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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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    Lithologic control of microbial-derived carbon in forest soils

    Hu, PeileiZhang, WeiChen, HongsongXu, Lin...
    10页
    查看更多>>摘要：Microbial necromass carbon (MNC) is an important contributor to soil organic carbon. The influence of lithology on MNC remains unclear. MNC is often regarded as a stable, uniform entity, but little consideration has been given to its unprotected and protected fractions. We measured MNC contents in particulate organic matter, which represents the unprotected fraction, and in mineral-associated organic matter, which represents the protected fraction, in forest soils over limestone and clastic rock across a climatic gradient in southwest China. Additionally, nearby croplands with long-term soil tillage were selected for comparison. On average, the contents of protected and unprotected MNC were 52-56% greater in forest soils over limestone compared to clastic rock. Both MNC fractions over clastic rock decreased with increasing the mean annual temperature (MAT), whereas only the unprotected fraction decreased with increasing the MAT over limestone. MNC was regulated by iron oxides and microbial biomass in clastic rock and by exchangeable calcium, iron oxides, and microbial biomass in limestone. However, long-term soil tillage minimized the influences of lithology on MNC. By extrapolating the data to the three provinces of southwest China based on the land-use conversion scenario, we estimated that the existing forestation (recovery and afforestation) has the potential to increase microbial-derived carbon by 17 Tg in topsoil (0-15 cm) over limestone and 11 Tg over clastic rock. The lithology-dependent drivers of microbialderived carbon accumulation and stability should be considered to predict soil carbon dynamics and minimize carbon emissions under changing environments.
      原文链接:
    • NSTL
    • Elsevier

    Initial soil formation by biocrusts: Nitrogen demand and clay protection control microbial necromass accrual and recycling

    Wang, BaorongHuang, YimeiLi, NaYao, Hongjia...
    13页
    查看更多>>摘要：Microbial biomass is increasingly considered to be the main source of organic carbon (C) sequestration in soils. Quantitative information on the contribution of microbial necromass to soil organic carbon (SOC) formation and the factors driving necromass accumulation, decomposition and stabilization during the initial soil formation in biological crusts (biocrusts) is absent. To address this knowledge gap, we investigated the composition of microbial necromass and its contributions to SOC sequestration in a biocrust formation sequence consisting of five stages: bare sand, cyanobacteria stage, cyanobacteria-moss stage, moss-cyanobacteria stage, and moss stage on sandy parent material on the Loess Plateau. The fungal and bacterial necromass C content in soil was analyzed based on amino sugars -the cell wall biomarker. Microbial necromass was an important source of SOC, and was incorporated into the particulate and mineral-associated organic C (MAOC). Because bacteria have smaller and thinner cell wall fragments as well as more proteins than fungi, bacterial necromass mainly contributed to the MAOC pool, while fungal residues remained more in the particulate organic C (POC). MAOC pool was saturated fast with the increase of microbial necromass, and POC more rapid accumulation than MAOC suggests that the clay content was the limiting factor for stable C accumulation in this sandy soil. The necromass exceeding the MAOC stabilization level was stored in the labile POC pool (especially necromass from fungi). Activities of four enzymes (i.e., beta-1,4-glucosidase, beta-1,4-N-acetyl-glucosaminidase, leucine aminopeptidase, and alkaline phosphatase) increasing with fungal and bacterial necromass suggest that the raised activity of living microorganisms accelerated the turnover and formation of necromass. Microbial N limitation raised the production of N acquisition enzymes (e.g., beta-1,4-N-acetyl-glucosaminidase and leucine aminopeptidase) to break down necromass compounds, leading to further increase of the nutrient pool in soil solution. The decrease of microbial N limitation along the biocrusts formation chronosequence is an important factor for the necromass accumulation during initial soil development. High microbial N demands and insufficient clay protection lead to fast necromass reutilization by microorganisms and thus, result in a low necromass accumulation coefficient, that is, the ratio of microbial necromass to living microbial biomass (on average, 9.6). Consequently, microbial necromass contribution to SOC during initial soil formation by biocrust is lower (12-25%) than in fully developed soils (33%- 60%, literature data). Nitrogen (N) limitation of microorganisms and an increased ratio between N-acquiring enzyme activities and microbial N, as well as limited clay protection, resulted in a low contribution of microbial necromass to SOC by initial formation of biocrust-covered sandy soil. Summarizing, soil development leads not only to SOC accumulation, but also to increased contribution of microbial necromass to SOC, whereas the plant litter contribution decreases.
      原文链接:
    • NSTL
    • Elsevier

    Humidity and low pH boost occurrence of Onygenales fungi in soil at global scale

    Selbmann, LauraGuirado, EmilioSingh, Brajesh K.Delgado-Baquerizo, Manuel...
    6页
    查看更多>>摘要：Soils are important reservoirs for potential human pathogens and opportunistic fungi such as the dermatophyte or dimorphic fungi in the order Onygenales. In soils, these taxa are decomposers but many of them have the potential to cause respiratory and skin diseases in humans and, in some cases, systemic infections. Even so, the factors that determine the biogeography and ecology of order Onygenales remain largely undocumented. To address this knowledge gap, we surveyed members of Onygenales from topsoil fungal communities at 235 sites across six continents and provided a first global atlas. We retrieved 4.3% of the total fungal sequences (~420 Onygenales) across nine biomes ranging from deserts to tropical forests. This work advances our knowledge on the ecology and global distribution of order Onygenales and suggests the hypothesis that wet and acid soils support the larger proportions of these fungi, while their richness is constrained by aridity.
      原文链接:
    • NSTL
    • Elsevier

    Acidic amelioration of soil amendments improves soil health by impacting rhizosphere microbial assemblies

    Chen, DeleWang, XingxiangCarrion, Victor J.Yin, Shan...
    13页
    查看更多>>摘要：Intensive cultivation with accompanying nitrogen fertilization leads to soil acidification in croplands of southern China, which in turn, imperils soil health, restricting the sustainability of agricultural production. Application of soil amendments is considered as a potential method for maintaining soil health; however, the underlying soil health-promoting mechanisms are poorly understood. In the present study, we used lime, organic manure, and straw biochar, or their combinations, to treat severely acidified field plots (5 previous seasons of peanut monocropping). We analyzed the rhizosphere microbial communities, soil physicochemical properties, plant disease resistance, and plant physiological parameters at pod-bearing and pod-maturing stages of peanut. The effect of soil pH, regulated by the amendments, on the root-associated microbiome was more pronounced than the effects of other physicochemical properties. Specifically, Actinobacteria and Proteobacteria became more abundant in the rhizosphere upon the application of organic materials with lime. In vitro co-cultures of rhizosphere bacterial suspensions with a fungal pathogen revealed their enhanced disease suppression ability following treatment. Physiologically, application of organic amendments with lime promoted disease-resistance of plant roots, as determined by phenylalanine ammonia lyase and superoxide dismutase activities. The optimization of bacterial community composition in the rhizosphere played a key role in enhancing plant disease resistance, as inferred by structural equation model and network analyses. These findings suggest that the application of soil amendments reinforces disease suppression and plant physiological parameters in acidified soils by impacting microbial community assembly in the rhizosphere.
      原文链接:
    • NSTL
    • Elsevier

    Soil oxidoreductase zymography: Visualizing spatial distributions of peroxidase and phenol oxidase activities at the root-soil interface

    Guber, AndreyKravchenko, AlexandraGhaderi, NegarBlagodatskaya, Evgenia...
    11页
    查看更多>>摘要：Decomposition of organic material in the rhizosphere - the most dynamic microbial habitat in soil - involves arrays of oxidoreductase and hydrolytic enzymes. Spatial distributions of various hydrolytic activities in soil have already been explored by zymographic techniques. However, the distribution of oxidative activity in the rhizosphere remains to be studied. Thus, we extended a Time-Lapse Zymography technique, using Amplex Red (R) reagent, to visualize and quantify distributions of phenol oxidase and peroxidase activities in the rhizosphere of Zea mays L. growing in a Haplic Phaeozem and the non-rhizospheric soil. The gross oxidative activity was greatest at the root surfaces, and fell to background soil levels 1.26 and 0.73 mm from seminal (> 1 mm diameter) and lateral (< 0.5 mm diameter) roots, respectively. The rhizosphere extent relative to the root radius was 59% broader around lateral than around seminal roots. The greatest activities, up to 30 nmol cm(-2) min(-1), were peroxidase-dominated and closely associated with roots. The results confirm the utility of the approach for studying spatio-temporal distributions of oxidative activities in soil. However, actual activity of oxidoreductases in the field will be strongly controlled by fluctuating environmental conditions such as soil aeration and the gradient of reactive oxygen species, which need to be considered especially in anoxic soils.
      原文链接:
    • NSTL
    • Elsevier

    Predominant role of air warming in regulating litter decomposition in a Tibetan alpine meadow: A multi-factor global change experiment

    Ye, ChenglongWang, YingYan, XuebinGuo, Hui...
    9页
    查看更多>>摘要：Alpine ecosystems worldwide are experiencing multi-faceted climate changes, but the interactive effects of these drivers on litter decomposition are poorly understood. Here, we examined the effects of air warming, nitrogen (N) addition and altered precipitation, and their interactions on litter decomposition originating from four species (Elymus nutans, Kobresia capillifolia, Thermopsis lanceolata, Saussurea nigrescens) in a Tibetan alpine meadow. Among the three factors, air warming by open top chambers (OTCs) significantly decreased all litter decomposition except for K. capillifolia with the highest C:N ratio over one-year field decomposition. The reduced litter mass loss in the chambered plots was mainly attributed to OTC-induced decrease in soil temperature, with more negative effects of OTC on litter decomposition in winter and spring than in summer. However, N addition offset the negative effects of OTC on litter mass loss of K. capillifolia, likely by alleviating N limitation to this poor-quality litter decomposition. In addition, simulated precipitation increase promoted decomposition of high quality litter (T. lanceolata and S. nigrescens) in the dry winter, likely by alleviating water stress. Together, our findings highlight the predominant role of climate in controlling litter decomposition in alpine ecosystems.
      原文链接:
    • NSTL
    • Elsevier

    Long-term warming reduced microbial biomass but increased recent plant-derived C in microbes of a subarctic grassland

    Verbrigghe, NielMeeran, KathiravanBahn, MichaelCanarini, Alberto...
    10页
    查看更多>>摘要：Long-term soil warming and nitrogen (N) availability have been shown to affect microbial biomass and com-munity composition. Altered assimilation patterns of recent plant-derived C and changes in soil C stocks following warming as well as increased N availability are critical in mediating the direction and magnitude of these community shifts. A C-13 pulse labelling experiment was done on a warming gradient in an Icelandic grassland (Sigurdsson et al., 2016), to investigate the role of recent plant-derived C and warming on the mi-crobial community structure and size. We observed an overall increase of microbial C-13 (e.g., root-exudate) uptake, while warming led to significant microbial biomass loss in all microbial groups. The increase of mi-crobial C-13 uptake with warming differed between microbial groups: an increase was only observed in the general and Gram-positive bacterial phospholipid fatty acid (PLFA) markers and in the PLFA and neutral lipid fatty acid (NLFA) markers of arbuscular mycorrhizal fungi (AMF). Nitrogen addition of 50 kg ha(-1) y(-1) for two years had no effect on the microbial uptake, microbial biomass or community composition, indicating that microbes were not N limited, and no plant-mediated N addition effects occurred. Additionally, we show that both warming and soil C depletion were responsible for the microbial biomass loss. Soil warming caused stronger loss in microbial groups with higher C-13 uptake. In our experiment, warming caused a general reduction of microbial biomass, despite a relative increase in microbial C-13 uptake, and altered microbial community composition. The warming effects on microbial biomass and community composition were partly mediated through soil C depletion with warming and changes in recent plant-derived C uptake patterns of the microbial community.
      原文链接:
    • NSTL
    • Elsevier

    Kinetics of arsenic and antimony reduction and oxidation in peatlands treating mining-affected waters: Effects of microbes, temperature, and carbon substrate

    Kujala, KatharinaLaamanen, TiinaKhan, Uzair AkbarBesold, Johannes...
    11页
    查看更多>>摘要：Arsenic (As) and antimony (Sb) from mining-affected waters are efficiently removed in two treatment peatlands (TPs) in Northern Finland. However, the exact mechanisms behind this removal are not well resolved. Thus, the present study combines results from microcosm experiments and pilot-scale TPs on the effects of microbes, temperature, and carbon substrate to elucidate the role of peat microorganisms in As and Sb removal. The main As and Sb species in TP inflow water are arsenate and antimonate. In peat microcosms, they were quantitatively reduced, however, at rates about 20-400 times lower than previously reported from pure cultures, likely due to excess of other terminal electron acceptors, such as nitrate and sulfate. Addition of the microbial inhibitor sodium azide inhibited reduction, indicating that it is indeed microbially mediated. Arsenite and antimonite (re) oxidation, which is in situ likely limited to upper, oxic peat layers, was likewise observed in peat microcosms. Only for antimonite, oxidation also occurred abiotically, likely catalyzed by humic acids or metals. Process rates increased with increasing temperature, but all processes occurred also at low temperatures. Monitoring of pilot scale TPs revealed only minor effects of winter conditions (i.e., low temperature and freezing) on arsenic and antimony removal. Formation of methylated oxyarsenates was observed to increase As mobility at the onset of freezing. From different carbon substrates tested, lactate slightly enhanced arsenate reduction and antimonate reduction was stimulated by acetate, lactate, and formate. However, a maximum rate enhancement of only 1.8 times indicates that carbon substrate availability is not the rate-limiting factor in microbial arsenate or antimonate reduction. The collective data indicate that microorganisms catalyze reduction and (re)oxidation of As and Sb species in the TPs, and even though temperature is a major factor controlling microbial As and Sb reduction/ (re)oxidation, low inflow concentrations, long water residence times, and the presence of unfrozen peat in lower layers allow for efficient removal also under winter conditions.
      原文链接:
    • NSTL
    • Elsevier

    Ecoenzymatic stoichiometry can reflect microbial resource limitation, substrate quality, or both in forest soils

    Vesterdal, LarsSchmidt, Inger KappelRousk, JohannesZheng, Haifeng...
    10页
    查看更多>>摘要：Many studies have used the relative activities of extracellular enzymes associated with microbial carbon (C), nitrogen (N) and phosphorus (P) acquisition to infer the relative C vs. nutrient limitation of the microbial community. However, recent experimental and theoretical evidence has shown that the use of ecoenzymatic ratio to infer limiting microbial resources may be invalid. We added the two contrasting leaf litters ash (Fraxinus excelsior L., relatively more labile and nutrient rich) and oak (Quercus robur L.), into samples of mineral soils to validate the use of ecoenzymatic stoichiometry to reflect microbial resource limitation. The litter treatments were also combined with N and P addition treatments to push microbial communities toward stronger C limi-tation. The microbial resource limitations were examined in all treatments by the responses in microbial respiration, bacterial and fungal growth, microbial community composition, and by detecting the responses of microbial growth to factorial C and nutrient additions in short-term limiting factor assays (LFAs). High ratios of 8-1,4-glucosidase (BG) to 8-1,4-N-acetylglucosaminidase (NAG) + leucine aminopeptidase (LAP) (> 2:1) con-trasted with the expected reduction in C limitation after initial litter inputs. The high ratio was mainly driven by an increase in BG activity associated with high energy supply and high microbial rates of metabolism induced by added labile C substrates. During the later incubation period (7-56 days), decreasing respiration and bacterial and fungal growth rates reflected increased microbial C limitation in all treatments. An increasing BG/(NAG + LAP) ratio was in line with increasing microbial C limitation in the ash treatment where cellulose dominated as microbial C source, but a decreasing BG/(NAG + LAP) ratio was inconsistent with the temporal dynamics in microbial C limitation in the oak treatment where substrates other than cellulose (i.e., microbial necromass and lignin) dominated as C source late in the incubation. The increased BG/(NAG + LAP) ratio was in line with intensified microbial C limitation by NP addition, which was mainly due to the stimulated BG activity. In the oak and litter plus NP treatments, fungal growth was stimulated and NAG -an enzyme targeting amino sugars -was increased, presumably to meet the fungal C demand by utilizing microbial necromass -partly consisting of amino sugar polymers. Taken together, these results suggest that variation in substrate quality, availability and how these matched the present microbial energy allocation strategy and resource allocation to enzyme production caused a substantial variation in the BG/(NAG + LAP) ratio, thereby disconnecting the ratio from unambiguously reflecting the microbial resource limitation.
      原文链接:
    • NSTL
    • Elsevier

    Different stochastic processes regulate bacterial and fungal community assembly in estuarine wetland soils

    Huang, LaibinBai, JunhongWang, JunjingZhang, Guangliang...
    11页
    查看更多>>摘要：The long-standing challenge in microbial ecology is to quantify the relative importance of deterministic and stochastic processes in controlling the community structures through space and time. Deterministic processes are important when the environmental selection and species interactions are strong, whereas stochastic processes may dominate when there is large number of neutral births, death, speciation of microorganism. The existing studies are still lacking in understanding how these two processes structure microbial communities in an ecosystem whose environmental gradients change sharply at a very short geographic scale, such as in the fresh saltwater transition zone. Here, we investigated the bacterial and fungal assembly processes in topsoil (0-10 cm) in a wetland transect with fresh-saltwater transition zone in the Yellow River Estuary, China, by calculating beta mean-nearest taxon distance (beta MNTD), beta nearest taxon index (beta NTI) and Raup-Crick index. We found that stochastic processes primarily shaped the two communities. The bacterial assembly was controlled by homogenizing dispersal and dispersal limitation within and across the wetland transect, respectively. The fungal assembly, on the other hand, was mostly regulated by undominated processes, which are processes induced by weak selection/dispersal, diversification, and drift. Dispersal limitation had more pronounced effects on the bacterial diversity and cooccurrence in comparison with the effects of undominated processes on the fungal community. Nevertheless, environmental factors, such as pH, salinity and C/N, explained ~30% (p < 0.01) of compositional variations with more explanatory power for bacteria than fungi. Our study highlights the different types of stochastic processes in regulating bacterial and fungal communities along the short natural environmental gradients.
      原文链接:
    • NSTL
    • Elsevier