Schima superba is a precious broadleaf tree species that produces excellent timber. Analyzing the radial variation of wood anatomical properties within stems and determining the boundary between the juvenile and mature wood can provide a theoretical basis for the breeding and cultivation of S. superba. Herein, 30 54-year-old trees were used to analyze the radial variation of wood anatomical properties qualitatively. The correlation among wood properties was analyzed. On this basis, four types of model were used to predict the wood properties quantitatively, and the optimal segmentation model was used to determine the boundary between juvenile and mature wood. The results showed that the variation of the early stage (before the 20th year) was larger than that of the later stage (after the 20th year); moreover, the variation of the vessel features (9.56%) was greater than that of the fiber features (7.42%), the vessel lumen diameter (11.94%) and the fiber length (8.00%) had the most variation. There were three radial variation patterns in the wood properties. In the early stage, there was a significant positive correlation between the ring width and wood air-dry density (0.78) and wood basic density (0.89), and a significant negative correlation between the ring width and the fiber characters (−0.79~−0.93) and vessel characters (−0.64~−0.90). The growth models of Logistic and Richards were more suitable (R² = 84.2%~95.2%) for the radial variation of wood anatomical properties than the nonlinear least square model (R² = 67.7%~90.9%). The transition wood between juvenile and mature wood of S. superba was from the 11th to the 16th year based on aggregative indicators from the pith to bark at breast height. Finally, when taken together, the wood anatomical properties of S. superba had regular radial variation. Breeding programs need to consider both growth and wood anatomical properties in the early stage, but they can be neglected in the mature stage. The formation of mature wood of S. superba occurred after the 16th year.

The subtropical region of China possesses abundant broad-leaf tree species resources; however, the anatomical properties and microstructure of the wood are still unclear, which restricts the processing and utilization of wood. In this study, 14 broad-leaf trees and four coniferous trees were selected. Wood anatomical indices and wood microanatomy were used to evaluate the wood properties using a comprehensive index method. The results have shown that Dalbergia assamica exhibited the highest wood basic density among the 14 broad-leaved tree species, accompanied by a significant fiber proportion and vessel lumen diameter but a small vessel proportion and a high number of wood rays. Conversely, Parakmeria lotungensis and Michelia chapensis had relatively low wood basic densities, rendering them less suitable as valuable broad-leaved wood sources. Altingia chinensis, Castanopsis kawakamii, and the remaining 11 tree species exhibited medium-level wood basic densities. The 14 broad-leaved tree species had medium-length fibers. Phoebe bournei, Dalbergia assamica, and Castanopsis kawakamii demonstrated relatively high fiber proportion. Altingia chinensis, Dalbergia assamica, and Castanopsis kawakamii exhibited a large number of wood rays, making their wood more susceptible to cracking, whereas other broad-leaved tree species possessed fewer wood rays. The findings have provided a scientific basis for the exploration of precious broad-leaved tree resources and wood use.

Calcium (Ca) is an essential plant nutrient and cell signal element, but in the cultivation of container seedlings, the regulatory effect of Ca on seedling nitrogen nutrition and its regulatory mechanism have been neglected. Ectomycorrhizal fungi (ECMF) inoculation is widely used in forest container seedling cultivation. Thus, we added a certain amount of Ca to the culture matrix to determine how the cooperation between Ca and ECMF improves the nitrogen nutrition of Pinus massoniana ectomycorrhizal (ECM) container seedlings. We found that addition Ca significantly increased the relative abundance of Actinomycetota and Bacillota in the rhizosphere of ECM seedlings. These enriched bacteria cooperated with the ECMF and significantly enhanced extracellular enzyme NAG and LAP secretion. Meanwhile, adding Ca promoted the microbial nitrogen cycle in the ECM seedlings rhizosphere, and the relative abundances of nitrogen fixation genes (nifD, nifH, nifK) and the dissimilatory nitrate reduction gene (narH) significantly increased. In addition, Ca promoted the infection of ECMF on seedlings and induced the sprouting of absorptive roots with larger diameter (0.5 mm < RD ≤ 2.0 mm), i.e., ECM seedlings adopted a dual strategy of enhancing mycorrhizal symbiosis and improving root absorption area to obtain soil nitrogen. These effects contributed to an increase in microbial biomass nitrogen (MBN) and seedling nitrogen content by 20.65% and 54.38%, respectively. The results provide an effective method and theoretical reference for improving the quality of container seedlings and increasing the ECM plantations early productivity.

Sulfur application can enhance plant tolerance to toxic metal stress, but the underlying physiological and microecological mechanisms in woody plants remain poorly understood. In this study, Salix chaenomeloides was treated with sulfur nanoparticles (S NPs) at dosages of 60 and 120 mg kg−1 under cadmium (Cd) stress. We evaluated the in planta physiological responses and rhizosphere microbial processes mediating Cd tolerance and phytoremediation efficiency. S application (sulfate and S NPs) significantly stimulated Salix growth, increasing above-ground and root biomass by 15.2–28.6% and 26.9–49.5%, respectively, compared with Cd alone treatment. Notably, S NPs outperformed sulfate in alleviating Cd-induced oxidative damage, reducing malondialdehyde and superoxide anion contents by 22.4–23.8% and 82.9–84.5%, respectively, compared with Cd alone. Under Cd stress, 120 mg kg−1 S NPs application significantly increased glutathione and oxidized-glutathione contents by 8.96% and 33.0%, respectively, compared with Cd alone. Sulfur NPs significantly upregulated the expression of genes involved in metal transport and sulfur metabolism. The abundance of the Cd tolerance gene czcC and sulfur transformation genes (cysH, dsrA and soxB) was significantly increased by S NPs application under Cd stress. The expression levels of functional genes linked to the S-cycle showed a noteworthy positive relationship with the translocation factor of Cd in shoots and the total accumulation of Cd. These findings demonstrate that S NPs represent a safe and sustainable strategy to enhance Cd phytoextraction and mitigate phytotoxicity in Salix.