The research, led by Meribeni Tsopoe and Kambam Boxen Meetei of the ICFRE-Rain Forest Research Institute in Jorhat, together with Krishna Giri and Rajiv Pandey of the Indian Council of Forestry Research and Education in Dehradun, focused on four Angami villages in Kohima district: Khonoma, Mima, Viswema, and Jotsoma. These communities practice sophisticated agroforestry systems, including the celebrated alder-based jhum cultivation of Khonoma, in which the nitrogen-fixing Himalayan alder is managed alongside crops in a rotational cycle that sustains soil fertility without external inputs. The team applied the Intergovernmental Panel on Climate Change vulnerability framework, integrating both socio-economic and ecological dimensions into a single assessment, an approach the authors argue fills a significant gap in the literature on indigenous farming systems in the region.

The IPCC framework conceptualizes vulnerability as a function of three interacting components: exposure to climatic stresses, sensitivity of the system to those stresses, and adaptive capacity, meaning the ability of a community to anticipate, cope with, and recover from impacts. Translating this into measurable indicators, the researchers combined qualitative and quantitative datasets gathered through household surveys and environmental sampling. Socio-demographic factors such as income, education, and livelihood diversity were weighed alongside ecological variables including soil health, carbon stocks, and biodiversity. The result was a Climate Vulnerability Index for each village, a single composite score that allows direct comparison across the landscape.

The rankings revealed striking contrasts between neighboring communities. Viswema emerged as the most vulnerable village, with an index value of 0.293, followed closely by Jotsoma at 0.278. Mima recorded 0.270, while Khonoma, the famed home of alder-based jhum, proved the least vulnerable at 0.268. The differences, though numerically small, are meaningful: the study attributes Khonoma’s and Mima’s relative resilience to higher adaptive capacity, whereas Viswema and Jotsoma face greater exposure to climatic hazards combined with fewer resources to respond. In other words, vulnerability in these hills is not simply a matter of where the rain falls hardest, but of what a community can do when it does.

Underlying these scores is a deeper ecological story. The study demonstrated that agroforestry systems actively enhance ecological resilience by improving soil fertility, increasing carbon sequestration, and supporting biodiversity. The alder trees that anchor Khonoma’s farming landscape fix atmospheric nitrogen through symbiotic bacteria, enriching the soil for the crops grown beneath them, a natural fertilization process documented in earlier work that identified indigenous free-living diazotrophs in the system. Deep root systems stabilize slopes against erosion, while the multi-layered canopy mimics forest structure, providing habitat for a wide range of species. These are precisely the ecosystem functions that conventional intensive agriculture tends to erode.

One of the study’s most commercially and politically significant findings concerns the relationship between the Climate Vulnerability Index and per capita income. The analysis showed that villages with higher per capita income exhibited lower vulnerability and greater economic stability, suggesting that economic diversification acts as a form of insurance against climatic uncertainty. Households that can draw on multiple income streams, whether from integrated farming, forest products, or off-farm employment, are better positioned to absorb losses when harvests fail. This echoes a growing body of research from across the Himalayas showing that livelihood diversification is among the most reliable predictors of household resilience in mountain communities.

The timing of this research could hardly be more critical. The Eastern Himalayas are recognized as one of the world’s major biodiversity hotspots, yet they are warming faster than many lowland regions, and rainfall patterns across Nagaland have shown significant trends in recent decades. Regional assessments, including India’s national 4×4 climate assessment and the Nagaland State Action Plan on Climate Change, have flagged the state’s predominantly agrarian and forest-dependent communities as acutely exposed. For smallholder farmers practicing subsistence agriculture on steep terrain, even modest shifts in the timing of monsoon rains can cascade into food insecurity, making the identification of low-vulnerability models a matter of survival rather than academic interest.

What makes the Angami case especially compelling is the explicit link the researchers draw between ecosystem services and adaptive capacity. Rather than treating ecology and economics as separate domains, the study argues that the services flowing from well-managed agroforestry, fertile soils, stored carbon, biodiversity, and water regulation, are themselves components of a community’s capacity to adapt. This integrated framing carries implications well beyond Nagaland. Globally, agroforestry is increasingly promoted as a nature-based solution to climate change, capable of delivering both mitigation through carbon storage and adaptation through reduced sensitivity of farming systems. The Angami experience offers a living, functioning proof of concept refined over generations.

The authors emphasize that their results argue for village-specific policies rather than one-size-fits-all interventions. Because Viswema and Jotsoma face different combinations of exposure and capacity deficits than Khonoma and Mima, adaptation strategies must be tailored accordingly. The study points to three priorities: sustainable ecological management that maintains the health of agroforestry landscapes, the formal integration of traditional knowledge into climate adaptation planning, and economic diversification that broadens household livelihoods. Such targeted approaches, the researchers suggest, could serve as a template for future research on resilient agroecosystems throughout the Himalayan arc and similar mountain regions worldwide.

For a world searching for climate solutions that work at the scale of real communities, the message from the hills of Kohima is quietly radical. The most resilient farming systems in the study were not those with the most modern infrastructure, but those where ecological knowledge accumulated over centuries continues to govern the relationship between people and land. As funding for the work came from India’s Department of Science and Technology, and as the researchers acknowledge the participating farming communities whose information made the study possible, the findings stand as both a scientific validation and a tribute. If the world’s mountain farmers are to weather the coming decades, the Angami agroecological systems of Nagaland may well be one of the blueprints worth studying, and protecting, now.

Subject of Research: Climate vulnerability and resilience of indigenous Angami agroforestry systems in Nagaland, Northeast India

Article Title: Climate change vulnerability, ecological resilience, and adaptive capacity of Angami agroecological systems in Kohima, Nagland, Northeast India

Article References: Tsopoe, M., Meetei, K. B., Giri, K., & Pandey, R. (2026). Climate change vulnerability, ecological resilience, and adaptive capacity of Angami agroecological systems in Kohima, Nagland, Northeast India. Environmental Monitoring and Assessment, 198(10), Article 1096. https://doi.org/10.1007/s10661-026-15940-8

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15940-8

Keywords: climate change vulnerability, agroforestry, Angami, Nagaland, Eastern Himalayas, adaptive capacity, ecological resilience, ecosystem services, indigenous knowledge, jhum cultivation, Climate Vulnerability Index, smallholder farmers

The survey covered four Community Reserved Forests, or CRFs, spanning tropical, sub-tropical, temperate, and montane forest types along a gradient running from about 900 to 2500 meters. These forests are not government parks; they are guarded by villages under customary law, which makes them both ecologically precious and administratively fragile. Across eighty systematically sampled quadrats, the researchers recorded 237 vascular plant species from 87 genera and 84 families, including 102 trees, 53 shrubs, and 82 herbs. That single district inventory accounts for approximately 9.71 percent of Nagaland’s entire known flora, a striking figure for a landscape that had never before been floristically documented in a structured way.

The fieldwork, conducted from 2023 to 2025, was designed to strip away confounding variables. Each forest received one permanent one-hectare plot, positioned to match comparable slope, aspect, and stand maturity, and each plot was gridded into twenty-five quadrats of which twenty were sampled. Within those quadrats, nested subplots of decreasing size captured trees with diameters at breast height of at least ten centimeters, shrubs, and herbs. Sampling ran across four seasons to capture the temporal pulse of the vegetation, and every specimen was identified with reference floras and authenticated against the collections of the Botanical Survey of India in Shillong. Voucher specimens now reside in the herbarium of Nagaland University’s Department of Forestry.

What emerged from the data was a pattern that contradicts the classical textbook picture. For much of the twentieth century, ecologists assumed that species richness simply fell as one climbed a mountain, a monotonic decline driven by the increasing harshness of the environment. Modern studies have increasingly documented instead a unimodal, or hump-shaped, distribution, with richness peaking at mid-elevations where the ranges of tropical and temperate taxa overlap and where energy and moisture are both abundant. In Phek, the temperate zone turned out to be exactly such a sweet spot, harboring the highest richness of the entire gradient, while diversity dropped off toward both the hot lowlands and the cold montane summits.

The mechanisms behind that peak proved to be as much about soil as about sky. Soil organic carbon, measured across three depth strata using the Walkley and Black method, showed a strong positive relationship with species richness, apparently because carbon-rich soils hold water better and buffer moisture through dry spells on steep, runoff-prone slopes. Sites with higher soil carbon maintained more stable moisture levels, supporting diverse herbaceous and epiphytic communities, including eleven species of orchids and other epiphytes. Meanwhile, the regression and stepwise analyses pinpointed a sharp ecological breakpoint: when mean annual precipitation exceeded 122.9 millimeters, richness increased markedly, a result statistically significant at p less than 0.001. Below that threshold, moisture availability strictly constrained which plants could persist.

To move beyond correlation, the team deployed a hierarchical statistical arsenal. Linear mixed-effects models, selected by the Akaike Information Criterion, quantified the influence of climatic and edaphic variables while accounting for repeated sampling years. Structural equation modeling then disentangled direct and indirect causal pathways, revealing, for example, that soil pH exerted a positive effect on richness in tropical and montane zones largely by mediating nutrient availability, and that temperature seasonality acted as a direct negative force, filtering out species unable to tolerate strong seasonal thermal swings. Species distribution models built with MaxEnt mapped these relationships onto the landscape, confirming that the temperate zone hosts the highest predicted richness.

Perhaps the most consequential finding concerns how communities change with elevation, not how many species they contain. Using Baselga’s partitioning of beta diversity, the researchers separated community dissimilarity into two components: species turnover, the wholesale replacement of species from one site to another, and nestedness, the progressive loss of species from species-rich sites to species-poor ones. Turnover overwhelmingly dominated, accounting for roughly 73 to 75 percent of total beta diversity across all four forest types, with remarkably consistent values of 73.6 percent in montane forests, 74.6 percent in temperate forests, 73.7 percent in sub-tropical forests, and 73.6 percent in tropical forests. Nestedness clustered near zero.

That result carries a profound implication: as one ascends the mountain, plant communities are not simply shedding species like a diminishing subset of the lowland flora. Instead, each elevational band hosts an essentially distinct assemblage, assembled by niche-based environmental filtering. The dominant species tell the story vividly. Montane forests are characterized by Saurauia montana and Euonymus attenuatus; temperate forests by the oaks Quercus griffithii and Quercus lamellosa; sub-tropical forests by Croton persimilis and Adenanthera pavonina; and tropical forests by Dysoxylum cauliflorum and Micromelum integerrimum. Mean elevations of tree assemblages declined in a clean staircase from about 2301 meters in montane forest to 1033 meters in tropical forest, underscoring how tightly vegetation is zoned along the gradient.

The conservation stakes are considerable. Roughly 39 percent of the documented species are endemic, and several carry alarming IUCN statuses, including the critically endangered Aquilaria malaccensis and Adinandra griffithii in the tropical forests. Yet the forests that harbor this diversity face mounting pressure: between 2002 and 2023, Phek District lost 1.56 thousand hectares of humid primary forest, and shifting jhum cultivation, timber extraction, and unregulated water diversion continue under village jurisdictions where enforcement varies widely. Because each forest type maintains a unique floristic identity driven by high turnover, losing any single elevational band would erase species found nowhere else along the gradient, a risk that richness maps alone would badly underestimate.

The authors argue that the path forward runs through the communities themselves. With little formal government involvement, the CRFs persist entirely under village stewardship, making local governance the decisive force in conservation outcomes. They call for stronger legal recognition of community forest rights, the integration of traditional ecological knowledge with science-based monitoring, and long-term, performance-based financial incentives for villages that protect their forests. The 122.9-millimeter precipitation threshold and the soil carbon relationship also offer a predictive framework: as climate change alters rainfall regimes across the Eastern Himalaya, the study’s baselines allow researchers to forecast which elevational zones and which communities are most likely to unravel first, and where conservation investment can buy the greatest protection for one of the planet’s great biodiversity hotspots.

Subject of Research: Elevational patterns of vascular plant species richness and turnover in the Eastern Himalayan biodiversity hotspot

Article Title: Elevational decline of vascular plant richness and distinct species turnover driven by soil carbon and precipitation in the Eastern Himalayan hotspot

Article References: Koza, V.-O., Pegu, J., & Yam, G. (2026). Elevational decline of vascular plant richness and distinct species turnover driven by soil carbon and precipitation in the Eastern Himalayan hotspot. Discover Plants, 3(1), Article 440. https://doi.org/10.1007/s44372-026-00899-0

Image Credits: AI Generated

DOI: 10.1007/s44372-026-00899-0

Keywords: Eastern Himalaya, species richness, elevational gradient, soil organic carbon, precipitation threshold, species turnover, beta diversity, biodiversity hotspot, community reserved forests, Nagaland, plant ecology, conservation

The research, led by Prabhakar Sharma and Gyanendra Nath Tiwari, surveyed 226 residents across three Nagaland districts, Kohima, Dimapur, and Chümoukedima, spanning urban, semi-urban, and rural settings. The team anchored their work in the Theory of Planned Behaviour, a widely used psychological framework holding that behaviour flows from three conscious drivers: attitude toward the act, perceived social pressure from others, and perceived behavioural control, the sense that one is able to carry out the behaviour. To this classic trio the researchers added measures of cultural values and perceptions of policy and governance, and they paired the survey with open-ended questions and ten in-depth interviews to capture what residents themselves saw as the real obstacles.

The quantitative results were striking in their asymmetry. Respondents scored highest on items measuring environmental concern and personal responsibility: agreement that plastic waste harms the environment averaged 4.77 on a five-point scale, that reducing plastic use is necessary averaged 4.58, and that one feels personally responsible for proper disposal averaged 4.38. Yet the subscale measuring perceived behavioural control, covering access to disposal points, confidence in segregating waste at home, and the availability of affordable alternatives, was the weakest of all, averaging just 2.97. In other words, people knew the problem was real and felt it was theirs to solve, but they did not feel equipped to act.

When the researchers ran a hierarchical multiple regression to see which constructs actually predicted self-reported waste-management behaviour, the pattern upended expectations. Subjective norms, the perception of what neighbours, friends, and the community expect and practice, emerged as by far the strongest predictor, with a standardized coefficient of 0.485. Cultural values contributed next, at 0.251, followed by attitude at 0.186. Perceived behavioural control, the variable that classical theory often casts as decisive, contributed essentially nothing once the other factors were accounted for, with a coefficient of negative 0.023 and a p-value of 0.661. Although control showed a small bivariate correlation with behaviour, that association was entirely absorbed by its overlap with subjective norms. The final model explained 44.5 percent of the variance in self-reported practice.

Just as telling was what did not matter. Adding residents’ perceptions of policy and governance, whether the plastic ban was enforced, whether government was managing waste efficiently, whether public information was adequate, improved the model by exactly nothing, a change in explained variance of zero with a p-value of 0.908. Residents clearly viewed enforcement as weak: agreement that the plastic ban was strictly enforced averaged only 2.85, and belief in efficient government management averaged 2.88. But those dim views of the state did not independently predict what people actually did with their plastic. The machinery of governance, in this setting, appears to shape behaviour only indirectly, if at all.

The qualitative strand of the study filled in the human texture behind these numbers. Among roughly 131 open-ended survey responses, the most frequently cited barrier to proper disposal was lack of awareness and education, named by 67 percent, followed by inadequate infrastructure and facilities at 58 percent and weak enforcement at 32 percent. In the separate interview sample, infrastructure deficits and the absence of plastic-specific traditional beliefs were rated as very high intensity themes, raised unprompted by eight or more of the ten participants. One interviewee captured a widespread mindset bluntly: people consider all waste equal, so everything belongs in the same bin. Traditional Naga practices, built around biodegradable materials and low-waste living, simply never developed categories for a plastic-dominated waste stream.

When the researchers integrated the two strands of evidence, the most revealing result was a divergence rather than an agreement. Infrastructure was overwhelmingly salient in how residents talked about the problem, yet individually perceived control carried no unique statistical weight in the regression. The authors propose, cautiously, that infrastructure may operate less as a direct constraint on individual action and more as a structural condition that shapes community norms and expectations, so that where collection points are absent, responsible disposal simply never becomes a shared local standard. That mediational hypothesis could not be tested with the study’s cross-sectional design, but it offers a concrete target for future longitudinal research.

The theoretical implications extend beyond Nagaland. The Theory of Planned Behaviour is a deliberative-reasoning model, assuming that people weigh attitudes and consequences before acting. A growing literature argues that everyday waste disposal is often habitual, cued by routine and context rather than conscious reflection, and the survey instrument used here was not designed to detect such automatic processes. The authors also flag social-desirability bias as a risk, since normatively loaded items about responsibility and cleanliness may inflate self-reports, and they acknowledge that the attitude and cultural values subscales showed weak internal consistency, with Cronbach’s alpha values of 0.35 and 0.46 respectively, well below conventional thresholds. The cultural values finding, they stress, should be read as a promising but tentative extension rather than an established determinant, particularly because exploratory factor analysis showed some of its items blending into the subjective norms factor.

For policy, the practical message is unambiguous. Awareness campaigns alone are unlikely to close the gap between what people believe and what they do, because belief is not the binding constraint. Instead, the authors argue, interventions should centre community-based and norm-oriented strategies, enlisting the village councils, religious organisations, and youth groups that already function as trusted arbiters of local expectation. Respondents themselves pointed in the same direction: awareness and education campaigns were the most frequently proposed solution, cited by 72 percent of open-ended respondents and 90 percent of interviewees, followed by better infrastructure at 53 and 70 percent respectively, and stricter enforcement at 38 and 60 percent. Ideas such as plastic buy-back schemes, subsidies for reusable alternatives, and regular community clean-up days surfaced repeatedly.

The study has clear limits. Its sample, recruited through stratified quotas combined with convenience sampling, skewed young and male, with roughly half of respondents under 25, and all behaviour measures were self-reported rather than validated against observed practice or objective infrastructure audits. The cross-sectional design forbids causal claims, and two exploratory moderation tests, whether residential area or cultural values changed the strength of other predictors, failed to reach significance. Still, the core result stands as a genuinely useful contribution: in a collectivist, community-governed society, the strongest lever for changing plastic behaviour is not the individual conscience but the collective gaze. If Nagaland’s village councils and youth groups begin treating segregation as a shared expectation rather than a private virtue, the plastic choking its urban slopes may finally have somewhere to go other than the open fire.

Subject of Research: Psychosocial and cultural determinants of plastic waste management behaviour in Nagaland, India

Article Title: Psychosocial, cultural, and structural determinants of plastic waste management practices in Nagaland, India: A mixed-methods study using the theory of planned behaviour

Article References: Sharma, P., & Tiwari, G. N. (2026). Psychosocial, cultural, and structural determinants of plastic waste management practices in Nagaland, India: A mixed-methods study using the theory of planned behaviour. Environmental and Sustainability Indicators, 32, Article 101539. https://doi.org/10.1016/j.indic.2026.101539

Image Credits: AI Generated

DOI: 10.1016/j.indic.2026.101539

Keywords: plastic waste, Nagaland, theory of planned behaviour, subjective norms, waste management, mixed methods, environmental psychology, cultural values, India, recycling, community governance, developing countries

The research team, led by Anannya Panging of Mizoram University together with colleagues from institutions across India, focused on the Dikhow River Basin, a drainage system covering roughly 3,971 square kilometres. The river rises near Zunheboto peak in Nagaland and flows north through Assam before joining the Brahmaputra, its basin spanning steep mountainous country in the south and flat alluvial plains in the north. Geologically, the upper basin is built from the Disang, Barail and Tipam groups of Eocene to Miocene age, dominated by sandstones, shales and clays, materials that are notoriously fragile when saturated by the region’s intense monsoonal rainfall. Nagaland falls within Zone V, the highest category, of India’s landslide hazard zonation map, yet no previous study had ever assessed landslide susceptibility across this basin.

To build their maps, the researchers compiled an inventory of 632 landslides identified from Google Earth imagery, then split the records into a training set of 442 points and a testing set of 190 points in a 70:30 ratio. They paired this inventory with twelve landslide conditioning factors: slope, aspect, elevation, rainfall, lithology, lineament density, distance to streams, the Normalized Difference Vegetation Index, the Topographic Wetness Index, land use and land cover, the Stream Power Index, and curvature. Each factor was derived from publicly available data, including the Shuttle Radar Topography Mission digital elevation model, Geological Survey of India lithological records, gridded rainfall data from 2003 to 2021, and 10-metre land cover imagery. All layers were resampled to a common 30-metre resolution and projected into a single coordinate system before analysis.

The two competing techniques were the Frequency Ratio model and the Index of Entropy model, both bivariate statistical approaches that quantify the association between past landslide locations and each class of each conditioning factor. The Frequency Ratio method is elegantly simple: for every class of every factor, it calculates the ratio of the proportion of landslide pixels to the proportion of the total area. A value above one signals a positive correlation with landsliding, below one a negative one. The Index of Entropy, by contrast, borrows Shannon’s information theory to assign weights that account for the uncertainty, or disorder, in the distribution of landslides across factor classes, producing a more elaborate weighting scheme. Both models are prized for their transparency and their ability to reveal threshold values, an advantage over black-box machine learning approaches when the goal is to explain why certain slopes fail.

Before running the models, the team checked for multicollinearity among the twelve factors using the Variance Inflation Factor and Tolerance statistics. Values ranged from 1.059 to 2.024 for VIF and 0.494 to 0.944 for Tolerance, well within acceptable limits, confirming that no factor was redundant and all twelve could legitimately enter the analysis. The relative importance of the factors then diverged between the models in an instructive way. In the Frequency Ratio framework, land use and land cover emerged as the single most influential factor, followed by slope, lithology and the Topographic Wetness Index. The Index of Entropy instead gave top weighting to the Topographic Wetness Index, with slope and land cover nearly tied at around 0.34. The discrepancy reflects the different mathematical machinery behind the two methods and hints that landslides here are not driven by any single cause but by interacting combinations of terrain, geology, hydrology and human activity.

The spatial patterns the models uncovered are striking. Landslides clustered in intermediate elevations between roughly 329 and 1,589 metres, on steep slopes where frequency ratios climbed as high as 3.19 in the steepest class of 35 to 71 degrees. Concave slopes, which accumulate water and raise pore pressure, showed a frequency ratio of 1.71, while carbonaceous sandy shale proved the most dangerous lithology with a ratio of 2.13, its moderate permeability and the chemical weathering of carbonate making it especially unstable. Counterintuitively, some of the lowest rainfall zones showed the strongest landslide associations, likely because those areas combine high lineament density, low vegetation cover and steep terrain, while the wettest zones sit largely on the stable plains of Assam. Built-up areas and rangeland, where human slope modification strips away protective vegetation, both showed positive associations with landsliding, underscoring the growing role of anthropogenic pressure on the region’s slopes.

When the two susceptibility maps were assembled and classified into five zones from very low to very high using natural-break classification, the differences between the models became vivid. The Frequency Ratio model flagged 19.9 percent of the basin as very highly susceptible and another 34.1 percent as highly susceptible, whereas the Index of Entropy assigned only 8.4 percent to the very high class and 22.7 percent to the high class. In both maps, the danger zones concentrated in the southern, south-eastern and south-western portions of the basin, particularly the steep uplands of Nagaland, with the districts of Tuensang, Mon and Longleng bearing the brunt. The northern, downstream plains registered low to very low susceptibility in both models, a reassuring result for the densely settled valley areas near the Brahmaputra confluence.

Validation separated the two contenders decisively. Using the area under the receiver operating characteristic curve, the gold-standard measure of predictive skill, the Frequency Ratio model scored 0.81 on the training data and 0.82 on the testing data, both firmly in the very good range. The Index of Entropy achieved 0.79 and 0.80 respectively, respectable but consistently a step behind. A second validation metric, the relative landslide density or R-index, told the same story: 64.81 percent of recorded landslides fell within the very high susceptibility zone of the Frequency Ratio map, compared with 60.25 percent for the entropy map, and landslide density rose steadily from low to high classes in both, confirming that the maps captured real spatial structure rather than statistical noise. The researchers attribute the entropy model’s slight underperformance to the narrow range of its factor weights in a basin where landslides respond to complex, interacting conditions rather than any single dominant trigger.

The practical implications extend well beyond academic comparison. The very high and high susceptibility zones identified by the Frequency Ratio map cover the upper Dikhow basin, precisely where road connectivity has repeatedly been severed and where landslides have claimed lives and destroyed property. The authors position the maps as a preliminary screening tool for hazard management and early warning systems, one that government agencies, policymakers and land-use planners can use to prioritise slope stabilisation, regulate construction on fragile hillsides and route infrastructure away from the most dangerous terrain. The method itself, built entirely from freely available satellite and government data, is transferable to other data-scarce mountainous regions facing similar monsoon-driven slope failures.

The study is candid about its limits. Seismic factors were excluded because ground data were unavailable, despite the region’s tectonic activity along features such as the Naga Thrust, and the temporal and spatial resolution of remote sensing data constrains the precision of any inventory-based mapping. The authors call for site-specific geotechnical investigation as the next step and point toward physics-informed machine learning and transfer learning techniques, which can carry knowledge from data-rich regions into data-poor ones, as the future of susceptibility modelling in the Northeast. For now, though, the message from the Dikhow basin is clear: sometimes the simplest statistical tool, applied carefully to good data, beats its more sophisticated rivals, and in doing so can hand a vulnerable region its first real map of where the earth is most likely to move.

Subject of Research: Comparative GIS-based landslide susceptibility mapping of the Dikhow River Basin using frequency ratio and index of entropy statistical models

Article Title: Comparative evaluation of frequency ratio and index of entropy models for landslides susceptibility mapping of Dikhow river basin, Northeast India

Article References: Comparative evaluation of frequency ratio and index of entropy models for landslides susceptibility mapping of Dikhow river basin, Northeast India. (n.d.). https://doi.org/10.1007/s44288-026-00737-6

Image Credits: AI Generated

DOI: 10.1007/s44288-026-00737-6

Keywords: landslide susceptibility mapping, frequency ratio, index of entropy, Dikhow River Basin, Nagaland, Northeast India, GIS, bivariate statistical models, natural hazards, monsoon rainfall, slope instability, ROC-AUC validation

The research team, led by K. Chiezou of the Geological Survey of India with colleagues from Assam University Silchar and North-Eastern Hill University Shillong, focused on a roughly 70-square-kilometre area in and around the Upper Tiru Valley in Mon district, within the Belt of Schuppen. This belt, a striking morphotectonic unit of northeast-southwest trending imbricate thrust sheets along the western flank of Nagaland, preserves sedimentary successions ranging from the Oligocene to the Quaternary. The Barail Group hosted within it is widely celebrated as a prolific hydrocarbon-bearing unit of the Upper Assam Petroliferous Basin, making any fresh insight into its composition and origin of direct economic as well as scientific interest.

The Tikak Parbat Formation itself is a visually distinctive succession. It alternates thin to thickly bedded, fine to medium-grained sandstones, which display cross-stratification and ripple lamination, with dark grey to black carbonaceous shales and coal seams. The formation is divided into two units: a lower intercalated shale-sandstone sequence between 120 and 215 metres thick, and an upper unit of alternating sandstone, shale and coal. Preserved sedimentary structures, including small-scale channels, lenticular bedding, scour-and-fill features and slumped layers, record a dynamic depositional environment in which sediment was repeatedly reworked, dried, flooded and destabilised.

To interrogate these rocks, the team collected 40 representative samples from the Tiru Valley and prepared thin sections from 39 of them. Using the Gazzi-Dickinson point-counting method, they tallied between 350 and 400 grains per slide to quantify modal mineralogy. Scanning electron microscopy on gold-coated samples at North-Eastern Hill University revealed delicate clay textures invisible to optical microscopy. Twenty of the least-altered samples were then crushed, ground and analysed for major oxides by X-ray fluorescence spectroscopy at the Geological Survey of India in Shillong, providing the chemical backbone for the study’s paleoenvironmental reconstructions.

The petrographic verdict was unambiguous. Quartz dominates the framework of the Tikak Parbat sandstones at roughly 45 percent of total grains, mostly as subangular to subrounded monocrystalline varieties, while rock fragments of igneous, sedimentary and metamorphic origin make up nearly 30 percent. Feldspar, at just under 6 percent, is more commonly potassium-rich than sodic, and many grains show alteration to sericite and clay. With an average recalculated modal composition of Q56 F7 R37, the sandstones classify as lithic arenite to lithic wacke, a composition that immediately hints at derivation from a recycled orogenic source rather than a freshly eroded volcanic arc.

Equally revealing is what the microscopy shows about the rocks’ post-depositional transformation. Mica flakes are kink-bent and ductile rock fragments have squeezed into pseudomatrix, hallmarks of intense mechanical compaction. Quartz cement occurs as syntaxial overgrowths around detrital grains, and iron oxide coats pore walls in reddish-brown films. Under the electron microscope, the team identified authigenic smectite and illite, including mixed-layer illite-smectite intergrowths in which illite nucleates directly on smectite flakes. Because smectite becomes unstable at burial temperatures above roughly 70 to 90 degrees Celsius and converts to illite in the presence of potassium released by dissolving K-feldspar, these textures indicate that the sandstones experienced moderate to deep burial diagenesis or contact with relatively hot pore fluids. Feldspar dissolution, meanwhile, generated secondary porosity, a process of keen interest to petroleum geologists because such pores can host hydrocarbons.

The geochemistry sharpened the picture further. Silicon dioxide ranges from about 49 to 82 weight percent, averaging 69 percent, while alumina averages 15.4 percent. Notably, sodium oxide is consistently lower than potassium oxide, matching the petrographic observation that K-feldspar outnumbers plagioclase, and reflecting the breakdown of unstable minerals during weathering and transport. Weathering indices tell a dramatic tale: the Chemical Index of Alteration averages 86.6 with values up to 89.1, the Chemical Index of Weathering averages 93.4, and the Plagioclase Index of Alteration averages an extraordinary 97.85, close to the theoretical maximum that signifies completely weathered material. On A-CN-K and A-K-C-N ternary diagrams, the samples cluster tightly near the alumina apex, confirming severe depletion of calcium, sodium and potassium in the source terrain.

These indices collectively portray source rocks stripped by intense chemical weathering under a semi-arid to semi-humid climate, conditions that produced chemically mature sediments before they ever reached the basin. The index of chemical variability points to high compositional maturity as well. Discriminant function analysis and SiO2 versus K2O/Na2O plots converge on a single tectonic interpretation: the Tikak Parbat sediments accumulated on a passive continental margin, a setting analogous to an Atlantic-type margin where thick sediment prisms build along trailing edges of continents far from active plate boundaries. Provenance diagrams place the sediment squarely in the recycled orogen field, with subordinate inputs from mixed and transitional continental sources.

The source of all this sediment is the most geologically satisfying part of the story. Trace-mineral evidence, including recycled zoned zircons and abraded quartz overgrowths that survived an earlier sedimentary cycle, alongside the dominance of metamorphic lithic fragments, points to sediment recycled from orogenic belts. The authors identify the flanking collisional systems, the Indo-Burmese or Indo-Myanmar Ranges and the Himalayas, as the principal contributors, with the bulk of the detritus derived from felsic rocks of granitic to rhyolitic composition. An aluminum oxide versus titanium dioxide plot reinforces this, showing low titanium-to-aluminum ratios characteristic of felsic crustal sources, with only a minor mafic, possibly basaltic, contribution.

What makes the study more than an academic exercise is its relevance to energy exploration and to the tectonic history of one of the most complex collision zones on Earth. Previous work had indicated that subsurface Barail sandstones differ significantly from their exposed counterparts in parts of the Belt of Schuppen, so characterising the outcropping rocks fills a genuine gap in regional knowledge. By demonstrating that the Oligocene Tikak Parbat sediments were intensely weathered, compositionally mature, recycled from collisional highlands and deposited on a passive margin that was later overprinted by thrusting, the study provides a calibrated baseline for reservoir prediction, for reconstructing the rise of the Himalaya and its neighbouring ranges, and for understanding how a quiet Atlantic-style continental edge was ultimately crumpled into the imbricate thrust sheets that give the Belt of Schuppen its name. In a handful of sandstones from a Nagaland valley, the rocks have preserved the full arc of that transformation, from placid margin to mountain front.

Subject of Research: Petrology and geochemistry of the Oligocene Tikak Parbat Formation sandstones in the Belt of Schuppen, Nagaland, Northeast India, constraining provenance, paleoweathering and tectonic setting

Article Title: Petrological and geochemical studies of Tikak Parbat Formation, Barail Group in parts of Belt of Schuppen, Nagaland, Northeast India

Article References: Petrological and geochemical studies of Tikak Parbat Formation, Barail Group in parts of Belt of Schuppen, Nagaland, Northeast India. (n.d.). https://doi.org/10.1007/s44288-026-00748-3

Image Credits: AI Generated

DOI: 10.1007/s44288-026-00748-3

Keywords: Tikak Parbat Formation, Barail Group, Belt of Schuppen, Nagaland, Northeast India, sandstone petrography, geochemistry, provenance, paleoweathering, passive continental margin, diagenesis, Oligocene