Xiuwei Wang

Background and aims The maintenance of β-diversity in microbial communities is closely linked to the community assembly processes. However, the relative contributions of different assembly processes to the components of β-diversity, as well as the extent to which host plant mycorrhizal types differentially regulate these processes, remain poorly understood. Methods We investigated 20 broad-leaved tree species from a temperate natural secondary forest in China, examined the root functional traits, soil properties, and β-diversity components and assembly processes of rhizosphere soil microbial communities between arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) species. The following hypotheses were tested: (1) species turnover is the dominant component of microbial β-diversity; and (2) the magnitude of species turnover and the proportion of community assembly processes differ between AM and ECM species. Results Species turnover accounted for more than 90% of the β-diversity in both bacterial and fungal communities, supporting hypothesis 1. Bacterial communities were mainly influenced by deterministic processes (homogeneous selection); whereas fungal communities were largely shaped by stochastic processes (dispersal limitation). Mycorrhizal type had no significant effect on the β-diversity and assembly process, hypothesis 2 was not supported. Soil property variation dominates the selective filtering of bacterial communities, while plant trait variation primarily shapes fungal communities by enhancing stochastic processes, especially dispersal limitation. Conclusions In natural secondary forests, the host rhizosphere imposes similar environmental selection pressures on bacteria and restricts fungal dispersal, thereby driving high species turnover. These findings deepening the understanding of species coexistence within forest communities and the mechanisms that sustain soil biodiversity.

Background and Aims Long-term nitrogen (N) deposition profoundly influences belowground ecological processes in forests. However, it remains unclear whether plant fine-root resource acquisition strategies regulate rhizosphere microbial community responses to N addition. Methods Based on a 22-year N addition experiment, this study investigated two tree species with contrasting strategies: Larix gmelinii (larch), exhibiting a conservative "low-investment, slow-return" strategy, and Fraxinus mandshurica (ash), which adopts an acquisitive "high-investment, fast-return" strategy. We explored how fine-root resource acquisition strategies regulate rhizosphere microbial community composition, metabolic limitations, and co-occurrence networks. Results Our results showed that N addition significantly strengthened the acquisitive strategy in ash but did not alter the resource acquisition strategy of larch fine roots. In ash, this enhanced acquisitive strategy drove the enrichment of specific bacterial taxa (Acidobacteriota and Proteobacteria) and fungal taxa (Ascomycota) in the rhizosphere following N addition, whereas the microbial composition in the larch rhizosphere remained largely unchanged. Furthermore, mediated by the root resource acquisition strategy, N addition alleviated microbial carbon limitation in the ash rhizosphere and fostered more complex and stable bacterial networks. In contrast, N addition intensified microbial carbon limitation in the larch rhizosphere, simplifying its bacterial network. Conclusion This study demonstrates that plant fine-root resource acquisition strategy is a key trait governing rhizosphere microbial response to N addition. N addition disproportionately benefits the rhizosphere ecosystems of species with inherently acquisitive root strategies by enhancing their ecological stability.

Aims First-order roots in forests exhibit high productivity and turnover rates, contributing to soil carbon accumulation to an even greater extent than leaf litter. However, the factors influencing first-order root litter decomposition, particularly the role of soil microbial communities in this process, remain poorly understood. Methods We conducted a three-year litter decomposition experiment using two dominant coniferous species in northeastern China, across four locations within their natural distribution range. This study aimed to investigate the differences in decomposition patterns between leaf and first-order root litter and to elucidate the influence of soil microbial network interactions on their decomposition dynamics. Results The decomposition rate of first-order root litter (13–22% per year) was significantly lower than that of leaf litter (23–31% per year). The decomposition rates of both litter types increased with decreasing latitude. First-order root litter decomposition exhibited a "home-field disadvantage," where locally sourced first-order root litter decomposed significantly slower than non-local sources, whereas leaf litter decomposition was independent of its origin. Additionally, we found that fungal network complexity in summer was positively correlated with the decomposition rates of both litter types, whereas bacterial network complexity in autumn exhibited a negative correlation. Climatic conditions modulate soil microbial network complexity, thereby influencing litter decomposition. Conclusions These findings demonstrate that while the decomposition dynamics of first-order root and leaf litter differ, both are influenced by soil microbial network complexity. Our study highlights the distinct and seasonally dependent effects of bacterial and fungal interactions within their respective networks on litter decomposition.

Biomass allocation is a critical mechanism for understanding plant responses to environmental changes. In northeast China, mixed planting with Dahurian larch (Larix gmelinii (Rupr.) Kuzen.) enhanced the productivity of Manchurian walnut (Juglans mandshurica Maxim.) plantations. However, the mechanisms underlying biomass allocation in these systems, particularly in relation to variation in root communication level, remained unclear. To address this, a 15-month pot experiment was conducted, in which Manchurian walnut and Dahurian larch seedlings were mix-planted to examine how varying degrees of root interaction influenced the trade-off between aboveground biomass (AGB) and belowground biomass (BGB) in these two species. The experiment included four treatments: complete root separation and three levels of root communication (1 μm nylon mesh segregation, 45 μm nylon mesh segregation and full root contact). Aboveground (leaf and stem) and root biomass, nutrient content (carbon, nitrogen and phosphorus), nutrient ratios and key morphological and physiological traits of leaves and roots were measured for both species. The trade-offs between AGB and BGB were also quantified. The results revealed that root communication increased the AGB and BGB of Manchurian walnut by 39.53 and 28.81%, respectively and reduced the AGB and BGB of Dahurian larch by 59.34 and 54.45%, respectively. Root communication shifted the biomass trade-off from a biased root allocation to an aboveground allocation in Manchurian walnut, while Dahurian larch exhibited the opposite trend. These trade-offs were directly associated with aboveground carbon-to-phosphorus ratios, root nitrogen-to-phosphorus ratios, root carbon-to-phosphorus ratios, specific root surface area and mycorrhizal colonization rates. In conclusion, these results indicated that mixed planting of Manchurian walnut and Dahurian larch altered the trade-off between AGB and BGB, with the magnitude varying with the level of root communication.