Isotopic methods for non-destructive assessment of carbon dynamics in shrublands under long-term climate change manipulation

Andresen L.C., Domínguez M.T., Reinsch S., Smith A.R., Schmidt I.K., Ambus P., Beier C., Boeckx P., Bol R., de Dato G., Emmett B.A., Estiarte M., Garnett M.H., Kröel-Dulay G., Mason S.L., Nielsen C.S., Peñuelas J., Tietema A. (2018) Isotopic methods for non-destructive assessment of carbon dynamics in shrublands under long-term climate change manipulation. Methods in Ecology and Evolution. 9: 866-880.
Link
Doi: 10.1111/2041-210X.12963

Abstract:

Long-term climate change experiments are extremely valuable for studying ecosystem responses to environmental change. Examination of the vegetation and the soil should be non-destructive to guarantee long-term research. In this paper, we review field methods using isotope techniques for assessing carbon dynamics in the plant–soil–air continuum, based on recent field experience and examples from a European climate change manipulation network. Eight European semi-natural shrubland ecosystems were exposed to warming and drought manipulations. One field site was additionally exposed to elevated atmospheric CO2. We discuss the isotope methods that were used across the network to evaluate carbon fluxes and ecosystem responses, including: (1) analysis of the naturally rare isotopes of carbon (13C and 14C) and nitrogen (15N); (2) use of in situ pulse labelling with 13CO2, soil injections of 13C- and 15N-enriched substrates, or continuous labelling by free air carbon dioxide enrichment (FACE) and (3) manipulation of isotopic composition of soil substrates (14C) in laboratory-based studies. The natural 14C signature of soil respiration gave insight into a possible long-term shift in the partitioning between the decomposition of young and old soil carbon sources. Contrastingly, the stable isotopes 13C and 15N were used for shorter-term processes, as the residence time in a certain compartment of the stable isotope label signal is limited. The use of labelled carbon-compounds to study carbon mineralisation by soil micro-organisms enabled to determine the long-term effect of climate change on microbial carbon uptake kinetics and turnover. Based on the experience with the experimental work, we provide recommendations for the application of the reviewed methods to study carbon fluxes in the plant–soil–air continuum in climate change experiments. 13C-labelling techniques exert minimal physical disturbances, however, the dilution of the applied isotopic signal can be challenging. In addition, the contamination of the field site with excess 13C or 14C can be a problem for subsequent natural abundance (14C and 13C) or label studies. The use of slight changes in carbon and nitrogen natural abundance does not present problems related to potential dilution or contamination risks, but the usefulness depends on the fractionation rate of the studied processes. © 2018 The Authors. Methods in Ecology and Evolution © 2018 British Ecological Society

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BioTIME: A database of biodiversity time series for the Anthropocene

Dornelas M., Antão L.H., Moyes F., Bates A.E., Magurran A.E., Adam D., Akhmetzhanova A.A., Appeltans W., Arcos J.M., Arnold H., Ayyappan N., Badihi G., Baird A.H., Barbosa M., Barreto T.E., Bässler C., Bellgrove A., Belmaker J., Benedetti-Cecchi L., Bett B.J., Bjorkman A.D., Błażewicz M., Blowes S.A., Bloch C.P., Bonebrake T.C., Boyd S., Bradford M., Brooks A.J., Brown J.H., Bruelheide H., Budy P., Carvalho F., Castañeda-Moya E., Chen C.A., Chamblee J.F., Chase T.J., Siegwart Collier L., Collinge S.K., Condit R., Cooper E.J., Cornelissen J.H.C., Cotano U., Kyle Crow S., Damasceno G., Davies C.H., Davis R.A., Day F.P., Degraer S., Doherty T.S., Dunn T.E., Durigan G., Duffy J.E., Edelist D., Edgar G.J., Elahi R., Elmendorf S.C., Enemar A., Ernest S.K.M., Escribano R., Estiarte M., Evans B.S., Fan T.-Y., Turini Farah F., Loureiro Fernandes L., Farneda F.Z., Fidelis A., Fitt R., Fosaa A.M., Daher Correa Franco G.A., Frank G.E., Fraser W.R., García H., Cazzolla Gatti R., Givan O., Gorgone-Barbosa E., Gould W.A., Gries C., Grossman G.D., Gutierréz J.R., Hale S., Harmon M.E., Harte J., Haskins G., Henshaw D.L., Hermanutz L., Hidalgo P., Higuchi P., Hoey A., Van Hoey G., Hofgaard A., Holeck K., Hollister R.D., Holmes R., Hoogenboom M., Hsieh C.-H., Hubbell S.P., Huettmann F., Huffard C.L., Hurlbert A.H., Macedo Ivanauskas N., Janík D., Jandt U., Jażdżewska A., Johannessen T., Johnstone J., Jones J., Jones F.A.M., Kang J., Kartawijaya T., Keeley E.C., Kelt D.A., Kinnear R., Klanderud K., Knutsen H., Koenig C.C., Kortz A.R., Král K., Kuhnz L.A., Kuo C.-Y., Kushner D.J., Laguionie-Marchais C., Lancaster L.T., Min Lee C., Lefcheck J.S., Lévesque E., Lightfoot D., Lloret F., Lloyd J.D., López-Baucells A., Louzao M., Madin J.S., Magnússon B., Malamud S., Matthews I., McFarland K.P., McGill B., McKnight D., McLarney W.O., Meador J., Meserve P.L., Metcalfe D.J., Meyer C.F.J., Michelsen A., Milchakova N., Moens T., Moland E., Moore J., Mathias Moreira C., Müller J., Murphy G., Myers-Smith I.H., Myster R.W., Naumov A., Neat F., Nelson J.A., Paul Nelson M., Newton S.F., Norden N., Oliver J.C., Olsen E.M., Onipchenko V.G., Pabis K., Pabst R.J., Paquette A., Pardede S., Paterson D.M., Pélissier R., Peñuelas J., Pérez-Matus A., Pizarro O., Pomati F., Post E., Prins H.H.T., Priscu J.C., Provoost P., Prudic K.L., Pulliainen E., Ramesh B.R., Mendivil Ramos O., Rassweiler A., Rebelo J.E., Reed D.C., Reich P.B., Remillard S.M., Richardson A.J., Richardson J.P., van Rijn I., Rocha R., Rivera-Monroy V.H., Rixen C., Robinson K.P., Ribeiro Rodrigues R., de Cerqueira Rossa-Feres D., Rudstam L., Ruhl H., Ruz C.S., Sampaio E.M., Rybicki N., Rypel A., Sal S., Salgado B., Santos F.A.M., Savassi-Coutinho A.P., Scanga S., Schmidt J., Schooley R., Setiawan F., Shao K.-T., Shaver G.R., Sherman S., Sherry T.W., Siciński J., Sievers C., da Silva A.C., Rodrigues da Silva F., Silveira F.L., Slingsby J., Smart T., Snell S.J., Soudzilovskaia N.A., Souza G.B.G., Maluf Souza F., Castro Souza V., Stallings C.D., Stanforth R., Stanley E.H., Mauro Sterza J., Stevens M., Stuart-Smith R., Rondon Suarez Y., Supp S., Yoshio Tamashiro J., Tarigan S., Thiede G.P., Thorn S., Tolvanen A., Teresa Zugliani Toniato M., Totland Ø., Twilley R.R., Vaitkus G., Valdivia N., Vallejo M.I., Valone T.J., Van Colen C., Vanaverbeke J., Venturoli F., Verheye H.M., Vianna M., Vieira R.P., Vrška T., Quang Vu C., Van Vu L., Waide R.B., Waldock C., Watts D., Webb S., Wesołowski T., White E.P., Widdicombe C.E., Wilgers D., Williams R., Williams S.B., Williamson M., Willig M.R., Willis T.J., Wipf S., Woods K.D., Woehler E.J., Zawada K., Zettler M.L. (2018) BioTIME: A database of biodiversity time series for the Anthropocene. Global Ecology and Biogeography. 27: 760-786.
Link
Doi: 10.1111/geb.12729

Abstract:

Motivation: The BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community-led open-source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal patterns of biodiversity in the Anthropocene. Main types of variables included: The database contains 8,777,413 species abundance records, from assemblages consistently sampled for a minimum of 2 years, which need not necessarily be consecutive. In addition, the database contains metadata relating to sampling methodology and contextual information about each record. Spatial location and grain: BioTIME is a global database of 547,161 unique sampling locations spanning the marine, freshwater and terrestrial realms. Grain size varies across datasets from 0.0000000158 km2 (158 cm2) to 100 km2 (1,000,000,000,000 cm2). Time period and grain: BioTIME records span from 1874 to 2016. The minimal temporal grain across all datasets in BioTIME is a year. Major taxa and level of measurement: BioTIME includes data from 44,440 species across the plant and animal kingdoms, ranging from plants, plankton and terrestrial invertebrates to small and large vertebrates. Software format:.csv and.SQL. © 2018 The Authors. Global Ecology and Biogeography Published by John Wiley & Sons Ltd

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Few multiyear precipitation-reduction experiments find a shift in the productivity-precipitation relationship

Estiarte M., Vicca S., Peñuelas J., Bahn M., Beier C., Emmett B.A., Fay P.A., Hanson P.J., Hasibeder R., Kigel J., Kröel-Dulay G., Larsen K.S., Lellei-Kovács E., Limousin J.-M., Ogaya R., Ourcival J.-M., Reinsch S., Sala O.E., Schmidt I.K., Sternberg M., Tielbörger K., Tietema A., Janssens I.A. (2016) Few multiyear precipitation-reduction experiments find a shift in the productivity-precipitation relationship. Global Change Biology. : 0-0.
Link
Doi: 10.1111/gcb.13269

Abstract:

Well-defined productivity-precipitation relationships of ecosystems are needed as benchmarks for the validation of land models used for future projections. The productivity-precipitation relationship may be studied in two ways: the spatial approach relates differences in productivity to those in precipitation among sites along a precipitation gradient (the spatial fit, with a steeper slope); the temporal approach relates interannual productivity changes to variation in precipitation within sites (the temporal fits, with flatter slopes). Precipitation-reduction experiments in natural ecosystems represent a complement to the fits, because they can reduce precipitation below the natural range and are thus well suited to study potential effects of climate drying. Here, we analyse the effects of dry treatments in eleven multiyear precipitation-manipulation experiments, focusing on changes in the temporal fit. We expected that structural changes in the dry treatments would occur in some experiments, thereby reducing the intercept of the temporal fit and displacing the productivity-precipitation relationship downward the spatial fit. The majority of experiments (72%) showed that dry treatments did not alter the temporal fit. This implies that current temporal fits are to be preferred over the spatial fit to benchmark land-model projections of productivity under future climate within the precipitation ranges covered by the experiments. Moreover, in two experiments, the intercept of the temporal fit unexpectedly increased due to mechanisms that reduced either water loss or nutrient loss. The expected decrease of the intercept was observed in only one experiment, and only when distinguishing between the late and the early phases of the experiment. This implies that we currently do not know at which precipitation-reduction level or at which experimental duration structural changes will start to alter ecosystem productivity. Our study highlights the need for experiments with multiple, including more extreme, dry treatments, to identify the precipitation boundaries within which the current temporal fits remain valid. © 2016 John Wiley & Sons Ltd.

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Physiological adjustments of a Mediterranean shrub to long-term experimental warming and drought treatments

Liu D., Llusia J., Ogaya R., Estiarte M., Llorens L., Yang X., Peñuelas J. (2016) Physiological adjustments of a Mediterranean shrub to long-term experimental warming and drought treatments. Plant Science. 252: 53-61.
Link
Doi: 10.1016/j.plantsci.2016.07.004

Abstract:

Warmer temperatures and extended drought in the Mediterranean Basin are becoming increasingly important in determining plant physiological processes and affecting the regional carbon budget. The responses of plant physiological variables such as shoot water potential (Ψ), carbon-assimilation rates (A), stomatal conductance (gs) and intrinsic water-use efficiency (iWUE) to these climatic regimes, however, are not well understood. We conducted long-term (16 years) field experiments with mild nocturnal warming (+0.6 °C) and drought (−20% soil moisture) in a Mediterranean early-successional shrubland. Warming treatment moderately influenced Ψ, A and gs throughout the sampling periods, whereas drought treatment strongly influenced these variables, especially during the summer. The combination of a natural drought in summer 2003 and the treatments significantly decreased A and iWUE. Foliar δ13C increased in the treatments relative to control, but not significantly. The values of Ψ, A and gs were correlated negatively with vapor-pressure deficit (VPD) and positively with soil moisture and tended to be more dependent on the availability of soil water. The plant, however, also improved the acclimation to drier and hotter conditions by physiological adjustments (gs and iWUE). Understanding these physiological processes in Mediterranean shrubs is crucial for assessing further climate change impacts on ecosystemic functions and services. © 2016 Elsevier Ireland Ltd

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Alteration of the phenology of leaf senescence and fall in winter deciduous species by climate change: Efects on nutrient proficiency

Estiarte M., Penuelas J. (2015) Alteration of the phenology of leaf senescence and fall in winter deciduous species by climate change: Efects on nutrient proficiency. Global Change Biology. 21: 1005-1017.
Link
Doi: 10.1111/gcb.12804

Abstract:

Leaf senescence in winter deciduous species signals the transition from the active to the dormant stage. The purpose of leaf senescence is the recovery of nutrients before the leaves fall. Photoperiod and temperature are the main cues controlling leaf senescence in winter deciduous species, with water stress imposing an additional influence. Photoperiod exerts a strict control on leaf senescence at latitudes where winters are severe and temperature gains importance in the regulation as winters become less severe. On average, climatic warming will delay and drought will advance leaf senescence, but at varying degrees depending on the species. Warming and drought thus have opposite effects on the phenology of leaf senescence, and the impact of climate change will therefore depend on the relative importance of each factor in specific regions. Warming is not expected to have a strong impact on nutrient proficiency although a slower speed of leaf senescence induced by warming could facilitate a more efficient nutrient resorption. Nutrient resorption is less efficient when the leaves senesce prematurely as a consequence of water stress. The overall effects of climate change on nutrient resorption will depend on the contrasting effects of warming and drought. Changes in nutrient resorption and proficiency will impact production in the following year, at least in early spring, because the construction of new foliage relies almost exclusively on nutrients resorbed from foliage during the preceding leaf fall. Changes in the phenology of leaf senescence will thus impact carbon uptake, but also ecosystem nutrient cycling, especially if the changes are consequence of water stress. © 2014 John Wiley & Sons Ltd.

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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.
Link
Doi: 10.1038/ncomms7682

Abstract:

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.

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Spatial variability and controls over biomass stocks, carbon fluxes, and resource-use efficiencies across forest ecosystems

Fernandez-Martinez M., Vicca S., Janssens I.A., Luyssaert S., Campioli M., Sardans J., Estiarte M., Penuelas J. (2014) Spatial variability and controls over biomass stocks, carbon fluxes, and resource-use efficiencies across forest ecosystems. Trees - Structure and Function. 28: 597-611.
Link
Doi: 10.1007/s00468-013-0975-9

Abstract:

Key message: Stand age, water availability, and the length of the warm period are the most influencing controls of forest structure, functioning, and efficiency. We aimed to discern the distribution and controls of plant biomass, carbon fluxes, and resource-use efficiencies of forest ecosystems ranging from boreal to tropical forests. We analysed a global forest database containing estimates of stand biomass and carbon fluxes (400 and 111 sites, respectively) from which we calculated resource-use efficiencies (biomass production, carbon sequestration, light, and water-use efficiencies). We used the WorldClim climatic database and remote-sensing data derived from the Moderate Resolution Imaging Spectroradiometer to analyse climatic controls of ecosystem functioning. The influences of forest type, stand age, management, and nitrogen deposition were also explored. Tropical forests exhibited the largest gross carbon fluxes (photosynthesis and ecosystem respiration), but rather low net ecosystem production, which peaks in temperate forests. Stand age, water availability, and length of the warm period were the main factors controlling forest structure (biomass) and functionality (carbon fluxes and efficiencies). The interaction between temperature and precipitation was the main climatic driver of gross primary production and ecosystem respiration. The mean resource-use efficiency varied little among biomes. The spatial variability of biomass stocks and their distribution among ecosystem compartments were strongly correlated with the variability in carbon fluxes, and both were strongly controlled by climate (water availability, temperature) and stand characteristics (age, type of leaf). Gross primary production and ecosystem respiration were strongly correlated with mean annual temperature and precipitation only when precipitation and temperature were not limiting factors. Finally, our results suggest a global convergence in mean resource-use efficiencies. © 2013 Springer-Verlag Berlin Heidelberg.

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A tethered-balloon PTRMS sampling approach for surveying of landscape-scale biogenic VOC fluxes

Greenberg J.P., Penuelas J., Guenther A., Seco R., Turnipseed A., Jiang X., Filella I., Estiarte M., Sardans J., Ogaya R., Llusia J., Rapparini F. (2014) A tethered-balloon PTRMS sampling approach for surveying of landscape-scale biogenic VOC fluxes. Atmospheric Measurement Techniques. 7: 2263-2271.
Link
Doi: 10.5194/amt-7-2263-2014

Abstract:

Landscape-scale fluxes of biogenic gases were surveyed by deploying a 100 m Teflon tube attached to a tethered balloon as a sampling inlet for a fast-response proton-transfer-reaction mass spectrometer (PTRMS). Along with meteorological instruments deployed on the tethered balloon and a 3 m tripod and outputs from a regional weather model, these observations were used to estimate landscape-scale biogenic volatile organic compound fluxes with two micrometeorological techniques: mixed layer variance and surface layer gradients. This highly mobile sampling system was deployed at four field sites near Barcelona to estimate landscape-scale biogenic volatile organic compound (BVOC) emission factors in a relatively short period (3 weeks). The two micrometeorological techniques were compared with emissions predicted with a biogenic emission model using site-specific emission factors and land-cover characteristics for all four sites. The methods agreed within the uncertainty of the techniques in most cases, even though the locations had considerable heterogeneity in species distribution and complex terrain. Considering the wide range in reported BVOC emission factors for individual vegetation species (more than an order of magnitude), this temporally short and inexpensive flux estimation technique may be useful for constraining BVOC emission factors used as model inputs. © 2014 Author(s).

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Erratum: Can current moisture responses predict soil CO2 efflux under altered precipitation regimes? A synthesis of manipulation experiments (Biogeosciences (2014) 11 (2991-3013))

Vicca S., Bahn M., Estiarte M., Van Loon E.E., Vargas R., Alberti G., Ambus P., Arain M.A., Beier C., Bentley L.P., Borken W., Buchmann N., Collins S.L., De Dato G., Dukes J.S., Escolar C., Fay P., Guidolotti G., Hanson P.J., Kahmen A., Kroel-Dulay G., Ladreiter-Knauss T., Larsen K.S., Lellei-Kovacs E., Lebrija-Trejos E., Maestre F.T., Marhan S., Marshall M., Meir P., Miao Y., Muhr J., Niklaus P.A., Ogaya R., Penuelas J., Poll C., Rustad L.E., Savage K., Schindlbacher A., Schmidt I.K., Smith A.R., Sotta E.D., Suseela V., Tietema A., Van Gestel N., Van Straaten O., Wan S., Weber U., Janssens I.A. (2014) Erratum: Can current moisture responses predict soil CO2 efflux under altered precipitation regimes? A synthesis of manipulation experiments (Biogeosciences (2014) 11 (2991-3013)). Biogeosciences. 11: 3307-3308.
Link
Doi: 10.5194/bg-11-3307-2014

Abstract:

[No abstract available]

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Can current moisture responses predict soil CO2 efflux under altered precipitation regimes? A synthesis of manipulation experiments

Vicca S., Bahn M., Estiarte M., Van Loon E.E., Vargas R., Alberti G., Ambus P., Arain M.A., Beier C., Bentley L.P., Borken W., Buchmann N., Collins S.L., De Dato G., Dukes J.S., Escolar C., Fay P., Guidolotti G., Hanson P.J., Kahmen A., Kröel-Dulay G., Ladreiter-Knauss T., Larsen K.S., Lellei-Kovacs E., Lebrija-Trejos E., Maestre F.T., Marhan S., Marshall M., Meir P., Miao Y., Muhr J., Niklaus P.A., Ogaya R., Peñuelas J., Poll C., Rustad L.E., Savage K., Schindlbacher A., Schmidt I.K., Smith A.R., Sotta E.D., Suseela V., Tietema A., Van Gestel N., Van Straaten O., Wan S., Weber U., Janssens I.A. (2014) Can current moisture responses predict soil CO2 efflux under altered precipitation regimes? A synthesis of manipulation experiments. Biogeosciences. 11: 2991-3013.
Link
Doi: 10.5194/bg-11-2991-2014

Abstract:

As a key component of the carbon cycle, soil CO2 efflux (SCE) is being increasingly studied to improve our mechanistic understanding of this important carbon flux. Predicting ecosystem responses to climate change often depends on extrapolation of current relationships between ecosystem processes and their climatic drivers to conditions not yet experienced by the ecosystem. This raises the question of to what extent these relationships remain unaltered beyond the current climatic window for which observations are available to constrain the relationships. Here, we evaluate whether current responses of SCE to fluctuations in soil temperature and soil water content can be used to predict SCE under altered rainfall patterns. Of the 58 experiments for which we gathered SCE data, 20 were discarded because either too few data were available or inconsistencies precluded their incorporation in the analyses. The 38 remaining experiments were used to test the hypothesis that a model parameterized with data from the control plots (using soil temperature and water content as predictor variables) could adequately predict SCE measured in the manipulated treatment. Only for 7 of these 38 experiments was this hypothesis rejected. Importantly, these were the experiments with the most reliable data sets, i.e., those providing high-frequency measurements of SCE. Regression tree analysis demonstrated that our hypothesis could be rejected only for experiments with measurement intervals of less than 11 days, and was not rejected for any of the 24 experiments with larger measurement intervals. This highlights the importance of high-frequency measurements when studying effects of altered precipitation on SCE, probably because infrequent measurement schemes have insufficient capacity to detect shifts in the climate dependencies of SCE. Hence, the most justified answer to the question of whether current moisture responses of SCE can be extrapolated to predict SCE under altered precipitation regimes is "no" - as based on the most reliable data sets available. We strongly recommend that future experiments focus more strongly on establishing response functions across a broader range of precipitation regimes and soil moisture conditions. Such experiments should make accurate measurements of water availability, should conduct high-frequency SCE measurements, and should consider both instantaneous responses and the potential legacy effects of climate extremes. This is important, because with the novel approach presented here, we demonstrated that, at least for some ecosystems, current moisture responses could not be extrapolated to predict SCE under altered rainfall conditions. © Author(s) 2014.

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