
In agriculture-dominated landscapes, agricultural intensification and associated landscape homogenization have caused large declines in farmland biodiversity. This study was aimed at determining how agricultural landscape composition drives community diversity and composition of farmland birds in the characteristic bocage landscape in Brittany (NW France) on a broad scale. Using bird atlas data from the region (2004-2008; 10. ×. 10. km), we analyzed the importance of different components of agricultural landscape composition (types of crops, amount of semi-natural covers and elements, and artificial lands) on the alpha diversity and beta diversity of farmland birds of different functional groups, defined depending on the degree of farmland specialization and ecological requirements.Agricultural landscape composition features explained a small amount of variation in alpha and beta diversity, particularly for specialists and residents. Cereal crops were negatively correlated with alpha diversity of all the functional groups considered whereas rotational grasslands were negatively associated with migrant and insectivorous alpha diversity. Although shrublands are not common in Brittany, they were positively associated with the occurrence of some species and particularly with alpha diversity of all the functional groups but specialists and residents. At the spatial grain of analysis, community composition was mainly driven by a gradient of alteration of the bocage.To conclude, we claim for the consideration of regional idiosyncrasies in far-reaching planning schemes to prevent future biodiversity loss in agriculture-dominated landscapes due to agricultural intensification. In view of the observed large-scale trends gathered from atlas data analysis and the small amount of explained variation, we also advocate for subsequent finer scale bespoke surveys to determine the biodiversity status associated with the valuable bocage agricultural landscape. © 2015 Elsevier B.V.
Girado-Beltran P., Andreu J., Pino J. (2015) Exploring changes in the invasion pattern of alien flora in Catalonia (NE of Spain) from large datasets. Biological Invasions. 17: 3015-3028.LinkDoi: 10.1007/s10530-015-0930-3
Plant invasions are characterized by their dynamism, but they are generally described at a precise time step due to the dearth of datasets on species distribution across time. In this paper we employed specific alien plant databases to assess the factors associated with recent changes in plant invasion patterns in Catalonia from two perspectives, site and species. We gathered records of neophyte plant species per 10-km UTM cell from two spatially coincident large-scale datasets collected in 1989 and 2012. We estimated the richness increase of species per UTM cell and the range size increase of each species (i.e. the number of occupied UTM cells) between these dates. We then evaluated the association of richness increase with geographic, climatic and landscape factors, and that of range size increase with species traits and the characteristics of the introduction event. We found 401 species, 291 recorded up to 1989 and 110 afterwards. Richness increase was concentrated in new hotspots compared to those observed in 1989, suggesting that patterns of susceptibility to plant invasion have changed in recent decades. Climatic factors were the most important in determining the large-scale pattern of alien species, with the highest values of species richness increase in warmest and rainiest areas. Range size increase of each alien species was mostly explained by the historical range size, the introduction pathway, namely unintentional introductions and the interaction between habitat and the minimum residence time. These factors were more influential than species traits in the recent spread of alien plant species across the region. © 2015, Springer International Publishing Switzerland.
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