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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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    The path less taken: Long-term N additions slow leaf litter decomposition and favor the physical transfer pathway of soil organic matter formation

    Eastman B.A.Peterjohn W.T.Adams M.B.
    10页
    查看更多>>摘要：? 2022 Elsevier LtdUnderstanding soil organic matter (SOM) formation as a balance between soil microbial access to organic plant inputs and protection by chemical recalcitrance and mineral associations can greatly improve our projections of this important terrestrial carbon pool. However, gaps remain in our understanding of the processes controlling the formation and destabilization of SOM and how these processes are affected by persistent global changes, such as nitrogen (N) deposition. To assess how elevated N deposition influences decomposition dynamics and the fate of plant inputs in a temperate deciduous forest, we coupled a reciprocal transplant leaf litter decomposition study with an analysis of the distribution of SOM in mineral associated and particulate organic matter fractions at a long-term, whole-watershed, N fertilization experiment. Nearly 30 years of N additions slowed leaf litter decomposition rates by about 11% in the fertilized watershed, regardless of the watershed from which the initial litter was collected. An apparent consequence of the altered rates of decomposition was that the proportion of SOM in light particulate organic matter in soil from the fertilized watershed was about 40% greater than that of the reference watershed, and was positively correlated with the bulk soil carbon to nitrogen ratio. Collectively, our results suggest that N saturation in a temperate forest alters SOM formation by slowing decomposition and favoring the accumulation of particulate organic matter as opposed to microbially processed mineral associated organic matter.
      原文链接:
    • NSTL
    • Elsevier

    Phenology-dependent root bacteria enhance yield of Brassica napus

    Mamet S.D.Helgason B.L.Siciliano S.D.Lamb E.G....
    13页
    查看更多>>摘要：? 2021The plant root microbiome can enhance yield in crops, but whether this effect is due to one yield-promoting bacterial community consisting of key taxa, or multiple configurations of taxa with different traits is unclear. A changing climate and the need to reduce carbon-intensive agricultural inputs has spurred breeding programs to explore holobiont approaches to optimizing crop yields. Here we used an extensive dataset of >1300 Brassica napus (a key oilseed crop) root samples across 4 trials and 16 varieties in a novel, robust analytical pipeline to decipher the beneficial root-associated bacterial communities associated with B. napus yield performance. We found three taxonomically distinct, but phylogenetically similar communities associated with leaf development, anthesis, and seed development that were linked to crop yield performance across multiple years and sites. Here we show B. napus is associated with not one, but several phenology-dependent yield-promoting root bacterial communities that influence seed yield via different, and yet undetermined, mechanisms. Therefore, we need to consider the relationship between B. napus phenology, and holobiont community assembly and function in selecting microbiome associated traits for use in breeding programs.
      原文链接:
    • NSTL
    • Elsevier

    Polar soils exhibit distinct patterns in microbial diversity and dominant phylotypes

    Ji M.Kong W.Jia H.Zhou T....
    9页
    查看更多>>摘要：? 2022 Elsevier LtdThe polar regions, comprising the Antarctic, Arctic and Tibetan Plateau, represent the most extreme environments on Earth. Soils across the polar regions harbor diverse microorganisms, which dominate the biogeochemical cycling. However, polar soil microbial diversity is largely underrepresented, and has not been directly compared with the non-polar regions at a global scale, which hinders our understanding of the potential importance of polar microbial diversity. In this study, we investigated the global microbial diversity and taxonomy by comparing 1114 soils, derived from the Antarctic (203), Arctic (432), Tibetan Plateau (104) and non-polar regions (375) across all continents. Soil microbial diversity was found to increase gradually from the Antarctic < Arctic < Tibetan Plateau and < non-polar regions. Soil microbial diversity dominantly corresponded to mean summer temperature in the polar regions and to soil pH in non-polar regions, respectively. Soil microbial community structure significantly differed across the different biogeographical regions, while the Antarctic exhibited the highest habitat-specificity. Over 26,000 phylotypes were observed across global soils, of which 21.8% were unique to the three poles, and 21.2% were apparently ubiquitous globally. Polar soils were dominated by fewer phylotypes, but individual phylotype showed greater dominance than that in non-polar regions. Our study reveals unique patterns of soil microbial diversity and taxonomic compositions in polar regions, and highlights the importance of environmental stresses in controlling soil microbial community.
      原文链接:
    • NSTL
    • Elsevier

    Testing the environmental controls of microbial nitrogen-mining induced by semi-continuous labile carbon additions in the subarctic

    Na M.Yuan M.Hicks L.C.Rousk J....
    15页
    查看更多>>摘要：? 2022 The AuthorsClimate warming and shrubification will affect soil carbon (C) cycling in arctic ecosystems. Rhizosphere inputs from increased plant productivity by shrubification may stimulate the mineralization of old soil organic matter (SOM), termed the “priming effect”. However, increased soil nitrogen (N) availability due to warming-accelerated mineralization, and litter inputs associated with shrubification could modulate this response. In this study, we investigated how N-availability affects the priming of SOM mineralization in subarctic soils by adding labile organic matter (OM) including 13C-glucose with and without mineral N, or 13C-alanine, into soils with different N availabilities resulting from inorganic N and/or litter addition field-treatments. Rather than as a single pulse addition, labile OM additions were administered semi-continuously every other day to simulate rhizosphere conditions. We found that semi-continuous additions of labile OM induced a sustained priming of SOM mineralization, and this was linked to a sustained stimulation of bacterial and fungal growth over time, despite a reduced microbial growth efficiency. The priming of soil N mineralization was higher than the priming of soil C mineralization, indicating a selective microbial N-mining that was particularly pronounced in more N-poor soils. However, microbial N-mining showed a declining trend over time, suggesting a shift from the most N-rich compounds to less N-rich compounds, presumably as reservoirs were exhausted. The priming effect controlled by N-mining was associated with a stimulation of bacterial and fungal growth depending on the form of labile OM: Alanine induced higher priming of soil C mineralization by stimulating bacterial growth, while glucose induced lower priming of soil C mineralization by stimulating fungal growth. These results indicate that bacteria and fungi can both drive the priming of SOM mineralization in subarctic soils. Based on microbial biomass and growth rates, it could be estimated that over 90% of the observed priming of both soil C and N mineralization were due to changes in turnover of “old” SOM rather than of the microbial biomass pool (i.e. “real” rather than “apparent” priming). Overall, our findings suggest that increased rhizosphere inputs could increase soil N availability by enhanced microbial N-mining, generating a positive feedback to plant productivity in the subarctic. In contrast, increased soil N availability could reduce soil C release through alleviated microbial demand for N.
      原文链接:
    • NSTL
    • Elsevier

    Soil pH influences the structure of virus communities at local and global scales

    Lee S.Nicol G.W.Hazard C.Sorensen J.W....
    5页
    查看更多>>摘要：? 2022The influence of biotic and abiotic factors on viral communities across environmental gradients in soil is relatively unknown. While soil pH strongly influences microbial community structure, it is unclear whether there is a similar influence on soil viruses. In this study, prokaryotic and viral communities were characterized in soils from a long-term pH-manipulated soil gradient (pH 4.5 and 7.5), and viral populations also compared to those of other soils ranging in pH (4.0–7.5). Viral communities were significantly influenced by pH at the local scale with 99% of viral operational taxonomic units restricted to pH 4.5 or 7.5 soil only. Analysis of viromes from six other European and North American soil systems demonstrated that a selection of viral clusters from acidic and neutral pH soils were more associated with those from the local gradient pH 4.5 or 7.5 soils, respectively. While direct pH effects on virion integrity and indirect selection via host composition were not distinguished, the results reveal that soil pH is a factor in structuring viral communities at local and global scales.
      原文链接:
    • NSTL
    • Elsevier

    Liquid scintillation counting can underestimate 14C-activity of 14CO2 trapped in NaOH

    Magid J.Bruun S.Jorgensen N.O.G.Boos E.F....
    5页
    查看更多>>摘要：? 2022 The AuthorsMineralization of organic matter in environmental samples is frequently quantified by trapping 14CO2 released from the degradation of 14C-labelled compounds. However, when 14CO2 trapped in NaOH is quantified by liquid scintillation counting, 14C-activity can be gradually lost from the scintillation vials. When combining different molarities and volumes of NaOH and five commercial scintillation cocktails, we observed in some mixtures a rapid loss in 14C-activity of up to 10% after 0.5 h and 60% after 96 h, while other mixtures showed no loss of 14C-activity for at least 96 h. The 14C-activity loss depended on molarity, volume, and CO2 saturation of NaOH, as well as the scintillation cocktail used and the mixing ratio of the two components. We show that the decline of 14C-activity may be caused by the loss of 14CO2 from the scintillation vials. The loss of 14C-activity must be prevented and therefore we provide recommendations how to accurately quantify 14C-activity of 14CO2 trapped in NaOH using liquid scintillation counting.
      原文链接:
    • NSTL
    • Elsevier

    Direction and magnitude of the change in water content between two periods influence soil respiration, microbial biomass and nutrient availability which can be modified by intermittent air-drying

    Marschner P.Zheng B.
    12页
    查看更多>>摘要：? 2022 Elsevier LtdSoil respiration and nutrient availability are influenced by soil water content and the effect of rewetting of dry soil has been studied extensively. But there are fewer systematic studies about the influence of less dramatic changes in water content on soil respiration and nutrient availability. In this study, two experiments were carried out with sandy loam soil. In both experiments, the soil was incubated at 200 g water kg?1 (W200) for two weeks which is optimal for microbial activity in this soil. Then the soil was either maintained at this water content or dried in a fan-forced oven at < 30 °C to about 10 g kg?1 (air-dried, AD), 40 g kg?1 soil (W40) or 100 g kg?1 soil (W100). Soil was maintained at these water contents for 14 days. In Experiment 1 after 14 days, soil water content was either maintained at W40, W100 or W200, reduced within 2 days or increased within a few minutes on day 16 to W40, W100 or W200 and kept at this water content for another 14 days. In Experiment 2, after the 14 days at AD, W40, W100 or W200, soil was air-dried within two days (in an oven at < 30 C°) after which soil water content was increased within a few minutes to W40, W100 or W200 and then kept at this water content for another 14 days. Soil respiration rate was measured during both 14-day periods, N and P availability and microbial biomass N and P (MBN and MBP) were determined on days 14, 23 and 30. In both experiments, respiration rate in the first 14 days and MBN on day 14 were very low in AD and increased with soil water content whereas available N was higher in AD than the other treatments. In Experiment 1, rewetting AD on day 16 induced a flush of respiration which was about 30% higher when rewet to W200 than rewetting to W100 or W40. Rewetting of W40 to W100 and W200 also induced a flush, but it was smaller than in rewetting of AD. In soil that was at W100 and W200 in the first two weeks, there was no respiration flush after day 16. In the second 2-week period, MBN on day 23 (7 days after the change in water content) was higher than on day 14 only in AD where it increased with water content in the second 2-week period. Available N was higher on day 23 than on day 14 in all treatments, 50% higher in AD and 2–3 fold higher in the other treatments. In Experiment 2 where the soil was dried to AD between day 14 and 16, irrespective of the water content in the first two weeks, rewetting to W100 and W200 induced a respiration flush which was about 30% higher in W200 than W100. The flush was smallest in soil that was at W200 in the first 14 days. MBN increased in AD and W40 treatments with a greater relative increase in AD (10-fold) than in W40 (2 fold). Available N changed little between day 14 and 23 in AD and W200, but increased about 2-fold in W40 and W100. In both experiments, differences in MBP and available P among treatments were small. In conclusion, respiration after a drying and rewetting event was influenced by the water content before drying where the respiration flush and cumulative respiration declined with increasing prior water content. Microbes in previously moist soils were more susceptible to drying and rewetting because MBN remained unchanged or decreased after rewetting. In previously dry soil on the other hand, rewetting induced not only a flush of respiration, but also an increase in MBN.
      原文链接:
    • NSTL
    • Elsevier

    Environmental filtering controls soil biodiversity in wet tropical ecosystems

    Cui H.Sun W.Delgado-Baquerizo M.Vitousek P.M....
    9页
    查看更多>>摘要：? 2022The environmental factors controlling soil biodiversity along resource gradients remain poorly understood in wet tropical ecosystems. Aboveground biodiversity is expected to be driven by changes in nutrient availability in these ecosystems, however, much less is known about the importance of nutrient availability in driving soil biodiversity. Here, we combined a cross-continental soil survey across tropical regions with a three decades' field experiment adding nitrogen (N) and phosphorus (P) (100 kg N ha?1y?1 and 100 kg P ha?1y?1) to Hawai'ian tropical forests with contrasting substrate ages (300 and 4,100,000 years) to investigate the influence of nutrient availability to explain the biodiversity of soil bacteria, fungi, protists, invertebrates and key functional genes. We found that soil biodiversity was driven by soil acidification during long-term pedogenesis and across environmental gradients, rather than by nutrient limitations. In fact, our results showed that experimental N additions caused substantial acidification in soils from Hawai'i. These declines in pH were related to large decreases in soil biodiversity from tropical ecosystems in four continents. Moreover, the microbial activity did not change in response to long-term N and P additions. We concluded that environmental filtering drives the biodiversity of multiple soil organisms, and that the acidification effects associated with N additions can further create substantial undesired net negative effects on overall soil biodiversity in naturally tropical acid soils. This knowledge is integral for the understanding and management of soil biodiversity in tropical ecosystems globally.
      原文链接:
    • NSTL
    • Elsevier

    Disentangling the impact of contrasting agricultural management practices on soil microbial communities – Importance of rare bacterial community members

    Tebbe C.C.Liu B.Arlotti D.Huyghebaert B....
    12页
    查看更多>>摘要：? 2022 The AuthorsAgriculture has a strong effect on soil microbial communities, but it is still unclear how different management practices drive their diversity and composition. To disentangle the effects of temporally contrasting crop management practices on soil microbial abundance and prokaryotic diversity, we analysed samples from a long-term agricultural field experiment, in which plant residues were exported (RE) or returned to soil, i.e., restituted (RR), over a period of 60 years. For 2.5 years, we followed a cropping sequence of maize, winter wheat and barley, in which, as an additional treatment, wheat cultivation was diversified once with pea intercropping. Based on soil-extracted DNA, abundances of bacteria, archaea and fungi were analysed by domain-specific qPCR and the diversity and composition of the prokaryotic community by 16S rRNA gene amplicon sequencing. The abundance of bacteria and fungi, but not for archaea, increased with the long-term restitution, but this effect was only detectable in spring due to their stabilized abundance during winter. The long-term effect of crop restitution on bacterial diversity became tangible when rare and dominant community members were differentiated, with higher sensitivity shown for the rare. In contrast, the cropping sequence equally affected members of both groups. The short-term effect of crop diversification by intercropping was much stronger in the C-depleted RE soils, than in RR soils where the C-loss was compensated, indicating that crop residue restitution increased the environmental resilience of soil microbial communities. Finally, we could confirm that rare bacterial community members, suspected to represent more oligotrophs and synergistic bacteria, formed stronger network structures to each other than the dominant, suspected to be more copiotrophic and competitive. Therefore, our results emphasize the importance to consider the response of rare microbial community members when evaluating long-term effects of agricultural management on the soil microbiome.
      原文链接:
    • NSTL
    • Elsevier

    Pool complexity and molecular diversity shaped topsoil organic matter accumulation following decadal forest restoration in a karst terrain

    Chen S.Feng X.Lin Q.Liu C....
    13页
    查看更多>>摘要：? 2022Fast accumulation of soil organic matter (SOM) following forest restoration shifted from cropland has been widely reported, but how the pools and molecular composition change across soil aggregate fractions remains unclear. In this study, undisturbed topsoil (0–10 cm) samples were collected across a decadal chronosequence of forest stands (RL10, RL20 and RL40) restored for 10, 20 and 40 years following maize cropland (CL) abandonment in a karst terrain of Guizhou, Southwest China. SOM changes were explored using the size and density fractionation of water-stable aggregates, 13C isotopic signalling and biomarker analyses as well as 13C solid-state NMR assays. Compared to that of CL, SOM content was increased by 24%, 79% and 181%, mass proportion of macroaggregates increased by 136%, 179% and 250%, and particulate organic matter (POM) increased by 13%, 108% and 382%, respectively at RL10, RL20 and RL40. With biomarker analyses, the relative abundances of plant-derived organics (lignin, cutin, suberin, wax and phytosterols), mostly protected in aggregates, increased, while those of microbe-derived OC, predominantly mineral bound, decreased in response to prolonged forest restoration. Calculated as per the Shannon diversity index (H’), changes in SOM pool complexity and molecular diversity were parallel to the SOM accumulation trend. The pool size ratio of POM to MAOM (mineral-associated organic matter) and the molecular abundance ratio of PL (plant-derived lipids) to ML (microbe-derived lipids) appeared to be indicative of SOM accumulation following forest restoration. With prolonged forest restoration, the topsoil OM shifted from microbial MAOM dominance to plant-derived POM dominance. Furthermore, the great topsoil OM enhancement in restored forest stands was shaped by pool complexity and molecular diversity changes with the complex interactions among plant-microbial-mineral assemblages in the karst topsoil. Both the pool complexity and molecular diversity of SOM should be considered in addressing carbon sequestration with forest restoration concerning the functioning of soil ecosystems and services under global change pressures.
      原文链接:
    • NSTL
    • Elsevier