The research focused on plantations established in 2016 under Jan Van Yojna, a private-land social forestry scheme launched by the Government of Jharkhand in which beneficiaries plant timber and fruit trees on plots of 0.5 to 50 acres, with the state covering 75 percent of establishment and maintenance costs for the first three years. By December 2020 the scheme had created 172.77 acres of new plantation cover across Ranchi district, holding 15,849 trees. Yet despite its policy significance, no published quantitative evaluation of the scheme’s carbon storage performance had existed until now.

The team, led by Md Shahzad Ahmad of Ranchi University, selected two sites from 26 active plantations in Ranchi district. The first, at BUDMU, was a 2.2-acre polyculture of 652 trees spanning seven species: four timber species, teak (Tectona grandis), gamhar (Gmelina arborea), mahogany (Swietenia macrophylla) and shisham (Dalbergia sissoo), alongside three fruit trees, mango, amla and guava. The second, at ANGADA, was a 2.0-acre monoculture of 500 teak trees. Both sites sat on the shallow, red-brown lateritic soils of the Ranchi plateau and had been managed under the standard JVY protocol, with the beneficiaries maintaining complete year-wise tree counts and maintenance records from 2016 to 2020.

The methodology combined several established carbon-accounting techniques. Every tree at both sites was individually enumerated and measured for girth at breast height, from which diameter was derived, and heights were recorded with a clinometer. Tree volumes were estimated using species-specific regression equations published by the Forest Survey of India, converted to green weight with species-specific wood densities, and then to dry weight using oven-dry ratios. The carbon content of stem, branch and leaf tissues was determined by the modified Walkley-Black wet oxidation titration, run in triplicate with a coefficient of variation below five percent. Root carbon was estimated as 26 percent of the above-ground total, following allometric proportions documented for tropical trees. Finally, total carbon was converted to carbon dioxide equivalents using the IPCC Tier-1 stoichiometric factor of 44/12, or 3.667.

The results were unambiguous at the site level. The BUDMU polyculture stored 15.32 tonnes of carbon, equivalent to 56.19 tonnes of CO2, or 17.21 tonnes of carbon per hectare. The ANGADA monoculture stored 5.92 tonnes of carbon, or 21.71 tonnes of CO2, at 7.31 tonnes per hectare. Normalised by area, the polyculture’s advantage was 2.35-fold, slightly lower than the whole-site ratio of 2.59 because BUDMU also carried a higher stem density, 732 trees per hectare against 618. Per-tree carbon dioxide equivalent at BUDMU was 86.17 kilograms, nearly double the 43.42 kilograms at ANGADA, despite the polyculture holding only 30 percent more individual trees.

Perhaps the most ecologically revealing finding was that a single species drove most of the polyculture’s advantage. Gmelina arborea, a fast-growing pioneer with low wood density and heavy stem allocation, accounted for 58.80 percent of the BUDMU site’s carbon total, or 33.04 tonnes of CO2. Teak contributed 18.44 percent and shisham 10.92 percent, with the remaining four species collectively adding 11.85 percent. Intriguingly, when the researchers compared teak trees across the two sites, individual teak trees in the mixed stand were marginally heavier in carbon, 12.28 kilograms per tree against 11.84 kilograms at the monoculture. The authors suggest, cautiously, that this is consistent with a facilitative inter-specific effect, possibly involving reduced intraspecific competition or nitrogen enrichment from the leguminous Dalbergia sissoo, though the study did not directly test this hypothesis.

Component-wise analysis showed that stems dominated carbon storage in most species, following the pattern stem, root, branch, leaf. At BUDMU overall, 69.91 percent of carbon sat in stems, 20.63 percent in roots, 9.03 percent in branches and just 0.40 percent in leaves. Notable exceptions emerged in mahogany and amla, which allocated more carbon to branches than to stems, a pattern the authors attribute to the high architectural branching characteristic of these species at this young growth stage.

The team then translated the ecological measurements into economic terms under three price scenarios. Using Voluntary Carbon Market pricing of five dollars per tonne of CO2 at the conservative end and fifteen dollars per tonne for certified nature-based-solution projects at the premium end, the BUDMU site’s sequestered carbon carried a hypothetical value of 280.93 to 842.79 dollars, while ANGADA’s ranged from 108.56 to 325.68 dollars. Under India’s Green Credit Programme rate of 650 rupees per tonne, the combined domestic potential was 50,634 rupees. The authors stress repeatedly that these figures are hypothetical and illustrative: neither site has undergone additionality assessment, third-party verification or registration with any carbon standard, and the revised Green Credit Programme framework issues forestry-linked credits only after a post-plantation monitoring period and makes them non-tradable outside limited circumstances.

The study is equally candid about its limitations, which the authors argue should shape how the findings are used. With one plantation sampled per management type, plantation type and site are completely confounded, meaning the observed difference could reflect species composition, underlying site quality, planting density or management history, and the design cannot statistically separate these contributions. The two sites were also purposively selected as the best-surviving examples from a scheme that experienced substantial attrition: only 26 of 78 original beneficiaries in Ranchi district remained active by 2020, with roughly 18 percent plant survival scheme-wide, and only four active sites retained 400 or more surviving trees. Sensitivity analyses varying the root-to-shoot proportion between 20 and 30 percent and the carbon factor by ten percent produced an indicative uncertainty envelope of roughly eight to twelve percent around the headline figures, applied symmetrically at both sites.

Even so, the findings carry real weight for policy. India’s updated Nationally Determined Contribution commits the country to creating an additional carbon sink of 2.5 to 3.0 billion tonnes of CO2 equivalent through forest and tree cover by 2030, and Jharkhand suffers among the highest rates of forest degradation in the country. The authors suggest, as a hypothesis for further testing rather than a formal recommendation, that plantation designs combining a fast-growing carbon sink like Gmelina arborea with nitrogen-fixing timber trees and fruit species could optimise carbon, livelihood and biodiversity outcomes simultaneously, since the fruit trees provide interim household income during the timber rotation. They recommend a replicated, multi-site carbon-monitoring programme across a stratified sample of active JVY sites before such a design becomes departmental guidance, and they note that any carbon-finance engagement would need to aggregate many smallholder plots into a single project to make monitoring and verification costs proportionate to the modest credit volumes each individual plot generates. If those hurdles can be cleared, the BUDMU and ANGADA comparison suggests that the species mix written into a planting plan may matter as much as the act of planting itself.

Subject of Research: Comparative carbon storage and green economy valuation of polyculture versus monoculture plantations under a social forestry scheme in Jharkhand, India

Article Title: Comparative biomass carbon storage, CO2 mitigation potential and green economy valuation of polyculture and monoculture plantations under the Jan Van Yojna social forestry scheme in semi-humid tropical Jharkhand India

Article References: Ahmad, M. S., Singh, U. S., & Naaz, N. (2026). Comparative biomass carbon storage, CO2 mitigation potential and green economy valuation of polyculture and monoculture plantations under the Jan Van Yojna social forestry scheme in semi-humid tropical Jharkhand India. Discover Forests, 2(1), Article 79. https://doi.org/10.1007/s44415-026-00142-4

Image Credits: AI Generated

DOI: 10.1007/s44415-026-00142-4

Keywords: carbon sequestration, social forestry, polyculture, monoculture, Tectona grandis, Gmelina arborea, Jharkhand, Jan Van Yojna, carbon credits, Green Credit Programme, IPCC Tier-1, tropical plantations