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Soil Biology & Biochemistry
Pergamon Press.
Soil Biology & Biochemistry

Pergamon Press.

0038-0717

Soil Biology & Biochemistry/Journal Soil Biology & BiochemistrySCIISTPAHCI
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    Impact of nitrogen addition on plant-soil-enzyme C–N–P stoichiometry and microbial nutrient limitation

    Xu H.Qu Q.Li G.Liu G....
    11页
    查看更多>>摘要：? 2022 Elsevier LtdGlobal atmospheric nitrogen deposition significantly affects the nutrient cycling and C–N–P stoichiometry in ecosystems. Herein, a global meta-analysis was conducted based on 898 pairwise observations to analyze the impact of nitrogen addition on plant-soil-enzyme C–N–P stoichiometry and microbial nutrient limitation in different ecosystem types (cropland, grassland, and forest), nitrogen addition intensity (0–5, 5–10, and >10 g N m?2 yr?1) and duration (0–5, 5–10, and >10yr). Results showed that nitrogen addition significantly decreased plant C:N (shoot: 16.5%, root: 27.1%, litter: 16.5%), soil C:N (5.9%), enzyme C:P (1.2%), and enzyme N:P (5.1%), whereas significantly increased soil C:P (4.9%), enzyme C:N (7.1%), vector angle (4.4%), vector length (3.9%), and plant N:P (shoot: 24.1%, root: 23.8%, and litter: 13.5%). Furthermore, nitrogen addition mainly affected the enzyme C:N and vector length in grasslands. Additionally, the changes in C:N in plants, soil, and enzymes, and vector angle and length were higher at nitrogen addition intensity of >10 g N m?2 yr?1. The changes in C:N and C:P in plant and soil were higher at nitrogen addition duration of >10 yr. Finally, the N:P in shoot, soil and enzyme, and vector angle were strongly correlated with mean annual precipitation (MAP). In conclusion, nitrogen addition significantly reduced the C:N ratio in plants and soil and increased plant N:P, and microbial C and P limitation. These effects vary with the ecosystem type, MAP, and nitrogen addition intensity and duration. The results improve our understanding of the plant-soil-microbial nutrient cycling processes in terrestrial ecosystems under global nitrogen deposition.
      原文链接:
    • NSTL
    • Elsevier

    Mechanisms and kinetics of (de-)protection of soil organic carbon in earthworm casts in a tropical environment

    Puche N.Rumpel C.Le Mer G.Jouquet P....
    11页
    查看更多>>摘要：? 2022 Elsevier LtdEarthworms have potential to stabilize soil organic carbon (SOC), but the biophysical controls on SOC dynamics in earthworm casts and the SOC residence time in casts is poorly known. To this end, we aimed to investigate (1) the kinetics of SOC (de-) protection in earthworm casts deposited in a tropical environment and (2) changes in the spatial relationships between fresh particulate organic matter (POM) and pore architecture within casts. Our experimental approach was to espose casts produced by the anecic earthworm Amynthas adexilis to tropical temperature and rainfall by placing them in a woodland in northern Vietnam. For 400 d, we monitored the dynamics of cast microstructures using X-ray micro-computed tomography and compared them to those of the surrounding soil aggregates (control). We also measured potential CO2 emissions of the same samples in a laboratory incubation. As expected, recently egested casts had higher SOC (1.9-fold) and POM volumes (7-fold) than aggregates, whereas their total imaged porosity was 4 times less. The SOC of casts was more labile than SOC of aggregates, as casts had 3 times more potentially mineralizable SOC. By 72 d of exposure to field conditions, the casts and aggregates had similar potential SOC mineralization, indicating that they had developed a similar level of SOC protection. Temporal changes in SOC mineralization rates were related to variations in POM volume, particularly those connected to the outside of the cast. After 400 d of exposure, casts had still greater POM volumes (2.5-fold) and higher SOC contents (1.6-fold) but similar total imaged porosity and SOC stability as aggregates. In conclusion, these results clearly indicated the direct involvement of earthworms in SOC stabilization through their impact on POM and pore spatial arrangements, which may have led to prolonged SOC sequestration for > 400 d.
      原文链接:
    • NSTL
    • Elsevier

    Pyrogenic organic matter as a nitrogen source to microbes and plants following fire in an Arctic heath tundra

    Xu W.Elberling B.Ambus P.L.
    9页
    查看更多>>摘要：? 2022 The AuthorsIn recent years, wildfire frequency and severity has increased in the Arctic tundra regions due to climate change. Pyrogenic organic matter (PyOM) is a product of incomplete combustion of biomass containing nutrients such as nitrogen (N), and is expected to affect ecosystem N cycling during a post-fire recovery period. We investigated effects of fire on soil biogeochemical cycles with a focus on pyrogenic N turnover over two subsequent growing seasons, combined with and without summer warming, in an Arctic heath tundra, West Greenland. The summer warming was achieved by deployment of open top chambers (OTCs). We simulated an in situ tundra fire by removing vegetation and litter, and scorching/heating soil surface followed by the addition of 15N-labelled PyOM (derived from aboveground biomass and litter) to the soil surface in plots with and without summer warming. A darker surface after the simulated fire resulted in an increase of 1.3 °C in soil temperature at 5-cm depth over the growing seasons. The fire also caused a nine-fold increase in soil NH4+-N and three-fold increase in soil NO3?-N concentrations at 7-cm depth after two years. Tracing the fate of 15N-labelled PyOM, 21 days after its application, showed low 15N recovery in microbial biomass (0.4%) and total dissolved N (TDN) pools (0.01%). Microbial and root 15N recovery increased two-fold and 15-fold after one year, respectively, and TDN 15N recovery increased two-fold after two years, suggesting that relatively recalcitrant N of PyOM can be partly transformed into plant-available forms over time. Root and TDN 15N recovery was also significantly higher after two years of summer warming than under ambient temperature conditions, suggesting that summer warming can enhance availability of PyOM-N for recovering plants after the fire. Hence, we conclude that fire-induced PyOM can act as an N source for plant recovery in this Arctic tundra ecosystem for years after the fire, and this N source will become increasingly important in a future warmer climate.
      原文链接:
    • NSTL
    • Elsevier

    Salinity affects microbial composition and function in artificially induced biocrusts: Implications for cyanobacterial inoculation in saline soils

    Wu L.Xia L.Song S.Lan S....
    9页
    查看更多>>摘要：? 2022 Elsevier LtdCyanobacterial inoculation is a promising technology that can induce biocrust development, for stabilizing degraded soils in dryland environments. However, it is challenging to grow cyanobacteria in dry, saline soils, which limits the application of this technology. In this study, NaCl was added into field-collected induced biocrusts to investigate how salt affects the biocrust community. This fundamental knowledge improves our assessment of microbial salinity preference and adaptation, and can guide researchers to select the appropriate cyanobacterial inoculants for saline soil restoration. The results showed that the biocrusts induced by inoculating Microcoleus vaginatus and Scytonema javanicum could survive 1.0% salinity, although both salt and drought stresses significantly inhibited microbial biomass and metabolism (P < 0.05), and salinity led to an obvious shift in microbial community structure. Compared to salt stress, drought seems to provide a vital ecological protection for the biocrusts, allowing them to be active only under relative low salinity after hydration. In the induced biocrusts, cyanobacteria were always the dominant organisms (even 18 years since inoculation), whereas under elevated salinity, cyanobacterial communities with lower relative abundance had a higher survival percentage of M. steenstrupii and Phormidium sp. Altogether, our results showed that both prokaryotic and eukaryotic communities have obvious salinity preference in the cyanobacteria-induced biocrusts. These results suggest that cyanobacterial inoculation strategies can be adapted in response to the soil salinity conditions. Furthermore, a combined inoculation of M. steenstrupii and Phormidium sp. appears to be favorable approach that is expected to improve cyanobacterial inoculation technology in saline soils.
      原文链接:
    • NSTL
    • Elsevier

    Deep-C storage: Biological, chemical and physical strategies to enhance carbon stocks in agricultural subsoils

    Button E.S.Chadwick D.R.Jones D.L.Pett-Ridge J....
    19页
    查看更多>>摘要：? 2022 The AuthorsDue to their substantial volume, subsoils contain more of the total soil carbon (C) pool than topsoils. Much of this C is thousands of years old, suggesting that subsoils offer considerable potential for long-term C sequestration. However, knowledge of subsoil C behaviour and manageability remains incomplete, and subsoil C storage potential has yet to be realised at a large scale, particularly in agricultural systems. A range of biological (e.g. deep-rooting), chemical (e.g. biochar burial) and physical (e.g. deep ploughing) C sequestration strategies have been proposed, but are yet to be assessed. In this review, we identify the main factors that regulate subsoil C cycling and critically evaluate the evidence and mechanistic basis of subsoil strategies designed to promote greater C storage, with particular emphasis on agroecosystems. We assess the barriers and opportunities for the implementation of strategies to enhance subsoil C sequestration and identify 5 key current gaps in scientific understanding. We conclude that subsoils, while highly heterogeneous, are in many cases more suited to long-term C sequestration than topsoils. The proposed strategies may also bring other tangible benefits to cropping systems (e.g. enhanced water holding capacity and nutrient use efficiency). Furthermore, while the subsoil C sequestration strategies we reviewed have large potential, more long-term studies are needed across a diverse range of soils and climates, in conjunction with chronosequence and space-for-time substitutions. Also, it is vital that subsoils are more consistently included in modelled estimations of soil C stocks and C sequestration potential, and that subsoil-explicit C models are developed to specifically reflect subsoil processes. Finally, further mapping of subsoil C is needed in specific regions (e.g. in the Middle East, Eastern Europe, South and Central America, South Asia and Africa). Conducting both immediate and long-term subsoil C studies will fill the knowledge gaps to devise appropriate soil C sequestration strategies and policies to help in the global fight against climate change and decline in soil quality. In conclusion, our evidence-based analysis reveals that subsoils offer an untapped potential to enhance global C storage in terrestrial ecosystems.
      原文链接:
    • NSTL
    • Elsevier

    Soil warming and nitrogen addition facilitates lignin and microbial residues accrual in temperate agroecosystems

    Ma L.Wu D.Wu W.Du Z....
    10页
    查看更多>>摘要：? 2022 Elsevier LtdBoth warming and nitrogen (N) addition affect the chemistry and characteristics of soil organic matter (SOM). However, their interactive impacts on molecular compositions and origins (plant- or microbial-derived) in agroecosystems are indeterminate. A nine-year field trial study in Northern China was undertaken to quantify the effects of warming (+2 °C), N addition (315 kg N ha?1 yr?1), and their interaction on SOM content and its composition, using biomarkers (i.e., free lipids, lignin phenols and amino sugars) and 13C NMR. Despite insignificant changes in bulk SOM content, the characteristics (i.e., molecular constituents, lability and source origin) were significantly influenced by warming and/or N addition in surface soil (0–10 cm), but not in the subsurface soil (10–20 cm). The SOM was composed of approximately 18–27% microbial residues with the bulk derived from fungi (up to 4–fold higher than bacteria). Warming alone reduced total free lipids (mainly short-chain lipids, <C20) by 21%, but increased lignin phenols (vanillyls and syringyls) by 37% and microbial residues (quantified as amino sugars) by 31%. Nitrogen addition alone increased lignin phenols by 28% and microbial residues by 30% in surface soils but had a limited effect on free lipids content. Combined warming and N addition additively increased total free lipids by 40% and lignin phenols by 42% and the ratio of fungal/bacterial microbial residues in the surface soils. Collectively, our study results suggest that warming and nitrogen addition have a synergistic positive effect on SOM persistence in temperate agroecosystem via accrual of lignin phenols and microbial residues.
      原文链接:
    • NSTL
    • Elsevier

    Rigorous, empirical, and quantitative: a proposed pipeline for soil health assessments

    Wade J.Culman S.W.Martin T.K.Sprunger C.D....
    10页
    查看更多>>摘要：? 2022Soil health is a promising lens through which to approach land management, having the potential to serve as a descriptor of biophysical processes and as an effective communication tool across stakeholders. However, this potential has been largely unrealized due to difficulty in quantitatively assessing soil health and linking those assessments to outcomes. Here we discuss many multiple persistent obstacles to quantitative soil health assessment and outline a suite of analyses to help address those obstacles. Specifically, we propose a quantitative approach to developing and selecting soil health indicators that help connect management-induced changes in soil health to specific outcomes (e.g., yield or water quality). To demonstrate the utility of this approach, we perform a small case study using published data from North Carolina and New York cropping systems. Additionally, we outline how this approach is scalable and flexible enough to integrate future soil health metric development. The proposed approach stands to provide a quantitative, empirical basis for future measurement, assessment, and interpretation of soil health.
      原文链接:
    • NSTL
    • Elsevier

    Disentangling carbon stabilization in a Calcisol subsoil amended with iron oxyhydroxides: A dual-13C isotope approach

    Fang Y.Collins D.Harvey D.Mehra P....
    13页
    查看更多>>摘要：? 2022Calcisols pose some unique challenges, particularly relating to their low organic carbon (C) content and low C storage ceiling. To address this, we investigated the role of iron (Fe) oxyhydroxides – goethite and ferrihydrite (0.36, 0.72, 3.6, and 7.2 g kg?1 soil) in the presence of a labile C substrate (glucose) to simulate rhizodeposition, on C-cycling. As there were three potential C sources: (i) glucose-C, (ii) native SOC, and (iii) soil inorganic C (SIC), a novel dual-13C isotope approach (δ13C-enriched glucose of 29 and 81‰) was implemented to accurately differentiate these three C sources from a Calcisol subsoil (δ13SOC, ?23‰; δ13SIC, ?3.6‰). Over 28 days, across the glucose and Fe oxyhydroxide treatments, 34.8–41.7% of the supplied glucose-C (1.0 g C kg?1 soil), 7.5–9.6% of the native SOC (3.7 g kg?1 soil), and 0.11–0.19% of the SIC (48 g kg?1 soil) were lost as CO2. Goethite and ferrihydrite generally stabilized organic C (including glucose-C and native SOC) which occurred primarily within the first 10 days following amendment with Fe oxyhydroxide, and the stabilization effect generally increased with increasing Fe oxyhydroxide dose. This is likely due to rapid Fe-OC adsorption that protected the OC from microbial decomposition. Ferrihydrite (cf. goethite) had a smaller effect on suppressing positive priming of SOC mineralization induced by glucose, possibly resulting from the lower C use efficiency and less stable Fe-OC associations due to the higher dissolution rate of ferrihydrite. The SIC loss increased after glucose addition, which was further enhanced by Fe oxyhydroxides. We conclude that Fe oxyhydroxides may be useful amendments for increasing SOC in highly alkaline Calcisols.
      原文链接:
    • NSTL
    • Elsevier

    Poor recovery of fungal denitrification limits nitrogen removal capacity in a constructed Gulf Coast marsh

    Mortazavi B.Tatariw C.Starr S.F.Cherry J.A....
    8页
    查看更多>>摘要：? 2022 Elsevier LtdWidespread degradation and destruction of coastal wetlands over the last century have spurred on the practice of creating salt marshes to mitigate losses of wetland area and ecosystem function. Constructed marshes can quickly recover plant biomass, but biogeochemical functions, such as nitrogen removal capacity through denitrification, can take decades to centuries to recover. One potential mechanism for this uncoupling of structural and functional recovery is that an impaired microbial community subsequently impedes the nitrogen removal capacity of constructed marshes. While both bacteria and fungi can contribute to nitrogen removal via denitrification, little is known about fungal denitrification in wetlands, even though it has the potential to contribute to climate change via the production of the greenhouse gas nitrous oxide. Here, we measured fungal and bacterial denitrification potential rates and fungal biomass in sediments collected from a 33-year-old constructed marsh and a reference natural marsh to assess both a) the relative contribution of each group to total nitrogen removal and b) whether fungal biomass accrual is a driver of functional recovery in salt marshes. To assess the relative contributions of fungi and bacteria to denitrification, we added selective inhibitors (antifungal, antibacterial, or both) to sediments from each marsh and measured potential fungal and bacterial denitrification rates. We also measured sediment ergosterol concentrations seasonally as a proxy for fungal biomass. In the absence of inhibitors, denitrification potential rates in the constructed marsh were three times lower than in natural marsh sediment. Further, denitrification rates in the constructed marsh remained similarly low regardless of increasing inhibitor concentration, whereas denitrification rates in the natural marsh declined with increasing inhibitor concentration. When either inhibitor was added alone, denitrification was stimulated in the natural marsh, but was suppressed in the constructed marsh, suggesting an apparent competitive release, where the reduction of either bacterial or fungal competition for substrate thereby allowed the remaining competitor greater access to the substrate, in the natural marsh. We observed that compared to the constructed marsh, fungi in the natural marsh contributed ～30% more (50% vs. 21%) to denitrification, and that fungal biomass was generally higher. Collectively, these data suggest that 3 decades post construction, denitrification rates and the contribution of fungal denitrification to total denitrification are lower in the constructed marsh than the natural marsh. These data also suggest that fungal biomass may limit the recovery of nitrogen removal in constructed marshes and that fungal denitrification can be an important pathway of N removal in salt marsh ecosystems.
      原文链接:
    • NSTL
    • Elsevier

    Assessing the long-term impact of urease and nitrification inhibitor use on microbial community composition, diversity and function in grassland soil

    Duff A.M.Forrestal P.Ikoyi I.Brennan F....
    11页
    查看更多>>摘要：? 2022 The AuthorsReductions in ammonia (NH3) and nitrous oxide (N2O) emissions from agricultural systems are critical for achievement of sustainability targets that underpin international efforts on climate and biodiversity. Urease inhibitors (UI) such as N-(n-butyl) thiophosphoric triamide (NBPT) and nitrification inhibitors (NI) such as dicyandiamide (DCD) slow down microbial and chemical N transformation rates in soil, resulting in decreased environmental N losses. To date there has been minimal assessment of the long-term non-target impacts of UI and NI on soil microbial communities and biological function in grasslands. Utilising a temperate grassland field experiment where fertilisers (with or without inhibitors) were repeatedly applied over a five year period, we assessed the impact of individual or combined inhibitor use on microbial community composition, abundance and function via a combination of functional assays, quantitative polymerase chain reaction (qPCR) assays and amplicon sequence analysis. We also investigated the effect of N inhibitor use on the N functional community, and whether the form of applied N fertiliser (i.e. calcium ammonium nitrate (CAN) or Urea) affected microbial community composition and function. Treatments included a Control (no N); CAN; Urea; Urea + NBPT (UI); Urea + DCD (NI); and Urea + DCD + NBPT (NI & UI). There was no impact of either UI or NI use on non-target microbial community composition or abundance. Function and the abundance of N cycling communities were mainly unaffected by fertilisation or the use of inhibitors. The observed effect of NI was primarily on the nitrification process. There was a significant reduction in nitrification potential associated with the use of NI, and in the case of the Urea + DCD treatment a reduction in COMAMMOX nitrifier abundance, and an increase in potential N mineralisation and N2O emissions. Finally, there was a significant impact of fertilisation and fertiliser type (i.e. CAN or Urea) on the fungal community structure but no impact on bacterial community structure. These results provide a knowledge base that will inform policy regarding the utilisation of N inhibitors as a mitigation measure for reducing gaseous N losses in grasslands.
      原文链接:
    • NSTL
    • Elsevier