The CesA proteins are key players in cellulose synthesis. Eucalyptus is well-known for cellulose synthesis, although the mechanism of cellulose synthesis is largely unknown. In this study, 11 CcCesA genes were identified by comprehensive bioinformatics analysis in Corymbia citriodora, a eucalypt species. CcCesA genes were generally conserved in each subfamily. Among them, four genes lacked a transmembrane domain in the N-terminal. We showed that genes of CesA2, 4, 5, and 8 may regulate the synthesis of secondary cell walls (SCWs) through phylogenetic trees analysis. Two pairs of segmental duplication and one pair of tandem duplication were detected in CcCesAs. Analysis of Ka/Ks ratios revealed that the duplicated genes were under negative or purifying selection. Numerous cis-acting elements related to plant hormones and light reactions were identified in the promoters of CcCesAs. Expression analysis confirmed that genes of CesA2, 4, and 8 regulate the synthesis of SCWs, and CesA8, in particular, had the highest expression compared with other genes. The results will help us understand the complexity of the CcCesAs in different diameters at breast height and provide valuable information for future functional characterization of specific genes in C. citriodora.

Understanding the effects of land use on soil structure and nutrients is important for soil and water conservation in an ecologically fragile zone. This study was carried out to examine the variability of physicochemical properties in three different land use types: abandoned land (AL), eucalyptus plantation (EP), and road lawn (RL) sites at soil depths of 0–10 and 10–20 cm in the Leizhou Peninsula, a tropical coastal ecologically fragile zone of South China. Soil physicochemical property patterns exhibited extremely significant differences among the three land uses (p < 0.001) at both soil depths. Soil nutrients, natural water content, and total porosity, from high to low, in the different land use types were RL, AL, and EP, while the bulk density, from high to low, was EP, AL, and RL. Soil total nitrogen, total phosphorus, total potassium, available potassium, exchangeable calcium, exchangeable magnesium, and natural water content exhibited significant differences (p < 0.05) among the three land use types at soil depths of 0–10 and 10–20 cm, while no significant changes were detected regarding soil organic carbon, available phosphorus, and total porosity. The correlation between physical and chemical properties at the 10–20 cm depth (R = 0.97, p < 0.001) was closer and more significant than that at the 0–10 cm depth (R = 0.95, p < 0.01). Overuse of land (EP) without a rest in the ecologically fragile zone leads to soil erosion and compaction. Compared with natural restoration (abandoned land), artificial restoration (road lawn) can improve soil nutrient and water status more quickly, but cannot modify the soil organic carbon and porosity in the short term.

Background and Aims Mangrove ecosystems are vital "blue carbon" sinks, yet their degradation threatens global carbon sequestration efforts. While forest structure influences carbon storage, the role of specific life-history stages, particularly that of seedlings, remains poorly quantified. This study aims to identify the key drivers of soil organic carbon (SOC) retention in mangroves, with a particular focus on the understudied role of seedling density. Methods We conducted a field study in a monodominant Avicennia marina forest on Techeng Isle, China, sampling along seaward-landward transects across the intertidal gradient. We measured stand structure and topsoil properties (0–20 cm), analyzing for SOC, total nitrogen (TN), total phosphorus (TP), and stoichiometric ratios (C:N:P). The relative importance of drivers was assessed using random forest regression. To uncover the underlying mechanisms, we derived proxy variables for belowground carbon input and sediment oxygen demand, which were integrated into structural equation modeling (SEM) to test causal pathways. Results From the seaward to landward fringe, the mangrove population structure shifted from declining to growing, with a significant increase in seedling density ( P < 0.001). Concurrently, the levels of SOC, TN, TP and their stoichiometric ratios increased significantly from the outer to the inner fringe ( P < 0.05). Among all predictors, seedling density emerged as the most vital for SOC, a finding substantiated by random forest analysis. Structural equation modeling demonstrated that seedling density enhances SOC primarily by promoting sediment anoxia and, to a lesser extent, by increasing root-driven carbon inputs, with the model explaining a substantial proportion of the variance (R² = 0.97). Conclusion Our findings demonstrate that mangrove population characteristics, especially seedling density, exert a stronger influence on topsoil carbon and nutrients than sediment physical properties alone. We propose high-density seedling planting as a novel and effective restoration strategy to enhance blue carbon sequestration, improve nutrient retention, and bolster ecosystem resilience against sea-level rise.

As a globally significant economic timber species, Eucalyptus hybridization plays a crucial role in germplasm improvement. However, China’ s dominant

Corymbia citriodora wood holds extensive application value; however, due to the cross-pollination nature of C. citriodora and the significant genetic varia