Enhancement of phosphorus storage capacity of sediments by coastal wetland restoration, Yellow River Delta, China.

Un-restored (R0) and restored (in 2006 (R2006) and in 2002, (R2002)) coastal wetlands were selected to study phosphorus (P) storage capacity and the risk of P loss in the Yellow River Delta (YRD). The results showed that the maximum P sorption capacity (Qmax) in the wetland sediments varied between 201.8-1168.6 mg kg-1; the average value was 576.2 mg kg-1. Qmax increased with increasing time since restoration (R2002 > R2006 > R0). The eutrophication risk index (ERI) ranged between 0.27-2.07% and decreased with increasing time since restoration, but the relationship was not statistically significant (P > 0.05). A correlation analysis demonstrated that Feox, Mg, and Alox are the main P sorption agents in wetland sediments, whereas TOC, pH, and clay particles have an important effect on P sorption and release. The analysis suggests that we should restore degraded coastal wetlands to help reduce the P load to offshore waters.

Overall supply level, not the relative supply of nitrogen and phosphorus, affects the plant community composition of a supratidal wetland in the Yellow River Delta.

Human activities have altered the environmental nitrogen (N) and phosphorus (P) supply from both aspects of overall supply level and relative supply ratio. However, the effects of the two aspects on plant community composition are still not clear. In this study, a field manipulation experiment combining 3 overall nutrient supply levels (Low, Medium and High) and 3 N:P supply ratios (5,1, 15:1 and 45:1) was conducted in a supratidal wetland in the Yellow River Delta from 2015 to 2018. The effects of the two aspects on soil properties, performance of dominant species and plant community diversity were examined. The results showed that the N:P supply ratio and overall supply level both affected the concentration of soil inorganic N and available P, and N:P ratio significantly, while only overall supply level exerted a significant effect on the importance value of the dominant species, species richness and Shannon diversity. There were big gaps in the N and P supply amounts among the treatments that having same overall supply level with different supply ratio, but the plant composition displayed no significant difference among these treatments, which suggested that P may be also very important in affecting plant community composition in the study area. The species richness and the Shannon diversity were negatively correlated with the importance value of Suaeda glauca. With the rise of overall supply level, S. glauca became increasingly dominant and suppressed other species. Compared with the control treatment, the species richness and the Shannon diversity declined significantly only at high supply level (minimum N supply amount of 26.01 g m-2 yr-1), indicated that the supratidal wetland had high resilience to nutrient enrichment. Our results revealed that the N:P supply ratio has little influence on plant composition, compared with overall supply, in relative short-term in the supratidal wetland.

[A new bibenzyl derivative from Bletilla striata].

AIM: To study the chemical constituents of Bletilla striata. METHODS: Various column chromatographies with silica gel and Sephadex LH-20 were employed for the isolation and purification. The structures of the compounds were elucidated on the basis of spectral analyses and chemical methods. RESULTS: Three compounds were isolated from the roots of Bletilla striata (Thunb.) Reichb. f. and identified as 5-hydroxy-4-(p-hydroxybenzyl)-3'-3-dimethoxybibenzyl (I), schizandrin (II), 4,4'-dimethoxy-(1,1'-biphenanthrene)-2,2',7,7'-tetrol (III). CONCLUSION: Compound I is a new bibenzyl derivative and II was isolated from this plant for the first time.