Response of soil micro-food web to nutrient limitation along a subtropical forest restoration

Cascade effects of nutrient input on river microeukaryotic stability: habitat heterogeneity-driven assembly mechanisms

The assembly process and stability mechanism of microeukaryotes can reflect the health and sustainability of river ecosystems, and changes in land use types can alter biodiversity and affect ecosystem functions. Here, we used 18S rDNA amplicon sequencing technology to explore the effects of land use and dry and wet season changes on microeukaryotic species composition, community assembly, co-occurrence networks, and network stability, as well as the mechanisms driving observed changes. The total phosphorus concentration was 13.3 and 7.8 times higher and the total nitrogen concentration was 6.3 and 3.8 times higher in agricultural and urban river sections, respectively, than in forest river sections. Differences in land use types have created heterogeneity on river habitats and altered the distribution and species composition of microeukaryotes, reducing the number and diversity of endemic species in communities and simplifying the food web. High nitrogen and phosphorus inputs promoted the abundance of low-trophic-level species; ecosystem stability and population sizes were maintained by high trophic levels, which controlled the abundance of low trophic levels through predation and promoted nitrogen transformation. The high-nutrient environment reduced the niche breadth of species (>70 % dry season niche breadth contraction), thus promoting specialization; given that this placed these species at a disadvantage in the competition for resources, community stability decreased (60 %/40 % wet/dry season robustness reductions). The physical dilution effect of the river in the dry season was weakened, and the input of domestic sewage and agricultural return water promoted deterministic processes (71.43 % increased |βNTI|>2 in dry season). The environmental filtration effect in the wet season was still stronger than the physical dilution effect caused by the increase in river flow (neutral model R2 = 33.5 %). The input of large amounts of nutrients was the main driver of the decline in the stability of microeukaryotes (Total Effect = -0.62).

Adaptation strategies of the soil microbial community to stoichiometric imbalances induced by grassland management measures in the desert steppe of Northwest China

Grassland management measures strongly affect soil resources availability which can not meet microbial elemental demands, potentially resulting in stoichiometric imbalances. This limits microbial metabolic activities and nutrient cycling. However, there is still limiting understanding of the adaptation strategies of soil microbial communities to stoichiometric imbalances. We investigated soil labile resources, microbial biomass stoichiometry, extracellular enzymatic stoichiometry (EES), and microbial communities under three management measures (planting Caragana korshinskii (NTC), moderate-intensity thinning Caragana korshinskii (MTC) and grassland (GL)) in desert steppe of Northwest China, and assessed microbial metabolic limitation. Lower soil labile C:N and C:P values, and higher microbial biomass C:N and C:P values were found in NTC and MTC, leading to lower C:N and C:P imbalances. The microbial communities maintained stoichiometric homeostasis through improving the threshold elemental ratio (TER), adjusting enzymes production and extracellular enzymatic stoichiometry (EES), and increasing microbial biomass P, to store scarce nutrients (N and P), consequently alleviating N and P limitations. Stoichiometric imbalances could better explain the variation of bacterial community compared with fungal community. The C:N imbalance was closely related with bacterial and fungal communities composition and diversity. Partial least squares path modelling highlighted that grassland management measures altered microbial communities, which was directly associated with EES and indirectly associated with high TER. Overall, these results helped to better understand the response of microbial metabolic activities and communities to stoichiometric imbalances changes induced by grassland management measures in the desert steppe. And moderate-intensity thinning C. korshinskii was a promising management measure for Ningxia desert steppe.

Agricultural soil microbiomes at the climate frontier: Nutrient-mediated adaptation strategies for sustainable farming

The equilibrium transformation of soil microbial community dynamics and succession across various temporal and spatial dimensions plays a critical role in maintaining plant adaptability. Intensive agricultural practices accelerate the succession of plant microbial communities, rendering their restoration function more vulnerable. Climate change, with its variable impacts, affects the resilience of plant microbial communities through regulatory and mediating effects. Investigating the spatiotemporal dynamics of soil microbial communities in the context of climate change offers valuable insights into developing robust and resilient microbial ecosystems. This review examines the regulatory role of soil resources in plant microbial communities, the interactive effects of climate change on soil resource regulation, and the prediction of microbial community structures through resource allocation. Additionally, it explores the mechanisms that sustain ecological resilience in plant microbial community systems, emphasizing the application of the profit-averaging law.

Microbial mechanisms of mixed planting in regulating soil phosphorus availability across different stand ages in Chinese fir plantations

The mixed planting of Chinese fir with broadleaf species to increase soil phosphorus (P) availability has been widely adopted in subtropical China. As soil P availability is significantly influenced by tree growth, the microbial mechanisms underlying the effects of mixed planting on soil P availability across different stand ages are not fully understood. In this study, we collected soil samples from mixed-species plantations of Chinese fir and Schima superba (MCP) and pure Chinese fir plantations (PCP) at young (5 years), middle-aged (20 years), and mature (32 years) stages in southeastern China. We determined the soil P fractions, organic P (Po) mineralizing ability, and dynamics of the microbial community associated with Po mineralization in the samples. We hypothesized that the influence of mixed planting on soil P availability is modulated by stand age. Compared with the PCP stands, the young and mature MCP stands exhibited significantly greater contents of labile and moderately labile P, with increases of 13.22% and 8.18%, respectively, in the young stands and 22.20% and 30.52%, respectively, in the mature stands. Conversely, the middle-aged MCP stands exhibited lower contents of labile and moderately labile P, with decreases of 20.93% and 18.16%, respectively. The communities of Po-mineralizing fungi (Pmin-F) and bacteria (Pmin-B) changed not only among the different plantation types but also across the various stand ages. The Pmin-F community contributed mainly to labile P, whereas the Pmin-B community was the primary driver of moderately labile P. Additionally, mixed planting mediated labile P availability through soil pH, accounting for 71% of the variation in this P fraction. Conversely, stand age affected the availability of moderately labile P through soil nitrogen availability and the Pmin-F community, explaining 81% of the variation in this P fraction. Overall, we revealed that the impact of mixed planting on soil P availability is modulated by stand age, with fungi and bacteria fulfilling distinct ecological roles in the process. Our results are highly important for maintaining soil P availability for the sustainable management of Chinese fir plantations.

Windfarm construction alters soil multinutrient cycling by destabilizing microfauna community in a mountain ecosystem

In recent decades, investors attracted to wind power's promise of zero-emission electricity have fueled the proliferation of large windfarms across the world. However, the effects of windfarm construction with different land use subtypes (i.e., wind turbine, waste slag, and construction production and living areas) on soil microfauna community stability and subsequent consequences for ecosystem functioning remains poorly understood. Here, we evaluated how these three land use types affect soil microfauna community stability relative to natural vegetation types (forest, shrubland, and grassland) in a mountain area. We found that all three windfarm land use subtypes reduced soil multinutrient cycling and microfauna community stability compared with natural ecosystems. However, among these natural ecosystems, reductions of soil multinutrient cycling were 66.36% and 79.10% lower in grassland than in forest and shrubland, respectively. Reductions of soil nematode community stability were 62.15% and 77.22% lower in grassland than in forest and shrubland; as well as soil protist community stability were 74.01% and 56.74%, respectively. Interspecific interactions and environmental filtering jointly drove variation in soil microfauna community stability. Soil microfauna community stability was significantly and positively linked to soil multinutrient cycling, which has the potential to initiate cascading ecological consequences. Our finding implies that grasslands may be more suitable than shrublands or forests for windfarm development based on the responses of soil microfauna communities.

Anthropogenic restoration exhibits more complex and stable microbial co-occurrence patterns than natural restoration in rubber plantations

Forest restoration is an effective method for restoring degraded soil ecosystems (e.g., converting primary tropical forests into rubber monoculture plantations; RM). The effects of forest restoration on microbial community diversity and composition have been extensively studied. However, how rubber plantation-based forest restoration reshapes soil microbial communities, networks, and inner assembly mechanisms remains unclear. Here, we explored the effects of jungle rubber mixed (JRM; secondary succession and natural restoration of RM) plantation and introduction of rainforest species (AR; anthropogenic restoration established by mimicking the understory and overstory tree species of native rainforests) to RM stands on soil physico-chemical properties and microbial communities. We found that converting tropical rainforest (RF) to RM decreased soil fertility and simplified microbial composition and co-occurrence patterns, whereas the conversion of RM to JRM and AR exhibited opposite results. These changes were significantly correlated with pH, soil moisture content (SMC), and soil nutrients, suggesting that vegetation restoration can provide a favorable soil microenvironment that promotes the development of soil microorganisms. The complexity and stability of the bacterial-fungal cross-kingdom, bacterial, and fungal networks increased with JRM and AR. Bacterial community assembly was primarily governed by stochastic (78.79 %) and deterministic (59.09 %) processes in JRM and AR, respectively, whereas stochastic processes (limited dispersion) predominantly shaped fungal assembly across all forest stands. AR has more significant benefits than JRM, such as a relatively slower and natural vegetation succession with more nutritive soil conditions, microbial diversity, and complex and stable microbial networks. These results highlight the importance of sustainable forest management to restore soil biodiversity and ecosystem functions after extensive soil degradation and suggest that anthropogenic restoration can more effectively improve soil quality and microbial communities than natural restoration in degraded rubber plantations.