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Item A life cycle and product type based estimator for quantifying the carbon stored in wood products(Springer Nature, 2023-01-23) Wei, Xinyuan; Zhao, Jianheng; Hayes, Daniel J.; Daigneault, Adam; Zhu, HeBackground Timber harvesting and industrial wood processing laterally transfer the carbon stored in forest sectors to wood products creating a wood products carbon pool. The carbon stored in wood products is allocated to end-use wood products (e.g., paper, furniture), landfill, and charcoal. Wood products can store substantial amounts of carbon and contribute to the mitigation of greenhouse effects. Therefore, accurate accounts for the size of wood products carbon pools for different regions are essential to estimating the land-atmosphere carbon exchange by using the bottom-up approach of carbon stock change. Results To quantify the carbon stored in wood products, we developed a state-of-the-art estimator (Wood Products Carbon Storage Estimator, WPsCS Estimator) that includes the wood products disposal, recycling, and waste wood decomposition processes. The wood products carbon pool in this estimator has three subpools: (1) end-use wood products, (2) landfill, and (3) charcoal carbon. In addition, it has a user-friendly interface, which can be used to easily parameterize and calibrate an estimation. To evaluate its performance, we applied this estimator to account for the carbon stored in wood products made from the timber harvested in Maine, USA, and the carbon storage of wood products consumed in the United States. Conclusion The WPsCS Estimator can efficiently and easily quantify the carbon stored in harvested wood products for a given region over a specific period, which was demonstrated with two illustrative examples. In addition, WPsCS Estimator has a user-friendly interface, and all parameters can be easily modified.Item Above-ground tree carbon storage in response to nitrogen deposition in the U.S. is heterogeneous and may have weakened(Springer Nature, 2023-02-14) Clark, Christopher M.; Thomas, R. Quinn; Horn, Kevin J.Changes in nitrogen (N) availability affect the ability for forest ecosystems to store carbon (C). Here we extend an analysis of the growth and survival of 94 tree species and 1.2 million trees, to estimate the incremental effects of N deposition on changes in aboveground C (dC/dN) across the contiguous U.S. (CONUS). We find that although the average effect of N deposition on aboveground C is positive for the CONUS (dC/dN = +9 kg C per kg N), there is wide variation among species and regions. Furthermore, in the Northeastern U.S. where we may compare responses from 2000-2016 with those from the 1980s–90s, we find the recent estimate of dC/dN is weaker than from the 1980s–90s due to species-level changes in responses to N deposition. This suggests that the U.S. forest C-sink varies widely across forests and may be weakening overall, possibly necessitating more aggressive climate policies than originally thought.Item Carbon accumulation rates are highest at young and expanding salt marsh edges(Springer Nature, 2022-08-02) Miller, Carson B.; Rodriguez, Antonio B.; Bost, Molly C.; McKee, Brent A.; McTigue, Nathan D.An objective of salt marsh conservation, restoration, and creation is to reduce global carbon dioxide levels and offset emissions. This strategy hinges on measurements of salt marsh carbon accumulation rates, which vary widely creating uncertainty in monetizing carbon credits. Here, we show the 14–323 g C m−2 yr−1 range of carbon accumulation rates, derived from cores collected at seven sites in North Carolina U.S.A., results from the landward or basinward trajectory of salt marsh colonization and the intertidal space available for accretion. Rates increase with accelerating sea-level rise and are highest at young and expanding marsh edges. The highest carbon densities are near the upland, highlighting the importance of this area for building a rich stock of carbon that would be prevented by upland development. Explaining variability in carbon accumulation rates clarifies appraisal of salt marsh restoration projects and landscape conversion, in terms of mitigating green-house gas emissions.Item China’s terrestrial ecosystem carbon balance during the 20th century: an analysis with a process-based biogeochemistry model(Springer Nature, 2022-10-08) Lu, Yanyu; Huang, Yao; Zhuang, Qianlai; Sun, Wei; Chen, Shutao; Lu, JunBackground: China’s terrestrial ecosystems play a pronounced role in the global carbon cycle. Here we combine spatially-explicit information on vegetation, soil, topography, climate and land use change with a process-based bio geochemistry model to quantify the responses of terrestrial carbon cycle in China during the 20th century. Results: At a century scale, China’s terrestrial ecosystems have acted as a carbon sink averaging at 96 Tg C yr−1, with large inter-annual and decadal variabilities. The regional sink has been enhanced due to the rising temperature and CO2 concentration, with a slight increase trend in carbon sink strength along with the enhanced net primary production in the century. The areas characterized by C source are simulated to extend in the west and north of the Hu Huanyong line, while the eastern and southern regions increase their area and intensity of C sink, particularly in the late 20th century. Forest ecosystems dominate the C sink in China and are responsible for about 64% of the total sink. On the century scale, the increase in carbon sinks in China’s terrestrial ecosystems is mainly contributed by rising CO2. Aforestation and reforestation promote an increase in terrestrial carbon uptake in China from 1950s. Although climate change has generally contributed to the increase of carbon sinks in terrestrial ecosystems in China, the positive effect of climate change has been diminishing in the last decades of the 20th century. Conclusion: This study focuses on the impacts of climate, CO2 and land use change on the carbon cycle, and presents the potential trends of terrestrial ecosystem carbon balance in China at a century scale. While a slight increase in carbon sink strength benefits from the enhanced vegetation carbon uptake in China’s terrestrial ecosystems during the 20th century, the increase trend may diminish or even change to a decrease trend under future climate change.Item Comprehensive evidence implies a higher social cost of CO2(Springer Nature, 2022-09-01) Rennert, Kevin; Errickson, Frank; Prest, Brian C.; Rennels, Lisa; Newell, Richard G.; Pizer, William; Kingdon, Cora; Wingenroth, Jordan; Cooke, Roger; Parthum, Bryan; Smith, David; Cromar, Kevin; Diaz, Delavane; Moore, Frances C.; Müller, Ulrich K.; Plevin, Richard J.; Raftery, Adrian E.; Ševčíková, Hana; Sheets, Hannah; Stock, James H.; Tan, Tammy; Watson, Mark; Wong, Tony E.; Anthoff, DavidThe social cost of carbon dioxide (SC-CO2) measures the monetized value of the damages to society caused by an incremental metric tonne of CO2 emissions and is a key metric informing climate policy. Used by governments and other decision-makers in benefit–cost analysis for over a decade, SC-CO2 estimates draw on climate science, economics, demography and other disciplines. However, a 2017 report by the US National Academies of Sciences, Engineering, and Medicine (NASEM) highlighted that current SC-CO2 estimates no longer reflect the latest research. The report provided a series of recommendations for improving the scientific basis, transparency and uncertainty characterization of SC-CO2 estimates. Here we show that improved probabilistic socioeconomic projections, climate models, damage functions, and discounting methods that collectively reflect theoretically consistent valuation of risk, substantially increase estimates of the SC-CO2. Our preferred mean SC-CO2 estimate is $185 per tonne of CO2 ($44–$413 per tCO2: 5%–95% range, 2020 US dollars) at a near-term risk-free discount rate of 2%, a value 3.6 times higher than the US government’s current value of $51 per tCO2. Our estimates incorporate updated scientific understanding throughout all components of SC-CO2 estimation in the new open-source Greenhouse Gas Impact Value Estimator (GIVE) model, in a manner fully responsive to the near-term NASEM recommendations. Our higher SC-CO2 values, compared with estimates currently used in policy evaluation, substantially increase the estimated benefits of greenhouse gas mitigation and thereby increase the expected net benefits of more stringent climate policies.Item Conservation Agriculture and Soil Organic Carbon: Principles, Processes, Practices and Policy Options(MDPI, 2023-02-22) Francaviglia, Rosa; Almagro, María; Vicente-Vicente, José LuisIntensive agriculture causes land degradation and other environmental problems, such as pollution, soil erosion, fertility loss, biodiversity decline, and greenhouse gas (GHG) emissions, which exacerbate climate change. Sustainable agricultural practices, such as reduced tillage, growing cover crops, and implementing crop residue retention measures, have been proposed as cost-effective solutions that can address land degradation, food security, and climate change mitigation and adaptation by enhancing soil organic carbon (SOC) sequestration in soils and its associated co-benefits. In this regard, extensive research has demonstrated that conservation agriculture (CA) improves soil physical, chemical, and biological properties that are crucial for maintaining soil health and increasing agroecosystem resilience to global change. However, despite the research that has been undertaken to implement the three principles of CA (minimum mechanical soil disturbance, permanent soil organic cover with crop residues and/or cover crops, and crop diversification) worldwide, there are still many technical and socio-economic barriers that restrict their adoption. In this review, we gather current knowledge on the potential agronomic, environmental, and socio-economic benefits and drawbacks of implementing CA principles and present the current agro-environmental policy frameworks. Research needs are identified, and more stringent policy measures are urgently encouraged to achieve climate change mitigation targets.Item Ecological resilience of restored peatlands to climate change(Springer Nature, 2022-09-13) Loisel, Julie; Gallego-Sala, AngelaDegradation of peatlands through land-use change and drainage is currently responsible for 5-10% of global annual anthropogenic carbon dioxide emissions. Therefore, restoring disturbed and degraded peatlands is an emerging priority in efforts to mitigate climate change. While restoration can revive multiple ecosystem functions, including carbon storage, the resilience of restored peatlands to climate change and other disturbances remains poorly understood. Here, we review the recent literature on the response of degraded and restored peatlands to fire, drought and flood. We find that degraded sites can generally be restored in a way that allows for net carbon sequestration. However, biodiversity, hydrological regime, and peat soil structure are not always fully restored, even after a decade of restoration efforts, potentially weakening ecosystem resilience to future disturbances. As the recovery of degraded peatlands is fundamental to achieving net-zero goals and biodiversity targets, sound science and monitoring efforts are needed to further inform restoration investments and priorities.Item Ecosystem productivity has a stronger influence than soil age on surface soil carbon storage across global biomes(Springer Nature, 2022-10-07) Plaza, César; García-Palacios, Pablo; Berhe, Asmeret Asmeret; Barquero, Jesús; Bastida, Felipe; Png, G. Kenny; Rey, Ana; Bardgett, Richard D.; Delgado-Baquerizo, ManuelInteractions between soil organic matter and minerals largely govern the carbon sequestration capacity of soils. Yet, variations in the proportions of free light (unprotected) and mineral-associated (protected) carbon as soil develops in contrasting ecosystems are poorly constrained. Here, we studied 16 long-term chronosequences from six continents and found that the ecosystem type is more important than soil age (centuries to millennia) in explaining the proportion of unprotected and mineral-associated carbon fractions in surface soils across global biomes. Soil carbon pools in highly productive tropical and temperate forests were dominated by the unprotected carbon fraction and were highly vulnerable to reductions in ecosystem productivity and warming. Conversely, soil carbon in low productivity, drier and colder ecosystems was dominated by mineral-protected carbon, and was less responsive to warming. Our findings emphasize the importance of conserving ecosystem productivity to protect carbon stored in surface soils.Item Effects of forest degradation classification on the uncertainty of aboveground carbon estimates in the Amazon(Springer Nature, 2023-02-14) Rangel Pinagé, Ekena ; Keller, Michael; Peck, Christopher P.; Longo, Marcos; Duffy, Paul; Csillik, OvidiuBackground Tropical forests are critical for the global carbon budget, yet they have been threatened by deforestation and forest degradation by fire, selective logging, and fragmentation. Existing uncertainties on land cover classification and in biomass estimates hinder accurate attribution of carbon emissions to specific forest classes. In this study, we used textural metrics derived from PlanetScope images to implement a probabilistic classification framework to identify intact, logged and burned forests in three Amazonian sites. We also estimated biomass for these forest classes using airborne lidar and compared biomass uncertainties using the lidar-derived estimates only to biomass uncertainties considering the forest degradation classification as well. Results Our classification approach reached overall accuracy of 0.86, with accuracy at individual sites varying from 0.69 to 0.93. Logged forests showed variable biomass changes, while burned forests showed an average carbon loss of 35%. We found that including uncertainty in forest degradation classification significantly increased uncertainty and decreased estimates of mean carbon density in two of the three test sites. Conclusions Our findings indicate that the attribution of biomass changes to forest degradation classes needs to account for the uncertainty in forest degradation classification. By combining very high-resolution images with lidar data, we could attribute carbon stock changes to specific pathways of forest degradation. This approach also allows quantifying uncertainties of carbon emissions associated with forest degradation through logging and fire. Both the attribution and uncertainty quantification provide critical information for national greenhouse gas inventories.Item Environmental and microbial controls on microbial necromass recycling, an important precursor for soil carbon stabilization(Springer Nature, 2020-10-22) Buckeridge, Kate M.; Mason, Kelly E.; McNamara, Niall P.; Ostle, Nick; Puissant, Jeremy; Goodall, Tim; Griffiths, Robert I.; Stott, Andrew W.; Whitaker, JeanetteThere is an emerging consensus that microbial necromass carbon is the primary constituent of stable soil carbon, yet the controls on the stabilization process are unknown. Prior to stabilization, microbial necromass may be recycled by the microbial community. We propose that the efficiency of this recycling is a critical determinant of soil carbon stabilization rates. Here we explore the controls on necromass recycling efficiency in 27 UK grassland soils using stable isotope tracing and indicator species analysis. We found that recycling efficiency was unaffected by land management. Instead, recycling efficiency increased with microbial growth rate on necromass, and was highest in soils with low historical precipitation. We identified bacterial and fungal indicators of necromass recycling efficiency, which could be used to clarify soil carbon stabilization mechanisms. We conclude that environmental and microbial controls have a strong influence on necromass recycling, and suggest that this, in turn, influences soil carbon stabilization.Item Hydroclimatic vulnerability of peat carbon in the central Congo Basin(Springer Nature, 2022-11-02) Garcin, Yannick; Schefuß, Enno; Dargie, Greta C.; Hawthorne, Donna; Lawson, Ian T.; Sebag, David; Biddulph, George E.; Crezee, Bart; Bocko, Yannick E.; Ifo, Suspense A.; Wenina, Y. Emmanuel Mampouya; Mbemba, Mackline; Ewango, Borneille E. N.; Emba, Ovide; Bola, Pierre; Tabi, Joseph Kanyama; Tyrrell, Genevieve; Young, Dylan M.; Gassier, Ghislain; Girkin, Nicholas T.; Vane, Christopher H.; Adatte, Thierry; Baird, Andy J.; Boom, Arnoud; Gulliver, Pauline; Morris, Paul J.; Page, Susan E.; Sjögersten, Sofie; Lewis, SimonThe forested swamps of the central Congo Basin store approximately 30 billion metric tonnes of carbon in peat. Little is known about the vulnerability of these carbon stocks. Here we investigate this vulnerability using peat cores from a large interfluvial basin in the Republic of the Congo and palaeoenvironmental methods. We find that peat accumulation began at least at 17,500 calibrated years before present (cal. yr BP; taken as AD 1950). Our data show that the peat that accumulated between around 7,500 to around 2,000 cal. yr BP is much more decomposed compared with older and younger peat. Hydrogen isotopes of plant waxes indicate a drying trend, starting at approximately 5,000 cal. yr BP and culminating at approximately 2,000 cal. yr BP, coeval with a decline in dominant swamp forest taxa. The data imply that the drying climate probably resulted in a regional drop in the water table, which triggered peat decomposition, including the loss of peat carbon accumulated prior to the onset of the drier conditions. After approximately 2,000 cal. yr BP, our data show that the drying trend ceased, hydrologic conditions stabilized and peat accumulation resumed. This reversible accumulation–loss–accumulation pattern is consistent with other peat cores across the region, indicating that the carbon stocks of the central Congo peatlands may lie close to a climatically driven drought threshold. Further research should quantify the combination of peatland threshold behaviour and droughts driven by anthropogenic carbon emissions that may trigger this positive carbon cycle feedback in the Earth system.Item Improved dryland carbon flux predictions with explicit consideration of water-carbon coupling(Springer Nature, 2021-12-02) Barnes, Mallory L.; Farella, Martha M.; Scott, Russell L.; Moore, David J. P.; Ponce-Campos, Guillermo E.; Biederman, Joel A.; MacBean, Natasha; Litvak, Marcy E.; Breshears, David D.Dryland ecosystems are dominant influences on both the trend and interannual variability of the terrestrial carbon sink. Despite their importance, dryland carbon dynamics are not well-characterized by current models. Here, we present DryFlux, an upscaled product built on a dense network of eddy covariance sites in the North American Southwest. To estimate dryland gross primary productivity, we fuse in situ fluxes with remote sensing and meteorological observations using machine learning. DryFlux explicitly accounts for intra-annual variation in water availability, and accurately predicts interannual and seasonal variability in carbon uptake. Applying DryFlux globally indicates existing products may underestimate impacts of large-scale climate patterns on the interannual variability of dryland carbon uptake. We anticipate DryFlux will be an improved benchmark for earth system models in drylands, and prompt a more sensitive accounting of water limitation on the carbon cycle.Item Mineral-enriched biochar delivers enhanced nutrient recovery and carbon dioxide removal(Springer Nature, 2022-03-18) Buss, Wolfram; Wurzer, Christian; Manning, David A. C.; Rohling, Eelco J.; Borevitz, Justin; Mašek, OndřejBiochar production via biomass pyrolysis with subsequent burial in soils provides a carbon dioxide removal technology that is ready for implementation, yet uptake requires acceleration; notably, through generation of cost reductions and co-benefits. Here we find that biomass enrichment (doping) with refined minerals, mineral by-products, or ground rocks reduces carbon loss during pyrolysis, lowering carbon dioxide removal costs by 17% to US$ 80–150 t−1 CO2, with 30% savings feasible at higher biomass costs. As a co-benefit, all three additives increase plant-available nutrient levels. Doping with potassium-bearing minerals can increase both potassium and phosphorus release. Mineral doping in biochar production therefore offers carbon dioxide removal at lower costs, while alleviating global phosphorus and potassium shortages. This makes it unique among carbon dioxide removal technologies.Item Natural forest growth and human induced ecosystem disturbance influence water yield in forests(Springer Nature, 2022-06-27) Yu, Zhen; Chen, Xiuzhi; Zhou, Guoyi; Agathokleous, Evgenios; Li, Lin; Liu, Zhiyong; Wu, Jianping; Zhou, Ping; Xue, Meimei; Chen, Yuchan; Yan, Wenting; Shi, Tingting; Zhao, XiangTogether natural growth, afforestation and forest disturbance, such as felling, contribute to the dynamic nature of forests. Thus to enhance forest management, water resource management and carbon sequestration, the net effect of forest changes on water yield must be better understood. Here, we conduct a global meta-analysis of 496 watersheds over 25 years to investigate the impact of forest complexity and overall changes on water yields. We classify watersheds based on the type of human disturbance, including felling and thinning, afforestation, and absence of external disturbances. We find that the runoff coefficient (ratio of annual water yield in watershed outlet to precipitation) is more sensitive to external disturbances in forests with lower ecosystem complexity compared to forests with higher complexity. In addition, we found forest natural growth may increase runoff and lead to an increased runoff coefficient decades later. Our findings highlight the importance of nature-based forest restoration, especially in regions vulnerable to water shortage.Item Nature-based solutions in mountain catchments reduce impact of anthropogenic climate change on drought streamflow(Springer Nature, 2022-03-09) Holden, Petra B.; Rebelo, Alanna J.; Wolski, Piotr; Odoulami, Romaric C.; Lawal, Kamoru A.; Kimutai, Joyce; Nkemelang, Tiro; New, Mark G.Quantifying how well Nature-based Solutions can offset anthropogenic climate change impacts is important for adaptation planning, but has rarely been done. Here we show that a widely-applied Nature-based Solution in South Africa – invasive alien tree clearing – reduces the impact of anthropogenic climate change on drought streamflow. Using a multi-model joint-attribution of climate and landscape-vegetation states during the 2015–2017 Cape Town “Day Zero” drought, we find that anthropogenic climate change reduced streamflow by 12–29% relative to a counterfactual world with anthropogenic emissions removed. This impact on streamflow was larger than corresponding reductions in rainfall (7–15%) and reference evapotranspiration (1.7–2%). Clearing invasive alien trees could have ameliorated streamflow reductions by 3–16% points for moderate invasions levels. Preventing further invasive alien tree spread avoided potential additional reductions of 10–27% points. Total clearing could not have offset the anthropogenic climate change impact completely. Invasive alien tree clearing is an important form of catchment restoration for managing changing hydroclimatic risk, but will need to be combined with other adaptation options as climate change accelerates.Item Net greenhouse gas balance of fibre wood plantation on peat in Indonesia(Springer Nature, 2023-04-05) Deshmukh, Chandra S.; Susanto, Ari P.; Nardi, Nardi; Nurholis, Nurholis; Kurniato, Sofyan; Suardiwerianto, Yogi; Hendrizal, M.; Rhinaldy, Ade; Mahfiz, Reyzaldi E.; Desai, Ankur R.; Page, Susan E.; Cobb, Alexander R.; Hirano, Takashi; Guérin, Frédéric; Serça, Dominique; Prairie, Yves T.; Agus, Fahmuddin; Astiani, Dwi; Sabiham, Supiandi; Evans, Chris D.Tropical peatlands cycle and store large amounts of carbon in their soil and biomass1,2,3,4,5. Climate and land-use change alters greenhouse gas (GHG) fluxes of tropical peatlands, but the magnitude of these changes remains highly uncertain6,7,8,9,10,11,12,13,14,15,16,17,18,19. Here we measure net ecosystem exchanges of carbon dioxide, methane and soil nitrous oxide fluxes between October 2016 and May 2022 from Acacia crassicarpa plantation, degraded forest and intact forest within the same peat landscape, representing land-cover-change trajectories in Sumatra, Indonesia. This allows us to present a full plantation rotation GHG flux balance in a fibre wood plantation on peatland. We find that the Acacia plantation has lower GHG emissions than the degraded site with a similar average groundwater level (GWL), despite more intensive land use. The GHG emissions from the Acacia plantation over a full plantation rotation (35.2 ± 4.7 tCO2-eq ha−1 year−1, average ± standard deviation) were around two times higher than those from the intact forest (20.3 ± 3.7 tCO2-eq ha−1 year−1), but only half of the current Intergovernmental Panel on Climate Change (IPCC) Tier 1 emission factor (EF)20 for this land use. Our results can help to reduce the uncertainty in GHG emissions estimates, provide an estimate of the impact of land-use change on tropical peat and develop science-based peatland management practices as nature-based climate solutions.Item On the use of Earth Observation to support estimates of national greenhouse gas emissions and sinks for the Global stocktake process: lessons learned from ESA-CCI RECCAP2(Springer Nature, 2022-10-01) Bastos, Ana; Ciais, Phillippe; Sitch, Stephen; Aragão, Luiz O. C.; Chevallier, Frédéric; Fawcett, Dominic; Rosan, Thais M.; Saunois, Marielle; Günther, Dirk; Perugini, Lucia; Robert, Colas; Deng, Zhu; Pongratz, Julia; Ganzenmüller, Raphael; Fuchs, Richard; Winkler, Karina; Zaehle, Sönke; Albergel, ClémentThe Global Stocktake (GST), implemented by the Paris Agreement, requires rapid developments in the capabilities to quantify annual greenhouse gas (GHG) emissions and removals consistently from the global to the national scale and improvements to national GHG inventories. In particular, new capabilities are needed for accurate attribution of sources and sinks and their trends to natural and anthropogenic processes. On the one hand, this is still a major challenge as national GHG inventories follow globally harmonized methodologies based on the guidelines established by the Intergovernmental Panel on Climate Change, but these can be implemented diferently for individual countries. Moreover, in many countries the capability to systematically produce detailed and annually updated GHG inventories is still lacking. On the other hand, spatially-explicit datasets quantifying sources and sinks of carbon dioxide, methane and nitrous oxide emissions from Earth Observations (EO) are still limited by many sources of uncertainty. While national GHG inventories follow diverse methodologies depending on the availability of activity data in the diferent countries, the proposed comparison with EO-based estimates can help improve our understanding of the comparability of the estimates published by the diferent countries. Indeed, EO networks and satellite platforms have seen a massive expansion in the past decade, now covering a wide range of essential climate variables and ofering high potential to improve the quantifcation of global and regional GHG budgets and advance process understanding. Yet, there is no EO data that quantifes greenhouse gas fuxes directly, rather there are observations of variables or proxies that can be transformed into fuxes using models. Here, we report results and lessons from the ESA-CCI RECCAP2 project, whose goal was to engage with National Inventory Agencies to improve understanding about the methods used by each community to estimate sources and sinks of GHGs and to evaluate the potential for satellite and in-situ EO to improve national GHG estimates. Based on this dialogue and recent studies, we discuss the potential of EO approaches to provide estimates of GHG budgets that can be compared with those of national GHG invento ries. We outline a roadmap for implementation of an EO carbon-monitoring program that can contribute to the Paris Agreement.Item Optimizing Sampling Strategies for Near-Surface Soil Carbon Inventory: One Size Doesn’t Fit All(MDPI, 2023-03-17) Bettigole, Charles; Hanle, Juliana; Kane, Daniel A.; Pagliaro, Zoe; Kolodney, Shaylan; Szuhay, Sylvana; Chandler, Miles; Hersh, Eli; Wood, Stephen A.; Basso, Bruno; Goodwin, Douglas Jeffrey; Hardy, Shane; Wolf, Zachary; Covey, Kristofer R.Soils comprise the largest pool of terrestrial carbon yet have lost significant stocks due to human activity. Changes to land management in cropland and grazing systems present opportunities to sequester carbon in soils at large scales. Uncertainty in the magnitude of this potential impact is largely driven by the difficulties and costs associated with measuring near-surface (0–30 cm) soil carbon concentrations; a key component of soil carbon stock assessments. Many techniques exist to optimize sampling, yet few studies have compared these techniques at varying sample intensities. In this study, we performed ex-ante, high-intensity sampling for soil carbon concentrations at four farms in the eastern United States. We used post hoc Monte-Carlo bootstrapping to investigate the most efficient sampling approaches for soil carbon inventory: K-means stratification, Conditioned Latin Hypercube Sampling (cLHS), simple random, and regular grid. No two study sites displayed similar patterns across all sampling techniques, although cLHS and grid emerged as the most efficient sampling schemes across all sites and strata sizes. The number of strata chosen when using K-means stratification can have a significant impact on sample efficiency, and we caution future inventories from using small strata n, while avoiding even allocation of sample between strata. Our findings reinforce the need for adaptive sampling methodologies where initial site inventory can inform primary, robust inventory with site-specific sampling techniques.Item Organic C Fractions in Topsoil under Different Management Systems in Northeastern Brazil(MDPI, 2023-02-05) Gualberto, Adriano Venicius Santana; de Souza, Henrique; Sagrilo, Edvaldo; Araujo, Ademir Sergio Ferreira; Mendes, Lucas William; de Medeiros, Erika Valente; Pereira, Arthur Prudêncio de Araujo; da Costa, Diogo Paes; Vogado, Renato Falconeres; da Cunha, João Rodrigues; Teixeira, Marcos Lopes; Leite, Luiz Fernando CarvalhoThe conversion from native forest to other land-use systems can decline the soil organic carbon (SOC) in tropical soils. However, conservationist management could mitigate SOC losses, promoting the functioning and stability of agricultural soils. This study aimed to address the influence of conversion from native forest to different land-use systems on SOC fractions in Northeastern Brazil. Topsoil soil samples were collected in areas under pasture (PAS), no-tillage (NT1 and NT2), eucalyptus (EUC), and native forests of Cerrado in Northeastern, Brazil. Total organic C, microbial biomass (MBC), particulate (POC), and mineral-occluded organic C (MOC), as well as fulvic acids (C-FA), humic acids (C-HA), and humin (C-HUM) fractions were accessed. The results showed that land conversion maintained similar levels of humic fractions and total organic carbon (TOC) stocks in the PAS, NT1, NT2, and EUC as compared to native Cerrado. Soils with the input of permanent and diverse fresh organic material, such as NT2, PAS, and EUC, presented high levels of MBC and POC, and the lowest C-FA:TOC and C-HA:TOC ratios. The land conversion to agricultural systems that include cropping rotations associated with pasture species such as Mombasa grass and eucalyptus prevents topsoil losses of active C compartments in the Cerrado of the Brazilian Northeast. It suggests that sustainable and conservationist management should be emphasized to maintain and improve the status of soil organic C.Item Potential of land-based climate change mitigation strategies on abandoned cropland(Springer Nature, 2023-02-16) Gvein, Maren H.; Hu, Xiangping; Næss, Jan S.; Watanabe, Marcos D. B.; Cavalett, Otávio; Malbranque, Maxime; Kindermann, Georg; Cherubini, FrancescoNatural revegetation, afforestation, and lignocellulosic crops for bioenergy, possibly coupled with a developing technology like carbon capture and storage, are the most common land-based climate change mitigation options. However, they can compete for land and threaten food security or nature conservation. Using abandoned cropland for their deployment can minimize these risks, but associated potentials are unclear. Here, we compare alternative land-based mitigation options by integrating historical and future (up to 2050) abandoned cropland with site-specific biomass yields and life-cycle emissions. Considering natural revegetation in biodiversity priority areas and different measures in the remaining land can achieve a mitigation potential of 0.8–4.0 GtCO2-equivalents yr−1 (2–11% of 2021 global CO2 emissions). Afforestation generally provides larger climate benefits than bioenergy, but bioenergy with carbon capture and storage delivers the highest mitigation in most locations. Overall, these results offer refined estimates of mitigation potentials from abandoned cropland and highlight opportunities for context-specific mitigation measures.