Soil fungi often operate through diverse functional guilds, and play critical roles in driving soil nutrient cycling, organic matter decomposition and the health of above-ground vegetation. However, fungal functional guilds at the early-stage restoration of disrupted subalpine forest soils remain elusive. In the present study, we collected 36 soil samples along an altitudinal gradient (2900 m a.s.l., 3102 m a.s.l., and 3194 m a.s.l.) from cut slopes (CS) (from Wenma highway) and natural soils (NS) at the Miyaluo of Lixian County, Southwest China. By applying nuclear ribosomal internal transcribed spacer (ITS) sequencing, this study revealed the ecological characteristics of fungal functional guild in the early-stage restoration of cut slope soils. The results showed that the predicted prevalence of ectomycorrhizal fungi decreased, while plant pathogens and arbuscular mycorrhizal fungi increased in CS. In the high-altitude regions (3102 m a.s.l. and 3194 m a.s.l.), the differences in communities between natural and cut slope soils were more pronounced for total soil fungi, soil saprotroph, litter saprotroph, arbuscular mycorrhizal fungi and ectomycorrhizal fungi, in contrast to the low altitude communities (2900 m a.s.l.). An opposite pattern was evident for plant pathogens. Variations in the differences of both soil properties (mainly soil pH) and community assembling processes (e.g., heterogeneous selection, dispersal limitation and drift) between natural and cut slope soils across the altitudinal gradient likely shaped the shifting patterns of community difference. This study provides valuable insights for devising restoration approaches for cut slopes in subalpine forest ecosystems, emphasizing the importance of taking soil fungal functional guilds into account in evaluating the restoration of cut slopes, and underscoring the necessity for increased attention to the restoration of soil fungi in cut slopes at the high-altitude ecosystems.

Abundant and rare bacteria exhibit unequal responses to environmental changes and disturbances, potentially resulting in differential contributions to the altitudinal characteristics of total community in natural and disturbed soils. Although the altitude patterns of soil bacteria have been widely studied, it remains unclear whether these patterns are consistent among bacteria with varying predominance levels, and which subpopulation contributes more to maintaining these patterns in natural and disturbed subalpine forest soils. In this study, we collected 18 natural subalpine forest soil samples and 18 disturbed ones from three altitudes (2900 m a.s.l., 3102 m a.s.l., and 3194 m a.s.l.) along the Wenma highway in Miyaluo, Lixian, Sichuan, Southwest China. By partitioning total bacterial communities based on species predominance, we found that bacteria with higher predominance levels tended to exhibit altitude patterns (α-diversity, community structure, and functional redundancy) similar to those of total bacteria in both natural and disturbed subalpine forest soils, although they only occupied a small portion of the community. Abundant bacteria might play critical roles in maintaining the regional ecological characteristics of total community across the altitude gradient, while the rare and hyper-rare ones might contribute more to local diversity and functional redundancy. In natural soils, the altitude patterns of α-diversity inferred from total, abundant, and rare bacteria were mainly shaped by ${\mathrm{NO}}_3^{-}$-N, while soil conductivity mainly drove the altitude patterns of α-diversity inferred from hyper-rare bacteria. Additionally, the community structures of total, abundant, rare, and hyper-rare bacteria were mainly shaped by ${\mathrm{NO}}_3^{-}$-N, while the altitude patterns of functional redundancy inferred from total, abundant, and rare bacteria were mainly shaped by soil conductivity in natural soils. In disturbed subalpine forest soils, the influences of ${\mathrm{NO}}_3^{-}$-N for the altitude patterns of α-diversity and community structure, and those of soil conductivity for functional redundancy, were relatively weak in total, abundant, rare, and hyper-rare bacteria. This study examined the roles of bacteria with varying predominance levels in maintaining the altitude pattern of bacteria in both natural and disturbed subalpine forest soils, providing novel insights for devising strategies to conserve biodiversity and ecologically restore disturbed soils in subalpine ecosystems.

Autotrophic carbon-fixing microbes can assimilate atmospheric carbon dioxide into biomass via the Calvin–Benson–Bassham (CBB) cycle (their primary carbon fixation pathway), thereby reinforcing soil carbon sequestration in the plantation ecosystem; however, the succession of RubisCO-harboring microbial communities across stand ages remains poorly understood. Here, we investigated the community succession of microbes carrying the gene encoding RubisCO, a key enzyme in the CBB cycle, across a stand-age chronosequence in a Picea asperata plantation ecosystem. Our results revealed a progressive decrease in microbial α-diversity and a significant restructuring of community composition with increasing stand age, characterized by an enrichment of Proteobacteria and a concomitant depletion of Actinobacteria. While the Shannon–Wiener index was most strongly correlated with soil total nitrogen content, redundancy analysis identified soil pH as the predominant environmental driver of community turnover, a relationship that was found to be threshold-dependent, with substantial community shifts occurring in response to pH variations of 0.5 to 1.0 units. These findings suggest that sustaining the diversity of RubisCO-harboring microbes in older stands—a process potentially enhanced by soil nitrogen management—provides a viable strategy for augmenting the carbon sequestration capacity of managed forests through targeted microbiome regulation.

Subalpine forests provide crucial ecosystem services and are increasingly threatened by human alterations like bare-cut slopes from highway construction. External soil spray seeding (ESSS) is often employed to restore these slopes, but the cement it introduces can negatively affect soil fungi, which are vital for the ecological sustainability of restored slopes. Despite previous extensive discussions about ESSS-restored slopes, fungal dynamics and their underlying ecological mechanisms during ESSS-based restorations still remain elusive. Here, we conducted a 196-day simulation experiment using natural soils from a subalpine forest ecosystem. By using nuclear ribosomal internal transcribed spacer (ITS) sequencing, we revealed soil fungal dynamics and their ecological mechanisms during simulated ESSS-based restorations. Results showed a decline in fungal α-diversity and significant shifts in community structures from the initial day to day 46, followed by relative stabilities. These dynamics were mainly characterized by ectomycorrhizal, plant pathogenic, and saprotrophic fungi, with ectomycorrhizal fungi being depleted, while saprotrophic and pathogenic fungi showed enrichment over time. Shifts in nitrate nitrogen (${\mathrm{NO}}_3^{-}$−N) content primarily regulated these dynamics via mediating homogeneous selections. High ${\mathrm{NO}}_3^{-}$−N levels at later stages (days 46 to 196, especially day 46) might exclude those poorly adapted fungal species, resulting in great diversity loss and community shifts. Despite reduced homogeneous selections and ${\mathrm{NO}}_3^{-}$−N levels after day 46, fungal communities did not show a recovery but continued to undergo changes compared to their initial states, suggesting the less resilient of fungi during ESSS-based restorations. This study highlights the need to manage soil ${\mathrm{NO}}_3^{-}$−N levels for fungal communities during ESSS-based restorations. It provides novel insights for maintaining the ecological sustainability of ESSS-restored slopes and seeking new restoration strategies for cut slopes caused by infrastructure in subalpine forests.

Canopy gaps can result in abiotic heterogeneities and diverse niches from gap borders to centers, potentially affecting fine root decompositions mediated by soil fungal communities. Despite extensive discussions on the relationship between soil fungi and fine root decomposition, the mechanism by which gap locations regulate fine root decomposition through the soil fungal community remains elusive. Here, we conducted an in situ field decomposition experiment of Chinese Toon (Toona sinensis) fine roots in a low-efficiency weeping cypress (Cupressus funebris) plantation forest across three microhabitats: gap centers, gap borders, and closed canopy areas. Soil fungal communities were determined using internal transcribed spacer (ITS) sequencing after two years of field incubation. Results showed that soil properties and nutrient content in residual roots varied across the three microhabitats, with the gap borders exhibiting the highest decomposition rates. While fungal α-diversity remained relatively consistent, taxonomic compositions differed significantly. Decomposition rates did not show significant correlations with soil properties, observed fungal ASVs, or overall community composition. However, they positively correlated with the relative abundance of saprotrophic Sordariomycetes, which in turn positively correlated with soil total nitrogen (with a highest correlation), peaking at the gap borders. Overall community variations were primarily driven by soil temperature and magnesium content in residual roots. Further analysis revealed high fungal community similarities and low dispersal limitations between the gap borders and closed canopy areas, with more phylogenetically clustered communities at the borders. These results demonstrate that the gap borders possess a high decomposition rate, likely due to the centralization of functions driven by soil fungi such as saprotrophs existing in the “microbial seed bank” or migrating from closed canopy areas. These findings highlight the key role of soil fungi, especially saprotrophic fungi, in fine root decomposition at the gap borders, stressing the importance of soil fungi-driven mechanisms in nutrient cycling, and also informing sustainable forest management practices.

Low-temperature stress is a key environmental factor limiting the introduction and cultivation of plants native to tropical and subtropical regions; however, the molecular mechanisms governing their cold tolerance are not fully understood. In this study, we identified a core circadian rhythm gene—PiLUX—in the ornamental and medicinal plant Plumbago indica L. (P. indica) and systematically analyzed its role in the plant’s response to low temperatures. Transcriptomic analysis and physiological measurements indicated that PiLUX is significantly upregulated following cold induction; furthermore, its transcriptional levels show positive correlations with cold-tolerance-related physiological indicators such as reactive oxygen species (ROS) scavenging capacity, osmoregulatory substance accumulation, and membrane lipid peroxidation. In transgenic Arabidopsis thaliana (A. thaliana), heterologous overexpression of PiLUX enhances cold tolerance but also delays flowering, suggesting that reproductive development is sacrificed to conserve nutrients for cold tolerance. VIGS experiments confirmed that PiLUX knockdown exacerbates oxidative damage in P. indica under cold stress and reduces its recovery ability. The experimental results and transcriptomic data suggest that PiLUX may participate in the low-temperature response downstream of, or in parallel with, the CBF pathway; however, direct regulatory evidence is still required. This study provides insights into the adaptation strategies of thermophilic plants under low-temperature stress and offers a theoretical basis and genetic resources for cold-tolerance breeding in P. indica.