A widely used veterinary antibiotic tylosin is associated with a fast increase in the prevalence of genes for macrolide resistance. Therefore, there are growing concerns of its potentially adverse effects on natural ecosystems, and a study on the sorption of tylosin is an important step in this direction. As a weak base, prior studies pointed out that cation exchange was the main sorption mechanism for tylosin in soil, and minerals were important factors in influencing the sorption. However, the ionic effect on the tylosin sorption process on minerals has not been systematically conducted. In this study, the sorption of tylosin on pure clay minerals was investigated in different ionic strength solutions. Moreover, the interlayer interaction of tylosin on different types of montmorillonite was preliminarily studied. All of the sorption data were fitted with the Langmuir–Freundlich–Hill sorption model. The results showed that the variation tendency of tylosin sorption capacity on montmorillonite and kaolinite were nearly the same. The sorption capacity of tylosin at different ionic strengths decreased with the order: 0.008 M > 0.051 M > 0.108 M > 0.508 M. In different ion solutions, the sorption capacity of tylosin decreased in the following order: K⁺ > Na⁺ > Ca²⁺ Mg²⁺. However, the sorption of tylosin on montmorillonite at low initial concentration of tylosin displayed a different tendency. When the initial concentration of tylosin was low, its sorption capacities on montmorillonite at different ionic strengths decreased with the order: 0.051 M 0.108 M > 0.008 M > 0.508 M. For different ionic solutions, the sorption of tylosin decreased in the order of Mg²⁺ Ca²⁺ > K⁺ > Na⁺. The cation effect on tylosin sorption in the interlayers of montmorillonite was also investigated. The sorption of tylosin on different montmorillonites decreased in the order of Ca-montmorillonite > Na-montmorillonite > K-montmorillonite. These indicated that the hydration of inorganic ions influenced the sorption of tylosin. The results provide a more comprehensive understanding about the sorption of tylosin on minerals.

Functional diversity is considered a key link between ecosystem functions and biodiversity, and forms the basis for making community diversity conservation strategies. Here, we chose a subtropical forest community in China as the research object, which is unique in that other regions of the world at the same latitude have almost no vegetation cover. We measured 17 functional traits of 100 plant species and calculated seven different functional diversity indices, based on functional richness, evenness, and divergence. We found that most functional diversity and species diversity indices significantly differed with plant habit. There was a significant positive correlation among functional richness indices. However, functional divergence indices, multidimensional functional divergence (FDiv), and Rao’s quadratic entropy index (RaoQ) were significantly negatively correlated, and RaoQ and functional divergence indices (FDis) were uncorrelated. The correlations between three types (richness, evenness, and divergence) of functional diversity indices and three species diversity indices were different. Lineage regression results generally showed that three functional richness indices (Average distance of functional traits (MFAD), Functional volume (FRic) and Posteriori functional group richness (FGR)) were increased with three species diversity indices (species richness (S), Shannon-Wiener index (H) and Pielou index (E)). The functional evenness index (FEve) decreased with species richness (S), Shannon-Wiener index (H) and increased with species evenness (Pielou index (E)), but the change trends were small. All three types of functional diversity indices declined with altitude, although altitude had a weak influence on them. Other environmental factors affected the functional diversity of the community. Here, soil total phosphorus (TP) was the most critical environmental factor and the convex had the least effect on functional diversity in our subtropical forest community. These results will contribute to our understanding of functional diversity in subtropical forests, and provide a basis for biodiversity conservation in this region.