Category Archives: Outreach

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

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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

“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:

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:

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.

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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. Continue reading