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"SOIL MICROORGANISMS"
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Plant root growth, architecture and function
Without roots there would be no rhizosphere and no rhizodeposition to fuel microbial activity. Although micro-organisms may view roots merely as a source of carbon supply this belies the fascinating complexity and diversity of root systems that occurs despite their common function. Here, we examine the physiological and genetic determinants of root growth and the complex, yet varied and flexible, root architecture that results. The main functions of root systems are also explored including how roots cope with nutrient acquisition from the heterogeneous soil environment and their ability to form mutualistic associations with key soil micro-organisms (such as nitrogen fixing bacteria and mycorrhizal fungi) to aid them in their quest for nutrients. Finally, some key biotic and abiotic constraints on root development and function in the soil environment are examined and some of the adaptations roots have evolved to counter such stresses discussed.
Journal Article
Meena and the Microbiome
\"When Meena wonders about the microbes in the soil and everywhere, her scientist mom answers questions while they garden, gather vegetables, eat a snack and have a bath, in a book that includes a resource list and an author's note\"-- Provided by publisher.
CHILDBOOK
Soil aggregate stability increase is strongly related to fungal community succession along an abandoned agricultural field chronosequence in the Bolivian Altiplano
1. Soil aggregate stability is an important ecosystem property which deteriorates overtime due to agricultural practices. The cessation of cultivation allows the potential recovery of soil aggregate binding agents such as soil micro-organisms and biochemical properties. Consequently, an increase in soil aggregate stability is expected. However, this outcome is difficult to predict because the response of each individual soil component and its contribution to soil stability varies. 2. This study utilized a chronosequence of 12 ex-arable fields in the Bolivian Altiplano, representing six soil ages of abandonment after cessation of potato cultivation, to examine whether soil aggregate stability increases after abandonment and the extent to which changes in soil bacterial and fungal community composition and soil chemical properties are involved in stability recovery. 3. Fields with the longest time since disturbance (15 and 20 years) have a greater proportion of water-stable aggregates than more recently abandoned fields (1 and 3 years) and exhibit larger differences in bacterial and fungal composition. Total N, ${\\mathrm{N}\\mathrm{H}}_{4}^{+}$, C and organic matter also increased with time since the last intensive agricultural practice. 4. Water-stable aggregates were strongly correlated with soil fungal community composition. Analysis of covariance is also consistent with the soil fungal community being an important mediator of the recovery of aggregate stability. 5. Synthesis and applications. Soil aggregate stability increased by 50% over the 20 years following disturbance. This recovery was associated with shifts in soil fungal community composition, as is consistent with fungal mediation of this recovery. Land management strategies focusing on restoration of the soil fungal community may enhance soil aggregate stability, a key aspect for soil conservation, restoration, sustainability of agroecosystems and erosion prevention.
Journal Article
Soil Acidification Under Long-Term N Addition Decreases the Diversity of Soil Bacteria and Fungi and Changes Their Community Composition in a Semiarid Grassland
Soil microorganisms play key roles in terrestrial biogeochemical cycles and ecosystem functions. However, few studies address how long-term nitrogen (N) addition gradients impact soil bacterial and fungal diversity and community composition simultaneously. Here, we investigated soil bacterial and fungal diversity and community composition based on a long-term (17 years) N addition gradient experiment (six levels: 0, 2, 4, 8, 16, 32 gN m
−2
year
−1
) in temperate grassland, using the high-throughput Illumina MiSeq sequencing. Results showed that both soil bacterial and fungal alpha diversity responded nonlinearly to the N input gradient and reduced drastically when the N addition rate reached 32 g N m
−2
year
−1
. The relative abundance of soil bacterial phyla
Proteobacteria
increased and
Acidobacteria
decreased significantly with increasing N level. In addition, the relative abundance of bacterial functional groups associated with aerobic ammonia oxidation, aerobic nitrite oxidation, nitrification, respiration of sulfate and sulfur compounds, and chitinolysis significantly decreased under the highest N addition treatment. For soil fungi, the relative abundance of
Ascomycota
increased linearly along the N enrichment gradient. These results suggest that changes in soil microbial community composition under elevated N do not always support the copiotrophic-oligotrophic hypothesis, and some certain functional bacteria would not simply be controlled by soil nutrients. Further analysis illustrated that reduced soil pH under N addition was the main factor driving variations in soil microbial diversity and community structure in this grassland. Our findings highlight the consistently nonlinear responses of soil bacterial and fungal diversity to increasing N input and the significant effects of soil acidification on soil microbial communities, which can be helpful for the prediction of underground ecosystem processes in light of future rising N deposition.
Journal Article
Plant-Soil-Microorganism Interactions: Heritable Relationship between Plant Genotype and Associated Soil Microorganisms
Although soil microbial communities are known to play crucial roles in the cycling of nutrients in forest ecosystems and can vary by plant species, how microorganisms respond to the subtle gradients of plant genetic variation is just beginning to be appreciated. Using a model Populus system in a common garden with replicated clones of known genotypes, we evaluated microbial biomass and community composition as quantitative traits. Two main patterns emerged. (1) Plant genotype influenced microbial biomass nitrogen in soils under replicated genotypes of Populus angustifolia, F₁, and backcross hybrids, but not P. fremontii. Genotype explained up to 78% of the variation in microbial biomass as indicated by broad-sense heritability estimates (i.e., clonal repeatability). A second estimate of microbial biomass (total phospholipid fatty acid) was more conservative and showed significant genotype effects in P. angustifolia and backcross hybrids. (2) Plant genotype significantly influenced microbial community composition, explaining up to 70% of the variation in community composition within P. angustifolia genotypes alone. These findings suggest that variation in above- and belowground traits of individual plant genotypes can alter soil microbial dynamics, and suggests that further investigations of the evolutionary implications of genetic feedbacks are warranted.
Journal Article
Effects of earthworms on the performance of Lolium multiflorum, soil properties and microbial communities in its root-zone soil under cadmium stress
Background and aims
Phytoremediation is an environment friendly, sustainable, and aesthetically pleasing technology for remediating heavy metal polluted soil. Earthworms are ubiquitous macrofauna in the soil ecosystem that play an important role in maintaining soil health and fertility. However, the understanding of earthworms' effect on phytoremediation remains limited.
Methods
In a greenhouse experiment,
Lolium multiflorum
was subjected to three levels of cadmium (0, 20, or 100 mg kg
−1
) fully crossed with two levels of earthworm treatments (i.e., with or without
Eisenia foetida
Savigny).
Results
Plant growth was inhibited while the root-shoot ratio and nitrogen accumulation in shoots were increased under 100 mg kg
−1
cadmium. Earthworms interacted with cadmium level to affect the total phosphorus content in soil. Furthermore, earthworms enriched specific microorganisms and significantly influenced bacterial communities under 0 and 20 mg kg
−1
cadmium. We observed a significant enrichment of specific microbial species in cadmium polluted soil when earthworms were present. Earthworms’ presence increased the sensitivity of fungal communities in soils polluted with cadmium.
Conclusions
Both earthworms and cadmium had certain impacts on the growth of plants, soil properties and microbial communities in root-zone soil. Moreover, the results suggest that earthworms may alleviate some negative effects of cadmium on soil microorganisms. The findings highlight the effect of earthworm on plant performance, soil properties, and root-zone microbial communities under cadmium stress, providing valuable insights into its role in phytoremediation of soils polluted with metals.
Journal Article
Effects of the dual inoculation of dark septate endophytes and Trichoderma koningiopsis on blueberry growth and rhizosphere soil microorganisms
Abstract
Blueberry is a shallow root plant in which the absorption of nutrients is inefficient, resulting in slow growth under artificial cultivation conditions. Endophytes play an important role in promoting plant growth; however, the effects of Trichoderma spp. and dark septate endophytes (DSEs) on host plant growth and soil microorganisms are still debatable. We isolated two endophytic fungal species, Trichoderma koningiopsis (TK) and a DSE (Amesia nigricolor; AN), from blueberry roots, which can solubilize insoluble phosphorus and produce amylase and cellulase to promote plant growth. We found that under dual inoculation, the colonization rate and colonization intensity of TK were higher than they were under single inoculation with TK, while the colonization rate and colonization intensity of AN were lower under dual inoculation than under single inoculation with AN. The plant nutrients, root activity, available potassium, and parts of soil phosphatase activities were highest under dual inoculation. TK inoculation resulted in the highest diversity and richness in the soil fungi and bacteria, followed by dual inoculation. The abundance of Ascomycota, Acidobacteriae, Firmicutes, and Actinobacteriota increased significantly, resulting in Trichoderma and Vicinamibacteria inoculated with TK, Chaetomium and Alicyclobacillales inoculated with AN, and Hypocreales and Burkholderiaceae with dual inoculation enriched in the soil.
Single or dual inoculation of blueberry plants with Trichoderma koningiopsis and dark septate endophytes and investigated the changes of single or dual inoculation on blueberry growth, soil physicochemical properties, and the rhizosphere microbial community of soil, which the results clarify the effects of beneficial endophytic fungi on blueberry plants.
Journal Article
Impact of various intercropping modes on soil quality, microbial communities, yield and quality of Platycodon grandiflorum (Jacq.) A. DC
Introduction
Intercropping has the function of promoting plant growth, improving yield and quality.
Platycodon grandiflorus
(
P. grandiflorus
) is a traditional Chinese medicinal herb; continuous cropping obstacles significantly inhibit its yield and quality. However, few study have established about
P. grandiflorus
interaction of various crops. This study provides a theoretical foundation to explore the most effective intercropping method, enhance soil utilization efficiency, and increase the yield and quality of
P. grandiflorus
. We conducted field experiment,
P. grandiflorus
monoculture (JG-JG),
P. grandiflorus
and
Achyranthes bidentata
intercropping (JG-NX),
P. grandiflorus
and
Saposhnikovia divaricata
intercropping (JG-FF),
P. grandiflorus
and
Glehnia littoralis
(JG-SS) intercropping. Additionally, we included three main intercropping crops with
P. grandiflorus
,
Zea mays
(JG-YM),
Setaria italica
(JG-GZ), and
Glycine max
(JG-DD). The soil physicochemical properties, enzyme activity, soil microorganisms, the yield and secondary metabolite content in the roots of
P. grandiflorus
were determined. The results showed that intercropping significantly increased the yield and quality of
P. grandiflorus
, and significantly reduced the incidence rate of root rot. The intercropping system enhances the physical and chemical properties of soil, soil enzyme activity, and soil microbial diversity. JG-SS intercropping significantly increased the abundance of bacteria and fungi, stimulated soil microbial communities, promoted plant growth, significantly increased yield and content of platycodin D, enhanced the complexity of microbial co-occurrence networks. This study could provide a sustainable planting system for the cultivation of
P. grandiflorus
, particularly the system JG-SS.
Clinical trial number
Not applicable.
Journal Article
Effects of crop rotation and continuous cropping on soil microbial community structure at different stages of tobacco
To explore the effects of crop rotation and continuous cropping on the microbial community in tobacco-planting soil at different stages and to clarify whether continuous cropping-induced microbial community imbalance can be alleviated by precise fertilization, providing a basis for improving tobacco yields and mitigating diseases. An experiment was set up in Wangqing County, Jilin Province, with two treatments: 1 - year maize - tobacco rotation (R) and 2 - year tobacco continuous cropping (C). Soil samples were collected at the cluster, peak, and maturity stages. Soil nutrients were measured and high-throughput sequencing was used to analyze the rhizosphere microbial community structure. Proteobacteria and Acidobacteria were dominant in the cluster stage. Continuous-cropping soil had a higher C.
viruginosa
abundance, and its microbial community was mainly driven by pH, whereas crop-rotation soil was affected by nutrients. During the peak period, the rotation soil had a higher abundance of actinomycetes and fibrinobacteria. At maturity, the rotation soil had higher actinomycetes and floatycomycetes abundances. Crop rotation increased Acidobacteria and decreased Bacteroidetes. Continuous cropping and crop rotation significantly affected the soil microbial community structure in tobacco-planting rhizosphere soils. The differences in the distribution of different bacteria reflect their adaptability to soil nutrients and pH, providing a scientific basis for optimizing tobacco planting patterns.
Journal Article