New analysis of landmark scurvy study leads to update on vitamin C needs

Peer-Reviewed Publication

UNIVERSITY OF WASHINGTON

It was wartime and food was scarce. Leaders of England’s effort to wage war and help the public survive during World War II needed to know: Were the rations in lifeboats adequate for survival at sea? And, among several experiments important for public as well as military heath, how much vitamin C did a person need to avoid the deadly disease scurvy?

In one experiment at the Sorby Research Institute in Sheffield, called the “shipwreck” experiment, volunteers were fed only what the navy carried in lifeboats. The grueling experiment resulted in more water and less food being carried in lifeboats. 

One of the more robust experiments run on human subjects during this time in England, which has had long-lasting public health consequences, was a vitamin C depletion study started in 1944, also at Sorby. This medical experiment involved 20 subjects, most of whom were conscientious objectors living in the building where many experiments, including the shipwreck experiment, were conducted. They were overseen by a future Nobel Prize winner, and detailed data was kept on each participant in the study.

“The vitamin C experiment is a shocking study,” said Philippe Hujoel, lead author of a new study on the Sorby vitamin C experiment, a practicing dentist and professor of oral health sciences in the UW School of Dentistry. “They depleted people’s vitamin C levels long-term and created life-threatening emergencies. It would never fly now.”

Even though two trial participants developed life-threatening heart problems because of the vitamin C depletion, Hujoel added, none of the subjects were permanently harmed, and in later interviews several participants said they would volunteer again given the importance of the research. 

Because of the war and food shortages, there was not enough vitamin C available, and they wanted to be conservative with the supplies, explained Hujoel, who is also an adjunct professor of epidemiology. The goal of the Sorby investigators was not to determine the required vitamin C intake for optimal health; it was to find out the minimum vitamin C requirements for preventing scurvy.  

Vitamin C is an important element in your body’s ability to heal wounds because the creation of scar tissue depends on the collagen protein, and the production of collagen depends on vitamin C. In addition to knitting skin back together, collagen also maintains the integrity of blood vessel walls, thus protecting against stroke and heart disease.

In the Sorby trial, researchers assigned participants to zero, 10 or 70 milligrams a day for an average of nine months. The depleted subjects were then repleted and saturated with vitamin C. Experimental wounds were made during this depletion and repletion. The investigators used the scar strength of experimental wounds as a measure of adequate vitamin C levels since poor wound healing, in addition to such conditions as bleeding gums, are an indication of scurvy.  

In the end, the Sorby researchers said 10 milligrams a day was enough to ward off signs of scurvy. Partly based on these findings, the WHO recommends 45 milligrams a day. Hujoel said that the findings of the re-analyses of the Sorby data suggest that the WHO’s recommendation is too low to prevent weak scar strength.  

In a bit of scientific detective work, Hujoel said he tracked down and reviewed the study’s data, and with the aid of Margaux Hujoel, a scientist with Brigham and Women’s Hospital/Harvard Medical School, put the data through modern statistical techniques designed to handle small sample sizes, techniques not available to the original scientists. The results of their work were published Monday in the American Journal of Clinical Nutrition.

The Hujoels discovered that the data from this unique study — which has been a cornerstone used by WHO and other agencies for establishing healthy levels of vitamin C in humans — needed more than an “eyeball method” of data assessment. 

“It is concluded that the failure to reevaluate the data of a landmark trial with novel statistical methods as they became available may have led to a misleading narrative on the vitamin C needs for the prevention and treatment of collagen-related pathologies,” the researchers wrote. 

“Robust parametric analyses of the (Sorby) trial data reveal that an average daily vitamin C intake of 95 mg is required to prevent weak scar strength for 97.5% of the population. Such a vitamin C intake is more than double the daily 45 mg vitamin C intake recommended by the WHO but is consistent with the writing panels for the National Academy of Medicine and (other) countries,” they add. 

The Hujoels’ study also found that recovery from a vitamin C deficiency takes a long time and requires higher levels of vitamin C. Even an average daily dose of 90 milligrams a day of vitamin C for six months failed to restore normal scar strength for the depleted study participants. 

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For more information, contact Philippe Hujoel at hujoel@uw.edu

Related UW study: Bleeding gums may be a sign you need more vitamin C in your diet

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JOURNAL

American Journal of Clinical Nutrition

DOI

10.1093/ajcn/nqab262

METHOD OF RESEARCH

Literature review

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Vitamin C and scar strength: analysis of a historical trial and implications for collagen-related pathologies

ARTICLE PUBLICATION DATE

16-Aug-2021

COI STATEMENT

None

 

Humble pond plant duckweed may help researchers to develop better crops

Rutgers-led study puts the spotlight back on the rapidly growing aquatic species

Peer-Reviewed Publication

RUTGERS UNIVERSITY

 

IMAGE: DUCKWEED, A TINY FRESHWATER FLOATING PLANT, IS AN EXCELLENT LABORATORY MODEL FOR SCIENTISTS TO DISCOVER NEW STRATEGIES FOR GROWING HARDIER AND MORE SUSTAINABLE CROPS IN AN AGE OF CLIMATE CHANGE AND GLOBAL POPULATION BOOM, A RUTGERS-LED STUDY FINDS. view more 

CREDIT: RUTGERS UNIVERSITY

New Brunswick, N.J. (Aug. 16, 2021) – Duckweed, a tiny freshwater floating plant, is an excellent laboratory model for scientists to discover new strategies for growing hardier and more sustainable crops in an age of climate change and global population boom, a Rutgers-led study finds.

“There is a need for new models to tackle complex molecular and ecological processes in plant biology using multidisciplinary approaches,” said the study’s senior author Eric Lam, a Distinguished Professor in the Department of Plant Biology at Rutgers University-New Brunswick. “Duckweeds are well suited to play an important role in these endeavors.”

The study appears in the journal The Plant Cell.

Duckweed (family Lemnaceae), the smallest flowering and fastest growing plant on Earth, has many benefits, including providing wildlife habitat and being a sustainable source of food, livestock feed and biofuel. But also can spread rapidly and deprive ponds of oxygen, thereby killing fish and beneficial algae when not managed properly.

Named for its global distribution (like ducks) and its rapid growth (like weeds), duckweed was commonly used in lab research from 1950 to 1990 before being largely replaced in the genomics era by thale cress or mouse-ear cress (Arabidopsis thaliana), a model plant in the mustard family that offers facile genetics and a small genome.

But advances in genomic technologies over the past decade and the growing need to find alternative and more sustainable crops have renewed interest in duckweed as a model to enable discoveries in diverse fields from plant biology and ecology to chronobiology.

Researchers from Rutgers, the Salk Institute and an international team of specialists reviewed the anatomy, growth, physiology and molecular characteristics of duckweed, which has unique characteristics compared to other model plants that make them excellent candidates as model plants to tackle complex biological questions. One example is that genome sequences from multiple species of duckweed showed that these aquatic plants have a smaller number of genes compared to other model plant species, which may make duckweed a simpler plant model to characterize each gene's function.

In addition, recent studies published by collaborating teams at Rutgers and the Salk Institute revealed that the smallest member of the duckweed family, Wolffia, may economize its energy for growth by minimizing the level of gene control over the daily day-night cycle.

“We thus suggest that the duckweed plant family is an excellent platform to discover novel strategies for improved plant growth as well as environmental responses to optimize plant resilience and productivity,” Lam said.

Although duckweed has adapted to an aquatic habitat, it has all the same types of genes and pathways as in well studied crop plants.

“As such, the novel strategies that we can learn from studying these small plants could potentially be used to re-engineer traditional crop plants to endow them with new traits,” Lam said. “Furthermore, as the commercialization of duckweed-based bioproducts gathers steam, we and our co-authors are optimistic that the basic research we are carrying out in the laboratory will help translate duckweed's prodigious productivity into new sustainable crops that can augment traditional agricultural products.”

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Broadcast interviews: Rutgers University has broadcast-quality TV and radio studios available for remote live or taped interviews with Rutgers experts. For more information, contact John Cramer at john.cramer@rutgers.edu

ABOUT RUTGERS—NEW BRUNSWICK
Rutgers University–New Brunswick is where Rutgers, the State University of New Jersey, began more than 250 years ago. Ranked among the world’s top 60 universities, Rutgers’s flagship is a leading public research institution and a member of the prestigious Association of American Universities. It has an internationally acclaimed faculty, 12 degree-granting schools and the Big Ten Conference’s most diverse student body.

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JOURNAL

The Plant Cell

DOI

10.1093/plcell/koab189

SUBJECT OF RESEARCH

Cells

ARTICLE TITLE

Return of the Lemnaceae: duckweed as a model plant system in the genomics and postgenomics era

ARTICLE PUBLICATION DATE

17-Jul-2021

 

Study of structural variants in cacao genomes yields clues about plant diversity

Peer-Reviewed Publication

PENN STATE

 

IMAGE: IN THIS STUDY, THE RESEARCHERS ANALYZED AND COMPARED CHROMOSOME-SCALE GENOME ASSEMBLIES OF 31 NATURALLY OCCURRING POPULATIONS OF THEOBROMA CACAO, THE LONG-LIVED TREE SPECIES THAT IS THE SOURCE OF CHOCOLATE. THIS MAP SHOWS THEIR ORIGINS IN THE AMAZON BASIN IN SOUTH AMERICA. view more 

CREDIT: PENN STATE

Molecular geneticists have known for about a decade that genomic structural variants can play important roles in the adaptation and speciation of both plants and animals, but their overall influence on the fitness of plant populations is poorly understood. That’s partly because accurate population-level identification of structural variants requires analysis of multiple high-quality genome assemblies, which are not widely available.

In this study, the researchers investigated the fitness consequences of genomic structural variants in natural populations by analyzing and comparing chromosome-scale genome assemblies of 31 naturally occurring populations of Theobroma cacao, the long-lived tree species that is the source of chocolate. Among those 31 strains of cacao, they found more than 160,000 structural variants.

In findings published today (Aug. 16) in the Proceedings of the National Academy of Sciences, the researchers reported that most structural variants are deleterious and thus constrain adaptation of the cacao plant. These detrimental effects likely arise as a direct result of impaired gene function and as an indirect result of suppressed gene recombination over long periods of time, they noted.

However, despite the overall detrimental effects, the study also identified individual structural variants bearing signatures of local adaptation, several of which are associated with genes differentially expressed between populations. Genes involved in pathogen resistance are among these candidates, highlighting the contribution of structural variants to this important local adaptation trait.

CAPTION

The genomes of different populations of cacao trees like these are 99.9% identical, but it’s the structural variants in that one tenth of 1% of their genomes that accounts for the plant’s diversity in different regions and its adaptation to climate and various diseases.

CREDIT

Robert Wilson

An exhaustive and painstaking comparison of the genomes of multiple strains of the cacao tree by a team of researchers has provided insights into the role genomic structural variants play in the regulation of gene expression and chromosome evolution, giving rise to the differences within populations of the plant.

The research, which has implications for plant genetics in general, would not have been possible before powerful computers made the high-resolution sequencing of genomes possible, affordable and relatively fast, according to team member Mark Guiltinan, J. Franklin Styer Professor of Horticultural Botany and professor of plant molecular biology in Penn State’s College of Agricultural Sciences.

“The genomes of different populations of cacao trees are 99.9% identical, but it’s the structural variants in that one-tenth of 1% of their genomes that accounts for the plant’s diversity in different regions and its adaptation to climate and various diseases,” he said. “This study makes an association between structural variation and the ability of a plant to adapt to a local environment.”

Overall, their findings provide important insight into processes underlying the fitness effects of structural variants in natural populations, the researchers pointed out. They suggest that structural variants influence gene expression, which likely impairs gene function and contributes to their detrimental effects. They also provided empirical support for a theoretical prediction that structural variants result in the suppression of gene recombination, making it less likely the plants can adapt to stressors.

CAPTION

Genomic structural variants are associated with genes differentially expressed between populations, such as genes involved in resistance to pathogens like the one that causes black pod rot, shown here.

CREDIT

Andrew Fister/Penn State

Beyond revealing new empirical evidence for the evolutionary importance of structural variants in all plants, documenting the genomic differences and structural variants among the 31 strains of cacao provides a valuable resource for ongoing genetic and breeding studies for that valuable plant, Guiltinan noted.

“All cacao comes from the Amazon basin — plants were collected a long time ago from the wild by collectors and they were cloned, so we have a permanent collection,” he said. “Their genomes have been sequenced, and that represents a huge amount of work and data. As a result of this study, we know that structural variation is important to the survival of the plant, to the evolution of the plant and especially to the adaptation of the plant to local conditions.”

Also involved in the research at Penn State were Claude dePamphilis, director of the Center for Parasitic and Carnivorous Plants, Dorothy Foehr Huck and J. Lloyd Huck Distinguished Chair in Plant Biology and Evolutionary Genomics, and professor of biology; Eric Wafula, bioinformatics programmer, Eberly College of Science; and Paula Ralph, senior research technologist, Eberly College of Science. Other team members were Tuomas Hamala and Peter Tiffin, Department of Plant and Microbial Biology, University of Minnesota.

The National Science Foundation and the U.S. Department of Agriculture’s National Institute of Food and Agriculture supported this work.

 

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JOURNAL

Proceedings of the National Academy of Sciences

ARTICLE TITLE

Genomic structural variants constrain and facilitate adaptation in natural populations of , the chocolate tree

ARTICLE PUBLICATION DATE

16-Aug-2021

Disclaimer: AAAS and EurekAl

 

History of the spread of pepper

(C. annuum) is an early example of 

global trade

Peer-Reviewed Publication

LEIBNIZ INSTITUTE OF PLANT GENETICS AND CROP PLANT RESEARCH

 

IMAGE: THE RESEARCHERS CONDUCTED A HUGE GENOMIC SCAN OF OVER TEN THOUSAND PEPPER (CAPSICUM SPP.) SAMPLES FROM WORLDWIDE GENEBANKS AND USED THE DATA TO INVESTIGATE THE HISTORY OF THIS ICONIC STAPLE. view more 

CREDIT: ILAN PARAN

Genebanks collect vast collections of plants and detailed passport information, with the aim of preserving genetic diversity for conservation and breeding. Genetic characterisation of such collections has also the potential to elucidate the genetic histories of important crops, use marker-trait associations to identify loci controlling traits of interest, search for loci undergoing selection, and contribute to genebank management by identifying taxonomic misassignments and duplicates.

“We conducted a huge genomic scan of over ten thousand pepper (Capsicum spp.) samples from worldwide genebanks and used the data to investigate the history of this iconic staple”, says Dr. Pasquale Tripodi, researcher at the Italian research institute CREA and co-first author of the study.

The peppers originated from 130 countries across five continents, a feat made possible through collaboration among many genebanks. This allowed the researchers to assess aspects of genebank management such as sample duplication. Genomic data detected up to 1,618 duplicate accessions within and between genebanks. “This significant level of duplication should motivate the development of genetic pre-screening protocols to be used in genebanks for documenting the potential duplicate samples upon first acquisition”, says Prof. Dr. Nils Stein, head of the research group Genomics of Genetic Resources at IPK Leibniz Institute, holder of a joint professorship at the University of Göttingen and coordinator of this pepper study which was part of the larger effort of the EU H2020 funded project G2P-SOL.

At its heart, the project represents a case study in the exploitation and in-depth analysis of genetic data from genebank collections to yield more and better information on expansion routes of the most economically important pepper species (Capsicum annuum); a species that has changed the face of culinary cultures worldwide. A method named ReMIXTURE - which uses genetic data to quantify the similarity between the complement of peppers from a focal region to those from other regions - was invented for the study and used to supplement more traditional population genetic analyses.

“The results reflect a vision of pepper as a highly desirable and tradable cultural commodity, spreading rapidly throughout the globe along major maritime and terrestrial trade routes”, says Dr. Mark Timothy Rabanus-Wallace from IPK Leibniz Institute, who co-led the study and who developed the ReMIXTURE method. “A large factor in pepper’s initial appeal was certainly its pungency, especially in nontropical Europe where hot spices were rare and imported black pepper could fetch good prices.” 

The kinds of peppers collected in broad regions across the globe overlap considerably. In particular, peppers in Eurasian regions overlap with neighbouring regions, a result of overland trade routes like the silk road. European and African peppers overlap a lot with peppers from the Americas, probably a result of transatlantic trade during the Age of Discovery. South/Mesoamerica, Eastern Europe, and Africa are all notable for large proportions of region-unique peppers. 

The group also detected that regions of the genome affecting traits such as pungency were distributed non-uniformly across the globe, suggesting that human culture truly does exert a primary influence over how peppers spread throughout the globe. IPK scientist Dr. Mark Timothy Rabanus-Wallace hopes the study encourages broader enjoyment globally of these regions’ unique and beautiful peppers.

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JOURNAL

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2104315118

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Global range expansion history of pepper (Capsicum spp.) revealed by over 10,000 genebank accessions.

ARTICLE PUBLICATION DATE

15-Aug-2021

Disclaimer: AAAS and EurekA

 

Recordings of the magnetic field from 9,000 years ago teach us about the magnetic field today

Tel Aviv University Research Links Archaeology, Physics, and Geophysics

Peer-Reviewed Publication

TEL-AVIV UNIVERSITY

 

IMAGE: EXCAVATIONS -TEL TIFDAN/ WADI FIDAN. view more 

CREDIT: THOMAS E. LEVY

International research by Tel Aviv University, the Istituto Nazionale di Geofisica e Vulcanologia, Rome, and the University of California San Diego uncovered findings regarding the magnetic field that prevailed in the Middle East between approximately 10,000 and 8,000 years ago. Researchers examined pottery and burnt flints from archaeological sites in Jordan, on which the magnetic field during that time period was recorded. Information about the magnetic field during prehistoric times can affect our understanding of the magnetic field today, which has been showing a weakening trend that has been cause for concern among climate and environmental researchers.

 

The research was conducted under the leadership of Prof. Erez Ben-Yosef of the Jacob M. Alkow Department of Archaeology and Ancient Near Eastern Cultures at Tel Aviv University and Prof. Lisa Tauxe, head of the Paleomagnetic Laboratory at the Scripps Institution of Oceanography, in collaboration with other researchers from the University of California at San Diego, Rome and Jordan. The article was published in the journal PNAS.

 

Prof. Ben-Yosef explains, "Albert Einstein characterized the planet's magnetic field as one of the five greatest mysteries of modern physics. As of now, we know a number of basic facts about it: The magnetic field is generated by processes that take place below a depth of approximately 3,000 km beneath the surface of the planet (for the sake of comparison, the deepest human drilling has reached a depth of only 20 km); it protects the planet from the continued bombardment by cosmic radiation and thus allows life as we know it to exist; it is volatile and its strength and direction are constantly shifting, and it is connected to various phenomena in the atmosphere and the planet's ecological system, including – possibly – having a certain impact on climate. Nevertheless, the magnetic field's essence and origins have remained largely unresolved. In our research, we sought to open a peephole into this great riddle."

  

CAPTION

Wadi Fidan

CREDIT

Thomas E. Levy

The researchers explain that instruments for measuring the strength of the Earth's magnetic field were first invented only approximately 200 years ago. In order to examine the history of the field during earlier periods, science is helped by archaeological and geological materials that recorded the properties of the field when they were heated to high temperatures. The magnetic information remains "frozen" (forever or until another heating event) within tiny crystals of ferromagnetic minerals, from which it can be extracted using a series of experiments in the magnetics laboratory. Basalt from volcanic eruptions or ceramics fired in a kiln are frequent materials used for these types of experiments. The great advantage in using archaeological materials as opposed to geological is the time resolution: While in geology dating is on the scale of thousands years at best, in archaeology the artifacts and the magnetic field that they have recorded can be dated at a resolution of hundreds and sometimes even tens of years (and in specific cases, such as a known destruction event, even give an exact date). The obvious disadvantage of archaeology is the young age of the relevant artifacts: Ceramics, which have been used for this purpose up until now, were only invented 8,500 years ago.

  

CAPTION

. Burnt flints and ceramics used to reconstruct the strength of the ancient geomagnetic field (from the article)

CREDIT

(from the article)

The current study is based on materials from four archaeological sites in Wadi Feinan (Jordan), which have been dated (using carbon-14) to the Neolithic period – approximately 10,000 to 8,000 years ago - some of which predate the invention of ceramics. Researchers examined the magnetic field that was recorded in 129 items found in these excavations, and this time, burnt flint tools were added to the ceramic shards.  Prof. Ben-Yosef: "This is the first time that burnt flints from prehistoric sites are being used to reconstruct the magnetic field from their time period. About a year ago, groundbreaking research at the Hebrew University was published, showing the feasibility of working with such materials, and we took that one step forward, extracting geomagnetic information from tightly dated burned flint. Working with this material extends the research possibilities tens of thousands of years back, as humans used flint tools for a very long period of time prior to the invention of ceramics. Additionally, after enough information is collected about the changes in the geomagnetic field over the course of time, we will be able to use it in order to date archaeological remains".

  

CAPTION

Prof. Erez Ben-Yosef

CREDIT

Yoram Reshef

An additional and important finding of this study is the strength of the magnetic field during the time period that was examined. The archaeological artifacts demonstrated that at a certain stage during the Neolithic period, the field became very weak (among the weakest values ever recorded for the last 10,000 years), but recovered and strengthened within a relatively short amount of time. According to Prof. Tauxe, this finding is significant for us today: "In our time, since measurements began less than 200 years ago, we have seen a continuous decrease in the field's strength. This fact gives rise to a concern that we could completely lose the magnetic field that protects us against cosmic radiation and therefore, is essential to the existence of life on Earth. The findings of our study can be reassuring: This has already happened in the past. Approximately 7,600 years ago, the strength of the magnetic field was even lower than today, but within approximately 600 years, it gained strength and again rose to high levels."

The research was carried out with the support of the US-Israel Binational Science Foundation, which encourages academic collaborations between universities in Israel and in the US. The researchers note that in this case, the collaboration was particularly essential to the success of the study because it is based on a tight integration of methods from the fields of archaeology and geophysics, and the insights that were obtained are notably relevant to both of these disciplines.

 

Link to the article:

https://doi.org/10.1073/pnas.2100995118

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DOI

https://doi.org/10.1073/pnas.2100995118

ARTICLE PUBLICATION DATE

15-Aug-2021

 

Fire in wet area of the Amazon destroys 27% of trees in up to three years, study finds

Based on data collected in the field, researchers showed that small and medium trees suffer most in the first two years after a fire, but the overall impact on vegetation can last decades. Carbon stocks fall 12.8% in burned areas on average

Peer-Reviewed Publication

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO

 

IMAGE: CARBON STOCKS FALL 12.8% IN BURNED AREAS ON AVERAGE view more 

CREDIT: INPE

Even in the wettest parts of the Amazon, the impact of forest fires, which spread through these areas only during extreme droughts, is sufficient to change the characteristics of the vegetation in the coming decades, although it is not as significant as in other parts of the biome.

According to an innovative study that measured the effects of fire in situ, burned forest in a wet area loses 27.3% of its stem density on average. The destruction affects mainly trees of small and medium size. Loss of biomass (stored carbon) in the three years following a fire reaches 12.8%. Mortality is worst in the first two years, and makes way for the growth of native herbaceous bamboo species.

The Amazon region corresponds to 59% of Brazil, with an area of 5 million sq. km., 775 municipalities, 67% of the planet’s tropical forest, a third of its trees, and 20% of its freshwater.

It is also the Brazilian biome with the most fires every year since records began, according to the National Space Research Institute (INPE). In 2020, INPE recorded 103,161 fires, the largest number since 2017 (107,439) and the third-largest in the decade. The second-largest number occurred in 2015 (106,438). INPE’s forest fire statistics are summarized at: https://queimadas.dgi.inpe.br/queimadas/portal-static/estatisticas_estados/.

The 2015 fires, exacerbated by the extreme drought relating to El Niño, were the focus for a study supported by São Paulo Research Foundation - FAPESP via two projects (16/21043-8 and 20/06734-0). An article describing the results, including data collected directly in the field, is published in Proceedings of the Royal Society B: Biological Sciences.

The study was led by Luiz Eduardo Oliveira e Cruz de Aragão, who heads INPE’s Earth Observation and Geoinformatics Division (DIOTG).

“Studying how forests respond to fire in the long run is one of the frontiers of knowledge about the functioning of the Amazon. It’s important both to enhance our capacity to model the biome’s future and climate interactions, and to provide data for Brazil to report emissions and carbon removal more accurately in the context of policies to reduce emissions from deforestation and forest degradation [REDD+], which can yield financial benefits for the country,” Aragão told.

The researchers analyzed burned and unburned areas immediately after the fires that swept through the north of the area between the Purus and Madeira Rivers (central Amazon), and conducted annual surveys to track the demographic drivers of biomass change in the ensuing three years.

The area is located in the municipality of Autazes, some 90 km southeast of Manaus, near the BR-319 highway. The researchers measured trees with a diameter of 10 cm or more, and estimated the extent to which stem growth and tree mortality were influenced by fire intensity (represented by bole char height, an indicator of the length of time a tree bole has been exposed to the flames and high temperatures of a fire), and tree morphology (size and wood density).

Most of the field work was done by Aline Pontes-Lopes, a PhD candidate at INPE, and Camila Silva, a researcher at the Amazon Institute of Environmental Research (IPAM), respectively first and second authors of the article.

“The field data is very valuable. The study included multiple censuses of the same burned area, a type of information that’s rare for the Amazon. In particular, field data is rare for tree mortality, growth and local dynamics in rainforest areas generally. The study also analyzed the effects of fire on the wettest parts of the forest, where it’s unusual. A great deal of new knowledge about such areas was produced,” said Ricardo Dal’Agnol, a researcher at INPE and another co-author of the article.

Dal’Agnol, who is supported by FAPESP via a postdoctoral scholarship, participated in another study published in January showing that water stress, soil fertility and anthropic forest degradation create gaps in the Amazon Rainforest, and influence tree mortality more than any other factors (more at: agencia.fapesp.br/35620).

Results

“In the burned areas we saw that saplings, small trees and bushes are the first to die, clearing the understory enough for us to walk through the forest and set up the forest inventory plots in 2015. Small and medium trees above all died in two to three years,” Pontes-Lopes said in an interview given to Agência FAPESP. The understory is the layer of trees and shrubs beneath the forest canopy but above the forest floor.

Another important point, she added, is the impact of fire on biomass. According to the study, biomass remained stable throughout the three-year period in the unburned plots but decreased 12.8% in the burned areas.

The impact was especially severe on lianas, which lost 38.6% of their individuals and 38.1% of their biomass. Tree loss was 28% for individual trees and 12.1% for biomass; for palms, the loss was 14.6% for individuals and 27.2% for biomass. The same comparisons for unburned plots showed much smaller losses or no significant change.

The scientists’ growth measurements and comparisons of burned with unburned areas showed that trees with lower wood density grew faster in burned areas in a three-year timeframe, and that large trees stored more carbon in burned areas. However, faster growth by these two tree classes did not cause an increase in the forest’s total biomass or in wood production, both of which were outpaced by tree mortality due to fire.

According to Pontes-Lopes, other groups are using the data collected in at least four studies. The data has been standardized and posted to ForestPlots.net, a website for researchers, forest scientists and forest communities to share data that will help measure, monitor and understand the world’s forests, especially in the tropics.

Future

According to the researchers, continuous monitoring of areas affected by fire at regular intervals (annual or semiannual) is important to improve our understanding of carbon emissions and uptake, the time forest takes to recover to a pre-fire state, and disruption of carbon dynamics by tree mortality due to additional drought and fire events. Future studies should focus on long-term post-fire monitoring to find out whether delayed mortality of large trees occurs on a significant scale in the Amazon, they conclude.

Fire in the Amazon is estimated to cause more than 50% of global greenhouse gas emissions due to land use change. These gases, especially carbon dioxide (CO2), contribute to the average temperature rise, which could reach 1.5 °C above pre-industrial levels by 2050 if effective measures are not taken soon to mitigate global warming.

The long-term impact of fires in the Amazon is insufficiently quantified, however. An article published last year with Silva as first author showed that more than 70% of the gross emissions resulting from forest fires in a 30-year period were due to tree mortality and decomposition (as distinct from combustion). These emissions were only partially offset by forest growth in the same period. The study also found that net annual emissions peaked four years after forest fires.

Deforestation and forest degradation, in conjunction with climate change, compromise forest carbon stocks. Plant photosynthesis converts light and CO2 into energy, reducing the amount of CO2 in the atmosphere. The carbon remains in the biomass until the vegetation burns, or dies and decomposes.

“Without proper land use regulation, the current intention of Brazil's government to pave the BR-319 will increase deforestation in the Purus-Madeira region, increasing ignition sources and the associated risk of large-scale forest dieback,” the authors warn.

They recommend two initiatives in support of future decision making to avoid large-scale forest fire in the Amazon: mapping of forest fire risks, and mapping of potential fire impacts based on morphological plant traits. Remote sensing technologies are essential to complement field inventories in developing these initiatives.

“If the effects of fire on the forest are better understood, management of the biome can improve thanks to better fire management policy, which should be decoupled from deforestation reduction policy,” Aragão said. “Progress in this matter is crucial to quantify the real impact of human activity on the carbon cycle in the Amazon and find coherent ways of achieving sustainable development for the nation.”

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About São Paulo Research Foundation (FAPESP)

The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at http://www.fapesp.br/en and visit FAPESP news agency at http://www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.

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JOURNAL

Proceedings of the Royal Society B Biological Sciences

DOI

10.1098/rspb.2021.0094#d1e581

ARTICLE TITLE

Drought-driven wildfire impacts on structure and dynamics in a wet Central Amazonian forest

ARTICLE PUBLICATION DATE

18-May-2021