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Tropical forests account for over 50% of the global terrestrial carbon sink, but climate change threatens to alter the carbon balance of these ecosystems. We show that warming and drying of tropical forest soils may increase soil carbon vulnerability, by increasing degradation of older carbon. In situ whole-profile heating by 4 °C and 50% throughfall exclusion each increased the average radiocarbon age of soil CO2 efflux by ~2–3 years, but the mechanisms underlying this shift differed. Warming accelerated decomposition of older carbon as increased CO2 emissions depleted newer carbon. Drying suppressed decomposition of newer carbon inputs and decreased soil CO2 emissions, thereby increasing contributions of older carbon to CO2 efflux. These findings imply that both warming and drying, by accelerating the loss of older soil carbon or reducing the incorporation of fresh carbon inputs, will exacerbate soil carbon losses and negatively impact carbon storage in tropical forests under climate change. Climate change threatens to alter the carbon balance of tropical forests. Increases in the age of carbon in soil CO2 emissions with experimental warming or drying suggest that climate change will exacerbate soil carbon losses in tropical forests. [ABSTRACT FROM AUTHOR]

Understanding the alterations in soil microbial communities in response to climate warming and their controls over soil carbon (C) processes is crucial for projecting permafrost C-climate feedback. However, previous studies have mainly focused on microorganism-mediated soil C release, and little is known about whether and how climate warming affects microbial anabolism and the subsequent C input in permafrost regions. Here, based on a more than half-decade of in situ warming experiment, we show that compared with ambient control, warming significantly reduces microbial C use efficiency and enhances microbial network complexity, which promotes soil heterotrophic respiration. Meanwhile, microbial necromass markedly accumulates under warming likely due to preferential microbial decomposition of plant-derived C, further leading to the increase in mineral-associated organic C. Altogether, these results demonstrate dual roles of microbes in affecting soil C release and stabilization, implying that permafrost C-climate feedback would weaken over time with dampened response of microbial respiration and increased proportion of stable C pool. Understanding microbial responses to climate warming is crucial for projecting permafrost carbon-climate feedback. Here, the authors reveal dual microbial roles in promoting both soil carbon release and stable soil carbon accrual under warming scenario. [ABSTRACT FROM AUTHOR]

Aims: Plastic film mulching (PFM) induces strong soil warming and alters the water balance, thereby influencing microbial activities, particularly those associated with nitrogen (N) transformations, including mineralization from soil organic matter. The impact of PFM on interactions between N fate and soil N transformations remains unclear. Methods: We investigated the complex interplay of soil N transformation processes through 15N labeling and tracing, analyzing N availability and N fate in the PFM-covered soil compared with a non-mulched flat soil (control). Results: PFM reduced gross N mineralization and nitrification rates by 20–28% and increased microbial gross N immobilization rates. In the PFM-covered soil, maize N uptake and N accumulation (up to 80 cm depth) increased by 19% and 127%, respectively, compared with the control soil. PFM effectively mitigated N leaching and reduced N2O and NH3 gaseous emissions (by 32 kg N ha−1). During the early stages of maize growth, the PFM increased N availability in soil owing to accelerated rates of gross N mineralization from soil organic matter and nitrification, which in turn increased N uptake by maize plants and microorganisms. PFM effectively mitigated gaseous N emissions and N leaching, increasing N retention in soil and raising N use efficiency. Despite gross N mineralization and nitrification rates were reduced in the late stages of maize growth, PFM-covered soil maintained high N availability by reducing N leaching and microbial N immobilization. This contributed to raised N uptake and increased maize yields. Conclusion: PFM altered soil N transformation processes, including gross N mineralization from soil organic matter, nitrification, and immobilization by microorganisms, leading to increased N availability, maize N uptake, soil N retention, and reduced N losses. Concept of N transformation and fate in soil with and without plastic film mulch (PFM) planting system describing the mechanisms of N supply and N retention. The units are in kg N ha−1 per maize growth period. Control, soil without film mulching; PFM, soil under plastic film mulch [ABSTRACT FROM AUTHOR]

Tree‐mycorrhizal associations are associated with patterns in nitrogen (N) availability and soil organic matter storage; however, we still lack a mechanistic understanding of what tree and fungal traits drive these patterns and how they will respond to global changes in soil N availability. To address this knowledge gap, we investigated how arbuscular mycorrhizal (AM)‐ and ectomycorrhizal (EcM)‐associated seedlings alter rhizodeposition in response to increased seedling inorganic N acquisition. We grew four species each of EcM and AM seedlings from forests of the eastern United States in a continuously 13C‐labeled atmosphere within an environmentally controlled chamber and subjected to three levels of 15N‐labeled fertilizer. We traced seedling 15N uptake from, and 13C‐labeled inputs (net rhizodeposition) into, root‐excluded or ‐included soil over a 5‐month growing season. N uptake by seedlings was positively related to rhizodeposition for EcM‐ but not AM‐associated seedlings in root‐included soils. Despite this contrast in rhizodeposition, there was no difference in soil C storage between mycorrhizal types over the course of the experiment. Instead root‐inclusive soils lost C, while root‐exclusive soils gained C. Our findings suggest that mycorrhizal associations mediate tree belowground C investment in response to inorganic N availability, but these differences do not affect C storage. Continued soil warming and N deposition under global change will increase soil inorganic N availability and our seedling results indicate this could lead to greater belowground C investment by EcM‐associated trees. This potential for less efficient N uptake by EcM‐trees could contribute to AM‐tree success and a shift toward more AM‐dominated temperate forests. [ABSTRACT FROM AUTHOR]

Prescribed burning is a management tool used for both management of fuel loads and for ecological purposes across fire prone areas. While in temperate areas wildfires usually occur during the hottest summer months, prescribed burns are generally conducted in autumn and spring, when conditions are more suitable for controlling fire. Orchids maintain avoidance mechanisms, such as persisting as dormant tubers during the predominant fire season, and therefore may be at risk from prescribed burns occurring during their active life cycle period. Using a glasshouse experiment, we investigated the impacts of fire season on the Australian orchid species Pterostylis curta. This approach allowed us to i) implement seasonal burns and relate impacts to quantifiable above and belowground life cycle stages of the study species, ii) isolate and assess the role of smoke, and iii) control for fire intensity and life stage of the study species at each of the treatment levels to enable robust comparison focused on fire season effects. We found that late autumn burns caused complete failure of a cohort in our glasshouse study. Heat alone was not the driver of tuber mortality, because soil heating was similar across all burn seasons, and plants burnt in the three other seasons were able to re-emerge strongly in the growing season after fire. Furthermore, a lack of post-fire emergence was due to tuber mortality, not dormancy. Our results highlight that there is likely an interaction between fire-related heat and the life cycle stage at which burning occurs, especially replacement tuber initiation, that drives post-fire demography. We show that orchids like P. curta had the lowest risk of negative impacts when burnt in the later stages of their growing season, and that an understanding of finer-scale phenological cycles can inform more robust fire management of orchid species. [ABSTRACT FROM AUTHOR]

Background Aims Methods Results Conclusions The current transformation of the entire energy system leads to a large‐scale expansion of extra‐high‐voltage underground transmission lines (UTL). Knowledge of the impact on soil temperature and soil moisture dynamics is fundamental for environmental evaluation.We investigated the impact of an existing 320 kV underground cable in continuous operation on soil temperature and moisture dynamics.A soil‐monitoring programme was established at four study sites in Western Germany. Data were continuously recorded in soil up to 120 cm depth using soil sensors over a period of 1 year.Soil warming was in a range of 0.6 K in the topsoil, approx. 1–1.3 K in the rooting zone and 1.7 K in the subsoil at 120 cm depth and was restricted mainly to the immediate vicinity of the cable route. Likewise, the impact on soil moisture dynamics was on average in a range of −1.00 wt.‐% in 0–60 cm depth and −2.45 wt. 2‐% in the subsoil relative to control. Although at a calculated maximum load capacity of 100% in regular operation, soil warming might remain moderate, with 1.5 K in the topsoil, 2.3–3.1 K in the rooting zone and 4.1 K in the subsoil.It is assumed that the reasons for the low‐to‐moderate influence of the UTL are to be found in the operational cable load (on average 65%), heat loss of cables (approx. 12 W m−1 per cable) and the quality of the imbedding material for the cables. [ABSTRACT FROM AUTHOR]

In mid-June to July 2023, North China witnessed extreme heatwaves, marked by intense near-surface warming with an advanced seasonal cycle of local air temperature. An unconventional upper-tropospheric cold vortex in early June, deviating from conventional "heat dome" patterns, preceded the heatwave extremes. The zonal SSTA gradient in Indo-Pacific warm pool initially suppressed Indian summer monsoon convection, which stimulated the cold vortex around North China via a tropical-extratropical teleconnection. This anomaly intensified the air-land thermal contrast, leading to increased sensible heating and reduced soil moisture in situ. The drier soil conditions maintained and further augmented sensible heating, escalating surface air temperature, and culminating in extraordinary heatwaves. The air column was then destabilized to mitigate the upper-level cold vortex. Historical records corroborate the extremity of the air-sea interactions in 2023. The ECMWF real-time subseasonal-to-seasonal (S2S) forecasts successfully capture the air-land feedback in both cold vortex and heatwave stages, albeit with an underestimation of heatwave intensity due to biases in soil moisture anomalies. Consequently, the initial cold vortex condition and air-land-sea interactions yield S2S predictability to the historic 2023 heatwaves in North China. [ABSTRACT FROM AUTHOR]

In this paper, we used data from 42 soil temperature observation sites in permafrost regions throughout the Northern Hemisphere to analyze the characteristics and variability in soil temperature. The observation data were used to evaluate soil temperature simulations at different depths from 10 CMIP6 models in the permafrost region of the Northern Hemisphere. The results showed that the annual average soil temperature in the permafrost regions in the Northern Hemisphere gradually decreased with increasing latitude, and the soil temperature gradually decreased with depth. The average soil temperatures at different depths were mainly concentrated around 0 °C. The 10 CMIP6 models performed well in simulating soil temperature, but most models tended to underestimate temperatures compared to the measured values. Overall, the CESM2 model yielded the best simulation results, whereas the CNRM-CM6-1 model performed the worst. The change trends in annual average soil temperature across the 42 sites ranged from −0.17 °C/10a to 0.41 °C/10a from 1900 to 2014, the closer to the Arctic, the faster the soil warming rate. The rate of soil temperature change also varied at different depths between 1900–2014 and 1980–2014. The rate of soil temperature change from 1980 to 2014 was approximately three times greater than that from 1900 to 2014. [ABSTRACT FROM AUTHOR]

Affected by climate warming and anthropogenic disturbances, the thermo-mechanical stability of warm and ice-rich frozen ground along the Qinghai–Tibet Railway (QTR) is continuously decreasing, and melting subsidence damage to existing warm frozen soil (WFS) embankments is constantly occurring, thus seriously affecting the stability and safety of the existing WFS embankments. In this study, in order to solve the problems associated with the melting settlement of existing WFS embankments, a novel reinforcement technology for ground improvement, called an inclined soil–cement continuous mixing wall (ISCW), is proposed to reinforce embankments in warm and ice-rich permafrost regions. A numerical simulation of a finite element model was conducted to study the freeze–thaw process and evaluate the stabilization effects of the ISCW on an existing WFS embankment of the QTR. The numerical investigations revealed that the ISCW can efficiently reduce the melt settlement in the existing WFS embankment, as well as increase the bearing capacity of the existing WFS embankment, making it favorable for improving the bearing ability of composite foundations. The present investigation breaks through the traditional ideas of "active cooling" and "passive protection" and provides valuable guidelines for the choice of engineering supporting techniques to stabilize existing WFS embankments along the QTR. [ABSTRACT FROM AUTHOR]

Thicker snow cover in permafrost areas causes deeper active layers and thaw subsidence, which alter local hydrology and may amplify the loss of soil carbon. However, the potential for changes in snow cover and surface runoff to mobilize permafrost carbon remains poorly quantified. In this study, we show that a snow fence experiment on High‐Arctic Svalbard inadvertently led to surface subsidence through warming, and extensive downstream erosion due to increased surface runoff. Within a decade of artificially raised snow depths, several ice wedges collapsed, forming a 50 m long and 1.5 m deep thermo‐erosion gully in the landscape. We estimate that 1.1–3.3 tons C may have eroded, and that the gully is a hotspot for processing of mobilized aquatic carbon. Our results show that interactions among snow, runoff and permafrost thaw form an important driver of soil carbon loss, highlighting the need for improved model representation. Plain Language Summary: Snow cover is steadily disappearing as a result of climate change, but in areas that remain below 0°C we can still expect an increase in snow depth in the middle of winter. Since snow acts akin to a blanket, this warms the soil and accelerates the thaw of permafrost—thereby potentially contributing to carbon release from these frozen soils. Ice wedges, which are typical for permafrost landscapes, are particularly vulnerable to thaw because they hold a large amount of ice. When this ice melts, the surface sinks down, and soil carbon may be lost. In this study, we show how experimentally raised snow cover triggered the collapse of several ice wedges, not only through a warming effect of the snow but also due to an increase in the flow of water through the ice wedge network. As a result, we estimate that 1.1–3.3 tons of carbon were removed from this location, of which a portion could have entered the atmosphere as CO2. We emphasize the importance of studying the interactions among snow, runoff, and permafrost thaw to better understand how this may affect the release of greenhouse gases to the atmosphere. Key Points: A decade of raised snow depths led to strong local thaw subsidence, while increased runoff triggered the downstream collapse of ice wedgesThe abrupt thaw process mobilized about 1.1–3.3 tons of soil organic carbon in total, and dissolved organic carbon was degraded in the thermo‐erosion gullyFeedbacks linking changes in snow cover, surface drainage, and permafrost thaw are important drivers of thermokarst and soil carbon loss [ABSTRACT FROM AUTHOR]

The continuous growth of the world's population and the escalating demand for food raise serious concerns about the future of agriculture. According to FAO's estimates, agricultural product demand is expected to rise by 60% by 2030. However, the increasing use of chemical fertilizers has shown adverse effects on the environment and living organisms. In this context, biofertilizers offer a promising alternative to hazardous chemicals, supporting agricultural sustainability. Biofertilizers are known for their eco-friendly, non-toxic, and cost-effective nature, contributing to soil health, structure, and biodiversity preservation. Nevertheless, they face challenges, including poor shelf-life, on-field stability, sensitivity to fluctuating environmental conditions (such as temperature, radiation, and pH), limitations in long-term use, scarcity of beneficial bacterial strains, susceptibility to desiccation, and high required doses for large coverage areas. Commercially available microbe-based biofertilizers have not always met expectations in field conditions due to various reasons. While there have been advancements in biofertilizers to improve efficiency and popularity among farmers, the need to explore next-generation biofertilizers remains essential. This review primarily focuses on advanced and next-generation biofertilizers, such as PGPB (Plant Growth-Promoting Bacteria), fungal biofertilizers, nanobiofertilizers, and biofilm biofertilizers, aiming to address these challenges and propel sustainable agriculture forward. Highlights: Biofertilizers offer eco-friendly alternatives for sustainable agriculture. Advanced research improves manufacturing and application techniques. Novel microbial strains target specific nutrients. Biotechnological advancements enhance nutrient mobilization and stress tolerance. Key research priorities include selecting efficient biofertilizers and studying microbiological survival in stressed soil environments. [ABSTRACT FROM AUTHOR]

There are still great uncertainties about effects of climate warming and no-tillage on soil carbon, nitrogen, phosphorus and potassium contents and pH in alpine farmlands. A warming (control; daytime warming, DW; nighttime warming, NW; all-day warming, DW + NW) and no-tillage (no-tillage vs. tillage) experiment was conducted in an alpine farmland of the Lhasa, Xizang since 2015. Soil organic carbon, total nitrogen, total phosphorus, total potassium (TK), available nitrogen, available phosphorus, available potassium, dissolved organic carbon (DOC), active organic carbon, particulate organic carbon (POC), light fraction organic carbon, and heavy fraction organic carbon contents and pH at four depths (0–5, 5–15, 15–25, and 25–35 cm) were measured. Warming effects on concerned soil variables differed with warming time, soil depth, and no-tillage. No-tillage effects on concerned soil variables differed with warming-time (daytime, nighttime, and all-day warming) and soil depths. Therefore, daytime warming and nighttime warming have different effects on soil variables, although the effects of nighttime warming on soil variables are not always greater than those of daytime warming. Effects of daytime warming and nighttime warming on soil variables are not simple addition or subtraction effects. There are interactions between diurnal asymmetrical warming and no-tillage on soil variables. [ABSTRACT FROM AUTHOR]

Ecological similarity plays an important role in biotic interactions. Increased body size similarity of competing species, for example, increases the strength of their biotic interactions. Body sizes of many exothermic species are forecast to be altered under global warming, mediating shifts in existing trophic interactions among species, in particular for species with different thermal niches.Temperate rocky reefs along the southeast coast of Australia are located in a climate warming hotspot and now house a mixture of temperate native fish species and poleward range‐extending tropical fishes (vagrants), creating novel species assemblages. Here, we studied the relationship between body size similarity and trophic overlap between individual temperate native and tropical vagrant fishes.Dietary niche overlap between vagrant and native fish species increased as their body sizes converged, based on both stomach content composition (short‐term diet), stable isotope analyses (integrated long‐term diet) and similarity in consumed prey sizes.We conclude that the warming‐induced faster growth rates of tropical range‐extending fish species at their cool water ranges will continue to converge their body size towards and strengthen their degree of trophic interactions and dietary overlap with co‐occurring native temperate species under increasing ocean warming. The strengthening of these novel competitive interactions is likely to drive changes to temperate food web structures and reshuffle existing species community structures. [ABSTRACT FROM AUTHOR]

In 2020, anthropogenic methane (CH4) emissions decreased due to COVID‐19 containment policies, but there was a substantial increase in the concentration of atmospheric CH4. Previous research suggested that this abnormal increase was linked to higher wetland CH4 emissions and a decrease in the atmospheric CH4 sink. However, the impact of changes in the soil CH4 sink remained unknown. To address this, we utilized a process‐based model to quantify alterations in the soil CH4 sink of terrestrial ecosystems between 2019 and 2020. By implementing the model with various datasets, we consistently observed an increase in the global soil CH4 sink, reaching up to 0.35 ± 0.06 Tg in 2020 compared to 2019. This increase was primarily attributed to warmer soil temperatures in northern high latitudes. Our results emphasize the importance of considering the CH4 sink in terrestrial ecosystems, as neglecting this component can lead to an underestimation of both emission increases and reductions in atmospheric CH4 sink capacity. Furthermore, these findings highlight the potential role of increased soil warmth in terrestrial ecosystems in slowing the growth of CH4 concentrations in the atmosphere. [ABSTRACT FROM AUTHOR]

Microbial necromass carbon (MNC) accounts for a large fraction of soil organic carbon (SOC) in terrestrial ecosystems. Yet our understanding of the fate of this large carbon pool under long‐term warming is uncertain. Here, we show that 14 years of soil warming (+4°C) in a temperate forest resulted in a reduction in MNC by 11% (0–10 cm) and 33% (10–20 cm). Warming caused a decrease in the content of MNC due to a decline in microbial biomass carbon and reduced microbial carbon use efficiency. This reduction was primarily caused by warming‐induced limitations in available soil phosphorus, which, in turn, constrained the production of microbial biomass. Conversely, warming increased the activity of soil extracellular enzymes, specifically N‐acetylglucosaminidase and leucine aminopeptidase, which accelerated the decomposition of MNC. These findings collectively demonstrate that decoupling of MNC formation and decomposition underlie the observed MNC loss under climate warming, which could affect SOC content in temperate forest ecosystems more widespread. [ABSTRACT FROM AUTHOR]

Vegetation changes are expected to alter soil thermal regimes, consequently modifying climate feedbacks related to frozen ground thawing and carbon cycling in cold regions. The Tibetan Plateau (TP) contains diverse alpine ecosystems and the largest area of frozen ground in low–mid latitude regions. Evidence suggests ongoing vegetation greening and permafrost degradation during the past several decades on the TP. However, the effect of vegetation changes on soil thermal regimes on the TP is not well understood. Here, we quantify the response of shallow soil temperature change to vegetation greening on the TP using remote–sensing data, in–situ observations, and physics–based modelling. Our results show that over the past 20 years, vegetation greening on the TP was accompanied a notable decrease in the area of bare land by approximately 0.7% (5000 km2). Annual mean soil temperature showed a significant warming trend of 0.57 °C decade–1 (p < 0.05) during the period 1983–2019, exceeding the warming rate of surface air temperature. Changes in vegetation resulted in a warming effect on annual shallow soil temperature of 0.15 ± 0.33 °C across the TP during the period 2000–2019. The warming effect varies with frozen soil types: 0.24 ± 0.48 °C in permafrost, 0.18 ± 0.36 °C in seasonally frozen ground, and 0.11 ± 0.32 °C in unfrozen ground. The net warming effect was caused by a decrease in albedo and increase in radiation penetrating the canopy, outweighing the cooling effect related to a limited increase in evapotranspiration. [ABSTRACT FROM AUTHOR]

Increased atmospheric nitrogen (N) deposition and climate warming are both anticipated to influence the N dynamics of northern temperate ecosystems substantially over the next century. In field experiments with N addition and warming treatments, cumulative treatment effects can be important for explaining variation in treatment effects on N dynamics over time; however, comparisons between data collected in the early vs. later years potentially can be confounded with interactions between treatment effects and inter-annual variation in environmental conditions or other factors. We compared the short-term versus long-term effects of N addition and warming on net N mineralization and N leaching in a grass-dominated old field using in situ soil cores. We added new N addition and warming plots (3 years old) to an existing field experiment (16 years old), which enabled comparison of the treatment effects at both time scales while controlling for potential inter-annual variation in other factors. For net N mineralization, there was a significant interaction between plot age and N addition over the growing season, and for extractable inorganic N there was a significant interaction between plot age and warming over winter. In both cases, the directions of the treatment effects differed among old and new plots. Moreover, the responses in the new plots differed from the responses observed previously when the 16-year-old plots had been new. These results demonstrate how inter-annual variation in responses, independent from cumulative treatment effects, can play an important role in interpreting long-term effects on soil N cycling in global change field experiments. [ABSTRACT FROM AUTHOR]

Warming‐induced soil drought, especially in topsoil, may enlarge the spatial mismatch between nutrients and water along the soil profile, which impedes the uptake of not only water but also nutrients by trees. Therefore, coordinating the acquisition of soil water and nutrients along the soil profile is an important strategy for trees to cope with global warming.This study examined soil depth‐related changes in nutrient concentrations, biomass and morphology of fine roots in a Chinese fir plantation after 3 years of large‐scale manipulative soil warming.Soil warming (ambient +4°C) increased fine root nitrogen (N) concentrations but decreased fine root phosphorus (P) concentrations across soil depths. Warming did not affect total fine root biomass and its vertical distribution. At the 0–10 cm depth, warming increased specific root length (SRL), specific root area (SRA), fine root diameter (RD) and root length density (RLD) but reduced root tissue density (RTD). In the 40–60 cm layer, warming reduced RD, SRL and RLD while increasing RTD mainly for roots of the 1–2 mm diameter class.Synthesis. We concluded that roots of Chinese fir plantations could adapt to warming‐induced moderate water stress through contrasting depth‐related root morphological adjustments, probably to optimize the acquisition of both soil water and nutrients. The results of this study are crucial for understanding the adaptation strategies of subtropical forests under future climate conditions. [ABSTRACT FROM AUTHOR]

Soil pH significantly impacts microbial activity and community assembly, which in turn determines the temperature sensitivity (Q10) of soil respiration. Due to the high soil acidification in China, it is necessary to understand how soil acidification impacts Q10. Here, the Q10 of soil respiration was examined in a long-term field experiment (1982–present) with different soil pH caused by fertilization management. In this experiment, we selected treatments with neutral pH: (1) no crops and fertilization (CK); (2) crops without fertilization (NF); low pH with (3) crops with chemical fertilization (NPK); and (4) crops with chemical fertilization combined with wheat straw incorporation (WS). Under natural soil temperature changes, we observed that soil acidification lowered the Q10 value of soil respiration. Considering only temperature changes, the Q10 of soil respiration was strongly associated with microbial community composition, alpha diversity, and soil ammonium nitrogen. Considering the interaction between soil pH and temperature, warming strengthened the negative effect of soil pH on the Q10 of soil respiration, and the pathway through which soil pH mediated Q10 included not only microbial community composition, alpha diversity, and biomass but also the soil's available phosphorus. This work enhanced our insights into the relationships between Q10, temperature, and soil pH by identifying important microbial properties and key soil environmental factors. [ABSTRACT FROM AUTHOR]

The scientific literature has many studies evaluating numerical weather prediction (NWP) models. However, many of those studies averaged across a myriad of different atmospheric conditions and surface forcings that can obfuscate the atmospheric conditions when NWP models perform well versus when they perform inadequately. To help isolate these different weather conditions, we used observations from the U.S. Climate Reference Network (USCRN) obtained between 1 January and 31 December 2021 to distinguish among different near-surface atmospheric conditions [i.e., different near-surface heating rates ( d T / d t ), incoming shortwave radiation (SWd) regimes, and 5-cm soil moisture (SM05)] to evaluate the High-Resolution Rapid Refresh (HRRR) Model, which is a 3-km model used for operational weather forecasting in the United States. On days with small (large) d T / d t , we found afternoon T biases of about 2°C (−1°C) and afternoon SWd biases of up to 170 W m−2 (100 W m−2), but negligible impacts on SM05 biases. On days with small (large) SWd, we found daytime temperature biases of about 3°C (−2.5°C) and daytime SWd biases of up to 190 W m−2 (80 W m−2). Whereas different SM05 had little impact on T and SWd biases, dry (wet) conditions had positive (negative) SM05 biases. We argue that the proper evaluation of weather forecasting models requires careful consideration of different near-surface atmospheric conditions and is critical to better identify model deficiencies in order to support improvements to the parameterization schemes used therein. A similar, regime-specific verification approach may also be used to help evaluate other geophysical models. Significance Statement: Improving weather forecasting models requires careful evaluations against high-quality observations. We used observations from the U.S. Climate Reference Network (USCRN) and found that the performance of the High-Resolution Rapid Refresh (HRRR) Model varies as a function of differences in near-surface heating and solar radiation. This finding indicates that model evaluations need to be conducted under varying near-surface weather conditions rather than averaging across multiple weather types. This new approach will allow for model developers to better identify model deficiencies and is a useful step to helping improve weather forecasts. [ABSTRACT FROM AUTHOR]

Manganese (Mn) is a redox‐active micronutrient that has been shown to accelerate plant litter decomposition; however, the effect of Mn‐promoted decomposition on soil C storage is unclear. We present a novel biogeochemical model simulating how Mn bioavailability influences soil organic C (SOC) stocks in a soil profile (<50 cm) within a temperate forest. In our model, foliar Mn increased in response to increasing soluble Mn released through Mn‐oxide (birnessite) dissolution in mineral soil layers. The ensuing Mn enrichment in leaf litter redistributed Mn to the surface forest floor layer, promoted enzymatic oxidation of lignin, and decreased SOC stocks. Total SOC loss was partially mitigated by accumulation of lignin‐oxidation products as mineral‐associated organic C. We also explored how Mn‐driven changes to C storage interacted with effects of N deposition and warming. Nitrogen enrichment inhibited Mn‐dependent lignin degradation, increasing SOC stocks and weakening their dependence on Mn bioavailability. Warming stimulated decomposition and reduced C stocks but was less effective at low Mn bioavailability. Our model results suggest that SOC stocks are sensitive to Mn bioavailability because increased plant uptake redistributes Mn to surface soils where it can enhance litter decomposition. Based on our simulations, we predict that Mn becomes limiting to litter decomposition where Mn is poorly soluble. Depletion of bioavailable Mn or other cofactors that are critical to decomposition could limit the response of organic C stocks to warming over time, but quantitative projections of the role of Mn bioavailability in regulating decomposition requires additional measurements to constrain model uncertainties. Plain Language Summary: Carbon that is removed from the atmosphere by plants and stored in soils has the potential to partially offset greenhouse gas emissions and mitigate climate change. However, predictions of soil carbon storage are challenged by limited understanding of complex interactions between biological and geochemical processes that influence how quickly organic matter decomposes in the soil. We developed a novel model that simulates how cycling of the micronutrient manganese between soils and plants impacts carbon storage in a soil profile. Although it has been demonstrated that manganese is involved in breakdown of lignin, an important component of plant litter, its effects on soil carbon storage are unknown. We also explore how effects of manganese interact with two other major global perturbations: warming and nitrogen deposition to soils. From our model results, we determine that high levels of manganese uptake by plants ultimately generate manganese‐rich surface soils that promote litter decomposition and decrease soil carbon storage. Nitrogen deposition increased carbon storage by inhibiting effects of manganese on decomposition. Decomposition increased with warming but was inhibited by low manganese bioavailability. Our model provides a novel framework for simulating how soil properties that control micronutrient availability to plants can impact soil carbon dynamics. Key Points: We developed a biogeochemical model simulating how manganese bioavailability impacts soil carbon storage in temperate forestsManganese redistribution to surface soils by plants enhanced decomposition and decreased carbon storage in the soil profileOur model predicts that low manganese bioavailability may generate nutrient limitation that decreases warming effects on decomposition [ABSTRACT FROM AUTHOR]

In permafrost regions with warm frozen soil, the pile foundation is commonly used, but most currently available models for the WFS foundation pile–soil system are either highly empirical or overcomplicated, without a simplified theoretical manner in engineering. This study derives a novel and simplified calculated model of the WFS pile–soil system. The model is formulated in terms of the shear deformation theory and load transfer method based on the rigorous deformation mechanism of the WFS foundation soil around the pile. Considering the different depth soil features and the equilibrium state of the pile–soil system, dividing warm frozen soil foundation into three regions (TPPR, ER, and BPPR) to calculate the Dp and Ds can simply obtain the total displacement of pile under different loads. The results demonstrate that the present theoretical model can well predict the WFS foundation load–displacement response of the pile. The present model provides a simple, practical, and effective approach for the estimation of the load–displacement behavior of piles installed in the WFS foundation. [ABSTRACT FROM AUTHOR]

Mercury (Hg) is a pollutant that bioaccumulates in the food web, leading to health issues in humans and other fauna. Although anthropogenic Hg deposition has decreased over the past 20 years, our watersheds continue to be sources of Hg to downstream communities. Wetlands, especially peatlands in the Boreal Region of the globe, play a vital role in the formation of bioaccumulative methylmercury (MeHg). Few studies have assessed how increases in temperatures such as those that have already occurred and those predicted will influence the hydrologic transport of Hg to downstream communities or the net fluxes of gaseous Hg. The results indicate that peatland pore water concentrations of MeHg are increasing with ecosystem warming, and to some degree with elevated carbon dioxide (eCO2) in the Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment at the Marcell Experimental Forest (MEF) in northern Minnesota, USA. Similar to SPRUCE, in the Biological Response to A Changing Environment (BRACE) experiment in Canada, mesocosm pore water MeHg concentrations increased with soil warming. However, long-term peatland watershed streamflow fluxes of MeHg at the MEF indicate that the competing effects of climate warming and decreased atmospheric deposition have led to overall decreases in watershed MeHg transport. Mesocosm studies in the PEATCOSM experiment in Upper Michigan, USA, indicate that simulated fluctuating water tables led to higher concentrations of MeHg in peatland pore water that is available for downstream transport when water tables rise and the next runoff event occurs. Results from a winter peatland soil freeze/thaw simulation from large mesocosm cores from Jennie's Bog at the MEF indicate higher total Hg (THg) upon soil thawing but lower MeHg, likely a result of cold temperatures limiting methylation during thawing. Although there are lower MeHg concentrations after thawing, more THg is available for methylation once soils warm. Results from PEATCOSM and the literature also suggest that plant community changes that result in higher densities of sedges also lead to elevated MeHg in pore water. From a climate warming perspective, it appears that two complementary mechanisms, both related to decomposition, are at play that lead to increased pore water MeHg concentrations with warming. First, warming increases decomposition rates, leading to a higher availability of many ions, including Hg (and sulfur) species. Higher decomposition rates also lead to increases in soluble carbon which complexes with Hg species and assists in downstream hydrologic transport. However, if streamflow is decreasing with climate change as a result of landscape-level changes in evapotranspiration as suggested at MEF, the combination of less direct watershed Hg deposition and lower streamflow results in decreases in the watershed transport of MeHg. Given changes already occurring in extreme events and the rewetting and restoration of hydrology during peatland restoration, it is likely that methylation and pore water MeHg concentrations will increase. However, the landscape-level hydrologic cycle will be key to understanding the connection to downstream aquatic communities. Finally, gaseous Hg fluxes increase with warming and lead to decreases in peatland pools of Hg that may influence future availability for downstream transport. [ABSTRACT FROM AUTHOR]

Kelps are in global decline due to climate change, which includes ocean warming. To identify vulnerable species, we need to identify their tolerances to increasing temperatures and determine whether tolerances are altered by co‐occurring drivers such as inorganic nutrient levels. This is particularly important for those species with restricted distributions, which may already be experiencing thermal stress. To identify thermal tolerance of the range‐restricted kelp Lessonia corrugata, we conducted a laboratory experiment on juvenile sporophytes to measure performance (growth, photosynthesis) across its thermal range (4–22°C). We determined the upper thermal limit for growth and photosynthesis to be ~22–23°C, with a thermal optimum of ~16°C. To determine if elevated inorganic nitrogen availability could enhance thermal tolerance, we compared the performance of juveniles under low (4.5 μmol · d−1) and high (90 μmol · d−1) nitrate conditions at and above the thermal optimum (16–23.5°C). Nitrate enrichment did not enhance thermal performance at temperatures above the optimum but did lead to elevated growth rates at the thermal optimum. Our results indicate L. corrugata is likely to be extremely susceptible to moderate ocean warming and marine heatwaves. Peak sea surface temperatures during summer in eastern and northeastern Tasmania can reach up to 20–21°C, and climate projections suggest that L. corrugata's thermal limit will be regularly exceeded by 2050 as southeastern Australia is a global ocean‐warming hotspot. By identifying the upper thermal limit of L. corrugata, we have taken a critical step in predicting the future of the species in a warming climate. [ABSTRACT FROM AUTHOR]

The impact of anthropogenic global warming has induced significant upward dispersal of trees to higher elevations at alpine treelines. Assessing vertical deviation from current uppermost tree distributions to potential treeline positions is crucial for understanding ecosystem responses to evolving global climate. However, due to data resolution constraints and research scale limitation, comprehending the global pattern of alpine treeline elevations and driving factors remains challenging. This study constructed a comprehensive quasi‐observational dataset of uppermost tree distribution across global mountains using Google Earth imagery. Validating the isotherm of mean growing‐season air temperature at 6.6 ± 0.3°C as the global indicator of thermal treeline, we found that around two‐thirds of uppermost tree distribution records significantly deviated from it. Drought conditions constitute the primary driver in 51% of cases, followed by mountain elevation effect which indicates surface heat (27%). Our analyses underscore the multifaceted determinants of global patterns of alpine treeline, explaining divergent treeline responses to climate warming. Moisture, along with temperature and disturbance, plays the most fundamental roles in understanding global variation of alpine treeline elevation and forecasting alpine treeline response to ongoing global warming. [ABSTRACT FROM AUTHOR]

Increasing global temperatures due to high atmospheric carbon dioxide (CO2) concentrations may cause an imbalance in the carbon circulation on earth. It has been reported that CO2 emissions from natural soils in all terrestrial areas on Earth account for about 25% of atmospheric CO2 emissions in the global carbon cycle. A tendency is well known that the higher the soil temperature with the higher the metabolic activity of microorganisms in the soil. Furthermore, since the global soil CO2 emissions are huge amount that approximately seven times the total atmospheric CO2 emissions from human origin, it is necessary to investigate the increasing rate of soil CO2 emission rate per unit area and unit time on a global scale (global soil CO2 efflux) that is affected by soil temperature rise due to global warming expected in the coming decades. In this paper, we modeled soil CO2 efflux vs. diurnal and seasonal variation in soil temperature at a measurement point using a formula that is an exponential function of soil temperature and then evaluated the effect of increasing average soil temperature due to surface air temperature rise by global warming. We have proposed a method to analogically evaluate the potential of increasing the rate of soil CO2 efflux against a change of 1°C in soil temperature based on the model equation. The power index b (°C-1) just indicates the potential of increasing the rate of soil CO2 efflux to soil temperature rise in any land area with different soil temperatures on earth. Finally, the values of b were obtained from the published literature with field measurement data at 71 locations in 10 countries including our data measured at the Ito campus, Kyushu University. The average rate of potential increase in soil CO2 efflux is 0.10°C-1 regardless of vegetation, annual rainfall (precipitation), soil type, and soil components (carbon and nitrogen content). In conclusion, assuming the average soil temperature rises by 1°C and ignoring any effects reducing soil CO2 reduction due to global warming, the potential increase in annual global soil CO2 efflux is roughly estimated at 22 billion tons-CO2/year. [ABSTRACT FROM AUTHOR]

Flooding and climate warming lead to the increase of low‐molecular‐weight organic acid (LMWOA) inputs to soil. However, it is unclear what the effects of flooding and climate warming on soil nitrogen fraction transformation under LMWOA input are. Fluvisol was collected in the riparian zone of the Three Gorges Reservoir to conduct an incubation experiment with the treatments of three LMWOAs at five contents, two hydrological environments and two temperatures. Compared with LMWOA input of 0 mg kg−1, the soil nitrogen in ion exchangeable fraction (IEF‐N), strong oxidant extractable fraction (SOEF‐N) and non‐transformable nitrogen (NTF‐N) were increased by 35.77, 54.71 and 25.49 mg kg−1, respectively, under LMWOA input of 40 mmol kg−1. Soil nitrogen in the weak acid extractable fraction (WAEF‐N) was decreased by 117.41 mg kg−1. Microbial biomass nitrogen (MBN) was increased by 25.29 mg kg−1, and calcium carbonate (CaCO3) was decreased by 8.03 g kg−1. The contents of IEF‐N, NTF‐N and amorphous iron oxides were higher under the flooding environment than under the drying environment. In contrast, opposite results were observed for soil nitrogen in the strong alkali extractable fraction (SAEF‐N), SOEF‐N and MBN. IEF‐N and NTF‐N contents were higher at 20°C than at 30°C, and the contents of SOEF‐N and MBN were higher at 30°C than at 20°C. WAEF‐N was dissolved by LMWOA through CaCO3 dissolution. The dissolved WAEF‐N was partly transformed into SOEF‐N and NTF‐N by microbial assimilation and humification. Flooding desorbed SAEF‐N through the crystalline transformation of iron oxides. Flooding inhibited the transformation of IEF‐N to SOEF‐N and promoted the formation of NTF‐N, while warming did the opposite. The results provide a perspective of the bound state between soil and nitrogen for understanding the soil nitrogen cycling and help to assess the impacts of climate warming and flooding on soil nitrogen loss from soil to the surrounding water. [ABSTRACT FROM AUTHOR]

This document is a reply to a study published in Nature Communications that reported a decrease in global soil microbial biomass carbon (MBC) due to increasing temperatures. However, the authors of this reply conducted field experiments and found no consistent reductions in MBC in response to soil warming. They suggest that the decline predicted by the original study may be a result of spatial gradients rather than actual temporal changes. Further research is needed to understand the potential effects of climate change on MBC. The study was funded by the Chinese Academy of Sciences, the Second Tibetan Plateau Scientific Expedition and Research Program, and the National Natural Science Foundation of China. [Extracted from the article]

Unravelling biosphere feedback mechanisms is crucial for predicting the impacts of global warming. Soil priming, an effect of fresh plant-derived carbon (C) on native soil organic carbon (SOC) decomposition, is a key feedback mechanism that could release large amounts of soil C into the atmosphere. However, the impacts of climate warming on soil priming remain elusive. Here, we show that experimental warming accelerates soil priming by 12.7% in a temperate grassland. Warming alters bacterial communities, with 38% of unique active phylotypes detected under warming. The functional genes essential for soil C decomposition are also stimulated, which could be linked to priming effects. We incorporate lab-derived information into an ecosystem model showing that model parameter uncertainty can be reduced by 32–37%. Model simulations from 2010 to 2016 indicate an increase in soil C decomposition under warming, with a 9.1% rise in priming-induced CO2 emissions. If our findings can be generalized to other ecosystems over an extended period of time, soil priming could play an important role in terrestrial C cycle feedbacks and climate change. Soil priming could release large amounts of soil C into the atmosphere. Here the authors show that experimental warming boosts soil priming and CO2 emissions in grasslands potentially due to microbial changes. Model accuracy could be improved by incorporating these mechanisms. [ABSTRACT FROM AUTHOR]

Field and laboratory studies on the effect of different systems of tillage on soil agrophysical properties, seed germination and productivity of maize (corn) demonstrate that tillage influences soil water content, penetration resistance and bulk density throughout the growing season. Faster soil warming and seed germination under the mouldboard plough influenced all stages of maize growth and development; minimal tillage was associated with lesser plant height, leaf area, number of cobs per 100 plants and 1000-grain weight, leading to an average yield shortfall of 0.37–0.88t/ha compared to the mouldboard plough. [ABSTRACT FROM AUTHOR]

The iron content can be used as a proxy for the intensity of weathering and pedogenesis, which reflect long‐term climate cycles and short‐term climate fluctuations and events. In this study, a typical loess–palaeosol sequence for 19.85 m in thickness deposited since 423 ka BP in northeastern China was investigated, and its iron pools were determined. The results reveal that with increasing depth, the abundances of different forms of iron are consistent with the changes in the magnetic susceptibility. Iron (Fe) in all forms is more abundant in the palaeosol than in the loess. The silicate‐bound Fe pool (Fer = Fet − Fed) accounts for 60.4% of the total Fe (Fet), indicating weak pedogenesis. The Fe in the crystalline oxides (Fec = Fed − Feo) is predominantly free Fe (Fed), with a crystallinity [Fey = (Fed − Feo) × 100 / Fed] of as high as 97.2%. The coefficients of variation of the different forms of iron associated with the soil depth are as follows: Fec > Fed > poorly crystalline Fe (Feo) > Fer > Fet. The distribution of the forms of Fe throughout the profile is a clear indicator of the pedogenesis. The Fed, Fec, and Fe freeness (freeness = Fed × 100 / Fet) correlate with the magnetic susceptibility. The neoformation of iron (Fe) oxides was closely related to the degree of pedogenesis. More crystalline Fe oxides were found in the soil layers corresponding to warm interglacial periods. We detected variations in the abundance of the Fe pools for characterizing climate fluctuations that occurred in a short period of time. In this study, we demonstrated that when used in combination with dating techniques, morphological development indices, and magnetic susceptibility, the measurement of soil Fe pools can be extremely useful for tracing the iron evolution in the Earth's critical zone and reconstructing past climatic events in loess–palaeosol sequences. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) is the largest terrestrial carbon pool, but it is still uncertain how it will respond to climate change. Especially the fate of SOC due to concurrent changes in soil temperature and moisture is uncertain. It is generally accepted that microbially driven SOC decomposition will increase with warming, provided that sufficient soil moisture, and hence enough C substrate, is available for microbial decomposition. We use a mechanistic, microbially explicit SOC decomposition model, the Jena Soil Model (JSM), and focus on the depolymerisation of litter and microbial residues by microbes at different soil depths, and its sensitivities to soil warming and different drought intensities. In a series of model experiments we test the effects of soil warming and droughts on SOC stocks, in combination with different temperature sensitivities (Q 10 values) for the half-saturation constant Km (Q 10, Km ) associated with the breakdown of litter or microbial residues. Microbial depolymerisation rates of litter and residues are proportional to microbial biomass (reverse kinetics), so that at low microbial biomass, the temperature sensitivity of Km plays a more prominent role. We find that soil warming leads to long-term SOC losses, but depending on SOC composition and its associated Q 10, Km values, these losses can be either reduced or further accelerated, especially in the subsoil where microbial biomass is low. Droughts can alleviate the effects of soil warming and reduce SOC losses, and even lead to SOC gains, provided unchanged litter inputs. Furthermore, a combination of drought and different Q 10, Km values associated with the breakdown of litter or microbial residues can have counteracting effects on the overall decomposition rates. In this study, we show that while absolute SOC changes driven by soil warming and drought are highest in the topsoil, SOC in the subsoil is more sensitive to the (sometimes counteracting) interplay between Km , temperature and soil moisture changes, and mineral-associated SOC. [ABSTRACT FROM AUTHOR]

Climate projections predict higher temperatures and more frequent hurricanes in the tropics. Tropical plants subjected to these stresses may respond by acclimating their physiology. We investigated tropical forest root respiration in response to in situ experimental warming and hurricane disturbance in eastern Puerto Rico. We measured mass-normalized root specific respiration, root biomass, and root traits at the Tropical Responses to Altered Climate Experiment (TRACE), where understory vegetation is warmed + 4 °C above ambient. Our measurements span 5 years, including before and after two major hurricanes, to quantify root contributions to ecosystem carbon fluxes. Experimental warming did not affect root specific respiration at a standard temperature of 25° (RSR25, mean = 3.89 nmol CO2 g−1 s−1) or the temperature sensitivity of root respiration (Q10, mean = 1.75), but did result in decreased fine-root biomass, thereby decreasing area-based estimations of ecosystem-level root respiration in warmed plots by ~ 35%. RSR25 of newer roots, which increased with increasing root nitrogen, showed greater rates 6 months after the hurricanes, but subsequently decreased after 12 months. Root specific respiration did not acclimate to higher temperatures, based on lack of adjustments in either Q10 or RSR25 in the warmed plots; however, decreased root biomass indicates the root contribution to soil carbon dioxide efflux was overall lower with warming. Lower root biomass may also limit nutrient and water uptake, having potential negative effects on carbon assimilation. Our results show that warming and hurricane disturbance have strong potential to affect tropical forest roots, as well as ecosystem carbon fluxes. [ABSTRACT FROM AUTHOR]

Projections of West African Monsoon (WAM) precipitation are uncertain. To address this, an improved understanding of the mechanisms driving WAM precipitation change is needed to shed light on inter-model differences and aid model development. The full forcing of increased CO2 can be decomposed into different components such as the impact of ocean warming, or the direct radiative effect of increased CO2. This paper investigates such a decomposition, analysing the effect of a uniform 4K ocean warming whilst keeping atmospheric CO2 concentrations constant. The analysis highlights several mechanisms acting to decrease WAM precipitation over a range of timescales, from days after the abrupt ocean warming, to the long-term equilibrium response. The initial decrease in WAM precipitation is caused by warming and enhanced convection over the ocean, stabilising the atmosphere inland and disrupting the monsoon inflow at low levels. Later in the response (after about 5 days), the WAM precipitation is reduced through a strengthening of the shallow circulation over West Africa, associated with changes in the large-scale temperature gradients and a local warming of the atmosphere related to a soil moisture feedback mechanism over the Sahel. Finally, from around 20 days after the SST increase, the WAM precipitation is also reduced through changes in specific humidity gradients that lead to increased potency of dry air advection into the monsoon rainband. The analysis concludes by demonstrating that the processes affecting precipitation in the early stages of the response are also relevant to the long-term equilibrium response. [ABSTRACT FROM AUTHOR]

Climate change is predicted to cause milder winters and thus exacerbate soil freeze–thaw perturbations in the subarctic, recasting the environmental challenges that soil microorganisms need to endure. Historical exposure to environmental stressors can facilitate the microbial resilience to new cycles of that same stress. However, whether and how such microbial memory or stress legacy can modulate microbial responses to cycles of frost remains untested. Here, we conducted an in situ field experiment in a subarctic birch forest, where winter warming resulted in a substantial increase in the number and intensity of freeze–thaw events. After one season of winter warming, which raised mean surface and soil (−8 cm) temperatures by 2.9 and 1.4°C, respectively, we investigated whether the in situ warming‐induced increase in frost cycles improved soil microbial resilience to an experimental freeze–thaw perturbation. We found that the resilience of microbial growth was enhanced in the winter warmed soil, which was associated with community differences across treatments. We also found that winter warming enhanced the resilience of bacteria more than fungi. In contrast, the respiration response to freeze–thaw was not affected by a legacy of winter warming. This translated into an enhanced microbial carbon‐use efficiency in the winter warming treatments, which could promote the stabilization of soil carbon during such perturbations. Together, these findings highlight the importance of climate history in shaping current and future dynamics of soil microbial functioning to perturbations associated with climate change, with important implications for understanding the potential consequences on microbial‐mediated biogeochemical cycles. [ABSTRACT FROM AUTHOR]

Relative to drought and heat waves, the effect of winter warming on forest CO2 fluxes during the dormant season has less been investigated, despite its relevance for net CO2 uptake in colder regions with higher carbon content in soils. Our objective was to test the effect of the exceptionally warm winter in 2020 on the winter CO2 budget of cold-adapted evergreen needle-leaf forests across Europe, and identify the contribution of soil and air temperature to changes in winter CO2 fluxes in response to warming. Our hypothesis was that warming in winter leads to higher emissions across colder sites due to increased ecosystem respiration. To test this hypothesis, we used 98 site-year eddy covariance measurements across 14 evergreen needle-leaf forests (ENFs) distributed from north to south of Europe (from Sweden to Italy). We used a data-driven approach to quantify the effect of air and soil temperature on changes in net ecosystem productivity (NEP) during the warm winter of 2020. Our results showed that the impact of warming was different across sites, as in the lower altitude and lower latitude sites positive soil temperature anomalies were larger, while positive air temperature anomalies were larger in the northern latitude and high-altitude sites. Warming in winter led to a divergent response across the sites. Out of 14 sites only in 3 sites net ecosystem productivity declined in winter significantly in response to warming. In addition, we observed that in the colder sites daytime NEP (that is dominated by photosynthesis) declined with warming of the air in winter, whereas in the warmer sites daytime NEP increased with warming of the soil. This shows that warming of the air – if not translated into a direct warming of the soil– might not trigger productivity in winter if the soil within the rooting zone remains frozen. Forests within the same plant functional type category can exhibit differing reactions to winter warming and to predict their responses accurately it is crucial to account for variations in local climate, physiology, and structure simultaneously. [ABSTRACT FROM AUTHOR]

Relative to drought and heat waves, the effect of winter warming on forest CO2 fluxes during the dormant season has less been investigated, despite its relevance for net CO2 uptake in colder regions with higher carbon content in soils. Our objective was to test the effect of the exceptionally warm winter in 2020 on the winter CO2 budget of cold-adapted evergreen needleleaf forests across Europe, and identify the contribution of soil and air temperature to changes in winter CO2 fluxes in response to warming. Our hypothesis was that warming in winter leads to higher emissions across colder sites due to increased ecosystem respiration. To test this hypothesis, we used 98 site-year eddy covariance measurements across 14 evergreen needleleaf forests (ENFs) distributed from north to south of Europe (from Sweden to Italy). We used a data-driven approach to quantify the effect of air and soil temperature on changes in net ecosystem productivity (NEP) during the warm winter of 2020. Our results showed that the impact of warming was different across sites, as in the lower altitude and lower latitude sites positive soil temperature anomalies were larger, while positive air temperature anomalies were larger in the northern latitude and high-altitude sites. Warming in winter led to a divergent response across the sites. Out of 14 sites only in 3 sites net ecosystem productivity declined in winter significantly in response to warming. In addition, we observed that in the colder sites daytime NEP (that is dominated by photosynthesis) declined with warming of the air in winter, whereas in the warmer sites daytime NEP increased with warming of the soil. While warming increases ecosystem respiration, it might not trigger productivity in winter if the soil within the rooting zone remains frozen. Forests within the same plant functional type category can exhibit differing reactions to winter warming and to predict their responses accurately it is crucial to account for variations in local climate, physiology, and structure simultaneously. [ABSTRACT FROM AUTHOR]

Purpose: Mangrove ecosystems which play a critical role in global C sequestration have recently become threatened by global warming and sea level rise. This study aimed to explore the responses of SOC mineralization and C pool stability in mangrove ecosystems to warming and flooding conditions. Methods: Laboratory incubation and solid-state 13C nuclear magnetic resonance (13C-NMR) analysis were used to evaluated soil organic carbon (SOC) mineralization and stability under warming (ST), flooding (SW), warming in coincidence with flooding (SWT), and soil under normal temperature taken from a subtropical mangrove ecosystem in southeastern China. Results: The cumulative SOC mineralization of ST increased by 24%, while SWT and SW decreased by 59% and 68% relative to CK, respectively. Furthermore, the 13C-NMR analysis showed that O-alkyl C was the dominant SOC chemical composition in all treatments (37.1–43.1%), followed by the aromatic C and alkyl C. The aromaticity index (AI) decreased, and the ratio of alkyl and O-alkyl to aromatic (Alip/Arom) increased in all treatments compared with CK, while the alkyl C/O-alkyl C ratio (A/O-A) and hydrophobicity index (HI) were higher for ST and SW but lower for SWT. Warming significantly facilitated SOC mineralization, and lowered SOC stability due to the high cumulative CO2-C production, while flooding had the opposite effects. However, warming in coincidence with flooding led to low SOC decomposition and a more recalcitrant substance. Conclusion: The theoretical elevated CO2 release from mangrove soils under warming in coastal zones might be partially offset by prolonged flooding. The different effects on the chemical fractions, chemical compositions, and stability of the SOC pool in mangrove soil under warming and flooding might further complicate the research on coastal carbon sinks. [ABSTRACT FROM AUTHOR]

Introduction: Global warming is caused by greenhouse gases (GHGs). It has been found that the release of methane (CH4) from Arctic permafrost, soil, ocean, and sediment is closely related to microbial composition and soil factors resulting from warming over several months or years. However, it is unclear for how long continuous warming due to global warming aects the microbial composition and GHG release from soils along Arctic glacial meltwater rivers. Methods: In this study, the soil upstream of the glacial meltwater river (GR) and the estuary (GR-0) in Svalbard, with strong soil heterogeneity, was subjected to short-term field incubation at 2◦C (in situ temperature), 10◦C, and 20◦C. The incubation was carried out under anoxic conditions and lasted for few days. Bacterial composition and CH4 production potential were determined based on high-throughput sequencing and physiochemical property measurements. Results: Our results showed no significant dierences in bacterial 16S rRNA gene copy number, bacterial composition, and methanogenic potential, as measured by mcrA gene copy number and CH4 concentration, during a 7- and 13-day warming field incubation with increasing temperatures, respectively. The CH4 concentration at the GR site was higher than that at the GR-0 site, while the mcrA gene was lower at the GR site than that at the GR-0 site. Discussion: Based on the warming field incubation, our results indicate that short-term warming, which is measured in days, aects soil microbial composition and CH4 concentration less than the spatial scale, highlighting the importance of warming time in influencing CH4 release from soil. In summary, our research implied that microbial composition and CH4 emissions in soil warming do not increase in the first several days, but site specificity is more important. However, emissions will gradually increase first and then decrease as warming time increases over the long term. These results are important for understanding and exploring the GHG emission fluxes of high-latitude ecosystems under global warming. [ABSTRACT FROM AUTHOR]

To help meet the need for the reuse of thermally desorbed soil from contaminated sites, this paper presents a laboratory simulation of the thermal desorption treatment of diesel-contaminated soils. The simulated treatment was based on the thermal desorption treatment of contaminated soil around chemical plants. X-ray micro-computed tomography and mercury pressure porosimetry were used to characterize changes in the pore structure of soil contaminated with diesel fuel and treated with thermal desorption. The changes in pore structure were rationalized in terms of macroscopic shrinkage of soil, matrix suction, particle gradation, and clay minerals. Additionally, permeability properties were explored. The main results were as follows: Thermal desorption altered the pore structure of the soil. With separate heating of different soil samples, the increase in heating temperature enlarged internal pore space, porosity, and average pore diameter, enhanced pore connectivity, and reduced tortuosity of the soil. Continuous heating of identical soil samples at intervals and progressively higher temperatures led to reductions in pore space, porosity, and pore average diameter as well as pore connectivity, and increased tortuosity. Matrix suction and clay minerals were the main factors responsible for changes in the pore structure. The mechanism of matrix suction was the main reason for very different trends in changes in the pore structure. Clay minerals were not influential until temperatures exceeded 400 °C. The permeability coefficients showed two very different trends with temperature under the two heating regimes. [ABSTRACT FROM AUTHOR]

Warming and precipitation fluctuations are changing desert ecosystems in global drylands. However, the effects of climate change on keystone species such as cryptogamic biocrust in drylands remain relatively under‐investigated, even though biocrusts play a vital role in desert ecosystems.We conducted a long‐term experiment (14 years) to simulate the responses of two main types of biocrusts to warming coupled with reduction in precipitation that was achieved by open‐top chambers (OTCs) to simulate the predicted warming and precipitation decreasing under climate change scenario. We also conduct a structural analysis to evaluate the resulting changes in desert ecosystem functioning (carbon and nitrogen cycling).Neither warming and corresponding rainfall reduction treatments had a negative effect on lichen species richness, but both treatments reduced lichen cover and biomass. The negative effects of warming on moss‐dominated crusts were much greater than those on lichen‐dominated crusts. Although mosses and lichens had varying degree responses to warming, the loss of mosses and decreased lichen cover and biomass, as well as the shortening of the wet time, resulted in a reduction in carbon and nitrogen fixation, soil enzyme activity and water‐holding capacity of biocrusts and topsoil. These impacts collectively change the water balance of drylands and weaken the hydrological and biogeochemical function of biocrusts.Synthesis and applications: Results from this long‐term experiment suggest that the ecosystem C and N cycling and water balance of global drylands may be highly impacted by climate change, in part because of the response of biocrusts, which contribute an important implication for both dryland restoration and earth system dynamics. [ABSTRACT FROM AUTHOR]

The impacts of climate change-induced warming on our ecosystems can no longer be neglected, but our understanding of consequences for groundwater ecosystems in general and groundwater quality in particular is alarmingly incomplete. In this review, we therefore provide an overview of the current state of knowledge related to the impact of global warming on our precious groundwater resources. Groundwater warming in shallow aquifers is closely associated with increasing average land surface temperatures and has already reached + 1 K compared to pe-industrial times. Until the end of the twenty-first century, temperature increases in local groundwater of up to + 10 K are possible. Monitoring data, laboratory and field experiments all provide evidence that such temperature increases are sufficient to substantially modify groundwater quality through numerous and interlinked biogeochemical processes, which we have summarized in a conceptual overview. Warming impacts on groundwater are highly site-specific and spatially heterogeneous, which complicates their assessment and prediction. Locally, shallow unconfined and nutrient-rich floodplain aquifers are most susceptible to warming-induced changes. Importantly, processes affecting water quality are not only modified by a long-term rise in groundwater temperatures, but also in the short-term during weather extremes, which is of great relevance for riverbank filtration. At the regional scale, aquifers in cold regions impacted by permafrost thawing are especially vulnerable to warming. As the majority of temperature-sensitive processes affecting groundwater quality are not or only very slowly reversable, we pressingly require comprehensive mechanistic understanding before it is too late to develop suitable countermeasures and management strategies. [ABSTRACT FROM AUTHOR]

The permafrost region has accumulated organic carbon in cold and waterlogged soils over thousands of years and now contains three times as much carbon as the atmosphere. Global warming is degrading permafrost with the potential to accelerate climate change as increased microbial decomposition releases soil carbon as greenhouse gases. A 19-year time series of soil and ecosystem respiration radiocarbon from Alaska provides long-term insight into changing permafrost soil carbon dynamics in a warmer world. Nine per cent of ecosystem respiration and 23% of soil respiration observations had radiocarbon values more than 50‰ lower than the atmospheric value. Furthermore, the overall trend of ecosystem and soil respiration radiocarbon values through time decreased more than atmospheric radiocarbon values did, indicating that old carbon degradation was enhanced. Boosted regression tree analyses showed that temperature and moisture environmental variables had the largest relative influence on lower radiocarbon values. This suggested that old carbon degradation was controlled by warming/permafrost thaw and soil drying together, as waterlogged soil conditions could protect soil carbon from microbial decomposition even when thawed. Overall, changing conditions increasingly favoured the release of old carbon, which is a definitive fingerprint of an accelerating feedback to climate change as a consequence of warming and permafrost destabilization. This article is part of the Theo Murphy meeting issue 'Radiocarbon in the Anthropocene'. [ABSTRACT FROM AUTHOR]

The Central American Dry Corridor experienced five consecutive years of drought from 2015 to 2019. Here, we find that the severity of this drought was driven primarily by rainfall deficits in July–August. To determine if the magnitude of this event was outside the range of natural variability, we apply a statistical resampling method to observations that emulates internal climate variability. Our analyses show that droughts similar to the 2015–2019 event are possible, although extremely rare, even without anthropogenic influences. Persistent droughts in our ensemble are consistently linked to stronger easterly winds associated with the Caribbean Low‐Level Jet. We also examine the effects of temperature on soil moisture during this drought using the Palmer Drought Severity Index and show that anthropogenic warming increases the likelihood of severe deficits. Multi‐year droughts are likely to worsen by the end of the 21st century due to the compound effects of anthropogenic climate change. Plain Language Summary: Climate models project that Central America is one of the global hotspots for future decreases in precipitation as a result of human‐caused climate change. This is particularly concerning for the Dry Corridor region, which is already prone to frequent droughts and high levels of food insecurity among households. Much of this region experienced severe rainfall deficits between 2015 and 2019, provoking the question of whether or not this drought was caused by climate change or if it could have occurred because of natural climate variability alone. Using a statistical model, we show that while 2015–2019 was the driest period in the observational record, droughts as bad as this one are possible even without the influence of human‐caused climate change. We examine the additional role of temperature since it can modulate drought severity through its influence on soil moisture. We find warming temperatures increase the occurrences of greater soil moisture deficits. We also determine that the strength of the Caribbean Low‐Level Jet, which transports moisture from the Caribbean Sea into Central America, is strongly associated with persistent dry conditions in the region. Key Points: The 2015–2019 drought was severe, but it falls within the range of natural climate variabilityJuly–August deficits were the most significant drivers of overall droughtPositive easterly zonal wind anomalies associated with the Caribbean Low‐Level Jet are strongly linked to regional precipitation deficits [ABSTRACT FROM AUTHOR]

Improving resource utilization efficiency is critical for achieving high yields and long-term agricultural development in arid and semi-arid settings. Using potato as the research material, a field trial was carried out from 2020 to 2022 in dryland agricultural areas of China, with two treatments of ridge planting with a furrow mulching straw pattern (SML) and flat planting without mulching (CK). The responses of the dryland potato yield, water use efficiency (WUE), and soil hydrothermal properties to the two cultivation patterns were investigated. The results indicated that during the potato reproductive period, the soil temperature of 0–25 cm in the SML treatment dropped by 0.70–0.83 °C, in comparison to CK; the ridge and furrow-covered belt, which showed a warming effect at 7:00 a.m. in the seedling stage (SD) and the budding stage (BP), was lower than CK in all the rest of the time, and also the planting belt on the ridge, which cooled down significantly at 14:00 a.m. and the performance varied between the years of 7:00 a.m. and 17:00 a.m. SML significantly decreased the water consumption before BP but significantly increased it after BP in the year of median water and mild drought, while the total amount of water consumed during the entire growing season did not differ significantly from CK's. In the year of moderate drought, SML's total water consumption was significantly less than that of CK, with the water consumption significantly lower before BP and after the tuber bulking stage (TB), but significantly higher from the BP to the TB. In three consecutive growing seasons, SML increased the yields by 9.72–41.67% and WUE by 4.62–11.14% compared with CK, with the yields significantly or positively connected with the average soil temperatures at the TB, the starch accumulation stage (SA), and the water consumption from the BP to the TB. Overall, partial straw mulching could be used as a cultivation technique to achieve sustainable agricultural development in dry farming areas. [ABSTRACT FROM AUTHOR]

Indochina is one of the regions with the most severe biomass burning (BB) in the world, which produces enormous amounts of atmospheric aerosols, mostly in spring. Moreover, the spring soil moisture anomalies in Indochina have been found to have a significant influence on the summer rainfall in the Yangtze River Valley (YRV). It is still partially unclear how spring BB in Indochina influences the local and regional climate and land–atmosphere interactions. Here, we use regional model experiments and observational data to show that the radiative effect of BB aerosols in Indochina stabilizes the atmosphere and reduces local precipitation and soil moisture. The dry soil in Indochina persists from spring to summer, which warms the land surface and the atmosphere. As a result, the western Pacific subtropical high (WPSH) is stronger and extends westward from spring to summer. This leads to stronger moisture transport to and more precipitation in the YRV (increases of approximately 5% in July and 10% in August). Thus, the effect of BB aerosols on the YRV rainfall is similar to that of the Indochina dry soil anomaly. Additionally, the increase in the YRV summer rainfall caused by the Indochina spring dry soil anomaly is almost doubled when there are BB aerosols compared to that without BB aerosols, suggesting the importance of BB aerosols in regulating the regional land–atmosphere interactions. [ABSTRACT FROM AUTHOR]

Climatic change conditions (elevated CO2 and warming) have been known to threaten agricultural sustainability and grain yield. Soil fungi play an important role in maintaining agroecosystem functions. However, little is known about the responses of fungal community in paddy field to elevated CO2 and warming. Herein, using internal transcribed spacer (ITS) gene amplicon sequencing and co-occurrence network methods, the responses of soil fungal community to factorial combinations of elevated CO2 (550 ppm), and canopy warming (+2 °C) were explored in an open-air field experiment for 10 years. Elevated CO2 significantly increased the operational taxonomic unit (OTU) richness and Shannon diversity of fungal communities in both rice rhizosphere and bulk soils, whereas the relative abundances of Ascomycota and Basidiomycota were significantly decreased and increased under elevated CO2, respectively. Co-occurrence network analysis showed that elevated CO2, warming, and their combination increased the network complexity and negative correlation of the fungal community in rhizosphere and bulk soils, suggesting that these factors enhanced the competition of microbial species. Warming resulted in a more complex network structure by altering topological roles and increasing the numbers of key fungal nodes. Principal coordinate analysis indicated that rice growth stages rather than elevated CO2 and warming altered soil fungal communities. Specifically, the changes in diversity and network complexity were greater at the heading and ripening stages than at the tillering stage. Furthermore, elevated CO2 and warming significantly increased the relative abundances of pathotrophic fungi and reduced those of symbiotrophic fungi in both rhizosphere and bulk soils. Overall, the results indicate that long-term CO2 exposure and warming enhance the complexity and stability of soil fungal community, potentially threatening crop health and soil functions through adverse effects on fungal community functions. [ABSTRACT FROM AUTHOR]

Side insertion horizontal transplanting sweet potato seedlings on mulch film is one kind of new planter pattern, which keeps the soil warm and moist restraining the infestation of pests and weeds, realizing dense transplanting and ensuring uniformity of sweet potato sizes. Therefore, a side insertion horizontal transplanting device for sweet potato seedlings on mulch film was designed, including the details and parameters of the reciprocating mechanism and the seedling clamping mechanism. Both the two mechanisms and the whole device were simulated and the test bench was built for field experiments to detect if this device can meet the agronomic requirements. The simulation results show that the designed device is in accordance with the agronomic requirements of horizontal transplanting, transplanting depth and transplanting length, and is potential for achieving rational close planting. The lateral length of the designed transplanting device is extended at about 90 mm compared with previous machine, which will promote the number of soil nodules of sweet potato seedlings and the growth of production enormously. The horizontal velocity of the transplanting claw is â?'17 mm/s when picking the seedling, the horizontal velocity of the transplanting claw 645 mm/s and the vertical velocity 83 mm/s when releasing the seedling. These data could ensure the accuracy requirements of horizontal transplanting trajectory. The field experiment results show the expulsion rate of sweet potato seedlings at 1.38%, the qualified rate of transplanting length and depth at 94.17% and 95.11% respectively, the average length and width of the mulch film breaking hole at 44.67 mm and 43.00 mm in several. The postures of the actual transplanted seedlings are consistent with the simulation results, meeting the requirements of horizontal transplanting with less damage to the mulch film. The designed transplanting device lays a foundation for the development of sweet potato seedlings side transplanting machine. [ABSTRACT FROM AUTHOR]

Adaptation of soil microbes due to warming from climate change has been observed, but it remains unknown what microbial growth traits are adaptive to warming. We studied bacterial isolates from the Harvard Forest Long-Term Ecological Research site, where field soils have been experimentally heated to 5°C above ambient temperature with unheated controls for 30 years. We hypothesized that Alphaproteobacteria from warmed plots have (i) less temperature-sensitive growth rates; (ii) higher optimum growth temperatures; and (iii) higher maximum growth temperatures compared to isolates from control plots. We made high-throughput measurements of bacterial growth in liquid cultures over time and across temperatures from 22°C to 37°C in 2-3°C increments. We estimated growth rates by fitting Gompertz models to the growth data. Temperature sensitivity of growth rate, optimum growth temperature, and maximum growth temperature were estimated by the Ratkowsky 1983 model and a modified Macromolecular Rate Theory (MMRT) model. To determine evidence of adaptation, we ran phylogenetic generalized least squares tests on isolates from warmed and control soils. Our results showed evidence of adaptation of higher optimum growth temperature of bacterial isolates from heated soils. However, we observed no evidence of adaptation of temperature sensitivity of growth and maximum growth temperature. Our project begins to capture the shape of the temperature response curves, but illustrates that the relationship between growth and temperature is complex and cannot be limited to a single point in the biokinetic range. IMPORTANCE Soils are the largest terrestrial carbon sink and the foundation of our food, fiber, and fuel systems. Healthy soils are carbon sinks, storing more carbon than they release. This reduces the amount of carbon dioxide released into the atmosphere and buffers against climate change. Soil microbes drive biogeochemical cycling and contribute to soil health through organic matter breakdown, plant growth promotion, and nutrient distribution. In this study, we determined how soil microbial growth traits respond to long-term soil warming. We found that bacterial isolates from warmed plots showed evidence of adaptation of optimum growth temperature. This suggests that increased microbial biomass and growth in a warming world could result in greater carbon storage. As temperatures increase, greater microbial activity may help reduce the soil carbon feedback loop. Our results provide insight on how atmospheric carbon cycling and soil health may respond in a warming world. [ABSTRACT FROM AUTHOR]

We conducted a short-term laboratory soil warming incubation experiment, sampling both warmed and un-warmed soils from a subtropical plantation in southeastern China, incubating them at 20 °C, 30 °C, and 40 °C. Our aim was to study the SOC mineralization response to increasing temperatures. Our findings revealed that the temperature sensitivity (Q10) of SOC mineralization to short-term experimental warming varied between the warmed soil and the un-warmed soil. The Q10 of the un-warmed soil escalated with the temperature treatment (20–30 °C: 1.31, 30–40 °C: 1.63). Conversely, the Q10 of the warmed soil decreased (20–30 °C: 1.57, 30–40 °C: 1.41). Increasing temperature treatments decreased soil substrate availability (dissolved organic C) in both un-warmed and warmed soil. The C-degrading enzyme in un-warmed soil and warmed soil had different trends at different temperatures. In addition, warming decreased soil microbial biomass, resulting in a decrease in the total amount of phospholipid fatty acids (PLFAs) and a decrease in the abundance of fungi and Gram-negative bacteria (GN) in both un-warmed and warmed soil. The ratio of fungal to bacterial biomass (F:B) in un-warming soil was significantly higher than that in warmed soil. A drop in the microbial quotient (qMBC) coupled with a rise in the metabolic quotient (qCO2) indicated that warming amplified microbial respiration over microbial growth. The differential Q10 of SOC mineralization in un-warmed and warmed soil, in response to temperature across varying soil, can primarily be attributed to shifts in soil dissolved organic C (DOC), alterations in C-degrading enzyme activities, and modifications in microbial communities (F:B). [ABSTRACT FROM AUTHOR]