scholarly journals Litter Quality and Microbes Explain Aggregation Differences in a Tropical Sandy Soil

2021 ◽  
Author(s):  
Moritz Laub ◽  
Samuel Schlichenmeier ◽  
Patma Vityakon ◽  
Georg Cadisch
Keyword(s):  
Sandy Soil ◽  
Litter Quality ◽  
Soil Aggregates ◽  
Temporal Variations ◽  
Bulk Soil ◽  
Seasonal Development ◽  
Aggregate Formation ◽  
Soil C ◽  
Aggregate Fraction ◽  
Medium Quality

AbstractSoil aggregates store most soil organic carbon (SOC), but how does litter quality influence their formation? We hypothesized varying litter quality to facilitate differences in aggregate formation by altering the seasonal development of microbial biomass (MB) C and N, with MB driving  aggregate development in a tropical sandy soil in Thailand. Aggregate development was studied in a long-term fallow experiment, receiving 10 Mg ha−1 annual applications of rice (Oryza sativa) straw (low N and polyphenols (PP)), groundnut (Arachis hypogaea) stover (high N, low PP), tamarind (Tamarindus indica) litter (medium N and PP), or dipterocarp (Dipterocarpus tuberculatus) leaf litter (low N, high PP) compared to a control. N-rich litter from groundnut and tamarind led to significantly higher MB, bulk soil C and aggregate C than dipterocarp, rice straw, and the control. Bulk soil C and small macroaggregates C of N-rich litter treatments increased about 7% in 30 weeks. Increasing MB N explained increasing small macroaggregate C and both, MB C or N were important covariates explaining temporal variations of C stored in the microaggregates, in silt and clay. MB also explained temporal variations of aggregate fraction weights. With time, SMA C only increased in the N-rich groundnut and tamarind treatments, but decreased in other treatments. Connections of MB to aggregate C and weight substantiated the importance of microbial activity for aggregate formation and carbon sequestration. By promoting MB for longest time spans, medium-quality tamarind could best facilitate aggregate formation, and increase silt and clay C.

scholarly journals Integrating microbial physiology and physiochemical principles in soils with the MIcrobial-MIneral Carbon Stabilization (MIMICS) model

2014 ◽  
Vol 11 (1) ◽  
pp. 1147-1185 ◽  
Author(s):  
W. R. Wieder ◽  
A. S. Grandy ◽  
C. M. Kallenbach ◽  
G. B. Bonan
Keyword(s):  
Litter Quality ◽  
Clay Content ◽  
Temperature Sensitive ◽  
Microbial Physiology ◽  
Carbon Stabilization ◽  
Physical Protection ◽  
Soil C ◽  
Substrate Quality ◽  
Functional Types ◽  
Microbial Residues

Abstract. Previous modeling efforts document divergent responses of microbial explicit soil biogeochemistry models when compared to traditional models that implicitly simulate microbial activity, particularly following environmental perturbations. However, microbial models are needed that capture current soil biogeochemical theories emphasizing the relationships between litter quality, functional differences in microbial physiology, and the physical protection of microbial byproducts in forming stable soil organic matter (SOM). To address these limitations we introduce the MIcrobial-MIneral Carbon Stabilization (MIMICS) model. In MIMICS, the turnover of litter and SOM pools are governed by temperature sensitive Michaelis–Menten kinetics and the activity of two physiologically distinct microbial functional types. The production of microbial residues through microbial turnover provides inputs to SOM pools that are considered physically or chemically protected. Soil clay content determines the physical protection of SOM in different soil environments. MIMICS adequately simulates the mean rate of leaf litter decomposition observed at a temperate and boreal forest sites, and captures observed effects of litter quality on decomposition rates. Initial results from MIMICS suggest that soil C storage can be maximized in sandy soils with low-quality litter inputs, whereas high-quality litter inputs may maximize SOM accumulation in finely textured soils that physically stabilize microbial products. Assumptions in MIMICS about the degree to which microbial functional types differ in the production, turnover, and stabilization of microbial residues provides a~mechanism by which microbial communities may influence SOM dynamics in mineral soils. Although further analyses are needed to validate model results, MIMICS allows us to begin exploring theoretical interactions between substrate quality, microbial community abundance, and the formation of stable SOM.

Soil aggregate-based nucleic acid analyses of the impact of maize roots and their root hairs on the structural diversity of microbial communities

2021 ◽  
Author(s):  
Christoph Tebbe ◽  
Damini Damini ◽  
Damien Finn ◽  
Nataliya Bilyera ◽  
Minh Ganther ◽  
...  
Keyword(s):  
16S Rrna ◽  
16S Rrna Gene ◽  
Root Hair ◽  
Soil Aggregates ◽  
Root Hairs ◽  
Soil Samples ◽  
Plant Roots ◽  
Bulk Soil ◽  
Rrna Gene ◽  
The Impact

<p>The deposition of energy rich carbon sources released by plant roots during their growth fuels microbially driven ecosystem processes in soil, but there is a lack of understanding how microorganisms interact and collaborate. The objective of this research was therefore to characterize microbial networks as they assemble under the influence of plant roots. To identify the specific importance of root hairs, we compared the impact of a maize wild-type to a root-air defective mutant (rth3; (1).</p><p>The microbial community structure was analyzed by qPCR and 16S rRNA gene amplicon sequencing from soil DNA. In order to increase the probability of detecting truly interacting microbial partners as a basis for network analyses, we first evaluated a new protocol to obtain DNA from as little as 1 mg instead of the usual 250 mg soil samples, thereby approaching the aggregate level (2). While the diversity of bacterial 16S rRNA gene amplicons of 250-mg samples taken from the same soil was not distinct, DNA analyses from individual aggregates clearly differed from each other underlining that soil aggregates represent distinct microbial habitats.</p><p>Soil column experiments with maize grown in a loam soil (3) revealed distinct communities between rhizosphere and bulk soil. The community composition of individual aggregates showed more differences in bulk soil compared to rhizosphere. Less elaborated networks were seen in bulk soil and a profound effect of root hairs could be unravelled. Null model testing demonstrated that Actinobacteria were equally important for network connectivity independent of the root hair mutation, but for networks of the wildtype, Acidobacteria were essential for synergistic interactions and overall network structure. In contrast, Proteobacteria and Firmicutes connectivity became more important. The observed differences in community composition and interactions suggests carbon cycling, and perhaps other microbially-driven functions, are markedly affected by the presence of root hairs.</p><p>Utilizing maize root soil microcosms for studying soil zymography in the rhizosphere allowed to obtain soil samples from regions with distinct specific enzyme activities. In order to enhance the detection of actively metabolizing bacterial community members, we studied rRNA sequences and compared it to rRNA gene sequences from the same samples. Currently the data are under analysis.</p><p>References</p><p>(1) Wen, T-J, Schnable PS (1994) Analyses of mutants of three genes that influence root hair development in Zea mays (Gramineae) suggest that root hairs are dispensable. Am. J. Bot. 81, 833–842.</p><p>(2) Szoboszlay M, Tebbe CC (2020) Hidden heterogeneity and co-occurrence networks of soil prokaryotic communities revealed at the scale of individual soil aggregates. Microbiol. Open, e1144. DOI: 10.1002/mbo3.1144</p><p>(3) Vetterlein D et al. (2020) Experimental platforms for the investigation of spatiotemporal patterns in the rhizosphere – laboratory and field scale. J. Plant Nutr. Soil Sci., 000, 1–16 DOI: 10.1002/jpln.202000079</p>

Contrasting impacts of manure and inorganic fertilizer applications for nine years on soil organic carbon and its labile fractions in bulk soil and soil aggregates

CATENA ◽  
2020 ◽  
Vol 194 ◽  
pp. 104739
Author(s):  
Tengteng Li ◽  
Yunlong Zhang ◽  
Shuikuan Bei ◽  
Xiaolin Li ◽  
Sabine Reinsch ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Aggregates ◽  
Inorganic Fertilizer ◽  
Bulk Soil

scholarly journals Modeling the effects of litter stoichiometry and soil mineral N availability on soil organic matter formation using CENTURY-CUE (v1.0)

2018 ◽  
Vol 11 (12) ◽  
pp. 4779-4796 ◽  
Author(s):  
Haicheng Zhang ◽  
Daniel S. Goll ◽  
Stefano Manzoni ◽  
Philippe Ciais ◽  
Bertrand Guenet ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Litter Quality ◽  
Plant Litter ◽  
Climate Mitigation ◽  
N Availability ◽  
Mineral N ◽  
Microbial Decomposition ◽  
Soil C ◽  
C Cycle

Abstract. Microbial decomposition of plant litter is a crucial process for the land carbon (C) cycle, as it directly controls the partitioning of litter C between CO2 released to the atmosphere versus the formation of new soil organic matter (SOM). Land surface models used to study the C cycle rarely considered flexibility in the decomposer C use efficiency (CUEd) defined by the fraction of decomposed litter C that is retained as SOM (as opposed to be respired). In this study, we adapted a conceptual formulation of CUEd based on assumption that litter decomposers optimally adjust their CUEd as a function of litter substrate C to nitrogen (N) stoichiometry to maximize their growth rates. This formulation was incorporated into the widely used CENTURY soil biogeochemical model and evaluated based on data from laboratory litter incubation experiments. Results indicated that the CENTURY model with new CUEd formulation was able to reproduce differences in respiration rate of litter with contrasting C : N ratios and under different levels of mineral N availability, whereas the default model with fixed CUEd could not. Using the model with flexible CUEd, we also illustrated that litter quality affected the long-term SOM formation. Litter with a small C : N ratio tended to form a larger SOM pool than litter with larger C : N ratios, as it could be more efficiently incorporated into SOM by microorganisms. This study provided a simple but effective formulation to quantify the effect of varying litter quality (N content) on SOM formation across temporal scales. Optimality theory appears to be suitable to predict complex processes of litter decomposition into soil C and to quantify how plant residues and manure can be harnessed to improve soil C sequestration for climate mitigation.

scholarly journals Abiotic and Biotic Factors Influencing the Effect of Microplastic on Soil Aggregation

Soil Systems ◽  
2019 ◽  
Vol 3 (1) ◽  
pp. 21 ◽  
Author(s):  
Anika Lehmann ◽  
Katharina Fitschen ◽  
Matthias Rillig
Keyword(s):  
Soil Structure ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Soil Aggregation ◽  
Soil Biota ◽  
Aggregate Formation ◽  
Sterile Soil ◽  
Soil Aggregate Stability ◽  
Abiotic And Biotic Factors ◽  
Positive Effect

Plastic is an anthropogenic, ubiquitous and persistent contaminant accumulating in our environment. The consequences of the presence of plastics for soils, including soil biota and the processes they drive, are largely unknown. This is particularly true for microplastic. There is only little data available on the effect of microplastics on key soil processes, including soil aggregation. Here, we investigated the consequences of polyester microfiber contamination on soil aggregation of a sandy soil under laboratory conditions. We aimed to test if the microfiber effects on soil aggregation were predominantly physical or biological. We found that soil biota addition (compared to sterile soil) had a significant positive effect on both the formation and stabilization of soil aggregates, as expected, while wet-dry cycles solely affected aggregate formation. Polyester microfiber contamination did not affect the formation and stability of aggregates. But in the presence of soil biota, microfibers reduced soil aggregate stability. Our results show that polyester microfibers have the potential to alter soil structure, and that these effects are at least partially mediated by soil biota.

The contribution of carbohydrate C and earthworm activity to the water-stable aggregation of a sandy soil

Soil Research ◽  
1997 ◽  
Vol 35 (1) ◽  
pp. 61 ◽  
Author(s):  
B. P. Degens
Keyword(s):  
Organic Matter ◽  
Sandy Soil ◽  
Bulk Soil ◽  
Organic C ◽  
Water Stable Aggregates ◽  
Incubation Study ◽  
Cast Doubt ◽  
The Stability ◽  
Water Extractable ◽  
Earthworm Activity

An incubation study was conducted to test the effects of decomposing clover tops (added at 0, 6·2 or 12·5 mg organic matter/g soil) and earthworm activity on the contribution of carbohydrate C to the stability of aggregates in a sandy soil. Soils incubated with and without earthworms were separated into surface-casts and bulk soil, and the amounts of water-stable aggregates >1 mm surviving slow and rapid rewetting (when air-dry) in these soil separates were determined. Organic C and acid- and water-extractable carbohydrate C concentrations were determined in the aggregates and bulk soil. The treatments of 6·2 and 12·5 mg organic matter/g soil increased the >1 mm aggregation of the bulk soil by more than 2·2- and 2·8-fold, respectively, compared with the non-amended soils. With the addition of earthworms, there were increases from 1·7- to 1·8-fold only in aggregates surviving slow rewetting. The acid- and water-extractable carbohydrate C contents of aggregates >1 mm in the bulk and surface-cast soils were generally not greater than the carbohydrate C in the bulk soil. Generally, the carbohydrate C fractions were also not increased in the more stable aggregates (rapidly rewet) compared with the weaker aggregates (slowly rewet). Carbohydrate C in bulk soil was generally (P < 0·05) correlated with the amounts of aggregates surviving each rewetting treatment (r > 0·71, P < 0·01). In contrast, greater amounts of carbohydrate in aggregates surviving slow rewetting were not correlated (r < -0·45, P > 0·05), with a greater proportion of these aggregates resisting disruption when the soils were rapidly rewet (except for acid-extractable carbohydrate C; r = -0·84, P < 0·05). These results cast doubt on the usefulness of correlations in assessing the contribution of carbohydrate C to aggregation. The amounts of carbohydrate materials in the soil appeared to have little influence on aggregation, probably because the location of bonding compounds in the soil pore matrix is more critical.

scholarly journals Protist diversity and community complexity in the rhizosphere of switchgrass are dynamic as plants develop

Microbiome ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Javier A. Ceja-Navarro ◽  
Yuan Wang ◽  
Daliang Ning ◽  
Abelardo Arellano ◽  
Leila Ramanculova ◽  
...  
Keyword(s):  
Community Composition ◽  
Community Assembly ◽  
Panicum Virgatum ◽  
Large Scale ◽  
Rhizosphere Soil ◽  
Bacterial Community Composition ◽  
Temporal Variations ◽  
Bulk Soil ◽  
Growth Stages ◽  
Soil System

Abstract Background Despite their widespread distribution and ecological importance, protists remain one of the least understood components of the soil and rhizosphere microbiome. Knowledge of the roles that protists play in stimulating organic matter decomposition and shaping microbiome dynamics continues to grow, but there remains a need to understand the extent to which biological and environmental factors mediate protist community assembly and dynamics. We hypothesize that protists communities are filtered by the influence of plants on their rhizosphere biological and physicochemical environment, resulting in patterns of protist diversity and composition that mirror previously observed diversity and successional dynamics in rhizosphere bacterial communities. Results We analyzed protist communities associated with the rhizosphere and bulk soil of switchgrass (SG) plants (Panicum virgatum) at different phenological stages, grown in two marginal soils as part of a large-scale field experiment. Our results reveal that the diversity of protists is lower in rhizosphere than bulk soils, and that temporal variations depend on soil properties but are less pronounced in rhizosphere soil. Patterns of significantly prevalent protists groups in the rhizosphere suggest that most protists play varied ecological roles across plant growth stages and that some plant pathogenic protists and protists with omnivorous diets reoccur over time in the rhizosphere. We found that protist co-occurrence network dynamics are more complex in the rhizosphere compared to bulk soil. A phylogenetic bin-based null model analysis showed that protists’ community assembly in our study sites is mainly controlled by homogenous selection and dispersal limitation, with stronger selection in rhizosphere than bulk soil as SG grew and senesced. Conclusions We demonstrate that environmental filtering is a dominant determinant of overall protist community properties and that at the rhizosphere level, plant control on the physical and biological environment is a critical driver of protist community composition and dynamics. Since protists are key contributors to plant nutrient availability and bacterial community composition and abundance, mapping and understanding their patterns in rhizosphere soil is foundational to understanding the ecology of the root-microbe-soil system.

Nutritive value of pasture: I. Seasonal variations in the productivity, botanical and chemical composition, and nutritive value of medium pasturage on a light sandy soil

1926 ◽  
Vol 16 (2) ◽  
pp. 205-274 ◽  
Author(s):  
Herbert Ernest Woodman ◽  
Denzil Layton Blunt ◽  
James Stewart
Keyword(s):  
Chemical Composition ◽  
Sandy Soil ◽  
Seasonal Changes ◽  
Nutritive Value ◽  
Weather Conditions ◽  
Pasture Grass ◽  
Initial Stage ◽  
Poa Trivialis ◽  
Medium Quality ◽  
Bromus Mollis

An account has been given of an investigation into the seasonal changes in the productivity, botanical and chemical composition, and nutritive value of pasture grass, the work constituting the initial stage of a comprehensive study of the nutritive properties of different types of pasture. The pasture on which the work was carried out was situated on a light sandy soil of low water-retaining capacity; the pasturage was of medium quality.Grazing was imitated by the daily use of a motor-mowing machine, the system of cutting being such as to ensure the whole plot being cut over once per week. The season was divided into ten periods, each period corresponding with the duration of a digestion trial carried out on two wether sheep. The main feature of the weather conditions during the season was the extremely low rainfall during the period from early June to mid-July.The pasture plot results were compared with corresponding results obtained from contiguous plots which were allowed to grow for hay, and from which, after removal of hay, several successive aftermath cuts were taken. The main findings of the investigation are summarised below:Seasonal changes in the botanical composition of the herbage. Although precise and systematic botanical analyses of the herbage of the pasture were not carried out, yet careful surveys made at an early and a late date in the season, together with general observations made during the whole course of the experiment, enabled interesting conclusions to be drawn in respect of the seasonal activity and persistency of the different species of grasses in the sward. During the spring season,Bromus mollis, Lolium perenne, Poa annuaandPoa trivialisaccounted for almost 80 per cent, of the herbage.

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