This week’s publication highlights relate to enhanced rock weathering, forestation, soil carbon sequestration and marine CDR.
Lithium Isotopes Reveal Enhanced Weathering Fluxes in North America during the Paleocene-Eocene Thermal Maximum
Abstract
Silicate weathering regulates Earth’s long-term climate by removing atmospheric CO2. Understanding changes in weathering regimes and rates is key to predicting climate response time scales. We investigated the reactivity of the North American source-to-sink system and the chemical weathering regime during the Paleocene–Eocene Thermal Maximum (PETM). We measured the detrital lithium isotope composition (δ7Li) in a deep-marine sediment core from the Gulf of Mexico, tracking changes in the formation of clay minerals, alongside neodymium isotopes (εNd), to constrain sediment provenance. We find a buffered negative δ7Li excursion during the PETM body, likely reflecting the mixing of neoformed and reworked clays from continental floodplains, followed by a stronger negative δ7Li excursion during the recovery phase. This pattern aligns with the continental Bighorn Basin (Wyoming, USA) δ7Li record, indicating rapid propagation of enhanced weathering and erosion fluxes in response to the PETM, which would have contributed to efficient CO2 drawdown.
Rocio Jaimes-Gutierrez et al. (2025) Lithium Isotopes Reveal Enhanced Weathering Fluxes in North America during the Paleocene-Eocene Thermal Maximum 54(3) Geology.
Read the full paper here: Lithium Isotopes Reveal Enhanced Weathering Fluxes in North America during the Paleocene-Eocene Thermal Maximum I Geology.
Long-Term Moderate Warming Shifts Soil Carbon Cycling but Maintains Carbon Sinks in a Subtropical Forest
Abstract
The lack of long-term experimental evidence on how multi-phase plant-soil interactions shape soil organic carbon (SOC) responses to warming—especially in (sub)tropical forests—hinders accurate predictions of carbon-climate feedbacks and the development of forest-based mitigation strategies. Here, we report findings from a 9-year passive ecosystem warming experiment (+0°C, +1.0°C, and +2.1°C) in a subtropical forest. We found that SOC exhibited a two-phase response distinct from previous soil-only warming experiments: initial loss (years 1–4) due to reduced topsoil mineral-associated organic carbon, followed by accumulation (years 6–9) attributed to sustained plant carbon inputs and microbial thermal adjustments that increased particulate organic carbon. Our findings indicate that some subtropical forests could continue to accumulate SOC under future moderate warming, albeit with distinct accumulation patterns of different SOC fractions across soil layers. Changes in plant-soil interactions mediating SOC fate under warming should receive increased conceptual and modeling attention moving forward.
Xujun Liu et al. (2026) Long-Term Moderate Warming Shifts Soil Carbon Cycling but Maintains Carbon Sinks in a Subtropical Forest 9(1) One Earth.
Read the full paper here: Long-Term Moderate Warming Shifts Soil Carbon Cycling but Maintains Carbon Sinks in a Subtropical Forest I One Earth.
Mixed Forestation Outperforms Pure Stands in Soil Carbon Sequestration and Stability
Abstract
Forestation is a pivotal nature-based strategy for enhancing soil organic carbon (SOC) sequestration, yet the differential impacts of pure versus mixed-species plantations on SOC fractions and stability remain poorly quantified at a global scale. To address this knowledge gap, we performed a meta-analysis of 4052 observations from 102 sites and showed that mixed forestation significantly increases SOC, particulate organic carbon (POC), and mineral-associated organic carbon (MAOC) by 64.3%, 86.9%, and 65.3%, respectively, whereas pure forestation enhances SOC and POC but has no significant impact on MAOC. Critically, pure forestation reduced the MAOC:POC ratio—a key indicator of SOC stability—by 24.9%, while mixed forestation maintained or enhanced it. Prior land use type was the dominant regulator of SOC fraction responses, with plantation age further moderating SOC accrual and stability. Mixed forestation also promoted greater soil nitrogen, microbial biomass, and dissolved organic carbon, supporting MAOC formation and SOC stability. Our results demonstrate that mixed forestation simultaneously enhances SOC storage and stability, offering a more resilient pathway for terrestrial carbon sequestration under global change. These findings underscore the need to prioritize mixed-species plantations in reforestation policies to achieve climate mitigation and ecosystem restoration goals.
Xianyang Shu et al. (2026) Mixed Forestation Outperforms Pure Stands in Soil Carbon Sequestration and Stability 32(3) Global Change Biology.
Read the full paper here: Mixed Forestation Outperforms Pure Stands in Soil Carbon Sequestration and Stability I Global Change Biology.
Evolutionary History Shapes Soil pH Following Forestation at Global Scales: A Meta-Analysis
Abstract
Understanding soil pH and its post-forestation changes is crucial for predicting soil biogeochemical processes. While previous studies have focused on environmental factors influencing soil pH after forestation, they have often neglected the functional traits of forested tree species, especially the evolutionary history. We compiled a global dataset of post-forestation soil pH, including 2139 observations across 210 tree species. Globally, soil pH decreased significantly after forestation, with an average decrease of 0.20 units. The post-forestation soil pH exhibited distinct functional patterns among tree species and displayed significant phylogenetic signals, whereas soil pH change after forestation showed neither significant functional patterns nor phylogenetic signals. Our study revealed that, at the global scale, variation was by phylogeny, species and environmental factors explained 29.5%, 27.7%, and 19.0% of post-forestation soil pH, respectively, and the three proportions of explained variation are, respectively, 11.3%, 37.6% and 20.8% for soil pH change. Random forest identified evolutionary history, climate, and SOC as key regulators of post-forestation soil pH, whereas SOC, climate, and topography primarily drove soil pH change after forestation. This study demonstrates that evolutionary history plays a crucial role in global post-forestation soil acidification, directly shaping post-forestation soil pH. These findings provide global evidence that forested tree species constrain soil biogeochemical processes and functions.
Liankang Yang et al. (2026) Evolutionary History Shapes Soil pH Following Forestation at Global Scales: A Meta-Analysis 611 (123725) Forest Ecology and Management.
Read the full paper here: Evolutionary History Shapes Soil pH Following Forestation at Global Scales: A Meta-Analysis I Forest Ecology and Management.
Marginal Seas as Potential Sinks for Refractory Carbon
Abstract
The Yellow Sea (YS) and East China Sea (ECS) are marginal seas in the Northwestern Pacific that receive large amounts of aged, terrestrial organic matter. In this study, we measured dissolved organic carbon (DOC) concentrations and radiocarbon contents (Δ14C) in these seas during summer and autumn, extending a previous winter study to provide a more comprehensive understanding of the DOC cycle, including its sources and removal. The significant negative correlation between DOC concentrations or Δ14C values and salinity shows that vertical and horizontal water mass mixing between coastal waters and the water intruding to the site from the Northwestern Pacific is the primary control on the distribution of DOC. The Δ14C values and the inverse of DOC concentrations show significant negative correlation, suggesting that marine primary production is the dominant DOC source in this region. However, deviations from this correlation imply inputs of aged DOC. Although freshwater input is highest in summer, the effects of aged DOC are greater in autumn and winter. Terrestrial organic matter delivered by rivers is rapidly degraded, and this process likely stimulates marine primary production. In addition, large seasonal differences in Δ14C values in Kuroshio-derived waters indicate significant removal of marine refractory DOC on the continental shelf. The results show that continental shelves have a key role in the removal of terrestrial and marine refractory DOC.
Yeongjin Ryu et al. (2025) Marginal Seas as Potential Sinks for Refractory Carbon 71(1) Limnology and Oceanography.
Read the full paper here: Marginal Seas as Potential Sinks for Refractory Carbon I Limnology and Oceanography.