Soil respiration — the flux of carbon dioxide from the soil surface to the atmosphere — is one of the largest single pathways by which carbon leaves terrestrial ecosystems. It is the combined breath of two underground worlds: autotrophic respiration from living plant roots and their rhizosphere partners, and heterotrophic respiration from microbes and soil fauna decomposing dead organic matter. Because forest soils hold more carbon than the atmosphere and all vegetation combined, even modest shifts in this efflux can tip an ecosystem between acting as a carbon sink and a carbon source. That is precisely why the researchers, Madhab Chandra Behera and Uttam Kumar Sahoo, spent months measuring it in situ across nine sites spanning three reserve forests.

The study focused on three moist deciduous forest types shaped by the dominance of sal (Shorea robusta): pure sal forest, sal-dominated mixed forest, and mixed deciduous forest without sal. The team established 72 tree subplots across 7.2 hectares, quantified stand structure, litter production and fine-root turnover, and graded each site on a disturbance index that accounted for proximity to settlements, grazing, fire, fuelwood removal and the proportion of tree basal area felled. Soil respiration itself was measured with the soda-lime absorption technique: sealed chambers containing oven-dried sodium hydroxide granules were left on the forest floor for 24 hours, and the weight gain of the granules — corrected with a blank chamber and a stoichiometric factor — yielded the daily carbon dioxide efflux.

To separate root respiration from microbial respiration, the researchers used the trenching method. Beside each measurement point they dug trenches to 45 centimetres, severing root ingrowth, then let the soil settle for four weeks before measuring again. The difference between total respiration in untrenched soil and respiration in root-free soil gave the heterotrophic component. This partitioning matters because the two components respond differently to climate and disturbance: root respiration tracks the vitality and carbon allocation of living trees, while microbial respiration tracks the decomposition of soil organic matter — the process that permanently releases carbon that may have been stored for decades.

The seasonal signal was unmistakable. Soil respiration climbed to its annual maximum between July and September, coinciding with the southwest monsoon that delivers roughly 80 percent of the region’s 152 to 160 centimetres of annual rainfall, and fell to its minimum in the dry winter months. In the sal-dominated mixed forest, daily efflux peaked at 2.98 grams per square centimetre per day in September, then dropped to just 0.16 grams in February. The explanation lies in the physiology of the rhizosphere: monsoon moisture stimulates root growth and the exudation of sugars, amino acids and organic acids from roots, which in turn fuels rhizosphere microbes, while also improving nutrient diffusion through the soil. In the hot, dry pre-monsoon months, by contrast, desiccated soil constrains both microbial enzymes and root metabolism, so rising temperature alone cannot lift respiration.

Forest composition left its own fingerprint. Mixed forest without sal showed the highest mean respiration at 1.14 grams per square centimetre per day, followed by the sal-dominated mixed forest at 1.03, with pure sal forest trailing at 0.66. Annual carbon efflux ranged from 28.80 megagrams of carbon per hectare per year in pure sal forest to 49.83 in the sal-free mixed stand. Across all types, root respiration contributed slightly more than half of the total — 52.37 percent on average — meaning that living roots, not just decaying matter, dominate the carbon exit route from these soils.

Perhaps the most striking result concerns how long carbon stays locked in the ground. By dividing the soil organic carbon stock by annual heterotrophic respiration, the team calculated the mean residence time of carbon in the surface 15 centimetres. Pure sal forest held the most soil organic carbon — 2.11 percent, with a stock of 42.70 megagrams per hectare — and the longest residence time, 37.08 years. The mixed forest without sal held barely a fifth as much carbon, at 20.16 megagrams per hectare, and turned it over in just 10.84 years. In other words, the mixed forests respire more and store less, cycling carbon rapidly through a labile pool, while pure sal stands accumulate chemically resistant or physically protected organic matter that resists decomposition.

Statistical analysis sharpened the picture. Soil respiration correlated positively with soil moisture (r = 0.790) and tree density (r = 0.789), and negatively with soil temperature (r = −0.813) — a counterintuitive negative temperature relationship that the authors attribute to seasonal co-variation: the hottest months are also the driest, so moisture, not warmth, is the binding constraint. Principal component analysis placed soil moisture, tree density, basal area and litter production together on the first axis, which explained 62.50 percent of total variance, while soil temperature and the disturbance index loaded on the second. Multiple regression models built on soil temperature, moisture and tree density explained up to 78.5 percent of respiration variation in individual forest types, with soil moisture consistently carrying the strongest coefficient. The authors are careful to note that with only nine independent sites, the regression is explanatory rather than predictive, and that correlation and ordination cannot by themselves establish causation.

The disturbance story is subtler than the title of the study might suggest. Disturbance itself showed only weak, non-significant direct correlations with respiration, and its influence appears to be indirect — mediated through canopy openness, altered microclimate and shifts in organic matter inputs, as reflected in its loading on the second principal component alongside temperature. What disturbance and composition clearly do change is carbon turnover: faster cycling in diverse, more open mixed stands, slower and more stabilising cycling under closed sal canopy. For managers in the Eastern Ghats, the practical implication is that preserving structurally diverse, minimally disturbed sal stands protects the region’s largest soil carbon reservoirs, while monsoon-dependent moisture regimes — increasingly vulnerable to climate variability — set the tempo of carbon loss. As warming intensifies, the fate of these forests may hinge less on how hot they get and more on whether the rains on which their underground carbon economy depends remain reliable.

Subject of Research: Soil respiration and carbon turnover in disturbed tropical sal forests of the Eastern Ghats, India

Article Title: Impact of disturbance on spatio-temporal dynamics of carbon dioxide efflux on forest floor in tropical sal forests of the Eastern Ghats

Article References: Behera, M. C., & Sahoo, U. K. (2026). Impact of disturbance on spatio-temporal dynamics of carbon dioxide efflux on forest floor in tropical sal forests of the Eastern Ghats. Discover Forests, 2(1), Article 76. https://doi.org/10.1007/s44415-026-00139-z

Image Credits: AI Generated

DOI: 10.1007/s44415-026-00139-z

Keywords: soil respiration, carbon dioxide efflux, sal forests, Eastern Ghats, soil organic carbon, monsoon, forest disturbance, autotrophic respiration, heterotrophic respiration, carbon turnover, Shorea robusta, tropical forests

The research, led by Binayak Poudel of the Institute of Forestry at Tribhuvan University, together with colleagues in Canada and Nepal, quantified both vegetation carbon and soil organic carbon across three dominant forest types: Shorea robusta (sal), Pinus roxburghii (chir pine), and mixed broadleaved forests. Working in two community forests in Kaski District—the 162-hectare Sityum Kasyari and Simsar Patleswara Jukepani Community Forest and the 14-hectare Banpale Community Forest—the team established nineteen nested circular plots of 500 square meters each, measuring every tree with a diameter at breast height of at least five centimeters. Soil samples were collected from four depth intervals reaching down to 80 centimeters, with five subsamples composited at each depth to smooth out local heterogeneity.

The results were striking. Shorea robusta forests emerged as the undisputed carbon champions, storing 113.5 plus or minus 7.1 megagrams of carbon per hectare in vegetation and 102.0 plus or minus 2.3 megagrams per hectare in soil—substantially more than chir pine forests, which held 96.5 and 85.5 megagrams respectively, and far ahead of mixed broadleaved forests at just 64.2 and 84.9 megagrams. Together, the sal forests banked roughly 215 megagrams of carbon per hectare across vegetation and soil combined, placing them at the upper end of the range reported for South Asian subtropical forests.

But the real analytical payoff came from teasing apart why these differences exist. The researchers evaluated fourteen predictors spanning stand structure, anthropogenic disturbance, soil properties, topography, and climate, using Pearson correlation analysis and principal component analysis to identify the dominant drivers. For tree carbon, two structural variables towered above the rest: basal area, with a correlation coefficient of 0.641, and canopy cover, at 0.635, both highly significant. Tree height and stem density, by contrast, showed only weak, non-significant positive relationships—a reminder that a forest crowded with small stems stores far less carbon than one anchored by a few massive trunks.

Equally important was what the analysis revealed about human pressure. The team constructed an Anthropogenic Disturbance Index combining stem cutting, leaf litter collection, lopping intensity, and fire influence, each weighted equally. This index correlated negatively with tree carbon at r equals minus 0.60, a statistically significant signal that where people extract biomass, carbon stocks suffer. Mixed broadleaved forests, which local communities depend on most heavily for fuelwood and cattle fodder, showed the highest disturbance levels and the lowest carbon stocks. Chir pine forests, whose needles are unsuitable for composting or fodder, experienced the least disturbance.

Soil organic carbon told a different story entirely. Here, the strongest correlate was not a property of the trees but a property of the ground itself: soil texture. Silt content correlated positively with SOC at r equals 0.587, while sand content showed a significant negative correlation at r equals minus 0.581. This pattern reflects a well-established mechanism in soil science—fine mineral particles form stable organo-mineral complexes that physically shield organic matter from microbial decomposition, whereas sandy soils, with poor aggregate structure and low water retention, accelerate mineralization. Canopy cover was the only structural variable significantly associated with soil carbon, at r equals 0.560, suggesting that dense canopies moderate soil temperature and moisture in ways that favor organic matter accumulation.

Principal component analysis confirmed this division of labor. For tree carbon, the first two principal components explained 53.2 percent of total variance, with carbon clustering alongside basal area, canopy cover, and stem density. For soil carbon, the first two components accounted for 52.8 percent of variation, dominated by textural and site variables. Permutational multivariate analysis of variance showed that forest type explained 45 to 46 percent of the variation in both pools—statistically significant for each. Intriguingly, elevation correlated negatively with soil carbon while aspect correlated positively with tree carbon, and mean annual temperature showed a positive relationship with SOC that the authors attribute to the co-distribution of warmer, more productive lower-elevation sal forests rather than a direct climatic effect.

The comparison with earlier Nepalese and Himalayan studies adds valuable context. Previous work in Makawanpur district reported sal forest biomass as high as 313.69 megagrams per hectare in well-managed community forests, while degraded stands in Dang district stored barely 99 megagrams. Protected-area studies in Shuklaphanta National Park found core-zone carbon stocks of 258.56 megagrams per hectare versus 193.3 in buffer zones—a protected-area effect that mirrors the disturbance gradient documented in the new study. The authors also note that Nepal’s total forest topsoil SOC has been estimated at 494 million tons, a figure that local-scale studies like this one help refine for national inventories.

The study is candid about its limitations. Nineteen plots distributed unevenly across three forest types constrain statistical power, and the geographic scope of two community forests in a single district limits extrapolation. The analysis relies on correlation and PCA, which identify associations without establishing causality, and the disturbance index applies equal weights to pressures that likely differ in carbon impact. Climate data at 1-kilometer resolution from WorldClim varied too little across plots to serve as strong predictors, and the fieldwork captured only a single post-monsoon season. The authors recommend denser plot networks, structural equation modeling, soil carbon fractionation, and longer observation windows in future work.

Yet the management implications are clear and actionable. Because basal area, canopy cover, and disturbance intensity are readily measurable in routine forest inventories, they can be embedded directly into community forest operational plans and carbon monitoring frameworks. Protecting large-diameter trees, maintaining canopy closure, and strictly regulating cutting, lopping, litter removal, and fire emerge as the highest-leverage interventions for maximizing ecosystem carbon. For Nepal’s REDD+ program and national carbon accounting, the message is that structural integrity—rather than forest type alone—should anchor carbon-oriented planning in the country’s community forests, which cover nearly 45 percent of the national land area and represent one of the developing world’s most celebrated conservation success stories.

Subject of Research: Carbon storage drivers in Nepalese mid-hill community forests

Article Title: Stand structure drives vegetation carbon storage while soil texture regulates soil organic carbon in Nepalese mid-hill community forests

Article References: Poudel, B., Bhattarai, S., Koirala, S., Chapagain, J., & Timilsina, S. (2026). Stand structure drives vegetation carbon storage while soil texture regulates soil organic carbon in Nepalese mid-hill community forests. Discover Forests, 2(1), Article 69. https://doi.org/10.1007/s44415-026-00130-8

Image Credits: AI Generated

DOI: 10.1007/s44415-026-00130-8

Keywords: forest carbon, soil organic carbon, stand structure, basal area, canopy cover, Shorea robusta, anthropogenic disturbance, soil texture, community forestry, Nepal, REDD+, carbon stocks

Researchers from Sambalpur University, Terracon Ecotech, and the Government of Odisha set out to quantify litterfall production, standing litter biomass, decomposition rates, and nutrient fluxes in four sacred forests across the region: Andhari, Dedungri, Medha, and Papanga. Three of the sites are dominated by sal (Shorea robusta), while Papanga is dominated by Cleistanthus collinus. The forests lie within a tropical savanna climate zone, where annual rainfall ranges from 900 to 1,400 millimeters, almost all of it delivered during the June-to-September monsoon, and where pre-monsoon temperatures can exceed 45 degrees Celsius. That pronounced seasonality shapes nearly everything that happens on the forest floor.

Between January and December 2023, the team measured litter inputs monthly using one-square-meter collection pits established at least ten meters inside each forest boundary to avoid edge effects. The collected material was separated into leaves, twigs, branches, and miscellaneous fragments, then oven-dried and weighed. Annual litterfall ranged from 8.59 megagrams per hectare per year at Andhari to 11.32 megagrams per hectare per year at Medha, figures that sit comfortably within the global range for tropical forests and actually exceed values reported for several other tropical dry deciduous forests in India. Leaves dominated the mix, contributing between 80.65 and 83.35 percent of total litterfall, followed by twigs, branches, and other material.

The seasonal signal was unmistakable. Litter production peaked in March at all four sites, coinciding with the height of the dry season, when water stress triggers leaf senescence and abscission in deciduous trees. Statistical analysis confirmed that month-to-month variation within sites was highly significant, while differences among the four forests were not. In other words, climate and phenology, not site identity, are the primary engines driving litterfall in these ecosystems. Standing litter biomass followed the same rhythm, accumulating to a maximum in March and dwindling to a minimum during the rainy and post-rainy months of August through November, with annual means ranging from 2.39 megagrams per hectare at Andhari to 2.68 at Medha.

The speed at which that litter disappeared was the study’s most striking finding. Using the classic litterbag technique, the researchers placed 20-gram samples of mixed-species fresh leaf litter, collected during the February-March peak litterfall period, into 20-by-20-centimeter nylon bags with one-millimeter mesh and laid them on the forest floor in a completely randomized design. Six bags were retrieved from each site every month. Roughly 95 percent of the initial litter mass had vanished within six months at every site. The fitted decay constants ranged from 5.75 to 6.65 per year, corresponding to half-lives of just 38 to 44 days. Model-based extrapolation suggested that 99 percent decomposition would be achieved within 274 to 318 days, although the authors caution that these figures extend beyond the six-month observation window.

Litter turnover rates told a similar story. The ratio of annual litterfall to standing litter biomass, a standard index of how quickly organic matter cycles through the forest floor, ranged from 3.59 to 4.22 per year, equivalent to residence times of only 87 to 102 days. Those turnover rates are higher than values reported for tropical semi-deciduous, tropical dry evergreen, and tropical evergreen forests, indicating that these small sacred groves process organic matter unusually fast. The researchers attribute the rapid decay to favorable temperature and moisture conditions during the decomposition period, which stimulate microbial activity, possibly combined with relatively high litter nutrient quality.

That quality question was addressed through chemical analysis of the mixed-species litter. Initial concentrations of nitrogen, phosphorus, and potassium differed significantly among the four forests, with Papanga showing the highest nutrient levels and the most favorable stoichiometric profile. Correlation analyses revealed that initial nitrogen and phosphorus concentrations were significantly associated with decomposition rates, while carbon content was not. The authors note an important caveat: lignin and cellulose, structural compounds that strongly regulate decomposability, were not measured, so the full biochemical picture of litter quality in these forests remains incomplete.

Nutrient release during decomposition followed a clear hierarchy: potassium was lost fastest, followed by nitrogen, then phosphorus. Potassium, highly soluble and prone to leaching, declined rapidly throughout the experiment, with release reaching 98.72 to 99.20 percent across the sites. Nitrogen loss ranged from 92.26 to 95.08 percent, and phosphorus from 80.54 to 95.34 percent after six months. Papanga recorded the highest total nutrient loss at 96.57 percent. Meanwhile, nitrogen and phosphorus concentrations actually increased in the residual litter, a pattern the researchers attribute to microbial immobilization, in which decomposer organisms accumulate these nutrients in their own biomass before releasing them back to the soil. Carbon concentrations remained relatively stable at Andhari and Medha but declined at Dedungri and Papanga.

The study’s authors are candid about its limitations. There were no non-sacred control forests for direct comparison, so the work characterizes variation within sacred forests rather than testing the effects of sacred-forest protection itself. Repeated temporal observations were not analyzed with mixed-effects models, and the correlation results should be read as associations rather than causal claims. Still, the baseline data fill a genuine gap: while litterfall and nutrient cycling have been extensively documented in tropical evergreen forests and, to a lesser degree, in sacred groves elsewhere in India, comparable information for the dry deciduous sacred forests of Western Odisha had been essentially absent.

The implications extend beyond ecology into conservation policy. Sacred forests persist as biodiversity hotspots and providers of ecosystem services, including carbon sequestration, water regulation, and soil conservation, precisely because community restrictions limit timber extraction, grazing, and fuelwood collection. Yet pressures such as fuelwood harvesting, livestock grazing, and non-timber forest product extraction persist to varying degrees, with Andhari and Dedungri showing signs of moderate degradation while Medha and Papanga remain relatively well preserved. By demonstrating that these culturally protected patches sustain high litter production, rapid decomposition, and substantial nutrient turnover, the study provides quantitative evidence that sacred forests function as localized reservoirs of soil fertility in human-dominated landscapes. As land-use intensification continues across tropical India, the researchers argue, protecting these living laboratories of biocultural conservation may be one of the most cost-effective strategies for maintaining nutrient cycling and ecological resilience in dry deciduous landscapes.

Subject of Research: Litterfall production, decomposition rates, and nutrient cycling in tropical dry deciduous sacred forests of Western Odisha, India

Article Title: Litterfall dynamics and decomposition-driven nutrient cycling in sacred forests of Eastern India

Article References: Pradhan, A., Mansingh, A., Gopinath, J. S., & Ekka, N. J. (2026). Litterfall dynamics and decomposition-driven nutrient cycling in sacred forests of Eastern India. Discover Plants, 3(1), Article 412. https://doi.org/10.1007/s44372-026-00892-7

Image Credits: AI Generated

DOI: 10.1007/s44372-026-00892-7

Keywords: litterfall, decomposition, nutrient cycling, sacred forests, tropical dry deciduous forest, Odisha, Shorea robusta, litterbags, soil fertility, ecosystem functioning, biocultural conservation, leaf litter