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  • The greening of the earth is approaching its limit

    A new study published in Science reveals that the fertilizing effect of excess CO2 on vegetation is decreasing worldwide. The lack of water and nutrients limit the greening observed in recent years and can cause CO2 levels in the atmosphere to rise rapidly, temperatures to increase and there to be increasingly severe changes in the climate.

    The greening of the earth is approaching its limit

    The lack of water and nutrients limit the greening observed in recent years and can cause CO2 levels in the atmosphere to rise temperatures to increase and to increase severe changes in the climate. Image: Public Domain

    Vegetation has a key role in mitigating climate change because it reduces the excess CO2 that we humans emit into the atmosphere. Just as when sportsmen and women are doped with oxygen, plants also benefit from the large amounts of CO2 that accumulate in the atmosphere. If more CO2 is available, they photosynthesize and grow more, which is called the fertilizing effect of CO2. When plants absorb this gas to grow, they remove it from the atmosphere and it is sequestered in their branches, trunk or roots.

    An article published in Science on December 2020 shows that this fertilizing effect of CO2 is decreasing worldwide, according to the text co-directed by Professor Josep Peñuelas of the CSIC at CREAF and Professors Songhan Wang (first author of the article) and Yongguang Zhang of the University of Nanjin, with the participation of CREAF researchers Jordi Sardans and Marcos Fernández. The study, carried out by an international team, concludes that the reduction has reached 50% progressively since 1982 due basically to two key factors: the availability of water and nutrients. “There is no mystery about the formula, plants need CO2, water and nutrients in order to grow. However much the CO2 increases, if the nutrients and water do not increase in parallel, the plants will not be able to take advantage of the increase in this gas”, explains Professor Josep Peñuelas. In fact, three years ago Prof. Peñuelas already warned in an article in Nature Ecology and Evolution that the fertilising effect of CO2 would not last forever, that plants cannot grow indefinitely, because there are other factors that limit them.

    If the fertilizing capacity of CO2 decreases, there will be strong consequences on the carbon cycle and therefore on the climate. Forests have received a veritable CO2 bonus for decades, which has allowed them to sequester tons of carbon dioxide that enabled them to do more photosynthesis and grow more. In fact, this increased sequestration has managed to reduce the CO2 accumulated in the air, but now it is over. “These unprecedented results indicate that the absorption of carbon by vegetation is beginning to become saturated. This has very important climate implications that must be taken into account in possible climate change mitigation strategies and policies at the global level. Nature’s capacity to sequester carbon is decreasing and with it society’s dependence on future strategies to curb greenhouse gas emissions is increasing”, warns Josep Peñuelas.

    The study published in Science has been carried out using satellite, atmospheric, ecosystem and modelling information. It highlights the use of sensors that use near-infrared and fluorescence and are thus capable of measuring vegetation growth activity.  

    Less water and nutrients

    According to the results, the lack of water and nutrients are the two factors that reduce the capacity of CO2 to improve plant growth. To reach this conclusion, the team based itself on data obtained from hundreds of forests studied over the last 40 years. “These data show that concentrations of essential nutrients in the leaves, such as nitrogen and phosphorus, have also progressively decreased since 1990,” explains researcher Songhan Wang.

    The team has also found that water availability and temporal changes in water supply play a significant role in this phenomenon. “We have found that plants slow down their growth, not only in times of drought, but also when there are changes in the seasonality of rainfall, which is increasingly happening with climate change,” explains researcher Yongguang Zhang.

    Reference article:

    Wang S, Zhang YG, Ju W, Chen, J, Ciais P, Cescatti A, Sardans J, Janssens IA, Sardans, J, Fernández-Martínez, M, … Penuelas J (2020). Recent global decline of CO2 fertilization effects on vegetation photosynthesis. Science, DOI: 10.1126/science.abb7772

    Source: Blog CREAF

    Country-Level Relationships of the Human Intake of N and P, Animal and Vegetable Food, and Alcoholic Beverages with Cancer and Life Expectancy


    The quantity, quality, and type (e.g., animal and vegetable) of human food and beverages have been correlated with cancer and life expectancy, although mostly at the population level and with many uncertainties. In a new study published in the journal Environmental Research and Human Health authors shed light on this association at country level. Picture source https://www.helpguide.org/

    The quantity, quality, and type (e.g., animal and vegetable) of human food have been correlated with human health, although with some contradictory or neutral results. We aimed to shed light on this association by using the integrated data at country level.

    In a new study published in the journal Environmental Research and Human Health authors hypothesized that higher N intake, lower N:P intake ratios, terrestrial animal food, and alcoholic beverages would be associated with cancer and shorter life expectancy (LE), whereas on the contrary, aquatic animals and vegetables would be associated with less cancer and longer LE.

    The study correlated elemental (nitrogen (N) and phosphorus (P)) compositions and stoichiometries (N:P ratios), molecular (proteins) and energetic traits (kilocalories) of food of animal (terrestrial or aquatic) and vegetable origin, and alcoholic beverages with cancer prevalence and mortality and LE at birth at the country level.

    Researchers used the official databases of United Nations (UN), Food and Agriculture Organization of the United Nations (FAO), Organization for Economic Co-operation and Development (OECD), World Bank, World Health Organization (WHO), U.S. Department of Agriculture, U.S. Department of Health, and Eurobarometer, while also considering other possibly involved variables such as income, mean age, or human development index of each country.

    The per capita intakes of N, P, protein, and total intake from terrestrial animals, and especially alcohol were significantly and positively associated with prevalence and mortality from total, colon, lung, breast, and prostate cancers. In contrast, high per capita intakes of vegetable N, P, N:P, protein, and total plant intake exhibited negative relationships with cancer prevalence and mortality. However, authors highlighted that a high LE at birth, especially in underdeveloped countries was more strongly correlated with a higher intake of food, independent of its animal or vegetable origin, than with other variables, such as higher income or the human development index.

    “Our analyses, thus, yielded four generally consistent conclusions. First, the excessive intake of terrestrial animal food, especially the levels of protein, N, and P, is associated with higher prevalence of cancer, whereas equivalent intake from vegetables is associated with lower prevalence. Second, no consistent relationship was found for food N:P ratio and cancer prevalence. Third, the consumption of alcoholic beverages correlates with prevalence and mortality by malignant neoplasms. Fourth, in underdeveloped countries, reducing famine has a greater positive impact on health and LE than a healthier diet”, concluded Prof. Josep Penuelas from CREAF-CSIC Barcelona.

    Reference: Penuelas, J., Krisztin, T., Obersteiner, M., Huber, F., Winner, H., Janssens, I.A., Ciais, P., Sardans, J. 2020. Country level relationships of the human intake of N and P, animal and vegetable food and alcoholic beverages with cancer and life expectancy. Environmental Research and Human Health, 2020, 17, 7240; doi:10.3390/ijerph17197240.

    Ozone affects plant, insect, and soil microbial communities: A threat to terrestrial ecosystems and biodiversity

    Ecological processes occurring at the ecosystem and foliar levels in a natural (not polluted)
    ecosystem (A) versus an ecosystem disturbed by increased levels of O3, figure shows the effects of elevated ozone (O3) on aboveground ecosystem processes. Figure by Agathokleous et al. Science Advances, 2020)

    Elevated tropospheric ozone concentrations induce adverse effects in plants. We reviewed how ozone affects (i) the composition and diversity of plant communities by affecting key physiological traits; (ii) foliar chemistry and the emission of volatiles, thereby affecting plant-plant competition, plant-insect interactions, and the composition of insect communities; and (iii) plant-soil-microbe interactions and the composition of soil communities by disrupting plant litterfall and altering root exudation, soil enzymatic activities, decomposition, and nutrient
    cycling. The community composition of soil microbes is consequently changed, and alpha diversity is often reduced.


    The effects depend on the environment and vary across space and time. We suggest that Atlantic islands in the Northern Hemisphere, the Mediterranean Basin, equatorial Africa, Ethiopia, the Indian coastline, the Himalayan region, southern Asia, and Japan have high endemic richness at high ozone risk by 2100.

    Reference: Agathokleous, E., Feng, Z., Oksanen, E., Sicard, P., Wang, Q., Saitanis, C.J., Araminiene, V., Blande, J.D., Hayes, F., Calatayud, V., Domingos, M., Veresoglou, S.D., Peñuelas, J., Wardle, D.A., De Marco, A.D., Li, Z., Harmens, H., Yuan, X., Vitale, M., Paoletti, E. 2020. Ozone affects plant, insect, and soil microbial communities: A threat to terrestrial ecosystems and biodiversity. Science Advances, 6(33): eabc1176. Doi: 10.1126/sciadv.abc1176

    Noves propostes per entendre com funciona la vegetació del planeta

    Un equip internacional –amb l’investigador del CSIC al CREAF Josep Peñuelas– explora els factors decisius del comportament vegetal i com incloure’ls als models predictius. El resultat es publica a Nature Plants i vol millorar la comprensió del cicle global del carboni i els serveis ecosistèmics i el seu futur si els boscos canvien pel canvi climàtic. 

    Bosc de coníferes. Public Domain.

    Bosc de coníferes. Public Domain.

    “Hem demostrat que si representem els principis d’evolució, autoorganització i maximització d’entropies (l’organització aleatòria d’alguns processos naturals) en els models,  podrem predir millor el comportament de les plantes complexes i la vegetació en general en relació amb els canvis ambientals”, explica Josep Peñuelas.

    Aquests factors ja s’han utilitzat anteriorment per separat per entendre aspectes concrets del funcionament de les plantes. Però les implicacions que tenen quan es combinen encara no s’havien analitzat a fons. Aprofundir-hi és important per conèixer millor com afectarà el canvi climàtic a aquestes dinàmiques. 

    Podeu llegir la investigació Organizing principles for vegetation dynamics a l’article que ha elaborat l’International Institute for Applied Systems Analysis, l’institut austríac que l’ha liderat.

    Article de referència:

    Franklin O, Harrison S, Dewar R, Farrior C, Brännström A, Dieckmann U, Pietsch S, Falster D, Penuelas J, et al. (2020). Organizing principles for vegetation dynamics. Nature Plants DOI: 10.1038/s41477-020-0655-x

    Font: Blog CREAF
    http://blog.creaf.cat/noticies/entendre-funcionament-vegetacio-planeta/

    Noves propostes per entendre com funciona la vegetació del planeta

    Un equip d’investigació internacional on ha participat en Josep Peñuelas explora els factors que més afecten el comportament de les plantes i com es poden incloure als models predictius per perfeccionar-los. L’estudi, publicat a Nature Plants, vol millorar la comprensió del cicle global del carboni i els serveis ecosistèmics i quin futur els espera si els boscos canvien davant el canvi climàtic. 

    Bosc de coníferes. Public Domain.

    Bosc de coníferes. Public Domain.

    “Hem trobat que si representem els principis d’evolució, autoorganització i maximització d’entropies (l’organització aleatòria d’alguns processos naturals) en els models,  podrien predir millor el comportament de les plantes complexes, i la vegetació en general, en relació amb els canvis ambientals”, explica en Josep Peñuelas, investigador del CSIC al CREAF.

    Aquests factors que proposa l’estudi ja s’han utilitzat anteriorment per separat per entendre aspectes concrets del funcionament de les plantes, però les implicacions que tenen quan es combinen encara no s’havien entès del tot. Profunditzar-hi és important per conèixer millor com afectarà el canvi climàtic a aquestes dinàmiques. 

    Podeu llegir més sobre la recerca en l’article que ha preparat  l’IIASAinstitució austríaca líder d’aquesta.

    Article de referència 

    Franklin O, Harrison S, Dewar R, Farrior C, Brännström A, Dieckmann U, Pietsch S, Falster D, Penuelas J, et al. (2020). Organizing principles for vegetation dynamics. Nature Plants DOI: 10.1038/s41477-020-0655-x

    Font: Blog CREAF

    Divergent responses of soil organic carbon to afforestation

    Afforestation is considered an effective strategy for increasing carbon sequestration and mitigating climate change and it has undoubtedly increased C stored in biomass. Afforestation has been widely implemented in many countries since the 1990s, increasing the area of planted forests globally by about 1.05 × 108 ha Picture by Pixabay

    Afforestation is the term used to refer the establishment of forests where previously there have been none, or where forests have been missing for a long time and has been proposed as an efficient method for removing carbon dioxide and mitigating climate change. The success of the goals of mitigation, however, depends on both the area of trees planted and the potential for carbon (C) sequestration of each afforestation. However, afforestation-induced changes in soil organic C (SOC) are poorly quantified due to the paucity of large-scale sampling data.

    In a new study published in the journal Nature plants authors provide the first comprehensive assessment of the afforestation impact on SOC stocks with a pairwise comparative study of samples from 619 control-and-afforested plot pairs in northern China.

    Authors found context-dependent effects of afforestation on SOC: afforestation increases SOC density (SOCD) in C-poor soils but decreases SOCD in C-rich soils, especially in deeper soil. Thus, the fixed biomass/SOC ratio assumed in previous studies could overestimate the SOC enhancement by afforestation. “By extrapolating the sampling data to the entire region, we estimate that afforestation increased SOC stocks in northern China by only 234.9 ± 9.6 TgC over the last three decades. The study highlights the importance of including pre-afforestation soil properties in models of soil carbon dynamics and carbon sink projections” explained Dr. Hong from the Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, China.

    The results of the study strongly suggest that estimated afforestation C sink potentials that do not account for background soil C stocks or the potentially negative effects of afforestation is overly optimistic. The authors claim that these findings also indicate that the assumption of a fixed ratio between soil and biomass C, which has been widely used in previous studies for estimating soil C stocks is unreliable.

    “According to this study pre-afforestation soil properties and original vegetation type need to be included in models of soil carbon dynamics; and extensive global-scale field investigations are required to improve the estimation of soil carbon stocks. Furthermore, the dependence of soil C changes on background soil C and tree species highlights the importance of site and species choices for maximizing afforestation C sequestration” said Prof. Josep Penuelas from CREAF-CSIC Barcelona.

    Reference: Hong, S., Yin, G., Piao, S., Chen, A., Cong, N., Dybzinski, R., Peñuelas, J., Zeng, H. 2020. Divergent responses of soil organic carbon to afforestation. Nature Sustainability, doi: https://doi.org/10.1038/s41893-020-0557-y.

    Durant l’estiu els boscos emeten més concentració de monoterpens, les fragàncies relacionades amb la salut de les persones

    Un estudi de l’ICTA, el CREAF, el CTFC i la UAB caracteritza per primera vegada la química forestal de l’aire per sota la copa dels arbres en un alzinar mediterrani. Les concentracions màximes de monoterpens, els compostos orgànics volàtils relacionats amb la salut humana, es produeixen al juliol i agost, a primera hora del matí i de la tarda.

    Montseny. Autor: Pixel (Wikimedia Commons)

    Montseny. Autor: Pixel (Wikimedia Commons)

    La recerca Human Breathable Air in a Mediterranean Forest: Characterization of Monoterpene Concentrations under the Canopy realitzada per l’investigador Albert Bach, de l’Institut de Ciència i Tecnologia Ambientals de la Universitat Autònoma de Barcelona (ICTA-UAB), ha comprovat que els monoterpens que emeten les plantes dins d’un alzinar tenen nivells màxims durant el juliol i l’agost. Els monoterpens són les fragàncies que emeten les plantes per comunicar-se, fer fora depredadors o captar l’atenció dels pol·linitzadors, entre d’altres. Són compostos orgànics volàtils actualment en estudi per les seves propietats antiinflamatòries, neuroprotectores i antitumorogèniques. En la recerca hi han col·laborat els investigadors del CREAF Joan Llusià, Iolanda Filella i Josep Peñuelas, juntament amb altres del Centre de Ciència i Tecnologia Forestal de Catalunya (CTFC), del Consejo Superior de Investigaciones Científicas (CSIC) i del Departament de Geografia de la UAB.

    L’estudi,  impulsat per la Fundació Bancària La Caixa i publicat a l’ International Journal of Environmental Research and Public Health, demostra que al bosc podem trobar aquests compostos a l’aire d’una forma molt variable. N’hi haurà més o menys depenent de l’estació de l‘any i l’hora del dia, sobretot segons la temperatura que faci, la radiació solar i la humitat. De fet, l’estudi ha comprovat que les màximes concentracions es produeixen durant el juliol i l’agost a primera hora del matí (de 6 a 8h) i de la tarda (de 13 a 15h), quan fa més calor i sol.

    Els resultats suggereixen que, durant l’estiu, les persones que caminen per aquest tipus de boscos estarien subjectes a una major absorció potencial de monoterpens en el seu torrent sanguini, especialment a primera hora del matí i a partir del migdia. Les concentracions obtingudes són similars o majors que en d’altres estudis que han demostrat la relació entre aquests compostos i la salut de les persones, no només al laboratori sinó també al bosc.

    Bosc i salut

    Quan estem en contacte amb el bosc experimentem una sèrie d’efectes en la nostra salut en general: als sistemes cardiovascular, immunitari, respiratori i nerviós, als que s’hi afegeixen canvis en el benestar fisiològic i psicològic.

    Tot i el seu paper rellevant al binomi bosc-salut, aquests compostos han estat poc estudiats per sota de la copa dels arbres, que és on té lloc la interacció amb les persones.  Per això, aquest estudi pioner obre un nou marc de recerca als boscos mediterranis i constitueix una aportació important per a la comunitat científica i de la sanitat pública.

    Més informació: Bach, A.; Yáñez-Serrano, A.M.; Llusià, J.; Filella, I.; Maneja, R.; Penuelas, J. (2020). Human Breathable Air in a Mediterranean Forest: Characterization of Monoterpene Concentrations under the Canopy. International Journal of Environmental Research and Public Health. https://doi.org/10.3390/ijerph17124391

    Font: Blog CREAF

    Variable reproduction goes beyond masting


    According to a new study published in the journal Nature Plants authors suggest that the first of the potential factors triggering a highly variable seed production could have been, before wind pollination and predators evolved, nutrient scarcity. Picture by Pixabay

    Nutrient scarcity, and climate, are long existing evolutionary forces that have selected for multiple plant traits and have constrained the physiology of plants since their early development.

    In a new study published in the journal Nature plants authors propose a mechanism by which nutrient scarcity may select for highly variable seed production, with weather patterns inducing masting synchrony across populations; they also discuss why wind-pollination and predator satiation cannot be the only selective pressures that select for highly variable reproduction.

    Nutrient availability is a direct determinant of the mean fruit production in agriculture and in the wild. In this study, authors discuss why low nutrient availability may have been an important factor selecting for highly variable and synchronized seed production, the latter in combination with adaptation to variability in long-term climate patterns.

    According to the authors, given the fact that temporally variable sexual reproduction in nature seems to be common, they conclude that factors others than wind pollination and predator satiation may have played a role in shaping this reproductive trait. “We suggest that one of these potential factors triggering a highly variable seed production, before wind pollination and predators evolved, may have been nutrient scarcity because of its role in determining the physiology of a broad range of organisms”, said Dr. Fernández-Martínez from University of Antwerp and collaborator of the Global Ecology Unit.

    “This mechanism, which could have originated during the early evolution of plants, may explain why, under low nutrient availability, nutrient-conservative plants with highly variable reproduction may have been preferentially selected in comparison to nutrient-spending plants (with more constant reproduction).” said Prof. Josep Penuelas from CREAF-CSIC Barcelona.

    Reference: Fernández-Martínez, M., Sardans, J., Sayol, F., LaMontagne, J.M., Bogdziewicz, M., Collalti, A., Hacket-Pain, A., Vacchiano, G., Espelta, J.M., Peñuelas, J., Janssens, I.A. 2020. Reply to: Nutrient scarcity cannot cause mast seeding. Nature Plants. DOI: 10.1038/s41477-020-0703-6.

    Trade-off between gymnosperm resistance and resilience increases forest sensitivity to drought

    According to a new study published in the journal Nature Ecology and Evolution the increase in gymnosperm sensitivity to drought suggests that their increasing intrinsic water use efficiency may not have alleviated the impacts of drought stress. Picture by Shutterstock

    The frequency and intensity of droughts have grown over the decades, leading to increased forest decline. The response of forest to drought can be evaluated by its sensitivity to drought (resistance) and the post-drought recovery rate (resilience). However, it remains uncertain how drought resistance and resilience of forests have changed across the space and over time under climate change.

    In a new study published in the journal Nature Ecology and Evolution authors assessed the spatio-temporal dynamics of forest resistance and resilience to drought over the past century (1901-2015) with global tree ring data records from 2935 sites and associated plant trait data. Authors point out that this study based on an analysis of long-term tree-ring data is the first one to report a trade-off in their recent trends between gymnosperm resistance and resilience to drought. According to the authors such decrease in drought resistance but increase in their drought resilience may potentially indicate a recent life-history strategy shift of gymnosperms in coping with changing climate and drought stress regimes.

    “Surprisingly, we found that the trade-off between resistance and resilience for gymnosperms, previously reported only spatially, also occurred at the temporal scale. In particular, drought resilience significantly increased but resistance decreased for gymnosperms between 1950-1969 and 1990-2009, indicating that previous models simulations may have underestimated the impacts of drought on gymnosperm-dominated forests under future climate change”, said the PhD student  Xiangyi Li from the Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, China.

    “We suggest that the altered ecosystem carbon cycle processes should be considered in the next generation of forest simulators to improve their predictive capacity of future ecosystem functioning and terrestrial carbon balance. The priority for further studies is to establish a network for long-term and synchronized observations of plant growth conditions and traits” said Prof. Josep Penuelas from CREAF-CSIC Barcelona.

    Reference: Li, X., Piao, S., Wang, K., Wang, X., Wang, T., Ciais, P., Chen, A., Lian, X., Peng, S., Peñuelas, J. 2020. Temporal trade-off between gymnosperm resistance and resilience increases forest sensitivity to extreme drought. Nature Ecology and Evolution.

    Plant Secondary Compounds in Soil and Their Role in Belowground Species Interactions.

    According to a new study published in the journal Trends in Ecology and Evolution, changes in the production of PSCs can lead to unforeseen consequences for soil structure and function and can disturb biological feedbacks on soil chemistry and biology, perhaps even on atmospheric chemistry and climate. Figure: © Trends in Ecology and Evolution, 2020.

    Secondary compounds (PSCs ) in plants (formed from primary metabolites in specific pathways) are major contributors to the chemical diversity of nature.. The distribution of PSCs is heterogeneous across the plant kingdom, and these compounds exhibit extensive variation both among and within species. Knowledge of the effect of PSCs on belowground interactions in the more diffuse community of species living outside the rhizosphere is sparse compared with what we know about how PSCs affect aboveground interactions.

    In a new study published in the journal Trends in Ecology and Evolution authors illustrate that PSCs from foliar tissue, root exudates, and leaf litter effectively influence such belowground plant–plant, plant–microorganism, and plant–soil invertebrate interactions.

    The study shows that soil is a theater of facilitation, symbiosis, and warfare deployed by plants and the various organisms living in it, and PSCs have a major role mediating many of these interactions. Plants and soil organisms have adapted to withstand, detoxify, or use the cocktail of PSCs originally meant to harm some of them. ”Therefore, understanding PSC-mediated relationships at the community scale and identifying the compounds involved in these interactions is important for better insight into the functioning of these systems and their evolution, especially in changing environments” said Dr. Bodil K. Ehlers from Aarhus University, Denmark

    According to the study climatic factors can induce PSC production and select for different plant chemical types. “Therefore, climate change can alter both quantitative and qualitative PSC production, and how these compounds move in the soil. This can change the soil chemical environment, with cascading effects on both the ecology and evolution of belowground species interactions and, ultimately, soil functioning” said Prof. Josep Penuelas from CREAF-CSIC Barcelona.

    “We encourage the creation of open, community-wide, curated, labeled, broad-spectrum PSC data sets across plant species and soils, because this would greatly increase the transfer of knowledge between scientists studying plants, microbes, and invertebrates in this biological belowground theatre” added Prof. Josep Penuelas from CREAF-CSIC Barcelona.

    .Reference: Ehlers, B.K., Berg, M.P., Staudt, M., Holmstrup, M., Glasius, M., Ellers, J., Tomiolo, S., Madsen, R.B., Slotsbo, S., Penuelas, J. 2020. Plant Secondary Compounds in Soil and Their Role in Belowground Species Interactions. Trends in Ecology & Evolution, doi: 10.1016/j.tree.2020.04.001.

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