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

Josep Peñuelas named Distinguished Scientist by Chinese Academy of Sciences

This award distinguish well established and internationally recognized scientists in their respective research fields, having obtained outstanding scientific accomplishment and prestigious international honors, awards or prizes.

The fellowship aims to create or strengthen partnerships between CAS host institutions and the recipients’ home institutions.

Continental mapping of forest ecosystem functions reveals a high but unrealized potential for forest multifunctionality


This study presents a new approach to quantify ecosystem functioning at scales relevant for policy makers. Photo by Pixabay.


Forests provide a number of functions related to key services such as timber production, climate regulation and recreation, and are important for the conservation of many plant and animal species. Thus humans require multiple services from ecosystems, but it is largely unknown whether trade-offs between ecosystem functions prevent the realisation of high ecosystem multifunctionality across spatial scales.

In a new study in the journal Ecology Letters scientists combined a comprehensive dataset (28 ecosystem functions measured on 209 forest plots) with a forest inventory dataset (105,316 plots) to extrapolate and map relationships between various ecosystem multifunctionality measures across Europe. These multifunctionality measures reflected different management objectives, related to key services (timber production, climate regulation and biodiversity conservation/recreation).

Authors found that different measures of forest multifunctionality tend not to tradeoff with each other, at both local and continental scales. “Within some areas there were strong synergies between different multifunctionality measures, indicating that even though they are currently uncommon, ‘win-win’ forest management strategies are possible and could be promoted in the future. “Using one of the most comprehensive assessments so far, our study therefore suggests a high but largely unrealised potential for management to promote multifunctional forests in Europe”, said Dr. van der Plas from Institute of Plant Sciences, University of Bern, Switzerland.

For the authors this study is a first step in reaching the ultimate goal of predicting how future ecosystem functioning and service provision will be altered by ongoing global trends, such as climate change), eutrophication and acidification or land-use change “Future studies could combine this approach with models on climate change, biodiversity change or management scenarios to investigate the impacts of these global trends for the future functioning and service provisioning of forests and other ecosystems”, said Prof. Josep Peñuelas from CREAF-CSIC Barcelona.


Journal Reference: van der Plas, F., Ratcliffe, S., Ruiz-Benito, P., Scherer-Lorenzen, M., Verheyen, K., Wirth, C., Zavala, M.A., Ampoorter, E., Baeten, L., Barbaro, L., Bastias, C.C., Bauhus, J., Benavides, R., Benneter, A., Bonal, D., Bouriaud, O., Bruelheide, H., Bussotti, F., Carnol, M., Castagneyrol, B., Charbonnier, Y., Cornelissen, J.C., Dahlgren, J., Checko, E., Coppi, A., Muhie Dawud, S., Deconchat, M., De Smedt, P., De Wandeler, H., Domisch, T., Finér, L., Fotelli, M., Gessler, A., Granier, A., Grossiord, C., Guyot, V., Haase, J., Hättenschwiler, S., Jactel, H., Jaroszewicz, B., Joly, F., Jucker, T., Kambach, S., Kaendler, G., Kattge, J., Koricheva, J., Kunstler, G., Lehtonen, A., Liebergesell, M., Manning, P., Milligan, H., Müller, S., Muys, B., Nguyen, D., Nock, C., Ohse, B., Paquette, A., Peñuelas, J., Pollastrini, M., Radoglou, K., Raulund-Rasmussen, K., Roger, F., Seidl, R., Selvi, F., Stenlid, J., Valladares, F., van Keer, J., Vesterdal, L., Fischer, M., Gamfeldt, L., Allan, E. 2018. Continental mapping of forest ecosystem functions reveals a high but unrealized potential for forest multifunctionality. Ecology Letters 21, Issue 1, 31–42, doi: 10.1111/ele.12868.


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

A celebration of Spain’s exemplary lab leaders

Meet the winners of Nature’s 2017 mentoring awards.

by Alison Abbott

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In the 1980s, Alicante was known only as a beach resort in southern Spain. Carlos Belmonte made it into a place where researchers could carry out international-level work in neuroscience. And in the 1970s, Margarita Salas created a school of molecular biology in Spain at a time when that science did not exist in the country’s minimal and internationally isolated research environment.

But these were not the main reasons that these two eminent researchers were jointly selected for the 2017 lifetime achievement award of the annual Nature Awards for Mentoring in Science. Belmonte, the founding director of the Institute of Neuroscience in Alicante, and Salas, a former director of the Spanish National Research Council’s Severo Ochoa Centre for Molecular Biology (CBMSO) in Madrid, were recognized by a panel of judges for their exemplary personal mentoring.

Throughout their careers, judges said, both recipients have given appropriate and  individual attention to the scientific development of the PhD students and postdocs under their supervision. In many cases, this support continued even after the trainees’ own careers were well under way.

For similar reasons, judges also co-awarded the Nature mid-career achievement mentoring prize to molecular biologist Carlos López-Otín at the University of Oviedo and physicist Lluís Torner, founding director of the Institute for Photonic Sciences (ICFO) in Barcelona. Nominators spoke of the ability of these scientists to instil confidence in self-doubting trainees, and of their motivational skills.

Keeping the flame

Judges said that all four winners have helped to develop a stronger science base in a country that remained at a scientific standstill during the 36-year military dictatorship of Francisco Franco, who ruled from 1939 until his death in 1975.

“It is very important to Spain to recognize the value of mentoring. As an evolving scientific society, we need to enhance mentoring as a relationship of support and trust between senior and junior scientists,” says ecologist Josep Peñuelas at the Autonomous University of Barcelona, who chaired the panel of judges. Although Spanish science is excellent in some fields, he adds, it remains poorly funded, yet excellent mentoring “helps to keep the flame”.

The Nature mentoring awards were founded in 2005 to draw attention to the importance of mentorship, a crucial component of a junior scientist’s career development that often goes overlooked and unrewarded. The awards are given in a different country each year. Each contender has to be nominated by five of their former trainees, from different stages of the mentor’s professional life; these five must describe the support they received while launching their own scientific careers. This year, awards were bestowed in Spain, and the two pairs of joint winners each share a €10,000 (US$12,000) purse. Winners received the awards on 4 December, in Madrid.

Each of the four winners, judges pointed out, developed new institutes or schools in which subsequent generations of scientists have matured under their supervision.

All four award winners fostered a sense of ‘family’ within their laboratories, mentees noted. Salas’s trainees, for example, are known colloquially as ‘the Margaritos’, and Torner’s as the ‘Infonians’. Many of the winners’ nominators have taken up top positions in labs in Spain and elsewhere. Yet they have continued to benefit from their mentors’ advice and guidance, they say, long after leaving the labs where they were once trainees.

Mentees emphasized how their mentors always made themselves available to listen, advise and give practical support — offering encouragement when assays failed to work, when things went wrong in the lab or in their personal lives, and when they felt like giving up. Nature’s recent global survey of PhD students (see demonstrates the crucial importance of mentorship to early-career researchers. Effective mentoring — including guidance from and recognition by an adviser — contributes more to respondents’ overall satisfaction with their PhD programme than does any other factor, the survey of 5,700 students found.

A new and better way

Belmonte’s nominators appreciated his creation of a strong scientific direction for the region of Alicante. “Academic life in the last years of Franco’s regime was extremely poor and dull, if not dead,” wrote one of Belmonte’s mentees. “Carlos arrived as a breath of fresh air into an impoverished atmosphere.”

Many also remarked on his personalized mentoring style. “He provided guidance, insight and criticism and at the same time allowed the development of my personal interests and space,” wrote one former trainee.

Salas, whose career also spanned Spain’s transition from dictatorship to hopeful democracy, worked to maintain the CBMSO as a thriving hub of science. “She ultimately constituted a school that cemented the field of molecular biology in the whole country,” said one of her mentees.

One of the people who nominated Salas said that, as a junior researcher in the molecular biologist’s lab, she had failed to get reproducible assays and had questioned her ability to be a scientist. “Margarita looked me in the eyes and said, ‘I trust you: you have good hands and these experiments will work.’ I calmed and tried again,” the mentee wrote. “Not long after that conversation, my first paper came out.”

Like Belmonte, López-Otín ended up not in one of Spain’s major scientific centres, but in a provincial town in Asturias, where he created an important centre for cancer and the biology of ageing. “Carlos has been a constant catalyst of scientific activities in Asturias, a region marked by decades of economic and social distress,” wrote one of his mentees.

Paths to independence

López-Otín’s mentees praised his ability to draw out and encourage even the shyest lab member. “Carlos gave me the strength to pursue an independent career as a principal investigator,” one wrote. “He made me feel that my career was a priority for him, and it is thanks to him that my career has advanced further than I would ever have imagined.” Another noted how López-Otín had encouraged trainees to read widely and think big. “Carlos told me that ground-breaking work comes from broad scientific knowledge, while overspecialization is the path to small science.”

Nominators said that López-Otín insisted on celebrating every accepted paper or project in the lab and was widely generous with advice. One scientist who was not in his lab, but who had found himself in difficulties, turned to him anyway. He found LópezOtín clearly busy, with lab members coming in for advice and e-mails pouring into his inbox. “But he still spent hours talking with me,” said the nominator. “He helped me refocus my passion for science.”

Science in Barcelona was underdeveloped when Torner accepted an offer in 2002 to be ICFO’s founding director. Today, the city is a thriving centre of scientific excellence, thanks to ICFO and other institutes that the regional government established around the same time.

Torner’s mentees commented on how he persuaded them to join ICFO instead of choosing more high-profile scientific institutes abroad. “Luís’s unique leadership convinced us that something different was being created and we wanted to be a part of it,” one mentee wrote. “None of us have regretted that decision.” Another mentee had been a visiting undergraduate from abroad when he first met Torner. “At the time, it was fair to say that Barcelona was not the best place in the world to do science,” the former trainee wrote. “Then I met Lluís and talked to him for five minutes — long enough to change all my plans, and switch to his field.”

Maximum motivation

One of Torner’s nominators recalls his “five-point take-home message: work hard, don’t settle for easy goals, get the most out of ICFO, pursue your dreams and let me know how I can help you get there.”

Philip Campbell, Nature’s editor-in-chief, notes that the awards competition has now taken place in 13 countries or regions, including the western United States, the Nordic countries, South Africa, Japan and China. “These are very varied cultures — and yet the key characteristics of outstanding mentors are remarkably similar. Spain’s great examples are no exception,” says Campbell, who established the awards. “They are extraordinary in their ability to nurture emerging scientists of great diversity.”