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The accurate estimation of carbon stocks in natural and plantation forests is a prerequisite for the realization of carbon peaking and neutrality. In this study, the potential of optical Sentinel-2A data and a digital elevation model (DEM) to estimate the spatial variation of carbon stocks was investigated in a mountainous warm temperate region in central Japan. Four types of image preprocessing techniques and datasets were used: spectral reflectance, DEM-based topography indices, vegetation indices, and spectral band-based textures. A random forest model combined with 103 field plots as well as remote sensing image parameters was applied to predict and map the 2160 ha University of Tokyo Chiba Forest. Structural equation modeling was used to evaluate the factors driving the spatial distribution of forest carbon stocks. Our study shows that the Sentinel-2A data in combination with topography indices, vegetation indices, and shortwave-infrared (SWIR)-band-based textures resulted in the highest estimation accuracy. The spatial distribution of carbon stocks was successfully mapped, and stand-age- and forest-type-level variations were identified. The SWIR-2-band and topography indices were the most important variables for modeling, while the forest stand age and curvature were the most important determinants of the spatial distribution of carbon stock density. These findings will contribute to more accurate mapping of carbon stocks and improved quantification in different forest types and stand ages.

AIM: To infer a forest carbon density map at 0.01° resolution from a radar remote sensing product for the estimation of carbon stocks in Northern Hemisphere boreal and temperate forests. LOCATION: The study area extends from 30° N to 80° N, covering three forest biomes – temperate broadleaf and mixed forests (TBMF), temperate conifer forests (TCF) and boreal forests (BFT) – over three continents (North America, Europe and Asia). METHODS: This study is based on a recently available growing stock volume (GSV) product retrieved from synthetic aperture radar data. Forest biomass and spatially explicit uncertainty estimates were derived from the GSV using existing databases of wood density and allometric relationships between biomass compartments (stem, branches, roots, foliage). We tested the resultant map against inventory‐based biomass data from Russia, Europe and the USA prior to making intercontinent and interbiome carbon stock comparisons. RESULTS: Our derived carbon density map agrees well with inventory data at regional scales (r² = 0.70–0.90). While 40.7 ± 15.7 petagram of carbon (Pg C) are stored in BFT, TBMF and TCF contain 24.5 ± 9.4 Pg C and 14.5 ± 4.8 Pg C, respectively. In terms of carbon density, we found 6.21 ± 2.07 kg C m⁻² retained in TCF and 5.80 ± 2.21 kg C m⁻² in TBMF, whereas BFT have a mean carbon density of 4.00 ± 1.54 kg C m⁻². Indications of a higher carbon density in Europe compared with the other continents across each of the three biomes could not be proved to be significant. MAIN CONCLUSIONS: The presented carbon density and corresponding uncertainty map give an insight into the spatial patterns of biomass and stand as a new benchmark to improve carbon cycle models and carbon monitoring systems. In total, we found 79.8 ± 29.9 Pg C stored in northern boreal and temperate forests, with Asian BFT accounting for 22.1 ± 8.3 Pg C.

[Objectives] To analyze the changes in of forest carbon sink and forestry economic development, provide reference for relevant management decisions, ecological governance and resource and environment management, and promote the development of green low-carbon economy in China. [Methods] Based on the data of six forest resource inventories from 1989 to 2018 and related studies, the comprehensive evaluation model of forest carbon sink and forestry economic development, the coupling degree model of forest carbon sink and forestry economic development, and the coupling coordination degree model of forest carbon sink and forestry economic development were adopted. The coupling degree of forest carbon sink and forestry economic development from 1992 to 2018 was analyzed. Stepwise regression and ARIMA model were used to analyze the influencing factors and lagging characteristics of forest carbon sink. The coupling degree between forest carbon sink and forestry economic development in China from 2019 to 2030 was predicted by autoregression and ADF test. The coupling between forest carbon sink and forestry economic development in China and its long-term change characteristics were also discussed in this study. [Results] (i) The investment of ecological construction and protection, the actual investment of forestry key ecological projects, GDP and the import of forest products had a significant impact on forest resources carbon stock. The total output value of forestry industry, the actually completed investment of forestry key ecological projects and the export volume of forest products had a significant impact on the forest carbon sink, and the actually completed investment of forestry key ecological projects has the greatest impact on the two. (ii) The impact of actually completed investment of forestry key ecological projects had a lag of 2 years on the forest resources carbon stock and a lag of 1 year on the forest carbon sink. When investing in forest carbon sink, it is necessary to make a good plan in advance, and do a good job in forest resources management and time optimization. (iii) From 1992 to 2018, the coupling degree of forest resources carbon stock, forest carbon sink and long-term development of forestry economy in China was gradually increasing. Although there were some fluctuations in the middle time, the coupling degree of forest resources carbon stock and the long-term development of forestry economy increased by 9.24% annually, and the degree of coupling coordination increased from \"serious imbalance\" in 1992 to \"high-quality coordination\" in 2018. From 1993 to 2018, the coupling degree of forest carbon sink and long-term development of forestry economy increased by 9.63% annually, slightly faster than the coupling coordination degree of forest resources carbon stock and long-term development of forestry economy. The coordination level also rose from level 2 in 1993 to level 10 in 2018. (iv) The prediction shows that the coupling coordination degree of forest resources carbon stock, forest carbon sink and the long-term development of forestry economy would increase from 2019 to 2030. The coupling coordination degree (D) values of both were close to 1, the coordination level was also 10 for a long time, and the degree of coupling coordination was also maintained at the \"high-quality coordination\" level for a long time. [Conclusions] Forest has multiple benefits of society, economy and ecology, and forest carbon sink is only a benefit output. The long-term coupling analysis of forest carbon sink and forestry economic development is a key point to multiple benefit analysis. The analysis shows that the spillover effect and co-evolution effect of forest carbon sink in China are significant. From 1992 to 2018, the coupling coordination degree of forest carbon sink and forestry economic development was gradually rising. The prediction analysis also indicate that the coupling coordination degree between the forest carbon sink and the long-term development of forestry economy will remain at the level of \"high-quality coordination\" for a long time from 2019 to 2030. Therefore, improving the level of forest management and maintaining the current trend of increasing forest resources are the key to achieving the goal of carbon peaking and carbon neutrality in China.

Forests play a major role in the global carbon cycle. Previous studies on the capacity of forests to sequester atmospheric CO2 have mostly focused on carbon uptake, but the roles of carbon turnover time and its spatiotemporal changes remain poorly understood. Here, we used long-term inventory data (1955 to 2018) from 695 mature forest plots to quantify temporal trends in living vegetation carbon turnover time across tropical, temperate, and cold climate zones, and compared plot data to 8 Earth system models (ESMs). Long-term plots consistently showed decreases in living vegetation carbon turnover time, likely driven by increased tree mortality across all major climate zones. Changes in living vegetation carbon turnover time were negatively correlated with CO2 enrichment in both forest plot data and ESM simulations. However, plot-based correlations between living vegetation carbon turnover time and climate drivers such as precipitation and temperature diverged from those of ESM simulations. Our analyses suggest that forest carbon sinks are likely to be constrained by a decrease in living vegetation carbon turnover time, and accurate projections of forest carbon sink dynamics will require an improved representation of tree mortality processes and their sensitivity to climate in ESMs.

Forest carbon sinks (FCS) play an important role in mitigating global climate change, but there is a lack of more accurate, comprehensive, and efficient forest carbon stock estimates and projections for larger regions. By combining 1980–2020 land use data from the Northeast China Forestry (NCF) and climate change data under the Shared Socioeconomic Pathway (SSP), the land use and cover change (LUCC) of NCF in 2030 and 2050 and the FCS of NCF were estimated based on the measured data of forest carbon density. In general, the forest area of NCF has not yet recovered to the level of 1980. The temporal change in the FCS experienced a U-shaped trend of sharp decline to slow increase, with the inflection point occurring in 2010. If strict ecological conservation measures are implemented, the FCS of the NCF is expected to recover to the 1980 levels by 2050. We believe that the ecological priority (EP) scenario is the most likely and suitable direction for future development of the NCF. We also advocate for more scientific and stringent management measures for NCF natural forests to unlock the huge potential for forest carbon sequestration, which is important for China to meet its carbon neutrality commitments.

Background Forest soils are a globally significant carbon-store, including in deep layers (> 30 cm depth). However, there is high uncertainty regarding the response of deep soil organic carbon (DSOC) to climate change and the resulting impact on the total OC budget for forest ecosystems. Managed forests have an opportunity to reduce the risk of DSOC loss with climate change, however, the basic understanding of DSOC is lacking. Planted forests in New Zealand are managed with very limited knowledge of DSOC, both in the amount and the capacity of the soil to continue to store carbon with climate change. In this study, we explore DSOC stocks to at least 2 m depth at 15 planted forest sties in New Zealand. We also explore DSOC radiocarbon age and soil mineralogy, then contextualise our results within international SOC datasets and climate change vulnerability frameworks to identify research priorities for New Zealand’s planted forest soils. Results DSOC stocks and soil mineralogy in New Zealand’s planted forests were diverse both horizontally across soil types and vertically throughout the soil profile. Critically, limiting measurements of SOC to the top 30 cm misses more than half of the SOC stocks present to at least 2 m depth (mean 57%; range 33–72%). At depth, mineral-associated OC was the dominant fraction of DSOC (average > 90%) and was on average much older (> 1000 years) than the current planted forest land use (< 100 years). Conclusions This small case study highlights that New Zealand’s planted forests contain substantial stocks of DSOC, much of which is older than the current forest land use. The deep soils were dominated by reactive metals, and although the age of DSOC suggest long-term stability, the large contribution of reactive metal-mediated SOC stabilisation may indicate vulnerability to warming soil temperatures relative to other climate change factors. There is a pressing need to expand soil sampling to greater depths and establish a robust SOC baseline for New Zealand’s planted forests. This is essential for enabling spatial predictions of DSOC dynamics under future climate scenarios, identify the key controls on DSOC persistence, and concomitant impacts on forest ecosystem function and resilience.

Forests play an important role in mitigating many of the negative effects of climate change. One of the ways trees mitigate impacts of climate change is by absorbing carbon dioxide and storing carbon in their wood, leaves, roots, and soil. Field assessments are used to quantify the carbon storage across different forested landscapes. The number of trees, their size, and total area inform estimates of how much carbon they store. Urban forested natural areas often have greater tree density compared to trees planted in designed cityscapes suggesting that natural area forests could be an important carbon stock for cities. We report a carbon budget for urban forested natural area using field-collected data across an entire city and model carbon stock and annual stock change in multiple forest pools. We find that natural area forests in New York City store a mean of 263.04 (95% CI 256.61, 270.40) Mg C ha -1 and we estimate that 1.86 Tg C (95% CI 1.60, 2.13 Tg C) is stored in the city’s forested natural areas. We provide an upper estimate that these forests sequester carbon at a mean rate of 7.42 (95% CI 7.13, 7.71) Mg C ha -1 y -1 totaling 0.044 Tg (95% CI 0.028, 0.055) of carbon annually, with the majority being stored in trees and soil. Urban forested natural areas store carbon at similar and in some cases higher rates compared to rural forests. Native oak-dominated forests with large mature trees store the most carbon. When compared to previous estimates of urban-canopy carbon storage, we find that trees in natural area forests in New York City account for the majority of carbon stored despite being a minority of the tree canopy. Our results show that urban forested natural areas play an important role in localized, natural climate solutions and should be at the center of urban greening policies looking to mitigate the climate footprint of cities.

The scientific literature contains contrasting findings about the climate effects of forest bioenergy, partly due to the wide diversity of bioenergy systems and associated contexts, but also due to differences in assessment methods. The climate effects of bioenergy must be accurately assessed to inform policy‐making, but the complexity of bioenergy systems and associated land, industry and energy systems raises challenges for assessment. We examine misconceptions about climate effects of forest bioenergy and discuss important considerations in assessing these effects and devising measures to incentivize sustainable bioenergy as a component of climate policy. The temporal and spatial system boundary and the reference (counterfactual) scenarios are key methodology choices that strongly influence results. Focussing on carbon balances of individual forest stands and comparing emissions at the point of combustion neglect system‐level interactions that influence the climate effects of forest bioenergy. We highlight the need for a systems approach, in assessing options and developing policy for forest bioenergy that: (1) considers the whole life cycle of bioenergy systems, including effects of the associated forest management and harvesting on landscape carbon balances; (2) identifies how forest bioenergy can best be deployed to support energy system transformation required to achieve climate goals; and (3) incentivizes those forest bioenergy systems that augment the mitigation value of the forest sector as a whole. Emphasis on short‐term emissions reduction targets can lead to decisions that make medium‐ to long‐term climate goals more difficult to achieve. The most important climate change mitigation measure is the transformation of energy, industry and transport systems so that fossil carbon remains underground. Narrow perspectives obscure the significant role that bioenergy can play by displacing fossil fuels now, and supporting energy system transition. Greater transparency and consistency is needed in greenhouse gas reporting and accounting related to bioenergy. We examine misconceptions about climate effects of forest bioenergy and highlight the importance of a systems approach in assessing options and developing policy for forest bioenergy. Assessment should consider the whole bioeconomy, including the life cycle of bioenergy systems, effects on forest management and landscape carbon stocks, and effects on the energy and building sectors. Focussing on carbon balances of individual forest stands, emissions at the point of combustion and short‐term emissions reduction targets, neglects system‐level interactions and obscures the significant role that bioenergy can play by displacing fossil fuels now, and supporting energy system transformation.

Disturbed African tropical forests and woodlands have the potential to contribute to climate change mitigation. Therefore, there is a need to understand how carbon stocks of disturbed and recovering tropical forests are determined by environmental conditions and human use. In this case study, we explore how gradients in environmental conditions and human use determine aboveground biomass (AGB) in 1958 national forest inventory (NFI) plots located in forests and woodlands in mainland Tanzania. Plots were divided into recovering forests (areas recovering from deforestation for <25years) and established forests (areas consistently defined as forests for ⩾25 years). This division, as well as the detection of year of forest establishment, was obtained through the use of dense satellite time series of forest cover probability. In decreasing order of importance, AGB in recovering forests unexpectedly decreased with water availability, increased with surrounding tree cover and time since establishment, and decreased with elevation, distance to roads, and soil phosphorus content. AGB in established forests unexpectedly decreased with water availability, increased with surrounding tree cover, and soil nitrogen content, and decreased with elevation. AGB in recovering forests increased by 0.4 Mg ha −1 yr −1 during the first 20 years following establishment. Our results can serve as the basis of carbon sink estimates in African recovering tropical forests and woodlands, and aid in forest landscape restoration planning.

Management of secondary forest can contribute to climate change mitigation through carbon storage. In the Yucatan Peninsula, forest owners practise thinning and tree enrichment with commercial species in secondary forest, with the aim of halting deforestation and raising household income. This field study assessed the effects of thinning (60% removal) and tree species enrichment in 15 to 17-year-old secondary forests in Calakmul, Yucatan Peninsula, on carbon stocks (live biomass, dead biomass and soil organic carbon (SOC)), tree species diversity and abundance and the ability of tree species to store carbon. The treatments were two thinnings (T2), three thinnings (T3), two thinnings plus enrichment with pepper (Pimenta dioica) (T2P), no thinning and enrichment with cedar (Cedrela odorata) and mahogany (Swietenia macrophylla) (T0CM) and, natural secondary forest (NSF). There were no significant differences in total carbon stocks (live biomass C + dead biomass C + SOC) between treatments, but T2P had significantly less live biomass C than T2, T3 and NSF. There were also no significant differences in tree species diversity and richness between treatments, but T0CM differed from T2, T3 and NSF in terms of species abundance. In the present study some tree species with high potential to store carbon were identified. Although no increment in carbon stocks were identified at the time of the carbon stock assessment (10–12 years after thinning) with 60% removal of vegetation compared to NSF, the nursed and introduced tree species give extra benefits to landowners, with no detrimental effects on forest diversity.