Experimental evidence for inherent lévy search behaviour in foraging animals

Kolzsch A., Alzate A., Bartumeus F., De Jager M., Weerman E.J., Hengeveld G.M., Naguib M., Nolet B.A., Van De Koppel J. (2015) Experimental evidence for inherent lévy search behaviour in foraging animals. Proceedings of the Royal Society B: Biological Sciences. 282: 0-0.
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Doi: 10.1098/rspb.2015.0424

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Recently, Lévy walks have been put forward as a new paradigm for animal search and many cases have been made for its presence in nature. However, it remains debated whether Lévy walks are an inherent behavioural strategy or emerge from the animal reacting to its habitat. Here, we demonstrate signatures of Lévy behaviour in the search movement of mud snails (Hydrobia ulvae) based on a novel, direct assessment of movement properties in an experimental set-up using different food distributions. Our experimental data uncovered clusters of small movement steps alternating with long moves independent of food encounter and landscape complexity. Moreover, size distributions of these clusters followed truncated power laws. These two findings are characteristic signatures of mechanisms underlying inherent Lévy-like movement. Thus, our study provides clear experimental evidence that such multi-scale movement is an inherent behaviour rather than resulting from the animal interacting with its environment. © 2015 The Author(s) Published by the Royal Society.

Llegeix més

Variations in functional diversity in snowbed plant communities determining snowbed continuity

Komac B., Pladevall C., Penuelas J., Conesa J.V., Domenech M. (2015) Variations in functional diversity in snowbed plant communities determining snowbed continuity. Plant Ecology. : 0-0.
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Doi: 10.1007/s11258-015-0506-4

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Snowbed habitats are home to plant species that have adapted to particular environmental conditions (i.e. long-lasting snow cover and short growing seasons). The presence of most of these species is dependent on a long period of snow cover and so their conservation may well depend in the future on their ability to adapt to the effects of climate change. The aim of this study was to assess the persistence of snowbed communities using functional trait and functional diversity indices. We used data for plant species abundances from 32 snowbeds in Andorra (Pyrenees) classified according to certain environmental variables (elevation, exposure, soil type and temperature) and snow cover duration. Nine functional traits were used to evaluate the functional diversity, which was characterised as consisting of functional richness, functional evenness, functional dispersion, functional divergence and the community-weighted mean trait values. In two snowbeds, plant traits were also recorded and variation analysed along a snowmelt gradient. We found that snowbed specialist species had functional traits that were well adapted to the particular abiotic conditions of snowbed habitats but that there was a predominance of the functional traits of grass species in species originating in neighbouring communities. We found less functional richness, fewer strategies and lower competitive ability in the adapted species as the severity of the abiotic conditions increased. Snowbed specialist species appear to be less sensitive to the length of the growing season than species from neighbouring communities. Our results suggest that non-specialist species will tend to appear more frequently in those snowbed habitats affected by the reduction in snow cover duration. © 2015 Springer Science+Business Media Dordrecht

Llegeix més

Development of an ISO-standard for the preservation of geospatial data and metadata: ISO 19165

Kresse W., Pau J.M. (2015) Development of an ISO-standard for the preservation of geospatial data and metadata: ISO 19165. Photogrammetrie, Fernerkundung, Geoinformation. 2015: 449-456.
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Doi: 10.1127/pfg/2015/0278

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Most of the paper maps produced a century ago are still very accessible in cartographic libraries preserved by the producer. It is our present obligation to guarantee the preservation of digital geospatial data today and allow for digital cartographic accessibility one century into the future. In addition, there is an increasing demand for older maps that goes beyond pure historical interest motivated by the study of dynamic problems such as impacts of the climate change, human activities and sustainability. The long-term preservation of large volumes of geospatial data in a uniform way still remains an unsolved question. A systematic solution has been demanded by National Mapping and Archival Agencies in Europe and North America. One year ago the ISO/TC 211 "Geographic information /Geomatics" published a New Work Item Proposal (NWIP) named ISO 19165 "Preservation of digital data and metadata" accompanied by a Working Draft document. The proposed standard is built upon the principles laid down in the ISO 14721 "Open Archival Information Systems" and upon thedatamodehofthe ISO 19115-1 "Metadata - Part 1: Fundamentals". This article reports on the specialization of both standards for the purpose of archiving of geospatial data and asks for contributions to the ISO 19165 under development. © 2015 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.

Llegeix més

Increased sensitivity to climate change in disturbed ecosystems

Kroel-Dulay G., Ransijn J., Schmidt I.K., Beier C., De Angelis P., De Dato G., Dukes J.S., Emmett B., Estiarte M., Garadnai J., Kongstad J., Kovacs-Lang E., Larsen K.S., Liberati D., Ogaya R., Riis-Nielsen T., Smith A.R., Sowerby A., Tietema A., Penuelas J. (2015) Increased sensitivity to climate change in disturbed ecosystems. Nature Communications. 6: 0-0.
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Doi: 10.1038/ncomms7682

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Human domination of the biosphere includes changes to disturbance regimes, which push many ecosystems towards early-successional states. Ecological theory predicts that early-successional ecosystems are more sensitive to perturbations than mature systems, but little evidence supports this relationship for the perturbation of climate change. Here we show that vegetation (abundance, species richness and species composition) across seven European shrublands is quite resistant to moderate experimental warming and drought, and responsiveness is associated with the dynamic state of the ecosystem, with recently disturbed sites responding to treatments. Furthermore, most of these responses are not rapid (2-5 years) but emerge over a longer term (7-14 years). These results suggest that successional state influences the sensitivity of ecosystems to climate change, and that ecosystems recovering from disturbances may be sensitive to even modest climatic changes. A research bias towards undisturbed ecosystems might thus lead to an underestimation of the impacts of climate change. © 2015 Macmillan Publishers Limited. All rights reserved.

Llegeix més

Random processes and phylogenetic loss caused by plant invasions

Lapiedra O., Sol D., Traveset A., Vila M. (2015) Random processes and phylogenetic loss caused by plant invasions. Global Ecology and Biogeography. : 0-0.
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Doi: 10.1111/geb.12310

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Aim: Although biological invasions represent a major cause of biodiversity loss, the actual mechanisms driving species extinctions remain insufficiently understood. Here we investigate the role of three processes as drivers of phylogenetic loss in invaded local plant communities, namely the 'biotic resistance', 'environmental filtering' and 'functional equivalence' hypotheses. Location: Balearic Islands (western Mediterranean). Methods: We quantified the phylogenetic diversity and structure of 109 pairs of invaded and non-invaded local plant communities from two Mediterranean islands. Each pair contained one control plot and one plot invaded either by the deciduous tree Ailanthus altissima, the succulent subshrubs Carpobrotus spp. or the pseudoannual geophyte Oxalis pes-caprae. We combined generalized linear models, analyses of phylogenetic community structure and generalized linear mixed models using a Markov chain Monte Carlo technique (MCMCglmm) to contrast the 'biotic resistance', 'environmental filtering' and 'functional equivalence' hypotheses. Results: While the phylogenetic structure of the non-invaded communities was not more clustered or overdispersed than expected by chance, minimum phylogenetic distance to the invasive species increased in invaded assemblages, in which the magnitude of phylogenetic diversity loss ranged from 6 to 37% depending on the invader's identity. Invader or island identity did not explain the probabilities of native species becoming locally extinct. Rather, the likelihood of extinction was mainly explained by species abundance, with scarcer species exhibiting a higher chance of becoming locally extinct. Species identity explained a small fraction of the variation in extinction risk (12%), independently of each species' evolutionary history. Main conclusions: The most relevant driver of local extinction is a stochastic process where less abundant species tend to disappear more frequently irrespective of their evolutionary history. This has strong implications for conservation because it suggests that in the study region the invaders are unlikely to drive regional and global extinctions except in cases where the native species is already rare. © 2015 John Wiley & Sons Ltd.

Llegeix més

Contrasting impacts of continuous moderate drought and episodic severe droughts on the aboveground-biomass increment and litterfall of three coexisting Mediterranean woody species

Liu D., Ogaya R., Barbeta A., Yang X., Peñuelas J. (2015) Contrasting impacts of continuous moderate drought and episodic severe droughts on the aboveground-biomass increment and litterfall of three coexisting Mediterranean woody species. Global Change Biology. 21: 4196-4209.
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Doi: 10.1111/gcb.13029

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Climate change is predicted to increase the aridity in the Mediterranean Basin and severely affect forest productivity and composition. The responses of forests to different timescales of drought, however, are still poorly understood because extreme and persistent moderate droughts can produce nonlinear responses in plants. We conducted a rainfall-manipulation experiment in a Mediterranean forest dominated by Quercus ilex, Phillyrea latifolia, and Arbutus unedo in the Prades Mountains in southern Catalonia from 1999 to 2014. The experimental drought significantly decreased forest aboveground-biomass increment (ABI), tended to increase the litterfall, and decreased aboveground net primary production throughout the 15 years of the study. The responses to the experimental drought were highly species-specific. A. unedo suffered a significant reduction in ABI, Q. ilex experienced a decrease during the early experiment (1999-2003) and in the extreme droughts of 2005-2006 and 2011-2012, and P. latifolia was unaffected by the treatment. The drought treatment significantly increased branch litterfall, especially in the extremely dry year of 2011, and also increased overall leaf litterfall. The drought treatment reduced the fruit production of Q. ilex, which affected seedling recruitment. The ABIs of all species were highly correlated with SPEI in early spring, whereas the branch litterfalls were better correlated with summer SPEIs and the leaf and fruit litterfalls were better correlated with autumn SPEIs. These species-specific responses indicated that the dominant species (Q. ilex) could be partially replaced by the drought-resistant species (P. latifolia). However, the results of this long-term study also suggest that the effect of drought treatment has been dampened over time, probably due to a combination of demographic compensation, morphological and physiological acclimation, and epigenetic changes. However, the structure of community (e.g., species composition, dominance, and stand density) may be reordered when a certain drought threshold is reached. © 2015 John Wiley & Sons Ltd.

Llegeix més

Expanding the tephrostratigraphical framework for the South Shetland Islands, Antarctica, by combining compositional and textural tephra characterisation

Liu E.J., Oliva M., Antoniades D., Giralt S., Granados I., Pla-Rabes S., Toro M., Geyer A. (2015) Expanding the tephrostratigraphical framework for the South Shetland Islands, Antarctica, by combining compositional and textural tephra characterisation. Sedimentary Geology. : 0-0.
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Doi: 10.1016/j.sedgeo.2015.08.002

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Tephra layers preserved in lake sedimentary sequences provide valuable isochrons with which to synchronise palaeoclimatic records. However, in regions where tephra inputs are dominated by a single volcanic source, overlapping chemical compositions can preclude unambiguous correlation of tephra layers. In this study, we characterise multiple visible (macrotephra) layers within sedimentary sequences from three lakes in Byers Peninsula, Antarctica. By combining compositional analyses with additional constraints from textural componentry, we identify three distinct tephra isochrons-T1, T2, and T3-each with distinct textural properties. The relative proportion of glassy compared to crystal-rich grains varies from ~. 50% (T3) to ~. 3% (T1) of the total sample. Although the proportion of dense to vesicular grains differs only slightly between all sampled tephra layers, the dominant vesicle shape varies from spherical (T3) to irregular and polylobate (T1/T2). These textural differences can be related to variations in the eruptive processes occurring at the Deception Island source volcano. This study highlights the efficacy of a correlative approach based on both chemical and physical tephra properties for deconvolving the tephra stratigraphy in regions where chemical compositions are non-unique. © 2015 Elsevier B.V.

Llegeix més

Climate-induced die-offaffects plant-soil-microbe ecological relationship and functioning

Lloret F., Mattana S., Yuste J.C. (2015) Climate-induced die-offaffects plant-soil-microbe ecological relationship and functioning. FEMS Microbiology Ecology. 91: 0-0.
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Doi: 10.1093/femsec/iu014

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This study reports the relationship between the diversity and functioning of fungal and bacterial soil communities with vegetation in Mediterranean woodland that experienced severe die-offafter a drought episode. Terminal restriction fragment length polymorfism (TRFLP) was used to describe microbial community structure and diversity five years after the episode in different habitats (Juniperus woodland, shrubland, grassland), when the vegetation had not yet recovered. Vegetation diversity was positively related to TRF bacterial richness under unaffected canopies and was higher in diverse grassland. Fungal TRF richness correlated with vegetation type, being greater in Juniperus woodland. Microbial respiration increased in grassland, whereas microbial biomass, estimated from soil substrate-induced respiration (SIR), decreased with bacterial diversity. Die-offincreased bacterial richness and changed bacterial composition, particularly in Juniperus woodland, where herbaceous species increased, while fungal diversity was reduced in Juniperus woodland. Die-offincreased microbial respiration rates. The impact on vegetation from extreme weather episodes spread to microbial communities by modifying vegetation composition and litter quantity and quality, particularly as a result of the increase in herbaceous species. Our results suggest that climate-induced die-offtriggers significant cascade effects on soil microbial communities, which may in turn further influence ecosystem C dynamics. © FEMS 2014. All rights reserved.

Llegeix més

Photosynthesis, stomatal conductance and terpene emission response to water availability in dry and mesic Mediterranean forests

Llusia J., Roahtyn S., Yakir D., Rotenberg E., Seco R., Guenther A., Peñuelas J. (2015) Photosynthesis, stomatal conductance and terpene emission response to water availability in dry and mesic Mediterranean forests. Trees - Structure and Function. : 1-11.
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Doi: 10.1007/s00468-015-1317-x

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Key message: Warmer summer conditions result in increased terpene emissions except under severe drought, in which case they strongly decrease.Abstract: Water stress results in a reduction of the metabolism of plants and in a reorganization of their use of resources geared to survival. In the Mediterranean region, periods of drought accompanied by high temperatures and high irradiance occur in summer. Plants have developed various mechanisms to survive in these conditions by resisting, tolerating or preventing stress. We used three typical Mediterranean tree species in Israel, Pinus halepensis L., Quercus calliprinos and Quercus ithaburensis Webb, as models for studying some of these adaptive mechanisms. We measured their photosynthetic rates (A), stomatal conductance (gs), and terpene emission rates during spring and summer in a geophysical gradient from extremely dry to mesic from Yatir (south, arid) to Birya (north, moist) with intermediate conditions in Solelim. A and gs of P. halepensis were threefold higher in Birya than in Yatir where they remained very low both seasons. Quercus species presented 2–3-fold higher A and gs but with much more variability between seasons, especially for Q. ithaburensis with A and gs that decreased 10–30-fold from spring to summer. Terpene emission rates for pine were not different regionally in spring but they were 5–8-fold higher in Birya than in Yatir in summer (P < 0.05). Higher emissions were also observed in Solelim for the drought resistant Q. ithaburensis (P < 0.001) but not for Q. calliprinos. α-Pinene followed by limonene and 3-carene were the dominant terpenes. Warmer summer conditions result in increased Terpene emission rates except under severe drought, in which case they strongly decrease. © 2015 Springer-Verlag Berlin Heidelberg

Llegeix més

A comparison of models for quantifying growth and standing carbon in UK Scots pine forests

Lonsdale J., Xenakis G., Mencuccini M., Perks M. (2015) A comparison of models for quantifying growth and standing carbon in UK Scots pine forests. IForest. 8: 596-605.
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Doi: 10.3832/ifor1403-008

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Scots pine is the most abundant native conifer in the UK. A stand level dynamic growth (SLeDG) model is parametrised for British Scots pine stands for the first time. This model predicts stands annually based on their current state, and allows for changes in forest management. Stand growth and carbon storage predictions using this model were compared with those of the yield look-up package Forest Yield, and a process-based model (3PGN). Predictions were compared graphically over an 100 year rotation, and strengths and weaknesses of each were considered. The SLeDG parametrisation provided forecasts of Scots pine growth with percentage mean absolute difference

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