Eucalyptus is harvested for wood and fiber production in many tropical and sub-tropical habitats globally. Plantation has been controversial because of its influence on the surrounding environment, however, the influence of massive Eucalyptus planting on soil microbial communities is unclear. Here we applied high-throughput sequencing of the 16S rRNA gene to assess the microbial community composition and diversity of planting chronosequences, involving two, five and ten years of Eucalyptus plantation, comparing to that of secondary-forest in South China. We found that significant changes in the composition of soil bacteria occurred when the forests were converted from secondary-forest to Eucalyptus. The bacterial community structure was clearly distinct from control and five year samples after Eucalyptus was grown for 2 and 10 years, highlighting the influence of this plantation on local soil microbial communities. These groupings indicated a cycle of impact (2 and 10 year plantations) and low impact (5-year plantations) in this chronosequence of Eucalyptus plantation. Community patterns were underpinned by shifts in soil properties such as pH and phosphorus concentration. Concurrently, key soil taxonomic groups such as Actinobacteria showed abundance shifts, increasing in impacted plantations and decreasing in low impacted samples. Shifts in taxonomy were reflected in a shift in metabolic potential, including pathways for nutrient cycles such as carbon fixation, which changed in abundance over time following Eucalyptus plantation. Combined these results confirm that Eucalyptus plantation can change the community structure and diversity of soil microorganisms with strong implications for land-management and maintaining the health of these ecosystems.

BACKGROUND: Tea polysaccharide conjugate (TPC) is a naturally occurring active substance that is extracted from tea. Owing to its benefits in enhancing human immunity and antioxidant effects, TPC is widely used in culinary products. The binding mode of polysaccharides and proteins in TPC, however, has not been well studied; it may be closely related to their functional properties, especially emulsification. RESULTS:The molecular weights and monosaccharide compositions of TPC were determined by ion chromatography and highperformance gel permeation chromatography. Although the functional groups of polysaccharides and proteins were confirmed by infrared spectroscopy, the presence of proteins could not be detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis and ultraviolet spectroscopy. It was hypothesized that the hydrophobic groups of the proteins in TPC were wrapped by polysaccharide chains, thus making the proteins undetectable. The rheology and interfacial protein adsorption results show that TPC forms a viscoelastic film at the oil-water interface to prevent the aggregation of oil droplets, thereby enhancing the stability of the emulsion. Based on these structural and emulsifying properties of TPC, the binding mode of polysaccharides and proteins along with their phase behavior at the oil-water interface of the emulsion was speculated.CONCLUSION: In TPC, the hydrophilic groups of the proteins are linked to polysaccharides by covalent interactions, where the hydrophobic groups are wrapped with the polysaccharide chains with the help of hydrophobic forces to form a hydrophobic core. The unique binding of polysaccharides and proteins in TPC enhances its amphiphilic properties, which can be effectively distributed at the oil-water interface and form stable emulsions.

How plants with different sexual systems grow and distribute in the community? Are they influenced by environmental factors? The answer to these questions is helpful to understand how species diversity is shaped in the plant community. This study summarized the numerical characteristics of sexual systems and the relationship between the distribution of dioecious plants and the topographical factors. Results showed that of the 289 woody seed plants recorded in the 60 ha plot, 176 species are bisexual plants and 113 species are unisexual plants. Of the 113 unisexual species, 51 are monoecious and 62 are dioecious plants. The abundance of unisexual plants accounts for 36.2% of all individuals recorded in the whole plot. The dioecious plants account for 21.5% of all individuals recorded and 59.5% of all individuals of unisexual plants in the plot. At the 20 m × 20 m quadrat spatial scale, 31 dioecious species showed aggregated distribution. Proportion of number of dioecious species of all species showed weak and positive correlation with altitude, convex and slope, but relative abundance of dioecious plants only showed weak and positive correlation with altitude. Furthermore, three diversity indices of plant sexual system did not show significant correlation with altitude, convex and slope. In sum, dioecious plants occupy a large proportion but most