Forest fires pose significant threats to ecosystems and can cause irreversible damage beyond the burned areas. The workflow combined Object-Based Image Analysis with Random Forest and Gradient Tree Boosting algorithms on the Google Earth Engine platform. The researchers segmented the Sentinel-2 imagery with the Simple Non-Iterative Clustering algorithm before applying the classifiers.

Four remotely sensed indices were calculated and included as model inputs: the Mid-Infrared Burn Index, Normalized Burn Ratio 2, Burn Area Index and Normalized Difference Vegetation Index. The study’s scope included four Mediterranean forest areas in Türkiye, followed by transferability tests at selected sites in Greece and Spain. Both machine-learning approaches produced high reported overall accuracies in the initial analysis, with Random Forest reaching 93.5–97.7% and Gradient Tree Boosting reaching 92.9–96.8%.

When the models were transferred to the comparison sites in Greece and Spain, both retained overall accuracies above 83%. These results support the potential use of object-based Random Forest and Gradient Tree Boosting models for burned-forest mapping within the tested Mediterranean environments. They do not establish that the same performance would extend to locations with different climates, vegetation types, fire regimes or satellite-image conditions.

The accessible source for this report provides the study abstract rather than the complete methods and results. As a result, the number of test samples, uncertainty estimates, site-specific error patterns and any comparisons with other classification methods cannot be assessed here. The reported percentages describe overall accuracy for the evaluated models, not perfect identification of burned forest in every landscape.

Even so, the study demonstrates that an object-based Sentinel-2 workflow can combine image segmentation, four burn- and vegetation-related indices and tree-based machine learning to map burned forests in Türkiye and maintain useful reported accuracy at selected Mediterranean transfer sites.

Subject of Research: Transferability of object-based machine-learning models for burned-forest mapping with Sentinel-2 imagery in Mediterranean regions

Article Title: Post-fire burned forest area mapping with Sentinel-2 imagery: evaluating object-based machine learning models and transferability

Article References: Bulut, F. S., Turker, M., & Ateşoğlu, A. (2026). Post-fire burned forest area mapping with Sentinel-2 imagery: evaluating object-based machine learning models and transferability. Natural Hazards, 122(22), Article 679. https://doi.org/10.1007/s11069-026-08470-6

Image Credits: AI Generated

DOI: 10.1007/s11069-026-08470-6

Keywords: Sentinel-2, burned forest mapping, machine learning, Random Forest, Gradient Tree Boosting, Object-Based Image Analysis, Google Earth Engine, Mediterranean forests, remote sensing, post-fire assessment, Post-fire, burned

The work builds on the second edition of Chile’s vegetation classification and cartography, developed by Luebert and Pliscoff in 2017. Chilean government conservation agencies and organizations already use the national vegetation units as surrogates for ecosystems in systematic planning, including the identification of new protected areas. Researchers have also used them to examine climate-change effects, assess the impacts of Chile’s severe 2017 fires and establish categories of ecosystem risk based on International Union for Conservation of Nature guidelines. The new linkage extends that nationally useful framework toward the EcoVeg approach, which is intended to provide an international standard for classifying vegetation.

To make the correspondence, the researchers first assigned each zonal vegetation unit to an EcoVeg formation by combining coarse vegetation physiognomy with macroclimate. They then used the names and descriptions of the vegetation belts to evaluate biogeography, diagnostic species, growth forms, bioclimate, dynamics and climate-related hydrology. The main reference was the published list of American macrogroups, supplemented where necessary with proposed new units following established EcoVeg criteria. The macrogroup level was selected because the finer group level remains largely undeveloped in Latin America, although the authors believe some Chilean units may eventually fit better at that level. Chilean zonal vegetation units, or vegetation belts associated with broad climatic and geographic zones, formed the population of 125 units analyzed in the study.

Four formation classes account for Chile’s zonal vegetation. Forest and woodland vegetation occurs in central and southern Chile across climates ranging from Mediterranean to cold antiboreal conditions and includes sclerophyllous, deciduous, lauriphyllous and evergreen forests. Ten macrogroups in this formation class received 55 zonal units. Shrub and herb vegetation, discontinuously distributed through central Chile, the far north and Patagonia, includes thorny scrub, Patagonian grassland and moorland; 18 units were assigned to six macrogroups in four formations. Another 33 units fall within desert and semi-desert formations, chiefly in northern Chile but also in the Mediterranean climatic zone of the central Andes. Nineteen units of high-mountain scrub, grassland and forb vegetation were assigned to three macrogroups, bringing the zonal total to all 125 units.

The analysis proposed additions that recognize vegetation characteristics not adequately represented in the existing international list. The authors introduced a Mediterranean Forest and Woodland formation and a Chilean Mediterranean Forest and Woodland division to accommodate the sclerophyllous and deciduous forests of central Chile. They also proposed the Valdivian Temperate Conifer Forest and Woodland macrogroup within the Cool Temperate Forest and Woodland formation. Two additional units, Magellanian Antiboreal Deciduous Forest and Magellanian Antiboreal Evergreen Forest, were needed because the existing classification did not distinguish both evergreen and deciduous Magellanian forests under an antiboreal bioclimate. These proposals extend the international framework rather than merely applying it unchanged, providing specific units for vegetation that the authors concluded was either absent or insufficiently differentiated in the earlier macrogroup list.

Several mismatches emerged where physiognomy, climate and biogeography do not align neatly. Chilean formations and International Vegetation Classification formations are both largely based on physiognomic and ecological criteria, but the international system combines multiple previous classification approaches. The authors found a particular difficulty in deciding whether macroclimate or biogeography should take precedence at different levels. For example, forests dominated by Nothofagus pumilio and Nothofagus betuloides can display similar structure and occur in both temperate and antiboreal climates. They are placed in different regional divisions because of biogeography, then distinguished as deciduous and evergreen macrogroups through growth form and dominant species. The authors also questioned the global suitability of terms such as “Boreal” and “Alpine” in formations that occur in the Southern Hemisphere, suggesting that such names and others with the same problem should be revised to make the international system more globally applicable.

Central Chile provided a further test of the hierarchy because its Mediterranean-climate forests were accommodated within a broader warm-temperate formation that combined sclerophyllous and deciduous vegetation. The proposed Chilean division reflects differences in floristic composition and phylogenetic diversity from other parts of the country, and the authors suggest it could eventually include appropriate Mediterranean-climate units elsewhere, including parts of California, the Mediterranean basin, South Africa and Australia. They also proposed placing Mediterranean high-Andean scrub and grassland in the cool semi-desert formation rather than the tropical high-mountain formation used in the existing list. These judgments expose differences among climate definitions, including the seasonal Mediterranean bioclimate used in the Chilean classification and systems in which Mediterranean climates are classified within temperate zones. The authors note that alternative definitions may differ in hierarchical position and spatial extent, so these assignments are not entirely independent of the climatic system adopted.

Not every existing macrogroup could be matched cleanly. Some were absent from the Chilean inventory, including Southern Andean Montane Salt Marsh and Sechura Atacama Semi-Desert Cliff and Pavement, while others could not be identified confidently from the national descriptions. Xeric Puna succulent scrub, represented in Chile by locally abundant Trichocereus atacamensis vegetation, had been embedded within broader high-elevation units rather than recognized separately. The division of Chile’s coast into Atacama and Peruvian Sechura components remains potentially contentious because the deserts have been described as floristically very different in some studies, although the authors cite phylogenetic and floristic evidence for broader relationships and retained the wider biogeographical treatment. These examples show why international classification requires explicit decisions about boundaries and hierarchy, not just a direct one-to-one translation of national maps.

Vegetation that does not follow the climatic zonation of the landscape proved more difficult. The researchers provisionally assigned intrazonal units to 23 macrogroups, 23 divisions and 17 formations, but some correspondences are doubtful because Chile’s intrazonal categories are broad and lack sufficiently detailed descriptions. Aquatic vegetation, including floating, natant, submerged, semi-aquatic and ephemeral-wetland communities, and open-rock vegetation on coasts, cliffs, inland outcrops, landslides and caves were also considered. Moorlands in southern Chile could not be placed in a dedicated macrogroup and were associated with bog and fen categories, even though they may be more closely related to azonal wetlands. Units dominated by Nothofagus antarctica also resisted formation-level placement because the species may grow as a large shrub or small tree yet strongly determines the vegetation’s physiognomy. The researchers included these units in forest formations because accommodating them in a new macrogroup could require major changes to the international classification.

Overall, the study shows that most of Chile’s mapped zonal vegetation can be represented within the EcoVeg hierarchy, while the proposed new formations, divisions and macrogroups identify places where the international system needs adjustment. The accompanying macrogroup map is available as a shapefile, and the authors present it as a tool that can facilitate collaboration across borders. A separate effort is reportedly under review to translate Chilean phytosociological units directly into International Vegetation Classification units down to association level, potentially adding secondary, degraded and ruderal vegetation. The present results remain a cartographic and classificatory contribution: they do not demonstrate improved conservation outcomes, and the authors explicitly characterize the intrazonal assignments as preliminary. Describing and classifying those non-zonal communities remains a major pending task in Chilean vegetation science.

Subject of Research: International classification and mapping of Chilean zonal and intrazonal vegetation

Article Title: The vegetation of Chile and the EcoVeg approach in the context of the International Vegetation Classification project

Article References: Luebert, F., & Pliscoff, P. (2022). The vegetation of Chile and the EcoVeg approach in the context of the International Vegetation Classification project. Vegetation Classification and Survey, 3, 15-28. https://doi.org/10.3897/vcs.67893

Image Credits: AI Generated

DOI: 10.3897/VCS.67893

Keywords: Chilean vegetation, EcoVeg, International Vegetation Classification, vegetation mapping, biogeography, ecosystem classification, Mediterranean forests, Patagonian grasslands, Magellanian forests, conservation planning, vegetation, Chile

The research, published in Environmental Monitoring and Assessment, was conducted by Salih Malkoçoğlu of Muğla Sıtkı Koçman University and Ergün Kahveci of Tokat Gaziosmanpaşa University. Their study site could hardly be more timely or more representative of the Mediterranean’s fire problem. In 2025, the Köyceğiz-Akköprü fire swept through a forest dominated by Pinus brutia, the Turkish red pine, a species that anchors vast stretches of the eastern Mediterranean’s fire-adapted landscapes. Rather than relying solely on satellite pixels, the researchers walked the burned ground themselves, laying down a dense network of measurement transects that recorded what was actually covering the soil, point by point.

The field protocol was meticulous. In each of 73 sampling plots, the team established two orthogonal transects, each 10 meters long, and recorded surface conditions at every 1-meter interval. That effort produced 1,601 individual point observations, each assigned to one of seven mutually exclusive surface-cover categories. This kind of transect-based ground cover measurement is a standard technique in fire effects monitoring, but what makes the new study distinctive is how directly it confronts the satellite record. For every plot, the researchers computed three Sentinel-2-derived indices: the differenced normalized burn ratio, known as dNBR; its relativized cousin, RdNBR; and the normalized difference vegetation index, NDVI.

Each of these indices has a long pedigree. dNBR, formalized by Key and Benson for the U.S. Forest Service’s FIREMON program, compares pre-fire and post-fire reflectance in the near-infrared and shortwave-infrared bands, where healthy vegetation and charred ground diverge most sharply. RdNBR, introduced by Miller and Thode in 2007, rescales that difference by pre-fire vegetation density, in principle allowing severity to be compared across stands that were structurally different before the fire. NDVI, dating back to Tucker’s foundational work in 1979, tracks the red and near-infrared contrast that signals photosynthetically active green vegetation. All three are staples of post-fire assessment, and all three are routinely treated as proxies for burn severity.

The regression models built in the new study tell a very different story. NDVI emerged as the index most tightly coupled to what was actually on the ground after the fire: its model had the highest explanatory power, with an adjusted R-squared of 0.439, and it was positively associated with live cover, carrying a standardized coefficient of +0.369. In plain terms, the greener the ground cover measured along the transects, the higher the NDVI recorded from orbit. That is exactly what one would hope for from a vegetation index, and it confirms that NDVI is picking up genuine early recovery signals, the resprouting shrubs, herbaceous flushes, and surviving understory that appear in the first growing season after a Mediterranean fire.

dNBR, by contrast, refused to behave as a pure measure of burn severity. Its strongest associations were not with post-fire surface conditions at all, but with pre-fire tree cover and with slope. The index, in other words, was largely encoding the structural and topographic context that existed before the flames arrived. This finding resonates with a growing body of literature, including work by Viedma and colleagues in southeastern Spain, showing that pre-fire vegetation and terrain often dominate the spectral signal that dNBR registers. A satellite index that is supposed to describe what the fire did may, in heterogeneous Mediterranean terrain, be describing mostly what was there to burn and where it stood on the landscape.

Perhaps the most intriguing result concerns RdNBR, the relativized index designed specifically to correct for pre-fire conditions. Instead of cleanly isolating fire effects, RdNBR showed a negative association with needle litter. The researchers interpret this as evidence that relative fire severity indices remain sensitive to residual organic cover, the layers of needles, duff, and litter that survive or accumulate after a burn. Because RdNBR normalizes by pre-fire vegetation, patches that retained substantial organic ground cover can register as less severely burned even when the fire’s actual effects on soils and surviving biota were substantial. The very adjustment meant to make the index more comparable across sites appears to entangle it with the organic residue that Mediterranean pine forests characteristically leave behind.

The team did not stop at the first round of models. Because ecological measurements taken across a landscape are rarely statistically independent, nearby plots tend to resemble one another, the researchers ran spatial robustness analyses that accounted for residual spatial dependence in their data. The principal associations survived. NDVI remained tied to live cover, dNBR to pre-fire structure and topography, and RdNBR to residual organic components. This methodological rigor matters, because spatial autocorrelation is a well-known source of inflated confidence in landscape-scale regression studies, a point emphasized in the geographical ecology literature since Diniz-Filho and colleagues’ influential critique of so-called red herrings in spatial analysis.

The practical upshot is a reframing of how satellite indices should be used in post-fire assessment. Rather than treating dNBR, RdNBR, and NDVI as three interchangeable dials reading the same underlying quantity of burn severity, the study shows they are complementary instruments, each tuned to a different ecological component of the post-fire landscape. dNBR, in this Mediterranean setting, functions largely as a recorder of pre-fire structural and topographic context. NDVI functions as a genuine early-recovery monitor, responsive to the living cover that determines erosion resistance, seedling establishment, and habitat recovery. RdNBR sits in between, its relativization making it sensitive to the residual organic layer that governs soil protection and hydrological response. Managers who read a single index map and draw conclusions about ecological damage or recovery may therefore be reading one channel of a multi-channel signal and mistaking it for the whole broadcast.

The study also demonstrates a practical field-reference workflow that could be adopted widely. By pairing systematic transect-based ground cover measurements with freely available Sentinel-2 imagery, the researchers show that the ecological meaning of spectral indices can be calibrated cheaply and repeatably, without exotic instrumentation. As Mediterranean-type regions face longer fire seasons and larger, more severe burns, as argued in recent calls for a paradigm shift in wildfire management, the demand for rapid, ecologically honest post-fire assessments will only grow. This study’s message is both a caution and a gift: the satellites are telling the truth, but each index tells a different truth, and only by grounding them in measured ground cover can fire ecologists decode which one they are hearing.

Subject of Research: Ecological interpretation of Sentinel-2 spectral indices for post-fire assessment in a Mediterranean Pinus brutia forest

Article Title: Linking transect-based field observations with Sentinel-2 indices to characterize post-fire conditions in a Mediterranean Pinus brutia forest

Article References: Malkoçoğlu, S., & Kahveci, E. (2026). Linking transect-based field observations with Sentinel-2 indices to characterize post-fire conditions in a Mediterranean Pinus brutia forest. Environmental Monitoring and Assessment, 198(11), 1207. https://doi.org/10.1007/s10661-026-16023-4

Image Credits: AI Generated

DOI: 10.1007/s10661-026-16023-4

Keywords: Sentinel-2, dNBR, RdNBR, NDVI, burn severity, wildfire, Pinus brutia, Mediterranean forests, transect sampling, ground cover, remote sensing, fire ecology

The research team, led by Mohamed El Mderssa of Sultan Moulay Slimane University together with colleagues from the National School of Forest Engineering and Moulay Ismail University, compared Ifrane National Park in the Middle Atlas with Talassemtane National Park in the Rif Mountains. These two parks form a natural experiment: Ifrane’s forests grow on a patchwork of basaltic volcanic rock and dolomitic carbonate, while Talassemtane sits almost entirely on limestone. Because both parks harbor similar numbers of forest ecosystem types, any divergence in their soil carbon profiles points toward geology and ecological differentiation rather than simple species counts.

The researchers assembled a harmonized dataset of 67 field observations collected during the summer of 2022, drawing on 48 sampling points in Ifrane and 19 in Talassemtane. All measurements targeted the upper 30 centimeters of mineral soil, a depth consistent with Intergovernmental Panel on Climate Change reporting guidance and one that captures the biologically active horizon where litter inputs, root exudates and fine-root turnover concentrate. Carbon concentrations were determined by Walkley–Black wet oxidation, and stocks were calculated using bulk density measured with the core method, ensuring that both datasets could be compared on identical footing.

The headline result is striking. Mean soil organic carbon stock reached 173.99 tonnes of carbon per hectare in Ifrane, roughly two and a half times the 69.44 tonnes per hectare recorded in Talassemtane. Welch’s t-test confirmed the difference was highly significant. Just as telling was the spread: individual values in Ifrane ranged from 36.10 to 437.92 tonnes per hectare, with a coefficient of variation of nearly 54 percent, while Talassemtane’s values spanned only 44.64 to 107.74 tonnes per hectare with a variation coefficient of just over 22 percent. In ecological terms, the Middle Atlas landscape behaves like a mosaic of carbon banks of very different sizes, whereas the Rif landscape stores carbon more uniformly and, on average, far less of it.

Forest ecosystem type significantly shaped these patterns in both parks. In Ifrane, zeen oak forests topped the table with a mean of 251.54 tonnes of carbon per hectare, followed by holm oak at 219.62 and cedar at 169.47. Mixed cedar–holm oak and holm oak–zeen oak stands, along with maritime pine plantations, stored considerably less. In Talassemtane, Mediterranean matorral showed the highest mean at 101.41 tonnes per hectare, ahead of cork oak and the endemic Moroccan fir, though the authors caution that matorral and fir were each represented by only two observations, making those means indicative rather than statistically robust. The spread between ecosystem means, a simple measure of carbon differentiation, was 142.52 tonnes per hectare in Ifrane against just 41.72 in Talassemtane.

Geology emerged as the study’s most provocative variable. Within Ifrane, soils derived from basalt averaged 200.84 tonnes of carbon per hectare, about 37 percent more than the 147.14 tonnes on dolomite. A general linear model identified geological substrate as the strongest determinant of soil carbon variability once ecosystem type was adjusted for, and a linear mixed-effects model estimated that limestone soils in Talassemtane hold roughly 139 tonnes per hectare less carbon than basaltic ones. The mechanistic explanation lies in soil chemistry: basalt weathers into clay-rich soils packed with reactive iron and aluminum oxides that bind organic matter into stable organo-mineral associations, shielding it from microbial decomposition, whereas calcareous and dolomitic substrates tend to produce shallower, sandier soils with weaker mineral protection.

Yet the authors are refreshingly careful not to oversell this geology story. Because four of Ifrane’s six ecosystem types occur exclusively on a single substrate, ecosystem identity and rock type are heavily entangled in the data. The cleanest available test comes from cedar and holm oak forests, the only ecosystems sampled on both basalt and dolomite. Within each of these, the basalt–dolomite difference was not statistically significant, with P values of 0.680 and 0.143 respectively. The holm oak comparison did show a large numerical gap, 264.7 against 174.5 tonnes per hectare, but with only six replicates per group the test was likely underpowered. The team explicitly frames the substrate effect as suggestive rather than confirmed, an unusually candid position that highlights how difficult it is to separate vegetation from parent material in real landscapes, echoing the classic pedological framework of soil formation in which climate, organisms, relief, parent material and time act inseparably.

Perhaps the study’s most conceptually important contribution is its redefinition of biodiversity. Instead of counting tree species within plots, the researchers treated forest ecosystem diversity as the diversity and spatial heterogeneity of ecosystem types across the landscape, integrating differences in vegetation structure, litter chemistry, rooting depth and microclimate. Both parks showed nearly identical richness and evenness indices for their sampled ecosystems, yet their carbon behavior diverged dramatically. This suggests that for carbon accounting purposes, biodiversity should be read as landscape heterogeneity rather than species richness, since what drives soil carbon is the patchwork of contrasting ecological engines, not the number of names on a plant list.

The practical implications ripple outward from Moroccan park boundaries. Carbon inventories that prioritize aboveground biomass while treating soil as a uniform black box risk mispricing these landscapes: a holm oak forest on basalt in Ifrane may hold more than four times the soil carbon of a holm oak forest on limestone in Talassemtane, even though the vegetation looks broadly similar. The authors argue that pedological information, including substrate type and mineralogy, should be built into national carbon accounting and that basalt-derived oak forests deserve priority in restoration and protection schemes as disproportionately valuable carbon reservoirs. At the same time, they caution against dismissing limestone ecosystems as low value, since they deliver unique biodiversity and hydrological services that carbon metrics alone cannot capture.

The team also lays out its own limitations with unusual transparency: uneven sampling between parks, the near-perfect confounding of substrate and ecosystem within Ifrane, the absence of climate, topographic and mineralogical covariates, and a 30-centimeter sampling depth that may underestimate total profile carbon in deeper soils. Future work, they suggest, should employ balanced designs in which the same ecosystem types are sampled across multiple substrates, and should extend to remote sensing and digital soil mapping for spatial prediction. For now, the message stands: if the world wants Mediterranean mountain forests to keep banking carbon, it must learn to read the rocks as carefully as it reads the trees.

Subject of Research: Soil organic carbon storage in Mediterranean mountain forests as shaped by forest ecosystem diversity and geological substrate in Morocco

Article Title: Soil organic carbon storage across Mediterranean mountain forests: a comparative assessment of forest ecosystem diversity and geological substrate in Ifrane and Talassemtane National Parks, Morocco

Article References: El Mderssa, M., ELMALKI, M., Malki, F., Abdelhakim, T., Abbas, Y., & Ibijbijen, J. (2026). Soil organic carbon storage across Mediterranean mountain forests: a comparative assessment of forest ecosystem diversity and geological substrate in Ifrane and Talassemtane National Parks, Morocco. Frontiers in Soil Science, 6, Article 1959268. https://doi.org/10.3389/fsoil.2026.1959268

Image Credits: AI Generated

DOI: 10.3389/fsoil.2026.1959268

Keywords: soil organic carbon, Mediterranean forests, Morocco, Ifrane National Park, Talassemtane National Park, geological substrate, basalt, limestone, carbon sequestration, forest ecosystems, Middle Atlas, Rif Mountains

The research focused on Yishi Forest in the Judean foothills, a hot Mediterranean site receiving about 510 millimeters of rain per year, where a thin soil layer of just 5 to 20 centimeters sits atop limestone bedrock. The team, led by Stav Livne-Luzon and Assaf Yaakobi under the supervision of Tamir Klein, compared plots dominated by three functionally distinct native species: the canopy conifer Pinus halepensis, the sub-canopy broadleaf Quercus calliprinos, and the understory woody shrub Pistacia lentiscus. Some plots contained only one dominant species, while others were mixed stands containing all three. Beneath every selected tree, and in the open gaps between canopies, the researchers collected soil from the top 10 centimeters, gathering 104 samples in total across the forest.

The central analytical move was to split soil organic carbon into two fractions with very different personalities. Mineral-associated organic carbon, or MAOC, consists of small organic molecules such as microbial necromass and root exudates that bind to clay and silt particles, shielding them from decomposition for periods that can stretch to millennia. Particulate organic carbon, or POC, is made of larger, tougher plant compounds like lignin and cellulose that resist chemical binding but remain exposed to microbial attack, turning over within decades. Globally, MAOC makes up roughly 65 percent of soil organic carbon, so understanding what controls each fraction is essential for any serious carbon accounting.

The results were unambiguous at the microsite scale. Soils under tree canopies held up to twice as much organic carbon as soils in nearby forest gaps, and Quercus plots stored 10 to 30 percent more carbon than either Pinus or Pistacia plots. Across the site, carbon concentrations ranged from 18.3 to 187.1 grams of carbon per kilogram of soil, with the highest values under oaks and the lowest in a gap within a mixed plot. When the researchers converted concentrations into stocks, accounting for the site’s shallow soils and abundant stones, mixed Quercus plots approached nearly 3 kilograms of carbon per square meter, compared with about 1 kilogram in monospecific gaps and Pistacia plots.

But the real story emerged when the fractions were separated. Trends in total soil carbon tracked the labile POC fraction almost entirely, and POC tended to be higher in mixed stands than in single-species ones. MAOC, by contrast, showed no significant differences among forest types or microsites, because it had effectively run out of room. The mineral-associated fraction displayed a classic saturation pattern, plateauing at around 45 grams of carbon per kilogram of soil, a figure closely matching saturation values of roughly 40 grams reported for European soils. At low-carbon sites, MAOC comprised nearly 80 percent of the soil carbon pool, but at the richest sites its share collapsed as POC came to account for more than 90 percent of the total.

What sets that ceiling? The answer, in this system, is mineralogy. MAOC increased linearly with clay and silt content across the plots, and a 95th-percentile regression yielded a site-specific carbon capacity of 50.3 grams of carbon per kilogram of clay plus silt. That value sits close to the 48 grams estimated for low-activity mineral soils globally, which fits the site’s carbonate-rich geology, since carbonate minerals are generally less reactive than the iron and aluminum oxides found in more volcanic soils. Notably, when the team applied the same calculation to a large dataset of dryland forests worldwide, the capacity came out substantially higher at 70.2 grams, suggesting that at Yishi Forest it is the minerals themselves, not the arid climate, that limit long-term carbon storage.

The microbial dimension of the study produced equally thought-provoking results. Using a high-resolution sequencing approach that targeted six variable regions of the 16S rRNA gene and enriched the reference database with full-length sequences from PacBio long-read sequencing, the team profiled bacterial communities across seasons and microsites. The sequencing revealed 1,531 amplicon sequence variants spanning 20 phyla, along with 413 novel full-length sequences representing bacteria absent from existing databases. Bacterial communities beneath tree canopies turned out to be subsets of the richer communities found in open gaps, implying that the altered soil conditions under trees act as an environmental filter, winnowing the microbial pool down to favored specialists.

Each tree species appeared to recruit its own microbial entourage. Soils under pines hosted proportionally more Proteobacteria, while oak soils were enriched in Firmicutes. Under pine canopies, genera such as Pseudolabrys, Bradyrhizobium, and Tardiphaga increased in abundance, while oak canopies favored Bradyrhizobium, Nocardioides, and a nitrosomonad genus, taxa associated with nitrogen fixation, nitrification, and the degradation of aromatic compounds. Intriguingly, however, neither bacterial richness nor diversity correlated consistently with any carbon pool, and microbial richness dropped out of the final structural equation model entirely. In this ecosystem, at least, the sheer number of microbial species matters less for carbon storage than the physical and chemical stage on which they perform.

That structural equation model, which explained 43 percent of the variation in MAOC and 66 percent in POC, painted a coherent picture of competing controls. Clay and silt content exerted the strongest direct effect on MAOC, while soil properties and microsite dominated POC, with a direct microsite effect hinting that belowground inputs such as root exudation and root turnover differ among species in ways aboveground litter alone cannot explain. Litter density showed a negative direct path to POC that was offset by a positive indirect route through soil properties, leaving no net effect. Taken together, the model confirms that labile and mineral-associated carbon pools answer to different masters.

The practical bottom line is quantified and sobering in equal measure. Mixed forests in this system were estimated to store approximately 6.1 megagrams of carbon per hectare more than monospecific pine stands, with the difference residing almost entirely in the fast-cycling POC pool, particularly where MAOC was already near saturation. As afforestation and forest management are promoted as leading natural climate solutions, the study suggests that planting diverse stands can meaningfully raise soil carbon stocks in dry regions, but that the durable, century-to-millennium fraction of that carbon is ultimately bounded by soil texture. In shallow, carbonate-rich Mediterranean soils approaching their mineralogical limits, the most reliable carbon gains from forest diversity may be real but transient, a finding that planners banking on soils as permanent carbon vaults would do well to heed.

Subject of Research: Tree species composition, microbial communities, and soil texture controls on particulate and mineral-associated soil organic carbon in Mediterranean forest soils

Article Title: Tree-microbe-soil interactions affecting soil organic carbon fractions in Mediterranean forest soils

Article References: Livne-Luzon, S., Yaakobi, A., Yalin, D., Sade, D., Dener, E., Oppenheimer-Shaanan, Y., & Klein, T. (2026). Tree-microbe-soil interactions affecting soil organic carbon fractions in Mediterranean forest soils. Biogeosciences, 23(18), 6763-6779. https://doi.org/10.5194/bg-23-6763-2026

Image Credits: AI Generated

DOI: 10.5194/bg-23-6763-2026

Keywords: soil organic carbon, Mediterranean forests, mineral-associated organic carbon, particulate organic carbon, tree diversity, mixed forests, soil microbiome, carbon sequestration, soil texture, carbon saturation, Pinus halepensis, Quercus calliprinos

The research team turned to MaxEnt, short for maximum entropy modelling, one of the most widely used tools in modern biogeography. The technique works by comparing the environmental conditions at locations where a species has been recorded with the conditions available across the whole study area, then estimating the probability of occurrence at every grid cell. Rather than requiring absence data, which is notoriously unreliable, MaxEnt builds a picture of a species’ ecological niche from presence records alone. For a country as topographically and climatically varied as Algeria, which spans Mediterranean coastline, high plateaus and the northern fringe of the Sahara, this approach is particularly powerful because it can capture the full breadth of conditions a species tolerates.

To drive the models, the researchers assembled occurrence records for both oak species, drawing on field knowledge and global biodiversity databases, and combined them with a suite of environmental predictor variables covering temperature, precipitation and terrain. Crucially, they projected the models forward using future climate scenarios for three time horizons, allowing them to track not just whether habitat will be lost or gained, but where the geography of suitability will shift. The performance of the models was assessed using the Area Under the Curve, or AUC, a standard statistical measure of discrimination. Values above roughly 0.8 are generally considered good, and above 0.9 excellent. Both oak models exceeded 0.96, a strikingly high score that indicates the models separated suitable from unsuitable terrain with near-perfect reliability.

The single most influential variable shaping the distribution of both species was the Martonne aridity index, a classic climatic measure that combines annual precipitation with mean temperature to express the degree of water availability across a landscape. Its dominance in the models makes ecological sense. Mediterranean oaks live at the dry edge of what trees can tolerate, and their growth, survival and regeneration are tightly governed by the balance between water arriving as rain and water lost to the atmosphere. In Algeria, where warming is outpacing the global average and droughts are becoming more frequent and severe, this finding underscores that aridity, not temperature alone, is the master variable controlling the fate of these forests.

When the researchers projected the models into the future, the two species told different stories. For cork oak, the annual rate of highly suitable habitat is expected to decline under every future scenario, with projected losses ranging from 0.040 percent to 0.191 percent per year. The numbers may look small, but compounded over decades they translate into a meaningful contraction of the species’ core range in Algeria. Cork oak is already under pressure across the western Mediterranean from land abandonment, overgrazing, fire and unexplained decline phenomena, so any additional climatic squeeze on its best habitat is cause for concern for foresters and conservationists alike.

Holm oak, by contrast, showed far greater stability. Its highly suitable habitat is projected to change only slightly, with shifts ranging from a loss of 0.021 percent to a gain of 0.164 percent per year depending on the scenario. This hardy evergreen is famously drought-tolerant, capable of surviving on thin soils and withstanding long summer dry seasons, and the model results reflect that toughness. In practical terms, the study suggests that holm oak could even hold its ground or modestly expand in some parts of Algeria as conditions change, making it a candidate species for stabilising forests in an increasingly arid landscape.

Perhaps the most vivid finding concerns elevation. The average elevation of suitable habitat is projected to shift under each climate scenario, ranging from 866 to 1,025 metres for cork oak and from 978 to 1,172.5 metres for holm oak. In other words, as the lowlands warm and dry, the climatic comfort zone for both species climbs the mountainsides, and holm oak consistently occupies higher ground than cork oak. This pattern echoes a well-documented global phenomenon in which mountain plant communities shift upslope in response to warming. The catch, as ecologists have repeatedly warned, is that mountains are cones: the higher a species climbs, the less land remains available, and slow-moving trees may lag far behind the pace of climate change.

The models also revealed a striking directional signature. Under most future scenarios, the highly suitable habitat for cork oak shifts towards the northeast of the country, while for holm oak it shifts towards the northwest. These compass bearings matter enormously for conservation planning. Northeastern Algeria, with the humid coastal ranges of Kabylia and El Kala, retains some of the wettest conditions in the country, and the projected northeastward drift of cork oak suitability suggests these areas will become increasingly critical refuges. The northwestward shift for holm oak points to a different set of priority landscapes, and the divergence between the two species means that a single, one-size-fits-all protected area network will not serve both trees equally well.

The practical value of this work lies in its maps. By identifying where habitat is highly suitable now and where it is likely to remain suitable through the end of the century, the study gives Algerian foresters a decision-support tool of real consequence. Rather than reacting to forest decline after it happens, managers can use these projections to prioritise which forest stands to protect, where to focus regeneration efforts, and which zones should be preserved as climate refugia. The authors emphasise that the maps are intended precisely for this purpose: helping foresters select the best conservation strategy for cork oak and holm oak and choose appropriate forest zones to be preserved before the climate window closes.

The study also sits within a growing body of Algerian research on climate-driven range shifts, including recent work on Atlas cedar, Aleppo pine, Phoenician juniper and the endemic oak Quercus afares, all pointing in a consistent direction: the country’s forest flora is being reshuffled by warming and drying. What makes the new findings compelling is the contrast between two closely related, sympatric oaks responding so differently to the same climatic pressures. As the Mediterranean basin warms faster than the global average, the fate of these forests will depend on whether conservation planning can anticipate the movement that the models now make visible. For Algeria’s cork and holm oaks, the future is not yet written, but the map of where it will unfold has finally been drawn.

Subject of Research: Species distribution modelling of cork oak and holm oak habitats in Algeria under climate change

Article Title: Modelling the current and future potential distributions of Quercus suber and Q. ilex (Fagaceae) in Algeria

Article References: Rais, H., Laala, A., Meghzili, I., Mennour, H., & Boucenna, H. (2026). Modelling the current and future potential distributions of Quercus suber and Q. ilex (Fagaceae) in Algeria. Plant Biosystems, 160(5), Article 239. https://doi.org/10.1007/s44473-026-00241-2

Image Credits: AI Generated

DOI: 10.1007/s44473-026-00241-2

Keywords: Quercus suber, Quercus ilex, Algeria, MaxEnt, species distribution modelling, climate change, aridity index, habitat suitability, Mediterranean forests, cork oak, holm oak, forest conservation

The team focused on three oak species that dominate the climax forests of acidic substrates across the peninsula: cork oak (Quercus suber), Pyrenean oak (Quercus pyrenaica) and pedunculate oak (Quercus robur). These species sit at different points along a moisture gradient. Pedunculate oak, a temperate and humidity-loving species, thrives in the cool Atlantic north. Pyrenean oak, a marcescent species that holds its withered leaves through winter, occupies a transitional submediterranean zone. Cork oak, the iconic evergreen of Mediterranean silviculture, tolerates pronounced summer drought. Because the three species often coexist in the same landscapes, distributed along gradients from rocky ridge tops to moist valley bottoms, the researchers reasoned that climate change could trigger a domino effect: as each species retreats from its drier margins, a more drought-adapted congener may move in to take its place.

To test this idea, the researchers built high-resolution species distribution models at a one-square-kilometre resolution, integrating nearly a quarter of a million cleaned occurrence records from GBIF, national biodiversity databases and expert-curated sources. For pedunculate oak, the team applied a spatial thinning procedure that reduced more than 205,000 records to about 27,000, mitigating oversampling while preserving the species’ environmental coverage. The models combined nineteen bioclimatic indices from the CHELSA dataset with soil pH, soil texture, a Topographic Ruggedness Index and a Topographic Wetness Index, all chosen through hypothesis-driven screening that excluded collinear predictors.

The modelling framework was an ensemble approach implemented in the biomod2 package in R, combining eight techniques ranging from generalized linear models and generalized additive models to random forests, artificial neural networks and maximum entropy. Each model was validated over ten rounds of cross-validation, and only algorithms exceeding a True Skill Statistic threshold of 0.7 were averaged into the final ensembles. Performance was strong across the board: TSS values exceeded 0.83 and AUC scores surpassed 0.97 for all three species, with cork oak models performing best. Future projections drew on five general circulation models selected for their strong performance over Europe, run under two Shared Socioeconomic Pathways: an intermediate SSP3-7.0 scenario and a pessimistic SSP5-8.5 scenario, for the mid-century period 2041 to 2070 and the late-century period 2071 to 2100.

The environmental variables that best explained each species’ current distribution revealed their distinct ecological thresholds. For pedunculate oak, the minimum temperature of the coldest month was the dominant predictor, reflecting its tolerance of subzero winters, followed by topographic ruggedness and precipitation of the warmest quarter. Pyrenean oak’s distribution hinged on annual precipitation and warm-season rainfall together with soil pH, underscoring its dependence on water availability during the hot, dry summer. Cork oak, by contrast, was governed primarily by soil pH and mean annual temperature, favouring sites where winter minima stay above freezing. All three species are strictly silicicole, confined to acidic substrates, which means that climatically suitable areas on limestone soils will remain off-limits no matter how the climate shifts.

The projected trajectories diverge sharply. Pedunculate oak’s current range is expected to remain largely stable, with between 73 and 84 percent of its present suitable area persisting across scenarios, though its total suitable area declines slightly as losses outweigh gains. Cork oak emerges as the clear winner: its suitable range expands in every scenario and time frame, gaining between 32 and 44 percent of new territory, pushing northward and inland, with potential altitudinal advances reaching as far as the Pyrenees, while losing almost nothing at its southern edge. Pyrenean oak fares worst. Its total suitable area shrinks in all scenarios, with losses of up to nearly 60 percent of its current range concentrated in the southern and inland parts of the peninsula, and only limited compensatory gains at higher elevations.

When the researchers overlaid the range dynamics of different species, the turnover patterns became strikingly clear. Wherever one species loses suitability while another gains or holds steady in the same grid cells, a potential replacement is flagged. The dominant signal is a turnover from Pyrenean oak to cork oak, projected across roughly 20 to 47 percent of Pyrenean oak’s currently suitable range depending on the scenario, intensifying toward the end of the century and under harsher emissions. This replacement is expected to begin at the species’ southern fringes and spread into the interior. A smaller turnover, from pedunculate oak to Pyrenean oak, is projected across about 5 to 8 percent of the former’s range, mostly in low-altitude inland areas at the southern edge of its distribution. In some coastal zones of western and northeastern Iberia, cork oak may ultimately replace both of the other species where they both become unsuitable.

A crucial dimension of the study is its analysis of protected areas. Between a quarter and nearly half of the projected turnover zones fall inside classified conservation sites, including Natura 2000 areas designated under the European Union’s Habitats Directive, national parks and nature reserves. The turnover from Pyrenean oak to cork oak carries a direct policy consequence: it implies a shift from habitat 9230, the Galicio-Portuguese oak woods, to habitat 9330, cork oak forests, within sites whose management plans were written for the habitats of the past. The researchers argue that conservation targets in these sites will need periodic revision to maintain habitat continuity under changing climates, and that protected areas can serve as demonstration cases for adaptive management on the privately owned lands that dominate the Portuguese landscape.

The authors are careful to frame these projections as shifts in potential climatic and edaphic suitability rather than deterministic predictions of stand-level replacement. The models do not explicitly simulate dispersal, disturbance regimes or biotic interactions, and oak species are notoriously slow to migrate relative to the pace of climate change. Yet the convergent trends across multiple climate models and scenarios lend weight to the central inference: that a gradual Mediterraneanization of the Iberian landscape is underway, marked by longer summer dry periods and reduced annual precipitation, in which drought-adapted oaks progressively occupy the space vacated by their moisture-dependent relatives.

The practical implications reach deep into forestry. The researchers recommend protecting natural regeneration of the species likely to dominate in the future, since cork oak individuals already occur near Pyrenean oak stands on rocky outcrops and within forests. Where natural regeneration is insufficient, they point to seed sowing and planting techniques, including autumn sowing to maximize root development before summer drought, selection of larger acorns, protection from seed predators such as wild boar, and the use of large containers to avoid root deformation. They also advocate multi-provenance strategies that draw reproductive material from southern or low-altitude populations already adapted to drier conditions, combined with mixed-species stands to hedge risk. If guided by such adaptive management, the authors conclude, species turnover need not spell the loss of Iberian forests; it may instead be the mechanism by which they retain canopy cover, ecological function and resilience through a century of rapid environmental change.

Subject of Research: Projected climate-driven species turnover among Iberian oak forests

Article Title: Exploring turnover dynamics in Iberian Oak forests under climate change scenarios

Article References: Passos, I., Figueiredo, A., Gonçalves, J., Ribeiro, M. M., & Vila-Viçosa, C. (2026). Exploring turnover dynamics in Iberian Oak forests under climate change scenarios. Discover Conservation, 3(1), Article 14. https://doi.org/10.1007/s44353-026-00084-0

Image Credits: AI Generated

DOI: 10.1007/s44353-026-00084-0

Keywords: climate change, oak forests, Quercus suber, Quercus pyrenaica, Quercus robur, species distribution models, species turnover, Iberian Peninsula, Mediterranean forests, forest management, conservation, habitat suitability

The Atlas cedar, Cedrus atlantica, is an emblematic conifer endemic to the Atlas Mountains of Morocco and Algeria, growing between roughly 1,300 and 2,200 meters on well-drained limestone and siliceous soils. It is a keystone species that regulates watershed soils and local climate, supports biodiversity, and carries deep cultural and economic value through its durable, aromatic timber. Yet the species has been in serious decline for decades. Dendroecological records across Morocco and Algeria show multi-decadal growth losses and rising drought sensitivity since the late twentieth century, driven by intensifying drought, heat stress, and warming-facilitated biotic attacks such as pine processionary moth outbreaks. The International Union for Conservation of Nature now classifies the species as endangered, and Algeria’s natural cedar forests have been reduced to small, fragmented relicts in the high mountains.

Chelia National Park, centered on Mount Chelia at 2,328 meters, contains one of the largest remaining cedar stands in the country, but even here recent surveys have documented drought-induced dieback alongside human pressures including overgrazing and illegal logging. While regional modeling studies have projected significant range contractions for Atlas cedar across North Africa, and Moroccan analyses have predicted habitat losses of 21 to 41 percent by 2070 depending on emissions, comparable local-scale analyses for Algeria have been lacking. Conservation planning in Chelia had not previously incorporated model-based climate projections, leaving managers without a quantitative picture of the park’s climatic future.

To fill that gap, the research team, led by Hichem Chenaker and Rami Khoucha of the Higher National School of Forests in Khenchela with colleagues from Iraq and Egypt, compiled 107 unique occurrence points from field GPS surveys conducted between 2022 and 2026 and from official park vegetation maps. To avoid pseudo-replication, the team assigned a single presence point to each mapped cedar stand rather than populating large polygons with many points, a design that also enforced natural spacing between records. The study area spans a Mediterranean montane climate in which most precipitation falls in winter, roughly 110 millimeters in January, while summers are extremely dry with only about 10 millimeters in July, and mean annual temperature falls from around 10 degrees Celsius at low elevations to near freezing at the highest peaks.

The researchers modeled habitat suitability with MaxEnt version 3.4.4, deliberately calibrating the model only within the park boundary to align its inference space with local management needs. Environmental predictors were assembled at one-kilometer resolution from WorldClim bioclimatic variables and NASADEM elevation data, then filtered for multicollinearity using a Pearson correlation threshold of 0.7 and a variance inflation factor cutoff of five. The final predictor set included mean diurnal range, isothermality, temperature seasonality, minimum temperature of the coldest month, temperatures of the wettest and driest quarters, precipitation of the driest month, precipitation seasonality, and elevation. Model performance was evaluated with ten-fold cross-validation, achieving an AUC of 0.83, a reasonable score given the restricted environmental gradients of the park, and transferability to future climates was checked with clamping and multivariate environmental similarity surface, or MESS, analyses.

Future projections drew on the WorldClim v2.1 CMIP6 multi-model ensemble, which averages bias-corrected outputs from eight major global climate models, under two emissions pathways: the intermediate SSP2-4.5 and the high-end SSP5-8.5, for the 2050 and 2070 time windows. The team applied a single 10th-percentile training presence threshold across all projections to keep the maps comparable, and classified the continuous suitability output into four classes. Under present-day conditions, only about 10.5 percent of the park’s 326 square kilometers, or 34.2 square kilometers, qualifies as highly suitable, nearly all of it in the high-elevation core southeast of the Chelia summit. Roughly 18 percent is moderately suitable, 7 percent weakly suitable, and the remaining 64 percent is already unsuitable, meaning the cedar is confined to narrow microclimates even today.

The future looks starker. Under the moderate SSP2-4.5 scenario, highly suitable habitat declines to about 8.9 percent of the park by 2050 and 7.9 percent by 2070, while unsuitable area expands to 66.3 percent, a net loss of nearly a quarter of the current prime habitat within half a century. Under the high-emission SSP5-8.5 pathway, losses arrive faster, with unsuitable conditions covering more than 67 percent of the park by 2070 and the remaining high-quality patches few, isolated, and concentrated in the east-central highlands near the highest peaks. MESS analysis showed that future climates in the high-elevation core remained within the range of the training data under all scenarios, while novel climates appeared only in low-elevation peripheries that are already unsuitable, lending confidence to the projections for the areas that matter most. Because the model was calibrated only within the park, the authors caution that these figures are conservative estimates of habitat loss.

One of the study’s most important contributions is its careful interpretation of why winter cold emerged as the dominant predictor. The minimum temperature of the coldest month, BIO6, accounted for more than 60 percent of the model’s explanatory power, followed by elevation at 17.8 percent and precipitation seasonality at 10.5 percent. Rather than reading this as a simple preference for cold, the authors interpret BIO6 as a proxy for elevation-linked humidity, snow persistence, and reduced summer water deficit. In Supramediterranean mountain systems, altitude and terrain features such as north-facing slopes and shaded ravines function as microrefugia by buffering heat load and vapor pressure deficit, so the coolest sites are frequently the moistest sites. Field observations support this: cedar stands cluster in cool, shaded topographic positions while lower slopes and ridgelines are largely cedar-free. As warming proceeds, the model suggests that precipitation seasonality and warm-season temperatures gain weight, pointing to intensifying summer drought as the central constraint on persistence. The authors also note that biological interactions, such as pest outbreaks, can act as ultimate drivers of local extinction in marginal cedar populations, guarding against an overly climate-deterministic reading.

The findings align with regional evidence from Morocco and Algeria, where modeling and tree-ring studies consistently show Atlas cedar tracking more humid conditions and suffering under warming and aridification, and with similar patterns in other Mediterranean montane conifers such as Spanish fir and European black pine. For Chelia, the authors propose an adaptive conservation strategy that goes beyond temperature-based upslope relocation: protecting high-elevation microrefugia, restoring habitat connectivity, assisted enrichment planting within refugial sites, seed banking and genetic conservation, and managing local stressors such as overgrazing, illegal logging, and fire. Critically, they argue that hydrological buffering deserves explicit attention, since riparian corridors, spring-fed slopes, and areas with shallow groundwater access act as natural drought refuges. The projected 25 percent contraction of highly suitable habitat by 2070, even under a low-emissions pathway, speaks directly to Sustainable Development Goal targets on climate action and life on land. The team acknowledges limitations, including niche truncation from local calibration, the absence of soil and disturbance data, and coarse climate inputs, and recommends future work with ensemble models, hierarchical regional-local approaches, finer downscaling, and quantitative fragmentation metrics to refine the outlook for Algeria’s vanishing cedars.

Subject of Research: Modeling current and future climate-driven habitat suitability of the endangered Atlas cedar in Chelia National Park, Algeria

Article Title: Climate resilience of Atlas cedar: habitat suitability modeling for climate action and life on land

Article References: Chenaker, H., Khoucha, R., Al-Quraishi, A. M. F., Atalla, M. A., & Bedair, H. (2026). Climate resilience of Atlas cedar: habitat suitability modeling for climate action and life on land. Discover Ecology, 2(1), Article 14. https://doi.org/10.1007/s44396-026-00032-1

Image Credits: AI Generated

DOI: 10.1007/s44396-026-00032-1

Keywords: Atlas cedar, Cedrus atlantica, species distribution modeling, MaxEnt, climate change, Chelia National Park, habitat fragmentation, microrefugia, CMIP6, conservation planning, Mediterranean forests, Algeria

The research, published in Plant Biosystems by a team led by Andrea Coppi and Federico Selvi of the University of Florence together with colleagues from Camerino, Sassari, Basilicata and Palermo, tackled a long-standing question in plant biogeography and evolutionary ecology: do endemic species differ from widespread congeners in the range and patterns of their functional trait variation and genetic structure? While many studies have examined the genetics of rare plants, little is known about how intraspecific variation in functional traits relates to genetic variation in narrow Mediterranean forest endemics, particularly when compared against close relatives occupying similar habitats.

The two species form an ideal natural experiment. Aegonychon calabrum is confined to a few mountain localities in Calabria and one outlier population in Campania, growing in mixed holm oak-broadleaf or Calabrian pine forests up to 1400 meters above sea level. Aegonychon purpurocaeruleum, by contrast, ranges across most of southern Europe eastwards to Iran and is found throughout most of Italy. Both are perennial hemicryptophytic herbs of the forest understory with similar growth habits, showy blue or purple flowers pollinated by long-tongued insects, and the ability to spread vegetatively through creeping sterile stems. Both are diploid, though with different chromosome numbers, and no hybrids are known between them, indicating effective reproductive barriers.

The researchers sampled three populations of the endemic and seven populations of the widespread species, the latter spanning the entire latitudinal gradient of Italy from Lake Garda in the north to Sicily in the south. At each site, leaves were collected from ten fully developed individuals spaced at least ten meters apart to avoid sampling clones of the same plant. Two leaves per individual were used for trait measurements and a third was dried in silica gel for genetic analysis. The team measured three core leaf traits: leaf area, specific leaf area, and leaf dry matter content, which together convey key information about how plants acquire and conserve resources.

The trait results told a nuanced story. Leaf area was significantly lower in the endemic species, supporting the idea that A. calabrum has a more resource-conservative strategy than its widespread relative, consistent with a recent broader study of Mediterranean forest endemics. However, and unexpectedly, the overall amount of intraspecific variation in the three traits was comparable between the species, and in some cases even slightly wider in the endemic, despite the fact that the widespread species was sampled across a far broader range of climatic conditions. Within the endemic, the southern high-elevation population on siliceous substrate showed more resource-acquisitive traits, while the two northern populations on warm calcareous sites exhibited smaller leaves and lower specific leaf area, traits associated with tolerance of drought and nutrient limitation.

When the researchers translated the leaf measurements into Grime’s CSR ecological strategies, which describe trade-offs between competitive ability, stress tolerance and ruderality, they found that species identity explained almost none of the variation. Instead, population effects accounted for between 52 and 81 percent of the variation in the three strategy scores. The endemic’s populations ranged from predominantly stress-tolerant to ruderal, mirroring the spread seen in the widespread species. This lack of clear divergence in ecological strategies suggests that A. calabrum fits the so-called refuge model of endemism, in which narrow distribution reflects stress tolerance and low competitive ability in marginal habitats, rather than the specialist model, in which rarity stems from tight adaptation to a narrowly defined environment.

The genetic analysis, based on AFLP fingerprinting of 94 individuals producing 181 loci, delivered perhaps the most surprising findings. Analysis of molecular variance showed that the vast majority of genetic variation occurs within populations in both species, and mean expected heterozygosity was only slightly lower in the endemic (0.295 versus 0.311). This runs counter to the common expectation that rare, fragmented species suffer genetic erosion. Differentiation among populations was actually lower in the endemic than in the widespread species, and a discriminant analysis of principal components confirmed a clear genetic separation between the two species, with the endemic defined almost exclusively by two unique genetic clusters. Only about five percent of loci were flagged as candidates under selection, pointing to a similarly low impact of adaptive divergence at the genome level in both species.

The pivotal insight came from comparing phenotypic differentiation among populations with neutral genetic differentiation. In both species, phenotypic differentiation in leaf traits substantially exceeded genetic differentiation, a pattern indicating that directional or divergent selection, rather than random genetic drift, is shaping population differences in leaf form and function. The magnitude of the gap between the two measures was far greater than averages reported in meta-analyses of plant populations, reinforcing the conclusion that selection is a powerful force in both the rare and the common species. The authors note that this result held even under conservative assumptions about the additive genetic basis of the traits, making the signature of selection difficult to dismiss as a methodological artifact.

The study also probed whether genetically similar populations share similar trait values, a population-level version of niche conservatism. A significant positive correlation between trait similarity and genetic proximity emerged only for leaf area, and a local autocorrelation analysis revealed that the two northern populations of the endemic, which occupy similar habitats, form a clade with significantly similar trait values. This pattern suggests that shared ancestry and limited environmental divergence, rather than random processes alone, help maintain trait similarity among genetically close populations, even as other forces push populations apart phenotypically.

Taken together, the findings paint the rare Aegonychon calabrum as anything but an evolutionary dead end. Its populations combine substantial genetic diversity, considerable phenotypic plasticity and evidence of ongoing selection, suggesting a real capacity to adapt to changing habitat conditions. For conservation biologists, the message is that narrow range does not necessarily mean genetic fragility, and that Mediterranean forest endemics may harbor hidden adaptive potential. The authors call for future work using genome-wide sequencing approaches such as ddRADseq and genome-wide association studies to characterize genomic variation in endemic and widespread species pairs more comprehensively, opening the way to a deeper understanding of how rarity and adaptability coexist in the plant world.

Subject of Research: Leaf trait variation, genetic structure and selection in a narrow Mediterranean forest endemic plant compared with its widespread congener

Article Title: Are leaf traits and genetic differentiation patterns divergent in endemic vs widespread congeneric plant species? Insights from the Mediterranean forest species pair Aegonychon calabrum-A. purpurocaeruleum (Boraginaceae)

Article References: Coppi, A., Santini, G., Canullo, R., Carrari, E., Chelli, S., Farris, E., Gasperini, C., Rosati, L., Santi, I., Bajona, E., Campetella, G., & Selvi, F. (2026). Are leaf traits and genetic differentiation patterns divergent in endemic vs widespread congeneric plant species? Insights from the Mediterranean forest species pair Aegonychon calabrum-A. purpurocaeruleum (Boraginaceae). Plant Biosystems, 160(5), Article 252. https://doi.org/10.1007/s44473-026-00254-x

Image Credits: AI Generated

DOI: 10.1007/s44473-026-00254-x

Keywords: Aegonychon calabrum, plant endemism, leaf traits, AFLP fingerprinting, genetic diversity, Mediterranean forests, niche conservatism, PST-FST comparison, CSR strategies, population genetics, directional selection, understory herbs