Carbon Sequestration Potential Research Articles

Fly ash-doped biochar fabricated by pyrolysis and hydrothermal strategies: characteristics and potentialities of carbon sequestration

The oxidation of biochar occurs due to both natural and human influences during the soil carbon sequestration process. Therefore, it is crucial to produce high-stability biochar to achieve carbon neutrality. Fly ash-doped biochar was obtained from fly ash and corn stalks by employing hydrothermal/pyrolysis treatment, along with alkali impregnation at different temperatures. The microstructural characteristics and carbon sequestration potentials were studied as an essential performance parameter that was influenced by mineral doping and treatment temperature. The yield and carbon retention of P500-1:2 improved by 54.15% and 6.81%, respectively, and the carbon loss following H2O2 oxidation was only 9.93% as depicted by the results. In comparison with hydrothermal biochar, pyrolysis biochar is superior in terms of its carbon sequestration potential. SiO2, Al2O3 and other components in fly ash continue to dissolve at high temperatures and react with carbon in biochar, promoting the formation of aromatic carbon and generating a physical protective layer to prevent biochar from oxidation, hence improving the chemical and thermal stability of biochar. High temperature and mineral interaction also contribute to high aromatic structure (H:C < 0.4) formation, significantly improving the specific surface area and thermal stability of biochar.Graphical

Midwater anoxia disrupts the trophic structure of zooplankton and fish in an oxygen deficient zone

AbstractAnoxic waters in the ocean's oxygen deficient zones (ODZs) limit the vertical migrations of zooplankton and mesopelagic fish impacting their ecology and influence on biogeochemical processes. Using an oxypleth‐tracking, nighttime‐only sampling protocol, this research reconstructed the trophic interactions of fish larvae and adults, and zooplankton, across the Eastern Tropical North Pacific ODZ. Bulk zooplankton δ15N increased latitudinally by ~ 3.3‰ from Costa Rica to Baja California due to anoxia‐derived denitrification and consequent enrichment of nitrogen sources for producers. Zooplankton δ15N also increased with depth, with an abrupt 3.4‰ increase below the anoxic core (~ 900 m depth), indicating a distinct trophic structure in the resident zooplankton community. Above the anoxic core, δ15N was similar for fish larvae (10.1‰) and zooplankton (10.5‰), reflecting a shared food source. An exception was the hypoxia‐tolerant myctophid Diogenichthys laternatus (δ15N = 7.5‰) that possibly feeds on chemoautotrophy‐derived material at the oxic‐anoxic interface. The δ15N of fish adults residing below the anoxic core, like the meso‐bathypelagic Notolychnus valdiviae (17.11‰) and Cyclothone spp. (15.89‰), was, on average, 4.8‰ higher than larval stages sampled at shallower depths, and 1.2‰ higher than zooplankton below the anoxic core. This stark increase in fish and zooplankton δ15N directly below the anoxic core suggests that anoxic waters act as a barrier for the downward trophic transfer by vertical migrants into the deep sea. Considering the current trends of ocean deoxygenation, this anoxia‐derived disruption of the migrant pump could limit the carbon sequestration potential of ODZs.

Primary Mid-Succession Carbon Fluxes in a Spontaneously Recovering Post-Mining Ecosystem

Limited research exists on the carbon sequestration potential of spontaneously developing post-coal-mining sites in the mid-stage of primary succession. Therefore, in 2023, net ecosystem exchange (NEE) was quantified in Czechia using an eddy covariance (EC) tower to assess carbon fluxes in a spontaneously developing ecosystem dominated by pioneer tree species such as willow, along with aspen and birch, growing on a wave-like microtopography. The ecosystem functioned as a strong carbon sink, with an annual NEE of −415 g C m−2 yr−1, ~39 years after coal mining. This NEE was derived by gross ecosystem exchange (GEE) of −1423 g C m−2 yr−1 and ecosystem respiration (Reco) of 1008 g C m−2 yr−1. Seasonal variation was driven by higher GEE in summer rather than by Reco. Consequently, Reco accounted for ca. 51% of GEE in summer, compared to 56% in spring. In addition, temperature was an important climatic factor in spring, whereas vapor pressure deficit (VPD) and global radiation (Rg) were more critical in summer. Overall, our results highlight the robust carbon sequestration capacity of naturally developing pioneer forests, suggesting their potential role in restoring mined areas in Central Europe and other regions without water limitations following coal mining.

Growth Performance and Carbon Sequestration potential of Planted Albizia versicolor and Albizia harveyi in Morogoro, Tanzania

This study assessed the growth performance and Carbon sequestration potential of 21-year-old Albizia versicolor Welw ex. Oliver. (Av) and Albizia harveyi Fourn (Ah) planted in 2003 at Maseyu village, Morogoro, Tanzania. These species are among the species preferred for wood fuel in Tanzania and other countries within African savanna ecosystems. Seedlings of the two species were planted at a spacing of 2 x 2 m with 25 trees per plot (8 x 8 m) using a completely randomized block design with three replications. In 2024, measurements were taken for diameter at breast height (Dbh) and height. Data was analyzed to get means for Dbh, height, volume, annual increment (MAI), above-ground biomass (AGB) and above-ground Carbon stock (AGC). An independent t-test was used to analyze differences in species parameters using R-studio. Results showed significant differences in stocking density (p &lt; 0.001), Dbh (p &lt; 0.001) and height (p &lt; 0.001) between species, with Albizia versicolor exhibiting larger mean Dbh (8.82 ± 1.36 cm) and height (7.46 ± 1.47 m) but relatively lower stocking density (1,188 ± 407 stems/ha) compared to Albizia harveyi (7.33 ± 1.16 cm,6.63 ± 2.28 m and 2,230 ± 1046 stems/ha respectively). However, no significant differences were found in volume, AGB, and AGC. Volume increments were 2.41 m³/ha/yr for Albizia versicolor and 2.58 m³/ha/yr for Albizia harveyi, while AGB increments were 1.23 and 1.17 t/ha/year for Albizia versicolor and Albizia harveyi respectively. Above-ground Carbon (AGC) stock increments (0.58 and 0.62 tC ha⁻¹ year⁻¹) for Albizia versicolor and Albizia harveyi respectively under monoculture were consistent with studies on mature Miombo woodlands. These findings suggest that both Albizia species perform well in monoculture growth, demonstrating their potential for sustainable Miombo woodland management and Carbon sequestration, despite lower biomass accumulation rates compared to natural Miombo ecosystems.

Estimating Soil Carbon Sequestration Potential in Portuguese Agricultural Soils Through Land-Management and Land-Use Changes

Soil carbon sequestration (SCS) is a nature-based, low-cost climate mitigation strategy that also contributes to the climate adaptation of agricultural systems. Some land-use and land-management practices potentially lead to an enhancement of the soil organic carbon (SOC) sink, such as no-till, the use of cover crops, leaving residues on fields, improving the variety of legume species in grasslands and reducing grazing intensity. However, uncertainties remain both in estimating and measuring the impact of the application of certain practices, as these vary with the soil, climate and historic land use. IPCC (Intergovernmental Panel on Climate Change) guidelines are commonly used to estimate SOC and SOC sequestration potentials at different tiers. Here, the IPCC’s tier 1 methodology was applied to estimate (1) the sequestration potential of nine mitigation practices and (2) the emission or sequestration potential of four current land-change trends for n = 7092 unique agricultural sites in mainland Portugal. The conversion of irrigated crops to improved grasslands resulted in the highest average unit sequestration (1.05 tC ha−1 yr−1), while cropland conversion to poor degraded pasture (abandonment) resulted in the highest unit SOC loss (−0.08 tC ha−1 yr−1). The abandonment of cropland results in a national SOC loss of up to 0.09 MtC yr−1, while the improvement of poor degraded pastures has the highest national sequestration potential, equal to 0.6 MtC yr−1 (2.2 MtCO2eq yr−1), about 4% of Portugal’s emissions in 2021, if applied in all managed areas. The results enable a comparison between different practices and land uses; however, to enhance accuracy, a higher tier methodology tailored to the Portuguese context should be developed.

Estimating mineral-associated organic carbon saturation and sequestration potential using MIR spectral based local quantile regression

Estimating mineral-associated organic carbon saturation and sequestration potential using MIR spectral based local quantile regression

Carbon dynamics in seawater and sediment: A case study of shellfish and seaweed mariculture systems.

Shellfish and seaweed, the primary mariculture species in China, generate significant amounts of dissolved organic matter (DOM) during growth. This production significantly influences the carbon cycle in the marine environment. In the present study, we evaluated the DOM changes during growth in both seawater and sediments in Nan'ao, Guangdong Province, southern China. The results showed that both shellfish and seaweed growth increased organic carbon content in seawater and sediments. DOM and water-extractable organic matter in the seaweed cultivation area exhibited greater aromaticity and hydrophobicity, indicating that seaweed-produced organic matter is more difficult to decompose and resistant to consumption. This implies a potential to expand the refractory dissolved organic carbon (RDOC) pool in the marine environment. We also estimated carbon removal and carbon sequestration by shellfish and seaweed culture in Guangdong Province from 2012 to 2021. Average carbon removal by shellfish cultivation is at 227.81GgC yr-1, and the release of carbon is at 205.71GgC yr-1. Carbon removal by seaweed cultivation is at 22.95GgC yr-1 with carbon sequestration of 11.89GgC yr-1. Compared with shellfish, seaweed has a large carbon sequestration potential. The integrated aquaculture of shellfish and seaweed in adjacent areas, given the environmental and socioeconomic benefits of absorbing nitrogen and phosphorus nutrients, mitigating eutrophication, and ocean acidification, is advisable for coastal developing countries to promote shellfish-seaweed farming.

Forest management reduces soil carbon sequestration potential in European temperate forests

Forest management reduces soil carbon sequestration potential in European temperate forests

InVEST-based assessment of carbon sequestration potentials and environmental dynamics in the coastal area of Lagos

InVEST-based assessment of carbon sequestration potentials and environmental dynamics in the coastal area of Lagos

A critical review of exploring the recent trends and technological advancements in forest biomass estimation

Biomass estimation is pivotal in understanding and managing global carbon stocks, offering vital insights into climate change and environmental ecology. It serves as a critical tool for evaluating carbon sequestration potential, a natural mechanism for regulating atmospheric carbon dioxide levels. Accurate estimation of forest biomass not only aids in quantifying carbon stocks but also provides a basis for sustainable forest management, conservation efforts, and policymaking to mitigate climate change impacts. This article provides a comprehensive review of various biomass estimation methods, including ground-based measurements, remote sensing technologies, and hybrid approaches. Each method's strengths, limitations, and practical applications are critically examined, highlighting their suitability for different spatial scales and ecological contexts. Traditional methods, while precise at small scales, are often labour-intensive and limited in coverage. In contrast, remote sensing technologies such as LiDAR, RADAR, and hyperspectral imaging have revolutionized biomass estimation by enabling large-scale and high-resolution assessments. Additionally, recent advancements in machine learning, data fusion, and satellite-based monitoring systems are transforming the field, offering unprecedented accuracy and efficiency. By presenting these trends and innovations, this article provides valuable insights for researchers, practitioners, and policymakers, emphasizing the importance of integrating advanced technologies into biomass estimation for sustainable development and climate resilience.

Estimation of the Water Footprint of Wood Construction in Chile Using a Streamlined Input–Output-Based Model

Wood construction is often proposed to reduce the construction sector’s greenhouse gas emissions due to its carbon sequestration potential. However, forestry significantly impacts natural water flows and increases water use—a critical concern in Chile. This study evaluates the water footprint of wood construction in Chile, considering direct and indirect water consumption under various scenarios. An input–output model was developed to quantify economic interactions, incorporating a new wood-construction sector based on data from a model house. An environmental extension matrix was also created to account for blue water (groundwater and surface water extraction) and green water (rainwater absorbed from soil) consumption. Future scenarios for the residential building sector were defined based on different growth rates for wood-based construction and current construction methods, and the model was resolved using the scenarios as demand vectors. The results indicate that wood construction’s water footprint is 2.38–2.47 times higher than conventional construction methods, with over 64% linked to forestry’s green water demand. By 2050, increased wood construction could raise the sector’s total water footprint by 30.0–31.8%. These findings underscore the need to assess water consumption as a critical sustainability parameter for wood construction and highlight the value of tools like the water footprint to guide decision-making.

Evaluating Impact of Agricultural Land Use on CO₂ Sequestration and Oxygen Release: A Case Study in Aranyik Subdistrict, Thailand

This study investigates the impact of various agricultural land use practices on CO₂ sequestration and oxygen release in Aranyik Subdistrict, Mueang District, Phitsanulok Province, Thailand. The region, characterized by lowland plains and a network of canals, supports diverse agricultural activities, with rice paddies dominating the landscape. Our analysis revealed significant variability in biomass distribution and carbon sequestration potential across different land use types. Eucalyptus plantations demonstrated the highest CO₂ sequestration and oxygen release rates, highlighting their role in climate change mitigation. However, the ecological implications of such monocultures, including water consumption and soil health, warrant careful consideration. In contrast, other land use types, such as mixed grasslands, lime orchards, and rice fields, exhibited lower sequestration rates but are crucial for maintaining biodiversity and supporting sustainable land management. This study underscores the importance of integrated land use strategies that balance carbon storage with ecological health, providing valuable insights for regional land use policy and climate change mitigation efforts. Further research should explore temporal land use changes and their broader environmental impacts to enhance the sustainability of agricultural practices in the region.

Assessing Urban Agriculture’s Potential for Biodiversity Conservation, Carbon Sequestration, and Community Development: A Comparative Study of Residents’ Perceptions in Three Western Romanian Cities

Urban agriculture is increasingly recognized as a strategy for enhancing sustainability and well-being in urban areas, mainly through circular economy principles. This study investigates residents’ perspectives from three major cities in western Romania—Arad, Timișoara, and Oradea—on the implementation and benefits of urban agriculture. The main goal was to identify differences in opinions regarding urban agriculture’s potential to improve biodiversity conservation, enhance carbon dioxide retention, and reduce synthetic compound usage. The research also explored community development through circular economy practices and tools local authorities could use to promote urban agriculture. A survey of 573 respondents utilized variance analysis and the Tukey test to reveal significant opinion differences among residents. The findings showed notable variations in views on biodiversity conservation and community development benefits but no significant differences in opinions on carbon dioxide capture or synthetic chemical use. Residents of Timișoara and Oradea expressed more favorable views on urban agriculture than those in Arad. Participants emphasized the importance of free land allocation and sustainable practices for successful urban agriculture implementation. This study offers valuable insights for policymakers and contributes to the understanding of urban sustainability and the role of urban agriculture in supporting circular economy principles.

Assessing and optimizing the potential for climate change mitigation and carbon sequestration in urban residential green spaces: energizing sustainable cities

IntroductionUrban green spaces play a crucial role in mitigating climate change by sequestering atmospheric carbon dioxide. This study aimed to evaluate the carbon sequestration potential of common plant species in urban residential areas and provide recommendations for optimizing green space design and management.MethodsThe research was conducted in four residential areas of Nanjing, China, where key growth parameters of 20 plant species, including evergreen trees, deciduous trees, evergreen shrubs, and deciduous shrubs, were measured. The assimilation method was employed to calculate carbon sequestration per unit canopy area and for entire plants.ResultsThe results showed that the carbon sequestration capacities of different plant species and types exhibited significant differences, with p-values less than 0.05. In terms of daily carbon sequestration per unit canopy projection area, the ranking was as follows: evergreen trees &amp;gt; evergreen shrubs &amp;gt; deciduous trees &amp;gt; deciduous shrubs. For total plant carbon sequestration, the ranking was: evergreen trees &amp;gt; deciduous trees &amp;gt; evergreen shrubs &amp;gt; deciduous shrubs. Evergreen trees performed excellently in both carbon sequestration metrics, with the average daily carbon sequestration per unit canopy projection area and for the entire plant being 18.0024 g/(m2·d) and 462.28 g/d, respectively. The study also observed seasonal variations, with carbon sequestration rates being higher in autumn and summer compared to spring and winter. During the summer, the average daily carbon sequestration per unit canopy projection area and for the entire plant were 11.975 g/(m2·d) and 161.744 g/d, respectively, while in autumn, these values were 13.886 g/(m2·d) and 98.458 g/d. Seasonal variations were also observed, with autumn and summer exhibiting higher carbon sequestration rates compared to spring and winter. Additionally, CO2 concentrations were monitored across the four residential areas, providing insights into the spatial and temporal dynamics of carbon sequestration.DiscussionBased on the findings, optimization strategies were proposed, such as prioritizing the selection and integration of high-performing evergreen tree species in urban green space design and incorporating diverse plant types to enhance year-round carbon sequestration. This study contributes to the development of sustainable urban planning and landscape management practices, promoting the role of green spaces in mitigating climate change and enhancing urban resilience.

Microplastics influencing aquatic environment and human health: A review of source, determination, distribution, removal, degradation, management strategy and future perspective.

Microplastics (MPs) are produced from various primary and secondary sources and pose multifaceted environmental problems. They are of non-biodegradable nature and may stay in aquatic environments for a long time period. The present review has covered novel aspects pertaining to MPs that were not covered in earlier studies. It has been observed that several methods are being employed for samples collection, extraction and identification of MPs and polymer types using various equipment, chemicals and instrumental techniques. Aquatic species mistakenly ingest MPs, considering them prey and through food-chain, and then suffer from various metabolic disorders. The consumption of seafood and fish may consequently cause health implications in humans. Certain plasticizers are added during manufacturing to provide colour, durability, flexibility, and strength to plastics, but they leach out during usage, storage, and transport, as well as after entering the bodies of aquatic species and human beings. The leached chemicals (bisphenol-A, triclosan, phthalates, etc.) act as endocrine disrupting chemicals (EDCs), which effect on homeostasis; thereby causing neurotoxicity, cytotoxicity, reproductive problems, adverse behaviour and autism. Negative influence of MPs on carbon sequestration potential of water bodies is also observed, however more studies are required to understand it with a detail mechanism under natural conditions. The wastewater treatment plants are found to remove a large amount of MPs, but in turn, also act as significant sources of their release in sludge and effluents. Further, it is covered that how advanced oxidation processes, thermal- and photo-oxidation, fungi, algae and microbes degrade the plastics and increase their numbers in the surrounding environment. The management strategy comprising recovery of energy and other valuable by-products from plastic wastes, recycling and regulatory framework; are also described in detail. The future perspectives can be of paramount importance to control MPs generation and their abundance in the aquatic and other types of environments. The studies in future need to focus on advanced filtration techniques, advanced oxidation processes, energy recovery from plastic wastes and influences of MPs on carbon sequestration in aquatic environment and human health.

Spatial and Temporal Variations in Soil Organic Carbon in Northwestern China via Comparisons of Different Methods

Soil organic carbon (SOC) is a crucial component for investigating carbon cycling and global climate change. Accurate data exhibiting the temporal and spatial distributions of SOC are very important for determining the soil carbon sequestration potential and formulating climate strategies. An important scheme of mapping SOC is to establish a link between environmental factors and SOC via different methods. The Shiyang River Basin is the third largest inland river basin in the Hexi Corridor, which has closed geographical conditions and a relatively independent carbon cycle system, making it an ideal area for carbon cycle research in arid areas. In this study, 65 SOC samples were collected and 21 environmental factors were assessed from 2011 to 2021 in the Shiyang River Basin. The linear regression (LR) method and two machine learning methods, i.e., support vector machine regression (SVR) and random forest (RF), are applied to estimate the spatial distribution of SOC. RF is slightly better than SVR because of its advantages in the comparison of classification. When latitude, slope, and the normalized vegetation index (NDVI) are used as predictor variables, the best SOC performance is shown. Compared with the Harmonized World Soil Database (HWSD), the optimal scheme improved the accuracy of the SOC significantly. Finally, the spatial distribution of SOC tended to increase, with a total increase of 135.94 g/kg across the whole basin. The northwestern part of the middle basin decreased by 2.82% because of industrial activities. The SOC in Minqin County increased by approximately 62.77% from 2011 to 2021. Thus, the variability of the spatial SOC increased. This study provides a theoretical basis for the spatial and temporal distributions of SOC in inland river basins. In addition, this study can also provide effective and scientific suggestions for carbon projects, offer a key scientific basis for understanding the carbon cycle, and support global climate change adaptation and mitigation strategies.

Ecosystem water use efficiency and carbon use efficiency respond oppositely to vegetation greening in China's Loess Plateau.

Ecosystem water use efficiency (WUE) and carbon use efficiency (CUE) are critical parameters to determine the trade-off between water consumption and carbon sequestration in drylands. However, the roles of vegetation cover, climate factors and soil moisture in affecting the coupling of WUE and CUE were still poorly understood. This study combined the spatial random forest model and structural equation model to detect the drivers of WUE and CUE variations in China's Loess Plateau during 2001-2020, a typical water-limited region with about 87% of area experiencing significant vegetation greening. The WUE increased significantly (P<0.05) in 92.7% of the greening area (0.024±0.020 gC kg-1H2O yr-1), and CUE decreased (-0.0011±0.0011yr-1) and increased (0.0010±0.0012yr-1) slightly in half and half of the greening area. The vegetation greening trend was a dominant factor positively influencing the variation of WUE (with 42.0% explanation), whereas CUE exhibited a negative response to the greening trend (with 25.0% explanation). However, the regions with dense vegetation cover (NDVI >0.5) were unfavourable for the increase of WUE but favourable for the increase of CUE. Vegetation greening exerted effect on WUE mainly via the path of gross primary productivity and ratio of transpiration to evapotranspiration (path coefficient: 0.83), whereas it had direct effect on CUE (path coefficient: 0.48). An increase in VPD facilitated the enhancement of both WUE and CUE. There was an optimal annual precipitation range (400-600mm) that maximized WUE enhancement, and annual temperature (∼10°C) optimized CUE increase. The findings indicate that despite the improvement in WUE, the vegetation greening may not necessarily enhance carbon sequestration potential in drylands. This study enhances the knowledge of the interaction between vegetation dynamics and water‑carbon coupling in drylands, contributing to ecological restoration practices and sustainable ecosystem management.

Estimation of the total carbon sequestration potential of coconut-gliricidia mixed cropping systems in Sri Lanka

Offsetting carbon footprints by sequestering carbon through plant biomasses has become a key concern under modern thinking on climate change mitigation. This study aimed to estimate the carbon sequestration capacities of coconut-based gliricidia mixed cropping systems in Sri Lanka and, importantly, to develop an allometric model for non-destructive estimation of carbon. Five major coconut age groups and four major gliricidia age groups were selected to estimate the total carbon stock. The age groups of coconut considered were 10, 20, 30, 40, and 50 years, with corresponding carbon stocks of 22.59, 34.99, 53.13, 63.40, and 66.03 Mg[C]ha-1, respectively. In gliricidia stands, carbon stocks were 25.53, 46.16, 83.83, and 106.09 Mg[C]ha-1, respectively, for age groups of 5, 10, 15, and 20 years. It is recommended that gliricidia be introduced as an intercrop in coconut plantations 20 years after the establishment of the latter. For this study, a 30-year-old coconut plantation with a 10-year-old gliricidia intercrop, along with its associated ground cover vegetation and soil carbon stock, were considered the benchmark agroforestry system. In the 30-year-old coconut monocropping system, the total carbon stock was 67.76 Mg[C]ha-1, which consisted of uniform coconut, 1.24 Mg[C]ha-1 from ground cover vegetation and 13.39 Mg[C]ha-1 from the soil carbon stock at a depth of 30 cm. The overall carbon sequestration rate for this monocropping system was 2.25 Mg[C]ha-1yr-1 and abated CO2 in 8.23 Mg[CO2]ha-1yr-1. In the 30-year-old coconut and 10-year-old gliricidia mixed cropping system, the total carbon stock was 114.83 Mg[C]ha-1, which consisted of uniform coconut and Gliricidia, 1.05 Mg[C]ha-1 from ground cover plants, and 14.49 Mg[C]ha-1 from soil carbon stock at a depth of 30 cm. Compared to the coconut monocropping system, the coconut-gliricidia mixed cropping system had a higher carbon sequestration rate of 6.84 Mg[C]ha-1yr-1 and abated CO2 in 25.03 Mg[CO2]ha-1yr-1, which are around three times higher than the monoculture system.

Species Diversity, Biomass Production and Carbon Sequestration Potential in the Protected Area of Uttarakhand, India.

Ecosystem functioning and management are primarily concerned with addressing climate change and biodiversity loss, which are closely linked to carbon stock and species diversity. This research aimed to quantify forest understory (shrub and herb) diversity, tree biomass and carbon sequestration in the Binsar Wildlife Sanctuary. Using random sampling methods, data were gathered from six distinct forest communities. The study identified 271 vascular plants from 208 genera and 74 families. A notable positive correlation (r2 = 0.085, p < 0.05) was observed between total tree density and total tree basal area (TBA), shrub density (r2 = 0.09), tree diversity (D) (r2 = 0.58), shrub diversity (r2 = 0.81), and tree species richness (SR) (r2 = 0.96). Conversely, a negative correlation was found with the concentration of tree dominance (CD) (r2 = 0.43). The Quercus leucotrichophora, Rhododendron arboreum and Quercus floribunda (QL-RA-QF) community(higher altitudinal zone) exhibited the highest tree biomass (568.8 Mg ha-1), while the (Pinus roxburghii and Quercus leucotrichophora) PR-QL (N) community (lower altitudinal zone) in the north aspect showed the lowest (265.7 Mg ha-1). Carbon sequestration was highest in the Quercus leucotrichophora, Quercus floribunda and Rhododendron arboreum (QL-QF-RA) (higher altitudinal zone) community (7.48 Mg ha-1 yr-1) and lowest in the PR-QL (S) (middle altitudinal zone) community in the south aspect (5.5 Mg ha-1 yr-1). The relationships between carbon stock and various functional parameters such as tree density, total basal area of tree and diversity of tree showed significant positive correlations. The findings of the study revealed significant variations in the structural attributes of trees, shrubs and herbs across different forest stands along altitudinal gradients. This current study's results highlighted the significance of wildlife sanctuaries, which not only aid in wildlife preservation but also provide compelling evidence supporting forest management practices that promote the planting of multiple vegetation layers in landscape restoration as a means to enhance biodiversity and increase resilience to climate change. Further, comprehending the carbon storage mechanisms of these forests will be critical for developing environmental management strategies aimed at alleviating the impacts of climate change in the years to come.

A framework for upscaling aboveground biomass from an individual tree to landscape level and qualifying the multiscale spatial uncertainties for secondary forests

ABSTRACT Secondary forests, a typical forest type in the sub-frigid zone of Northeast China, have significant potential for carbon sequestration. Accurate estimation of the Aboveground Biomass (AGB) of secondary forests and assessment of multiscale uncertainties are crucial for promoting Reduced Emissions from Deforestation and Degradation. This study developed a novel framework to upscale the AGB estimation from the tree to the landscape level and assessed multiscale uncertainties based on multi-platform laser scanning data and Unmanned Aerial Vehicle (UAV) hyperspectral images. The framework included two stages: (1) quantifying multiple uncertainties (uncertainties of individual tree crown delineation, individual tree parameters estimation, and tree species classification) in individual tree-based AGB estimation using Monte Carlo simulations; (2) upscaling the plot to the landscape level estimated AGB using the Nonlinear Simultaneous Equation (NSE) with error-in-variables and quantifying the uncertainties of model residuals, model parameters, and model independent variables. The findings revealed a high accuracy from tree to plot AGB estimation (R2: 0.75, Root Mean Square Error (RMSE): 6.65 Mg/ha, relative RMSE (rRMSE): 5.40%), with the total and relative uncertainties of 16.85 Mg/ha and 16.29%, respectively, with the highest uncertainty (9.73 Mg/ha) observed in tree species classification. The AGB estimation using NSE achieved an R2 of 0.69, with an RMSE of 9.91 Mg/ha and an rRMSE of 10.43% from the plot to landscape level; and the uncertainties caused by model parameters, independent variables, and residuals were 5.52 Mg/ha, 14.56 Mg/ha, and 25.25 Mg/ha, respectively, accounting for 3.46%, 24.09%, and 72.45% of the total uncertainty. This study develops a framework for large-scale AGB estimation of mixed forests based on the individual tree approach and uncertainty quantification of multiscale estimates and provides a foundation for precise forestry, sustainable forest management, and carbon neutrality.