The Cerrado originally spanned approximately two million square kilometers, with about 98 percent of that area inside Brazil and small portions extending into Bolivia and Paraguay. Recognized as a global biodiversity hotspot, it harbors thousands of endemic species and underpins the health of the country’s major river basins. Yet more than 55 percent of its native vegetation has already been destroyed, an area exceeding one million square kilometers converted into pastures, monocultures, and cities, with the pace of conversion accelerating sharply from the 1980s onward.

Satellite monitoring data cited in the review show that between 1985 and 2023 the Cerrado lost roughly 380,000 square kilometers of native vegetation, equivalent to 19 percent of its original coverage. Since systematic monitoring began in 2001, more than 326,000 square kilometers have been cleared, an area nearly the size of Italy. Annual clearing rates peaked at nearly 29,000 square kilometers in 2003 and 2004, fell through the following decade, and then climbed again from 2019, reaching a recent peak of about 11,012 square kilometers in 2023 before declining to 7,235 square kilometers in 2025.

One of the review’s central arguments is that the Cerrado cannot be treated as a single, uniform savanna. The authors propose calling it an “ecodomain,” a term meant to capture its true heterogeneity: grasslands such as Campo Limpo and Campo Rupestre, savanna formations including Cerrado Denso and Vereda, and forests such as Cerradão, Mata Ciliar, and Mata Seca. These ecosystems occur in dynamic, interdependent mosaics, each with distinct vulnerabilities. Rocky grassland ecosystems, for example, occupy only about 7 percent of the Cerrado but host extraordinary endemism and feed the springs that make the region Brazil’s “water tank,” yet they are prime targets for mining of iron, niobium, gold, and quartz.

Fire is another axis of the crisis. Many Cerrado species evolved under natural fire regimes, developing thick bark, underground storage organs, and deep roots that allow them to resprout after burning. But the review stresses that roughly 99 percent of fires in Brazil are now of human origin, occurring with increasing frequency and intensity outside natural seasonality. Between 1985 and 2022, fire affected 40 percent of the Cerrado, and 63 percent of that burned area burned more than once. In 2024 the region recorded around 14.6 million hectares of burned land, the highest figure since 2012, a level the authors describe as a collapse of the ecological fire regime.

The hydrological stakes are equally severe. The Cerrado is the cradle of eight of Brazil’s twelve major river basins and sits atop three immense aquifers: Bambuí, Urucuia, and Guarani. Deep-rooted vegetation channels rainfall into the ground and sustains dry-season river flows. Irrigation for soybeans and other commodities, hydropower dams on once free-flowing rivers, and agrochemical runoff are depleting and contaminating these reserves, a fragility exposed during Brazil’s worst drought in nearly a century in 2021.

The biodiversity accounting is sobering. The region hosts more than 3,200 vertebrate species, around 13,000 angiosperm plants, and an estimated invertebrate fauna that may exceed 90,000 species. The authors estimate roughly 600 angiosperms and between 400 and 450 invertebrates are formally threatened, more than all threatened terrestrial vertebrates combined. Among 340 known endemic terrestrial vertebrates, only 57 have been officially assessed as globally threatened, and more than 20 percent remain unassessed or data deficient, meaning many species may vanish before science even records them.

Legal protections are a particular focus of criticism. The Forest Code requires landowners to preserve only 20 percent of native vegetation as a legal reserve in most of the Cerrado, versus 35 percent in the Legal Amazon, an asymmetry the authors call unjustified. Permanent protection strips along watercourses are set at 30 meters for rivers up to 10 meters wide, far narrower than the natural width of gallery forests, undermining their ecological function. Only about 8 percent of the Cerrado is effectively protected, and less than 3 percent in strictly protected areas, far short of the Kunming-Montreal Global Biodiversity Framework’s 30 percent target for 2030.

The review also highlights the role of Indigenous peoples, around 100,000 people from at least 83 ethnic groups living across roughly 109 recognized territories covering about 4.4 percent of the original Cerrado. The authors firmly reject narratives blaming Indigenous communities for degradation, describing them instead as guardians whose controlled burning practices and traditional knowledge support conservation. They warn that the 2023 “Marco Temporal” law, which conditions land rights on occupation as of 1988, and agribusiness proposals to legalize farming on Indigenous lands threaten to accelerate biodiversity loss.

The proposed way forward combines expanding conservation units and Indigenous lands, restoring degraded pastures and abandoned croplands using techniques such as biomass transposition, and shifting from extractive to regenerative economies built on premium native products, payments for ecosystem services, and carbon credits that recognize the Cerrado’s largely underground carbon stocks, which average about 158 tons per hectare with 87 percent stored belowground. The authors frame defending the Cerrado not merely as an ecological imperative but as an agenda for environmental justice, water security, and intergenerational responsibility, urging that the region be repositioned at the center of global discussions on conservation, climate, and sustainable development.

Subject of Research: Threats to and conservation pathways for the Cerrado biodiversity hotspot in Brazil

Article Title: The Cerrado crisis review: highlighting threats and providing future pathways to save Brazil's biodiversity hotspot

Article References: Pereira, C. C., Kenedy-Siqueira, W., Maia, L. R., Sperandei, V. D. F., Arantes-Garcia, L., Fernandes, S., Fernandes, G. F. C., de Castro, G. C., Rodrigues, D. D. J., Salm, R., & Fearnside, P. M. (2026). The Cerrado crisis review: highlighting threats and providing future pathways to save Brazil's biodiversity hotspot. Nature Conservation, 61, 29-70. https://doi.org/10.3897/natureconservation.61.168273

Image Credits: AI Generated

DOI: 10.3897/natureconservation.61.168273

Keywords: Cerrado, biodiversity hotspot, deforestation, Brazil, fire regime, water security, conservation units, Forest Code, Indigenous lands, ecological restoration, carbon sink, savanna

The work, led by Xu-Ri and Jiaoneng Yu of the Institute of Tibetan Plateau Research at the Chinese Academy of Sciences, together with colleagues across China and the United States, tackles a long-standing blind spot in high-altitude carbon accounting. Nitrogen is the nutrient that most often limits plant growth in cold environments, and the amount of carbon an ecosystem can lock away is tightly coupled to how much nitrogen enters the system. In most models of the Tibetan Plateau, that nitrogen input has been treated as a fixed background quantity. The new study shows it is anything but fixed: it depends on which plants are present, how much biomass they hold, and where on the mountain they grow.

To quantify this, the team assembled one of the largest sampling campaigns ever attempted across the plateau’s alpine permafrost region. They collected 1,047 plant samples from 323 plots spanning the plateau’s environmental gradients, then applied nitrogen-15 natural-abundance techniques — a method that exploits the tiny differences in the ratio of nitrogen-15 to nitrogen-14 that arise when plants draw nitrogen from the atmosphere versus from the soil — to work out how much of each plant’s nitrogen came from biological fixation and how much came from the soil pool. Because only legumes host the rhizobial bacteria capable of fixing atmospheric nitrogen into reactive forms, the isotope signatures allowed the researchers to separate the two sources with unusual precision for a landscape this large.

The results reveal a strikingly clean relationship. Aboveground symbiotic nitrogen fixation across the region ranged from essentially zero to 7.43 grams of nitrogen per square metre per year, and it tracked legume aboveground biomass almost perfectly. Where legumes were abundant, fixation was high; where they were sparse, it all but vanished. The pattern held across the plateau’s elevation gradient, with fixation peaking at elevations between 3,600 and 4,000 metres — the band where alpine meadows are most productive and legumes most prevalent. Below that band, harsher conditions suppress legume growth; above it, shorter growing seasons and colder soils do the same.

What makes the finding consequential is what happens when the fixation map is laid over the map of recent ecological change. The spatial distribution of symbiotic nitrogen fixation largely coincides with the areas that have gained the most aboveground biomass and plant nitrogen density over recent decades. In other words, the parts of the plateau that are greening and accumulating plant material fastest are precisely the parts where legumes are pumping new nitrogen into the system. The implication is that the region’s carbon gains are not simply a passive response to warming and longer growing seasons — they are actively underwritten by the nitrogen-fixing capacity of the plant community itself.

To test how much this matters, the team turned to process-based ecosystem simulations, running scenarios in which symbiotic nitrogen fixation was removed from the model. The outcome was stark: without the nitrogen supplied by legumes, the ecosystems slid into severe nitrogen limitation, and the region’s carbon balance flipped from a net sink — taking up more carbon than it releases — to a net source, emitting more carbon to the atmosphere than it stores. The simulation does not predict that legumes will disappear, but it isolates their contribution and shows that the carbon sink the plateau currently provides is contingent on a biological process that most carbon-cycle models do not represent at all.

The stakes are high because the Tibetan Plateau’s permafrost region holds enormous stores of organic carbon accumulated over millennia in frozen soils. As warming accelerates permafrost thaw, the question of whether these ecosystems will continue to sequester carbon in their vegetation — offsetting some of the carbon released from thawing ground — is central to global climate projections. The new results suggest that the answer depends partly on legumes: if warming shifts vegetation composition in ways that reduce legume abundance, the nitrogen supply that supports plant growth could falter, weakening the carbon sink precisely when it is most needed. Conversely, if legumes expand or maintain their dominance, they could help sustain the sink even as conditions change.

The study also carries a methodological lesson for the wider field. Nitrogen-15 natural-abundance techniques have long been used at individual sites, but applying them across 323 plots spanning an entire permafrost region is rare, and it allowed the researchers to move from plot-level estimates to a regional picture of nitrogen inputs. That regional picture, in turn, is what makes the link to decadal biomass gains visible — a connection that would be invisible in single-site studies. The approach could be replicated in other cold regions, from the Arctic tundra to the Alps, where the role of nitrogen-fixing plants in the carbon cycle remains poorly quantified.

For climate modellers, the message is that symbiotic nitrogen fixation is not a detail to be averaged away. It is a first-order control on whether high-altitude permafrost ecosystems act as carbon sinks or sources, and its dependence on legume biomass means it can shift rapidly as vegetation communities reorganise under warming. Models that treat nitrogen inputs as static risk missing both the magnitude and the direction of future carbon fluxes in these regions. Incorporating legume dynamics — their distribution, their biomass, and their sensitivity to warming — into process-based carbon-cycle frameworks is now a concrete priority.

For the plateau itself, the findings add a layer of urgency to conservation. The legumes that anchor this nitrogen economy are embedded in alpine meadows that face grazing pressure, infrastructure development and rapid climatic change. Protecting the plant communities that sustain nitrogen fixation may prove to be one of the most cost-effective ways to preserve the region’s carbon storage capacity. As the permafrost warms and the plateau’s ecosystems are pushed into new configurations, the humble legume — often overlooked in favour of charismatic megafauna or sweeping glacier imagery — may turn out to be one of the most important biological levers in the region’s climate future.

Subject of Research: Symbiotic nitrogen fixation by legumes and its role in sustaining carbon sinks in the warming Tibetan Plateau permafrost region

Article Title: Symbiotic nitrogen fixation sustains carbon sinks under warming Tibetan permafrost region

Article References: Xu-Ri, Yu, J., Qu, S., Tian-Liang, Shama, R., Lei, H., Cui, Y., Xu, X., Pan, Y., Niu, H., Borjigidai, A., Liang, E., & Chen, F. (2026). Symbiotic nitrogen fixation sustains carbon sinks under warming Tibetan permafrost region. Communications Earth & Environment. https://doi.org/10.1038/s43247-026-04085-8

Image Credits: AI Generated

DOI: 10.1038/s43247-026-04085-8

Keywords: Tibetan Plateau, permafrost, symbiotic nitrogen fixation, legumes, carbon sink, nitrogen cycle, nitrogen-15 isotope, alpine meadow, climate change, ecosystem modelling, carbon sequestration, plant ecology

The concept at the heart of the review is called the carbon sink by carbonate weathering coupled with aquatic photosynthesis, or CCW. When rainwater percolates through limestone and other carbonate rocks, it dissolves them, pulling atmospheric carbon dioxide into the water as dissolved inorganic carbon. In karst regions, this process produces dissolved inorganic carbon concentrations that are six to ten times higher than in non-karst watersheds. Aquatic plants, algae, and microorganisms then convert a portion of this dissolved inorganic carbon into autochthonous organic carbon through photosynthesis, a process the researchers term autochthonous production. That organic carbon, once buried in sediments or transported downstream to the ocean, becomes a long-term stable carbon sink rather than a transient one.

What makes the CCW theory particularly compelling as a nature-based solution is its dual benefit. The review details how elevated dissolved carbon dioxide acts as a fertilizer for aquatic photosynthesis, alleviating what the authors identify as a chronic carbon limitation in high-pH karst waters. In these alkaline environments, the carbonate equilibrium system is dominated by bicarbonate and carbonate ions, leaving free carbon dioxide at often less than one percent of the total dissolved inorganic carbon pool. This scarcity constrains photosynthetic organisms that preferentially use carbon dioxide over bicarbonate, which requires energy-intensive carbon concentrating mechanisms to assimilate.

The fertilization effect ripples through the entire aquatic food web in ways that suppress eutrophication rather than exacerbate it. When carbon dioxide is scarce, cyanobacteria—blue-green algae equipped with highly efficient carbon concentrating mechanisms—dominate because they can strip bicarbonate from the water when other organisms cannot. These blooms produce toxins, deplete oxygen, and degrade water quality. But when dissolved carbon dioxide is abundant, species with weaker carbon concentrating mechanisms, such as green algae and diatoms, gain a competitive edge. The review cites field data from Erhai Lake in Yunnan and Caohai Lake in Guizhou showing that cyanobacteria decline relative to other phytoplankton when the carbon-to-nitrogen and carbon-to-phosphorus molar ratios in the water exceed specific thresholds, suggesting that carbon fertilization can tip the ecological balance away from harmful bloom-forming species.

Submerged aquatic plants, the foundation of healthy shallow lake ecosystems, also benefit disproportionately from carbon fertilization. Unlike phytoplankton, these rooted plants have limited capacity to use bicarbonate and typically begin switching to it only when carbon dioxide concentrations exceed 50 micromoles per liter, far above the 10 to 15 micromole threshold for many algae. Their higher carbon-to-nitrogen and carbon-to-phosphorus stoichiometric ratios mean they are better adapted to carbon-rich environments. Dense beds of submerged plants improve water clarity, stabilize sediments, provide habitat for aquatic fauna, and release chemical compounds that inhibit algal growth, creating a self-reinforcing cycle of water quality improvement.

The review also illuminates a second, purely geochemical mechanism by which autochthonous production removes phosphorus, the nutrient most responsible for eutrophication. As aquatic organisms photosynthesize, they raise the pH of the water, shifting the carbonate equilibrium toward carbonate ions and triggering the precipitation of calcium carbonate. This newly formed calcite has an enormous specific surface area and abundant adsorption sites. Dissolved phosphate co-precipitates with the calcite crystals or adsorbs onto their surfaces, converting soluble reactive phosphorus into an insoluble form that settles into the sediment. The authors report that when pH rises above 9.5, more than 74 percent of phosphorus can co-precipitate with calcium carbonate, a self-purification mechanism they call the AOCP-CP removal hypothesis, linking the organic carbon pump to the carbonate pump.

Field evidence for this mechanism comes from multiple sources. In Sicilian reservoirs, managers successfully controlled cyanobacterial outbreaks by spreading lime powder to induce calcium carbonate precipitation and phosphorus removal. Enclosure experiments in nutrient-poor lakes showed that added phosphorus stimulated productivity and calcium carbonate precipitation, but much of the phosphorus was ultimately buried in sediment through co-precipitation, creating a negative feedback on eutrophication. X-ray diffraction analyses of calcium carbonate products exposed to phosphate solutions revealed the formation of hydroxyapatite, the most thermodynamically stable calcium phosphate mineral, confirming the long-term sequestration of phosphorus in these systems.

The scale of the potential carbon sink is substantial. The review estimates that enhanced autochthonous production in inland waters could sequester between 0.38 and 1.8 billion tons of carbon per year, a range that positions these aquatic ecosystems as significant contributors to closing the global carbon budget. Data from the Shawan Karst Test Site in Guizhou Province showed that autochthonous organic carbon fixed in surface waters ranged from 156 to 493 tons of carbon per square kilometer per year, increasing with dissolved inorganic carbon concentration. In the Pearl River, a typical karst river, phytoplankton biomass and total organic carbon both rose with dissolved inorganic carbon, and autochthonous organic carbon accounted for 65 percent of the total organic carbon pool.

The authors acknowledge that significant research gaps remain. Most existing studies have focused on single regions and short time periods, lacking the global coverage and high-frequency monitoring needed to fully quantify carbon fluxes. The role of methane and nitrous oxide emissions from these waters in offsetting carbon gains remains poorly constrained. The mechanisms linking carbon fertilization to community structure shifts and phosphorus removal need further elucidation across different climatic zones, land uses, and lithologies. To address these gaps, the review proposes establishing a global monitoring network for carbon fluxes in karst surface waters, employing hydrological modeling, radioisotopes, stable carbon isotopes, and machine learning to trace carbon sources and quantify lateral transport and vertical burial.

Looking forward, the authors propose coupling enhanced carbonate rock weathering with aquatic photosynthesis as a next-generation carbon removal strategy. By deliberately managing aquatic productivity to convert dissolved inorganic carbon from enhanced weathering into stable organic carbon, the approach could approach near-complete carbon sequestration efficiency. As climate targets slip further out of reach and eutrophication intensifies across the globe, the humble chemistry of limestone and sunlight may prove to be one of the most elegant and scalable nature-based solutions available.

Subject of Research: Carbon fertilization of aquatic photosynthesis in karst surface waters as a nature-based solution for carbon sequestration and eutrophication mitigation

Article Title: Carbon fertilization of autochthonous production in karst surface waters and its role in carbon reduction and eutrophication mitigation—a nature-based solution (NbS)

Article References: Shao, M., Liu, Z., Zeng, S., Sun, H., & He, H. (2025). Carbon fertilization of autochthonous production in karst surface waters and its role in carbon reduction and eutrophication mitigation—a nature-based solution (NbS). Frontiers in Geochemistry, 3, Article 1622714. https://doi.org/10.3389/fgeoc.2025.1622714

Image Credits: AI Generated

DOI: 10.3389/fgeoc.2025.1622714

Keywords: karst, carbon cycle, eutrophication, nature-based solutions, carbonate weathering, aquatic photosynthesis, carbon sink, water quality, Carbon, fertilization, autochthonous, production

The study area lies in the municipality of Rianxo, where the temperate-oceanic climate delivered an average temperature of 15.7 degrees Celsius and an accumulated precipitation of 1,774 liters per square meter in 2024. The parent material is mainly granitic, and the soils are mostly classified as Leptosols and Umbrisols. These forests are communal properties, owned collectively by villagers, and the sampling was carried out in collaboration with forest owner associations across five forest communities, from Campelo Vilar e Cerqueiras to Leiro, at altitudes ranging from 50 to 485 meters above sea level. In each of the 54 stands, the team collected 10 subsamples along a zig-zag transect, compositing them into a single sample per plot from the 0 to 20 centimeter soil layer in the summer of 2024.

Galician forest soils are, in general, acidic, rich in organic matter and poor in phosphorus. The measurements confirmed this regional signature: pH values ranged between 4.63 and 5.6, soil organic matter between 12.1 and 20.9 percent, nitrogen between 0.41 and 0.69 percent, and extractable phosphorus between just 4.0 and 8.4 milligrams per kilogram. The researchers attribute these properties primarily to the humid climate, which drives intense leaching and acidification, and to the acidic nature of the granitic parent material, rather than to the tree species themselves. Statistically, no significant differences emerged in these solid-phase chemical properties among the different forest covers, a finding the authors link partly to the young age of more than half of the plantations, most of which were less than six years old.

Where the tree species did matter was in soil water content. Soils under eucalyptus and birch plantations were the driest, averaging 13 and 14 percent respectively, while soils under shrublands held the most water at 27 percent on average, with statistically significant differences. The intermediate values fell between 19 percent under walnut and 25 percent under pine. The ability of eucalyptus to extract large amounts of soil water is well documented, although some authors argue that eucalyptus water depletion is more a myth tied to poor plantation management than an inherent trait of the trees. Birch, meanwhile, has been shown to deplete topsoil moisture compared with conifers such as spruce. Both the birch and eucalyptus stands in this study were established over shallow soils of roughly 50 centimeters that had been burnt by a wildfire in 2019, and the authors suggest that the fire disturbance, the soil management for tree establishment, or the low organic matter content, which reduces water retention, could all explain the dry conditions. Indeed, the team detected a significant positive correlation between soil water content and soil organic matter.

The most striking result concerns microbial respiration, the rate at which soil organisms release carbon dioxide as they decompose organic matter. Soils under walnut plantations showed the highest respiration rates, averaging 1,440 plus or minus 97 parts per million of carbon dioxide per gram, while soils under eucalyptus showed the lowest, at 537 plus or minus 211 parts per million per gram. When the values for all deciduous broadleaf species were pooled together, respiration under eucalyptus was significantly lower than under the deciduous forests, with the coniferous pine values falling in between. Soil respiration correlated positively with soil organic matter, total nitrogen and total carbon, and walnut soils happened to contain the highest organic matter content at 20.9 percent, while eucalyptus soils had the lowest at 12.1 percent.

The walnut result carries an intriguing biochemical twist. Walnut leaf litter is rich in phenolic compounds that can inhibit Gram-positive bacteria but leave fungi unaffected, and fungi are the main drivers of respiration in forest soils. This selective pressure could favor a fungal-dominated community and boost carbon dioxide efflux. The eucalyptus result, by contrast, may reflect a different mechanism: previous studies have described a decrease in fungal dominance within eucalyptus plantations, which could explain the suppressed respiration rates. The eucalyptus plots had all been burnt in 2019, whereas the walnut plots had no recent fire history, but meta-analyses suggest that total soil respiration generally recovers to pre-fire values within about five years, and around three years for temperate forests, making the fire explanation less conclusive.

For the pine plantations, which represented the largest group with 30 samples, the researchers compared respiration across stands of different ages but found no significant differences, although average values tended to decline with tree longevity, from 991 plus or minus 69 parts per million per gram in 2 to 4 year old stands to 774 plus or minus 162 parts per million per gram in stands aged 40 to 45 years. A similar age-related decline has been reported in other coniferous plantations. The team also measured the activity of beta-glucosidase, a key enzyme in the carbon cycle that completes the final step of cellulose hydrolysis by converting cellobiose to glucose, but detected no significant differences among the forest covers, with average values ranging from 60 plus or minus 5 micrograms of p-nitrophenol per gram per hour under walnut to 31 plus or minus 15 under shrublands. The authors suggest that the limited variability in edaphic properties and the young age of most stands may explain the lack of differentiation in this enzyme activity.

Aluminium emerged as another defining feature of these soils. Exchangeable aluminium concentrations averaged between 4.7 and 7.43 centimoles per kilogram, representing between 63 and 90 percent saturation of the exchange complex, with practically all samples exceeding 60 percent saturation, a threshold indicative of alic soils that can limit plant growth. The highest saturation values appeared under shrublands at 90 percent, pines at 86 percent and chestnut at 83 percent, although these differences were not statistically significant. Despite this potentially toxic aluminium load, timber production in Galicia remains high within the temperate-humid region, likely because soil organic matter complexes aluminium into less toxic forms, and anions such as sulfate and fluoride can also bind aluminium and reduce its toxicity. The soils under chestnut, shrubland and pine showed the lowest concentrations of exchangeable calcium and magnesium, possibly reflecting the high demand these species place on these base cations to cope with aluminium stress, and the team detected a strong correlation between exchangeable calcium and magnesium across their samples.

When all the physicochemical and biological properties were analyzed together using redundancy analysis, no structural differences between forest covers were detected. The permutation test revealed that stand age was the only significant factor affecting soil properties, while wildfire events were marginally significant. Community location, altitude, tree species, parental rock and soil depth had no significant effect. The first component of the analysis explained 21.1 percent of the variability and was related to soil respiration, higher in samples with greater organic matter content. The authors acknowledge that their initial hypothesis, that tree species would drive the biggest differences between native broadleaf species and intensive plantations, was not fulfilled, most likely because the different ages of the stands acted as a confounding factor, and because the analyses were restricted to the solid soil phase, which is less sensitive to change than the soil solution.

The implications reach far beyond Galicia. Forest soils are crucial carbon sinks, both above and below ground, yet the soil section is still sometimes excluded from carbon pool estimations despite the enormous amount of carbon stored in it. As climate change sharpens the urgency of maximizing the carbon that healthy forest soils can fix, the finding that which tree species are cultivated measurably alters soil microbial respiration should be considered when elaborating forestry exploitation plans. Soils under eucalyptus exhibited the lowest values for both moisture and microbial respiration, while broadleaf deciduous species generally supported higher microbial activity through greater litter inputs and root exudation. The authors call for further research integrating microbial community analysis with functional assessments, alongside evaluating long-term wildfire and management impacts, to guide forest management under specific edapho-climatic conditions in a warming world.

Subject of Research: Forest soil science

Article Title: Effect of Different Tree Plantations on the Chemical Properties and Microbial Activity in Galician Forests Soils

Article References: Barreiro, A., Míguez-González, A., Cela-Dablanca, R., Díaz-Raviña, M., Núñez-Delgado, A., Fernández-Sanjurjo, M. J., & Álvarez-Rodríguez, E. (2025). Effect of Different Tree Plantations on the Chemical Properties and Microbial Activity in Galician Forests Soils. Spanish Journal of Soil Science, 15, Article 14988. https://doi.org/10.3389/sjss.2025.14988

Image Credits: AI Generated

DOI: 10.3389/sjss.2025.14988

Keywords: forest soils, soil respiration, carbon sink, eucalyptus, soil microbiology, forestry management, Galicia, wildfire, Effect, Different, Tree, Plantations

The problem the researchers set out to solve is structural rather than technical. Under the Land Use, Land-Use Change and Forestry (LULUCF) sector of the greenhouse gas inventory, countries must report net carbon dioxide emissions and removals for the subcategory of forest land remaining forest land. Aboveground biomass is generally well covered, because national forest inventories repeatedly measure tree growth. But deadwood, litter, and soil organic carbon are rarely measured systematically at intervals that allow carbon stock change factors to be derived empirically. Without those factors, the reported national net sink is methodologically incomplete — a gap that matters more as Europe’s forest carbon sink shows signs of saturation and faces mounting pressure from heat, drought, and disturbances.

Process-based models offer a way forward that differs fundamentally from the empirical growth-curve approaches many inventories rely on. Instead of extrapolating from inventory data alone, Biome-BGCMuSo simulates the daily cycling of carbon, nitrogen, and water through vegetation, litter, and soil, representing photosynthesis, respiration, carbon allocation, senescence, mortality, and decomposition mechanistically. The MuSo extension replaces the single-layer soil of the original Biome-BGC with a ten-layer soil profile, and the model can capture acclimatization to temperature, drought legacy effects on carbohydrate stores, and stomatal conductance that responds to atmospheric CO2. In this study the model was driven by the ERA5-Land meteorological reanalysis for 1951 through 2023, with the time series extended back to 1850 by random resampling so that even the oldest simulated stands, 140 years old, could be grown from bare ground through a spin-up phase to dynamic equilibrium.

The heart of the workflow is a stratification scheme that translates a whole country into a manageable set of representative stands. Environmental strata were built by crossing eight bioclimatic zones — from Mediterranean and sub-Mediterranean to lowland dry and wet, submontane, montane, subalpine, and azonal — with two soil types and two soil depths, yielding 18 combinations across the two countries. Forest strata combined six forest types (oaks, beech, pines, fir, spruce, and coppice), sixteen business-as-usual management regimes, and up to seven age classes, producing 54 strata for Croatia and 56 for Slovakia. Crossing the two yielded 486 modeling strata in Croatia and 616 in Slovakia, each simulated separately and then upscaled to the national level by multiplying results by the area each stratum represents. For the reporting period, the team assumed a uniform age-class distribution within each environmental zone and forest type, an application of the classic normal forest concept that smooths out artifacts from synchronized rotation events.

Validation was deliberately conservative. The researchers compared simulated aboveground wood carbon — converted to growing stock using country-specific conversion factors — against geo-referenced observations from the Croatian and Slovak forest management databases. Because the model assumes fully stocked stands while real forests include understocked ones, an uncorrected comparison revealed an overall overestimation of roughly 41 percent. The team therefore derived stocking correction factors from a quarter of the observational dataset, applied them only where they reduced predictions, and validated against the remaining 75 percent. After correction, the overestimation fell to about 4 percent, and the model achieved successful predictive performance, with a normalized root mean square error of 44 percent and normalized bias of 9 percent for Croatia, and 41 percent and 2 percent respectively for Slovakia. Performance was strongest for beech, oaks, and spruce, which explained 57 to 66 percent of the area-weighted variance, while pines, coppice, and fir — ecologically and managerially more heterogeneous groups — showed larger uncertainty.

Because validating deadwood, litter, and soil against field data was not feasible at the stratum level, the team evaluated those pools against published plausible ranges for European forests. Simulated annual net ecosystem exchange stayed mostly within the published range of minus 460 to plus 60 grams of carbon per square meter per year, with the expected exception of young stands, which acted as carbon sources for roughly 10 to 15 years after final harvest. Carbon stocks in all three pools remained within literature ranges throughout 1990 to 2023, and country totals compared credibly with national forest inventory figures: 214 versus 248 tonnes of carbon per hectare for Croatia in 2008, and 250 versus 277 tonnes per hectare for Slovakia in 2016.

The payoff came in the form of model-derived carbon stock change factors ready for use in the Common Reporting Tables of national inventories. Rather than reporting year-to-year values, which can jump abruptly when a large stratum reaches its rotation age in simulation, the team used the slope of each pool’s carbon time series over the reporting period as a proxy for the average annual change. Simulated soil organic carbon increased modestly in both countries, litter stocks were essentially stable, and deadwood showed slightly negative trends — a conservative result the authors attribute to model limitations, including the inability to represent historical wood extraction during spin-up and an assumed 90 percent extraction rate during salvage logging that likely overestimates real removals. Applying the new factors, and adding an estimate for Croatia’s heterogeneous forests out of yield, raised the previously reported national net CO2 removals for 2023 by 86.11 kilotonnes, or 1.6 percent, in Croatia, and by 138.61 kilotonnes, or 2.1 percent, in Slovakia.

A sensitivity and uncertainty analysis of the workflow itself revealed which methodological choices matter most. The representation of forest management caused the largest variation in growing stock estimates, exceeding 30 percent, followed by the stocking correction at roughly 25 percent. Environmental stratification and carbon-to-growing-stock conversion factors contributed moderate variability of 12 to 16 percent, while statistical uncertainty propagated through the upscaling step added only about 5 percent. The message is clear: for process-based models deployed at national scale, accurate management history and explicit treatment of stand structural variability are more decisive than the fine details of parameterization, and future model development should integrate stand structure directly rather than correcting for it afterward.

The authors are candid about the simplifications that remain. Tree species composition was held constant over the 34-year reporting period — defensible, they argue, because post-disturbance management in Croatia typically preserves composition and Slovakia’s observed shift from spruce to beech has occurred mainly in young stands with modest carbon impact. Age structure within each stratum was represented by a single fixed age, and mortality was kept constant. Disturbances other than drought were not represented, despite evidence of rising disturbance levels in both countries, which is one reason the simulated deadwood trends should be interpreted with caution. Even so, the workflow is conceptually transferable to other process-based models that provide comparable carbon pool outputs, and the modest size of the reported changes — 1.6 and 2.1 percent — sits comfortably within the workflow’s own estimated uncertainty range.

What makes this study resonate beyond two Central European countries is its timing. Europe’s forests have long been counted on as a reliable climate ally, yet recent research warns of sink saturation and growing disturbance pressure, making the accuracy of national LULUCF accounts a matter of continental consequence. By demonstrating that a transparent, validated, process-based modeling chain can supply country-specific carbon stock change factors for the very pools that field measurement programs have left uncovered, the team has turned a methodological gap into an actionable pathway. The increase in reported removals is small, but the strengthening of methodological completeness is not: it gives inventory compilers a defensible, reproducible estimate where previously there was silence, and it offers other nations a tested template for making their own forest carbon accounts whole.

Subject of Research: Country-scale process-based forest carbon modeling to derive carbon stock change factors for national LULUCF greenhouse gas inventory reporting in Croatia and Slovakia

Article Title: Country-scale forest carbon modeling to support national greenhouse gas inventories in Croatia and Slovakia

Article References: Ostrogović Sever, M. Z., Dobor, L., Merganič, J., Bitunjac, D., Marjanović, H., Hlásny, T., Anić, M., Hidy, D., Barcza, Z., Barka, I., Mendaš, P., & Merganičová, K. (2026). Country-scale forest carbon modeling to support national greenhouse gas inventories in Croatia and Slovakia. Regional Environmental Change, 26(4), Article 215. https://doi.org/10.1007/s10113-026-02705-9

Image Credits: AI Generated

DOI: 10.1007/s10113-026-02705-9

Keywords: forest carbon, Biome-BGCMuSo, greenhouse gas inventory, LULUCF, carbon stock change, Croatia, Slovakia, soil organic carbon, deadwood, process-based modeling, carbon sink, climate mitigation

The study’s central quantities are two of the most important currencies in ecosystem science. The first is net primary productivity, or NPP, which measures the amount of carbon that vegetation fixes through photosynthesis minus the carbon plants respire for their own maintenance — in effect, the gross income of an ecosystem’s carbon economy. The second is carbon use efficiency, or CUE, the ratio of the carbon actually incorporated into plant tissue to the total carbon fixed. A high CUE means an ecosystem is a disciplined saver, converting its photosynthetic earnings into wood, roots, and leaves rather than burning them off as respiration. Together, these two metrics determine whether a landscape acts as a growing carbon sink or a leaky one, and both are exquisitely sensitive to the physical conditions of the root zone.

To track these variables across a region the size of a small continent, the researchers turned to the Community Land Model version 5.0, a state-of-the-art land surface model developed for Earth system simulation. CLM5.0 integrates soil thermal and hydrological processes, vegetation dynamics, and biogeochemical cycling, allowing the team to simulate NPP and CUE across the plateau from 1979 to 2020. The model was constrained and evaluated against an impressive array of observational data: long-term in situ soil temperature records archived at the National Tibetan Plateau Data Center, eddy-covariance measurements of net ecosystem productivity and heterotrophic respiration from the Haibei research station, satellite-derived MODIS net primary productivity products, and independent NPP estimates from the CASA and VPM remote sensing models. Soil property maps and plant functional type distributions provided the underlying substrate and vegetation structure.

The simulation revealed a striking hierarchy among the plateau’s ecosystems. Forests, concentrated in the warmer and wetter southeastern margins, were the most productive, with a median NPP of 963.52 grams of carbon per square meter per year. Shrublands, however, proved to be the most frugal, achieving the highest median carbon use efficiency at 0.53 — meaning more than half of the carbon they fixed was retained in biomass rather than lost to respiration. Grasslands, which blanket the vast majority of the plateau, showed the most dramatic long-term trajectories: their NPP climbed by 2.16 grams of carbon per square meter per year each year, while their CUE declined by 0.0009 per year. That combination — rising gross productivity but falling efficiency — hints at a subtle but consequential shift in how these alpine ecosystems are handling a warming climate.

The declining CUE of grasslands deserves particular attention. Carbon use efficiency tends to fall when respiration outpaces photosynthesis, and warming accelerates both plant and microbial metabolism. Previous work cited by the team, including multi-model analyses of the Qinghai-Tibet Plateau, has suggested that continued climate change will erode the carbon use efficiency of terrestrial ecosystems across the region. The new results add a mechanistic dimension to that picture: the decline is not simply a response to warmer air, but is tightly coupled to the state of the soil, where permafrost thaw, altered drainage, and shifting moisture regimes reshape the environment in which roots and microbes operate. An ecosystem that fixes more carbon but spends proportionally more of it on respiration may accumulate biomass more slowly than its rising NPP would suggest.

To disentangle the relative influence of soil temperature and soil moisture, the researchers employed a random forest machine learning approach, a method well suited to capturing nonlinear relationships and interactions among many predictors. The analysis produced a clear seasonal signature. In spring and autumn — the shoulder seasons when the plateau’s vegetation is waking from or settling into dormancy — soil temperature was the dominant driver of NPP variation. This makes physical sense: during these periods, plant growth is often limited by cold soils, and the timing of spring thaw regulates when roots can access water and nutrients and when photosynthesis can resume. Earlier and warmer soil thawing has been shown to regulate the onset of growth in tundra and alpine biomes, and the new findings confirm that this temperature control extends across the plateau’s diverse vegetation types.

Summer told a different story. Once soils had warmed sufficiently, temperature ceased to be the binding constraint, and soil moisture took over as the key driver of net primary productivity. The plateau’s summer monsoon delivers the bulk of annual precipitation, and interannual variability in that moisture supply strongly modulates how much carbon vegetation can fix during the peak growing season. This finding aligns with global evidence that soil moisture exerts a large influence on long-term terrestrial carbon uptake, and it carries a sobering implication: as warming intensifies evapotranspiration and potentially destabilizes monsoon patterns, summer drought stress could become an increasingly important brake on the plateau’s carbon sink, even as longer and warmer growing seasons push in the opposite direction.

The vegetation-type analysis added yet another layer of nuance. For carbon use efficiency, soil temperature contributed more in grasslands, whereas soil moisture was the primary driver in shrublands and forests. These differences likely reflect the distinct ecophysiological strategies of the plant types involved. Grasses, with shallow root systems and rapid tissue turnover, are highly responsive to the thermal environment of the upper soil layers. Shrubs and trees, with deeper roots and woody structure, depend more heavily on sustained water availability, making their carbon allocation decisions more sensitive to moisture fluctuations. For land managers and carbon accountants, this means that a single regional parameterization of soil controls would misrepresent at least some of the plateau’s ecosystems; the rules of the carbon economy change with the vegetation.

Why does all of this matter beyond the plateau itself? The Tibetan Plateau, often called the Third Pole, holds one of the largest reservoirs of permafrost soil carbon outside the Arctic. As permafrost degrades and glaciers retreat, the soil hydrothermal regime is being rewritten, with consequences that ripple through the global carbon cycle. The study’s findings suggest that the trajectory of the plateau’s carbon sink will hinge on the coupled evolution of soil temperature and moisture — not on warming alone. A warmer but wetter plateau could continue to expand its vegetation carbon uptake, as the team’s earlier work on soil warming and wetting indicated, whereas a warmer and drier one could see productivity gains offset by respiration losses and declining efficiency. Regional carbon sink management and climate adaptation strategies, the authors argue, need to account for this hydrothermal coupling explicitly.

The study also demonstrates the growing power of combining process-based Earth system models with machine learning attribution. By simulating four decades of coupled soil and vegetation dynamics with CLM5.0 and then using random forests to apportion variance among drivers, the researchers achieved something neither approach could accomplish alone: a physically consistent reconstruction of ecosystem carbon behavior, paired with a data-driven ranking of its controls across seasons and vegetation types. The work was supported by the National Natural Science Foundation of China, the National Key R&D Program, and the Chinese Academy of Sciences, with simulations conducted using the Earth System Numerical Simulation Facility. As permafrost thaw accelerates across the world’s cold regions, this kind of quantitative attribution — knowing precisely when warmth matters and when water matters, and for which plants — will be essential for forecasting whether high-altitude and high-latitude ecosystems remain allies in the fight against climate change or become its amplifiers.

Subject of Research: Effects of soil temperature and moisture on vegetation carbon sequestration under climate warming on the Tibetan Plateau

Article Title: Quantifying the effects of soil hydrothermal conditions on vegetation carbon sequestration capacity under climate warming on the Tibetan Plateau

Article References: Peng, Q., Jia, B., Wang, L., Wu, R., & Huang, Q. (2026). Quantifying the effects of soil hydrothermal conditions on vegetation carbon sequestration capacity under climate warming on the Tibetan Plateau. Plant and Soil. https://doi.org/10.1007/s11104-026-09026-0

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09026-0

Keywords: Tibetan Plateau, net primary productivity, carbon use efficiency, soil temperature, soil moisture, permafrost degradation, climate warming, CLM5.0, random forest, grasslands, carbon sink, alpine ecosystems

The numbers behind the warning are stark. Across Europe, the rate at which forests are damaged by drought, storms, wildfire and insect outbreaks has more than doubled over the past three decades, and climate-driven damage already costs several billion euros every year. Particularly worrying is the rise of compound events, in which one disturbance sets the stage for another: a severe drought weakens trees, and a subsequent fire or pest outbreak then magnifies the losses and slows recovery even further. These cascading interactions are becoming more common as the climate warms, yet they remain poorly captured by conventional monitoring and assessment systems, which tend to evaluate each disturbance in isolation.

Summer 2026 has made the issue tangible for policymakers and the public alike. Prolonged heat and drought stressed forests across much of the continent, and by late August wildfires had burned more than 630,000 hectares within the European Union, roughly twice the twenty-year average for that point in the season. Giorgio Vacchiano of the University of Milan, author of the policy brief, stresses that resilience is not simply a question of whether a forest is still standing after a disturbance. The real question, he argues, is whether forests can maintain their functions, regenerate and adapt as conditions change, and if those processes are not measured, they cannot be managed.

The stakes extend far beyond the timber economy. Extreme events put biodiversity, rural livelihoods and cultural landscapes at risk, and they raise the likelihood of floods and landslides in vulnerable terrain. Europe’s forests currently absorb around 360 million tonnes of carbon dioxide each year, a service of enormous value to continental climate policy, but that carbon sink is weakening as stands age, harvesting intensifies and disturbances grow more frequent. Without deliberate adaptation, the brief warns, the European Union’s climate targets become progressively harder to meet, because a shrinking forest sink must be compensated by deeper emissions cuts elsewhere in the economy.

One of the brief’s core criticisms is that forest monitoring and reporting still concentrate largely on how much forest exists and how much biomass it holds. Those figures matter, but they reveal little about whether a given stand can resist a shock, recover afterwards or adjust to a changing climate over decades. A plantation of uniform, drought-stressed trees may report impressive standing volume on paper while possessing almost no capacity to regenerate after a fire. The brief therefore calls for a broader suite of resilience indicators covering recovery capacity, regeneration success, structural and functional diversity, landscape connectivity, and the ability of species to adapt in place or shift their ranges as conditions change.

Technology has a crucial role to play in this shift. Satellite observation can supply early-warning signals long before decline becomes visible to a forester walking the ground. A drop in photosynthetic activity detected from orbit, for instance, can indicate that recovery is slowing and that a stand is approaching a critical threshold beyond which degradation accelerates. Remote-sensing time series of this kind are most powerful when paired with long-term field observation and scenario-based models that combine three dimensions of risk simultaneously: the climate hazard itself, the vulnerability of the forest, and its adaptive capacity. Together, these tools allow policymakers and forest managers to test what-if futures and to target intervention where it will deliver the greatest benefit.

The brief also translates analysis into practice, setting out management approaches that can demonstrably strengthen resilience. Among them are Closer-to-Nature and Climate-Smart Forestry, greater diversity of tree species and forest structures, restoration of hydrological function in degraded catchments, and carefully planned assisted migration of suitable species and provenances to areas where the climate is shifting faster than natural dispersal allows. Biodiversity is central throughout this agenda: complementary species and functions help forests absorb uncertainty while continuing to store carbon, regulate water flows and support rural livelihoods. Monocultures, by contrast, may perform well under average conditions but fail catastrophically when an extreme event exceeds their narrow tolerance range.

To move from principles to policy, the authors recommend five directions for action. These include mainstreaming climate-smart planning using resilience indicators and scenario modelling; introducing quantitative resilience targets into national forest, climate, adaptation and nature restoration strategies; investing in long-term observation and research infrastructures such as eLTER; supporting biodiversity-based and closer-to-nature management through payments for ecosystem services and well-designed nature credits; and aligning forest management more closely with natural disturbance regimes so that resilience and carbon uptake are sustained together. At the regional level, the brief points to fire-prevention planning in Tuscany and Lombardy, where climate projections, vegetation dynamics and fire-behaviour models are already being used to prioritise areas for intervention before ignition occurs.

Underpinning the entire argument is the claim that long-term observation is the missing link in European forest policy. Resilience cannot be read off a single measurement or judged only in the aftermath of a disaster; it has to be observed across years and decades. Through its distributed network of long-term research sites and socio-ecological platforms, eLTER tracks tree growth and mortality, soil moisture, carbon pools and water balance over exactly those timescales. Sustained field observation supplies the evidence needed to calibrate models and to test whether management interventions genuinely improve resistance and recovery, while comparable observations from across Europe make it possible to identify which approaches work, under which conditions and with which trade-offs.

Vacchiano summarises the case plainly: long-term observations are what turn resilience from an appealing concept into something that can be tested and improved, allowing scientists to see whether recovery is slowing, whether a forest is approaching a threshold, and whether management is actually increasing its capacity to cope with future extremes. Europe’s forests will keep meeting climate shocks, and the brief’s conclusion is that the continent faces a clear choice between reacting after each damaging event and building, in advance, the capacity to anticipate, absorb, recover and adapt. Whether that choice is made in time may determine not only the fate of Europe’s woodlands but the credibility of its climate commitments.

Subject of Research: Measuring and building the resilience of European forests against extreme climate events

Article Title: Europe's forests are still standing, but many are losing the ability to recover

Article References: Europe's forests are still standing, but many are losing the ability to recover. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: forests, climate change, resilience, eLTER, wildfire, drought, carbon sink, biodiversity, forest management, long-term monitoring, remote sensing, policy brief

The research, led by Yun-Soo Na and Sang-Wook Yeh of Ewha Womans University in Seoul, together with Jong-Seong Kug of Seoul National University and Young-Min Yang of Jeonbuk National University, set out to answer a deceptively simple question: how strongly does vegetation productivity in East Asia respond to the year-to-year growth rate of atmospheric carbon dioxide? The answer matters because East Asia is a region of extraordinary climatic and ecological diversity, spanning the monsoon-drenched forests and croplands of China, Korea, and Japan as well as the drier grasslands and barren expanses of the interior. Understanding how these contrasting landscapes respond to a changing atmosphere is essential for projecting the future of the global carbon cycle.

To quantify that response, the team drew on twelve Dynamic Global Vegetation Models from the TRENDY version 13 ensemble, the same suite of models that underpins the annual Global Carbon Budget, covering the period from 1959 to 2023. Their methodology was meticulous. They first removed the long-term trends from both gross primary productivity, the measure of carbon absorbed by plants through photosynthesis, and the atmospheric carbon dioxide growth rate, using a nonlinear smoothing technique called LOWESS. They then performed linear regressions within 20-year moving windows, defining the slope of each regression as the sensitivity of productivity to carbon dioxide growth. The approach captures the combined ecosystem response to carbon dioxide, climate variability, and land-use change together, rather than isolating the fertilizing effect of carbon dioxide alone.

The first striking result concerned net ecosystem production, the net balance between carbon taken up by photosynthesis and carbon released by respiration. Eleven of the twelve vegetation models simulated a negative sensitivity, meaning that when atmospheric carbon dioxide grew faster, East Asian ecosystems tended to take up less carbon, and vice versa. After applying statistical screening based on the most recent two decades of data, the researchers retained nine models for detailed analysis. The spatial pattern of productivity sensitivity that emerged was anything but uniform: central-eastern China, Korea, and Japan behaved very differently from the northern and western parts of the region, prompting the team to divide East Asia into a monsoon region and a non-monsoon region for all subsequent analysis.

When the researchers tracked sensitivity through time, a clear and troubling trajectory appeared. In the non-monsoon region, net ecosystem production sensitivity remained negative throughout the record, briefly approaching zero in the late 1990s before turning more negative again. In the monsoon region, sensitivity started out weakly positive but gradually declined, crossing into negative territory around the 1990s. Gross primary productivity told the same story with even greater amplitude: positive sensitivity in the monsoon region weakened and flipped negative in the late 2000s, while the non-monsoon region drifted back toward strongly negative values. In both regions, the inverse relationship between carbon dioxide growth and carbon uptake has been intensifying, suggesting that faster atmospheric carbon dioxide accumulation now goes hand in hand with weaker photosynthetic carbon absorption across East Asia.

Why is this happening? The answer, it turns out, depends on where you look. In the non-monsoon region, the decline in productivity sensitivity tracked soil moisture sensitivity almost perfectly, with a correlation coefficient of 0.85 and soil moisture explaining 72 percent of the variance in productivity sensitivity. This is a region dominated by grasslands and barren terrain, where water is chronically scarce. When the carbon dioxide-associated response of soil moisture weakened, vegetation activity weakened with it. The analysis of transpiration added a further layer of detail: reduced stomatal conductance accompanied by reduced transpiration did not translate into meaningful gains in soil water in this dry environment, so the plants gained no compensating benefit and photosynthesis remained constrained.

The monsoon region presented a strikingly different picture. There, where rainfall is comparatively abundant, soil moisture sensitivity actually increased over time, moving from negative to positive values, while productivity sensitivity moved in the opposite direction, yielding a significant negative correlation of minus 0.65. The real culprit was light. Photosynthetically active radiation, the portion of sunlight that plants use for photosynthesis, showed a distinct declining trend in the monsoon region, and productivity sensitivity fell in step with it, with a positive correlation of 0.72 and radiation explaining 52 percent of the variance. In other words, even when water was plentiful, dimming skies limited the plants’ capacity to convert rising carbon dioxide into additional growth. The researchers also found that this radiation control strengthened over time: when they split the record into early and late periods, the explanatory power of radiation in the monsoon region rose from 21 percent to 59 percent.

Vegetation structure appears to underpin much of this regional contrast. Using satellite-based land cover data from the MODIS instrument, the team showed that the non-monsoon region is dominated by grasslands and barren surfaces, while the monsoon region is dominated by croplands and woody savannas, ecosystems with fundamentally higher baseline productivity and different water-use strategies. These structural differences, combined with contrasting hydroclimatic regimes, help explain why the same global driver, the rising atmospheric carbon dioxide growth rate, produces such divergent local responses. The findings were robust to methodological choices: the researchers repeated their analysis with moving windows of 10, 15, 25, and 30 years and with nonparametric Spearman correlations, and the main patterns held.

The implications reach far beyond East Asia. Global studies have already suggested that the carbon dioxide fertilization effect on vegetation has been weakening in recent decades, and that the positive contribution of carbon dioxide to productivity trends has roughly halved since the 2000s. This study adds a crucial regional dimension, showing that the weakening is governed by different limiting factors in different places, water in the dry interior, light under the monsoon skies. If the sensitivity of ecosystems to carbon dioxide growth continues to decline, the terrestrial carbon sink may absorb proportionally less of future emissions, leaving more carbon dioxide in the atmosphere and accelerating warming. The authors argue that future carbon cycle projections and carbon budget assessments must explicitly account for regional climatic constraints, particularly soil moisture and radiation, rather than treating the land surface as a homogeneous sponge.

There is also a message here for policy. Carbon neutrality strategies, the researchers suggest, should be designed with regional specificity, because the capacity of natural ecosystems to buffer human emissions depends on local climate systems and vegetation characteristics that vary enormously even within a single continent. The study’s authors are careful to note that their sensitivity measure reflects statistical associations within the coupled Earth system rather than isolated causal effects, and that correlation analysis alone cannot fully establish causality. Even so, the convergence of evidence from twelve independent vegetation models, satellite land cover observations, and six decades of atmospheric measurements paints a coherent picture: East Asia’s ecosystems are becoming less responsive to rising carbon dioxide, and the planet’s carbon arithmetic may be shifting as a result. As atmospheric carbon dioxide continues its climb, the question of whether forests, grasslands, and croplands can keep pace is no longer academic, and this study suggests the answer will be written region by region, in soil moisture and sunlight.

Subject of Research: Regional sensitivity of East Asian ecosystem productivity to atmospheric CO2 growth

Article Title: Regional contrasts of ecosystem productivity sensitivity to atmospheric CO2 growth across East Asia

Article References: Na, Y.-S., Yeh, S.-W., Kug, J.-S., & Yang, Y.-M. (2026). Regional contrasts of ecosystem productivity sensitivity to atmospheric CO 2 growth across East Asia. Earth System Dynamics, 17(5), 1381-1394. https://doi.org/10.5194/esd-17-1381-2026

Image Credits: AI Generated

DOI: 10.5194/esd-17-1381-2026

Keywords: carbon cycle, East Asia, gross primary productivity, atmospheric CO2 growth rate, soil moisture, photosynthetically active radiation, monsoon, TRENDY vegetation models, carbon sink, land cover, climate-vegetation feedback, Earth System Dynamics

The stakes of this measurement problem are enormous. Terrestrial ecosystems absorb roughly one quarter of the carbon dioxide released by human activities, a service that significantly slows the rise of atmospheric CO2 and the pace of global warming. NEE, defined as the difference between the CO2 released by ecosystem respiration and the CO2 sequestered by photosynthesis, is the quantity that tells us whether a landscape is a net carbon sink or source. Yet NEE can only be measured directly at the plot scale, using eddy covariance towers that monitor the vertical exchange of CO2 between vegetation and air. Everything beyond the tower footprint must be estimated, and that is where the disagreements begin.

Scientists have traditionally taken two routes to continental-scale carbon budgets. Top-down atmospheric inversions combine measurements of atmospheric CO2 concentrations with transport models to infer surface fluxes, offering an independent perspective but at coarse spatial resolutions limited by sparse sampling. Bottom-up approaches use process-based terrestrial biosphere models or data-driven machine learning to extrapolate tower observations across landscapes. The trouble is that bottom-up estimates have often diverged dramatically from inversions, partly because conventional machine learning treats each time step independently and fails to capture the complex, nonlinear ways ecosystems respond to disturbances and climate extremes. Ecosystems remember: a drought can suppress carbon uptake for months or years after the rains return, and most models simply do not carry that memory.

The LSTM architecture is what sets MemoryFlux apart. Developed originally to solve long-term dependency problems in sequence modelling, the network uses a six-month look-back window of historical climate and vegetation data to predict current carbon exchange, explicitly encoding the legacy effects of antecedent conditions. The team trained separate ecosystem-specific models for ten major plant functional types, from evergreen needleleaf forests to permanent wetlands, using tower-measured meteorology combined with a rich suite of satellite observations. Those predictors included the normalized difference vegetation index, leaf area index, the fraction of absorbed photosynthetically active radiation, and solar-induced chlorophyll fluorescence, a direct signal of photosynthetic activity, alongside ERA5-Land climate reanalysis variables such as temperature, radiation, precipitation, soil water content, and vapour pressure deficit.

The validation results are striking. MemoryFlux’s seasonal cycle of NEE correlated at r=0.96 with the ensemble mean of the OCO-2 v10 Model Intercomparison Project inversion and at r=0.97 with CarbonTracker2022, both top-down estimates derived from fundamentally different methodology. Perhaps more importantly, the mean annual carbon sink of −1.27 ± 0.12 petagrams of carbon per year sits far closer to the inversion range of −0.83 to −0.70 petagrams than existing machine-learning upscaling products, which have suggested sinks as large as −3.30 petagrams per year. That gap between bottom-up and top-down estimates has long been one of the most stubborn discrepancies in regional carbon cycle science, and narrowing it builds confidence in both approaches.

One of the dataset’s most celebrated achievements is its reproduction of the Midwest Corn Belt phenomenon. Atmospheric inversions have consistently shown that the croplands of the Upper Midwest pull in enormous amounts of carbon during the peak growing season in July and August, a continental-scale signal recognized as a model benchmark since the early days of the CarbonTracker project. Yet most existing global flux upscaling datasets fail to capture it, instead placing their strongest seasonal uptake in the southeastern United States. MemoryFlux correctly identifies the Corn Belt as the dominant carbon-uptake region during the peak growing season, matching the empirical evidence and the inversion picture, even though the uptake is transitory because most of the absorbed carbon ends up in harvested crops consumed by humans and livestock.

The spatial patterns across the continent also align with ecological understanding. The strongest annual carbon uptake appears in the humid southeastern United States, followed by the northern Pacific Coast and tropical regions, while major carbon sources concentrate in the tundra of northern and central Canada and the arid central United States, where warming could release soil carbon and accelerate climate change. Forests and wooded ecosystems emerge as the continent’s dominant carbon sink, contributing a mean uptake of −0.76 petagrams of carbon per year, with MemoryFlux attributing more than 85 percent of the total sink to forests, a share higher than most other products suggest.

To test whether the memory mechanism actually matters, the researchers ran a controlled experiment. They built a parallel dataset, dubbed nonMemoryFlux, using the same predictors, architecture, and validation scheme but feeding the model only contemporaneous variables, with no look-back window. The differences were substantial. At the plant functional type level, the coefficient of determination rose from 0.63 to 0.79 when historical information was included, and error metrics dropped accordingly. The memory-free version also estimated stronger carbon uptake in recent years, precisely the period when the 2015/16 El Niño and repeated droughts and heatwaves struck North America, suggesting it failed to capture the lingering legacy of those extremes. The gap between the two versions reached 186 teragrams of carbon in a single year, about 14.6 percent of the mean continental uptake.

MemoryFlux also proved its worth during climate disasters. The researchers examined six major events, including the 2011 drought in Mexico and the southern United States, the 2012 North American drought, the 2013 California drought, the 2017 flash drought across the northern plains, the 2019 Midwest floods, and the southwestern drought and wildfires of 2020 to 2021. In each case, the dataset’s spatial anomaly patterns coincided with negative soil moisture and fluorescence anomalies and with the documented extent of the events, showing anomalous carbon release where ecosystems were stressed. The memory-equipped version represented these regional anomaly patterns more clearly than its memory-free counterpart, particularly for the 2011 and 2012 droughts and the 2019 flood.

The authors are careful about limitations. Flux tower coverage remains uneven, with some ecosystem types represented by only two sites, and the dataset lacks a fully spatially explicit uncertainty framework. A mismatch between tower-scale training data and gridded reanalysis predictors introduces additional uncertainty, and the static land-cover map cannot track real transitions such as cropland expansion or fire-induced vegetation change. Differences with inversions persist in the managed Midwest croplands, hinting that human management information could further improve the models. Still, with the dataset and code openly available, MemoryFlux offers climate scientists a powerful new lens on how a continent’s ecosystems respond to a rapidly changing climate, and a template for bringing memory into the next generation of carbon cycle models worldwide.

Subject of Research: LSTM-based upscaling of net ecosystem CO2 exchange across North America from flux tower and satellite observations

Article Title: Improved estimation of net ecosystem CO2 exchange over North America using LSTM-based flux upscaling (2001–2021)

Article References: Huang, C., He, W., Byrne, B., Nguyen, N. T., Xiao, J., Yang, H., Ciais, P., Wang, S., Li, X., Ma, H., Xu, P., Zhao, M., Chen, H., & Ju, W. (2026). Improved estimation of net ecosystem CO 2 exchange over North America using LSTM-based flux upscaling (2001–2021). Earth System Science Data, 18(10), 7367-7390. https://doi.org/10.5194/essd-18-7367-2026

Image Credits: AI Generated

DOI: 10.5194/essd-18-7367-2026

Keywords: carbon cycle, net ecosystem exchange, LSTM, deep learning, MemoryFlux, eddy covariance, atmospheric inversion, drought, Corn Belt, remote sensing, North America, carbon sink

Ground-level ozone is not emitted directly by fires. Instead, it is a secondary pollutant, formed when reactive gases produced by combustion react chemically in the presence of sunlight. In the lower atmosphere, ozone is harmful to human health and, crucially, interferes with the physiology of plants. When ozone enters leaf tissue through the same microscopic pores that trees use to absorb carbon dioxide, it damages cells and impairs photosynthesis. For a forest already stressed by drought and fire, this additional burden means that the trees that survive a blaze are less able to resume their role as carbon absorbers in the months and years that follow. The result is a double blow to the climate: fires release carbon dioxide directly when biomass burns, and the ozone they generate suppresses the ability of the remaining forest to capture and store that gas.

The research team quantified this effect using nearly three decades of observations and a global vegetation model, tracking how ozone damage evolved between 1997 and 2024 alongside patterns of fire activity and drought. Their analysis shows that the impact of fire-driven ozone is strongest during major droughts, when hot, dry conditions simultaneously fuel more fires and leave vegetation more vulnerable to pollution damage. Alarmingly, three of the most extreme Amazon droughts of the past three decades — in 1997/98, 2015/16 and 2023/24 — all occurred during El Niño events, the warm phase of a natural, recurring global climate cycle. While El Niño is not caused by human activity, climate change means it now sits atop rising baseline temperatures, making it more likely to push global temperatures to record highs and intensify extreme weather.

Lead author Dr Flossie Brown, of ETH Zurich, emphasized that the problem extends well beyond the flames themselves. Forest fires do not just release carbon dioxide when they burn, she explained; they also contribute to the rise in ground-level ozone, a pollutant that damages the leaves of surviving trees and reduces their ability to keep absorbing carbon afterwards. According to the study, this hidden effect is equivalent to around a quarter of the carbon released by the fires themselves — a significant loss to the Amazon’s carbon budget that had not previously been considered. In other words, every hectare of burned forest inflicts a further, largely unmeasured penalty on the intact forest around it, eroding the region’s capacity to recover the carbon that has been lost.

The drought years examined in the study each left a distinct signature in the data, but the most recent event stands out starkly. Ozone damage during the 2023/24 drought nearly doubled compared with the average of the previous decade, a jump that coincided with record fire activity across the basin. Dr Brown warned that, given a comparably strong El Niño appears to be developing again this year, the researchers are concerned that history could repeat itself. Forecasters have indicated that the emerging El Niño has the potential to become one of the most intense on record, raising the prospect of another major spike in this hidden carbon loss. If drought conditions and fire activity mirror those of 2024, the ozone-driven suppression of photosynthesis could once again strip a substantial fraction of the Amazon’s remaining carbon uptake capacity at precisely the moment it is most needed.

The mechanics of this damage are rooted in the chemistry of the tropical atmosphere. Wildfires release a cocktail of precursor gases, including nitrogen oxides and volatile organic compounds, which react under the intense sunlight of the tropics to produce ozone near the ground. Unlike the stratospheric ozone layer that shields the Earth from ultraviolet radiation, ground-level ozone is a pollutant. In plants, it enters through stomata — the tiny pores on leaf surfaces that regulate gas exchange — and triggers oxidative stress that damages cellular machinery. Stressed trees may close their stomata to limit ozone uptake, but doing so also restricts the influx of carbon dioxide, directly reducing photosynthesis. Over large areas and extended periods, this physiological impairment translates into measurably lower carbon uptake across the forest, compounding the losses from drought stress and fire mortality.

What makes the new findings particularly consequential is that the ozone effect operates on surviving forest rather than burned land. Conventional carbon accounting for wildfires focuses on the immediate emissions from combustion and the slower losses from tree death and decomposition. The ozone penalty, by contrast, is invisible in satellite images of smoke and scorched earth, yet it accumulates across vast swathes of intact forest downwind of burning areas. By combining long-term observational records with a global vegetation model, the researchers were able to isolate this signal and express it in carbon budget terms, showing that the atmosphere suffers significantly more damage from each Amazon fire season than direct emissions alone would suggest.

There is, however, a clear and actionable message embedded in the research. Almost all fires in the Amazon are started by people, whether through deliberate land clearance or through agricultural burning that escapes into standing forest. The worst ozone damage is concentrated in the so-called Arc of Deforestation, the frontier zone where agricultural land is expanding into the rainforest. Professor Stephen Sitch, of the University of Exeter, stressed that this means the extra ozone damage described in the study is largely preventable. Reducing deforestation and forest degradation would cut direct fire emissions, but the study shows it would also protect the Amazon from this secondary, invisible source of carbon loss. The same policy lever, in other words, addresses both problems at once.

Co-author Dr Alexander Cheesman, of James Cook University, argued that the findings demonstrate why air pollution, land-clearing and climate change cannot be treated as separate problems when determining the future of the Amazon. These impacts interact and need to be considered together, he said, but that interaction also means solutions may deliver multiple benefits. Policies that tackle deforestation and degradation address both the carbon dioxide released directly by fires and the ozone pollution quietly eroding what is left of the forest’s ability to soak that carbon back up. In a region where the margin between sink and source grows thinner with each drought, such co-benefits could prove decisive.

As the developing El Niño raises the specter of another record fire season, the study serves as a timely reminder that the true climate cost of Amazon fires is greater than the smoke plumes suggest. The research was funded by the Natural Environment Research Council, partly via the GW4+ Doctoral Training Partnership, and the underlying paper is entitled Fire-derived ozone and intensifying droughts undermine the Amazon carbon sink. Its central conclusion is stark: every fire season in the Amazon now carries a hidden surcharge, paid not in flames but in the diminished photosynthesis of the trees that survive. Protecting the world’s largest rainforest, the authors make clear, requires confronting not only the fires themselves but the polluted air they leave behind.

Subject of Research: Fire-derived ground-level ozone pollution and drought reducing carbon uptake in the Amazon rainforest

Article Title: Wildfire ozone pollution weakening Amazon's ability to absorb carbon

Article References: Wildfire ozone pollution weakening Amazon's ability to absorb carbon. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Amazon rainforest, ozone pollution, wildfires, carbon sink, El Niño, drought, deforestation, climate change, photosynthesis, Communications Earth & Environment, Arc of Deforestation, ground-level ozone