• Afforestation neutralizes soil pH

    Pinus koraiensis_Pixabay_Feb2018

    Afforestation is a type of land use change project primarily designated for wood production, soil and water conservation, increasing carbon storage and mitigating climate change. This study shows that afforestation changes, moreover, soil pH, that is a key soil variable. Photo by: Pixabay

    Soil pH, which measures the acidity or alkalinity of soils, is associated with many soil properties such as hydrolysis equilibrium of ions, microbial communities, and organic matter contents. Soil pH regulates soil biogeochemical processes and has cascading effects on terrestrial ecosystem structure and functions.

    Afforestation has been widely adopted to increase terrestrial carbon sequestration and enhance water and soil preservation. However, the effect of afforestation on soil pH is still poorly understood and inconclusive.

    In a new study in the journal Nature Communications scientists investigate the afforestation-caused soil pH changes with pairwise samplings from 549 afforested and 148 control plots in northern China, across different tree species and soil pH gradient.

    Authors find significant soil pH neutralization by afforestation—afforestation lowers pH in relatively alkaline soils but raises pH in relatively acid soils. The soil pH thresholds (TpH), the point when afforestation changes from increasing to decreasing soil pH, are species-specific, ranging from 5.5 (Pinus koraiensis) to 7.3 (Populus spp.) with a mean of 6.3.

    The study provides improved understandings on how afforestation impacts soil pH across a broad range of soil types and afforestation tree species, which is critical for developing climate change mitigation strategies and ecological sustainability plans.

    “Our study indicates that afforestation has the potential to alleviate soil acidification caused by enhanced acidic deposition with the appropriate selection of tree species and thus could further increase ecosystem productivity and carbon sequestration”, said Dr. Songbai Hong from Sino-French Institute for Earth System Science, Peking University.


    “Our findings indicate that afforestation can modify soil pH if tree species and initial pH are properly matched, which may potentially improve soil fertility and promote ecosystem productivity”, said Prof. Josep Peñuelas from CREAF-CSIC Barcelona.

    According to the authors, further field studies are still needed to determine best tree species for afforestation according to soil properties, water availability and climate suitability, and designated ecosystem and socioeconomic goals.

    Journal Reference: Hong, S., Piao, s., Chen, A., Liu, Y., Liu, L., Peng, S., Sardans, J., Sun, Y., Peñuelas, J., Zeng, H. 2017. Afforestation neutralizes soil pH. Nature Communications, (2018) 9:520. doi: 10.1038/s41467-018-02970-1.

    The large mean body size of mammalian herbivores explains the productivity paradox during the last glacial maximum

    Mammalian herbivores live in major terrestrial ecosystems on Earth. During the past decades, our understanding has increased about the important role of large mammalian herbivores (body mass >10 kg) in controlling vegetation structure and carbon and nutrient flows within ecosystems. Photo by: Pixabay


    Large herbivores are a major agent in ecosystems, influencing vegetation structure and carbon and nutrient flows (shattering woody vegetation and consuming large amounts of foliage). Despite the non-negligible ecological impacts of large herbivores, most of the current DGVMs, or land surface models that include a dynamic vegetation module, lack explicit representation of large herbivores and their interactions with vegetation.

    During the last glacial period, the steppe-tundra ecosystem prevailed on the unglaciated northern lands, hosting a high diversity and density of megafaunal herbivores. The apparent discrepancy between the late Pleistocene dry and cold climates and the abundant herbivorous fossil fauna found in the mammoth steppe biome has provoked long-standing debates, termed as “productivity paradox” by some paleontologists.

    In a new study in the journal Nature Ecology and -Evolution scientists, aiming to address the productivity paradox, incorporated a grazing module in the ORCHIDEE-MICT DGVM model. “This grazing module is based on physiological and demographic equations for wild large grazers, describing grass forage intake and metabolic rates dependent on body size, and demographic parameters describing the reproduction and mortality rates of large grazers”, explained Dr. Dan Zhu from the Laboratoire des Sciences du Climat et de l’Environnement, LSCE CEA CNRS UVSQ, France.

    In the study authors also extended the modelling domain to the globe for two distinct periods, present-day and the last glacial maximum (ca. 21 ka BP). The present-day results of potential grazer biomass, combined with an empirical land use map, infer a reduction of wild grazer biomass by 79-93% due to anthropogenic land replacement over natural grasslands.

    For the last glacial maximum, authors find that the larger mean body size of mammalian herbivores than today is the crucial clue to explain the productivity paradox, due to a more efficient exploitation of grass production by grazers with a larger-body size. Evidences from fossil and extant mammal species have shown a long-term trend towards increasing body size in mammals throughout the Cenozoic, this indicates selective advantages of larger body sizes, such as larger guts of herbivores that allow microbes to break down low-quality plant materials, and higher tolerance to coldness and starvation. “Our results show quantitatively the importance of body size to explain the productivity paradox, as a larger-body size enables grazers to live on the mammoth steppe in substantial densities during the LGM, despite colder temperatures and shorter growing seasons than today”, said Dr. Philippe Ciais from the Laboratoire des Sciences du Climat et de l’Environnement, LSCE CEA CNRS UVSQ, France.

    For the authors large herbivores might have fundamentally modified Pleistocene ecosystems; therefore, “to bring them into large-scale land surface models would help us better understand the intricate interactions among climate, plants and animals that shaped the biosphere”, said Prof. Josep Peñuelas from CREAF-CSIC Barcelona.

    Journal Reference: Zhu, D., CIiais, P., Chang, J., Krinner, G., Peng, S., Viovy, N., Peñuelas, J., Zimov, S. 2018. The large mean body size of mammalian herbivores explains the productivity paradox during the last glacial maximum. Nature Ecology & Evolution

    How to spend a dwindling greenhouse gas budget

    The Paris Agreement is based on emission scenarios that move from a sluggish phase-out of fossil fuels to largescale late-century negative emissions. In a new study in the journal Nature Climate Change authors argue that a new set of scenarios needs to be generated and analysed to inform the policy process on robust timing of climate mitigation, with the aim of avoiding negative side effects. Image by: Pixabay.

    The 2015 climate summit in Paris galvanized global commitments to an ambitious yet vaguely defined goal of climate stabilization. The Paris Agreement is based on emission scenarios that move from a sluggish phase-out of fossil fuels to largescale late-century negative emissions. At the same time, some scientists argue that the model based scenarios with 1.5 °C and even 2 °C temperature change targets seem unattainable and detached from current political realities. Alternative pathways of early deployment of negative emission technologies need to be considered to ensure that climate targets are reached safely and sustainably

    In a new study in the journal Nature Climate Change, authors scrutinize the dominant climate mitigation scenario archetype that projects low global decarbonization rates in the first half of this century followed by large negative emissions in the second half, thanks to carbon dioxide removal (CDR) technologies. Authors call this approach to mitigation the ‘Late- Century CDR’ scenario archetype.

    This archetype is consistent with nearly all of 2 °C scenarios covered by the IPCC’s Fifth Assessment Report (AR5), 87% of which deploy CDR technologies in the second half of the century. The authors consider that, following this predominant archetype might not only turn out to be a risky strategy, but may lead to significant environmental damages and may also be economically inefficient. In Late-Century CDR scenarios, CDR mostly in the form of bioenergy with carbon capture and storage (BECCS) typically removes the equivalent of 20 years of current GHG emissions to reverse the temporary GHG budget overshoot that is tolerated earlier on. The authors point out that the challenges and uncertainties associated with CDR are well described in the scientific literature, yet the scientific and political debate addressing the consequences of large-scale and late deployment of CDR as a backstop strategy is only at an early stage.

    Authors argue that a new set of scenarios needs to be generated and analysed to inform the policy process on robust timing of climate mitigation, with the aim of avoiding negative side effects. “Essentially, three attributes characterize such budget-constrained scenarios: the timing and magnitude of global peak net emissions and the speed of decline thereafter; the maximum amount of allowable deployment of biomass-based CDRs; and an admissible risk threshold associated with a temperature overshoot”, noted Prof. Obersteiner from the Ecosystems Services and Management Program, International Institute for Applied Systems Analysis (IIASA) Laxenburg, Austria.

    The study concludes that the timing of mitigation actions, in particular of negative emission technologies, needs to be urgently revisited in the analyses of ambitious climate targets. They argue that considerations of both intergenerational equity and climate/environment safety motivate early and moderate — rather than extreme — deployment of negative emission technologies as well as a timely peak in net carbon emissions as early as 2020. As a consequence all of the near-term and mid-century net emission reduction, targets should be, according to the authors, reformulated to include targets of early action on CDR technology portfolios.

    “Transforming the 570 million farms to be climate smart and incentivizing 1.6 billion people who economically depend on forests to become early movers in No Overshoot and Minimize CDR scenarios is a formidable global policy challenge. We call for a discourse on effective strategies, starting with more detailed global gap assessments of the archetypes, and then mainstreaming the gained insights into Nationally Determined Contributions and implementation plans”, said Prof. Josep Peñuelas from CREAF-CSIC Barcelona.

    Journal Reference: Obersteiner, M., Bednar, J., Wagner, F., Gasser, T., Ciais, P., Forsell, N., Frank, S., Havlik, P., Valin, H., Janssens, I.A., Peñuelas, J., Schmidt-Traub, G. 2018. How to spend a dwindling greenhouse gas budget. Nature Climate Change 8, 7-10. doi: 10.1038/s41558-017-0045-1

    Mapping local and global variability in plant trait distributions

    Butler_et al_PNAS_2017.tif
    Specific leaf area (SLA), and dry mass-based concentrations of leaf nitrogen (Nm) and phosphorus (Pm) are used in this study to better capture the response of the land surface component of the Earth System to environmental change. Image: Butler, E.E., et al. 2017. Proceedings of the National Academy of Sciences

    Our ability to understand and predict the response of ecosystems to a changing environment depends on quantifying vegetation functional diversity. However, representing this diversity at the global scale is challenging. Typically, in Earth Systems Models, characterization of plant diversity has been limited to grouping related species into Plant Functional Types (PFTs), with all trait variation in a PFT collapsed into a single mean value that is applied globally.

    In a new study in the journal Proceedings of the National Academy of Sciences authors created fine-grained global maps of plant trait distributions that can be applied to Earth System Models by using the largest global plant trait database and state of the art Bayesian modeling. “Here, we use an updated version of the largest global database of plant traits coupled with modern Bayesian spatial statistical modeling techniques to capture local and global variability in plant traits. This combination allows the representation of trait variation both within pixels on a gridded land surface as well as across global environmental gradients”, said Dr. Butler from Department of Forest Resources, University of Minnesota.

    Focusing on a set of plant traits closely coupled to photosynthesis and foliar respiration – specific leaf area (SLA), and dry mass-based concentrations of leaf nitrogen (Nm) and phosphorus (Pm), authors characterize how traits vary within and among over 50,000 ~ 50 × 50 km cells across the entire vegetated land surface. “The importance of these traits (SLA, Nm, Pm) and the more advanced representation of functional diversity developed here may be used to better capture the response of the land surface component of the Earth System to environmental change”, said Prof. Josep Peñuelas from CREAF-CSIC Barcelona.

    This endeavor advances prior trait mapping by generating global maps that preserve variability across scales by using modern Bayesian spatial statistical modeling in combination with a database over three times larger than previous analyses. “Our maps reveal that the most diverse grid cells possess trait variability close to the range of global PFT means”, said Dr. Butler from Department of Forest Resources, University of Minnesota.

    Journal Reference: Butler, E.E., Datta, A., Flores-Moreno, H., Chen, M., Wythers, K.R., Fazayeli, F., Banerjee, A., Atkin, O.K., Kattge, J., Amiaud, B., Blonder, B., Boenisch, G., Bond-Lamberty, B., Brown, K.A., Byun, C., Campetella, G., Cerabolini, B.E.L., Cornelissen, J.H.C., Craine, J.M., Craven, D., de Vries, F.T., Díaz, S., Domingues, T., Forey, E., Gonzalez, A., Gross, N., Han, W., Hattingh, W.N.,  Hickler, T., Jansen, S., Kramer, K., Kraft, N.J.B., Kurokawa, H., Laughlin, D.C., Meir, P., Minden, V.,  Niinemets, Ü., Onoda, Y., Peñuelas, J., Read, Q., Valladares Ros, F., Sack, L., Schamp, B.,  Soudzilovskaia, N.A., Spasojevic, M.J., Sosinski, E., Thornton, P., van Bodegom, P.M.,  Williams, M., Wirth, C., Reich, P.B.. 2017. Mapping local and global variability in plant trait distributions. Proceedings of the National Academy of Sciences.

    Shifting from a fertilization-dominated to a warming-dominated period

    Penuelas_Nature_Shifting_Sept2017In a new study in the journal Nature Ecology and Evolution researchers argue that a slowdown of the CO2 and N fertilization effects on ecosystem carbon sequestration and the rapid emergence of negative ecosystem impacts from global climate change might drive a change from a fertilization-dominated to a warming-dominated period. Photos by Pixabay

    Natural ecosystems currently remove on average each year an amount of carbon dioxide equivalent to about one third of human-caused carbon dioxide (CO2) emissions from fossil fuel burning and cement production. There are numerous evidences which show that the efficiency of natural land ecosystems to absorb the increasing fossil fuel and cement emissions does not keep their path.

    In a new study in the journal Nature Ecology and Evolution authors hypothesize that the progressive long term weakening of the natural land sink relative to fossil fuel CO2 emissions marks the beginning of a transition from a vegetation fertilization-dominated period to a period dominated by nutrient and climate constraints on plant growth, and larger climate change impacts (e.g., heatwaves).

    There are many unknowns in the timing of this transition, so in light of the recent Paris COP21 agreement, a better understanding of climate change impacts on carbon stocks remains paramount to understand the level of climate mitigation required to achieve agreed temperature goals, indicates Prof Josep Peñuelas from CREAF-CSIC Barcelona.

    Human fertilization changes productivity and carbon residence in ecosystems

    Human activities result in increasing atmospheric concentrations of CO2, N inputs to ecosystems and temperature. This leads to enhanced metabolism of organism and lengthening the growing seasons. Plants can consequently grow more. The magnitude of carbon sinks and their duration depend both on the rate of increase of carbon inputs and on the residence time of the carbon being taken up by ecosystems explain Drs Shilong Piao from Academy of Sciences in Pekin and Jordi Sardans from CREAF in Barcelona.

    Authors point out that several studies realized at global scale, in all biomes, suggest that trends of increasing sinks may be slowing down. A remaining question is whether in regions where carbon sinks may be slowing down, this is due to stalling productivity or to reducing residence times.

    Likely limitations for enhancement of carbon sinks

    The anthropogenic increases in CO2 and atmospheric nitrogen deposition are not matched by a similar increase in the inputs of other key nutrients such as phosphorus (P) and/or potassium (K). Current evidence suggests an overall shortage of P which will act as a limiting factor to meet the increasing demand for plant growth. “A better understanding of the factors that regulate exchanges between pools of “available” and “unavailable” soil P is critically needed”, said Prof. Ivan Janssens from University of Antwerp.

    The higher nocturnal temperatures enhance night respiration, Prof. Josep Canadell pointed out. Moreover, severe regional heatwaves are also likely to become more frequent in a changing climate, and their negative impact on terrestrial carbon sequestration may thus also become important. “For example, the 2003 heatwave decreased European gross primary productivity by 30%, which resulted in a strong anomalous net source of carbon dioxide to the atmosphere; this effect is the equivalent of reversing four years of net ecosystem carbon sequestration in the European continent”, said Prof. Philippe Ciais from LSCE Paris.

    In recent decades large-scale droughts have reduced seasonal NPP in the Southern and Northern hemispheres and weakened the terrestrial carbon sink. However, as Drs Marcos Fernandez-Martinez and Jofre Carnicer from CREAF-CSIC Barcelona point out, there is an inherent difficulty in quantifying the response of NPP to drought because it depends on the timing of drought during the growing season, and on ecosystem properties of resistance to drought.

    Furthermore, it should be taken into account that most land use changes, fires, and harvests, which are expected to increase in the future reduce residence times, thereby reducing the sink capacity of the land biosphere as noticed by Prof Michael Obersteiner from IIASA Vienna.

    Due to the above, the potential saturation or slower increase of the sink capacity of terrestrial ecosystems, or even its transition into a source of CO2, could be expected. Moreover, for Prof. Josep Peñuelas from CREAF-CSIC Barcelona, current climate models do not necessarily well represent extreme events due to coarse resolution (eg. extreme precipitation, wind storms and tropical cyclones) or to insufficiently constrained soil-atmosphere interactions. At this point, authors point out that these models could improve its prediction capacity through the addition of factors outlined above. “Such improved models could then help understanding the responses to different levels of global warming (especially in the range 1.5-3°C according to the Paris agreement and current intended policies)”, said Prof. Josep Peñuelas from CREAF-CSIC Barcelona.

    Shift from a fertilization to a warming period

    This study presents multiple evidences suggesting limits to the buffering capacity of the biosphere. Thus, Prof. Josep Peñuelas indicates that a slowdown of the CO2 and N fertilization effects on ecosystem carbon sequestration and the rapid emergence of negative ecosystem impacts from global climate change might drive a shift from an Anthropocene period dominated by fertilization to another period characterized by saturated fertilization and strong climate change.

    For Prof. Peñuelas, although the climate has not yet changed dramatically in the Anthropocene, the coming decades will undoubtedly be different. Prof. Vautard from LSCE Paris explains that “A warming of 2 °C would slightly increase the frequency of 2003-like heatwaves in Northern France, but a warming of 3 °C would instead produce very different conditions, with one summer like that of 2003 occurring every three or four years, which would therefore affect the forests carbon sink in Europe much more than in the past”.

    There is also the possibility of low probability but high impact phenomena which would lead to rapid positive feedbacks to the climate system (e.g. massive dieback of Amazon rainforest because of reduced rainfall or a dramatic temperature drop in the North Atlantic because of the collapse of the ocean current). “The occurrence of this phenomena is highly uncertain, particularly for low temperature scenarios. However, it is much more certain that we are currently entering a new warming period where ecosystems are put under increasing stresses”, said Prof. Josep Peñuelas from CREAF-CSIC Barcelona.

    This study was funded by the European Research Council Synergy grant ERC-2013-SyG-610028

    Journal Reference: Peñuelas, P., Ciais, P., Canadell, J., Janssens, I., Fernandez-Martinez, M., Carnicer, J., Obersteiner, M., Piao, S., Vautard, R., Sardans, J. 2017. Shifting from a fertilization-dominated to a warming-dominated period. Nature Ecology and Evolution.


    Microbial mass movements

    Flying aircrafts_ESA_Sept2017
    Global transport, tourism, waste disposal have changed biogeographic patterns for microorganisms. In this study authors point to the importance of the dispersal of cells and genes by human activities. The picture presents a flight map showing 15,000 simultaneously flying aircrafts based on 25 million positions (European Space Agency (ESA)).

    For several billion years, microorganisms and the genes they carry have mainly been moved by physical forces such as air and water currents. These forces generated biogeographic patterns for microorganisms that are similar to those of animals and plants.

    In a new study in the journal Science authors note that humans and animals now move on an unprecedented scale, and this movement actively transports and enriches a specific subset of microorganisms.

    “Humans in the past 100 years have changed these natural dynamics by transporting large numbers of cells to new locations through waste disposal, tourism, and global transport and by modifying selection pressures at those locations. As a consequence, we are substantially altering microbial biogeography”, said Prof. Josep Peñuelas from CREAF-CSIC Barcelona.

    Dissemination through wastewater

    Wastewater carries high densities of microorganisms and their cargo genes. It should be noted that, globally, some 359,000 km2 of croplands depend on irrigation with urban wastewater, 80% of which undergoes little or no treatment. Therefore, the use of wastewater or manure in agriculture contaminates fruits, vegetables, and farm animals which in turn are distributed globally. Wastewater also contains pollutants with biological effects (as metals, antibiotics or disinfectants). These compounds stimulate bacterial stress response systems that increase mutation rates which, in turn, confer adaptive advantages on at least a subset of cells arriving at a new location.

    For a sense of the importance of this adaptive advantage, authors consider the clinical class 1 integron. This DNA element acquires foreign genes from the environment and has played a central role in spreading antibiotic resistance among bacterial pathogens. DNA sequencing data show that it had the origin in a single cell, in the early 20th century. Millions to billions of copies of this element now exists in every gram of feces from human and domestic animals. This remarkable increase in its abundance and distribution has been driven by antibiotic selection, increases in human population, and dissemination via global transport.

    The role of human and material movement

    This study points out that humans and agricultural animals now comprise 35 times as much biomass as wild terrestrial mammals. The bacteria shed in feces, therefore, mainly represent the gut microbiota of humans and agricultural animals (cattle, sheep, goats, pigs, and chickens) and they have vastly increased in both abundance and distribution, particularly in the last century. “Efficiency of dispersal is enhanced by the 1.2 billion international tourist movements per year, as evidenced by the rapid spread of bacterial clones and antibiotic resistance genes between continents”, emphasizes Prof. Micahel Gillings from Macquarie University, Sydney .

    The study also points out that humans additionally promote dispersal of microbial cells via mass movement of materials. In this regard it should be noted that human activities now move more soil, sand, and rock than all natural processes combined. As an example, natural fluvial erosion is 21 gigatons (Gt) per year, much lower than the75 Gt per year eroded by agriculture. “This erosion transports very large numbers of bacteria, given that soil can contain more than a billion microbial cells per gram. Movements on this scale have consequences for human health, agriculture, and ecosystem functions, such as increasing the spread of human pathogens and threatening sustainable food productivity”, said Prof. Yong-Guan Zhu from Chinese Academy of Science.

    Changes to biogeochemical cycles

    According to this study, changes in the distribution and abundance of microorganisms, and the resultant changes in microbial ecosystems will affect biogeochemical cycles driven by microbial activity. “Knowledge of the connections between microbial biodiversity and landscape-scale biogeochemical processes, as well as below-ground ecosystems, will be essential to predict the magnitude and direction of these changes”, said Prof. Josep Peñuelas from CREAF-CSIC Barcelona.

    Linking the rapidly expanding databases generated by environmental genomics with biogeochemical models could reveal changes in nutrient cycles. “This fusion of genomics and Earth system science is a first step to understanding how the biochemical functions of microorganisms could be altered, temporally and spatially, by global change”, said Prof. Yong-Guan Zhu from Chinese Academy of Science.

    Unlocking the complexity

    There is a recent growing trend for monitoring the environmental dissemination of genes, particularly those that confer phenotypes of direct relevance to human and animal health. In this sense, Prof. Josep Peñuelas points to the high importance of understanding how human activities cause systematic changes in ecosystems and highlight the priority of investigating microbial invasions, microbial extinctions, and perturbations to microbial ecosystems.

    Journal Reference: Zhu, Y.G., Gillings, M., Simonet, P., Stekel, D., Banwart, S., Penuelas, J. 2017. Microbial mass movements. Science 357 (6356), 1099-1100.

    Atmospheric deposition, CO2, and change in the land carbon sink

    The reduction in acidic deposition of nitrogen and Sulphur should lead to a slow recovery of forests to a pre-acid deposition state. Photo by Pixabay

    Human activities result in increasing atmospheric concentrations of CO2 that affects the terrestrial biosphere in multiple ways: warming the climate, increasing photosynthesis (CO2 fertilization), decreasing transpiration by stimulating stomatal closure and changing the stoichiometry of carbon, nitrogen and phosphorus (C:N:P) in ecosystem carbon pools. Concentrations of atmospheric carbon dioxide (CO2) have continued to increase whereas, due to air-quality policies, atmospheric deposition of sulphur and nitrogen has declined in Europe and the USA during recent decades.

    Terrestrial ecosystems are key components of the global carbon cycle, as indicated by the fact that, since the 1960s, they have been sequestering an average of about 30% of the annual anthropogenic CO2 emitted into the atmosphere.

    In a new study in the journal Scientific Reports authors used time series of flux observations from 23 forests distributed throughout Europe and the USA, and generalised mixed models to end up finding  that forest-level net ecosystem production and gross primary production have increased by 1% annually from 1995 to 2011.

    In this study, authors test the hypothesis that gross primary production, ecosystem respiration and the net C-sink strength (net land-atmosphere CO2 flux) or net ecosystem production (NEP), have accelerated during the last two decades because of the increased atmospheric CO2 concentrations and temperature, and because of the recovery from high loads of S deposition in Europe and North America. “We expected these deposition reductions to have modulated the biogeochemical effects of rising CO2” added Dr. Marcos Fernández-Martínez from CREAF-CSIC Barcelona

    Statistical models indicated that increasing atmospheric CO2 was the most important factor driving the increasing strength of carbon sinks in these forests. Authors also found that the reduction of sulphur deposition in Europe and the USA led to higher recovery in ecosystem respiration than in gross primary production, thus limiting the increase of carbon sequestration. By contrast, the study shows that trends in climate and nitrogen deposition did not significantly contribute to changing carbon fluxes during the studied period. “Our findings support the hypothesis of a general CO2-fertilization effect on vegetation growth and suggest that, so far unknown, sulphur deposition plays a significant role in the carbon balance of forests in industrialized regions”, said Prof. Josep Peñuelas from CREAF-CSIC Barcelona

    “Our results show the need to include the effects of changing atmospheric composition, beyond CO2, to assess future dynamics of carbon-climate feedbacks not currently considered in earth system/climate modelling”, said Dr. Fernández-Martínez from CREAF-CSIC Barcelona

    This study was funded by the European Research Council Synergy grant ERC-2013-SyG-610028, the Spanish Government project CGL2016-79835-P and the Catalan Government grant FI-2013

    Journal Reference: Fernández-Martínez, M., Vicca, S., Janssens, I.A., Ciais, P., Obersteiner, M., Bartrons, M., Sardans, J., Verger, A., Canadell, J.G., Chevallier, F., Wang, X., Bernhofer, C., Curtis, P.S., Gianelle, D., Grünwald, T., Heinesch, B., Ibrom, A., Knohl, A., Laurila, T., Law, B.E., Limousin, J.M., Longdoz, B., Loustau, D., Mammarella, I., Matteucci, G., Monson, R.K., Montagnani, L., Moors, E.J., Munger, J.W., Papale, D., Piao, S.L., Peñuelas, J. 2017. Atmospheric deposition, CO2, and change in the land carbon sink. Scientific Reports 7, 9632.

    Relative contribution of groundwater to plant transpiration estimated with stable isotopes

    Water is generally taken up by roots (with important exceptions), so root structure and function should play a central role in research of plant-water relations. Photo by Pixabay

    Water stored underground in the saturated and subsurface zones below the soil are important sources of water for plants in water-limited ecosystems. Arid and seasonally dry ecosystems contain the deepest root systems, and some species grow roots to depths of more than 4 m, even in temperate and tropical ecosystems. The presence of deep-rooted plants worldwide, however, suggests that the use of groundwater is not restricted to arid and seasonally dry ecosystems.

    In a new study in the journal Scientific Reports authors compiled the available data (71 species) on the relative contribution of groundwater to plant water estimated using stable isotopes and mixing models, which provided information about relative groundwater use, and analysed their variation across different climates, seasons, plant types, edaphic conditions, and landscape positions.

    Plant use of groundwater was more likely at sites with a pronounced dry season, and represented on average 49 per cent of transpired water in dry seasons and 28 per cent in wet seasons. The relative contribution of groundwater to plant-water uptake was higher on rocky substrates (saprolite, fractured bedrock), which had reduced groundwater uptake when this source was deep belowground.

    Notably, authors found that the connectivity between groundwater pools and plant water is quantitatively larger and more widespread than reported by recent global estimations based on isotopic averaged values. Thus, “in order to improve the representation of groundwater-surface interactions in models, a quantification of the relative contribution of groundwater to transpiration and its variability across environmental gradients was required”, said Dr. Adrià Barbeta from CREAF-CSIC Barcelona, now in INRA Bourdeaux

    Prof. Josep Peñuelas from CREAF-CSIC Barcelona claims also that “further research on plant-water sources in boreal, polar regions and tropical rainforests would help our understanding of the global patterns of groundwater uptake and may substantially improve the biosphere-atmosphere models by a realistic representation of this important component of the water cycle”.

    This study was funded by the European Research Council Synergy grant ERC-2013-SyG-610028, the Spanish Government project CGL2016-79835-P and the Catalan Government grant FI-2013

    Journal Reference: Barbeta, A., Peñuelas, J. 2017. Relative contribution of groundwater to plant transpiration estimated with stable isotopes. Scientific Reports

    β-Ocimene, a Key Floral and Foliar Volatile Involved in Multiple Interactions between Plants and Other Organisms

    Plants generally synthesize and emit species-specific floral volatile organic compounds (VOCs) mixtures to attract pollinators by mixing several of these common VOCs. Photo by Pexels

    More than 1700 volatile organic compounds (VOCs) have been identified in the floral scents of flowering plants. These VOCs are not equally distributed across the phylogeny of flowering plants, so that the commonness and predominance of these compounds in floral scents varies widely among species. Common floral VOCs have a widespread phylogenetic distribution, which means that they are present in the floral scents of many species from different plant families. Instead, less common floral VOCs are only present in plants that are pollinated by specific pollinator groups with specific innate preferences for those VOCs.

    β-Ocimene is a very common plant volatile released in important amounts from the leaves and flowers of many plant species. This acyclic monoterpene can play several biological functions in plants, by potentially affecting floral visitors and also by mediating defensive responses to herbivory.

    In a new study in the journal Molecules authors indicated that the ubiquity and high relative abundance of β-ocimene in the floral scents of species from most plant families and from different pollination syndromes (ranging from generalism to specialism) strongly suggest that this terpenoid may play an important role in the attraction of pollinators to flowers.

    In this study authors compiled abundant evidence from published studies that supports β-ocimene as a generalist attractant of a wide spectrum of pollinators. They found no studies testing behavioural responses of pollinators to β-ocimene, that could directly demonstrate or deny the function of β-ocimene in pollinator attraction; but “several case studies support that the emissions of β-ocimene in flowers of different species follow marked temporal and spatial patterns of emission, which are typical from floral volatile organic compound (VOC) emissions that are involved in pollinator attraction”, said Dr. Gerard Farré-Armengol from CREAF-CSIC Barcelona, now in the University of Salzburg.

    Furthermore, important β-ocimene emissions are induced from vegetative plant tissues after herbivory in many species, which have relevant functions in the establishment of tritrophic interactions. Authors thus conclude that β-ocimene is a key plant volatile with multiple relevant functions in plants, depending on the organ and the time of emission.

    Experimental behavioural studies on pure β-ocimene conducted with pollinating insects will be necessary to prove the assumptions made here. “In view of the presented indirect evidences, we strongly encourage the inclusion of β-ocimene alone or in combination with other floral volatiles in coupled gas chromatography electroantennographic detection (GC-EAD) analyses and behavioural tests when conducting future studies in order to provide a solid experimental proof for the assumptions made in the study”, said Prof. Josep Peñuelas from CREAF-CSIC Barcelona.

    This study was funded by the European Research Council Synergy grant ERC-2013-SyG-610028, the Spanish Government project CGL2016-79835-P and the Catalan Government grant FI-2013

    Journal Reference: Farré-Armengol, G., Filella, I., Llusià, J., Peñuelas, J. 2017. β-Ocimene, a Key Floral and Foliar Volatile Involved in Multiple Interactions between Plants and Other Organisms. Molecules 2017, 22, 1148; doi: 10.3390/molecules22071148.

    Temperature increase reduces global yields of major crops in four independent estimates

    kornfeld / cornfield
    Understanding climate change is critical to ensure global food security. In this study authors combine four analytical methods to assess the impact of increasing temperatures on yields of wheat, rice, maize and soybean. Photo by Pexels

    All agricultural production is vulnerable to climate change including wheat, rice, maize and soybean that provide two-thirds of human caloric intake. Assessing the impact of global temperature increase on production of these major crops is therefore critical to maintain global food supply.

    In a new study in the journal Proceedings of the National Academy of Sciences authors investigated the impacts of temperature on yields of the four crops by compiling extensive published results from four analytical methods: global grid-based and local point-based models, statistical regressions and field-warming experiments.

    “By combining four different methods, our comprehensive assessment of the impacts of increasing temperatures on major global crops shows substantial risks for agricultural production, already stagnating in some parts of the world”, said Prof. Josep Peñuelas from CREAF-CSIC Barcelona.

    The study shows that results from the different methods consistently indicate negative temperature impacts on crop yield at the global scale, generally underpinned by similar impacts at country and site scales. Without CO2 fertilization, effective adaptation and genetic improvement, each degree Celsius increase in global mean temperature would on average reduce global yields of wheat by 6.0%, rice by 3.2%, maize by 7.4% and soybean by 3.1%. In any case, researchers point out that results are highly heterogeneous across crops and geographical areas with some positive impact estimates.

    Multi-method analyses improved the confidence in assessments of future climate impacts on global major crops, and suggest crop- and region-specific adaptation strategies to ensure food security for an increasing world population.

    Journal Reference: Zhao, C., Liu, B., Piao, S., Wang, X., Lobell, D., Huang, Y., Huang, M., Yao, Y., Bassu, S., Ciais, P., Durand, J-L., Elliott, L., Ewert, F., Janssens, I., Li, T., Lin, E., Liu, Q., Martre, P., Müller, C., Peng, S., Peñuelas, J., Ruane, A., Wallach, D., Wang, T., Wu, D., Liu, Z., Zhu, Y., Zhu, Z., Asseng, S. 2017. Temperature increase reduces global yields of major crops in four independent estimates. Proceedings of the National Academy of Sciences.

    Next 10 years critical for achieving climate change goals

    Carbon dioxide (CO2) and other greenhouse gases in the atmosphere can be reduce in two ways — by cutting our emissions, or by removing it from the atmosphere, for example through plants, the ocean, and soil.

    In a new study, published in the journal Nature Communications, researchers from the International Institute for Applied Systems Analysis (IIASA) used a global model of the carbon system that accounts for carbon release and uptake through both natural and anthropogenic activities.

    “The study shows that the combined energy and land-use system should deliver zero net anthropogenic emissions well before 2040 in order to assure the attainability of a 1.5°C target by 2100,” says IIASA Ecosystems Services and Management Program Director Michael Obersteiner, a study coauthor.

    According to the study, fossil fuel consumption would likely need to be reduced to less than 25% of the global energy supply by 2100, compared to 95% today. At the same time, land use change, such as deforestation, must be decreased. This would lead to a 42% decrease in cumulative emissions by the end of the century compared to a business as usual scenario.

    “This study gives a broad accounting of the carbon dioxide in our atmosphere, where it comes from and where it goes. We take into account not just emissions from fossil fuels, but also agriculture, land use, food production, bioenergy, and carbon uptake by natural ecosystems,” explains World Bank consultant Brian Walsh, who led the study while working as an IIASA researcher.

    The compares four different scenarios for future energy development, with a range of mixtures of renewable and fossil energy. In a “high-renewable” scenario where wind, solar, and bioenergy increase by around 5% a year, net emissions could peak by 2022, the study shows. Yet without substantial negative emissions technologies, that pathway would still lead to a global average temperature rise of 2.5°C, missing the Paris Agreement target.

    Walsh notes that the high-renewable energy scenario is ambitious, but not impossible — global production of renewable energy grew 2.6% between 2013 and 2014, according to the IEA. In contrast, the study finds that continued reliance on fossil fuels (with growth rates of renewables between 2% and 3% per year), would cause carbon emissions to peak only at the end of the century, causing an estimated 3.5°C global temperature rise by 2100.

    The authors note that not only the mix of energy matters, but also the overall amount of energy consumed. The study also included ranges for high energy consumption and low energy consumption.

    The study adds to a large body of IIASA research on climate mitigation policy and the chances of achieving targets.

    “Earlier work on mitigation strategies by IIASA has shown the importance of demand-side measures, including efficiency, conservation, and behavioral change. Success in these areas may explain the difference between reaching 1.5C instead of 2C,” says IIASA Energy Program Director Keywan Riahi, who also contributed to the new work.

    A new model

    The study is one of the first published results from the newly developed FeliX model, a system dynamics model of social, economic, and environmental earth systems and their interdependencies. The model is freely available for download and use at http://www.felixmodel.com/.

    “Compared to other climate and integrated assessment models, the FeliX model is less detailed, but it provides a unique systemic view of the whole carbon cycle, which is vital to our understanding of future climate change and energy,” says IIASA Ecosystem Services and Management Program Director.

    This study received support from the European Research Council Synergy grant ERC-2013-SyG-610028


    Brian Walsh, Philippe Ciais, Ivan A. Janssens, Josep Peñuelas, Keywan Riahi, Felicjan Rydzak, Detlef P. van Vuuren, Michael Obersteiner. Pathways for balancing CO2 emissions and sinks. Nature Communications, 2017; 8: 14856 DOI: 10.1038/NCOMMS14856

    Human population growth offsets climate-driven increase in woody vegetation in sub-Saharan Africa

    Africa_woody vegetations_Pixabay2017
    Woody cover has actually increased over the past 20 years in large parts of Africa, and in particular in drylands. Researchers attribute much of this increase to changes in rainfall and the growing concentration of CO2 in the atmosphere. Photo by Pixabay

    The rapidly growing human population in sub-Saharan Africa generates increasing demand for agricultural land and forest products, which presumably leads to deforestation. Conversely, a greening of African drylands has been reported, but this has been difficult to associate with changes in woody vegetation. There is thus an incomplete understanding of how woody vegetation responds to socio-economic and environmental change.

    Deforestation in Africa has been high on the environmental agenda for decades. In a new study published in Nature Ecology and Evolution, researchers used a passive microwave Earth observation data set to demonstrate that the realities are more complex.

    Many earlier studies have overlooked that woody cover has actually increased over the past 20 years in large parts (~30%) of Africa, and in particular in drylands. This increase explains the observed ‘greening’ of drylands, both north and south the Equator. Authors further find that much of this increase may be explained by changes in rainfall and the growing concentration of CO2 in the atmosphere. In humid parts of Africa trends in woody cover are more diverse. Negative trends dominate where population density is high, and often in areas with dense forests with high ecological and economic value. The agreement between the map showing woody cover changes and the one with human population growth is so striking that statistics are almost needless to transport the message:


    The findings thus contradict, on one hand, generally held views of loss of woody cover in drylands, e.g. in the Sahel-belt across Africa, yet on the other hand it supports the concerns for deforestation, due to agricultural expansion in more densely populated regions, and due to logging in the sparsely populated Congo basin.

    The positive and negative impacts of observed trends are difficult to balance (increase in carbon stocks, lower albedo due to greater woody cover in drylands may have a positive effect on rainfall, the loss of forests in certain humid areas may imply serious losses of biodiversity and ecosystem services…).”At continental scale, it is thus impossible to draw final conclusions, and difficult to state if positive and negative effects are balanced. Local and regional scaled studies have to be evaluated and combined with these continental scale attempts”, said Dr. Martin Brandt from University of Copenhagen.

    “Given that Africa’s population is expected to continue growing throughout much of this century, there is a clear need to sharpen natural resource management strategies to counter losses while taking advantage of increases in woody cover in drylands which are large enough to act as a carbon sink” said Dr. Aleixandre Verger from CREAF-CSIC.

    “The great new thing is that we are now able to localize and quantify areas of change and we are working hard to quantify the amount of carbon which is affected by observed changes. This knowledge is critical in the fight against climate change”, said Prof. Josep Peñuelas from CSIC-CREAF.

    Citation: Brandt, M., Rasmussen, K., Penuelas, J., Tian, F., Schurgers, G., Verger, A., Mertz, O., Palmer, J., Fensholt, R. 2017. Human population growth offsets climate driven woody vegetation increase in sub-Saharan Africa. Nature Ecology and Evolution, 1, 0081 (2017), doi: 10.1038/s41559-017-0081.

    Sequence of plant responses to droughts of different timescales: lessons from holm oak (Quercus ilex) forests

    Montserrat_Lluis Comas_2017
    Tree physiology, forest structure and site-specific factors interact to determine the response of forests to recurring annual droughts, however, the increasing frequency of extreme droughts is making Mediterranean forests vulnerable. Picture shows Quercus ilex forests standing on the slopes of the sacred Montserrat mountain. Photo by Lluís Comas


    The functional traits of plants in regions of the world with a Mediterranean climate have been shaped to tolerate periods of water deficit. These species are adapted to summer droughts but may not be able to cope with future increases in drought intensity, duration, and/or frequency.

    In a new study published in Plant Ecology & Diversity researchers review the mechanisms and traits of drought resistance and recovery of the holm oak (Quercus ilex), which they propose as a model species for Mediterranean-type ecosystems. The aim of the study was to understand the differences and links between the responses of Q. ilex to summer droughts, extreme droughts, and long-term drought experiments. A main goal was to provide an integral picture of drought responses across organizational and temporal scales for identifying the most relevant processes that are likely to contribute to determining the future of Mediterranean vegetation. Evidence from long-term drought experiments showed that acclimation processes from the molecular (e.g. epigenetic changes) to the ecosystem level (e.g. reductions in stand density) mitigate the effects of drought.

    Changes in leaf morphology and hydraulics, leaf-to-shoot allometry, and root functioning are among the key mechanisms for overcoming increasing drought. The duration of drought determines its severity in terms of canopy loss and stem mortality. Although Q. ilex can vigorously resprout after such episodes, its resilience may be subsequently reduced. In the future, higher frequency of return of extreme droughts will challenge thus the capacity of these forests to recover. The insights provided by this review of the complex interplay of processes that determine the response of trees to droughts of different duration, intensity, and frequency will also help to understand the likely responses of other resprouting angiosperms in seasonally dry ecosystems that share similar functional traits with Q. ilex.

    “The limits of plasticity in primary and secondary growth in relation to future drier and warmer conditions may be determinants for the persistence of some populations in their current structure and function”, said Dr. Adrià Barbeta from CSIC-CREAF.

    “We recommend that future research should keep on addressing the combined effect of consecutive extreme droughts and drier average conditions on the structure and function of plant communities, but with a special emphasis on the resilience after crown damage and on the access to the vital long-lasting deep water pools”, said Prof. Josep Peñuelas from CSIC-CREAF.

    Citation: Barbeta, A., Peñuelas, J. 2016. Sequence of plant responses to droughts of different timescales: lessons from holm oak (Quercus ilex) forests. Plant Ecology & Diversity, 9:4, 321-338, doi: 10.1080/17550874.2016.1212288

    Future climate change will affect plants and soil differently

    Reinsch_Sci reports_2017
    Changes of aboveground net primary production and soil respiration in response to drought indicated that wet systems had an overall risk of increased loss of C but drier systems did not. Photo by: Pixabay


    In a new study published in the Nature journal Scientific Reports, researchers have found that soil carbon loss is more sensitive to climate change compared to carbon taken up by plants. In drier regions, soil carbon loss decreased but in wetter regions soil carbon loss increased. This could result in a positive feedback to the atmosphere leading to an additional increase of atmospheric CO2 levels.

    Scientists analysed data from seven climate change experiments across Europe to show how European shrubland plant biomass and soil carbon loss is affected by summer drought and year-around warming.

    The research was conducted by a group of European and American scientists including Marc Estiarte and Josep Peñuelas from CSIC-CREAF.

    The authors showed that soil carbon loss is most responsive to change in soil water. Soil water plays a critical role in wet soils where water logging limits decomposition processes by soil biota resulting in a build-up of soil carbon as peat. Drying of the soil removes this limitation resulting in soil carbon loss. In contrast in drier soils, reduced rainfall reduces soil water below the optimum for soil biota resulting in a decrease in soil carbon loss.

    Most of the earth’s terrestrial carbon is stored in soil. The world’s soil carbon stocks are estimated to be circa 2000 gigatonnes (1 gigatonne = 1 000 000 000 000 kilograms) of carbon. The researchers showed that drought decreases and increases soil carbon more predictably than warming.

    Dr Sabine Reinsch, the first author on the paper and a Soil Ecologist at the Centre for Ecology & Hydrology in Bangor, said, “This cross European study enabled us, for the first, time to investigate plant and soil responses to climate change beyond single sites.

    “Putting ecosystem responses to climate change into the wider context of natural climate gradients helps us to understand the observed responses of plants and soils better.”

    Professor Penuelas, the Head of the Global Ecology Unit CREAF-CSIC and co-author on the paper, Prof Claus Beier and Prof. Bridgette Emmet, as senior authors of the study commented that “The study highlights and illustrates new and fundamental understanding related to the response of ecosystems to climate change.

    “By conducting the same experiment at different moisture and temperature conditions across the European continent, it has become clear and visible how the pressure from climate change factors may act differently, and sometimes even opposite, across these conditions”.

    “These differences are important for our overall assessment of future ecosystem responses to climate change, but the study also shows that they can be understood and to some extent predicted.” “These results emphasize how sensitive soil processes such as soil respiration are to environmental change. “

    Dr Marc Estiarte, researcher at Spanish research centre CREAF-CSIC and co-author on the paper, said, “In contrast to the soils, reducing precipitation was not a threat to plant productivity in wetter sites, and in the drier sites plants resisted proportionally more than in intermediate sites, whose aboveground productivity was shown more sensitive. This illustrates the clear difference in sensitivity of the soils compared to the plants across the climate gradient.”

    The new paper in Scientific Reports considers plant and soil responses to drought and warming only across European shrublands. There are several other biomes in the world where plant and soil responses to climate change could be different.

    “Understanding the responses of plants and soils in other biomes will provide a better understanding of climate change and the effects on global plant and soil interactions and the feedbacks to climate”, said Prof. Josep Penuelas from CREAF-CSIC Barcelona.

    Paper reference

    Reinsch, S. Estiarte M., Penuelas J. et al. ‘Shrubland primary production and soil respiration diverge along European climate gradient,’ Scientific Reports. Published online 3 March 2017. DOI: 10.1038/srep43952

    The paper is available as an open access document via this URL: www.nature.com/articles/srep43952

    Pharmaceuticals and Personal-Care Products in Plants


    Pharmaceuticals and personal-care products reach plants predominantly from the use of reclaimed wastewater for irrigation. Photo by Pixabay

     Pharmaceutical and personal-care products (PPCPs) for human and animal use are increasingly released into the environment.

    Plants act as excellent tracers of global pollution because they are present in almost all areas of the planet and accumulate chemical compounds present in the atmosphere, in the water with which they are irrigated, and in the soil on which they grow.

    PPCP removal from plants for waste water treatment is incomplete, and the dispersal of these compounds into the environment and accumulation in plants mostly occurs from irrigating with reused water and from the application of biosolids and manure to land.

    In a featured article in the journal Trends in Plant Science, UVIC and CREAF-CSIC researchers highlighted the potential of plants as biomonitors of PPCPs in the environment and the risk that the dietary intake of these PPCP-contaminated plants could have on the entire biosphere including on human health, even at low concentrations.

    “Plants accumulate PPCP at concentrations that can be toxic to plants, plant microbiota, and soil microorganisms and thus affect nutrient cycling, food webs and ecosystem functioning. Furthermore, the risk to humans from dietary intake of these PPCP-contaminated plants (mostly crops) is uncertain but warrants deep consideration”, said Dr. Mireia Bartrons from Universitat de Vic, Barcelona.

    “Further attention has recently been given to the effects of human and veterinary antibiotics. They dramatically affect the structure and function of soil microbial communities and promote the emergence of multidrug-resistant human pathogens that increasingly threaten successful anti-biotic treatment of bacterial infections”, said Prof. Josep Penuelas from CREAF-CSIC Barcelona.

    Citation: Bartrons, M., Peñuelas, J. 2017. Pharmaceuticals and Personal-Care Products in Plants. Trends in Plant Science, (2017) 22, Issue 3, 194–203. doi: 10.1016/j.tplants.2016.12.010.

    Phosphorus accumulates faster than nitrogen globally in freshwater ecosystems under anthropogenic impacts


    Underwater image of a lake. Photo by Pexels

    Human activities have drastically accelerated Earth’s major biogeochemical cycles, altering the the nitrogen (N) and phosphorus (P) cycles.

    Combined effects of cumulative nutrient inputs and biogeochemical processes that occur in freshwater under anthropogenic eutrophication could lead to myriad shifts in N:P stoichiometry in global freshwater ecosystems, but this was not yet well-assessed.

    In a new study in the journal Ecology Letters researchers from Peking University and CREAF-CSIC evaluated the characteristics of N and P stoichiometries in bodies of freshwater and their herbaceous macrophytes across human-impact levels, regions and periods.

    Freshwater and its macrophytes had higher N and P concentrations and lower N:P ratios in heavily than lightly human-impacted environments, further evidenced by spatiotemporal comparisons across eutrophication gradients. N and P concentrations in freshwater ecosystems were positively correlated and N:P ratio was negatively correlated with population density in China.

    “Our findings indicate that anthropogenic eutrophication might thus shift aquatic ecosystems from a state of predominant P limitation to being potentially limited or co-limited by N, or by other factors such as light, especially in rapidly developing regions such as China” said Zhengbing Yan, researcher from Peking University.

    “These results indicate a faster accumulation of P than N in human-impacted freshwater ecosystems, which could have large effects on the trophic webs and biogeochemical cycles of estuaries and coastal areas by freshwater loadings, and reinforces the importance of rehabilitating these ecosystems”, said Prof. Josep Penuelas from CREAF-CSIC Barcelona.

    Citation: Yan, Z., Han, W., Penuelas, J., Sardans, J., Elser, J.J., Du, E., Fang, J. 2016. Phosphorus accumulates faster than nitrogen globally in freshwater ecosystems under anthropogenic impacts. Ecology Letters 19, (2016), 1237-1246. doi: 10.1111/ele.12658

    Plausible rice yield losses under future climate warming

    Rice fields, researchers analyze the sensitivity of rice yield to climate warming. Photo by Pixabay
    Rice fields, researchers analyze the sensitivity of rice yield to climate warming. Photo by Pixabay

    Rice is the staple food for more than 50% of the world’s population. Reliable prediction of changes in rice yield is thus central for maintaining global food security. This is an extraordinary challenge.

    In a new study in the journal Nature Plants researchers compare the sensitivity of rice yield to temperature increase derived from field warming experiments and three modelling approaches: statistical models, local crop models and global gridded crop models.

    Field warming experiments produce a substantial rice yield loss under warming, with an average temperature sensitivity of −5.2 % per degree of warming. Local crop models give a similar sensitivity (−6.3 %), but statistical and global gridded crop models both suggest less negative impacts of warming on yields (−0.8 % and −2.4 7%, respectively).

    Using data from field warming experiments, researchers further propose a conditional probability approach to constrain the large range of global gridded crop model results for the future yield changes in response to warming by the end of the century (from −1.3% to −9.3% per degree of warming). The constraint implies a more negative response to warming (−8.3 %) and reduces the spread of the model ensemble by 33%. This yield reduction exceeds that estimated by the International Food Policy Research Institute assessment (−4.2 to −6.4% ).

    “Our study suggests that without CO2 fertilization, effective adaptation and genetic improvement, severe rice yield losses are plausible under intensive climate warming scenarios” said Dr. Chuang Zhao, researcher from Peking University.

    “The long-term perspective of climate change allows us to prepare agricultural production systems for this challenge, but suitable policies must be put in place in the near future, given that targeted research on adaptation options and their large-scale implementation will require considerable time”, said Prof. Josep Penuelas from CREAF-CSIC Barcelona.

    Citation: Zhao, C., Piao, S., Wang, X., Huang, Y., Ciais, P., Elliott, J., Huang, M., Janssens, I.A., Li, T., Lian, X., Liu, Y., Müller, C., Peng, S., Wang, T., Zeng, Z., Penuelas, J. 2016. Plausible rice yield losses under future climate warming. Nature Plants 3, 16202 (2016), doi: 10.1038/nplants.2016.202.

    Losses of soil carbon under climate warming might equal U.S. emissions

    Carbon stores are greatest in places like the Arctic and the sub-Arctic, where the soil is cold and often frozen Photo by SHUTTERSTOCK


    A new global analysis finds that warming temperatures will trigger the release of trillions of kilograms of carbon from the planet’s soils, driven largely by the losses of carbon in the world’s colder places.

     See short video about this paper: https://youtu.be/IrKOpPJIbXA

    New Haven, Conn. – For the past two decades, scientists have speculated that rising global temperatures may alter the ability of soils to store huge amounts of carbon. If warming accelerates the release of carbon stored in the soil, it could trigger a dangerous feedback effect that could have runaway effects on climate change. Yet, despite thousands of studies around the world, we have remained unclear about whether soil carbon storage will increase or decrease in response to warming.

    Finally, a global perspective has allowed us to see past the mixed results of single-site studies to see the global patterns in this effect.

    In a new study in the journal Nature researchers find that warming will drive the loss of trillions of kg of carbon from the soil. A conservative estimate by the researchers suggest that this value will exceed 55 trillion kg by 2050.

    This value would represent up to 17% on top of current anthropogenic emissions that we expect over that time.

    The results are based on an analysis of soil carbon data from dozens of warming experiments conducted all over the world in the past 20 years.

    Using this worldwide dataset, the researchers generated a global map of the sensitivity of soil carbon to warming, showing that carbon loss is greatest in the world’s colder places, at high latitudes, where massive stocks of carbon have built up over thousands of years and slow microbial activity has kept them relatively secure.

    “Soil carbon stores are greatest in places like the Arctic and the sub-Arctic, where the soil is cold and often frozen. In those conditions microbes are less active and so carbon has been allowed to build up over many centuries,” said lead author Thomas Crowther, at the Yale School of Forestry & Environmental Studies (F&ES).

    “But as you start to warm those areas, the microbes become more active, that’s when the carbon losses are likely to happen,” Crowther said. “The scary thing is, these cold regions are the places that are expected to warm the most under climate change.”

    The study predicts that for one degree of warming, about 30 petagrams of soil carbon will be released into the atmosphere, or about 2-3 times as much as is emitted annually due to human-related activities. This is a sobering prospect, given that the planet is likely to warm by 2 degrees Celsius by mid-century.

    Other scientists on the team include Marc Estiarte and Josep Peñuelas from CREAF, as well as collaborating researchers from more than 30 other institutions.

    Marc Estiarte commented on the value of the results: “We suspected that cold regions were key because warming could potentially reverse the carbon-accumulating pressure that cold temperatures have been exerting since such a long time”

    The results represent a warn because “the vulnerability of the northern soil carbon pool is a threat to the stabilization of the CO2 concentrations in the atmosphere due to the positive feedback that can unfold between climate warming and soil carbon losses to the atmosphere”, in the words of Josep Peñuelas.

    Understanding these processes at a global scale is critical for our understanding of climate change. “Getting a handle on these kinds of feedbacks is essential if we’re going to make meaningful projections about future climate conditions. Only then can we generate realistic greenhouse gas emission targets that are effective at limiting climate change,” said Crowther.

    More information: T. W. Crowther et al, Quantifying global soil carbon losses in response to warming, Nature (2016). DOI: 10.1038/nature20150

    A remotely sensed pigment index reveals photosynthetic phenology in evergreen conifers

    Boreal forest
    Boreal forest, researchers find a close correspondence between seasonally changing foliar pigment level and evergreen photosynthetic activity Photo by ŠtefanŠtefančík

    In evergreen conifers, where the foliage amount changes little with season, accurate detection of the underlying “photosynthetic phenology” from satellite remote sensing has been difficult, causing errors in terrestrial photosynthetic carbon uptake models. This represents a challenge for global models of ecosystem carbon uptake.

    In a new study in the journal Proceedings of the National Academy of Sciences researchers find a close correspondence between seasonally changing foliar pigment levels, expressed as chlorophyll/carotenoid ratios, and evergreen photosynthetic activity, leading to a “chlorophyll/carotenoid index” (CCI) that tracks evergreen photosynthesis at multiple spatial scales.

    When calculated from NASA’s Moderate Resolution Imaging Spectroradiometer satellite sensor, the CCI closely follows the seasonal patterns of daily gross primary productivity of evergreen conifer stands measured by eddy covariance.

    This discovery provides a way of monitoring evergreen photosynthetic activity from optical remote sensing, and indicates an important regulatory role for carotenoid pigments in evergreen photosynthesis. “This methodology could improve the assessment of the evergreen component of the terrestrial carbon budget, which has been elusive” said Prof. Josep Peñuelas.

    “Improved methods of monitoring photosynthesis from space can improve our understanding of the global carbon budget in a warming world of changing vegetation phenology”, said Prof. John Gamon.


    Citation: Gamon, J., Huemmrich, J.K.F., Wong, C.Y.F., Ensminger, I., Garrity, S., Hollinger, D.Y., Noormets, A., Peñuelas, J. 2016. A remotely sensed pigment index reveals photosynthetic Q:1 phenology in evergreen conifers. Proceedings of the National Academy of Sciences, 2016. In press

    Study Finds Limited Sign of Soil Adaptation to Climate Warming

    Soil warming experiment at Toolik Station Photo by Jim Tang(1)
    This photo shows measurements of carbon flux from soil at Toolik Field Station in Arctic Alaska. Credit: Jianwu Tang


     WOODS HOLE, Mass. — While scientists and policy experts debate the impacts of global warming, the Earth’s soil is releasing roughly nine times more carbon dioxide to the atmosphere than all human activities combined. This huge carbon flux from soil, which is due to the natural respiration of soil microbes and plant roots, begs one of the central questions in climate change science. As the global climate warms, will soil respiration rates increase, adding even more carbon dioxide to the atmosphere and accelerating climate change?

    Previous experimental studies of this question have not produced a consensus, prompting Marine Biological Laboratory scientists Joanna Carey, Jianwu Tang and colleagues to synthesize the data from 27 studies across nine biomes, from the desert to the Arctic. Their analysis is published this week in Proceedings of the National Academy of Sciences. This represents the world’s largest dataset to date of soil respiration response to experimental warming.

    One prediction from the synthesis is that rising global temperatures result in regionally variable responses in soil respiration, with colder climates being considerably more responsive. “Consistently across all biomes, we found that soil respiration increased with soil temperature up to about 25° C (77° F),” says Carey, a postdoctoral scientist in the MBL Ecosystems Center. Above the 25° C threshold, respiration rates decreased with further increases in soil temperature.

    “That means the Arctic latitudes, where soil temperatures rarely, if ever, reach 25° C , will continue to be most responsive to climate warming. Because there is so much carbon stored in frozen soils of the Arctic, this has really serious repercussions for future climate change,” Carey says.

    Soil scientists are struggling to find evidences of soil acclimation to warming, as indicated by some individual field experiments, but the current study found limited evidence of it.

    “The occurrence of acclimation would provide some relieve on the positive feedback between warming and CO2 release by respiration from soil” says Marc Estiarte, a member of the research teams at CREAF.

    The information provided by the study will be critical to improve the soil-atmosphere interactions in the Earth-system models. The results of the study “will greatly improve our mechanistic understanding of how carbon dynamics change with climate warming”, in the words of Josep Peñuelas, a member of the research teams at CREAF

    To understand how global carbon in soils will respond to climate change, the authors stress, more data are needed from under- and non-represented regions, especially the Arctic and the tropics.



    Carey, Joanna A. et al (2016) Temperature response of soil respiration largely unaltered with experimental warming. Proc. Natl. Acad. Sci. DOI: 10.1073/pnas.1605365113

    Científics alerten a la revista Scientific Reports de l’extensa acumulació de contaminants orgànics a la vegetació arreu del planeta

    Un article publicat a la revista Scientific Reports alerta d’una extensa acumulació de contaminants orgànics a la vegetació arreu del planeta. L’article ha recollit, analitzat i comparat les dades de 79 estudis sobre aquesta matèria publicats entre 1979 i 2015, més de la meitat dels quals incloïen resultats d’àrees rurals i remotes.
    El treball l’ha elaborat la doctora en Biologia i professora de la Universitat de Vic – Universitat Central de Catalunya Mireia Bartrons, juntament amb Jordi Catalan i Josep Peñuelas, ambdós investigadors membres del CREAF, el centre públic de recerca en ecologia terrestre i anàlisi del territori que genera coneixement i metodologies per a la conservació, la gestió i l’adaptació del medi natural al canvi global.

    See more at: http://www.uvic.cat/cient%C3%ADfics-alerten-la-revista-scientific-reports-de-l%E2%80%99extensa-acumulaci%C3%B3-de-contaminants-org%C3%A0nics-la#sthash.urpo4Pl8.dpuf

    See more at: http://www.uvic.cat/

    IMBALANCE-P article on how ocean acidification will impact marine life

    A new analysis by Ligia Azevedo from IIASA and collaborators provides a holistic assessment of the impacts of climate change and ocean acidification on marine organisms including coral, shellfish, sea urchins, and other calcifying species. Please, find more detailed information here.

    More than 30% of phosphorus emitted to the atmosphere is a result of human activities

    According to the study of the IMBALANCE-P ERC Synergy Grant researchers, China and India contributes 43% of this amount. For decades it had been thought that human activities were responsible for only around 5% of atmospherically-circulating phosphorus.

    More phosphorus in the air means more phosphors deposited on the ground. This can boost plant growth and the capacity to sequester atmospheric CO2; for that reason human activities may be altering the phosphorus and carbon cycles to a degree which was previously unknown.


    December 15th 2014. Researchers of the IMBALANCE-P ERC Synergy Grant are working on the most realistic planetary atmospheric phosphorus budget done to date. Phosphorus is an essential nutrient for life and also plays a fundamental role in agriculture and world food security. Phosphorus is found in mineral reserves and in living beings, and despite being much less known, phosphorus is also in the atmosphere. Before the industrial era phosphorus was only naturally emitted to the atmosphere due to volcanic explosions, emissions of biogenic aerosols, and forest fires, in addition to being transported in continental dust and in marine salt. Now, the article published in Nature Geoscience has revealed the impact that human activities have had and are having on the cycle of phosphorus in the atmosphere. The team of international researchers publishing this information has shown that more than 30% of phosphorus currently emitted to the atmosphere is the result of human activities, basically from the burning of coal and biomass, whereas to date it was thought that this number was closer to 5%.

    According to the results, the total quantity of phosphorus emitted to the atmosphere has increased 30% in the previous fifty years as a result of a doubling of emissions produced by human beings. Currently, 43% of anthropogenic phosphorus emissions to the atmosphere are from China and India, while European emissions have continued to decline year after year.

    To carry out the study, the researchers created an inventory of natural and anthropic sources in 222 countries and territories for the period of 1960-2007. They used samples of coal from 13 different countries and samples of biomass of the 11 tree species and 9 crops most utilized as combustibles.

    Combustion emits CO2 to the atmosphere, but phosphorus helps store it 

    Phosphorus is a limiting nutrient for plant growth. A lot of phosphorus makes a soil fertile, helping plants grow and store more atmospheric CO2, reducing the greenhouse effect. “The results of this study show that the phosphorus cycle is strongly perturbed, more than we thought. This opens the possibility that there are many ecosystems which are being fertilized due to atmospheric phosphorus deposited in the ocean and above all on the ground, especially in tropical and subtropical forests of Asia and Africa. If these ecosystems are fertilized and their capacities for growth and carbon storage become greater, that means that atmospheric phosphorus is modifying the carbon cycle more than we thought up to now,” comments Josep Peñuelas, professor of the Spanish Council for Scientific Research (CSIC), who carries out research at CREAF.

    The opposite could be happening in Europe or in North America, where the rhythm of coal and biomass burning has slowed in recent years. While we shouldn’t forget that this reduction in the use of coal has significantly improved air quality, phosphorus emission rates have also declined, and now the soil is not receiving the same quantity of phosphorus as it did in the past, and forest growth could be slowed for this reason.

    “The policies designed to reduce the emissions of aerosols coming from fossil fuel burning represent a clear win-win option for improving air quality, while also reducing warming caused by the CO2 produced in combustion. However, this study suggests to us that we should also take into account the phosphorus which we will stop emitting when we evaluate the capacity of terrestrial and marine ecosystems to store CO2,” concludes Professor Peñuelas.

    Article: Wang, R. Balkanski, Y. Boucher, O. Ciais, P. Peñuelas, J. Tao, S. (2014) Significant contribution of combustion-related emissions to the atmospheric phosphorus budget Nature Geoscience

    Anna Ramon, communicator officer – CREAF

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