Shihao Cui’s research while affiliated with Aarhus University and other places

Increased CH4 emissions from rewetted organic soils can undermine the climate benefits of reduced CO2 release. This is especially problematic in low-lying areas that tend to remain waterlogged and act as potential CH4 hotspots. Here we test whether burning the soil surface before rewetting can reduce CH4 emissions. Using laboratory experiments with soil cores collected from degraded farmland in Denmark, we found that rewetting organic soils following burning reduced CH4 emissions by more than 95% over a 90-day period compared to rewetting alone. The reduction was likely associated with changed soil chemistry such as increased soil carbon stability and the decrease in methanogen abundance and activity. Our results suggest that targeted burning could help suppress short-term CH4 emissions after rewetting. However, long-term field studies are needed to understand whether this effect persists and to assess potential ecological risks such as pollution runoff, before any broader field-scale implementation is considered.

Rewetting drained peatlands is a promising strategy for mitigating carbon dioxide (CO2) emissions, transforming these areas from carbon sources to sinks. Despite the well-known climate benefits, practical implementation is often hampered by conflicts between environmental goals and farmers’ economic interests. Identifying optimal rewetting locations that maximize greenhouse gas (GHG) reduction while minimizing agricultural disruption is crucial to advancing this process. However, there is currently limited scientific evidence to guide these decisions. To identify “low-hanging fruits”, 12 sites were selected for 4-month incubations to investigate the effects of four land uses (grass-cut, grass-graze, arable, and unmanaged) on CO2 and methane (CH4) emissions postrewetting. Results showed that unmanaged sites exhibited the highest potential for GHG reduction (2015 mg CO2-eq m–2 day–1, 89.9%), followed by grass-graze, grass-cut, and arable sites, reflecting a gradient of management intensity. These insights suggest that prioritizing rewetting of unmanaged areas while delaying interventions on arable lands could yield greater climate benefits and enhance farmers’ acceptance. Additionally, emission variability across sites was linked to soil properties, indicating that soils with a higher organic carbon content (for greater CO2 reduction) and lower bacterial diversity (for reduced CH4 production) offer the greatest GHG reduction potential. This study provides crucial scientific evidence to guide targeted peatland rewetting efforts, supporting net-zero emission goals.

Methane fluxes (FCH4) vary significantly across wetland ecosystems due to complex mechanisms, challenging accurate estimations. The interactions among environmental drivers, while crucial in regulating FCH4, have not been well understood. Here, the interactive effects of six environmental drivers on FCH4 were first analyzed using 396,322 half-hourly measurements from 22 sites across various wetland types and climate zones. Results reveal that soil temperature, latent heat turbulent flux, and ecosystem respiration primarily exerted direct effects on FCH4, while air temperature and gross primary productivity mainly exerted indirect effects by interacting with other drivers. Significant spatial variability in FCH4 regulatory mechanisms was highlighted, with different drivers demonstrated varying direct, indirect, and total effects among sites. This spatial variability was then linked to site-specific annual-average air temperature (17.7%) and water table (9.0%) conditions, allowing the categorization of CH4 sources into four groups with identified critical drivers. An improved estimation approach using a random forest model with three critical drivers was consequently proposed, offering accurate FCH4 predictions with fewer input requirements. By explicitly accounting for environmental interactions and interpreting spatial variability, this study enhances our understanding of the mechanisms regulating CH4 emissions, contributing to more efficient modeling and estimation of wetland FCH4.

The efficiency of direct electron flow from electron donors to electron acceptors in redox reactions is significantly influenced by the spatial separation of these components. Geobatteries, a class of redox-active substances naturally present in soil–water systems, act as electron reservoirs, reversibly donating, storing, and accepting electrons. This capability allows the temporal and spatial decoupling of redox half-reactions, providing a flexible electron transfer mechanism. In this review, we systematically examine the critical role of geobatteries in influencing electron transfer and utilization in environmental biogeochemical processes. Typical redox-active centers within geobatteries, such as quinone-like moieties, nitrogen- and sulfur-containing groups, and variable-valent metals, possess the potential to repeatedly charge and discharge. Various characterization techniques, ranging from qualitative methods like elemental analysis, imaging, and spectroscopy, to quantitative techniques such as chemical, spectroscopic, and electrochemical methods, have been developed to evaluate this reversible electron transfer capacity. Additionally, current research on the ecological and environmental significance of geobatteries extends beyond natural soil–water systems (e.g., soil carbon cycle) to engineered systems such as water treatment (e.g., nitrogen removal) and waste management (e.g., anaerobic digestion). Despite these advancements, challenges such as the complexity of environmental systems, difficulties in accurately quantifying electron exchange capacity, and scaling-up issues must be addressed to fully unlock their potential. This review underscores both the promise and challenges associated with geobatteries in responding to environmental issues, such as climate change and pollutant transformation.