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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.

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.

To investigate the effects of different dominant species on the microbial functional diversity of vegetation concrete substrates, the rhizosphere and non-rhizosphere soils of three dominant species (Pennisetum alopecuroides (PA), Arthraxon hispidus (AH) and Pueraria lobata (PL)) of vegetation concrete were studied using the Biolog-Eco method at Xiangjiaba Hydropower Station. The results showed that the microbial activity and microbial functional diversity indices in the rhizosphere soil of the three dominant plants were significantly higher than those in the non-rhizosphere soil and that the microbial activity and functional diversity indices in the rhizosphere and non-rhizosphere soil of AH, as well as in the rhizosphere soil of PL, were at a high level. The carbon sources predominantly used by rhizosphere soil microbes were carbohydrates, amino acids and polymers, while the carbon sources predominantly used by non-rhizosphere soil microbes were carboxylic acids, amino acids and polymers. The governing elements of the carbon source metabolic features of the microbial community were the soil moisture content (WC), organic matter (OM), total nitrogen (TN), potential of hydrogen (pH), microbial carbon (MBC), microbial nitrogen (MBN) and microbial phosphorus (MBP). Based on a thorough examination of these aspects, it was concluded that vegetation had altered the microbial community structure and functional diversity of the vegetation concrete substrate, perhaps improving the overall metabolic activity. A. hispidus with high adaptability should be prioritized in the regeneration of vegetation on concrete slopes.

Marigold (Tagetes erecta L.) flowers can be used to produce lutein, but the production process generates fermentation wastewater, which is rich in lactic acid. Currently, most fermentation wastewater treatment methods are relatively expensive and time-consuming. To develop a practical marigold flower fermentation wastewater treatment method, in this study, we treated the fermentation wastewater with calcium oxide to prepare a neutralization solution, which was then used to irrigate maize that in turn exhibited a significant increase in growth. Then, we investigated soil pH, conductivity and enzyme activity, as well as microbial community and diversity of the maize rhizosphere and non-rhizosphere soil. Compared with the control group, the neutralization solution had no significant effect on soil pH and four kinds of enzyme (soil urease, catalase, sucrase and acid phosphatase) activity, but the electrical conductivity of the treatment group increased by 24.3%. The 16s rDNA and ITS rDNA sequencing results showed that the neutralization solution treatment influenced the diversity and abundance of bacteria and fungi in the non-rhizosphere samples, as well as the number of bacterial species in rhizosphere soil. The effect of neutralization solution treatment on bacteria was greater than that on fungi. Proteobacteria and Ascomycota were the predominant bacterial and fungal phyla in maize rhizosphere soil. The relative abundance of Paenibacillus, Bacillus and Penicillium genera significantly increased in non-rhizosphere soils. We hereby present a potential method for treating marigold flower fermentation wastewater for fertilizer utilization and show that the neutralization solution promotes maize growth and influences the soil microbial structure.

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.

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.

Continuous cropping obstacles severely hindered the sustained development of the ginseng industry. Among the obstacles, an imbalance of soil microbiome community was considered one of the major culprits. The fungal community is an essential part of the soil microbiome community. Extensive characterization of the fungal community composition and variation during ginseng cultivation will help us understand the mechanism underlying continuous cropping obstacles. By using a high-throughput amplicon sequencing method, the non-rhizospheric fungal community of farmland cultivated ginseng of 2 years old (C2) and 5 years old (C5), understory wild ginseng of 15 years old (W15) and 35 years old (W35), fallow fields which have been abandoned for 10 (F10) years were characterized. Farmland cultivated ginseng and understory wild ginseng harbored distinct non-rhizospheric fungal communities, and extension of cultivation periods enlarged the fungal community difference between two cultivation modes. Extended cultivation periods significantly decreased the OTU richness and PD whole tree indices, and OTU number and cultivation periods were negatively correlated. Extension of cultivation periods led to an increased abundance of pathotrophs. Still, the increased abundance of pathotrophs may not be the leading cause of severe continuous cropping obstacles in farmland cultivated ginseng. Compared with understory wild ginseng, farmland cultivated ginseng had a lower abundance of symbiotrophs and a higher abundance of saprotrophs. This changed symbiotrophs/saprotrophs ratio may have some correlation with the severe continuous cropping obstacles that occurred in farmland cultivated ginseng. Fallowing on the fungal community of the non-rhizosphere soil was generally opposite of that of extension of ginseng cultivation periods. The impacts of farmland cultivation on the fungal community of the non-rhizosphere soil can last for decades, even if the following is practiced.

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.

Thirty rhizosphere and non-rhizosphere soil samples from different infection grades(0, I, III, V and VII) of three typical banana plots(Jianfeng, Shiyuetian, Chongpo) infected by banana fusarium wilt (Fusarium oxysporum f. sp. cubense) in Hainan province were collected to study the microbial community functional diversity applying Biolog-ECO microplates technology. The results are as follows: (1) Overall carbon source metabolic capacities of soil microbial community weaken with increasing of infection grades of banana fusarium wilt. (2) Richness indices, Simpson indices, Shannon indices and McIntosh indices of soil microbial community gradually decreased with increasing of infection grades of banana fusarium wilt. (3) Principal component analysis show that metabolic characteristics of soil microbial community significantly change between the healthy plants and diseased plants in the same banana plot. The results would provide information for explaining the pathogenesis of banana fusarium wilt and controlling its incidence by applying microbial ecology to regulate soil environmental measures.

Sole-carbon-source-utilization techniques were used to evaluate the functional diversities of microorganisms in samples of arctic soil maintained at three different incubation temperatures. Samples collected from four sites were gathered from the rhizosphere and from non-rhizosphere soils. Techniques used to isolate microorganisms from samples are described. The microorganisms were then inoculated into ECO-Biolog plates and incubated at temperatures of 4, 10, and 28 degree C. Data from analyses of substrate utilization in the Biolog plates were used to compute values for Shannon-Weaver diversity and Shannon-Weaver evenness. Differences between rhizosphere and non-rhizosphere soils are described. Findings from principal component analyses of the multivariate data sets from the different soils are discussed.