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In drylands, where water scarcity limits vascular plant growth, much of the primary production occurs at the soil surface. This is where complex macro‐ and microbial communities, in an intricate bond with soil particles, form biological soil crusts (biocrusts). Despite their critical role in regulating C and N cycling in dryland ecosystems, there is limited understanding of the fate of biologically fixed C and N from biocrusts into the mineral soil, or how climate change will affect C and N fluxes between the atmosphere, biocrusts, and subsurface soils. To address these gaps, we subjected biocrust–soil systems to experimental warming and drought under controlled laboratory conditions, monitored CO2 fluxes, and applied dual isotopic labeling pulses (13CO2 and 15N2). This allowed detailed quantification of elemental pathways into specific organic matter (OM) pools and microbial biomass via density fractionation and phospholipid fatty acid analyses. While biocrusts modulated CO2 fluxes regardless of the temperature regime, drought severely limited their photosynthetic C uptake to the extent that the systems no longer sustained net C uptake. Furthermore, the effect of biocrusts extended into the underlying 1 cm of mineral soil, where C and N accumulated as mineral‐associated OM (MAOM<63μm). This was strongly associated with increased relative dominance of fungi, suggesting that fungal hyphae facilitate the downward C and N translocation and subsequent MAOM formation. Most strikingly, however, these pathways were disrupted in systems exposed to warming, where no effects of biocrusts on the elemental composition of the underlying soil nor on MAOM were determined. This was further associated with reduced net biological N fixation under combined warming and drought, highlighting how changing climatic conditions diminish some of the most fundamental ecosystem functions of biocrusts, with detrimental repercussions for C and N cycling and the persistence of soil organic matter pools in dryland ecosystems. [ABSTRACT FROM AUTHOR]

A review of the available literature shows that analyses of organic Rankine cycle systems with a zeotropic mixture working medium practically concern single-circuit systems. In these works, it has been shown that the standing of zeotropic mixtures in organic Rankine cycle systems makes it possible to achieve higher power and efficiency compared to organic Rankine cycle systems with pure fluids. In this article, the authors present an analysis of the efficiency of a two-circuit organic Rankine cycle (binary) power plant with a zeotropic mixture in the upper cycle of this power plant. The proposed binary power plant system uses a zeotropic mixture circulating medium in the upper organic Rankine cycle circuit, while the lower circuit uses a homogeneous low-boiling medium. The results of this analysis showed that with properly selected parameters of the binary power plant system, i.e. with appropriate selection of the pressure during the evaporation transformation in the upper and lower circuits, the power obtained in it is higher than for a single-circuit power plant in the same temperature range (for the same heat source and the same condensing temperature). The increase in the power of the binary power plant system was achieved by using the heat contained in the water stream to preheat the medium in the bottom circuit. For example, for the binary organic Rankine cycle power plant with R413A refrigerant in the upper circuit, the generated power is 17.8 kWe, which is 20% higher than for a single-circuit power plant (for the reference power plant, the power is 14.8 kWe). [ABSTRACT FROM AUTHOR]

Introduction: Sugarcane/soybean intercropping with reduced nitrogen (N) addition has improved soil fertility and sustainable agricultural development in China. However, the effects of intercropping pattern and N fertilizer addition on the allocation of photosynthesized carbon (C) in plant-soil system were far less understood. Methods: In this study, we performed an 13CO2 pulse labeling experiment to trace C footprints in plant-soil system under different cropping patterns [sugarcane monoculture (MS), sugarcane/soybean intercropping (SB)] and N addition levels [reduced N addition (N1) and conventional N addition (N2)]. Results and discussion: Our results showed that compared to sugarcane monoculture, sugarcane/soybean intercropping with N reduced addition increased sugarcane biomass and root/shoot ratio, which in turn led to 23.48% increase in total root biomass. The higher root biomass facilitated the flow of shoot fixed 13C to the soil in the formof rhizodeposits. More than 40% of the retained 13C in the soil was incorporated into the labile C pool [microbial biomass C (MBC) and dissolved organic C (DOC)] on day 1 after labeling. On day 27 after labeling, sugarcane/soybean intercropping withN reduced addition showed the highest 13C content in the MBC as well as in the soil, 1.89 and 1.14 times higher than the sugarcane monoculture, respectively. Moreover, intercropping pattern increased the content of labile C and labile N (alkaline N, ammonium N and nitrate N) in the soil. The structural equation model indicated that the cropping pattern regulated 13C sequestration in the soil mainly by driving changes in labile C, labile N content and root biomass in the soil. Our findings demonstrate that sugarcane/soybean intercropping with reduced N addition increases photosynthesized C sequestration in the soil, enhances the C sink capacity of agroecosystems. [ABSTRACT FROM AUTHOR]

Soil moisture is among the most important factors regulating soil biodiversity and functioning. Models forecast changes in the precipitation regime in many areas of the planet, but how these changes will influence soil functioning, and how biotic drivers modulate such effects, is far from being understood. We evaluated the responses of C and N fluxes, and soil microbial properties to different soil water regimes in soils from the main three ecotypes of the world's largest and most diverse tropical savanna. Further, we explored the direct and indirect effects of changes in the ecotype and soil water regimes on these key soil processes. Soils from the woodland savanna showed a better nutritional status than the other ecotypes, as well as higher potential N cycling rates, N2O emissions, and soil bacterial abundance but lower bacterial richness, whereas potential CO2 emissions and CH4 uptake peaked in the intermediate savanna. The ecotype also modulated the effects of changes in the soil water regime on nutrient cycling, greenhouse gas fluxes, and soil bacterial properties, with more intense responses in the intermediate savanna. Further, we highlight the existence of multiple contrasting direct and indirect (via soil microbes and abiotic properties) effects of an intensification of the precipitation regime on soil C- and N-related processes. Our results confirm that ecotype is a fundamental driver of soil properties and functioning in the Cerrado and that it can determine the responses of key soil processes to changes in the soil water regime. [ABSTRACT FROM AUTHOR]

Alpine dwarf pine populations are dwelling in a climate-sensitive habitat, where detection of the carbon (C) cycle is still valued for sustainability. Foliar and soil parameters are key factors that combine to jointly affect aboveground C storage in alpine ecosystems, but how they generate combined contributions to aboveground C in alp dwellers still needs more research. In this study, Pinus pumila, a typical alp dwarf pine species in a canyon of the Great Khingan Mountain, was focused on. Their natural populations were investigated for individual growth and needle and soil parameters in plots across six categorized elevations from 800 m to 1200 m. Aboveground C storage was estimated by three allometric models which were all found to increase against increases in elevation. Along the increasing elevational gradient, needle concentrations of nitrogen (N) and phosphorus (P) both showed decreasing trends, but activities of N and P assimilation enzymes and chlorophyl contents, as well as the soil contents of ammonium N and organic matter, all showed increasing trends. Multiple linear regression models indicated that elevation (parameter estimate, PE: +0.01), needle P (PE: +0.66) and chlorophyl contents (PE: +0.60) made jointly positive contributions to estimated C storage while soil pH had a negative contribution (PE: −1.80). For the purpose of sustainable C fixation by alp P. pumila populations, strategies should be considered to increase P availability and control high soil pH. Our results fill the gap about C storage and driving forces in alpine ecosystems, and their applications are not limited to being referenced by other alpine plants. [ABSTRACT FROM AUTHOR]

Plant rhizodeposition strongly mediates plant-soil-microbe interactions and impacts the soil active organic carbon (C) pool. However, the mechanisms by which rhizodeposition affects the modulation of soil active organic C pool remain poorly understood. In this study, we investigated the effects of rhizodeposition on active organic C pool and microbial communities in Moso bamboo (Phyllostachys edulis), a clonal plant with rhizome-connected mother and offspring ramets. The crown of the mother ramet was enriched with 13CO 2 to trace rhizodeposition and assess changes in soil organic C pool and the microbial community across different root systems (culm roots and rhizome roots) during key growth stages (early, peak, branching, and leafing). Our results showed that crown CO 2 enrichment increased δ13C and the contents of microbial biomass C, dissolved organic C, and labile organic C (by 22.08 % to 43.67 %) in the rhizosphere, which significantly altered the bacterial community composition. Under crown CO 2 enrichment, the abundance of bacterial taxa and genes associated with recalcitrant C decomposition decreased by 29.08 %–77.38 % and 30.75 %–56.85 %, respectively; while taxa and genes related to CO 2 fixation increased by 51.22 %–267.00 % and 92.52 %–331.46 %, respectively. These microbial shifts contributed to an increase in the soil active organic C pool. In addition, the growth stage, rather than the root system, had a greater influence on rhizodeposition, with higher δ13C observed during the early and leafing stages compared to the peak and branching stages. In conclusion, our findings suggest that increases in the active organic C pool were primarily driven by enhanced C rhizodeposition, the stimulation of microbes involved in CO 2 fixation, and the suppression of bacteria involved in recalcitrant C decomposition, while being highly dependent on the growth stage. This study provides valuable insights into the interactions between plant rhizodeposition, microbial functions, and soil active organic C dynamics. [Display omitted] • Rhizodeposition differed among four growth stages of Moso bamboo. • δ13C and active organic C fractions showed no difference between various root systems. • Enhanced rhizodeposition, CO 2 fixation and reduced C degradation changed soil C pool. • Thermoplasmatota matters most for variations in active organic C components. [ABSTRACT FROM AUTHOR]

Cover cropping is an effective method to protect agricultural soils from erosion, promote nutrient and moisture retention, encourage beneficial microbial activity, and maintain soil structure. Re-utilization of winter cover crop root channels by maize roots during summer allows the cash crop to extract resources from distal regions in the soil horizon. In this study, we investigated how cover cropping during winter followed by maize ( Zea mays L.) during summer affects the spatiotemporal composition and function of the bacterial communities in the maize rhizosphere and surrounding soil samples using quantitative polymerase chain reaction (PCR), 16S ribosomal ribonucleic acid (rRNA) gene amplicon sequencing, and metaproteomics. We found that the bacterial community differed significantly among cover crop species, soil depths, and maize growth stages. Bacterial abundance increased in reused root channels, and it continued to increase as cover crop diversity changed from monocultures to mixtures. Mixing Fabaceae with Brassicaceae or Poaceae enhanced the overall contributions of several steps of the bacterial carbon and nitrogen cycles, especially glycolysis and the pentose phosphate pathway. The deeper root channels of Fabaceae and Brassicaceae as compared to Poaceae corresponded to higher bacterial 16S rRNA gene copy numbers and improved community presence in the subsoil regimes, likely due to the increased availability of root exudates secreted by maize roots. In conclusion, root channel reuse improved the expression of metabolic pathways of the carbon and nitrogen cycles and the bacterial communities, which is beneficial to the soil and to the growing crops., Competing Interests: The authors declare that they have no conflict of interests that could have influenced the work being reported in this manuscript., (© The Author(s) 2024. Published by Oxford University Press on behalf of the International Society for Microbial Ecology.)

Areas covered by seminatural grasslands have been in constant decline for decades in Europe. This trend is particularly strong for mountain territories, where such traditional agricultural practices as cattle grazing are no longer economically feasible. This study was conducted in the subalpine pasture of Cinte Tesino (TN, Italy), where local farmers have applied the following different management strategies: shorter and longer grazing durations during the season and a complete abandonment for the last 15 years. We aimed to study how these different management strategies impact the functioning and diversity of vegetation and the chemical and biological characteristics of the soil. Species richness was higher in plots subjected to longer grazing with a prevalence of D. caespitosa in terms of biomass share. A decline in species richness in abandoned plots was accompanied by an increase in the share of other graminoids in collected biomass. A concomitant increase in leaf N concentration and light availability in grazed plots resulted in higher photosynthetic efficiency in some species, as revealed by the δ13C of plant tissues. Soils under grazing were characterised by a higher concentration of total and extractable N, almost doubled microbial biomass C and increased extracellular enzymes activity, evidencing nutrient cycling mobilization. While the microbial pool was characterised by lower mineralization rates, C was lost from the soil with 15 years of abandonment. The longer grazing season demonstrated to be the most beneficial, promoting species richness, C accumulation and better soil microbial functioning. A change in soil pH from strongly acidic to moderately acidic with longer grazing is likely one of the important factors adding to the success in the functioning of primary producers and decomposers in this site. [ABSTRACT FROM AUTHOR]

Abstract Background Qatar is one of the countries with the highest carbon (C) footprints per capita in the world with an increasing population and food demand. Furthermore, the international blockade by some countries that is affecting Qatar—which has been traditionally a highly-dependent country on food imports—since 2017 has led the authorities to take the decision of increasing food self-sufficiency. In this study we have assessed the effect on greenhouse gas (GHG) emissions of shifting diets from conventional to organic products and from import-based diets to more regionalized diets for the first time in a Gulf country. Results We found that considering the production system, the majority of the emissions come from the animal products, but the differences between conventional and organic diets are very small (738 and 722 kg CO2-eq capita−1 year−1, of total emissions, respectively). Conversely, total emissions from plant-based products consumption might be around one order of magnitude smaller, but the differences in the emissions between the organic and conventional systems were higher than those estimated for animal products, leading to a decrease in 44 kg CO2-eq capita−1 year−1 when changing from 100% conventional to 50% of organic consumption of plant-based products. Regarding the shift to regionalized diets, we found that packaging has a small influence on the total amount of GHG emissions, whereas emissions from transportation would be reduced in around 450 kg CO2 capita−1 year−1 when reducing imports from 100 to 50%. Conclusions However, these results must be read carefully. Due to the extreme adverse pedoclimatic conditions of the country, commercial organic regional livestock would not be possible without emitting very high GHG emissions and just only some traditional livestock species may be farmed in a climate-friendly way. On the other hand, organic and regional low-CO2 emission systems of plant-based products would be possible by implementing innovations in irrigation or other innovations whose GHG emissions must be further studied in the future. Therefore, we conclude that shifting towards more plant-based organic regional consumption by using climate-friendly irrigation is a suitable solution to both increasing self-sufficiency and reducing C footprint. We encourage national authorities to including these outcomes into their environmental and food security policies.

Soil microorganisms determine the fate of soil organic matter (SOM), and their activities compose a major component of the global carbon (C) cycle. We employed a multisubstrate, DNA-stable isotope probing experiment to track bacterial assimilation of C derived from distinct sources that varied in bioavailability. This approach allowed us to measure microbial contributions to SOM processing by measuring the C assimilation dynamics of diverse microorganisms as they interacted within soil. We identified and tracked 1,286 bacterial taxa that assimilated 13C in an agricultural soil over a period of 48 d. Overall 13C-assimilation dynamics of bacterial taxa, defined by the source and timing of the 13C they assimilated, exhibited low phylogenetic conservation. We identified bacterial guilds composed of taxa that had similar 13C assimilation dynamics. We show that C-source bioavailability explained significant variation in both C mineralization dynamics and guild structure, and that the growth dynamics of bacterial guilds differed significantly in response to C addition. We also demonstrate that the guild structure explains significant variation in the biogeographical distribution of bacteria at continental and global scales. These results suggest that an understanding of in situ growth dynamics is essential for understanding microbial contributions to soil C cycling. We interpret these findings in the context of bacterial life history strategies and their relationship to terrestrial C cycling. [ABSTRACT FROM AUTHOR]

Areas covered by seminatural grasslands have been in constant decline for decades in Europe. This trend is particularly strong for mountain territories, where such traditional agricultural practices as cattle grazing are no longer economically feasible. This study was conducted in the subalpine pasture of Cinte Tesino (TN, Italy), where local farmers have applied the following different management strategies: shorter and longer grazing durations during the season and a complete abandonment for the last 15 years. We aimed to study how these different management strategies impact the functioning and diversity of vegetation and the chemical and biological characteristics of the soil. Species richness was higher in plots subjected to longer grazing with a prevalence of D. caespitosa in terms of biomass share. A decline in species richness in abandoned plots was accompanied by an increase in the share of other graminoids in collected biomass. A concomitant increase in leaf N concentration and light availability in grazed plots resulted in higher photosynthetic efficiency in some species, as revealed by the δ13C of plant tissues. Soils under grazing were characterised by a higher concentration of total and extractable N, almost doubled microbial biomass C and increased extracellular enzymes activity, evidencing nutrient cycling mobilization. While the microbial pool was characterised by lower mineralization rates, C was lost from the soil with 15 years of abandonment. The longer grazing season demonstrated to be the most beneficial, promoting species richness, C accumulation and better soil microbial functioning. A change in soil pH from strongly acidic to moderately acidic with longer grazing is likely one of the important factors adding to the success in the functioning of primary producers and decomposers in this site.

After carbon (C) enters a lake through surface runoff and atmospheric deposition, most of it, being influenced by the environmental conditions of the basin, is deposited into lake sediment, thus, becoming one of the most important C pools in the world. Therefore, it is critical to understand sediment response characteristics under the context of increasing C concentrations in lake water. Based on the changes of sediment C concentration at different depths in Poyang Lake, belonging to China's large floodplain-lake system, we revealed the sediment C short-term response characteristics to changes in lake water C concentrations as well as their associated impacting factors. We found that dissolved total carbon (DTC) concentrations increased by 25.78% in winter compared to spring, while total carbon (TC) sediment concentrations increased by only 4.37% during the corresponding period. Specifically, we found that there was a hysteresis effect in the response of sediment C to the increase of water C concentration in the short term. When DTC concentrations in water were below a threshold value (12.50 mg/L), sediment TC concentrations were generally maintained at approximately 5.79 mg/kg. We also believed that biological and environmental factors and sediment stratification characteristics collectively resulted in this sediment C hysteresis effect. Among these factors and characteristics, phytoplankton can affect sediment C response by changing C absorption and utilization in water or cause a synergistic effect along with environmental factors, which is the key link that causes this C sediment hysteresis effect to occur. Furthermore, we found that the combined effect of sediment C from different depths also resulted in a hysteresis effect in C deposition. [ABSTRACT FROM AUTHOR]

Background: Qatar is one of the countries with the highest carbon (C) footprints per capita in the world with an increasing population and food demand. Furthermore, the international blockade by some countries that is affecting Qatar—which has been traditionally a highly-dependent country on food imports—since 2017 has led the authorities to take the decision of increasing food self-sufficiency. In this study we have assessed the effect on greenhouse gas (GHG) emissions of shifting diets from conventional to organic products and from import-based diets to more regionalized diets for the first time in a Gulf country. Results: We found that considering the production system, the majority of the emissions come from the animal products, but the differences between conventional and organic diets are very small (738 and 722 kg CO2-eq capita−1 year−1, of total emissions, respectively). Conversely, total emissions from plant-based products consumption might be around one order of magnitude smaller, but the differences in the emissions between the organic and conventional systems were higher than those estimated for animal products, leading to a decrease in 44 kg CO2-eq capita−1 year−1 when changing from 100% conventional to 50% of organic consumption of plant-based products. Regarding the shift to regionalized diets, we found that packaging has a small influence on the total amount of GHG emissions, whereas emissions from transportation would be reduced in around 450 kg CO2 capita−1 year−1 when reducing imports from 100 to 50%. Conclusions: However, these results must be read carefully. Due to the extreme adverse pedoclimatic conditions of the country, commercial organic regional livestock would not be possible without emitting very high GHG emissions and just only some traditional livestock species may be farmed in a climate-friendly way. On the other hand, organic and regional low-CO2 emission systems of plant-based products would be possible by implementing innovations in irrigation or other innovations whose GHG emissions must be further studied in the future. Therefore, we conclude that shifting towards more plant-based organic regional consumption by using climate-friendly irrigation is a suitable solution to both increasing self-sufficiency and reducing C footprint. We encourage national authorities to including these outcomes into their environmental and food security policies. [ABSTRACT FROM AUTHOR]

From a molecular level to an ecosystem scale, different coupling mechanisms take place during coupled carbon-nitrogen-water (C-N-H2O) cycles, of which essential are water flux and related biogeochemical processes through physicochemical reactions associated with terrestrial and aquatic ecosystems. Meanwhile, regional coupled C-N-H2O cycle will subsequently impact regional gross primary productivity (GPP) and C and N exchanges during air-water interactions that occur downstream of watersheds. This study aimed to first synthetically analyze the regional dynamics of C, N and H2O cycles in ecosystems and determine their interactional relationships; second, to specify regional C-N-H2O coupled relationships of ecosystems and their theoretical ecological principles; third, to classify coupled regional response and adaptation of the C-N-H2O cycle to climatic and environmental changes under anthropogenic activities, providing a theoretical basis to fully understand and make adjustments to interactional C, N and H2O cycling relationships at different ecosystem scales and under associated coupling processes. [ABSTRACT FROM AUTHOR]

In submarine-hydrothermal systems, fluid-rock interactions play a pivotal role in fostering life on rocky planets. Carbonated-ultramafic rocks (i.e., ophicarbonates) represent an important witness of such environments and their study may provide new insights into hydrothermal processes. Here, we report in-situ trace element concentrations and the first in-situ boron isotope analyses (δ11B) of serpentines from the Ligurian N. Apennine (Italy) ophicarbonates, which represent non-subducted remnants of Jurassic ultramafic-hosted hydrothermal system. Based on micro-Raman analyses, lizardite is the dominant stable serpentine polymorph in the studied samples, thus constraining the temperature (T) of serpentinization below ca. 320 °C. By means of U Pb LA-ICP-MS calcite geochronology, the age of the carbonation event is constrained at 137 ± 3 Ma (2σ, n = 52). The increasing inventory of several fluid-mobile elements (e.g., B, Li, As, Sb, Sr, U) associated with the REE budget variability in serpentines from ophicarbonates compared to those in pure serpentinites suggest that physico-chemical changes during the evolution of the hydrothermal system exert a relevant influence on the geochemistry of serpentines. Pure serpentinites, which are considered the protoliths of the ophicarbonates, show positive δ11B signatures from +15.8 to +35.0‰ (n = 24), thus falling in the range of present-day oceanic and forearc serpentinites and ophiolite-derived serpentinites. The δ11B imprint of serpentines in ophicarbonates clusters at +10.2 ± 2.2‰ (2SD, n = 57) and − 5.7 ± 1.5‰ (2SD, n = 36). Remarkably, this is the first report of oceanic serpentines showing negative B isotope compositions. The positive δ11B data likely reflect inheritance from the precursor serpentinite, while the negative δ11B values are here related to the hydrothermal process(es). We attempt to model how the variation in pH and different δ11B composition of the hydrothermal vent fluids (+25 and + 8‰) at different T (100 and 150 °C) can affect the δ11B imprint of serpentines. Our results indicate that either pH condition or δ11B of the hydrothermal vent fluids can shift the δ11B of serpentines from positive to negative values. Our new trace element and δ11B data are integrated and discussed with those from the literature to achieve new constraints in the variations and controls on the physical-chemical conditions of fluid-rock interaction during the progressive evolution of long-lived fossil ultramafic-hosted hydrothermal system. Finally, we discuss how subduction processes can potentially modify the B geochemistry of ophicarbonates and the information that we could achieve by studying B isotopes in such high- P lithologies to unravel the B- and C-cycles into the Earth's mantle since the onset of modern plate tectonics. • New In-situ δ11B data for serpentine in ophicarbonates from the N. Apennines (Italy). • First report of oceanic serpentines with negative δ11B signatures. • Hydrothermal vent fluids can modify the δ11B imprint of serpentine. • U Pb calcite geochronology constrains carbonation at 137 ± 3 Ma in N. Apennine. • Subduction of ophicarbonates may provide heterogeneous δ11B at depth. [ABSTRACT FROM AUTHOR]

Understanding the functioning of different forest ecosystems is important due to their key role in strategies for climate change mitigation, especially through soil C sequestration. In controlled laboratory conditions, we conducted a preliminary study on six different forest soils (two coniferous, two deciduous, and two mixed sites comprising trees of different ages) collected from the same region. The aim was to explore any differences and assess seasonal changes in soil microbial parameters (basal respiration BR, microbial biomass Cmic, metabolic quotient qCO2, dehydrogenase activity DHA, and Cmic:Corg ratio). Indicator- and forest-specific seasonality was assessed. In addition to litter input, soil parameters (pH, nutrient content, texture and moisture) strongly regulated the analyzed microbial indicators. PCA analysis indicated similarity between mature mixed and deciduous forests. Among annual mean values, high Cmic and DHA with simultaneously low qCO2 suggest that the mature deciduous stand was the most sustainable in microbial activities among the investigated forest soils. Research on the interrelationship between soil parameters and forest types with different tree ages needs to be continued and extended to analyze a greater number of forest and soil types.

Abstract Soil organic matter (SOM) protection, stability and long-term accumulation are controlled by several factors, including sorption onto mineral surfaces. Iron (Fe) has been suggested as a key regulator of SOM stability, both in acidic conditions, where Fe(III) is soluble, and in near-neutral pH environments, where it precipitates as Fe(III) (hydr)oxides. The present study aimed to probe, by sorption/desorption experiments in which Fe was added to the system, the mechanisms controlling Fe(III)-mediated organic carbon (C) stabilization; fine silt and clay (FSi + Cl) and fine sand (FSa) SOM fractions of three soils under different land uses were tested. Fe(III) addition caused a decrease in the organic C remaining in solution after reaction, indicating an Fe-mediated organic C stabilization effect. This effect was two times larger for FSa than for FSi + Cl, the former fraction being characterized by both low specific surface area and high organic C content. The organic C retained in the solid phase after Fe-mediated stabilization has relatively low sensitivity to desorption. Moreover, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy indicated that Fe-mediated organic C stabilization can be mainly ascribed to the formation of complexes between carbohydrate OH functional groups and Fe oxides. These results demonstrate that the binding of labile SOM compounds to Fe(III) contributes to its preservation, and that the mechanisms involved (flocculation vs. coating) depend on the size fractions. Graphical abstract Unlabelled Image Highlights • Fe(III) controls organic C stabilization in fine silt and clay and fine sand SOM fractions. • Fe(III) addition caused a decrease in the organic C in the solution. • The stabilization effect was larger for the fine sand SOM fraction. • The reaction with Fe(III) may promote either flocculation or coating phenomena. • The organic C retained after Fe-mediated stabilization has low sensitivity to desorption. [ABSTRACT FROM AUTHOR]

Grazing causes changes in microbiome metabolic pathways affecting plant growth and soil physicochemical properties. However, how grazing intensity affects microbial processes is poorly understood. In semiarid steppe grassland in northern China, shotgun metagenome sequencing was used to investigate variations in soil carbon (C) and nitrogen (N) cycling-related genes after six years of the following grazing intensities: G0, control, no grazing; G1, 170 sheep days ha−1 year−1; G2, 340 sheep days ha−1 year−1; and G3, 510 sheep days ha−1 year−1. Taxa and functions of the soil microbiome associated with the C cycle decreased with increasing grazing intensity. Abundances of genes involved in C fixation and organic matter decomposition were altered in grazed sites, which could effects on vegetation decomposition and soil dissolved organic carbon (DOC) content. Compared with the control, the abundances of nitrification genes were higher in G1, but the abundances of N reduction and denitrification genes were lower, suggesting that light grazing promoted nitrification, inhibited denitrification, and increased soil NO 3 − content. Q-PCR further revealed that the copies of genes responsible for carbon fixation (cbbL) and denitrification (norB) decreased with increasing grazing intensity. The highest copy numbers of the nitrification genes AOA and AOB were in G1, whereas copy numbers of the denitrification gene nirK were the lowest. A multivariate regression tree indicated that changes in C fixation genes were linked to changes in soil DOC content, whereas soil NO 3 − content was linked with nitrification and denitrification under grazing. Thus, genes associated with C fixation and the N cycle affected how C fixation and N storage influenced soil physicochemical properties under grazing. The findings indicate that grazing intensity affected C and N metabolism. Proper grassland management regimes (e.g., G1) are beneficial to the balances between ecological protection of grasslands and plant production in the semiarid steppe. • Grazing intensity affected soil microbial carbon (C) and nitrogen (N) metabolism. • Grazing affected C cycling by increasing C fixation and decreasing C decomposition. • Dissolved organic C was the predominant driver of changes in soil C fixation. • Changes in soil nitrate content under grazing impacted the N cycle. [ABSTRACT FROM AUTHOR]

Australian ecosystems, particularly wetlands, are facing new and extreme threats due to climate change, land use, and other human interventions. However, more fundamental knowledge is required to understand how nutrient turnover in wetlands is affected. In this study, we deployed a mechanistic biogeochemical model of carbon (C), nitrogen (N), and sulfur (S) cycles at 0.25∘× 0.25∘ spatial resolution across wetlands in Australia. Our modeling was used to assess nutrient inputs to soil, elemental nutrient fluxes across the soil organic and mineral pools, and greenhouse gas (GHG) emissions in different climatic areas. In the decade 2008–2017, we estimated an average annual emission of 5.12 Tg-CH4, 90.89 Tg-CO2, and 2.34 × 10−2 Tg-N2O. Temperate wetlands in Australia have three times more N2O emissions than tropical wetlands as a result of fertilization, despite similar total area extension. Tasmania wetlands have the highest areal GHG emission rates. C fluxes in soil depend strongly on hydroclimatic factors; they are mainly controlled by anaerobic respiration in temperate and tropical regions and by aerobic respiration in arid regions. In contrast, N and S fluxes are mostly governed by plant uptake regardless of the region and season. The new knowledge from this study may help design conservation and adaptation plans to climate change and better protect the Australian wetland ecosystem.

Introduction: Sugarcane/soybean intercropping with reduced nitrogen (N) addition has improved soil fertility and sustainable agricultural development in China. However, the effects of intercropping pattern and N fertilizer addition on the allocation of photosynthesized carbon (C) in plant-soil system were far less understood., Methods: In this study, we performed an 13 CO 2 pulse labeling experiment to trace C footprints in plant-soil system under different cropping patterns [sugarcane monoculture (MS), sugarcane/soybean intercropping (SB)] and N addition levels [reduced N addition (N1) and conventional N addition (N2)]., Results and Discussion: Our results showed that compared to sugarcane monoculture, sugarcane/soybean intercropping with N reduced addition increased sugarcane biomass and root/shoot ratio, which in turn led to 23.48% increase in total root biomass. The higher root biomass facilitated the flow of shoot fixed 13 C to the soil in the form of rhizodeposits. More than 40% of the retained 13 C in the soil was incorporated into the labile C pool [microbial biomass C (MBC) and dissolved organic C (DOC)] on day 1 after labeling. On day 27 after labeling, sugarcane/soybean intercropping with N reduced addition showed the highest 13 C content in the MBC as well as in the soil, 1.89 and 1.14 times higher than the sugarcane monoculture, respectively. Moreover, intercropping pattern increased the content of labile C and labile N (alkaline N, ammonium N and nitrate N) in the soil. The structural equation model indicated that the cropping pattern regulated 13 C sequestration in the soil mainly by driving changes in labile C, labile N content and root biomass in the soil. Our findings demonstrate that sugarcane/soybean intercropping with reduced N addition increases photosynthesized C sequestration in the soil, enhances the C sink capacity of agroecosystems., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Zhang, Tang, Peng, Ge, Liu, Feng and Wang.)

In this study, 11 dehydrodiferulic acids (DFAs) and 8 diethyl dehydrodiferulates (DEFs) were synthesized and evaluated by Trolox equivalent antioxidant capacity (TEAC) and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) assays for their antioxidant properties to understand the Structure-Antioxidant Activity Relationship (SAR) of these dehydrodiferulates. In both assays, the order of antioxidant activity for all tested ferulic acid dimers were consistent except for 3-(4-Hydroxy-3-methoxy-benzylidene)-5-(4-hydroxy-3-methoxy-phenyl)-3H-furan-2-one ( 2 , 8-8-lactone DC DFA, not occurred naturally) being the best antioxidant by TEAC test. The order of antioxidant activity of diferulic acid ethyl esters, evaluated by both assays, was not consistent; however, TEAC and DPPH assays provided consistent results for certain set of ethyl diferulates. In this study most of dimeric ferulates, with three exceptions, showed higher radical-scavenging efficacy than the monomers. Comparing the antioxidant activities of the tested diferulates suggested that the phenolic hydroxyl group, electron donating methoxyl group, and stable conjugated transient structures dictate the antioxidant activity of diferulates. [ABSTRACT FROM AUTHOR]

Abstract The humification process is one of the least understood and most intriguing aspects of humus chemistry and vital to the global carbon (C) cycle. Peatlands represent the largest terrestrial reservoirs of organic C and support a unique biodiversity, but are also natural archives of climate and environmental changes. In fact, cores from ombrotrophic peatlands are commonly used to reconstruct environmental impacts by human activities during the past decades, centuries and millennia. Understanding the extent to which bogs may serve as reliable archives is of paramount importance in order to ensure that chronological information about natural and human-induced environmental changes are effectively preserved in peat deposits rather than irretrievably affected by humification. Structural changes of the organic matter which constitutes peat are often evaluated by various indirect measures of the degree of humification. Numerous methods and proxies have been proposed and used during the last century, often providing contrasting or inconsistent results. Here, we tested multiple physical, chemical, spectroscopic and thermal approaches using peat samples collected from nine bogs on four continents. Despite the different climatic conditions, botanical composition, depth and age of peat formation, we show that the H/C ratio is the simplest, most widely valid and cost-effective humification proxy and should find universal application to multi-proxy geochemical and paleoenvironmental studies. Moreover, we show that, on average, three-quarters of the organic C in the studied bogs is in a comparatively undecomposed state, and thus vulnerable to climate changes. [ABSTRACT FROM AUTHOR]

Vascular endothelial growth factor (VEGF) has emerged as a therapeutic target in several malignancies, including cervical cancer. Chemotherapy doublets combined with the fully humanized monoclonal antibody, bevacizumab, now constitute first-line therapy for women struggling with recurrent/metastatic cervical carcinoma. Regulatory approval for this indication was based on the phase III randomized trial, GOG 240, which demonstrated a statistically significant and clinically meaningful improvement in overall survival when bevacizumab was added to chemotherapy: 17.0 vs 13.3 months; HR 0.71; 98% CI, 0.54–0.95; p = .004. Incorporation of bevacizumab resulted in significant improvements in progression-free survival and response. These benefits were not accompanied by deterioration in quality of life. GOG 240 identified vaginal fistula as a new adverse event associated with bevacizumab use. All fistulas occurred in women who had received prior pelvic radiotherapy, and none resulted in emergency surgery, sepsis, or death. Final protocol-specified analysis demonstrated continued separation of the survival curves favoring VEGF inhibition: 16.8 vs 13.3 months; HR 0.77; 95% CI, 0.62–9.95; p = .007. Post-progression survival was not significantly different between the arms in GOG 240. Moving forward, immunotherapy has now entered the clinical trial arena to address the high unmet clinical need for effective and tolerable second line therapies in this patient population. Targeting the programmed cell death 1/programmed death ligand 1 (PD-1/PD-L1) pathway using checkpoint inhibitors to break immunologic tolerance is promising. The immunologic landscape involving human papillomavirus-positive head and neck carcinoma and cutaneous squamous cell carcinoma can be informative when considering feasibility of checkpoint blockade in advanced cervical cancer. Phase II studies using anti-PD-1 molecules, nivolumab and pembrolizumab are ongoing, and GOG 3016, the first phase III randomized trial of a checkpoint inhibitor (cemiplimab) in cervical cancer, recently activated. Important considerations in attempts to inhibit the inhibitors include pseudoprogression and post-progression survival, abscopal effects, and immune-related adverse events, including endocrinopathies. [ABSTRACT FROM AUTHOR]

Forests are major sources of terrestrial CH4 and CO2 fluxes but not all surfaces within forests have been measured and accounted for. Stem respiration is a well-known source of CO2, but more recently tree stems have been shown to be sources of CH4 in wetlands and upland habitats. A study transect was established along a natural moisture gradient, with one end anchored in a forested wetland, the other in an upland forest and a transitional zone at the midpoint. Stem and soil fluxes of CH4 and CO2 were measured using static chambers during the 2013 and 2014 growing seasons, from May to October. Mean stem CH4 emissions were 68.8 ± 13.0 (mean ± standard error), 180.7 ± 55.2 and 567.9 ± 174.5 µg m−2 h−1 for the upland, transitional and wetland habitats, respectively. Mean soil methane fluxes in the upland, transitional and wetland were − 64.8 ± 6.2, 7.4 ± 25.0 and 190.0 ± 123.0 µg m−2 h−1, respectively. Measureable CH4 fluxes from tree stems were not always observed, but every individual tree in our experiment released measureable CH4 flux at some point during the study period. These results indicate that tree stems represent overlooked sources of CH4 in forested habitats and warrant investigation to further refine CH4 budgets and inventories. [ABSTRACT FROM AUTHOR]

When considering cities such as Lisbon, which due to their Köppen Geiger classification of ‘ Csa ’, witness hot and dry summers, the translation of local bottom-up knowhow upon climatic guidelines has been a topic of considerable dissemination over recent years. Depicting upon a concrete case study located in Lisbon’s historical quarter, the results from a previous bioclimatic study undertaken by the authors were taken further in order to consider how worst-case-scenarios of climate change (A1FI/RCP8.5) could potentially impact the existing human thermal environment within the square. In addition to considering its existing layout, public space design interventions were also examined within different thermal/temporal scenarios through the use the Physiologically Equivalent Temperature (PET) and PET(Load) indices. The results of the study revealed that within a climatic worse-case-scenario, and without any adaptive measures to address Physiological Stress (PS) levels, the majority of the square presented potential PS thresholds ranging between ‘Extreme Heat Stress Lv.3/4′, with PET values exceeding that of 51 °C and 56 °C. On the other hand, and particularly in regions prone to high levels of solar radiation, the thermal amelioration effects of the proposed public space design interventions presented reductions of PET values up to 16.6 °C. [ABSTRACT FROM AUTHOR]

The release of respiratory CO from polar tundra soils depends on the interactions between soil organic carbon and microbial communities, a topic of increasing importance due to global climate change. We experimentally amended samples of organic-rich tundra soil and mineral-rich temperate soil with dissolved organic carbon (DOC) and examined the following (at the same temperature): (1) the effects of DOC enrichment on bacterial and eukaryotic microbial biomasses, respiration, and acid phosphatase activities in both soil types, (2) whether relationships between microbial biomass, respiration, and acid phosphatase activities were similar across soil types, and (3) to what extent DOC enrichment altered the microbial food web in both soil types. Both soil types showed immediate, temporary increases in respiration following C enrichment, though the C source (amino acids, citric acid, or glucose) was an important source of variation. Additionally, a consistent relationship between respiration rates and acid phosphatase activities suggested that C and P cycling were linked in similar ways in the two soil types. The relationships of respiration rate and acid phosphatase activity to bacterial biomass were also consistent across soil types, excepting some amended tundra soil samples, perhaps due to greater protist bacterivory in those samples. In the tundra samples only, changes in predator biomass were accompanied by elevation of bacterial biomass-specific respiration rates. Our findings highlight the potential importance of protist bacterivory on microbial processes in tundra soils, but further research is needed to assess whether microbial food webs differ consistently among soils that vary in organic content. [ABSTRACT FROM AUTHOR]

Biogeochemical simulation models are important tools for describing and quantifying the contribution of agricultural systems to C sequestration and GHG source/sink status. The abundance of simulation tools developed over recent decades, however, creates a difficulty because predictions from different models show large variability. Discrepancies between the conclusions of different modelling studies are often ascribed to differences in the physical and biogeochemical processes incorporated in equations of C and N cycles and their interactions. Here we review the literature to determine the state-of-the-art in modelling agricultural (crop and grassland) systems. In order to carry out this study, we selected the range of biogeochemical models used by the CN-MIP consortium of FACCE-JPI (http://www.faccejpi.com): APSIM, CERES-EGC, DayCent, DNDC, DSSAT, EPIC, PaSim, RothC and STICS. In our analysis, these models were assessed for the quality and comprehensiveness of underlying processes related to pedo-climatic conditions and management practices, but also with respect to time and space of application, and for their accuracy in multiple contexts. Overall, it emerged that there is a possible impact of ill-defined pedo-climatic conditions in the unsatisfactory performance of the models (46.2%), followed by limitations in the algorithms simulating the effects of management practices (33.1%). The multiplicity of scales in both time and space is a fundamental feature, which explains the remaining weaknesses (i.e. 20.7%). Innovative aspects have been identified for future development of C and N models. They include the explicit representation of soil microbial biomass to drive soil organic matter turnover, the effect of N shortage on SOM decomposition, the improvements related to the production and consumption of gases and an adequate simulations of gas transport in soil. On these bases, the assessment of trends and gaps in the modelling approaches currently employed to represent biogeochemical cycles in crop and grassland systems appears an essential step for future research. [ABSTRACT FROM AUTHOR]

Once inorganic electron acceptors are depleted, organic matter in anoxic environments decomposes by hydrolysis, fermentation, and methanogenesis, requiring syntrophic interactions between microorganisms to achieve energetic favorability. In this classic anaerobic food chain, methanogenesis represents the terminal electron accepting (TEA) process, ultimately producing equimolar CO 2 and CH 4 for each molecule of organic matter degraded. However, CO 2 :CH 4 production in Sphagnum- derived, mineral-poor, cellulosic peat often substantially exceeds this 1:1 ratio, even in the absence of measureable inorganic TEAs. Since the oxidation state of C in both cellulose-derived organic matter and acetate is 0, and CO 2 has an oxidation state of +4, if CH 4 (oxidation state −4) is not produced in equal ratio, then some other compound(s) must balance CO 2 production by receiving 4 electrons. Here we present evidence for ubiquitous hydrogenation of diverse unsaturated compounds that appear to serve as organic TEAs in peat, thereby providing the necessary electron balance to sustain CO 2 :CH 4 > 1. While organic electron acceptors have previously been proposed to drive microbial respiration of organic matter through the reversible reduction of quinone moieties, the hydrogenation mechanism that we propose, by contrast, reduces C C double bonds in organic matter thereby serving as (1) a terminal electron sink, (2) a mechanism for degrading complex unsaturated organic molecules, (3) a potential mechanism to regenerate electron-accepting quinones, and, in some cases, (4) a means to alleviate the toxicity of unsaturated aromatic acids. This mechanism for CO 2 generation without concomitant CH 4 production has the potential to regulate the global warming potential of peatlands by elevating CO 2 :CH 4 production ratios. [ABSTRACT FROM AUTHOR]

In the Mediterranean basin the effects of climate warming on ecosystem functioning will strongly depend on the warming intensity directly but also on its effects on evapotranspiration and nutrient cycling. Climate manipulation experiments under field conditions are a source of unique empirical evidence regarding climate-related modifications of biotic processes. A field night-time warming experiment, simulating the predicted near-future increase in ambient temperatures (+0.3 up to 1 °C), was established in a Mediterranean shrub community located in Porto Conte (Italy) in 2001. After 11 years of continuous treatment, we labeled the dominant shrub Cistus monspeliensis with 13 CO 2 and studied the dynamics of the label allocation between aboveground and belowground pools and fluxes in warmed and ambient plots within 2 weeks of the chasing period. The interactions between C and N metabolism were assessed by parallel labeling of soil with K 15 NO 3. Most of the assimilated 13 C was respired by Cistus shoots (28–51%) within two weeks. Cistus under warming respired more 13 C label and tended to allocate less 13 C to leaves, branches and roots. The higher C and N content in microbial biomass in warming plots, combined with the higher N content in plant tissues and soil, evidenced a greater N mobilization in soil and a better nutrient status of the plants as compared to the ambient treatment. Acceleration of N cycling is probably responsible for higher respiratory C losses, but combined with the reduction in the number of frost days, should also positively affect plant photosynthetic performance. We conclude that, although Cistus plants are already growing in conditions close to their thermal optimum, long-term warming will positively affect the performance of this species, mainly by reducing the nutrient constraints. This positive effect will highly depend on the frequency and amount of rain events and their interactions with soil N content. [ABSTRACT FROM AUTHOR]

Purpose: Climate-change impacts can be mitigated through greater use of bioenergy, but the extent to which specific options actually reduce overall impacts needs to be assessed. Most bioenergy assessments have used proxy measures for assessing its merits. Here, a new approach is presented, whereby the contribution of bioenergy use is assessed through quantifying marginal changes in climate-change impacts that result from the implementation of a bioenergy option. Methods: Marginal climate-change impacts were calculated for one specific example of a bioenergy option, conversion of an unutilised mature forest into a production forest harvested repeatedly for bioenergy over successive 25-year rotations. The overall benefit of the option was assessed by including stand-level carbon dynamics, global carbon-cycle feedback, progressively changing radiative efficiency and marginal impact sensitivity of warming. It also includes a differentiated assessment of three kinds of climatic impacts: direct-warming, rate-of-warming and cumulative-warming impacts. Marginal impacts were calculated and summed over 100 years to assess the overall marginal impact of this bioenergy option. Results and discussion: Bioenergy use in this specific example led to a large initial loss of biomass carbon followed by an ongoing and accumulating benefit through fossil-fuel substitution. This caused adverse climatic impacts over the first two rotations as the effects of the on-site carbon loss dominated the overall impact, but the option became increasingly beneficial over longer time frames as the benefit of fossil-fuel substitution accrued and eventually dominated. Summed over 100 years, the bioenergy option reduced direct-temperature and rate-of-warming impacts whilst increasing cumulative-warming impacts. The average of the three kinds of impacts showed a slight mitigation benefit by reducing overall impacts. In the particular example, bioenergy use was assessed to have a more beneficial effect if the analysis was carried out under the assumption of higher-emission concentrations pathways, or if it assumed a steeper relationship between climate perturbations and impacts. Conclusions: The usefulness of any climate-change mitigation option ultimately relates to the marginal climate-change impacts it can avert. It is shown here that marginal impacts can be calculated in routine operation and that they can provide an objective and methodologically consistent assessment of the mitigation potential of bioenergy use. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of NZVI on composting carbon cycle and carbon balance was investigated. • A NZVI-regulated composting C cycle was experimentally demonstrated. • NZVI addition increased CO 2 and CH 4 emissions by 51% and 128% respectively. • NZVI addition enhanced bacteria promoting hygiene of final product. The effectiveness of nano-zero-valent-iron (NZVI) addition during composting of pig manure (PM) was investigated. Different dosages of NZVI were mixed with PM substrate during a 50 days composting process. The results revealed that the higher share of NZVI addition, the higher OM degradation rate is. On contrary, it was observed that the higher share of NZVI addition, the lower the fulvic acid and the humin degradation rate is. Meanwhile, NZVI amendment increased the CO 2 and CH 4 emissions by 29–47 % and 53–57 %, respectively. The in-depth analysis showed that NZVI addition increased the activity of Sphaerobacter and Luteimonas , which eventually led to the degradation of hard-to-degrade OM faster. Additionally, NZVI was found to increase the filtration of microorganisms, reducing the toxicity and hygiene of compost products. No significant improvement in humic substance enhancement was observed during composting with NZVI addition but improved OM degradation. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are persistent organic pollutants globally, with a continuous increase in MP wastes near and away from the regions of human activities. Studies to date aimed to explore the impact of MPs on ecosystems, but the area of research could not go beyond environmental pollution caused by MPs. To address the menace of MPs, scientists need to pay enough attention to the biogeochemical cycles, microbial communities, and functional microorganisms. Hence, this study aimed to evaluate the impact of adding 0.3% (mass ratio) [low-concentration (LC) group] and 1% [high-concentration (HC) group] of polyamide (PA) MP to the soil microenvironment with regard to the aforementioned parameters. PA MP decreased the soil microbial diversity (Shannon and Simpson indices, P < 0.05). At the phylum level, PA MP increased the abundance of Acidobacteria, Firmicutes , and Crenarchaeota (P < 0.05); at the genus level, it enhanced that of Geobacter , Thiobacillus, Pseudomonas, and Bradyrhizobium (P < 0.01) while decreased that of Bacillus, Flavisolibacter, Geothrix , and Pseudarthrobacter (P < 0.05). PA MP affected the carbon (C) cycle. PA MP accelerated the soil C fixation by enhancing the abundance of the genes accA and pccA. The LC PA MP accelerated organic C degradation and methane metabolism by changing the abundance of mnp, chiA, mcrA, pmoA , and mmoX genes, while the HC PA MP inhibited them with increasing the experimental time. Regarding the effects of PA on the nitrogen (N) cycle, the PA MP promoted N assimilation and ammonification by increasing the abundance of the genes gdh and ureC , the impact of PA MP on N fixation and denitrification depended on its concentration and treating time. This study showed that PA MP impacted the microbial consortium, it also affected the C and N cycles and its effect depended on its concentration and the treating time. [Display omitted] • PA MP significantly impacted the diversity of soil bacterial community. • PA MP accelerated the soil carbon fixation. • PA MP promoted the soil nitrogen assimilation and ammonification. • The impact of PA MP on the C and N cycle depended on its concentration and treating time. [ABSTRACT FROM AUTHOR]

In Europe, rural depopulation and the abandonment of pastoral practices in mountain areas trigger deep changes in the landscape, which result in the accumulation of lignified fuels and the increased risk of fires, a sensitive issue in southern areas of the continent. From prehistory, a pyric herbivory has been practiced in European mountain regions. Pastoral fires created open communities, amenable to wild and domestic grazing, and herbivores perpetuated them by controlling fuel accumulation. In the last decades, the declining of extensive herbivory has given a prominent role to prescribed fires in order to preserve open communities. As a consequence, a new scenario of increased burning frequency and reduced herbivory emerges, which may affect the soil function in different ways. Our aim was to evaluate the effects of experimental burnings on soil function and nutrients cycling of a mountain gorse ( Ulex gallii Planch.) shrubland, with the absence/presence of extensive grazing. We performed traditional “bush-to-bush” burnings in three experimental mountain plots and analysed seasonally along a 2-year period the soil function in relation to C-cycle (dissolved organic C, microbial biomass C and glucosidase activity), N-cycle (inorganic N forms, dissolved organic N, microbial biomass N and urease activity), P-cycle (phosphatase activity) and overall bacterial catabolic activity. Fire effects were time dependent and extensive grazing had a low influence on them. Fire originated a transient pulse of inorganic-N forms in the short term, which disappeared after 1 year, and increased dissolved organic N forms, which attenuated with time. In burned areas, a decrease of total N and microbial biomass N, and a slow-down of N- and P-cycle enzymatic activities were observed in the mid-term coinciding with a decrease of soil moisture. Since a higher burning frequency is a feasible situation that may affect mountain, nutrient-poor soils, the enduring effects of prescribed fires need to be taken into account to establish the optimal date of burning and the adequate recurrence regime that avoid negative impacts on the soil function and minimize the loss of nutrients from the soil reservoir. [ABSTRACT FROM AUTHOR]

Climate change (i.e., high atmospheric carbon dioxide (CO2) concentrations (=400 ppm); increasing air temperatures (2-4 °C or greater); significant and/or abrupt changes in daily, seasonal, and interannual temperature; changes in the wet/dry cycles; intensive rainfall and/or heavy storms; extended periods of drought; extreme frost; heat waves and increased fire frequency) is and will significantly affect soil properties and fertility, water resources, food quantity and quality, and environmental quality. Biotic processes that consume atmospheric CO2 and create organic carbon (C) that is either reprocessed to CO2 or stored in soils, are the subject of active current investigations with great concern over the influence of climate change. In addition, abiotic C cycling and its influence on the inorganic C pool in soils is a fundamental global process in which acidic atmospheric CO2 participates in the weathering of carbonate and silicate minerals, ultimately delivering bicarbonate and Ca2+ or other cations that precipitate in the form of carbonates in soils or are transported to the rivers, lakes, and oceans. Soil responses to climate change will be complex, and there are many uncertainties and unresolved issues. The objective of the review is to initiate and further stimulate a discussion about some important and challenging aspects of climate-change effects on soils, such as accelerated weathering of soil minerals and resulting C and elemental fluxes in and out of soils, soil/geo-engineering methods used to increase C sequestration in soils, soil organic matter (SOM) protection, transformation and mineralization, and SOM temperature sensitivity. This review reports recent discoveries and identifies key research needs required to understand the effects of climate change on soils. [ABSTRACT FROM AUTHOR]

Decomposition of plant debris is a critical process during the filling phase of water reservoir. Here we investigated the impact of decomposition of the plant species ( Cytisus scoparius , Pteridium aquilinum and Juncus effusus ) in the Alaco reservoir (southern Italy). To simulate lake ecological conditions, a microcosm experiment was carried-out for 100 days with litters incubated in water lake in aerobic conditions in the light at two temperatures (+12 °C and +24 °C). Litter types were characterized by classic proximate chemical analyses (total C and N, labile C, cellulose and lignin content, C/N and lignin/N ratios) and, at molecular level, by solid-state 13 C CPMAS NMR. Water quality was monitored through pH, electrolytic conductivity, DOC, BOD 5 and dissolved oxygen. Decomposition was more rapid for C. scoparius , intermediate for J. effusus and slower for P. aquilinum. After 100 days of decomposition for all litter type the O -alkyl-C region, associated with sugars and polysaccharides, decreased and the aliphatic alkyl-C region increased for C. scoparius and P. aquilinum . Immediately after litter submergence, DOC and BOD 5 dramatically increased, reaching high values for P. aquilinum and C. scoparius . However, after 100 days of incubation, DOC concentration sharply decreased reaching values usually below 50 mg l −1 , and after 10 days of incubation BOD 5 values dropped to values close to zero. Although carried out in laboratory, the experiment showed that submerged plant litter during decomposition produces a short-term changes of water quality that rapidly returns to background level. [ABSTRACT FROM AUTHOR]

Global climate change is already having significant impacts on arctic and alpine ecosystems, and ongoing increases in temperature and altered precipitation patterns will affect the strong seasonal patterns that characterize these temperature-limited systems. The length of the potential growing season in these tundra environments is increasing due to warmer temperatures and earlier spring snow melt. Here, we compare current and projected climate and ecological data from 20 Northern Hemisphere sites to identify how seasonal changes in the physical environment due to climate change will alter the seasonality of arctic and alpine ecosystems. We find that although arctic and alpine ecosystems appear similar under historical climate conditions, climate change will lead to divergent responses, particularly in the spring and fall shoulder seasons. As seasonality changes in the Arctic, plants will advance the timing of spring phenological events, which could increase plant nutrient uptake, production, and ecosystem carbon (C) gain. In alpine regions, photoperiod will constrain spring plant phenology, limiting the extent to which the growing season can lengthen, especially if decreased water availability from earlier snow melt and warmer summer temperatures lead to earlier senescence. The result could be a shorter growing season with decreased production and increased nutrient loss. These contrasting alpine and arctic ecosystem responses will have cascading effects on ecosystems, affecting community structure, biotic interactions, and biogeochemistry. [ABSTRACT FROM AUTHOR]

Boiling Springs Lake ( BSL) is an oligotrophic, acidic geothermal feature where even very low levels of microbial heterotrophic production still exceed autotrophy. To test whether allochthonous leaf litter (LL) inputs fuel this excess, we quantified leaf litterfall, leaching and decomposition kinetics, and measured the impact of organic amendments on production, germination and cell growth, using pyrosequencing to track changes in microbial community composition. Coniferous leaves in BSL exhibited high mass loss rates during leaching and decomposition, likely due to a combination of chemical hydrolysis and contributions of both introduced and endemic microbes. We measured very low in situ 3H-thymidine incorporation over hours by the dominant chemolithotroph Acidimicrobium (13-65 μg C L−1 day−1), which was inhibited by simple C sources (acetate, glucose). Longer term incubations with additions of 0.01-0.02% complex C/N sources induced germination of the Firmicute Alicyclobacillus within 1-2 days, as well as growth of Acetobacteraceae after 3-4 days. LL additions yielded the opposite successional patterns of these r-selected heterotrophs, boosting production to 30-150 μg C L−1 day−1. Growth and germination studies suggest both prokaryotes and fungi likely consume allochthonous organics, and might be novel sources of lignocellulose-degrading enzymes. A model of BSL's C budget supports the hypothesis that allochthonous inputs fuel seasonal microbial heterotrophy, but that dissolved organic C sources greatly exceed direct LL inputs. [ABSTRACT FROM AUTHOR]

The increasing input of anthropogenically derived nitrogen (N) to ecosystems raises a crucial question: how does available N modify the decomposer community and thus affects the mineralization of soil organic matter ( SOM). Moreover, N input modifies the priming effect ( PE), that is, the effect of fresh organics on the microbial decomposition of SOM. We studied the interactive effects of C and N on SOM mineralization (by natural 13C labelling adding C4-sucrose or C4-maize straw to C3-soil) in relation to microbial growth kinetics and to the activities of five hydrolytic enzymes. This encompasses the groups of parameters governing two mechanisms of priming effects - microbial N mining and stoichiometric decomposition theories. In sole C treatments, positive PE was accompanied by a decrease in specific microbial growth rates, confirming a greater contribution of K-strategists to the decomposition of native SOM. Sucrose addition with N significantly accelerated mineralization of native SOM, whereas mineral N added with plant residues accelerated decomposition of plant residues. This supports the microbial mining theory in terms of N limitation. Sucrose addition with N was accompanied by accelerated microbial growth, increased activities of β-glucosidase and cellobiohydrolase, and decreased activities of xylanase and leucine amino peptidase. This indicated an increased contribution of r-strategists to the PE and to decomposition of cellulose but the decreased hemicellulolytic and proteolytic activities. Thus, the acceleration of the C cycle was primed by exogenous organic C and was controlled by N. This confirms the stoichiometric decomposition theory. Both K- and r-strategists were beneficial for priming effects, with an increasing contribution of K-selected species under N limitation. Thus, the priming phenomenon described in 'microbial N mining' theory can be ascribed to K-strategists. In contrast, 'stoichiometric decomposition' theory, that is, accelerated OM mineralization due to balanced microbial growth, is explained by domination of r-strategists. [ABSTRACT FROM AUTHOR]

Currently, the global annual flux of methane (CH) to the atmosphere is fairly well constrained at ca. 645 Tg CH year. However, the relative magnitudes of the fluxes generated from different natural (e.g. wetlands, deep seepage, hydrates, ocean sediments) and anthropogenic sources remain poorly resolved. Of the identified natural sources, the contribution of vegetation to the global methane budget is arguably the least well understood. Historically, reviews of the contribution of vegetation to the global methane flux have focused on the role of plants as conduits for soil-borne methane emissions from wetlands, or the aerobic production of methane within plant tissues. Many recent global budgets only include the latter pathway (aerobic methane production) in estimating the importance of terrestrial vegetation to atmospheric CH flux. However, recent experimental evidence suggests several novel pathways through which vegetation can contribute to the flux of this globally important, trace greenhouse gas (GHG), such as plant cisterns that act as cryptic wetlands, heartwood rot in trees, the degradation of coarse woody debris and litter, or methane transport through herbaceous and woody plants. Herein, we synthesize the existing literature to provide a comprehensive estimate of the role of modern vegetation in the global methane budget. This first, albeit uncertain, estimate indicates that vegetation may represent up to 22 % of the annual flux of methane to the atmosphere, contributing ca. 32-143 Tg CH year to the global flux of this important trace GHG. Overall, our findings emphasize the need to better resolve the role of vegetation in the biogeochemical cycling of methane as an important component of closing the gap in the global methane budget. [ABSTRACT FROM AUTHOR]

Abstract: Microbial decay of emergent macrophyte litters in the standing-dead phase is an essential component of litter decomposition and thus carbon (C) cycle in wetland ecosystems. In this study, we examined the amount of microbial respiration from standing litter in a Deyeuxia angustifolia-dominated marsh in the Sanjiang Plain by integrating field studies with laboratory experiments. In the field, CO2 evolution from standing litter exhibited a pronounced diel pattern, with high evolution rates concurring with increasing litter water potential at night. Notably, significant CO2 evolution even existed at temperature of −4°C. Overall, rates of CO2 evolution showed strong positive correlations with relative humidity and litter water potential. In the laboratory, rates of CO2 evolution from wetted culms and leaves increased with increasing temperature, and the relationship between CO2 evolution rates and temperature could be well described with an exponential model. Based on extrapolation from temperature-adjusted mean CO2 evolution rates and standing litter mass, annual CO2 fluxes of culms (3.07gCm−2 yr−1) and leaves (6.81gCm−2 yr−1) accounted for 2.32% (culms, 132.30gCm−2 yr−1) and 6.94% (leaves, 98.20gCm−2 yr−1) of the corresponding annual net aboveground production, respectively. In total, microbial mineralization of standing litter only contributed to 1.12% of the ecosystem respiration (880gCm−2 yr−1). Our results highlight the importance of standing-dead phase in litter decomposition and C cycle in wetlands, and also suggest that CO2 flux from standing litter could even be neglected in assessing C budget in the D. angustifolia-dominated freshwater marshes in the Sanjiang Plain, Northeast China. [Copyright &y& Elsevier]