Ducatez S., Sayol F., Sol D., Lefebvre L. (2018) Are Urban Vertebrates City Specialists, Artificial Habitat Exploiters, or Environmental Generalists?. Integrative and comparative biology. 58: 929-938.LinkDoi: 10.1093/icb/icy101
Although urbanization is a major threat to biodiversity, some species are able to thrive in cities. This might be because they have specific adaptations to urban conditions, because they are able to cope with artificial habitats in general or because they are generalists that can live in a wide range of conditions. We use the latest version of the IUCN database to distinguish these possibilities in 25,985 species of the four classes of terrestrial vertebrates with the help of phylogenetically controlled methods. We first compare species occurrence in cities with that of the five other artificial habitats recognized by the IUCN and use principal components analyses to ask which of these most resembles cities. We then test whether urban species have a wider habitat breadth than species occurring in other, non-urban, artificial habitats, as well as species that occur only in natural habitats. Our results suggest that the proportion of terrestrial vertebrates that occur in urban environments is small and that, among the species that do occur in cities, the great majority also occur in other artificial habitats. Our data also show that the presence of terrestrial vertebrates in urban habitats is skewed in favor of habitat generalists. In birds and mammals, species occurrence in urban areas is most similar to that of rural gardens, while in reptiles and amphibians, urban areas most resemble pasture and arable land. Our study suggests that cities are likely not unique, as is often thought, and may resemble other types of artificial environments, which urban exploiters can adapt to because of their wide habitat breadth.
Eller C.B., Rowland L., Oliveira R.S., Bittencourt P.R.L., Barros F.V., Da Costa A.C.L., Meir P., Friend A.D., Mencuccini M., Sitch S., Cox P. (2018) Modelling tropical forest responses to drought and El Niño with a stomatal optimization model based on xylem hydraulics. Philosophical Transactions of the Royal Society B: Biological Sciences. 373: 0-0.LinkDoi: 10.1098/rstb.2017.0315
The current generation of dynamic global vegetation models (DGVMs) lacks a mechanistic representation of vegetation responses to soil drought, impairing their ability to accurately predict Earth system responses to future climate scenarios and climatic anomalies, such as El Niño events. We propose a simple numerical approach to model plant responses to drought coupling stomatal optimality theory and plant hydraulics that can be used in dynamic global vegetation models (DGVMs). The model is validated against stand-scale forest transpiration (E) observations from a long-term soil drought experiment and used to predict the response of three Amazonian forest sites to climatic anomalies during the twentieth century. We show that our stomatal optimization model produces realistic stomatal responses to environmental conditions and can accurately simulate how tropical forest E responds to seasonal, and even long-term soil drought. Our model predicts a stronger cumulative effect of climatic anomalies in Amazon forest sites exposed to soil drought during El Niño years than can be captured by alternative empirical drought representation schemes. The contrasting responses between our model and empirical drought factors highlight the utility of hydraulically-based stomatal optimization models to represent vegetation responses to drought and climatic anomalies in DGVMs. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’. © 2018 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.LinkDoi: 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
Fernández-Martínez M., Vicca S., Janssens I.A., Carnicer J., Martín-Vide J., Peñuelas J. (2018) The consecutive disparity index, D: a measure of temporal variability in ecological studies. Ecosphere. 9: 0-0.LinkDoi: 10.1002/ecs2.2527
Temporal variability in ecological processes has attracted the attention of many disciplines in ecology, which has resulted in the development of several quantitative indices. The coefficient of variation (CV = standard deviation × mean−1) is still one of the most commonly used indices to assess temporal variability, despite being known to present several problems on its assessment (e.g., mean dependence or high sensitivity to rare events). The proportional variability (PV) index was developed to solve some of the CV's drawbacks, but, so far, no variability index takes into account the chronological order of the values in time series. In this paper, we introduce the consecutive disparity index (D), a temporal variability index that takes into account the chronological order of the values, assessing the average rate of change between consecutive values. We used computer simulations and empirical data for fruit production in trees, bird counts, and rodent captures to compare the behavior of D, PV, and CV under different scenarios. D was sensitive to changes in temporal autocorrelation in the negative autocorrelation range, and CV and PV were sensitive in the positive autocorrelation range despite not considering the chronological order of the values. The CV, however, was highly dependent on the mean of the time series, while D and PV were not. Our results demonstrate that, like PV, D solves many of the problems of the CV index while taking into account the chronological order of values in time series. The mathematical and statistical features of D make it a suitable index for analyzing temporal variability in a wide range of ecological studies. © 2018 The Authors.
Fernández-Pérez L., Villar-Salvador P., Martínez-Vilalta J., Toca A., Zavala M.A. (2018) Distribution of pines in the Iberian Peninsula agrees with species differences in foliage frost tolerance, not with vulnerability to freezing-induced xylem embolism. Tree Physiology. 38: 507-516.LinkDoi: 10.1093/treephys/tpx171
Drought and frosts are major determinants of plant functioning and distribution. Both stresses can cause xylem embolism and foliage damage. The objective of this study was to analyse if the distribution of six common pine species along latitudinal and altitudinal gradients in Europe is related to their interspecific differences in frost tolerance and to the physiological mechanisms underlying species-specific frost tolerance. We also evaluate if frost tolerance depends on plant water status. We studied survival to a range of freezing temperatures in 2-year-old plants and assessed the percentage loss of hydraulic conductivity (PLC) due xylem embolism formation and foliage damage determined by needle electrolyte leakage (EL) after a single frost cycle to −15 °C and over a range of predawn water potential (ψpd) values. Species experiencing cold winters in their range (Pinus nigra J.F. Arnold, Pinus sylvestris L. and Pinus uncinata Raymond ex A. DC.) had the highest frost survival rates and lowest needle EL and soluble sugar (SS) concentration. In contrast, the pines inhabiting mild or cool winter locations (especially Pinus halepensis Mill. and Pinus pinea L. and, to a lesser extent, Pinus pinaster Ait.) had the lowest frost survival and highest needle EL and SS values. Freezing-induced PLC was very low and differences among species were not related to frost damage. Reduction in ψpd decreased leaf frost damage in P. pinea and P. sylvestris, increased it in P. uncinata and had a neutral effect on the rest of the species. This study demonstrates that freezing temperatures are a major environmental driver for pine distribution and suggests that interspecific differences in leaf frost sensitivity rather than vulnerability to freezing-induced embolism or SS explain pine juvenile frost survival. © The Author(s) 2018. Published by Oxford University Press. All rights reserved.
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.LinkDoi: 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.
Franz D., Acosta M., Altimir N., Arriga N., Arrouays D., Aubinet M., Aurela M., Ayres E., López-Ballesteros A., Barbaste M., Berveiller D., Biraud S., Boukir H., Brown T., Brömmer C., Buchmann N., Burba G., Carrara A., Cescatti A., Ceschia E., Clement R., Cremonese E., Crill P., Darenova E., Dengel S., D'Odorico P., Filippa G., Fleck S., Fratini G., Fuß R., Gielen B., Gogo S., Grace J., Graf A., Grelle A., Gross P., Grönwald T., Haapanala S., Hehn M., Heinesch B., Heiskanen J., Herbst M., Herschlein C., Hörtnagl L., Hufkens K., Ibrom A., Jolivet C., Joly L., Jones M., Kiese R., Klemedtsson L., Kljun N., Klumpp K., Kolari P., Kolle O., Kowalski A., Kutsch W., Laurila T., De Ligne A., Linder S., Lindroth A., Lohila A., Longdoz B., Mammarella I., Manise T., Jiménez S.M., Matteucci G., Mauder M., Meier P., Merbold L., Mereu S., Metzger S., Migliavacca M., Mölder M., Montagnani L., Moureaux C., Nelson D., Nemitz E., Nicolini G., Nilsson M.B., De Beeck M.O.M., Osborne B., Löfvenius M.O., Pavelka M., Peichl M., Peltola O., Pihlatie M., Pitacco A., Pokorný R., Pumpanen J., Ratié C., Rebmann C., Roland M., Sabbatini S., Saby N.P.A., Saunders M., Schmid H.P., Schrumpf M., Sedlák P., Ortiz P.S., Siebicke L., Šigut L., Silvennoinen H., Simioni G., Skiba U., Sonnentag O., Soudani K., Soulé P., Steinbrecher R., Tallec T., Thimonier A., Tuittila E.-S., Tuovinen J.-P., Vestin P., Vincent G., Vincke C., Vitale D., Waldner P., Weslien P., Wingate L., Wohlfahrt G., Zahniser M., Vesala T. (2018) Towards long-Term standardised carbon and greenhouse gas observations for monitoring Europe's terrestrial ecosystems: A review. International Agrophysics. 32: 439-455.LinkDoi: 10.1515/intag-2017-0039
Research infrastructures play a key role in launching a new generation of integrated long-Term, geographically distributed observation programmes designed to monitor climate change, better understand its impacts on global ecosystems, and evaluate possible mitigation and adaptation strategies. The pan-European Integrated Carbon Observation System combines carbon and greenhouse gas (GHG; CO2, CH4, N2O, H2O) observations within the atmosphere, terrestrial ecosystems and oceans. High-precision measurements are obtained using standardised methodologies, are centrally processed and openly available in a traceable and verifiable fashion in combination with detailed metadata. The Integrated Carbon Observation System ecosystem station network aims to sample climate and land-cover variability across Europe. In addition to GHG flux measurements, a large set of complementary data (including management practices, vegetation and soil characteristics) is collected to support the interpretation, spatial upscaling and modelling of observed ecosystem carbon and GHG dynamics. The applied sampling design was developed and formulated in protocols by the scientific community, representing a trade-off between an ideal dataset and practical feasibility. The use of open-Access, high-quality and multi-level data products by different user communities is crucial for the Integrated Carbon Observation System in order to achieve its scientific potential and societal value. © 2018 Daniela Franz et al., published by Sciendo 2018.
Galante M.V., Pinard M.A., Mencuccini M. (2018) Estimating Carbon Avoided from the Implementation of Reduced-Impact Logging in Sabah, Malaysia. International Forestry Review. 20: 58-78.LinkDoi: 10.1505/146554818822824192
The objective of this study was to investigate the design and application of a carbon baseline for commercial timber harvest activities involving conventional timber harvest activities (CNV), relative to reduced-impact logging (RIL) in Sabah, Malaysia. As only RIL is eligible to be practiced in production forests, a baseline of CNV was estimated from the literature. The principle of net present value was applied to the post-harvest accumulation of carbon stocks after RIL to model a conservative 'crediting' baseline. Two areas representing opposite ends of a range of anthropogenic disturbance were sampled, with an old growth lower montane forest, and a lowland severely logged-over dipterocarp forest investigated before-, and two- and three-years after harvest, respectively. Areas impacted by CNV were estimated to contain 12-39% of pre-harvest carbon stock, relative to 57-63% under RIL and estimated to accumulate carbon in the range of 0.68-1.25 tC ha-1 yr1, averaging 14-55 years for recovery; in-line with body of knowledge. While the main limitation was our inability measure CNV directly, a balance of understanding is required for the development of a 'best estimate' using the literature. © 2018 Commonwealth Forestry Association. All rights reserved.
Galiana N., Lurgi M., Claramunt-López B., Fortin M.-J., Leroux S., Cazelles K., Gravel D., Montoya J.M. (2018) The spatial scaling of species interaction networks. Nature Ecology and Evolution. 2: 782-790.LinkDoi: 10.1038/s41559-018-0517-3
Species-area relationships (SARs) are pivotal to understand the distribution of biodiversity across spatial scales. We know little, however, about how the network of biotic interactions in which biodiversity is embedded changes with spatial extent. Here we develop a new theoretical framework that enables us to explore how different assembly mechanisms and theoretical models affect multiple properties of ecological networks across space. We present a number of testable predictions on network-area relationships (NARs) for multi-trophic communities. Network structure changes as area increases because of the existence of different SARs across trophic levels, the preferential selection of generalist species at small spatial extents and the effect of dispersal limitation promoting beta-diversity. Developing an understanding of NARs will complement the growing body of knowledge on SARs with potential applications in conservation ecology. Specifically, combined with further empirical evidence, NARs can generate predictions of potential effects on ecological communities of habitat loss and fragmentation in a changing world. © 2018 The Author(s).
García-Callejas D., Molowny-Horas R., Araújo M.B. (2018) The effect of multiple biotic interaction types on species persistence. Ecology. 99: 2327-2337.LinkDoi: 10.1002/ecy.2465
No species can persist in isolation from other species, but how biotic interactions affect species persistence is still a matter of inquiry. Is persistence more likely in communities with higher proportion of competing species, or in communities with more positive interactions? How do different components of community structure mediate this relationship? We address these questions using a novel simulation framework that generates realistic communities with varying numbers of species and different proportions of biotic interaction types within and across trophic levels. We show that when communities have fewer species, persistence is more likely if positive interactions—such as mutualism and commensalism—are prevalent. In species-rich communities, the disproportionate effect of positive interactions on persistence is diluted and different combinations of biotic interaction types can coexist without affecting persistence significantly. We present the first theoretical examination of how multiple-interaction networks with varying architectures relate to local species persistence, and provide insight about the underlying causes of stability in communities. © 2018 by the Ecological Society of America
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