Knots in wood have a substantial impact on both the physical and mechanical properties of derived products. It is necessary to study their effect on the mechanical properties of wood and understand the mechanisms behind the effect. The modulus of elasticity (MOE) and modulus of rupture (MOR) of specimens without knots and with knots are measured using the three-point bending test. The size and position of knots are recorded. The specimens with knots are analyzed according to failure not at knots and failure at knots. For specimens with failure at knots, they are further divided into two sub-groups, i.e., failure around knots (FK-A) or failure in knots (FK-I).

Leafy spurge (Euphorbia esula) is an important herb and potential energy source with medicinal value. Codon usage bias (CUB) is a static feature of genes and genomes that results from adaptation and selection during long-term evolution and facilitates molecular breeding in transgenic plants. Here, we used TransDecoder to identify candidate coding regions from the downloaded leafy spurge transcriptome and generate coding region annotation files based on reference genomes. The whole genome showed A/T bias, especially at terminal positions, and seven high-frequency codons were identified. We compared codon usage frequencies to identify candidate exogenous expression receptor systems for leafy spurge. The identified factors affecting leafy spurge CUB included natural selection and other factors, mutation pressure and base composition, with natural selection and other factors being dominant. The observed CUB was significantly positively correlated with the gene expression levels. Systematic analysis of whole-genome leafy spurge revealed that highly expressed protein-coding genes presented greater CUB than did less expressed protein-coding genes. Furthermore, the highly expressed genes tended to have terminal G/C bases. In summary, we conducted a series of related studies based on the leafy spurge whole-genome sequence and laid a foundation for selecting suitable exogenous expression receptor systems and improving gene expression levels.

This study aimed to address soil land degradation caused by long-term monoculture in Chinese fir plantation forests in southern China. A 10-year close-to-nature transformation experiment was conducted in Cili County, Hunan Province. We systematically evaluated the vertical differentiation effects and restoration mechanisms of different "retention density–afforestation method" combinations on soil quality. The results showed that high retention density (170–180 trees/acre) significantly increased surface layer (0–10 cm) soil organic carbon content (+13.8%) and available phosphorus (AP) content (+126.7%) by enhancing litter input and rhizosphere exudates, making it the optimal strategy for the rapid recovery of surface-layer soil fertility. In contrast, low retention density (150–160 trees/acre) improved the physical structure of the subsurface layer (10–20 cm), enhancing microbial phosphorus cycling (microbial biomass phosphorus, +34.4%) and increasing non-capillary porosity (+19.1%), thereby effectively supporting the ecological functions of the mid-layer soil. Mixed afforestation with Phoebe zhennan and Betula luminifera showed limited short-term improvement but activated deep-layer (20–40 cm) AP potential (+273.7%), suggesting its capacity to mobilize deep nutrient pools over medium to long terms. We developed an integrated assessment framework for soil quality based on principal component analysis and a random forest model. This framework used a comprehensive index that incorporated physical, chemical, and microbial indicators, thus identifying phosphorus supply and microbial activity as the key drivers of soil fertility restoration. This study proposed a hierarchical synergistic pathway—"retention density drives shallow restoration whereas afforestation strategies unlock deep potentials"—thereby providing both a theoretical basis and scalable transformation models for the sustainable management of subtropical plantation forest ecosystems.