Monday, July 14, 2025

Forest trees and microbes choreograph their hunt for a ‘balanced diet’ under elevated CO2

In conditions mimicking a future atmosphere, 180-year-old English oaks traded-off “do it yourself” ways to access nutrients with “outsourcing” to soil microbes

University of Birmingham

Oak trees change their fine roots and ‘energise’ soil microbes by supplying them with a cocktail of small organic compounds, all to supplement the trees’ supply of essential nutrients when exposed to higher levels of carbon dioxide. This according to a study conducted at the unique University of Birmingham Institute of Forest Research’s Free Air CO2 Enrichment (BIFoR-FACE): a very large outdoor forest research facility.

In a study published in the Proceeding of the National Academy of Sciences (PNAS) today (Monday 14 July), researchers at BIFoR-FACE facility discovered that trees growing in a CO2-rich atmosphere tactically choreograph in-soil trading of carbon for nutrients through “do it yourself” and “outsourcing” strategies.

Perspex-sided root boxes, buried in the forest, allowed scientists at BIFoR-FACE access to the soil and roots below giant ~180 years old English oak trees growing in what is expected to be a mid-21st-century atmosphere; that is, an atmosphere containing over a third more CO2. The trees demonstrated their ability to respond to the change of atmosphere by adjusting multiple carbon investment strategies for sourcing soil nutrients.

The measurements, made after elevating CO2 in the forest for five years, showed that the oak trees increased their fine root branching systems by 73%, helping the trees explore more of the soil at all times of the year in a “do it yourself strategy” for finding and taking up nutrients. “Outsourcing” strategies, which involve trade partnerships with the soil microbial community, showed distinct seasonal patterns.

There was a 63% increase in the release (‘exudation’) of a cocktail of small organic molecules early in spring and autumn, which ‘prime’ soil microbes to release nutrients locked up in soils, so meeting tree nutrient demands. There was also a 17% increase in the amount of symbiotic root-associated fungi in autumn. More remarkable still, under elevated CO2, trees not only invested more carbon in their in-soil trading, they also altered the cocktail of chemicals released as root exudate, providing yet one more ‘outsourcing’ strategy to gain nutrients and sustain growth.

Dr Michaela Reay, the lead author from the University of Bristol, who carried out the research for this study while at the University of Birmingham, said:

“Roots do not simply take up nutrients and water from soils but rather exhibit smart and dynamic choreography, which involves highly specialized tradeoffs with soil microbes via varied nutrient exploration strategies throughout the year.

“These findings indicate that trees are more agile in optimizing growth than previously thought and will continue to be agile under higher CO2 atmospheres as long as soil nutrient supplies are sustained.”

Senior author Professor Sami Ullah from the University of Birmingham said:

“These mechanistic insights into how trees growing in future atmospheres acquire soil nutrients will have significant policy implications with direct relevance for climate mitigation initiatives such as the Paris Climate Agreement, the EU Green Deal, and the UK and EU net zero ambitions by 2050.”

“There is growing importance of forests to act as carbon sinks to contribute to offset essential CO2 emissions. Forest growth not only relies on CO2, but also requires an ample supply of soil nutrients to keep capturing and sequestering atmospheric CO2.”

Professor Iain Hartley from Exeter University said:

“Trees in this forest increasing their growth under elevated CO2 was slightly unexpected, and suggests mature temperate forests could play a key role in the fight against climate change. It remains important to investigate whether the strategies the oak trees are using will continue to allow for greater access to soil nutrients.”

Since the nutrients available in soil are not unlimited, the question now remains whether the extra carbon investment of trees in nutrient acquisition may eventually exhaust soil nutrient stocks. Forest responses to enforced changes, such as higher atmospheric CO2, can take many years to reach a new balance point; the ongoing research at BIFoR-FACE will assess whether nutrient supplies can continue to meet tree nutrient demands.

Journal

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2503595122

Article Title

Elevated CO2 alters relative belowground carbon investment for nutrient acquisition in a mature temperate forest

Article Publication Date

14-Jul-2025

Beyond health: The political effects of infectious disease outbreaks

Do infectious disease outbreaks breed political mistrust? Ore Koren, Indiana University Bloomington (USA), and Nils Weidmann, University of Konstanz (Germany), have found out that they do.

University of Konstanz

The COVID-19 pandemic has drawn the attention to the far-reaching social implications of emerging infectious diseases, bringing to mind similarly impactful events like the Black Plague in early modern Europe or the Spanish Flu after World War I. However, how emerging epidemics shape the development of political mistrust and instability has been underexplored so far. In a recently published article in the PNAS, political scientists Ore Koren (Indiana University Bloomington and currently a Humboldt Research Fellow at the University of Konstanz) and Nils Weidmann (University of Konstanz) give empirical evidence that individuals who experienced an infectious disease outbreak show significantly less trust in the political establishment. This is especially true for their confidence in the president, parliament and ruling party of the country they live in. “Our findings provide robust empirical evidence that deadly infectious disease outbreaks can exacerbate political polarization and undermine political stability,” the study concludes.

Declining trust in political institutions
The scientists focused on zoonotic disease outbreaks, i.e. diseases that originate in animal hosts and spread to humans, ranging from Ebola to H1N1 and Lassa, in several African countries. To evaluate the political impact of these outbreaks, the team combined outbreak data from the Geolocated Zoonotic Disease Outbreak Dataset (GZOD) with geolocated information from the Afrobarometer surveys. The latter database records the political and social attitudes of citizens in several African states through regular surveys, and also includes information about respondents’ trust in various political actors.

To ensure that the results capture only the impact of an outbreak, the researchers “matched” individuals affected by disease outbreaks in their proximity with similar individuals from the same country who were unaffected. This approach reveals that residents that have experienced an outbreak have significantly lower levels of trust in their country’s president, parliament, ruling party, electoral commission and police force. “An additional test of what happens when there are outbreaks in neighbouring countries – but not in one’s home country – shows that these outbreaks abroad have no effect on political trust in the home country. Thus, the effect does not travel across borders,” Weidmann points out.

Lessons learned
The loss of public trust could have various reasons, according to the researchers. It may be caused by the government’s failure to protect civilians from exposure, its mismanagement of the disease, its enforcement of containment or other unpopular policies. These insights, so Koren and Weidmann, emphasize how crucial it is for policymakers to combine public health strategies with measures designed to preserve and rebuild political trust in case of infectious disease outbreaks. “Governments should integrate trust-preservation strategies into their epidemic response plans and make sure their decision-making is transparent, and communication is clear and consistent”, says Koren. Weidmann adds: “During a health crisis, policymakers should rapidly engage with community leaders and trusted intermediaries to reinforce the legitimacy of public institutions.” Both researchers also recommend constantly monitoring public sentiment during health crises to help identify solutions that not only mitigate the spread of disease but also rebuild trust in political leadership, thus reinforcing democratic norms.

Key facts:

THIS PRESS RELEASE IS UNDER EMBARGO UNTIL MONDAY, JULY 14, 2025 AT 3:00 PM U.S. EASTERN TIME. The study “Infectious Disease Outbreaks Drive Political Mistrust” is scheduled to publish in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS) one day the week starting on July 14, 2025.
The study gives empirical evidence that individuals who experienced an infectious disease outbreak show significantly less trust in the political establishment.
Authors:
Ore Koren is Associate Professor of International Relations and Methodology at Indiana University Bloomington, U.S. From January to July 2025, he stayed at the University of Konstanz as a visiting professor on a Research Fellowship funded by the Alexander von Humboldt Foundation.
Nils Weidmann is Professor of Political Science and head of the "Communication, Networks and Contention" Research Group at the University of Konstanz, and is a Principal Investigator in the university's Cluster of Excellence "The Politics of Inequality".

Note to editors:

You can download a photo of Nils Weidmann here:: https://www.uni-konstanz.de/fileadmin/pi/fileserver/2025_extra/epidemien_auswirkungen_weidmann.jpg
Caption: Nils Weidmann is Professor of Political Science at the University of Konstanz and a principal investigator in the university's Cluster of Excellence "The Politics of Inequality".

Copyright: University of Konstanz Photo: Ines Janas

Note to editors:

You can download a photo of Ore Koren here: https://www.uni-konstanz.de/fileadmin/pi/fileserver/2025_extra/epidemien_auswirkungen_koren.jpeg

Caption: Ore Koren is Associate Professor of International Relations and Methodology at Indiana University Bloomington, U.S.

Journal

Proceedings of the National Academy of Sciences

For tastier and hardier citrus, researchers built a tool for probing plant metabolism

The new tool is poised to help plant breeders develop crops that are healthier and more resistant to drought and pests

University of California - San Diego

A new tool allows researchers to probe the metabolic processes occurring within the leaves, stems, and roots of a key citrus crop, the clementine. The big picture goal of this research is to improve the yields, flavor and nutritional value of citrus and non-citrus crops, even in the face of increasingly harsh growing conditions and growing pest challenges.

To build the tool, the team – led by the University of California San Diego – focused on the clementine (Citrus clementina), which is a cross between a mandarin orange and a sweet orange.

The effort is expected to expand well beyond the clementine in order to develop actionable information for increasing the productivity and quality of a wide range of citrus and non-citrus crops. The strategy is to uncover – and then make use of – new insights on how plants respond, in terms of metabolic activities in specific parts of the plant or tree, to environmental factors like temperature, drought and disease.

The tool, and the comprehensive genome-scale model for Citrus clementina, were published July 14, 2025 in the journal Proceedings of the National Academy of Sciences (PNAS).

The team is led by researchers at UC San Diego, in collaboration with researchers at UC Riverside and the Universidad Autónoma de Yucatán.

“Together we created a tool that will open the door for improved crop design and sustainable farming for Citrus clementia and a wide range of citrus and non-citrus crops,” said UC San Diego professor Karsten Zengler, the corresponding author on the new paper.

At UC San Diego, Zengler holds affiliations in the Department of Bioengineering, the Department of Pediatrics, the Center for Microbiome Innovation, and the Program in Materials Science and Engineering.

“Our data-driven modeling approach represents a powerful tool for citrus breeding and farming and for the improvement of crop yield and quality, meeting the escalating demand for high-quality products in the global market,” said Zengler.

The high-resolution genomic tool has been designed and built as a platform technology that can be expanded to help researchers improve a wide range of citrus and non-citrus crops. The actionable information is derived from a wide range of new mechanistic insights into how plant metabolism works within leaves, stems, roots and other tissues of key plant crops.

The highly curated and validated model of clementine metabolism, for example, contains 2,616 genes, 8,653 metabolites and 10,654 reactions.

“We generated seven biomass objective functions based on organ-specific metabolomics data for leaf, stem, root, and seed and experimentally validated the model – a challenge for a plant with an average lifespan of 50 years,” said Zengler. “This model represents one of the largest genome-scale models that has been built for any organism, including for humans.”

The model is called iCitrus2616. It captures Citrus clementina’s metabolism with exceptional accuracy and enables simulating economically-relevant scenarios.

For example, the researchers show how specific nutrients can improve the production of starch and types of cellulose, which in turn can enhance strength and rigidity of cell walls in citrus plants, which is useful for withstanding mechanical and drought stress.

The researchers also used the new tool to demonstrate how to increase flavor-related compounds in Citrus clementina such as flavonoids.

The team integrated organ-specific models for leaf, stem, and root into a whole plant model. Using this integrated whole-plant model, the researchers show how flavonoids and hormones are distributed through the entire plant.

Additionally, the team constrained the clementine metabolism model with gene expression data from symptomatic and asymptomatic leaf and root tissues across four seasons during citrus greening – which is caused by a bacterial infection. Citrus greening causes millions of dollars of agricultural damage annually.

This project has already revealed tissue-specific metabolic adaptations, including shifts in energy allocation, secondary metabolite production, and stress-response pathways under biotic stress and has provided a mechanistic understanding of disease progression.

The researchers note that this work represents a milestone in modeling higher organisms, specifically plants.

“I envision that these types of models will aid with crop breeding efforts in the near future. With these models, we are working to make critical plant breeding efforts more reliable and also faster,” said Zengler. “In preliminary follow-on research, we are already seeing examples of the positive impacts these models can have for data-driven strategies to optimize plant growth.”

Paper
Unravelling Organ-specific Metabolism of Citrus clementina, published in PNAS on 14 July 2025

Funders
US Department of Agriculture, National Institute of Food and Agriculture; California Department of Food and Agriculture; UC Multicampus Research Programs and Initiatives of the University of California

Authors
Co-first authors
Anurag Passi, Diego Tec-Campos

Additional authors
Manish Kumar, Juan D. Tibocha-Bonilla, Cristal Zuñiga, Beth Peacock, Amanda Hale, Rodrigo Santibáñez-Palominos, James Borneman, Karsten Zengler

Corresponding author
Karsten Zengler

Author Affiliations

University of California San Diego
Center for Microbiome Innovation in the UC San Diego Jacobs School of Engineering; Department of Pediatrics in the UC San Diego School of Medicine; Program in Materials Science and Engineering; Shu Chien-Gene Lay Department of Bioengineering in the UC San Diego Jacobs School of Engineering

University of California, Riverside
Department of Microbiology and Plant Pathology

Universidad Autónoma de Yucatán
Facultad de Ingeniería Química

Journal

Proceedings of the National Academy of Sciences

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Unravelling Organ-specific Metabolism of Citrus clementina

Article Publication Date

14-Jul-2025

Stay hydrated: New sensor knows when you need a drink

University of Texas at Austin

With another hot Texas summer underway, the threat of dehydration always looms. Though this condition can range from inconvenient to life-threatening, it's tough to track.

Researchers from The University of Texas at Austin are working to change that with the invention of a new non-invasive, wearable sensor designed to measure a user's hydration levels continuously, in real time. Such a device could help a football player stay hydrated on a hot September afternoon, keep a firefighter battling a blaze from getting too dried out, or just let an office worker know when it's time to make a trip to fill their water bottle.

“Dehydration is a silent threat that affects millions of people every day,” said Nanshu Lu, professor in the Cockrell School of Engineering's Department of Aerospace Engineering and Engineering Mechanics, who led the study published in the Proceedings of the National Academy of Sciences. “Our wearable sensor provides a simple, effective way to monitor hydration levels in real time, empowering individuals to take proactive steps to stay healthy and perform at their best.”

It uses bioimpedance, a technique that measures how electrical signals pass through the body, to track hydration levels. Using strategically placed electrodes, the sensor sends a small, safe electrical current through the arm.

How the electrical current flows through the body depends on the amount of water in the tissues. Water is a good conductor of electricity, so hydrated tissues allow the current to pass more easily, while dehydrated tissues resist the flow.

Data collected by the sensor is wirelessly transmitted to a smartphone, allowing users to monitor their hydration levels.

Researchers conducted several experiments to test the device, including a diuretic-induced dehydration study and a 24-hour free-living trial. In the dehydration study, participants took a diuretic medication to promote fluid loss, and their hydration levels were monitored using the wearable sensor and then tested against a urine sample. The results showed a strong correlation between changes in arm bioimpedance and body weight loss due to water loss.

“Our experiments demonstrated that arm bioimpedance is not only sensitive to hydration changes but also aligns closely with whole-body hydration measurements,” said Matija Jankovic, co-author of the study and a post-doctoral researcher in Lu's lab. “This means the sensor can be a reliable surrogate for tracking hydration levels, even during everyday activities like walking, working, or exercising.”

Traditional methods for assessing hydration, such as urine tests or blood analysis, are often invasive, time-consuming and impractical for continuous monitoring. Commercial hydration assessment devices typically require bulky equipment and stationary setups, limiting their use in everyday life.

Hydration is essential for human health. It plays a critical role in maintaining organ function, regulating body temperature, and supporting vital physiological processes.

Yet dehydration—a condition caused by insufficient water in the body—remains a common and often overlooked issue. Even mild dehydration can impair cognitive function, physical performance, and thermoregulation, while severe dehydration can lead to life-threatening conditions such as kidney stones, cardiovascular issues and heatstroke.

In addition to protecting workers in extreme environments, the device has potential applications in health care. Continuous hydration monitoring could aid in diagnosing and managing conditions such as kidney disease, cardiovascular issues and chronic dehydration.

"And hopefully, it could help our Longhorn student athletes compete and stay healthy on hot days," Lu said.

While the current version of the sensor tracks relative changes in hydration, future research aims to establish reference data for absolute hydration levels. This would involve collecting bioimpedance measurements from a large population to create a baseline for comparison.

The researchers also plan to explore new designs, such as breathable e-tattoos or sweat-wicking wearables, to improve comfort and performance during extended use. They hope to expand testing to larger groups and explore applications for other body segments, such as the forearm or thigh.

“This is just the beginning,” Lu said. “Our goal is to make simple hydration monitoring accessible to everyone."

Journal

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2504278122

Article Title

Wireless arm-worn bioimpedance sensor for continuous assessment of whole-body hydration

Article Publication Date

14-Jul-2025

Soil erosion in mountain environments accelerated by agro-pastoral activities for 3,800 years

Peer-Reviewed Publication

CNRS

Soil erosion in mountain environments accelerated by agro-pastoral activities for 3,800 years — image:
Pastoralism in the Alps. At a time when soil erosion threatens our societies by impacting biodiversity, carbon dioxide storage, and food production capacity, it is crucial to study and quantify its causes.
view more
Credit: © Julia GARAGNON / LSCE / CNRS Images

Over the last 3,800 years, agro-pastoral activities have accelerated alpine soil erosion at a pace 4-10 times faster than their natural formation. The history of this erosion has just been revealed for the first time by a research team led by a CNRS scientist1. The team has shown that high-altitude soil was degraded first, under the combined effect of pastoralism and forest clearing to facilitate the movement of herds. Medium- and low-altitude soil was then eroded with the development of agriculture and new techniques such as the use of ploughs, from the late Roman period to the contemporary period. The study has also revealed that the acceleration of soil erosion in mountain environments by human activities did not begin everywhere in the world in synchronous fashion.

This research, which will be published in the journal PNAS during the week of 14 July, reinforces the conclusion of a previous study by the authors2. In a global context of soil degradation affecting soil fertility, biodiversity, and water and carbon cycles, the authors are calling for the implementation of global protection measures.

These conclusions were obtained by comparing the isotope signature of lithium in sediments from Lake Bourget with those sampled from the rocks and soil of today. The samples were taken from the largest catchment area in the French Alps3. The data obtained was then compared to that from other regions in the world4. The DNA content in the sediments was also studied to identify the mammals and plants present during each period.

Core drilling barge on Bourget Lake in Savoie, during the drilling of the sediments accumulated at the bottom of the lake.Analysis using isotopic geochemistry for the sedimentary core samples that can reconstitute the evolution of erosion over a period of 10,000 years.

Credit

Notes

1 – From the Environments, Dynamics, and Mountain Territories Laboratory (CNRS/Université Savoie Mont Blanc) and the Paris Institute of Planetary Physics (CNRS/Institut de physique du globe de Paris/Université Paris Cité). The Paris-Saclay Geosciences Laboratory (CNRS/Université Paris-Saclay) was also involved. Scientists from l’Université Paris-Saclay, l’Université Savoie Mont Blanc, and the Paris Institute of Planetary Physics also took part in the research.

2 - Human-triggered magnification of erosion rates in European Alps since the Bronze Age. Rapuc, W., Giguet-Covex, C., Bouchez, J., Sabatier, P., Gaillardet, J., Jacq, K., Genuite, K., Poulenard, J., Messager, E., Arnaud, F. Nature communications, published on 10 February 2024.
DOI : https://doi.org/10.1038/s41467-024-45123-3

3 – The catchment area in question extends from the Chambéry basin to the peak of Mont Blanc.

4 – The Andes and North America.

Journal

Proceedings of the National Academy of Sciences

Article Title

Human and climate impacts on the alpine Critical Zone over the past 10,000 years

LA REVUE GAUCHE - Left Comment

Monday, July 14, 2025

Forest trees and microbes choreograph their hunt for a ‘balanced diet’ under elevated CO2

Journal

DOI

Article Title

Article Publication Date

Beyond health: The political effects of infectious disease outbreaks

Journal

For tastier and hardier citrus, researchers built a tool for probing plant metabolism

Journal

Method of Research

Subject of Research

Article Title

Article Publication Date

Stay hydrated: New sensor knows when you need a drink

Journal

DOI

Article Title

Article Publication Date

Soil erosion in mountain environments accelerated by agro-pastoral activities for 3,800 years

Core drilling barge on Bourget Lake in Savoie, during the drilling of the sediments accumulated at the bottom of the lake.Analysis using isotopic geochemistry for the sedimentary core samples that can reconstitute the evolution of erosion over a period of 10,000 years.

Credit

Journal

Article Title

About Me