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Overgrazing‐induced grassland degradation has become a serious ecological problem worldwide. The diversity and composition of soil microbial communities are sensitive to grazing disturbances. However, our understanding is limited with respect to the effects of grazing intensity on bacterial and fungal communities, especially in plant rhizosphere. Using a long‐term grazing experiment, we evaluated the diversity and composition of microbial communities in both rhizosphere and non‐rhizosphere soils under three grazing intensities (light, moderate, and heavy grazing) in a desert grassland and examined the relative roles of grazing‐induced changes in some abiotic and biotic factors in affecting the diversity and composition of microbial communities. Our results showed that soil bacteria differed greatly in diversity and composition between rhizosphere and non‐rhizosphere zones, and so did soil fungi. Moderate and heavy grazing significantly reduced the rhizosphere bacterial diversity. Grazing intensity substantially altered the bacterial composition and the fungal composition in both zones but with different mechanisms. While root nitrogen and soil nitrogen played an important role in shaping the rhizosphere bacterial composition, soil‐available phosphorus greatly affected the non‐rhizosphere bacterial composition and the fungal composition in both soils. This study provides direct experimental evidence that the diversity and composition of microbial communities were severely altered by heavy grazing on a desert grassland. Thus, to restore the grazing‐induced, degraded grasslands, we should pay more attention to the conservation of soil microbes in addition to vegetation recovery. Our study found that grazing in fragile ecosystems had a stronger effect on rhizosphere soil microorganisms than in non‐rhizosphere soil. The restoration and protection of rhizosphere microbial community should be emphasized when considering the restoration of degraded grassland.

Characterizing soil microbial community is important for forest ecosystem management and microbial utilization. The microbial community in the soil beneath Camellia oleifera , an important woody edible oil tree in China, has not been reported before. Here, we used Illumina sequencing of 16S and ITS rRNA genes to study the species diversity of microorganisms in C. oleifera forest land in South China. The results showed that the rhizosphere soil had higher physicochemical properties, enzyme activities and microbial biomass than did the non-rhizosphere soil. The rhizosphere soil microorganisms had a higher carbon source utilization capacity than the non-rhizosphere soil microorganisms, and attained the highest utilization capacity in summer. The soil microbial community of C. oleifera was characterized by rich ester and amino acid carbon sources that played major roles in the principal functional components of the community. In summer, soil microbes were abundant in species richness and very active in community function. Rhizosphere microorganisms were more diverse than non-root systems in species diversity, which was associated with soil pH, Available phosphorous (AP) and Urease (URE). These results indicated that microbial resources were rich in rhizosphere soil. A priority should be given to the rhizosphere microorganisms in the growing season in developing and utilizing soil microorganisms in C. oleifera plantation. It is possible to promote the growth of C. oleifera by changing soil microbial community, including carbon source species, pH, AP, and URE. Our findings provide valuable information to guide microbial isolation and culturing to manage C. oleifera land.

The tillage method in farming systems is essential to develop strategies to increase fertilizer uptake by plant roots and to avoid environmental pollution. The field study aimed to investigate the characteristics of nitrogen and enzyme activities in rhizosphere soil with different tillage methods. Four treatment plots applied with fertilizers were established: continuous rotary tillage (CR), plowing-rotary tillage (PR), continuous no-till (CN) and ploughing-no-till (PN). The total content of nitrogen in chernozem was high during early stages of plant growth, and then it decreased with the maize growth. In the rhizosphere soil, the total N accounted 1314.45, 1265.96, 1120.47, 1120.47, 1204.05 mg·kg−1 of CR, PR, CN, and PN, respectively, which were markedly greater than that of non-rhizosphere soil (1237.52, 1168.40, 984.51, 1106.49 mg·kg−1 of CR, PR, CN, and PN, respectively). At first growth stages, content of NH4+-N and NO3−-N in two soil regions was low, then increased gradually, which followed the order of CR < PR < PN < CN. The rhizosphere soil showed slightly higher concentration of NH4+-N and NO3−-N than non-rhizosphere. The soil enzymes were more active in the rhizosphere soil than that of non-rhizosphere during the whole maize growth stages. Due to minimal damage to the soil environment and optimal soil moisture and temperature, the urease and catalase activities were greatest in the rhizosphere for CN treatment. Therefore, CN was recommended to be used by farmers for the improvement of macronutrient availability and soil enzyme activities in the soil.

Intercropping can enable more efficient resource use and increase yield. Most current studies focus on the correlation between soil nutrients and crop yield under intercropping conditions. However, the mechanisms related to root exudates and soil nutrients remain unclear. Therefore, this study explored the correlation between rhizosphere soil nutrients and root exudates in sugarcane/peanut intercropping. Root extracts, root exudates, rhizosphere soil enzyme activities, and soil nutrients were analyzed and compared in monocultured and intercropped peanut and sugarcane at different growth stages. The root metabolites were annotated using the Kyoto Encyclopedia of Genes and Genomes pathways to further identify the connection between soil nutrients and root exudates. The effects of intercropping differed in peanut and sugarcane at different growth stages, and the difference between podding and pod-filling stages was significant. Intercropping generally had a great effect on peanut; it not only significantly increased the organic acid, soluble sugars, and phenolic acids in root exudates and extracts from peanuts, but also significantly increased rhizosphere soil enzyme activities and soil nutrient levels. Intercropping peanuts promoted fumaric acid secretion from roots and significantly affected the metabolic pathways of alanine, aspartate, and glutamate. Sugarcane/peanut intercropping can increase root exudates and effectively improve soil nutrients. The changes in soil nutrients are closely related to the effects of fumaric acid on alanine, aspartate, and glutamate metabolism.

The decline of Mongolian Scots pine (Pinus sylvestris var. mongolica) plantations in the “Three-North” shelterbelt region is closely linked to soil degradation. This study compared rhizosphere and non-rhizosphere soils across different stand ages, focusing on nutrient availability, microbial biomass, enzyme activities, and soil particle morphology. Results showed that SOC and TN accumulated with age, whereas AP, AK, and pH declined in older stands, indicating progressive acidification. Results demonstrated that SOC and TN increased with stand age, whereas AP, AK, and pH exhibited a marked decline in the older stands (stands aged ≥ 40 years), reflecting progressive acidification and nutrient depletion. Rhizosphere soils consistently displayed higher SOC, TN, microbial biomass, and enzyme activities than non-rhizosphere soils, largely driven by root exudation and enhanced microbial turnover. The increasing Cmic/Nmic ratio with age suggested a fungal-dominated microbial community, which may exacerbate stand decline by fostering pathogenic fungi. Scanning electron microscopy revealed pronounced particle fragmentation and surface roughness with increasing stand age, particularly in rhizosphere soils, indicating root-driven physical and biochemical weathering. These findings highlight the synergistic effects of stand development and rhizosphere processes on soil structure and fertility, providing a theoretical basis for the sustainable management and restoration of declining plantations.

Background and aimsIt is known that the single and combined use of phosphate-solubilizing bacteria (PSB) and silicon (Si) have the potential to improve the uptake of phosphorus (P) by plants in calcareous soils. However, it was unclear which form of Si in soil would have the most profound effects on the uptake of P by wheat plant inoculated with PSB. Here we investigated the effect of Si fertilizer on chemical forms of Si and P uptake by wheat plant inoculated with PSB in a calcareous soil. Determining different forms of Si in calcareous soils with a low P supply is essential to better understand the capacity of these forms to supply wheat plant with P in the presence of PSB.MethodsA pot trial in a completely randomized design with factorial arrangement in 3 repetitions under greenhouse conditions was adopted to investigate the effect of Si fertilizer alone or in combination with PSB on the uptake of P and Si by wheat plant grown on a calcareous soil with low available P. Experimental treatments included: Si factor at four levels of 0, 150, 300, and 600 mg Si kg−1 from silicic acid source and PSB strains factor at three levels of B0 (control), Pseudomonas sp. FA1, and Bacillus simplex UT1. The impacts of Si levels and PSB on shoot and root dry weight and the wheat shoot uptake of Si and P were measured. Also, the chemical forms of Si in wheat rhizosphere and non-rhizosphere soil and the regression models of the variables were studied to better understand the mechanisms of this process.ResultsWith increasing the levels of Si, the plant available Si with the lowest level, adsorbed Si, and amorphous Si with the highest level in both the rhizosphere and non-rhizosphere soil increased. In addition, Si fertilization-mediated increase at level of the soil Si fractions was intensified in the presence of PSB strains. The highest plant available Si (75.50 mg Si kg−1 soil) was obtained from the treatment of 600 mg Si kg−1 soil in the presence of Pseudomonas sp. FA1. The combined application of Si and PSB strains also increased the wheat shoot dry weight by 3.5 times compared to the control treatments. The use of Si alone at level of 300 mg Si kg−1 also increased the wheat shoot content of P by 2.3 times compared to the control treatment. However, the combined application of Pseudomonas sp. FA1 and Si at level of 600 mg Si kg−1 increased the wheat shoot content of P by 4 times compared to the control treatment. According to the correlations among the studied parameters, in addition to the expected positive correlation between plant available Si of wheat rhizosphere soil and the measured parameters, a positive and significant correlation between adsorbed Si of wheat rhizosphere soil and the shoot uptake of Si (r2 = 0.84, P < 0.01) and the shoot uptake of P (r2 = 0.58, P < 0.05) was also observed in this study.ConclusionsThe information on the distribution of different forms of Si and the availability of P following the combined use of PSB strains and Si in this study (e.g., the role of rhizosphere adsorbed Si in increasing the wheat shoot uptake of P) may help in better management of P-fertilization in calcareous soils.

Background and aims Soil-borne diseases are an increasingly serious threat to agriculture systems. Organic fertilization would improve soil quality and microbial community as well, and thus is appreciated a promising control strategy for soil-borne diseases. Yet, how soil microbial communities mediate disease control under organic fertilization remains largely unknown. Here, we aimed to explore the microbial mechanism of controlling soil-borne diseases by organic fertilization. Methods We investigated the effects of various fertilization regimes on the soil suppressiveness toward pathogenic fungi in the peanut rhizosphere. The fertilization regimes tested were organic fertilizer, chemical fertilizers, and a combination of both. Results Uninterrupted application of organic fertilizer in peanut field plots for seven planting seasons resulted in a control of peanut root rot, with a significantly higher peanut yield. Upon organic fertilization, bacterial microbiome assembly in the rhizosphere played a key role in developing soil suppressiveness against peanut root rot; upon chemical fertilization, the potential fungal pathogens dominated the fungal microbiome assembly in the rhizosphere to boost root rot. Further, structural equation model revealed that the rhizosphere bacterial community contributed to the control of root rot. Furthermore, upon organic fertilization, the rhizosphere bacterial community strongly suppressed mycelial growth and spore germination of Fusarium sp. ACCC 36194. Conclusions Collectively, in a monocropping system, persistent organic fertilization favors the development of a protective microbial shield in the plant rhizosphere, maintaining the rhizosphere health.

Background Dendrobium is a precious herbal that belongs to Orchidaceae and is widely used as health care traditional Chinese medicine in Asia. Although orchids are mycorrhizal plants, most research still focuses on endophytes, and there is still large amount unknown about rhizosphere microorganisms. To investigate the rhizosphere microbial community of different Dendrobium species during the maturity stage, we used high-throughput sequencing to analyze microbial community in rhizosphere soil during the maturity stage of three kinds of Dendrobium species. Results In our study, a total of 240,320 sequences and 11,179 OTUs were obtained from these three Dendrobium species. According to the analysis of OTU annotation results, different Dendrobium rhizosphere soil bacteria include 2 kingdoms, 63 phyla, 72 classes, 159 orders, 309 families, 850 genera and 663 species. Among all sequences, the dominant bacterial phyla (relative abundance > 1%) were Proteobacteria, Actinobacteria, Bacteroidetes, Acidobacteria, Firmicutes, Verrucomicrobia, Planctomycetes, Chloroflexi, and Gemmatimonadetes. And through WGCNA analysis, we found the hub flora was also belong to Acidobacteria, Actinobacteria and Proteobacteria. Conclusions We found that the rhizosphere bacterial communities of the three kinds of Dendrobium have significant differences, and that the main species of rhizosphere microorganisms of Dendrobium are concentrated in the Proteobacteria, Actinobacteria, and Bacteroidetes. Moreover, the smaller the bacterial level, the greater the difference among Dendrobium species. These results fill knowledge gaps in the rhizosphere microbial community of Dendrobium and provide a theoretical basis for the subsequent mining of microbial functions and the study of biological fertilizers.

Nitrogen (N) is the primary essential nutrient for ginseng growth, and a reasonable nitrogen application strategy is vital for maintaining the stability of soil microbial functional communities. However, how microbial-mediated functional genes involved in nitrogen cycling in the ginseng rhizosphere respond to nitrogen addition is largely unknown. In this study, metagenomic technology was used to study the effects of different nitrogen additions (N0: 0, N1: 20, N2: 40 N g/m 2 ) on the microbial community and functional nitrogen cycling genes in the rhizosphere soil of ginseng, and soil properties related to the observed changes were evaluated. The results showed that N1 significantly increased the soil nutrient content compared to N0, and the N1 ginseng yield was the highest (29.90% and 38.05% higher than of N0 and N2, respectively). N2 significantly decreased the soil NO 3 – N content (17.18 mg/kg lower than N0) and pH. This resulted in a decrease in the diversity of soil microorganisms, a decrease in beneficial bacteria, an increase in the number of pathogenic microorganisms, and an significant increase in the total abundance of denitrification, assimilatory nitrogen reduction, and dissimilatory nitrogen reduction genes, as well as the abundance of nxrA and napA genes (17.70% and 65.25% higher than N0, respectively), which are functional genes involved in nitrification that promote the soil nitrogen cycling process, and reduce the yield of ginseng. The results of the correlation analysis showed that pH was correlated with changes in the soil microbial community, and the contents of soil total nitrogen (TN), ammonium nitrogen (NH 4 + -N), and alkaline-hydrolyzed nitrogen (AHN) were the main driving factors affecting the changes in nitrogen cycling functional genes in the rhizosphere soil of ginseng. In summary, nitrogen addition affects ginseng yield through changes in soil chemistry, nitrogen cycling processes, and functional microorganisms.

PurposeThe invasive weed common ragweed (Ambrosia artemisiifolia [L.]) has become notorious in China as a major weed in agriculture. Soil microbial communities play important roles in invasive plant growth by potentially mediating nutrient cycling in soil. However, knowledge regarding the soil microbial communities in common ragweed remains limited.MethodsIn this study, a long-term field experiment was conducted to comparatively study the microbial community compositions in the rhizosphere soil of invasive common ragweed and two native plants, Chenopodium serotinum and Setaria viridis.ResultsWe found that the bacterial and fungal community compositions differed significantly between common ragweed and two native plants. Invasion by common ragweed selectively accumulated microorganisms, such as Exopiala, RB41, Cnuella, Dinghuibacter and Funneliformis, that can enhance carbon and nitrogen cycling and the absorption of phosphorus in the rhizosphere environment. Moreover, the relative abundances of these microorganisms were significantly related to the soil pH and ammonium contents. Furthermore, we found that microbial inoculants from rhizosphere of common ragweed promote growth of both common ragweed and S. viridis.ConclusionsOur results show that common ragweed constructs a unique rhizosphere microbial community that distinguishes it from local plants, which could contribute to its growth and expansion by providing a stronger ability to use carbon, nitrogen, and phosphorus. This study offers fundamental explanation to explain how the underground microbial community facilitate the invasion of common ragweed on an ecosystem-level.