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Biochar from biomass and waste is a valuable component of various urban green infrastructures, including green roofs, permeable pavements, green walls, and green parking lots. Incorporating biochar into substrate mixtures offers numerous benefits, including improved water retention, nutrient availability, plant growth, and carbon sequestration. Moreover, biochar plays a crucial role in stormwater management by effectively retaining and filtering stormwater, reducing runoff, mitigating urban flooding, and improving surface water quality. This study conducted a comprehensive bibliometric analysis and synthesis of the literature to provide a broad perspective of the current understanding of biochar use in green infrastructure projects, focusing on the impact of biochar on soil and environmental quality, water retention, pollutant removal and the overall performance and sustainability of green infrastructure systems. This review also provides a comprehensive synthesis of the potential of biochar in enhancing green infrastructure systems and guiding future research and implementation strategies. The insights provided in this review can guide corporate stakeholders in understanding the benefits, challenges, and applications of biochar in urban green infrastructure management, empowering them to make informed decisions and contribute to the development of sustainable and resilient urban environments aligned with the principles of the UN SDGs and ESG considerations. [ABSTRACT FROM AUTHOR]

The application of biochar to soil is widely recognized as a promising strategy for enhancing the accumulation and stability of soil organic carbon (SOC), which is crucial in mitigating climate change. However, the influence of interactions between plants and biochar on soil microbial communities and their involvement in SOC mineralization and stability remains unclear. This understanding is essential for optimizing carbon (C) sequestration in systems involving plants, soil, and biochar. In this study, employing a 13C natural abundance approach, we investigated the effect of biochar on the maize rhizosphere priming effect (RPE) in paddy soil. We also examined alterations in microbial communities and functional genes related to C degradation and fixation. Over the 99 days of maize growth, biochar application increased RPE and total SOC while decreasing dissolved organic C. It also elevated soil pH, resulting in shifts in fungal and bacterial community structure, favoring oligotrophic species. Fungal and bacterial assemblies were dominated by deterministic and stochastic processes, respectively. While the abundance of fungal guilds varied irregularly, bacterial guilds were uniformly enriched under biochar-plant interactions. Functional traits such as ecoenzymatic activities, bacterial guilds, and functional genes predominantly affected RPE under biochar application. Bacterial functional genes associated with C degradation and fixation were concurrently enhanced with biochar application. Our results indicate that interactions between plants and biochar can enhance native SOC mineralization and accumulation in a short timeframe by modulating functional traits of soil microorganisms, particularly the bacterial community involved in C degradation and fixation. Article Highlights: Biochar application altered rhizosphere priming effects by − 116.96% to + 171.59% during maize growth. Biochar application increased total soil organic carbon and boosted bacterial abundance. Biochar-plant interactions accelerated soil carbon mineralization and accumulation. [ABSTRACT FROM AUTHOR]

Forests harbor extensive biodiversity and act as a strong global carbon and nitrogen sink. Although enhancing tree diversity has been shown to mitigate climate change by sequestering more carbon and nitrogen in biomass and soils in manipulative experiments, it is still unknown how varying environmental gradients, such as gradients in resource availability, mediate the effects of tree diversity on carbon and nitrogen accrual in natural forests. Here, we use Canada's National Forest Inventory data to explore how the relationships between tree diversity and the accumulation of carbon and nitrogen in tree biomass and soils vary with resource availability and environmental stressors in natural forests. We find that the positive relationship between tree functional diversity (rather than species richness) and the accumulation of carbon in tree biomass strengthens with increasing light and soil nutrient availability. Moreover, the positive relationship between tree functional diversity and the accumulation of carbon and nitrogen in both organic and mineral soil horizons is more pronounced at sites with greater water and nutrient availabilities. Our results highlight that conserving and promoting functionally diverse forests in resource-rich environments could play a greater role than in resource-poor environments in enhancing carbon and nitrogen sequestration in Canada's forests. Tree diversity can enhance carbon and nitrogen sequestration in both biomass and soils, but its effects across different environmental conditions remain unclear. This study shows that promoting tree functional diversity can increase carbon and nitrogen accumulation more in resource-rich environments. [ABSTRACT FROM AUTHOR]

Background and Aims: Roots are of critical importance to plants due to their role in absorbing soil water and nutrients and adapting to ever-changing environmental conditions. Grazing changes plant and soil conditions and can affect root growth and resource utilization strategies. However, it is still unclear how grazing intensity affects plant root traits in desert steppes, especially by altering soil resource availability. Methods: Here, we studied the effect of four levels of grazing intensity, including no grazing (CK), light grazing (LG), moderate grazing (MG), and heavy grazing (HG), on the root traits of Stipa breviflora and soil physical, chemical, and microbial properties in a desert steppe dominated by S. breviflora under in Siziwang Banner, Inner Mongolia, China. Results: Compared to the CK treatment, all grazing treatments significantly reduced root diameter, and increased root length density and root-to-shoot ratio, but did not affect root nitrogen concentration and tissue density. The light grazing treatment significantly increased the root fractal dimension, root fractal abundance, and root biomass. The heavy grazing treatment significantly increased specific root length and root fractal abundance. Principal component analysis revealed that grazing influenced the root-mycorrhizal "collaboration" gradient, shifting root resources utilization strategies from "outsourcing" in the CK to "do-it-yourself" in the grazed plots. Structural equation modeling showed that shifts in root traits were mainly associated with changes in soil pH, ammonium nitrogen availability, and microbial diversity under grazing. Conclusions: Under increasing grazing intensity, S. breviflora adapted to higher soil pH and lower nitrogen availability by producing longer, thinner, more branching roots and a "do-it-yourself" strategy. Our results suggest that changes in root traits play a very important role in the adaption of a dominant desert steppe plant to grazing intensity. [ABSTRACT FROM AUTHOR]

Anthropogenic land‐use practices influence ecosystem functions and the environment. Yet, the effect of global land‐use change on ecosystem nitrogen (N) cycling remains unquantified despite that ecosystem N cycling plays a critical role in maintaining food security. Here, we analysed 2430 paired observations globally to show that converting natural to managed ecosystems increases ratios of autotrophic nitrification to ammonium immobilisation and nitrate to ammonium, but decreases soil immobilisation of mineral N, causing increased N losses via leaching and gaseous N emissions, such as nitrous oxide (e.g., via denitrification), resulting in a leaky N cycle. Changing land use from intensively managed to one that resembles natural ecosystems reversed N losses by 108% on average, resulting in a more conservative N cycle. Structural equation modelling revealed that changes in soil organic carbon, pH and carbon to N ratio were more important than changes in soil moisture content and temperature in predicting ecosystem N retention capacities following land‐use conversion and its reversion. The hotspots of leaky N cycles were mostly in equatorial and tropical regions, as well as in Western Europe, the United States and China. Our results suggest that whether an ecosystem exhibits a conservative N cycle after land‐use reversion depends on management practices. [ABSTRACT FROM AUTHOR]

Purpose: The influence of organic amendments on the interplay among soil extracellular enzyme activities (EEAs) and their stoichiometry (EES) and nutrient availabilities, key indicators of resource limitations for soil microbes, is poorly understood. This study aims to investigate how manure compost (hereafter "manure") and its biochar derivative affect EEAs, EES and soil fertility. Materials and methods: We studied EEAs (BG, β-glucosidase; CBH, cellobiohydrolase; LAP, Leucine aminopeptidase; NAG, β-1,4-N-acetylglucosaminidase and AP, acid phosphatase), EES and soil fertility two years post-application of manure and biochar in central Alberta, Canada. Results and discussion: Applying manure and its biochar did not affect soil permanganate oxidable carbon (C), total phosphorus (P), and available P and nitroegn (N). Manure application increased NAG activity by 13.9% (75.9 nmol h−1 g−1 soil) relative to the control (66.6 nmol h−1 g−1 soil), whereas biochar application increased LAP activity by 22.1% (64.6 nmol h−1 g−1 soil) compared to the manure treatment (52.9 nmol h−1 g−1 soil), suggesting that manure addition caused microbial C limitation, while biochar addition led to microbial N limitation. However, both manure and biochar treatments did not affect soil NAG, CBH and AP, and enzymatic C:N, C:P, and N:P stoichiometry. Manure and biochar and their interactions with the soil ultimately affect soil physicochemical properties. Conclusions: Manure and its biochar differentially altered some soil N-cycling EEAs and C and N limitations two years after their applications. [ABSTRACT FROM AUTHOR]

Despite that biodegradable plastics are perceived as environmentally friendly, there is a lack of comprehensive understanding of their fate in soil. Current Environmental, Social, and Governance (ESG) frameworks, along with new UNEP regulations on plastic pollution, necessitate scientific information on plastic degradation in soils for developing sustainable biodegradable plastics. In this study, we examined the degradation rates of two biodegradable plastics, poly(butylene adipate‐co‐terephthalate) (PBAT) and poly(lactic acid) (PLA), in a laboratory microcosm experiment using uncontaminated soil, with PBAT or PLA added at 8.3% (w/w). Our aim was to further understand the impact of these plastic types on soil properties and microbial communities under different incubation temperatures. Both PBAT and PLA treatments elevated cumulative CO2 efflux compared with the control soil incubated at 25 and 58°C. After 33 weeks, 9.2% and 6.1% of the added PBAT and PLA degraded, respectively, at 58°C, while only 2.3% of PBAT and 1.7% of PLA degraded at 25°C, implying slower degradation rates of PBAT and PLA under the lower temperature. Degradation at 58°C increased total soil carbon by 0.6%, 1.9%, and 4.3% for Control, PBAT, and PLA, respectively, and soil electrical conductivity by 0.17, 0.33, and 2.38 dS m−1, respectively, but decreased soil pH. Microbial diversity and richness decreased under thermophilic conditions at 58°C compared with that at 25°C. We conclude that the degradation of PBAT and PLA varies with environmental condition, and influences soil properties. [ABSTRACT FROM AUTHOR]

One strategy to reduce CO2 emissions from cement production is to reduce the amount of Portland cement produced by replacing it with supplementary cementitious materials (SCMs). Biochar is a potential SCM that is an eco-friendly and stable porous pyrolytic material. However, the effects of biochar addition on the performances of Portland cement composites are not fully understood. This meta-analysis investigated the impact of biochar addition on the 7- and 28-day compressive strength of Portland cement composites based on 606 paired observations. Biochar feedstock type, pyrolysis conditions, pre-treatments and modifications, biochar dosage, and curing type all influenced the compressive strength of Portland cement composites. Biochars obtained from plant-based feedstocks (except rice and hardwood) improved the 28-day compressive strength of Portland cement composites by 3–13%. Biochars produced at pyrolysis temperatures higher than 450 °C, with a heating rate of around 10 C min-1, increased the 28-day compressive strength more effectively. Furthermore, the addition of biochar with small particle sizes increased the compressive strength of Portland cement composites by 2–7% compared to those without biochar addition. Biochar dosage of < 2.5% of the binder weight enhanced both compressive strengths, and common curing methods maintained the effect of biochar addition. However, when mixing the cement, adding fine and coarse aggregates such as sand and gravel affects the concrete and mortar's compressive strength, diminishing the effect of biochar addition and making the biochar effect nonsignificant. We concluded that appropriate biochar addition could maintain or enhance the mechanical performance of Portland cement composites, and future research should explore the mechanisms of biochar effects on the performance of cement composites. Highlights: Biochar effects on Portland cement composites were studied through a meta-analysis. Effects of biochar production condition, modification and pre-treatment were studied. The above parameters affected the compressive strength of Portland cement composites. Biochar addition effects were dependent on batch designs of Portland cement composites. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "Biochar affects compressive strength of Portland cement composites: a meta-analysis." The correction states that the positions of certain figures in the original article were incorrectly reversed. The corrected figures show the effect sizes of biochar addition on the compressive strength of Portland cement composites at different time intervals, as influenced by various factors. The original article has been updated to reflect these corrections. [Extracted from the article]

Microplastics (MPs) are emerging contaminants that adversely affect environmental health. In this review, we discuss the uptake of MPs by plants via endocytosis and crack-entry pathways in the roots and stomata of leaves; the translocation of MPs via xylem and phloem; and the toxicity of MPs to diverse plant species through oxidative stress, inhibition of photosynthesis, cytotoxicity, and genotoxicity. It's difficult to assess the health risks of MPs because they directly cause toxicity and also change soil properties and the bioavailability of coexisting pollutants, such as plastic additives, in the plant rhizosphere, and bioaccumulate along the food chain. Moreover, compared to the uptake behavior and phytotoxicity effects of MPs in laboratory and hydroponic studies, MPs of various shapes, sizes, and types are likely to cause different effects on plants in complex natural environments. This review proposes potential phytoremediation strategies, including phytoextraction, immobilization, and rhizoremediation, for MP pollutants and provides guidelines for the bioremediation of MP-contaminated environments to enhance environmental sustainability. In the phytoremediation of MP pollution, the selection and disposal of plants used for phytoremediation and the optimization of functional microbes in the rhizosphere remain challenging. Future studies should address knowledge gaps in (i) methods for determining environmentally-relevant concentrations of MPs, (ii) the assessment of the ecological and human health risks of MPs in the natural environment, and (iii) the development of effective strategies for the phytoremediation of MP pollution. [ABSTRACT FROM AUTHOR]

The effects of long-term biochar application on soil phosphorus (P) flux across the root-soil interface and its availability in the rhizosphere of rice (Oryza sativa L) remain unclear. We used diffusive gradients in thin films (DGT), laser ablation-inductively coupled plasma mass spectrometry, and planar optode sensor techniques to characterize, in-situ, the 2D heterogeneity and dynamics of rhizosphere soil P, iron (Fe), sulfur (S) and trace element fluxes, dissolved oxygen and pH in paddy soil, after 10 years of biochar application. Compared to the control (no biochar applied), biochar applied at 4.5, 22.5 and 45.0 Mg ha−1 yr−1 decreased rhizospheric P fluxes by 11.6%, 63.4% and 79.0%, respectively. This decrease under biochar treatments was attributed to changed redox status of Fe and S caused by the lower dissolved oxygen in rhizosphere soil and increased soil pH induced precipitating of soluble inorganic P into insoluble P forms, such as calcium-bound and residual P that are unavailable for crop uptake. Higher application rate of biochar resulted in lower As and Pb fluxes in rice rhizosphere and their availabilities for crop uptake. The in-situ observation results in rice rhizosphere at μm-scale after 10 years of biochar addition directly showed the complex effects of long-term biochar and rhizosphere heterogeneity on P transformation process. Highlights: In-situ 2D imaging of rice rhizosphere P, Fe, S, and trace elements was elucidated. Long-term biochar application conspicuously lowered rice rhizosphere available P. Soil P release process was related to Fe and S redox status. [ABSTRACT FROM AUTHOR]

One strategy to reduce CO2 emissions from cement production is to reduce the amount of Portland cement produced by replacing it with supplementary cementitious materials (SCMs). Biochar is a potential SCM that is an eco-friendly and stable porous pyrolytic material. However, the effects of biochar addition on the performances of Portland cement composites are not fully understood. This meta-analysis investigated the impact of biochar addition on the 7- and 28-day compressive strength of Portland cement composites based on 606 paired observations. Biochar feedstock type, pyrolysis conditions, pre-treatments and modifications, biochar dosage, and curing type all influenced the compressive strength of Portland cement composites. Biochars obtained from plant-based feedstocks (except rice and hardwood) improved the 28-day compressive strength of Portland cement composites by 3–13%. Biochars produced at pyrolysis temperatures higher than 450 °C, with a heating rate of around 10 C min-1, increased the 28-day compressive strength more effectively. Furthermore, the addition of biochar with small particle sizes increased the compressive strength of Portland cement composites by 2–7% compared to those without biochar addition. Biochar dosage of < 2.5% of the binder weight enhanced both compressive strengths, and common curing methods maintained the effect of biochar addition. However, when mixing the cement, adding fine and coarse aggregates such as sand and gravel affects the concrete and mortar's compressive strength, diminishing the effect of biochar addition and making the biochar effect nonsignificant. We concluded that appropriate biochar addition could maintain or enhance the mechanical performance of Portland cement composites, and future research should explore the mechanisms of biochar effects on the performance of cement composites. Highlights: Biochar effects on Portland cement composites were studied through a meta-analysis. Effects of biochar production condition, modification and pre-treatment were studied. The above parameters affected the compressive strength of Portland cement composites. Biochar addition effects were dependent on batch designs of Portland cement composites. [ABSTRACT FROM AUTHOR]

Highly diverse exoenzymes mediate the energy flow from substrates to the multitrophic microbiota within the soil decomposer micro‐food web. Here, we used a "soil enzyme profile analysis" approach to establish a series of enzyme profile indices; those indices were hypothesized to reflect micro‐food web features. We systematically evaluated the shifts in enzyme profile indices in relation to the micro‐food web features in the restoration of an abandoned cropland to a natural area. We found that enzymatic C:N stoichiometry and decomposability index were significantly associated with substrate availability. Furthermore, the higher Shannon diversity index in the exoenzyme profile, especially for the C‐degrading hydrolase, corresponded to a greater microbiota community diversity. The increased complexity and stability of the exoenzyme network reflected similar changes with the micro‐food web networks. In addition, the gross activity of the enzyme profile as a parameter for soil multifunctionality, effectively predicted the substrate content, microbiota community size, diversity, and network complexity. Ultimately, the proposed enzymic channel index was closely associated with the traditional decomposition channel indices derived from microorganisms and nematodes. Our results showed that soil enzyme profile analysis reflected very well the decomposer food web features. Our study has important implications for projecting future climate change or anthropogenic disturbance impacts on soil decomposer micro‐food web features by using soil enzyme profile analysis. Highlights: Soil enzyme profile analysis for indicating decomposer micro‐food web features was first proposed.Diversity indication utilities for contrasting enzyme profiles were different.Protozoa channel index and enzymatic channel index were proposed. [ABSTRACT FROM AUTHOR]

Converting natural forests to agricultural lands has been widespread globally due to increasing population and the demand for food. Phosphorus (P) is often applied to agricultural lands in excessive amounts which can saturate the natural P sorption capacity of the soil, leading to P leaching and subsequent off‐site water eutrophication. We studied the effect of land‐use conversion from natural forests to tea plantations on total soil P, P fractions, and P sorption capacity in subtropical China. Compared to natural forests, total soil P concentrations increased significantly in both 0–20 and 20–40 cm depths in tea plantations, indicative of the accumulation of P fertilizer. The increases in total soil P were primarily found in NaOH‐extractable inorganic P and residual P fractions in both depths, suggesting that P fertilizer was sorbed and occluded into more stable forms due to the high abundance of sorbents (i.e., iron [Fe], aluminum [Al] minerals, and clay). Across all soil samples, oxalate‐extractable Fe was the best predictor of soil maximum P sorption capacity (r = 0.94, p < 0.001). Surprisingly, the conversion from natural forests to tea plantations decreased both oxalate‐extractable Fe concentration and soil maximum P sorption capacity, hereby increasing the degree of P saturation in soils. Depletion of P sorbents (i.e., soil amorphous Fe) is likely a consequence of Fe removal through tea production and soil erosion, indicating soil degradation. Plantation soils have also shown other signs of degradation including the loss of nutrients (e.g., total soil nitrogen and oxalate‐extractable calcium) and soil organic matter. Our results demonstrate that the conversion of natural forests to tea plantations reduced the ability of the soil to sorb P by both saturating the natural P sorption capacity and depleting P sorbents. Soil degradation resulting from land‐use conversion has increased the environmental risk of P leaching loss, emphasizing the need for improved P fertilization management. [ABSTRACT FROM AUTHOR]

The incorporation of organic amendments, such as food waste (FW) and biochar, into soil is an established agronomic practice known for enhancing soil fertility and improving overall soil health. However, the individual and combined effects of FW and biochar on soil properties in microplastic (MP)-contaminated soil–plant systems remain poorly understood. To address this knowledge gap, we conducted a field experiment to investigate the individual and combined effects of polystyrene MPs, FW, and FW-derived biochar on soil properties and lettuce growth. Soil chemical properties were unaffected by the addition of MPs. However, the application of FW and biochar increased the soil pH, with the highest pH (8.2) observed in the combined treatment of biochar and MPs. Despite the presence of MPs, FW application resulted in notable increases in soil electrical conductivity (EC; 2.04 dS m−1), available nitrogen (NO3−–N: 325.5 mg kg−1, NH4+–N: 105.2 mg kg−1), available phosphorus (88.4 mg kg−1), and total exchangeable cations (18.6 cmol(+) kg−1). However, these values decreased after lettuce cultivation. In soil cultivated with lettuce, the coexistence of MPs and biochar reduced soil Fluorescein diacetate hydrolase enzyme activity by 46.2% and urease activity by 94.0%. FW addition doubled acid phosphatase activity, whereas FW and its coexistence with MPs decreased alpha diversity. The relative abundance of Actinobacteria decreased with MP application, whereas that of Acidobacteria and Actinobacteria decreased with FW treatment. Gemmatimonadetes and Nitrospirae decreased in soil treated with FW and biochar. The highest relative abundances of Firmicutes and Proteobacteria were observed in the FW-added soils, and Planctomycetes were the highest in the biochar-added soils. FW application negatively affected lettuce growth. Overall, the coexistence of MPs with FW or biochar had limited effects on soil properties and lettuce growth, with FW and biochar serving as the primary factors in modifying soil–plant systems. Future studies should investigate the effects of different MPs and their interactions with organic soil amendments on soil properties and crop growth under different management practices. [ABSTRACT FROM AUTHOR]

Microplastic (MP) pollution in agricultural soils, resulting from the use of plastic mulch, compost, and sewage sludge, jeopardizes the soil microbial populations. However, the effects of MPs on soil chemical properties and microbial communities remain largely unknown. Here, we investigated the effects of different concentration levels (0, 0.1, 1, 3, 5, and 7%; w:w) of low-density polyethylene (LDPE) MPs on the chemical properties and bacterial communities of agricultural soil in an incubation study. The addition of LDPE MPs did not drastically change soil pH (ranging from 8.22 to 8.42). Electrical conductivity increased significantly when the LDPE MP concentrations were between 1 and 7%, whereas the total exchangeable cations (Na+, K+, Mg2+, and Ca2+) decreased significantly at higher LDPE MP concentrations (3–7%). The highest available phosphorus content (2.13 mg kg−1) was observed in 0.1% LDPE MP. Bacterial richness (Chao1 and Ace indices) was the lowest at 0.1% LDPE MP, and diversity indices (Shannon and Invsimpson) were higher at 0 and 1% LDPE MP than at other concentrations. The effect of LDPE MP concentrations on bacterial phyla remained unchanged, but the bacterial abundance varied. The relative abundance of Proteobacteria (25.8–33.0%) was the highest in all treatments. The abundance of Acidobacteria (15.8–17.2%) was also high, particularly in the 0, 0.1, and 1% LDPE MPs. With the increase in LDPE MP concentration, the abundance of Actinobacteria gradually increased from 7.80 to 31.8%. Our findings suggest that different MP concentration levels considerably alter soil chemical properties and microbial composition, which may potentially change the ecological functions of soil ecosystems. [ABSTRACT FROM AUTHOR]

Biochar has been widely recommended as an effective soil amendment for reducing nitrous oxide (N2O) emissions and nitrogen (N) leaching. However, the effects of biochar application to Lei bamboo plantations on soil N2O emissions and N leaching remain unclear. These effects on soil N2O emissions and N leaching were investigated in the present study using five treatments applied with the same amount of N: rice husk at 10 t ha−1 (10H) and 30 t ha−1 (30H), biochar at 10 t ha−1 (10B) and 30 t ha−1 (30B), and no additions (control, CK). Both the 10H and 30H treatments significantly increased cumulative N2O emissions compared to the CK treatment, with an increment of 0.78 and 2.20 kg N ha−1, respectively. The 30B treatment significantly reduced cumulative N2O emissions by 0.90 kg N ha−1, whereas the 10B treatment had no significant effect. The reduction in N2O emissions following the high-rate biochar addition was probably due to the increased pH and the total abundance of nosZ I and nosZ II genes. The 30H treatment significantly increased nitrate N (NO3−–N) and dissolved organic N (DON) leaching by 38% and 170% respectively compared to the CK treatment, and had the largest N loss via N2O emissions and N leaching, while the 30B treatment had the lowest N loss. Partial least squares path modeling revealed that soil chemical properties [ammonium nitrogen (NH4+–N), NO3−–N, DON, dissolved organic C (DOC), total N (TN), soil organic C (SOC), and pH] dominantly affected soil N2O emissions, while the total abundance of denitrifying genes (nirS, nirK, nosZ I, and nosZ II) were the key factors involved in reducing NO3−–N leaching. There was a strong positive correlation between cumulative N2O emissions and N leaching loss, which may be related to excessive N surplus in the soil. Our results suggest that the replacement of rice husk by its biochar at a high-rate would reduce the risk of N2O emissions and N leaching loss effectively from Lei bamboo forests in subtropical China. [ABSTRACT FROM AUTHOR]

Microplastic (MP) pollution in agricultural soils, resulting from the use of plastic mulch, compost, and sewage sludge, jeopardizes the soil microbial populations. However, the effects of MPs on soil chemical properties and microbial communities remain largely unknown. Here, we investigated the effects of different concentration levels (0, 0.1, 1, 3, 5, and 7%; w:w) of low-density polyethylene (LDPE) MPs on the chemical properties and bacterial communities of agricultural soil in an incubation study. The addition of LDPE MPs did not drastically change soil pH (ranging from 8.22 to 8.42). Electrical conductivity increased significantly when the LDPE MP concentrations were between 1 and 7%, whereas the total exchangeable cations (Na+, K+, Mg2+, and Ca2+) decreased significantly at higher LDPE MP concentrations (3–7%). The highest available phosphorus content (2.13 mg kg−1) was observed in 0.1% LDPE MP. Bacterial richness (Chao1 and Ace indices) was the lowest at 0.1% LDPE MP, and diversity indices (Shannon and Invsimpson) were higher at 0 and 1% LDPE MP than at other concentrations. The effect of LDPE MP concentrations on bacterial phyla remained unchanged, but the bacterial abundance varied. The relative abundance of Proteobacteria (25.8–33.0%) was the highest in all treatments. The abundance of Acidobacteria (15.8–17.2%) was also high, particularly in the 0, 0.1, and 1% LDPE MPs. With the increase in LDPE MP concentration, the abundance of Actinobacteria gradually increased from 7.80 to 31.8%. Our findings suggest that different MP concentration levels considerably alter soil chemical properties and microbial composition, which may potentially change the ecological functions of soil ecosystems. [ABSTRACT FROM AUTHOR]

Purpose: The effects of nitrogen (N) deposition and leaf litter addition on soil carbon (C) cycling have been widely studied. However, soil carbon dioxide (CO2) emissions linked to N deposition, leaf litter decomposition, soil microbial biomass, and enzyme activity remain poorly understood. Therefore, the objective of this study was to investigate the interactive effects of N and leaf litter addition on soil CO2 emissions. Materials and methods: We conducted a 180-day laboratory incubation experiment by adding Moso bamboo (Phyllostachys edulis) leaf litter and ammonium nitrate (NH4NO3, equivalent to 50 kg N ha−1 yr−1), both alone and in combination with one another, to the soil collected from a Moso bamboo forest in subtropical China. Results and discussion: After 180 days of incubation, the sole leaf litter addition significantly increased cumulative soil CO2 emissions by 207%, whereas the sole addition of N did not significantly affect. However, the combined effect of N and leaf litter addition on soil CO2 emissions was antagonistic. The addition of leaf litter alone enhanced dissolved organic C (DOC), total inorganic N, and microbial biomass C (MBC) concentrations in the soil. Nonetheless, the combined addition of N and leaf litter reduced lignin decomposition, soil MBC concentration, soil DOC, and soil C-degrading enzyme activities in comparison to leaf litter addition alone. Conclusions: The present study indicates that although the addition of leaf litter stimulates soil CO2 emissions, the deposition of atmospheric N can reduce this stimulatory effect and promote lignin accumulation in Moso bamboo forest soils. [ABSTRACT FROM AUTHOR]

The extensive use of organic chemicals has resulted in the widespread distribution of hydrocarbon contaminants (HCs) in many ecosystems on a global scale. Many subterranean ecosystems can rapidly become anaerobic or even methanogenic following hydrocarbon contamination. Bacteria and archaea dominate communities in such systems and mediate the syntrophic processes that transform HCs into methane (CH4). The resulting CH4 is oxidized by anaerobic bacteria and archaea, either jointly or individually, in the presence of electron acceptors (e.g., sulfate, nitrate, nitrite, manganese, or ferric iron), a process that reduces CH4 emissions and, as a result, contributes to climate change mitigation. Although the possibility of the syntrophy of bacteria and archaea in the anaerobic transformation of HCs and methane oxidation is widely established, the specific pathways and syntrophic taxa involved are poorly understood. This paper reviews the syntrophy of bacteria and archaea in anaerobic HC degradation, with a focus on methanogenic processes. In addition, we discuss the role of bacteria and archaea in the anaerobic oxidation of methane (AOM) and its environmental significance. Given that much of the biotransformation of HCs driven by methanogenic and methanotrophic processes remains unknown, we propose a way forward to discover novel syntrophic partners and metabolic pathways in such anoxic systems. [ABSTRACT FROM AUTHOR]

Increasing soil carbon and nitrogen storage can help mitigate climate change and sustain soil fertility1,2. A large number of biodiversity-manipulation experiments collectively suggest that high plant diversity increases soil carbon and nitrogen stocks3,4. It remains debated, however, whether such conclusions hold in natural ecosystems5–12. Here we analyse Canada’s National Forest Inventory (NFI) database with the help of structural equation modelling (SEM) to explore the relationship between tree diversity and soil carbon and nitrogen accumulation in natural forests. We find that greater tree diversity is associated with higher soil carbon and nitrogen accumulation, validating inferences from biodiversity-manipulation experiments. Specifically, on a decadal scale, increasing species evenness from its minimum to maximum value increases soil carbon and nitrogen in the organic horizon by 30% and 42%, whereas increasing functional diversity enhances soil carbon and nitrogen in the mineral horizon by 32% and 50%, respectively. Our results highlight that conserving and promoting functionally diverse forests could promote soil carbon and nitrogen storage, enhancing both carbon sink capacity and soil nitrogen fertility.Analysis of data from the Canadian National Forest Inventory database suggests that greater tree diversity in natural forests is associated with increases in soil carbon and nitrogen stocks. [ABSTRACT FROM AUTHOR]

Species mixtures have been widely reported to increase aboveground productivity; however, how tree species mixtures affect root systems in natural forests remains unclear. We hypothesize that mixtures have a greater fine root length compared to single species‐dominated stands to support their greater productivity.Here, we collected monthly root images from the minirhizotrons installed in 18 stands either dominated by Populus tremuloides, Pinus banksiana, and their mixtures for three years (2015–2017) in post‐fire boreal forests of two stand ages (8 and 34 years old) to test our hypotheses.We found that the fine root length was higher in mixtures than in single species‐dominated stands, and the magnitude of mixture effects was greater in the 34‐ than in the 8‐year‐old stands in the third year. The mixture effects on fine root length revealed a positive relationship with forest net primary productivity. Root length production, which is the growth of new roots within a year, was not affected by tree species mixtures except for the 8‐year‐old stand in 2015. Tree species mixtures did not affect root length turnover. Root length and root biomass were not significantly correlated at stand level.Synthesis. Our results show that tree species mixtures positively affect fine root length, with that positive effect increasing with stand development in the studied natural forests. Our results suggest that the greater root length in species mixtures supported the greater forest productivity in species mixtures as the greater root length benefits plant uptake of nutrients and water. Therefore, conserving tree species diversity has implications for improving forest productivity and carbon sequestration in forest ecosystems. [ABSTRACT FROM AUTHOR]

Forest soil CO2 efflux (FCO2) is a crucial process in global carbon cycling; however, how FCO2 responds to disturbance regimes in different forest biomes is poorly understood. We quantified the effects of disturbance regimes on FCO2 across boreal, temperate, tropical and Mediterranean forests based on 1240 observations from 380 studies. Globally, climatic perturbations such as elevated CO2 concentration, warming and increased precipitation increase FCO2 by 13% to 25%. FCO2 is increased by forest conversion to grassland and elevated carbon input by forest management practices but reduced by decreased carbon input, fire and acid rain. Disturbance also changes soil temperature and water content, which in turn affect the direction and magnitude of disturbance influences on FCO2. FCO2 is disturbance‐ and biome‐type dependent and such effects should be incorporated into earth system models to improve the projection of the feedback between the terrestrial C cycle and climate change. [ABSTRACT FROM AUTHOR]

Responses of the terrestrial biosphere to rapidly changing environmental conditions are a major source of uncertainty in climate projections. In an effort to reduce this uncertainty, a wide range of global change experiments have been conducted that mimic future conditions in terrestrial ecosystems, manipulating CO2, temperature, and nutrient and water availability. Syntheses of results across experiments provide a more general sense of ecosystem responses to global change, and help to discern the influence of background conditions such as climate and vegetation type in determining global change responses. Several independent syntheses of published data have yielded distinct databases for specific objectives. Such parallel, uncoordinated initiatives carry the risk of producing redundant data collection efforts and have led to contrasting outcomes without clarifying the underlying reason for divergence. These problems could be avoided by creating a publicly available, updatable, curated database. Here, we report on a global effort to collect and curate 57,089 treatment responses across 3644 manipulation experiments at 1145 sites, simulating elevated CO2, warming, nutrient addition, and precipitation changes. In the resulting Manipulation Experiments Synthesis Initiative (MESI) database, effects of experimental global change drivers on carbon and nutrient cycles are included, as well as ancillary data such as background climate, vegetation type, treatment magnitude, duration, and, unique to our database, measured soil properties. Our analysis of the database indicates that most experiments are short term (one or few growing seasons), conducted in the USA, Europe, or China, and that the most abundantly reported variable is aboveground biomass. We provide the most comprehensive multifactor global change database to date, enabling the research community to tackle open research questions, vital to global policymaking. The MESI database, freely accessible at doi.org/10.5281/zenodo.7153253, opens new avenues for model evaluation and synthesis‐based understanding of how global change affects terrestrial biomes. We welcome contributions to the database on GitHub. [ABSTRACT FROM AUTHOR]

The accumulation of phytolith-occluded carbon (PhytOC) in Moso bamboo could be a novel long-term carbon sequestration strategy. The objective of this study was to investigate the effects of temperature change and different fertilization on PhytOC accumulation. The pot experiment was established with different fertilization (including control (CK), nitrogen fertilizers (N), silicon fertilizers (Si), and a combination of nitrogen and silicon (NSi)) under high- and low-temperature. Despite the different fertilization, the PhytOC accumulation of the high-temperature group increases by 45.3% on average compared with the low-temperature group, suggesting higher temperature is greatly beneficial to the PhytOC accumulation. Fertilization significantly increases the accumulation of PhytOC (increased by 80.7% and 48.4% on average for the low- and high-temperature group, respectively) compared with CK. However, the N treatment increased both Moso bamboo biomass and PhytOC accumulation. The difference in the accumulation of PhytOC in Si and NSi was insignificant, indicating the combination of N and Si didn't bring extra benefit to PhytOC accumulation compared to Si fertilizer alone. These results indicated the application of nitrogen fertilizer is a practical and effective method for enhancing long-term carbon sequestration for Moso bamboo. Based on our study, we conclude that global warming poses a positive effect on promoting the long-term carbon sequestration of Moso bamboo. [ABSTRACT FROM AUTHOR]

Converting rice husk to biochar is one of the solutions to manage crop residues by transforming waste into a value-added material that has broad benefits to the environment when biochar is applied to the soil. This study investigated the impact of the application of rice husk and its biochar at different doses (i.e., 0, 10, and 30 t ha−1) on soil carbon stability, the property of water-soluble soil organic matter, and the abundance and diversity of microbial communities in a Lei bamboo (Phyllostachys praecox) forest soil 262 days after their application. The application of rice husk, especially at 30 t ha−1, increased dissolved organic carbon due to the high labile carbon (C) (e.g., cellulose, hemicellulose, polysaccharides) content in the rice husk. The biochar treatments stimulated the release of humic-like substances (e.g., (poly) phenols) into the soil solution, increased the aromatic C content by 412–557%, and increased the relative abundance of Chloroflexi, Planctomycetota, and Proteobacteria compared to the control. This study shows that biochar application, particularly at 30 t ha−1, enhanced the C stability by turning organic C into recalcitrant forms in the soil, demonstrating the merit of converting rice husk into biochar before its application to the soil. [ABSTRACT FROM AUTHOR]

Changes in precipitation regimes can strongly affect soil nitrogen (N) cycling in terrestrial ecosystems. However, whether altered precipitation regimes may differentially affect soil N cycling between arid and humid biomes at the global scale is unclear. We conducted a meta‐analysis using 1036 pairwise observations collected from 194 publications to assess the effects of increased and decreased precipitation on the input (N return from plants), storage (various forms of N in soil), and output (gaseous N emissions) of soil N in arid versus humid biomes at the global scale. We found that (1) increased precipitation significantly increased N input (+12.1%) and output (+34.9%) but decreased N storage (−13.7%), while decreased precipitation significantly decreased N input (−10.7%) and output (−34.8%) but increased N storage (+11.1%); (2) the sensitivity of soil N cycling to increased precipitation was higher in arid regions than in humid regions, while that to decreased precipitation was lower in arid regions than in humid regions; (3) the effect of altered precipitation regimes on soil N cycling was independent of precipitation type (i.e., rainfall vs. snowfall); and (4) the mean annual precipitation regulated soil N cycling in precipitation alteration experiments at the global scale. Overall, our results clearly show that the response of soil N cycling to increased versus decreased precipitation differs between arid and humid regions, indicating the uneven effect of climate change on soil N cycling between these two contrasting climate regions. This implies that ecosystem models need to consider the differential responses of N cycling to altered precipitation regimes in different climatic conditions under future global change scenarios. [ABSTRACT FROM AUTHOR]

Soil microbes make up a significant portion of the genetic diversity and play a critical role in belowground carbon (C) cycling in terrestrial ecosystems. Soil microbial diversity and organic C are often tightly coupled in C cycling processes; however, this coupling can be weakened or broken by rapid global change. A global meta‐analysis was performed with 1148 paired comparisons extracted from 229 articles published between January 1998 and December 2021 to determine how nitrogen (N) fertilization affects the relationship between soil C content and microbial diversity in terrestrial ecosystems. We found that N fertilization decreased soil bacterial (−11%) and fungal diversity (−17%), but increased soil organic C (SOC) (+19%), microbial biomass C (MBC) (+17%), and dissolved organic C (DOC) (+25%) across different ecosystems. Organic N (urea) fertilization had a greater effect on SOC, MBC, DOC, and bacterial and fungal diversity than inorganic N fertilization. Most importantly, soil microbial diversity decreased with increasing SOC, MBC, and DOC, and the absolute values of the correlation coefficients decreased with increasing N fertilization rate and duration, suggesting that N fertilization weakened the linkage between soil C and microbial diversity. The weakened linkage might negatively impact essential ecosystem services under high rates of N fertilization; this understanding is important for mitigating the negative impact of global N enrichment on soil C cycling. [ABSTRACT FROM AUTHOR]

Biochar application to the soil is a novel approach to carbon sequestration. Biochar application affects the emission of greenhouse gases (GHGs), such as CO2, CH4, and N2O, from different environments (e.g., upland soils, rice paddies and wetlands, and composting environments). In this review, the effect of biochar on GHGs emissions from the above three typical environments are critically evaluated based on a literature analysis. First, the properties of biochar and engineered biochar related to GHGs emissions was reviewed, targeting its relationship with climate change mitigation. Then, a meta‐analysis was conducted to assess the effect of biochar on the emissions of CO2, CH4, and N2O in different environments, and the relevant mechanisms. Several parameters were identified as the main influencing factors in the meta‐analysis, including the pH of the biochar, feedstock type, pyrolysis temperature, biochar application rate, C/N ratio of the biochar, and experimental scale. An overall suppression effect among different environments was found, in the following order for different greenhouse gases: N2O > CH4 > CO2. We conclude that biochar can change the physicochemical properties of soil and compost in different environments, which further shapes the microbial community in a specific environment. Biochar addition affects CO2 emissions by influencing oligotrophic and copiotrophic bacteria; CH4 emissions by regulating the abundance of functional genes, such as mcrA (a methanogen) and pmoA (a methanotroph); and N2O emissions by controlling N‐cycling functional genes, including amoA, nirS, nirK, nosZ. Finally, future research directions for mitigating greenhouse gas emissions through biochar application are suggested. [ABSTRACT FROM AUTHOR]

Moreover, soil acidification, with soil pH ranging from 4.0 to 4.5, simplified network structure and compelled denitrifiers to cooperate with each other in contrast with other soil pH ranges. Soil tillage practices and the resulting increase in water erosion is one of the most important anthropogenic processes to drive soil nutrients and SOC turnover in agricultural land. Abbreviations AOC aggregate-associated carbon iPOC intra-aggregate particulate organic carbon OC organic carbon SOC soil organic carbon SOM soil organic matter Mollisols are inherently productive and fertile soils that are extensively distributed on the steppes of North America, South America, Ukraine, and Northeast China. [Extracted from the article]

Agroforestry systems (AFS) contribute to carbon (C) sequestration and reduction in greenhouse gas emissions from agricultural lands. However, previously understudied differences among AFS may underestimate their climate change mitigation potential. In this 3‐year field study, we assessed various C stocks and greenhouse gas emissions across two common AFS (hedgerows and shelterbelts) and their component land uses: perennial vegetated areas with and without trees (woodland and grassland, respectively), newly planted saplings in grassland, and adjacent annual cropland in central Alberta, Canada. Between 2018 and 2020 (~April–October), nitrous oxide emissions were 89% lower under perennial vegetation relative to the cropland (0.02 and 0.18 g N m−2 year−1, respectively). In 2020, heterotrophic respiration in the woodland was 53% lower in shelterbelts relative to hedgerows (279 and 600 g C m−2 year−1, respectively). Within the woodland, deadwood C stock was particularly important in hedgerows (35 Mg C ha−1 or 7% of ecosystem C) relative to shelterbelts (2 Mg C ha−1 or <1% of ecosystem C), and likely affected C cycling differences between the woodland types by enhancing soil labile C and microbial biomass in hedgerows. Deadwood C stock was positively correlated with annual heterotrophic respiration and total (to ~100 cm depth) soil organic C, water‐soluble organic C, and microbial biomass C. Total ecosystem C was 1.90–2.55 times greater within the woodland than all other land uses, with 176, 234, 237, and 449 Mg C ha−1 found in the cropland, grassland, planted saplings treatment, and woodland, respectively. Shelterbelt and hedgerow woodlands contained 2.09 and 3.03 times more C, respectively, than adjacent cropland. Our findings emphasize the importance of AFS for fostering C sequestration and reducing greenhouse gas emissions and, in particular, retaining hedgerows (legacy woodland) and their associated deadwood across temperate agroecosystems will help mitigate climate change. [ABSTRACT FROM AUTHOR]

Increased occurrence of heat wave events is an aspect of extreme climate change that may influence soil carbon (C) dynamics and greenhouse gas (GHG) emissions. However, heat wave events have rarely been studied; furthermore, their effects on C dynamics and GHG emissions in soils in agroforestry systems have not been studied. We conducted a laboratory incubation experiment to investigate the effect of simulated heat wave events and their frequencies on CO2 and N2O emissions, as well as soil labile C, in two land-use types in a common agroforestry system of western Canada. Both two- and three-time heat wave events increased CO2 and N2O emissions in both cropland and forest soils compared with the control (P < 0.01), but there was no difference between two- and three-time heat wave events. Furthermore, cumulative emissions (both CO2 and N2O emissions) increased with greater heat wave frequency, but the effect diminished with each successive heat wave event. Emissions of CO2 and N2O were higher from the forest than cropland soils during heat wave events (P < 0.01). Soil labile C (hot water extractable organic C and microbial biomass C) was higher in forest than in cropland soils (P < 0.001) and did not respond to the heat wave treatment, but showed a declining trend with an increasing heat wave frequency. Our findings suggest that heat wave events increase soil CO2 and N2O emissions in the studied soils collected from an agroforestry system and may have a positive feedback mechanism to climate change. Increased GHG emissions from both cropland and forest soils should be considered when evaluating heat wave impacts on soil C sequestration, in addition to their commonly studied effect on ecosystem productivity. [ABSTRACT FROM AUTHOR]

The temperature sensitivity (Q10) of heterotrophic soil respiration (RH) of forests affects terrestrial carbon (C) dynamics under climate change. However, the effects of changed chemistry of tree leaf litter (referred to as litter hereafter) under elevated atmospheric CO2 concentrations ([CO2]) on the Q10 of RH has not been explored. To fill the knowledge gap, the Q10 of RH was investigated through incubation experiments at three temperature levels using litters of pine (Pinus densiflora Siebold & Zucc.) and oak (Quercus variabilis Blume) that were produced under ambient ([CO2]a) and elevated ([CO2]e) [CO2]. Regardless of [CO2] conditions, pine litter had higher lignin but lower nonstructural carbohydrate (NSC), calcium (Ca), and manganese (Mn) concentrations than oak, suggesting that pine litter has inherently poor chemistry. [CO2]e increased the ratios of lignin-to-nitrogen (lignin/N; by 58 and 122% for pine and oak, respectively) and C-to-N (C/N; by 47 and 125%, respectively) of litter through decreasing litter N concentration. For soils amended with [CO2]a-litter, Q10 was greater for pine (1.54) than oak (1.39) litters in agreement with the kinetic theory on the substrate quality-Q10 relationship. However, amending [CO2]e-litter decreased Q10 for pine (1.44) but marginally increased Q10 for oak (1.44). The decreased Q10 for pine by [CO2]e could be attributed to the inherently poor litter chemistry (e.g., high lignin, and low NSC, Ca, and Mn concentrations). Our study shows that the changed litter chemistry by [CO2]e modifies Q10 of RH of litter-amended soils. [ABSTRACT FROM AUTHOR]

Root foraging enables plants to obtain more soil nutrients in a constantly changing nutrient environment. Little is known about the adaptation mechanism of adventitious roots of plants dominated by asexual reproduction (such as tea plants) to soil potassium heterogeneity. We investigated root foraging strategies for K by two tea plants (low-K tolerant genotype "1511" and low-K intolerant genotype "1601") using a multi-layer split-root system. Root exudates, root architecture and transcriptional responses to K heterogeneity were analyzed by HPLC, WinRHIZO and RNA-seq. With the higher leaf K concentrations and K biological utilization indexes, "1511" acclimated to K heterogeneity better than "1601". For "1511", maximum total root length and fine root length proportion appeared on the K-enriched side; the solubilization of soil K reached the maximum on the low-K side, which was consistent with the amount of organic acids released through root exudation. The cellulose decomposition genes that were abundant on the K-enriched side may have promoted root proliferation for "1511". This did not happen in "1601". The low-K tolerant tea genotype "1511" was better at acclimating to K heterogeneity, which was due to a smart root foraging strategy: more roots (especially fine roots) were developed in the K-enriched side; more organic acids were secreted in the low-K side to activate soil K and the root proliferation in the K-enriched side might be due to cellulose decomposition. The present research provides a practical basis for a better understanding of the adaptation strategies of clonal woody plants to soil nutrient availability. [ABSTRACT FROM AUTHOR]

Developing sustainable materials for recovering and recycling nutrients from wastewater is critically needed for nutrients such as phosphorus that have a diminishing supply. Struvite crystallization is emerging as a promising strategy for phosphorus recovery which can be enhanced with seeding through microalgal biochar. The main bottleneck of using microalgae is its high harvesting cost. In this study, an integrated electrocoagulation-flotation (ECF) process is used to recover and at the same time modify the algal surface with magnesium anode and inert carbon cathode. Harvesting efficiency of 98% was achieved with 40.78 mA cm−2, 0.5 cm inter-electrode distance and energy consumption of 4.03 kWh kg−1 in 15 min. The harvested microalgae were pyrolyzed to obtain a yield of 52.90% Mg-laden microalgal biochar. Simultaneously, surface impregnation of 28% magnesium was attained as confirmed by Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Phosphorus recovery and struvite yield of 93.70% and 2.66 g L−1, respectively, were obtained from dosing 1.50 g L−1 Mg-laden microalgal biochar. Comparison of physicochemical characteristics of residual supernatant after microalgal harvesting and struvite recovery showed that the combined use of both the residuals can serve as a sustainable growth medium for microalgae. The overall operating cost of the integrated process was found to be 2.48 USD kg−1 with a total energy consumption of 10.76 kWh kg−1, which was found to be lower than conventional harvesting unit processes such as centrifugation and filtration. This novel approach can help attaining a circular bioeconomy by encompassing nutrient recovery and waste management in an integrated process. [ABSTRACT FROM AUTHOR]

Information about regional‐level carbon (C) stocks in agroforestry systems (AFS), as well as the annual loss of agroforests and associated C stocks, is scarce, limiting our capacity for increasing C sequestration through establishing, retaining, and enhancing these systems. This study quantified regional‐level C stocks and the associated incremental economic value in the forest land‐use component of three common AFS (hedgerows, shelterbelts, and silvopastures), estimated the annual loss of hedgerow and silvopasture forests and the associated C, and assessed the potential to enhance C storage through the expansion of shelterbelts in central Alberta, Canada, using publicly available satellite imagery, previously collected field data and the Google Earth Engine platform. Results showed that forests in the three AFS stored 699.9 million tons (Mt) C across 9.5 million hectares (Mha) of land in central Alberta and were valued at $102.7 billion based on the 2021 Canadian C tax rate of $40 t−1 CO2‐equivalent. Silvopasture forests in the studied region had the highest C stocks, which were 14.2 and 67.2 times that found in hedgerow and shelterbelt forests, respectively. Between 2001 and 2020, forests in hedgerows and silvopastures declined at rates of 468.1 and 1957.1 ha year−1, respectively, leading to an 8.4 Mt decline in total C storage over the 20 years. However, there is potential to establish new shelterbelts at many road/field margins, which could increase C stocks by 2.3 times the current C stocks in shelterbelt forests. These results highlight the importance of retaining existing and establishing new AFS for increasing C sequestration, emphasizing the impact of agroforest loss on reducing C storage within agroecosystems. The development of policies that assist or reward landowners for providing the ecosystem service of C storage by retaining, establishing, and enhancing agroforests as part of existing agroecosystem management should be encouraged for mitigating climate change. [ABSTRACT FROM AUTHOR]

Efforts to reduce greenhouse gas (GHG) emissions from cattle production have led to modifications of livestock diet composition aimed at reducing CH4 emissions from enteric fermentation. These diet modifications can result in varied manure types that may differentially affect GHG emissions when applied to soil. The purpose of this experiment was to examine the effect of different manure types on GHG emissions. We conducted an incubation experiment, comparing the manure from livestock fed a corn-based diet (CM) to that from livestock fed a traditional barley-based diet (BM). The manures were applied to three soil types (with varied soil fertility and pH) and compared to a control (without manure application). Carbon dioxide (CO2) emissions were greater from CM than from BM across all soil types (29.1 and 14.7 mg CO2-C kg−1, respectively). However, CM resulted in lower N2O emissions relative to BM in the low fertility soil (4.21 and 72.67 μg N2O-N kg−1, respectively) and in lower CH4 emissions relative to BM in the two acidic soils (0.5 and 2.5 μg CH4-C kg−1, respectively). Total GHG emissions (sum of CO2, N2O, and CH4) were similar between CM and BM across all soil types, but CM (unlike BM) had 52–66% lower emissions in the low fertility soil relative to both CM and BM in the high fertility soil. Our study shows that manure and soil type interact to affect GHG emissions and that CM may mitigate N2O emissions relative to BM when applied to low fertility soils. [ABSTRACT FROM AUTHOR]

High heterogeneity in the spatial distribution of soil organic carbon (SOC) in grasslands causes uncertainty in estimating its content and storage. In this study, we investigated the spatial distribution of SOC content and storage in the prairies of southern Alberta, Canada, and how it is affected by land use such as irrigated cropping and other environmental conditions such as cattle grazing, slope landscape position and dominant plant species. The mean SOC content was determined to be 11.5 g kg–1 (range: 8.9 to 22.4 g kg–1) in the 0–10 cm layer and 6.8 g kg–1 (range: 4.0 to 13.3 g kg–1) in the 10–30 cm layer; mean SOC storage was 1.59 kg C m–2 (range: 1.23 to 2.78 kg C m–2) in the 0–10 cm layer and 2.07 kg C m–2 (range: 1.21 to 3.62 kg C m–2) in the 10–30 cm layer. The SOC content was significantly affected by slope position in both the 0–10 and 10–30 cm layers, in the following order: bottom >middle > top position. Moreover, SOC storage was higher in sites dominated by shrubs than graminoid/forb communities. Thus, SOC content and storage had distinctly clustered spatial patterns throughout the study area and were significant differences between the 0–10 and 10–30 cm soil layers. Prior land‐use change from arid grassland to irrigated cropland increased SOC content and storage in bulk soils. [ABSTRACT FROM AUTHOR]

The application of manure-derived biochar offers an alternative to avoid the direct application of manure to soil causing greenhouse gas emission. Soil fauna, especially earthworms, can markedly stimulate carbon dioxide (CO2) and nitrous oxide (N2O) emissions from soil. This study therefore investigated the effect of cattle manure biochar (added at rates of 0, 2%, or 10%, coded as BC0, BC2 and BC10, respectively) application, with or without earthworm Aporrectodea turgida, on emissions of CO2 and N2O and changes of physic-chemical properties of agricultural and forest soils in a laboratory incubation experiment. The BC10 treatment significantly enhanced cumulative CO2 emissions by 27.9% relative to the untreated control in the agricultural soil. On the contrary, the BC2 and BC10 treatments significantly reduced cumulative CO2 emissions by 16.3%–61.1% and N2O emissions by 92.9%–95.1% compared to the untreated control in the forest soil. The addition of earthworm alone significantly enhanced the cumulative CO2 and N2O fluxes in agricultural and forest soils. Cumulative CO2 and N2O fluxes were significantly increased when BC2 and BC10 were applied with earthworm in the agricultural soil, but were significantly reduced when BC10 was applied with earthworm in the forest soil. Our study demonstrated that biochar application interacted with earthworm to affect CO2 and N2O emissions, which were also dependent on the soil type involved. Our study suggests that manure biochar application rate and use of earthworm need to be carefully studied for specific soil types to maximize the climate change mitigation potential of such management practices. [ABSTRACT FROM AUTHOR]

Summary: To offer an innovative way to valorize industrial crop waste into the diverse types of biofuels, the thermochemical process of peanut waste (PW) was investigated. In particular, this study laid a great stress on the use of PW‐derived biochar as a cheap catalytic material in the production of biodiesel. Specifically, biochar derived from the pyrolysis of PW was used as a catalytic and porous medium for biodiesel production to enhance reaction kinetics and lower reaction temperature, compared to conventional methods. Two PW‐derived biochars produced at 600°C (PWB‐600) and 700°C (PWB‐700) were effective on the transesterification of soybean oil, showing higher than 95 wt% of biodiesel yield after 1 minute of transesterification reaction at ≥210°C. As a comparison, a commercially used reaction, alkali‐catalyzed transesterification, was conducted at 60°C with a KOH catalyst. Biodiesel yield from the alkali‐catalyzed reaction was less than 90 wt% even after 6 hours of reaction. Given that the biochar formation process results in the generation of pyrolytic gases and oils, both pyrolysates at different temperatures were also monitored. Pyrolytic gases included syngas and C1‐2 hydrocarbons, whereas pyrolytic oils consisted of phenolic compounds that can be used as intermediates for the synthesis of value‐added chemicals. Thus, the results confirmed that the thermochemical upgrading of PW produces value‐added industrial chemicals (pyrolytic gases and oils) and biochars that are highly active for the biodiesel production process. [ABSTRACT FROM AUTHOR]

Purpose: No-till (NT) and fertilization are common land management practices in agricultural production systems to increase soil quality and crop yield. No-till can be reversed to tillage (termed tillage reversal, TR, in this paper) due to changes in management objectives. Materials and methods: The impact of NT, TR, and TR plus nitrogen (N) fertilization (TRN) treatments on the composition and structure of bacterial communities in a Gray Luvisol was studied in west-central Alberta, Canada. Results and discussion: The structure of bacterial communities was not affected by the TR treatment (compared with NT). The TRN treatment increased the relative abundance of some bacterial taxa groups, e.g., Gemmatimonadetes, Thermoleophilia and Solibacteres, that have chemolithotrophic nitrifying functions as compared with the TR treatment. The decreased relative abundance of some bacterial taxa groups, such as Alphaproteobacteria, Deltaproteobacteria, Spartobacteria, and Planctomycetia that have denitrifying functions, would change the soil's denitrification function in the TRN as compared to the TR treatment. There were more dominant bacterial taxa groups, and the bacterial community had greater inter-annual variations in the TRN than in the NT and TR treatments. Moreover, the function of bacterial communities was affected by the TRN as compared to the NT and TR treatments, based on the predicted metagenomes. Conclusions: We conclude that when TR was applied to the soil with long-term N fertilization, which eliminates N limitation, altered soil bacterial community structure and function over TR applied to the studied Gray Luvisol without long-term N fertilization. Findings from our study have important implications for improving land management practices through tillage and N fertilization to enhance the soil's function and quality in agroecosystems. [ABSTRACT FROM AUTHOR]

The occurrence of multi‐year drought is predicted to increase globally with climate change. However, it is unclear whether drought effects on ecosystems are progressive through time.Here, we experimentally reduced growing season precipitation (GSP) by 45% at seven North American temperate grasslands for four consecutive years to determine the following: (a) whether the effects of reduced precipitation on plant community structure and biomass components (shoot, root, litter) are compounding over time; (b) whether prior year climatic and soil conditions influence subsequent drought impacts on plant community structure and biomass components; and (c) whether the effects of reduced precipitation on individual ecosystem components are related to one another.Across the seven field sites, we observed neither consistent nor progressive effects of reduced precipitation on any biomass component during the experiment, despite having extreme drought conditions imposed for four consecutive years. Relative to the ambient treatment, above‐ground net primary productivity (ANPP) declined in response to drought during the early years of the experiment but increased above the ambient treatment in the fourth year, while root and litter biomass were stable across the sites throughout the study. Similarly, graminoid cover decreased initially but recovered by the final year of the experiment, contributing to observed differences in species composition between treatments across sites. Compositional changes were not associated with any declines in species richness or evenness. Divergent responses among years were not driven by lag effects based on prior year climatic and soil conditions. Furthermore, precipitation effects on ecosystem components were largely independent as we found only two positive links: between ANPP and plant species richness, and between species evenness and composition.Synthesis. Overall, our results suggest that these northern grasslands are relatively resistant to short‐term multi‐year drought in the context of supporting plant diversity and biomass production. [ABSTRACT FROM AUTHOR]

Mixed-species plantations generally exhibit higher ecosystem multifunctionality than monospecific plantations. However, it is unclear how tree species functional composition influences species mixture effects on ecosystem multifunctionality. We selected 171 monospecific and mixed-species plantations from nine regions across subtropical China, and quantified 13 key ecosystem functional properties to investigate how species mixture effects on ecosystem multifunctionality are modulated by functional diversity and identity. We found that ecosystem multifunctionality was significantly higher (p < 0.05) in mixed tree plantations than in monospecific plantations except the mixed-conifer species plantations. Across all regions, ecosystem multifunctionality was significantly higher (p < 0.05) in mixed conifer-broadleaf plantations than in monospecific plantations of the corresponding species, but not different between mixed and monospecific coniferous plantations. The magnitude of species mixture effects on ecosystem multifunctionality varied greatly with tree species compositions. Taking Cunninghamia lanceolata Lamb. as an example, the effects varied from a range of 2.0%–9.6% when mixed with a conifer species to 36%–87% when mixed with a broadleaf species. The functional diversity was the dominate driver shaping ecosystem multifunctionality, while functional identity, as expressed by community-weighted mean of specific leaf area, also had a positive effect on ecosystem multifunctionality through the increased below-ground nitrogen and phosphorus stocks regulated by specific leaf area of the mixing tree species. Our study highlights the important role of functional diversity in shaping ecosystem multifunctionality across region-wide environmental conditions. Mixed conifer-broadleaf tree plantations with distinct functional traits benefit the enhancement of ecosystem multifunctionality, and the magnitude of species mixture effects is modulated by the functional identity of tree species composition; those relationships deserve a special consideration in multifunctional management context of subtropical plantations. [ABSTRACT FROM AUTHOR]

Soil gross nitrification (GN) is a critical process in the global nitrogen (N) cycle that results in the formation of nitrate through microbial oxidation of ammonium or organic N, and can both increase N availability to plants and nitrous oxide emissions. Soil GN is thought to be mainly controlled by soil characteristics and the climate, but a comprehensive analysis taking into account the climate, soil characteristics, including microbial characteristics, and their interactions to better understand the direct and indirect controlling factors of GN rates globally is lacking. Using a global meta-analysis based on 901 observations from 330 15N-labeled studies, we show that GN differs significantly among ecosystem types, with the highest rates found in croplands, in association with higher pH which stimulates nitrifying bacteria activities. Autotrophic and heterotrophic nitrifications contribute 63% and 37%, respectively, to global GN. Soil GN increases significantly with soil total N, microbial biomass, and soil pH, but decreases significantly with soil carbon (C) to N ratio (C:N). Structural equation modeling suggested that GN is mainly controlled by C:N and soil total N. Microbial biomass and pH are also important factors controlling GN and their effects are similar. Precipitation and temperature affect GN by altering C:N and/or soil total N. Soil total N and temperature drive heterotrophic nitrification, whereas C:N and pH drive autotrophic nitrification. Moreover, GN is positively related to nitrous oxide and carbon dioxide emissions. This synthesis suggests that changes in soil C:N, soil total N, microbial population size, and/or soil pH due to anthropogenic activities may influence GN, which will affect nitrate accumulation and gaseous emissions of soils under global climate and land-use changes. [ABSTRACT FROM AUTHOR]

Soil gross nitrogen (N) mineralization (GNM), a key microbial process in the global N cycle, is mainly controlled by climate and soil properties. This study provides for the first time a comprehensive analysis of the role of soil physicochemical properties and climate and their interactions with soil microbial biomass (MB) in controlling GNM globally. Through a meta‐analysis of 970 observations from 337 published papers from various ecosystems, we found that GNM was positively correlated with MB, total carbon, total N and precipitation, and negatively correlated with bulk density (BD) and soil pH. Our multivariate analysis and structural equation modeling revealed that GNM is driven by MB and dominantly influenced by BD and precipitation. The higher total N accelerates GNM via increasing MB. The decrease in BD stimulates GNM via increasing total N and MB, whereas higher precipitation stimulates GNM via increasing total N. Moreover, the GNM varies with ecosystem type, being greater in forests and grasslands with high total carbon and MB contents and low BD and pH compared to croplands. The highest GNM was observed in tropical wet soils that receive high precipitation, which increases the supply of soil substrate (total N) to microbes. Our findings suggest that anthropogenic activities that affect soil microbial population size, BD, soil substrate availability, or soil pH may interact with changes in precipitation regime and land use to influence GNM, which may ultimately affect ecosystem productivity and N loss to the environment. [ABSTRACT FROM AUTHOR]

A 120-day field experiment was conducted to investigate the responses of soil N2O emissions, plant biomass N content, and N cycling-related functional genes to yak (Bos grunniens) dung pat size, including full-size dung pat (FDP), 1/4FDP, 1/8FDP, and 1/16FDP (i.e., FDP split into four, eight, and sixteen equal-sized dung pat fragments) in an alpine steppe on the Qinghai-Tibetan Plateau. The yield-scaled and cumulative N2O emissions were lower in the 1/16FDP and 1/8FDP than in the FDP and 1/4FDP treatments. In addition, the 1/16FDP treatment had the smallest N2O emission factor (0.002%), possibly due to lower denitrification as shown by the lower nisS, nirK, and nosZ gene copy numbers in the first (day 30) and second (day 72) samplings, and increased aboveground plant N concentration and content, which was 23–32% and 21–36%, respectively, greater than in the other treatments. In conclusion, splitting the yak dung pat into 1/16 fragments would be an effective strategy for managing yak dung to reduce N2O emissions and improve aboveground plant biomass N content which enhances the sustainability of alpine steppe ecosystems on the Qinghai-Tibetan Plateau. The implication from this study is that long-term field experiments should be conducted to further investigate the potential antagonistic or synergistic effects of yak dung pat fragmentation combined with other amendments (e.g., nitrogen inhibitors, lime, or biochar) on reducing N2O emissions. [ABSTRACT FROM AUTHOR]

A pot experiment was carried out to study the response of Moso bamboo (Phyllostachys edulis) and broadleaf tree species (Schima superba, Cinnamomum camphora, Cyclobalanopsis glauca), representing respective native invasive and non-invasive plants in subtropical China, to N addition with three NH4+/NO3− ratios. We used 15N isotope tracing and high-throughput sequencing to study the N cycling and soil microbial communities. With an increasing NH4+/NO3− ratio, total plant biomass increased for bamboo but decreased for broadleaf trees, coinciding with the preferential assimilation of NH4+ by bamboo and NO3− by broadleaf trees, as indicated by the activities of glutamine synthetase and nitrate reductase and the enrichment of 15N in roots. The ammonia-oxidizing archaea (AOA) rather than the ammonia-oxidizing bacteria (AOB) community responded to the addition of N with different NH4+/NO3− ratios and a distinct AOA community was formed when the NH4+/NO3− ratio was greater than one. The relationship between AOA abundance and NO3− concentration was positive for C. camphora and C. glauca but negative for P. edulis. Under addition of N with a high NH4+/NO3− ratio, the AOA composition was positively related to NO3− concentration for C. camphora but negatively for P. edulis. Addition of N with a high NH4+/NO3− ratio favored biomass production but suppressed soil nitrification for bamboo in contrast to broadleaf trees. The species-specific response to soil NH4+/NO3− ratio may be an important factor that facilitates bamboo invasion into broadleaf forests. [ABSTRACT FROM AUTHOR]

A 28-day microcosm experiment was conducted using three paddy soils (an alluvial paddy soil, a loess-formed paddy soil, and a yellow clayey paddy soil) to investigate the impact of procyanidin on N2O emissions and associated microbial mechanisms. The efficacy of procyanidin on N2O emissions varied among the paddy soils tested, with an average inhibition rate ranging from 2.7% in the alluvial paddy soil to 57.1% in the loess-formed paddy soil. Furthermore, suppression of N2O emissions by procyanidin occurred alongside fluctuations in nitrate reductase activity and nirS- and nirK-type denitrifiers abundance. The correlation analysis indicates that nitrate reductase, clade I nirS-denitrifiers, clade I or II, and clade III nirK-denitrifiers were closely linked to N2O emissions. These findings provide evidence that procyanidin is capable of limiting N2O emissions in paddy soils by inhibiting nitrate reductase and different clades of nirS-/nirK-denitrifiers. [ABSTRACT FROM AUTHOR]

Global change has altered nitrogen availability in boreal forest soils. As ectomycorrhizal fungi play critical ecological functions, shifts in their abundance and community composition must be considered in the response of forests to changes in nitrogen availability. Furthermore, ectomycorrhizas are symbiotic, so the response of ectomycorrhizal fungi to nitrogen cannot be understood in isolation of their plant partners. Most previous studies, however, neglect to measure the response of host trees to nitrogen addition simultaneously with that of fungal communities. In addition to being one‐sided, most of these studies have also been conducted in coniferous forests. Deciduous and "dual‐mycorrhizal" tree species, namely those that form ecto‐ and arbuscular mycorrhizas, have received little attention despite being widespread in the boreal forest. We applied nitrogen (30 kg ha−1 year−1) for 13 years to stands dominated by aspen (Populus tremuloides Michx.) and hypothesized that tree stem radial growth would increase, ectomycorrhizal fungal biomass would decrease, ectomycorrhizal fungal community composition would shift, and the abundance of arbuscular mycorrhizal (AM) fungi would increase. Nitrogen addition initially increased stem radial growth of aspen, but it was not sustained at the time we characterized their mycorrhizas. After 13 years, the abundance of fungi possessing extramatrical hyphae, or "high‐biomass" ectomycorrhizas, doubled. No changes occurred in ectomycorrhizal and AM fungal community composition, or in ecto‐ and AM abundance measured as root colonization. This dual‐mycorrhizal tree species did not shift away from ectomycorrhizal fungal dominance with long‐term nitrogen input. The unexpected increase in high‐biomass ectomycorrhizal fungi with nitrogen addition may be due to increased carbon allocation to their fungal partners by growth‐limited trees. Given the focus on conifers in past studies, reconciling results of plant–mycorrhizal fungal relationships in stands of deciduous trees may demand a broader view on the impacts of nitrogen addition on the structure and function of boreal forests. [ABSTRACT FROM AUTHOR]