Automatic high-frequency measurements of full soil greenhouse gas fluxes in a tropical forest

Alice Courtois E., Stahl C., Burban B., Van Den Berge J., Berveiller D., Bréchet L., Larned Soong J., Arriga N., Peñuelas J., August Janssens I. (2019) Automatic high-frequency measurements of full soil greenhouse gas fluxes in a tropical forest. Biogeosciences. 16: 785-796.
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Doi: 10.5194/bg-16-785-2019

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Measuring in situ soil fluxes of carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) continuously at high frequency requires appropriate technology. We tested the combination of a commercial automated soil CO 2 flux chamber system (LI-8100A) with a CH 4 and N 2 O analyzer (Picarro G2308) in a tropical rainforest for 4 months. A chamber closure time of 2 min was sufficient for a reliable estimation of CO 2 and CH 4 fluxes (100% and 98.5% of fluxes were above minimum detectable flux - MDF, respectively). This closure time was generally not suitable for a reliable estimation of the low N 2 O fluxes in this ecosystem but was sufficient for detecting rare major peak events. A closure time of 25 min was more appropriate for reliable estimation of most N 2 O fluxes (85.6% of measured fluxes are above MDF±0.002 nmolm -2 s -1 ). Our study highlights the importance of adjusted closure time for each gas. © Author(s) 2019.

Llegeix més

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.

Llegeix més

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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sPlot – A new tool for global vegetation analyses

Bruelheide H., Dengler J., Jiménez-Alfaro B., Purschke O., Hennekens S.M., Chytrý M., Pillar V.D., Jansen F., Kattge J., Sandel B., Aubin I., Biurrun I., Field R., Haider S., Jandt U., Lenoir J., Peet R.K., Peyre G., Sabatini F.M., Schmidt M., Schrodt F., Winter M., Aćić S., Agrillo E., Alvarez M., Ambarlı D., Angelini P., Apostolova I., Arfin Khan M.A.S., Arnst E., Attorre F., Baraloto C., Beckmann M., Berg C., Bergeron Y., Bergmeier E., Bjorkman A.D., Bondareva V., Borchardt P., Botta-Dukát Z., Boyle B., Breen A., Brisse H., Byun C., Cabido M.R., Casella L., Cayuela L., Černý T., Chepinoga V., Csiky J., Curran M., Ćušterevska R., Dajić Stevanović Z., De Bie E., de Ruffray P., De Sanctis M., Dimopoulos P., Dressler S., Ejrnæs R., El-Sheikh M.A.E.-R.M., Enquist B., Ewald J., Fagúndez J., Finckh M., Font X., Forey E., Fotiadis G., García-Mijangos I., de Gasper A.L., Golub V., Gutierrez A.G., Hatim M.Z., He T., Higuchi P., Holubová D., Hölzel N., Homeier J., Indreica A., Işık Gürsoy D., Jansen S., Janssen J., Jedrzejek B., Jiroušek M., Jürgens N., Kącki Z., Kavgacı A., Kearsley E., Kessler M., Knollová I., Kolomiychuk V., Korolyuk A., Kozhevnikova M., Kozub Ł., Krstonošić D., Kühl H., Kühn I., Kuzemko A., Küzmič F., Landucci F., Lee M.T., Levesley A., Li C.-F., Liu H., Lopez-Gonzalez G., Lysenko T., Macanović A., Mahdavi P., Manning P., Marcenò C., Martynenko V., Mencuccini M., Minden V., Moeslund J.E., Moretti M., Müller J.V., Munzinger J., Niinemets Ü., Nobis M., Noroozi J., Nowak A., Onyshchenko V., Overbeck G.E., Ozinga W.A., Pauchard A., Pedashenko H., Peñuelas J., Pérez-Haase A., Peterka T., Petřík P., Phillips O.L., Prokhorov V., Rašomavičius V., Revermann R., Rodwell J., Ruprecht E., Rūsiņa S., Samimi C., Schaminée J.H.J., Schmiedel U., Šibík J., Šilc U., Škvorc Ž., Smyth A., Sop T., Sopotlieva D., Sparrow B., Stančić Z., Svenning J.-C., Swacha G., Tang Z., Tsiripidis I., Turtureanu P.D., Uğurlu E., Uogintas D., Valachovič M., Vanselow K.A., Vashenyak Y., Vassilev K., Vélez-Martin E., Venanzoni R., Vibrans A.C., Violle C., Virtanen R., von Wehrden H., Wagner V., Walker D.A., Wana D., Weiher E., Wesche K., Whitfeld T., Willner W., Wiser S., Wohlgemuth T., Yamalov S., Zizka G., Zverev A. (2019) sPlot – A new tool for global vegetation analyses. Journal of Vegetation Science. 30: 161-186.
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Doi: 10.1111/jvs.12710

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Aims: Vegetation-plot records provide information on the presence and cover or abundance of plants co-occurring in the same community. Vegetation-plot data are spread across research groups, environmental agencies and biodiversity research centers and, thus, are rarely accessible at continental or global scales. Here we present the sPlot database, which collates vegetation plots worldwide to allow for the exploration of global patterns in taxonomic, functional and phylogenetic diversity at the plant community level. Results: sPlot version 2.1 contains records from 1,121,244 vegetation plots, which comprise 23,586,216 records of plant species and their relative cover or abundance in plots collected worldwide between 1885 and 2015. We complemented the information for each plot by retrieving climate and soil conditions and the biogeographic context (e.g., biomes) from external sources, and by calculating community-weighted means and variances of traits using gap-filled data from the global plant trait database TRY. Moreover, we created a phylogenetic tree for 50,167 out of the 54,519 species identified in the plots. We present the first maps of global patterns of community richness and community-weighted means of key traits. Conclusions: The availability of vegetation plot data in sPlot offers new avenues for vegetation analysis at the global scale. © 2019 International Association for Vegetation Science

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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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Different effects of alpine woody plant expansion on domestic and wild ungulates

Espunyes J., Lurgi M., Büntgen U., Bartolomé J., Calleja J.A., Gálvez-Cerón A., Peñuelas J., Claramunt-López B., Serrano E. (2019) Different effects of alpine woody plant expansion on domestic and wild ungulates. Global Change Biology. 25: 1808-1819.
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Doi: 10.1111/gcb.14587

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Changes in land-use and climate affect the distribution and diversity of plant and animal species at different spatiotemporal scales. The extent to which species-specific phenotypic plasticity and biotic interactions mediate organismal adaptation to changing environments, however, remains poorly understood. Woody plant expansion is threatening the extent of alpine grasslands worldwide, and evaluating and predicting its effects on herbivores is of crucial importance. Here, we explore the impact of shrubification on the feeding efficiency of Pyrenean chamois (Rupicapra p. pyrenaica), as well as on the three most abundant coexisting domestic ungulate species: cattle, sheep and horses. We use observational diet composition from May to October and model different scenarios of vegetation availability where shrubland and woodland proliferate at the expense of grassland. We then predicted if the four ungulate species could efficiently utilize their food landscapes with their current dietary specificities measuring their niche breath in each scenario. We observed that the wild counterpart, due to a higher trophic plasticity, is less disturbed by shrubification compared to livestock, which rely primarily on herbaceous plants and will be affected 3.6 times more. Our results suggest that mixed feeders, such as chamois, could benefit from fallow landscapes, and that mountain farmers are at a growing economic risk worldwide due to changing land-use practices and climate conditions. © 2019 John Wiley & Sons Ltd

Llegeix més

Global trends in carbon sinks and their relationships with CO2 and temperature

Fernández-Martínez M., Sardans J., Chevallier F., Ciais P., Obersteiner M., Vicca S., Canadell J.G., Bastos A., Friedlingstein P., Sitch S., Piao S.L., Janssens I.A., Peñuelas J. (2019) Global trends in carbon sinks and their relationships with CO2 and temperature. Nature Climate Change. 9: 73-79.
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Doi: 10.1038/s41558-018-0367-7

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Elevated CO2 concentrations increase photosynthesis and, potentially, net ecosystem production (NEP), meaning a greater CO2 uptake. Climate, nutrients and ecosystem structure, however, influence the effect of increasing CO2. Here we analysed global NEP from MACC-II and Jena CarboScope atmospheric inversions and ten dynamic global vegetation models (TRENDY), using statistical models to attribute the trends in NEP to its potential drivers: CO2, climatic variables and land-use change. We found that an increased CO2 was consistently associated with an increased NEP (1995–2014). Conversely, increased temperatures were negatively associated with NEP. Using the two atmospheric inversions and TRENDY, the estimated global sensitivities for CO2 were 6.0 ± 0.1, 8.1 ± 0.3 and 3.1 ± 0.1 PgC per 100 ppm (~1 °C increase), and −0.5 ± 0.2, −0.9 ± 0.4 and −1.1 ± 0.1 PgC °C−1 for temperature. These results indicate a positive CO2 effect on terrestrial C sinks that is constrained by climate warming. © 2018, The Author(s), under exclusive licence to Springer Nature Limited.

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Encroachment of shrubs into subalpine grasslands in the Pyrenees modifies the structure of soil fungal communities and soil properties

Grau O., Saravesi K., Ninot J.M., Geml J., Markkola A., Ahonen S.H., Peñuelas J. (2019) Encroachment of shrubs into subalpine grasslands in the Pyrenees modifies the structure of soil fungal communities and soil properties. FEMS microbiology ecology. 95: 0-0.
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Doi: 10.1093/femsec/fiz028

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The encroachment of shrubs into grasslands is common in terrestrial ecosystems dominated by grass. Land abandonment and favourable climatic trends in recent decades have favoured the expansion of shrubs into subalpine grasslands in many mountainous regions across Europe. The advance of the succession from grassland to shrubland is expected to have a major impact on ecosystem functioning. We used DNA metabarcoding to assess whether the structure of soil fungal communities varied along the succession from subalpine grassland to shrubland in the Pyrenees, and investigated whether shrub encroachment was associated with changes in soil properties. The expansion of shrubs increased the soil C:N ratio and/or reduced the N, P or K contents. Plant-driven changes in soil properties were strongly associated with the compositional turnover of fungi, including arbuscular mycorrhizal, ectomycorrhizal, ericoid, root endophytic, saprotrophic, lichenised and pathogenic fungi. Total richness and the richness of most functional groups were correlated with soil P, N and the C:N or N:P ratios. We show that the interplay between abiotic factors (changes in soil properties) and biotic factors (occurrence and identity of shrubs) played a key role in the structure and uniqueness of soil fungal communities along the succession. © FEMS 2019.

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Effects of nitrogen loading on emission of carbon gases from estuarine tidal marshes with varying salinity

Hu M., Peñuelas J., Sardans J., Huang J., Li D., Tong C. (2019) Effects of nitrogen loading on emission of carbon gases from estuarine tidal marshes with varying salinity. Science of the Total Environment. 667: 648-657.
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Doi: 10.1016/j.scitotenv.2019.02.429

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Estuarine tidal marshes sequester significant quantities of carbon and are suffering from anthropogenic nitrogen (N) enhancement. However, the effects of this N loading on carbon gas emissions from freshwater-oligohaline tidal marshes are unknown. In this paper, we report on our evaluation of the effects of a N gradient (0, 24, 48 and 96 g NH 4 NO 3 –N m −2 y −1 ) on the methane (CH 4 ) and carbon dioxide (CO 2 ) emissions from freshwater and oligohaline tidal marshes in the Min River estuary, southeast China. On an annual scale, the oligohaline marsh has significantly higher CO 2 emissions, while it has slightly lower CH 4 emissions relative to freshwater marsh. The addition of N increased CH 4 emission from the freshwater marsh and decreased CH 4 emission from the oligohaline marsh, although there was no statistically significant difference in CH 4 emission between either of the two marshes and the control. The addition of 96 g NH 4 NO 3 –N m −2 y −1 significantly increased CO 2 emission from the freshwater marsh, while it did not significantly influence CO 2 emission from the oligohaline marsh. CH 4 and CO 2 emission levels were positively correlated with soil temperature under all conditions. The CH 4 flux resulting from both the control and the addition of N was negatively correlated with porewater SO 4 2− and Cl − concentrations and soil EC in the oligohaline marsh. Overall, N addition significantly increased carbon gas emissions under freshwater conditions while slightly inhibiting carbon gas emissions from the oligohaline marsh. Our findings suggested that even under low salinity conditions, the effects of N loading on CH 4 and CO 2 emissions from freshwater and oligohaline tidal marshes can vary. We propose that the addition of N to estuarine tidal marshes has a significant effect on the carbon cycle and promotes soil carbon loss, phenomena which may be influenced by salinity. © 2019 Elsevier B.V.

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