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Elevated nitrogen (N) deposition may stimulate a plant's dependency on arbuscular mycorrhizal (AM) fungi in phosphorus (P)-deficient subtropical forests. However, the ecological assembly processes and the responses of AM fungal diversity and community structure to N deposition in both the roots and rhizosphere are still unclear. We collected root and soil samples from a Cunninghamia lanceolata plantation forest after four years of N addition and examined the community structure and assembly of AM fungi. Elevated N deposition decreased the AM fungal community diversity in both rhizosphere soil and roots. Glomeraceae was the dominant family of the AM fungal community in both soil and roots across all N addition treatments, followed by Gigasporaceae and Ambisporaceae. However, N addition induced differential variation in the community composition of AM fungi between soil and roots. For soil AM fungi, N addition decreased the Glomeraceae abundance and increased the Gigasporaceae and Ambisporaceae abundance. In contrast, the root AM fungal community was dominated by Glomeraceae under N addition treatments. Furthermore, N addition increased the deterministic community assembly that acted as an environmental filter for soil AM fungi. In contrast, N addition decreased the importance of determinism, implying that the selection of plants on root AM fungi decreased with increasing N addition. Altogether, our findings suggest that the community structure of AM fungi responds differently to N deposition in the soil and roots in subtropical forests and highlight the important role of soil AM fungi in helping host plants respond to N deposition. [ABSTRACT FROM AUTHOR]

Vegetation restoration is assumed to enhance carbon (C) sequestration in terrestrial ecosystems, where plant producers and microbial decomposers play key roles in soil C cycling. However, it is not clear how the nutrient limitation patterns of plants and soil microbes might change during vegetation restoration. We investigated the nutrient limitations of the plant and microbial communities along a natural vegetation restoration chronosequence (1, 8, 16, 31, and 50 years) following farmland abandonment in Qinling Mountains, China, and assessed their relationships with soil factors. The result showed that following natural vegetation restoration, the nitrogen (N) limitation of plant and microbial communities was alleviated significantly, and thereafter, it began to shift to phosphorus (P) limitation at a later stage. Plants showed P limitation 50 years after restoration, while microbial P limitation appeared 31 years later. The changes in plant nutrient limitation were consistent with those in microbial nutrient limitation, but soil microbes were limited by P earlier than plants. Random forest model and partial least squares path modeling revealed that soil nutrient stoichiometry, especially soil C:N ratio, explained more variations in plant and microbial nutrient limitation. Our study demonstrates that the imbalanced soil C:N ratio may determine the soil microbial metabolic limitation and further mediate the variation in plant nutrient limitation during natural vegetation restoration, which provides important insights into the link between metabolic limitation for microbes and nutrient limitation for plants during vegetation restoration to improve our understanding of soil C turnover in temperate forest ecosystems. [ABSTRACT FROM AUTHOR]

In the southernmost part of coast of China, two height forms of Spartina alterniflora, tall and short, have invaded Leizhou Peninsula within the last decade. However, the effect of different height forms of Spartina alterniflora on plant-microbe interaction has not been clarified. Here, the community structures of rhizosphere bacteria and the abundance of N- and S-cycling functional genes associated with selected S. alterniflora were investigated in the field and a common garden. The community structure of tall-form S. alterniflora was distinct from short-form S. alterniflora at OTU level in the field, even after transplantation into a common garden. The abundance of bacterial amoA, nirS, and nosZ in tall S. alterniflora was significantly greater than those in short S. alterniflora in the field; however, this difference disappeared in a 1-year common garden experiment. These results suggested that compared with the tall-form S. alterniflora, the rhizosphere of short-form S. alterniflora harbored fewer nitrification-denitrification related microorganisms, which might benefit from conserving N in an N limited habitat. Together, our results suggested that tall- and short-form S. alterniflora can host their specific rhizosphere microbial communities and had different strategies of N usage via selecting the composition of rhizosphere bacterial assemblages, which in turn might determine the growth and invasiveness of S. alterniflora in its introduced range. [ABSTRACT FROM AUTHOR]

Aims: Ecological forest succession can be influenced by plant-plant interactions that exert contrasting effects on early- and late-successional species. In this study, we explored the role of indirect plant-plant interactions and the underlying microbial mechanisms in forest succession.Methods: In a mesocosm experiment, we used Schima superba, a widespread mid-successional species in subtropical China, as a model species to explore how inoculating the rhizosphere soil of Schima affected the performances of two early-successional species (Pinus massoniana and Rhodomyrtus tomentosa) and two late-successional species (Cryptocarya chinensis and Machilus chinensis). All direct and indirect correlations between plant performance and soil microbial composition were examined using partial least square path models.Results: Schima inoculum inhibited the growth of the early-successional species but had little effect on the growth of the late-successional species. Inoculation reduced non-arbuscular mycorrhizal fungi (non-AMF) colonization in both species groups but increased arbuscular mycorrhizal fungi (AMF) colonization in the late-successional species. The percentage of root lesions in the early-successional species increased with inoculation, while that in the late-successional species decreased. Plant nutrient acquisition was not responsive to inoculation. According to the path models, soil microbes explained 51% of the growth variances in the early-successional species but barely explained any growth variances in the late species.Conclusions: Schima may increase the competitive advantage of the late-successional species over early-successional species by inhibiting the mutualistic association between non-AMF and the latter, which in turn may facilitate forest succession. [ABSTRACT FROM AUTHOR]

[Display omitted] • Resource distribution trend of slope was reversed by enhanced rhizosphere effects. • Rhizosphere microbial P limitation was mainly aggravated by litter C:P imbalance. • P co-utilization by plants and microbes was derived from rhizosphere processes. • Slope position promoted P co-utilization by regulating rhizosphere effects. Phosphorus (P) limitation hinders ecological restoration in vulnerable ecosystems, particularly in forest ecosystems with severe soil erosion. Slope position and rhizosphere effect (RE) are two critical drivers of biological P utilization, but their unknown potential interaction limits the improvement of ecological restoration under P limitation. To bridge this gap, we investigated the interaction on plant–microbe P utilization by quantifying the REs at different slope positions (top, middle, and bottom) of a typical artificial forest on the Loess Plateau, China. The results showed that: (1) most of the positive REs increased by 1.5 to 5.6 times with decreasing slope position, which reversed the resource distribution trend along the slope. (2) Due to nutrient competition, plant and microbial P limitation exhibited contrasting patterns across the slope, both of which were aggravated by the RE on soil nitrogen (N)-P imbalance and litter carbon (C):P imbalance, respectively. (3) Conversely, plant P resorption and the rhizosphere process of microbial P utilization had a synergistic relationship to achieve P co-utilization in the plant–soil–microbe system. (4) The decreasing slope position promoted this P co-utilization by regulating the REs on resource quantities and resource imbalances. Overall, our findings highlight the importance of rhizosphere processes and the mediation of slope position in biological P utilization, further revealing that the rhizosphere-linked synergism of P utilization by plants and microbes may counteract the adverse consequences of P limitation on ecological restoration. [ABSTRACT FROM AUTHOR]

• The N threshold of the unimodal response of CH 4 uptake was ∼10 g N m−2 yr−1. • The critical N addition rate to +/- abundance of pmoA gene was ∼7.0 g N m−2 yr−1. • N -induced changes in the plant community affect pmoA gene abundance through rhizospheric effects. Methane (CH 4) uptake in dryland ecosystems is a pathway in mitigating atmospheric CH 4 concentrations. A number of studies have demonstrated that nitrogen availability is a key regulator of the CH 4 oxidation process. However, how plants mediate soil CH 4 oxidation in response to N addition, particularly in saline-alkaline grasslands in the vast regions of the northern China, has received little attention. We conducted a 3-yr (2017–2019) in-situ experiment with eight N addition levels to examine the effect of N on soil CH 4 oxidation, and to explore the linkages between the N -induced changes of plant community and the seasonal dynamics of CH 4 in a saline-alkaline grassland. We found that the saline-alkaline grassland was a weak CH 4 sink displaying nonlinear CH 4 uptake levels in response to N additions, possibly due to the nonlinear changes in the abundance of key functional genes (pmoA) that were responsible for CH 4 oxidation. The changes in plant productivity and diversity that were induced by N additions explained 21 % of the variations in CH 4 uptake. The N -induced increase in productivity indirectly enhanced CH 4 uptake at N addition rates of <10 g m−2 yr−1, while the decrease in biodiversity indirectly inhibited CH 4 uptake when N addition exceeded 10 g m−2 yr−1. The N -induced changes in the plant community can affect CH 4 uptake, mainly through the rhizospheric effects of plants. In conclusion, our findings underscore the importance of rhizosphere when assessing the CH 4 uptake in saline-alkaline grassland ecosystems. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is a critical macronutrient that is essential for many life-sustaining processes. Despite decades of work on plant performance under P deficiency and the importance of microbes in ecosystem processes, little is known about how bacterial and fungal flora respond to P gradients and determine the vegetation health. In current study, we examined soil edaphic conditions and microbial communities in 39 untouched natural forests representing phosphorous deficient (Pp) and phosphorus rich (Pr) soils (due to naturally occurring phosphate rocks) in Yunnan Province, China. We also considered the effect of plant functional types by including the dominant tree species. Bacterial and fungal diversity was greater across the Pp sites compared with Pr sites. The relative abundance of Actinobacteria and Gemmatimonadetes was higher across Pp sites, while Chlamydiae and Verrucomicrobia showed the opposite pattern, with greater relative abundance across the Pr sites. Bacterial taxa that were observed in low P soils were more likely having oligotrophic life history strategies. Interestingly, ectomycorrhizal (ECM) fungal diversity was promoted in the Pp sites, indicating that the decreasing soil P concentration and the increasing host P demand foster stimulated the ECM species for hyphal soil exploration. Moreover, the high P level caused saprophytic fungi (SAP) to diverge, causing its enrichment only under Q. variabilis compared to low P soil, where there is no difference in relative abundance of SAP between the two tree species. This likely resulted in an enhanced decomposition process by SAP and elevation of soil properties (Carbon and Nitrogen) under Q. variabilis across the Pr sites. Taken together, our findings highlight the highly diverse microbiome in low P soils. The higher soil P caused shifts of fungal functional guilds, which likely influence tree growth and health (ECM), along with divergence of ecosystem services between tree functional types., Competing Interests: Declaration of competing interest The authors declare that there is no conflict of interest to claim., (Copyright © 2021 Elsevier B.V. All rights reserved.)