Mixed broad-leaved trees are particularly effective in addressing ecological issues such as soil degradation and biodiversity loss caused by the dense planting of Chinese fir. Understanding the changes in soil bacterial communities in fir–broadleaf mixed forests as a function of fir retention density may offer new insights for optimizing management practices and enhancing the ecological functions of the underground components of forest ecosystems. In this study, the diversity and composition of soil bacterial communities in mixed Cunninghamia lanceolata and Betula luminifera forests (CFBFs) with diverse retention densities of Chinese fir (1250, 1560, and 1690 trees/hm²) were analyzed. The results suggested that the soil characteristics and microbial communities’ diversity and structure are significantly influenced by the retention densities of Chinese fir in CFBFs. At the aggregate scale, the CFBFs with a retention density of 1560 trees/hm² presented the greatest soil bacterial community diversity (based on the Chao 1 (3562.75) and Shannon indices (6.58)), and the diversity and richness of soil bacteria initially increase and then decrease as the retention density decreases. In CFBFs, regardless of the retention density, bacterial communities in soil were mainly composed of Acidobacteria, Proteobacteria, and Planctomycetes. The relative abundance of soil Acidobacteria first elevated and afterwards decreased as the retention density decreased, with the highest levels (47.15%) observed in the stand with 1560 trees/hm² of Chinese fir. The Principal Coordinates Analysis (PCoA) showed that the soil microbial community structure in CFBEs with a retention density of 1560 trees/hm² is significantly different from CFBEs with a retention density of 1260, and 1690 trees/hm². Moreover, with different retention densities of Chinese fir, soil organic C, total N concentrations, and soil pH also significantly affected the diversity and composition of CFBF soil bacterial communities. Our results show that the choice of retention densities significantly influences soil microbial diversity and composition in CFBFs. Optimal retention densities (1560 trees/hm²) of Chinese fir in CFBFs can maximize bacterial diversity and stability, providing management guidance for thinning for sustainable management of the soil microenvironment of CFBFs.

In the subtropical mountainous area of Huangshan, China, 81 Torreya grandis were selected for research on growth and element distribution, with the aim of providing empirical and theoretical support for the promotion and management of T. grandis. Seven growth equations were constructed for tree height (H) and diameter at breast height (DBH) in age levels 40–2000. The most suitable Korf equation was selected by comparing the R-squared values. With R-squared values of 0.93 and 0.80, the equations H = 33.98 × Exp(−53.56/age^0.84) and DBH = 158.48 × Exp(−21.41/age^0.55) fit T. grandis growth best, respectively. The results show that T. grandis growth was relatively rapid before the age of 45 and then slowed. Among the carbon (C), nitrogen (N), and phosphorus (P) elements found in different T. grandis organs of the same age, the roots had the lowest C content, the leaves had the highest N content, and the branches had the lowest P content. The roots had the highest C:N and C:P, and the leaves had the highest N:P. The amount of N in the leaves and P in the branches both increased significantly with age, and the N:P ratio indicates that considering only one organ may not accurately indicate T. grandis nutrient limitations.

Chloranthus spicatus is one of the main scented tea varieties cultivated mainly in the Huangshan region, and dried flowers of these plants are mainly used for imparting a characteristic aroma to the tea. However, climatic variations in Huangshan limit its cultivation, with water deficit (WD) being the main limiting factor. The present study evaluated the effects of different WD intensities on the growth and physiological parameters of C. spicatus seedlings to determine the optimal soil moisture content for their large-scale cultivation. The experimental design comprised a control group (95–100%) and three treatment groups, namely mild WD (75–80%), moderate WD (55–60%), and severe WD (35–40%). Each treatment lasted 45 days and was given to 10 potted C. spicatus seedlings, with 3 replicates. Measurements were conducted for the shoot length and diameter; biomass; photosynthesis parameter; activities of antioxidant enzymes, namely superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT); and soluble protein (SP) and malonylaldehyde (MDA) contents of the seedlings. The results indicated that mild and moderate WD positively affected C. spicatus seedlings in terms of shoot length, diameter, biomass, root/shoot ratio, photosynthesis rate, intercellular CO₂ concentration, water use efficiency, and carboxylation efficiency. Moreover, the growth and photosynthesis were increased in the mild and moderate WD seedlings but decreased in the severe WD seedlings. Mild and moderate WD also led to a significant decrease in the antioxidant enzyme activities and the MDA content of seedlings (p < 0.05), all of which exhibited higher levels in severe WD seedlings. These results indicated that severe water stress restricted the growth of seedlings, while mild and moderate stress proved beneficial. SP content of the seedlings increased under mild and moderate WD but decreased under severe WD. We infer that the strong hydrophilicity of SPs in the seedlings results in the accumulation of water in plant cells, thus conferring resistance to drought stress. In conclusion, reducing the soil moisture content by 55–80% in the Huangshan region may be a promising strategy for boosting its cultivation.

Background: Biochar is being explored for pest management, but its potential as a subterranean termite bait and its mechanism of action on the gut symbiont community are poorly understood. Methods: We fed Coptotermes formosanus workers a diet of pine wood powder containing 0%, 5%, or 20% (w/w) rice-straw biochar. We then measured feeding preference, body weight, mortality, and analyzed changes in the hindgut flagellate community, bacterial 16S rRNA gene profiles, and host transcriptomics. Results: The 5% biochar diet did not deter feeding, whereas 20% reduced intake by ~18.75%. Both doses were associated with significant, time- and dose-dependent reductions in body weight and survival. The three major cellulolytic flagellate species (Holomastigotoides mirabile, Pseudotrichonympha grassii, Spirotrichonympha leidyi) declined sharply, coinciding with a restructuring of the bacterial community, notably a decrease in nitrogen-fixing Dysgonomonadaceae and an increase in opportunistic taxa. Host transcriptomics revealed exploratory, dose-dependent trends from anabolic growth toward catabolic stress and detoxification pathways, including upregulation of the proteasome and downregulation of ribosomal and energy metabolism pathways; several of these enrichment signals did not remain significant after multiple-testing correction and are therefore treated as hypothesis-generating. Conclusions: Our data are consistent with a proposed cascade hypothesis in which biochar ingestion is associated with disruption of essential gut flagellates, subsequent restructuring of bacterial symbiosis, and host metabolic stress. However, these links are inferred from parallel measurements and require continuous causal and rescue experiments for confirmation. Reduced intake at 20% and unmeasured biochar physicochemical properties remain alternative or non-exclusive explanations. Low-dose, non-deterrent biochar formulations represent candidate multi-mode active ingredients for termite bait development.