Carbon Balance and Management最新文献

Background

This study evaluated the effects of grazing management practices, topographic position, and land cover types on mineral-associated organic carbon (MAOC) and particulate organic carbon (POC) in a semi-arid rangeland of Kenya. Research was conducted at Mpala Research Centre (controlled grazing) and Ilmotiok Community Group Ranch (continuous grazing) in Laikipia County. A factorial experimental design with a split-plot arrangement was used in this study. Grazing management practices (controlled and continuous grazing) and topographic positions (midslope, foot slope, and bottomland) were assigned to the main plots, while land cover types (bare ground, grass patches, and tree mosaics) were designated as subplots. Soil samples were collected at 10 cm intervals, 0–10 cm, 10–20 cm, and 20–30 cm depth for MAOC and POC analysis. Data analysis was done using R software, where nonparametric tests were done when the assumptions of normality and homogeneity of variance were violated.

Results

Controlled grazing resulted in higher MAOC (0.361%) and POC (0.683%) compared to continuous grazing (0.352% and 0.548%, respectively), indicating an increase of 2.56% in MAOC and 24.64% in POC under controlled grazing. This can largely be attributed to improved vegetation recovery, especially in midslope areas. The highest MAOC (0.367%) was found in the bottomland, likely due to reduced erosion and improved water retention. The midslope and foot slope positions had lower MAOC means of 0.358% and 0.344%, respectively. Depth analysis showed peak MAOC at 20 cm (0.390%), with controlled grazing resulting in better carbon retention at 30 cm. Similarly, controlled grazing yielded a mean POC of 0.683% versus 0.548% for continuous grazing, with bottomland having the highest POC of 0.754%. A Kruskal‒Wallis tests showed significant differences in MAOC and POC across land cover types (χ² = 42.701, p < 0.001 for MAOC, and χ² = 83.53, p < 0.001 for POC), with tree mosaics and bare land contributing most to POC and MAOC, respectively.

Conclusions

These findings highlight the beneficial role of controlled grazing and diverse land cover in enhancing soil carbon storage. To promote sustainable rangeland management, it is recommended that rangeland managers adopt controlled grazing practices and allow diverse land cover types, such as tree mosaics, to increase carbon sequestration and ecosystem resilience.

As the global greenhouse effect intensifies, the emission and balance of greenhouse gases, particularly carbon dioxide (CO₂), have become crucial for achieving global carbon neutrality. Volcanic geothermal regions, as major natural sources of carbon emissions, release substantial volume of greenhouse gases into the atmosphere in various ways including volcanic eruptions, soil microseepages, vents, and hot springs. Among these, soil microseepages are particularly important due to their widespread and persistent nature. However, the geochemical dynamics of CO₂ release from soil microseepage in volcanic regions remain poorly understood. In this study, we propose a novel CO₂ release model employing computational fluid dynamics (CFD) to model CO₂ emissions from soil microseepage in volcanic regions. Our results provide important insights as follows: (1) Low porosity in subsurface strata inhibits CO₂ penetration, while well-developed underground cracks and channels enhance release rates. (2) Favorable gas pathways enable CO₂ to penetrate dense layers, and migrate upward, with migration patterns influenced by gas source pressure, temperature, and soil permeability. Slowing vertical migration increases horizontal diffusion and expands the effective surface release area. (3) Surface release is also influenced by external factors like wind speed, though these do not significantly affect underground seepage. (4) To improve the accuracy of CO₂ flux measurements using the closed chamber method, it is recommended to reverse the initial slope of the CO₂ concentration-time curve. This study provides critical data to enhance global carbon budget assessments and support efforts towards carbon neutrality.

Amid profound shifts in the global energy landscape, increasing attention is being paid to the causal relationships among geopolitical risks, government governance, and energy transition. Based on data covering 39 countries from 2002 to 2020, this study explores the long-term causal relationships between geopolitical risks, governance quality, and energy transition. The analysis applies cross-sectional dependence and slope heterogeneity tests, the CADF unit root test, second-generation cointegration methods, Pooled Mean Group (PMG) estimation, Method of Moments Quantile Regression (MMQR), and Granger causality tests. The results yield three key findings. Firstly, governance quality is negatively associated with energy transition, while geopolitical risks have a positive effect. Secondly, MMQR shows that these effects are more pronounced at higher quantiles of the energy transition distribution, meaning countries further along in the transition process are more responsive to changes in governance and geopolitical conditions. Thirdly, heterogeneity tests indicate that geopolitical risks exhibit a more pronounced long-term positive contribution to energy transition in economically high-growth and highly urbanized countries. These findings challenge dominant assumptions in the literature, particularly the presumed uniformly positive role of governance. The results suggest that the influence of governance and geopolitical risks on energy transition is context-dependent and nonlinear. This study provides new empirical evidence and theoretical insights to inform energy policy under geopolitical uncertainty.

The magnitude and distribution of organic carbon (OC) transport from the terrestrial surface to the oceans is not well understood on a global scale. This hinders our understanding of terrestrial and marine carbon cycles. In this study, we determined the characteristics of OC flux. Our results showed that approximately 420 Tg C/yr of OC are transported from the terrestrial surface to the oceans, including 220 Tg C/yr of particulate organic carbon (POC) and 200 Tg C/yr of dissolved organic carbon (DOC). Asia, with only 32.46% of the basin area, accounts for 57.65% of the total POC flux, while North America, with only 17.52% of the basin area, accounts for 37.51% of DOC flux. Of these, the Pacific receives 48% of the total POC flux, and the Atlantic receives 46% of the total DOC flux. Five key zones are diagnosed and identified, in which latitudes between 5° N and 20° S contributed 72.76% of the global OC flux. Such insights directly reveal global riverine OC flux, which helps us to comprehensively understand the terrestrial and marine carbon cycles.

Accurately identifying ecological compensation (EC) regions and establishing clear compensation criteria are essential for promoting carbon sequestration, mitigating ecological degradation, and supporting equitable resource allocation. In this study, ecological modeling combined with hotspot analysis was applied to quantify the spatial mismatch between ecosystem service (ES) supply and demand on the Tibetan Plateau (TP) in 2020. We introduced the concept of comparative ecological radiation force (CERF) to characterize the spatial flow of ESs and to estimate the total compensation required to balance these flows. Our results highlight that the value of carbon sequestration, represented by net primary production (NPP), reached 1.21 × 10⁶ CNY, alongside other key services such as soil conservation (SC) (284.69 × 10⁶ CNY), water yield (WY) (44.99 × 10⁶ CNY) and food supply (FS) (20.81 × 10⁶ CNY). The directional analysis of service flows revealed that NPP, along with SC and WY, predominantly flowed from east to west, while FS exhibited a north-to-south pattern. Notably, NPP received only 0.16% of the total ecological compensation, in contrast to 95.42% for SC, 4.21% for WY, and 0.21% for FS. This study provides an integrated framework for aligning EC strategies with carbon management goals, offering insights to support carbon neutrality efforts and ecosystem restoration on the TP.

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.

Background

In the context of mitigating global warming and promoting sustainable development, the scientific and effective assessment of the global carbon total factor productivity (CTFP) is essential for slowing global warming and fostering green transformation and coordinated development at both the global and regional levels.

Methods

This study constructs a CTFP evaluation index system and, for the first time, employs the SBM-DDF-GML productivity index model to measure the CTFP of 137 countries worldwide from 1991 to 2019. This model combines a directional distance function with the global Malmquist–Luenberger index to achieve precision in efficiency measurement and intertemporal comparability. It effectively resolves the problems of estimation bias and time dimension inconsistency caused by the radial assumption in traditional radial models. The spatial characteristics, regional disparities, and sources of these disparities in the CTFP are examined using ArcGIS and the Dagum Gini coefficient method. The σ-convergence and β-convergence models are used to investigate the influencing factors and convergence characteristics of the CTFP.

Results

The findings reveal that (1) the global CTFP exhibited an overall upward trend with fluctuations over the sample period, with technological progress being the primary driving force. (2) There are significant gradient disparities in the global CTFP, primarily stemming from supervariable density, followed by intraregional and interregional differences, and these disparities are expanding. (3) While there is no evident σ-convergence in the global CTFP and CTFP of the four major regions, there are significant absolute and conditional β-convergence trends.

Conclusion

Based on the research results, this paper proposes specific strategies to promote the global development of CTFP. These include strengthening technology R&D to improve CTFP, encouraging regional convergence to reduce development disparities, and enhancing the dynamic monitoring and evaluation system to foster growth and equity. This study provides empirical support and a decision-making basis for the coordinated development of the global economy and environment, contributing to advancing global green, low-carbon, and sustainable development.

Climate change, fire suppression, and human encroachment contribute to increasingly intense forest fires in the Western United States, releasing hundreds of millions of metric tons (MMT) CO₂/year. Proactive fire-risk reduction treatments coordinated by the US Forest Service (USFS) typically include thinning and burning (or in situ decay) of thinned products and may require thinning on ~ 28 million hectares of public and private land over the next decade. Assuming thinning of only small (~ 30 cm diameter) trees within 0.8 km of existing roads on slopes gentler than a 40% grade, this will produce ~ 1,100 MMT of thinned wood, which, if burned or left to decay, will release ~ 2000 MMT CO₂. Here we evaluate the life cycle emissions of an alternative fate, burial in anoxic wood vaults. We performed a life cycle analysis (LCA) to assess potential net emissions reductions, considering site clearing, transport, site preparation and post-burial decay. We used Monte-Carlo simulations to estimate emissions uncertainty and identify key parameters influencing carbon removal efficiency.

We find wood vaults will decrease emissions relative to current practice by a mean of 66% if wood is transported 100 km, and by 38% at a transport distance of 500 km. If the USFS is able to implement the proposed Wildfire Crisis Strategy, and all of the wood from thinning were buried in wood vaults within 100–500 km of the thinning sites, our results suggest these vaults would thus sequester between ~ 40–140 MMT CO₂/yr over a decade. This annual figure represents ~ 6–12% of 2021 energy-related emissions in the contiguous Western United States. Harvesting thinned products only from gentler (< 20%) slopes within shorter distances from roads (304 m) would result in a greenhouse gas savings equivalent to 3–6% of 2021 Western State emissions. However, these results depend heavily on parameters related to wood decay and post-decay methane emissions that are relatively poorly constrained.

These results suggest wood vaults are a promising emissions-reduction strategy, but challenges remain. It is not clear that the USFS has the resources to manage the additional ~ 20 million hectares targeted for forest thinning. Biogeochemically, the importance of rates of wood decay within the vault, and the fraction of methane generated that escapes the vault, are poorly constrained parameters. Their estimation will be important for narrowing uncertainty in estimates of life cycle emissions. Nevertheless, our analysis suggests wood vaults are a promising, low-tech, ready-to-deploy emissions reduction strategy in places where forest management incl