Rooting big and deep rapidly: the ecological roots of pine species distribution in southern Europe

Andivia E., Zuccarini P., Grau B., de Herralde F., Villar-Salvador P., Savé R. (2019) Rooting big and deep rapidly: the ecological roots of pine species distribution in southern Europe. Trees - Structure and Function. 33: 293-303.
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Doi: 10.1007/s00468-018-1777-x

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Key message: The rapid production of a large, deep root system during seedling establishment is critical for pines to colonize dry Mediterranean locations. Abstract: Root properties can influence plant drought resistance, and consequently plant species distribution. Root structure strongly varies across biomes partly as a result of phylogeny. However, whether the spatial distribution of phylogenetically close plant species is linked to differences in root properties remains unclear. We examined whether root properties mediate the strong correlation between summer drought intensity and the spatial segregation of pine species native to southern Europe. For this, we compared the seedling root growth and structure of five ecologically distinct pine species grown in 360 L rhizotrons for 19 months under typical hot and dry Mediterranean conditions. We studied the mountain and boreo-alpine pines Pinus sylvestris and Pinus nigra, and the Mediterranean pines Pinus pinaster, Pinus pinea, and Pinus halepensis. Mediterranean pines formed deep roots faster than mountain pines, their shoots and roots grew faster and had higher root growth, especially P. halepensis, at low air temperature. By the end of the study, Mediterranean pines had larger root systems than mountain pines. Neither distribution of root mass with depth nor root-to-shoot mass ratio varied significantly among species. Across species, minimal annual rainfall to which species are exposed in their range related negatively to root growth but positively to specific root length and the time needed for roots to reach a depth of 40 cm. This study highlights the importance of root growth as a driver of pine distribution in southern Europe and suggests that rapidly producing a large, deep root system may be a key attribute for pines to colonize dry Mediterranean locations. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.

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Belowground biota responses to maize biochar addition to the soil of a Mediterranean vineyard

Andrés P., Rosell-Melé A., Colomer-Ventura F., Denef K., Cotrufo M.F., Riba M., Alcañiz J.M. (2019) Belowground biota responses to maize biochar addition to the soil of a Mediterranean vineyard. Science of the Total Environment. 660: 1522-1532.
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Doi: 10.1016/j.scitotenv.2019.01.101

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Biochar is a high carbon material resulting from biomass pyrolysis that, when applied to croplands, can increase soil carbon and soil water retention. Both effects are of critical importance in semi-arid regions, where carbon decline and desertification are the main drivers of soil degradation. Since most environmental services provided by soil are mediated by belowground biota, effects of biochar on soil microbial and invertebrate communities must be evaluated under field conditions before its agricultural application can be recommended. We tested maize biochar for its mid-term effect on soil microbes and micro-arthropods of a Mediterranean vineyard. We applied biochar to three field plots with neutral sandy loam soils at a dose of 5 Mg ha−1. During two years, we monitored the abundance of functional groups of soil micro-arthropods and estimated the biomass of soil microbial groups. We also analyzed the δ13C value of microbial PLFA biomarkers to determine biochar-C utilization by each microbial group taking advantage of the δ13C natural abundance differences between the applied biochar and the soil. Biochar addition significantly reduced soil microbial biomass but did not alter the functional microbial diversity nor the abundance or biodiversity of soil micro-arthropods. The contribution of biochar-C to the diet of most microbial groups was very low through the monitoring period. However, two gram-negative bacterial groups increased their biochar-derived carbon uptake under extreme soil dryness, which suggests that biochar-C might help soil microbes to overcome the food shortage caused by drought. The decrease in microbial biomass observed in our experiment and the concomitant decrease of SOM mineralization could contribute to the carbon sequestration potential of Mediterranean soils after biochar addition. © 2019 Elsevier B.V.

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The physics and ecology of mining carbon dioxide from the atmosphere by ecosystems

Baldocchi D., Penuelas J. (2019) The physics and ecology of mining carbon dioxide from the atmosphere by ecosystems. Global Change Biology. : 0-0.
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Doi: 10.1111/gcb.14559

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Reforesting and managing ecosystems have been proposed as ways to mitigate global warming and offset anthropogenic carbon emissions. The intent of our opinion piece is to provide a perspective on how well plants and ecosystems sequester carbon. The ability of individual plants and ecosystems to mine carbon dioxide from the atmosphere, as defined by rates and cumulative amounts, is limited by laws of physics and ecological principles. Consequently, the rates and amount of net carbon uptake are slow and low compared to the rates and amounts of carbon dioxide we release by fossil fuels combustion. Managing ecosystems to sequester carbon can also cause unintended consequences to arise. In this paper, we articulate a series of key take-home points. First, the potential amount of carbon an ecosystem can assimilate on an annual basis scales with absorbed sunlight, which varies with latitude, leaf area index and available water. Second, efforts to improve photosynthesis will come with the cost of more respiration. Third, the rates and amount of net carbon uptake are relatively slow and low, compared to the rates and amounts and rates of carbon dioxide we release by fossil fuels combustion. Fourth, huge amounts of land area for ecosystems will be needed to be an effective carbon sink to mitigate anthropogenic carbon emissions. Fifth, the effectiveness of using this land as a carbon sink will depend on its ability to remain as a permanent carbon sink. Sixth, converting land to forests or wetlands may have unintended costs that warm the local climate, such as changing albedo, increasing surface roughness or releasing other greenhouse gases. We based our analysis on 1,163 site-years of direct eddy covariance measurements of gross and net carbon fluxes from 155 sites across the globe. © 2018 John Wiley & Sons Ltd

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Contrasting effects of fog frequency on the radial growth of two tree species in a Mediterranean-temperate ecotone

Barbeta A., Camarero J.J., Sangüesa-Barreda G., Muffler L., Peñuelas J. (2019) Contrasting effects of fog frequency on the radial growth of two tree species in a Mediterranean-temperate ecotone. Agricultural and Forest Meteorology. 264: 297-308.
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Doi: 10.1016/j.agrformet.2018.10.020

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The performance and persistence of rear-edge tree populations are relevant issues for conserving biodiversity because these stands harbor high intraspecific biodiversity and play a key role during periods of climate change. The occurrence of these populations is associated with the influence of heterogeneous topography, creating suitable refugia with regionally rare environmental conditions. Climate is changing at a global-scale, but little is known about the long-term impact on local climatic singularities and the associated taxa. We analyzed tree-ring growth chronologies of the two species (Fagus sylvatica and Quercus ilex) forming the evergreen-deciduous forest ecotone, constitutive of the rear-edge of F. sylvatica distribution. The study area is a coastal range with frequent fog immersion, which has been hypothesized to favor the persistence of F. sylvatica in Mediterranean peninsulas. We analyzed the long-term effect of fog on tree growth along a topographical gradient and the sensitivity of growth to rainfall and temperature. The annual number of foggy days has decreased by 62% over the last four decades, concomitant with increasing temperatures. Fog frequency was a relevant factor determining tree growth; fog during summer had positive effects on F. sylvatica growth mainly through a temperature buffering effect. The positive effect of fog on the growth of Q. ilex, however, was likely caused by a collinearity with rainfall. Q. ilex growth was less sensitive to climate than F. sylvatica, but growth of both species was enhanced by a positive early-summer water balance. Our results indicate that a decrease in fog frequency and an increase in temperature may generally benefit Q. ilex in this forest ecotone. Although future changes in rainfall and temperature matter most for the fate of rear-edge tree populations, local climatic singularities such as fog should also be considered. Those can have complementary effects that can swing the balance in ecotones and rear-edge tree populations such as those studied here. © 2018 Elsevier B.V.

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The effects of local climate on the correlation between weather and seed production differ in two species with contrasting masting habit

Bogdziewicz M., Szymkowiak J., Fernández-Martínez M., Peñuelas J., Espelta J.M. (2019) The effects of local climate on the correlation between weather and seed production differ in two species with contrasting masting habit. Agricultural and Forest Meteorology. 268: 109-115.
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Doi: 10.1016/j.agrformet.2019.01.016

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Many plant species present inter-annual cycles of seed production (mast seeding), with synchronized high seed production across populations in some years. Weather is believed to be centrally involved in triggering masting. The links between meteorological conditions and seeding are well-recognized for some species, but in others consistent correlates have not been found. We used a spatially extensive data set of fruit production to test the hypothesis that the influence of weather on seed production is conditioned by local climate and that this influence varies between species with different life history traits. We used two model species. European beech (Fagus sylvatica) that is a flowering masting species, i.e. seed production is determined by variable flower production, and sessile oak (Quercus petraea) that is a fruit-maturation masting species, i.e. seed production is determined by variable ripening of more constant flower production. We predicted that climate should strongly modulate the relationship between meteorological cue and fruit production in Q. petraea, while the relationship should be uniform in F. sylvatica. The influence of meteorological cue on reproduction in fruiting masting species should be strongly conditioned by local climate because the strength of environmental constraint that modulates the success of flower-to-fruit transition is likely to vary with local climatic conditions. In accordance, the meteorological cuing was consistent in F. sylvatica. In contrast, in Q. petraea the relationship between spring temperature and seed production varied among sites and was stronger in populations at colder sites. The clear difference in meteorological conditioning of seed production between the two studied species suggests the responses of masting plants to weather can be potentially systematized according to their masting habit: i.e. fruiting or flowering. © 2019 Elsevier B.V.

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Phenotypic biomarkers of climatic impacts on declining insect populations: A key role for decadal drought, thermal buffering and amplification effects and host plant dynamics

Carnicer J., Stefanescu C., Vives-Ingla M., López C., Cortizas S., Wheat C., Vila R., Llusià J., Peñuelas J. (2019) Phenotypic biomarkers of climatic impacts on declining insect populations: A key role for decadal drought, thermal buffering and amplification effects and host plant dynamics. Journal of Animal Ecology. : 0-0.
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Doi: 10.1111/1365-2656.12933

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Widespread population declines have been reported for diverse Mediterranean butterflies over the last three decades, and have been significantly associated with increased global change impacts. The specific landscape and climatic drivers of these declines remain uncertain for most declining species. Here, we analyse whether plastic phenotypic traits of a model butterfly species (Pieris napi) perform as reliable biomarkers of vulnerability to extreme temperature impacts in natural populations, showing contrasting trends in thermally exposed and thermally buffered populations. We also examine whether improved descriptions of thermal exposure of insect populations can be achieved by combining multiple information sources (i.e., integrating measurements of habitat thermal buffering, habitat thermal amplification, host plant transpiration, and experimental assessments of thermal death time (TDT), thermal avoidance behaviour (TAB) and thermally induced trait plasticity). These integrative analyses are conducted in two demographically declining and two non-declining populations of P. napi. The results show that plastic phenotypic traits (butterfly body mass and wing size) are reliable biomarkers of population vulnerability to extreme thermal conditions. Butterfly wing size is strongly reduced only in thermally exposed populations during summer drought periods. Laboratory rearing of these populations documented reduced wing size due to significant negative effects of increased temperatures affecting larval growth. We conclude that these thermal biomarkers are indicative of the population vulnerability to increasing global warming impacts, showing contrasting trends in thermally exposed and buffered populations. Thermal effects in host plant microsites significantly differ between populations, with stressful thermal conditions only effectively ameliorated in mid-elevation populations. In lowland populations, we observe a sixfold reduction in vegetation thermal buffering effects, and larval growth occurs in these populations at significantly higher temperatures. Lowland populations show reduced host plant quality (C/N ratio), reduced leaf transpiration rates and complete above-ground plant senescence during the peak of summer drought. Amplified host plant temperatures are observed in open microsites, reaching thermal thresholds that can affect larval survival. Overall, our results suggest that butterfly population vulnerability to long-term drought periods is associated with multiple co-occurring and interrelated ecological factors, including limited vegetation thermal buffering effects at lowland sites, significant drought impacts on host plant transpiration and amplified leaf surface temperature, as well as reduced leaf quality linked to the seasonal advance of plant phenology. Our results also identify multiannual summer droughts affecting larval growing periods as a key driver of the recently reported butterfly population declines in the Mediterranean biome. © 2018 The Authors. Journal of Animal Ecology © 2018 British Ecological Society

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Trajectory analysis in community ecology

De Cáceres M., Coll L., Legendre P., Allen R.B., Wiser S.K., Fortin M.-J., Condit R., Hubbell S. (2019) Trajectory analysis in community ecology. Ecological Monographs. : 0-0.
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Doi: 10.1002/ecm.1350

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Ecologists have long been interested in how communities change over time. Addressing questions about community dynamics requires ways of representing and comparing the variety of dynamics observed across space. Until now, most analytical frameworks have been based on the comparison of synchronous observations across sites and between repeated surveys. An alternative perspective considers community dynamics as trajectories in a chosen space of community resemblance and utilizes trajectories as objects to be analyzed and compared using their geometry. While methods that take this second perspective exist, for example to test for particular trajectory shapes, there is a need for formal analytical frameworks that fully develop the potential of this approach. By adapting concepts and procedures used for the analysis of spatial trajectories, we present a framework for describing and comparing community trajectories. A key element of our contribution is the means to assess the geometric resemblance between trajectories, which allows users to describe, quantify, and analyze variation in community dynamics. We illustrate the behavior of our framework using simulated data and two spatiotemporal community data sets differing in the community properties of interest (species composition vs. size distribution of individuals). We conclude by evaluating the advantages and limitations of our community trajectory analysis framework, highlighting its broad domain of application and anticipating potential extensions. © 2019 by the Ecological Society of America

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First detection of Aedes japonicus in Spain: An unexpected finding triggered by citizen science

Eritja R., Ruiz-Arrondo I., Delacour-Estrella S., Schaffner F., Álvarez-Chachero J., Bengoa M., Puig M.-A., Melero-Alcíbar R., Oltra A., Bartumeus F. (2019) First detection of Aedes japonicus in Spain: An unexpected finding triggered by citizen science. Parasites and Vectors. 12: 0-0.
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Doi: 10.1186/s13071-019-3317-y

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Background: Aedes japonicus is an invasive vector mosquito from Southeast Asia which has been spreading across central Europe since the year 2000. Unlike the Asian Tiger mosquito (Aedes albopictus) present in Spain since 2004, there has been no record of Ae. japonicus in the country until now. Results: Here, we report the first detection of Ae. japonicus in Spain, at its southernmost location in Europe. This finding was triggered by the citizen science platform Mosquito Alert. In June 2018, a citizen sent a report via the Mosquito Alert app from the municipality of Siero in the Asturias region (NW Spain) containing pictures of a female mosquito compatible with Ae. japonicus. Further information was requested from the participant, who subsequently provided several larvae and adults that could be classified as Ae. japonicus. In July, a field mission confirmed its presence at the original site and in several locations up to 9 km away, suggesting a long-time establishment. The strong media impact in Asturias derived from the discovery raised local participation in the Mosquito Alert project, resulting in further evidence from surrounding areas. Conclusions: Whilst in the laboratory Ae. japonicus is a competent vector for several mosquito-borne pathogens, to date only West Nile virus is a concern based on field evidence. Nonetheless, this virus has yet not been detected in Asturias so the vectorial risk is currently considered low. The opportunity and effectiveness of combining citizen-sourced data to traditional surveillance methods are discussed. © 2019 The Author(s).

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Seasonal diet composition of Pyrenean chamois is mainly shaped by primary production waves

Espunyes J., Bartolomé J., Garel M., Gálvez-Cerón A., Aguilar X.F., Colom-Cadena A., Calleja J.A., Gassó D., Jarque L., Lavín S., Marco I., Serrano E. (2019) Seasonal diet composition of Pyrenean chamois is mainly shaped by primary production waves. PLoS ONE. 14: 0-0.
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Doi: 10.1371/journal.pone.0210819

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In alpine habitats, the seasonally marked climatic conditions generate seasonal and spatial differences in forage availability for herbivores. Vegetation availability and quality during the growing season are known to drive life history traits of mountain ungulates. However, little effort has been made to understand the association between plant phenology and changes in the foraging strategies of these mountain dwellers. Furthermore, this link can be affected by the seasonal presence of livestock in the same meadows. The objective of this work was to study the seasonal changes in diet composition of Pyrenean chamois (Rupicapra p. pyrenaica) and its relationship to primary production trends in a Mediterranean alpine environment. Moreover, diet composition in two populations with contrasting livestock pressure was compared in order to study the effect of sheep flocks on the feeding behaviour of chamois. From 2009 to 2012, monthly diet composition was estimated by cuticle microhistological analysis of chamois faeces collected in the eastern Pyrenees. The primary production cycle was assessed by remote sensing, using the Normalized Difference Vegetation Index. Additionally, the diet of sheep sharing seasonally the subalpine and alpine meadows with chamois was analysed. Diet selection of chamois and sheep and their overlap was also assessed. Our results show an intra-annual variation in the diet composition of Pyrenean chamois and demonstrate a strong relationship between plant consumption dynamics and phenology in alpine areas. In addition, Calluna vulgaris, Cytisus spp. and Festuca spp., as well as forbs in the summer, are found to be key forage species for Pyrenean chamois. Furthermore, this study couldn’t detect differences between both chamois populations despite the presence of sheep flocks in only one area. However, the detection of a shift in the diet of chamois in both areas after the arrival of high densities of multi-specific livestock suggest a general livestock effect. In conclusion, Pyrenean chamois are well adapted to the variations in the seasonal availability of plants in alpine habitats but could be disturbed by the seasonal presence of livestock. Due to the key plants in their diet, we suggest that population management programmes should focus on the preservation of mixed grasslands composed of patches of shrubs and herbs. The effects of climate change and shrub expansion should be studied as they may potentially affect chamois population dynamics through changes in habitat composition and temporal shifts in forage availability. © 2019 Espunyes et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Sea spray influences water chemical composition of Mediterranean semi-natural springs

Fernández-Martínez M., Margalef O., Sayol F., Asensio D., Bagaria G., Corbera J., Sabater F., Domene X., Preece C. (2019) Sea spray influences water chemical composition of Mediterranean semi-natural springs. Catena. 173: 414-423.
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Doi: 10.1016/j.catena.2018.10.035

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Sea spray aerosol (SSA) is responsible for the large-scale transfer of particles from the sea to the land, leading to significant deposition of a range of ions, predominantly Na+, K+, Mg2+ Ca2+, and Cl−. Up to now, there has been little research into the effects of SSA on spring water chemistry. Therefore, we sampled 303 semi-natural springs across Catalonia (NE Iberian Peninsula) and analysed the concentrations of 20 different ions and elements, and determined the impact of SSA (using distance to the coast as a proxy) as well as climate, lithology and human disturbances. We found that distance to the coast had a clear effect on the water chemical composition of springs, while accounting for potentially confounding factors such as anthropogenic water pollution (nitrate, NO3 −), differences in lithology and annual rainfall. Our results showed that springs located closer to the coast had higher Cl−, SO4 2−, Na+, Mg2+, K+ and Ca2+ concentrations than those of springs located further away. Precipitation was generally negatively correlated with the concentration of almost all elements analysed. The concentration of NO3 − increased with distance to the coast, concurrently with farming activities, located mainly inland in the study area. These results demonstrate that SSA has an important effect on the groundwater of coastal zones, up to a distance of around 70 km from the coastline. This analysis reveals the main natural and human processes that influence spring water chemistry in this Mediterranean region, information that could be helpful in similar regions for ecological studies, water quality policies, and for the improvement of predictions in the current context of global change. © 2018 Elsevier B.V.

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