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To identify impact factors on the distribution and characters of natural plants community in reclamation area, with survey data from 67 plant quadrats in July 2009, soil properties data from 216 sampling points in April 2009, and TM (30 m) data in 2006, the composition and characteristics of natural plants community in different time of the Fengxian area in the Changjiang (Yangtze) River estuary were analyzed with two-way indicator species analysis (TWINSPAN), multivariate analysis of variance (MANOVA), detrended canonical correspondence analysis (DCCA) and canonical correspondence analysis (CCA). The results show that: 1) The plant communities in the reclaimed area are mainly mesophytes and helophytic-mesophytic transitional communities, showing a gradient distribution trend with the change in reclamation years. Species richness ( MA), species diversity ( H) and above-ground biomass also increase with the increase of reclamation years. Nevertheless, they appear to decline slightly in the middle and late reclamation period (> 30 years). 2) With the rise in land use levels, the changes in species richness and species diversity tend to increase at first and then decrease; species dominance ( D), however, tends to decline; and above-ground biomass increases slightly. 3) The distribution of the plant community is mainly influenced by the following factors: land use levels ( R = 0.55, p < 0.05), soil moisture ( R = 0.53, p < 0.05), soil salinity ( R = 0.43, p < 0.05) and reclamation time ( R = 0.40, p < 0.05). [ABSTRACT FROM AUTHOR]

The objective of this study is to analyze soil physical and chemical properties, soil comprehensive functions and impact factors after different years of reclamation. Based on the survey data taken from 216 soil sampling points in the Fengxian Reclamation Area of the Changjiang (Yangtze) River Estuary, China in April 2009 and remotely sensed TM data in 2006, while by virtue of multivariate analysis of variance (MANOVA), geo-statistical analysis (GA), principal component analysis (PCA) and canonical correspondence analysis (CCA), it was concluded that: 1) With the increase in reclamation time, soil moisture, soil salinity, soil electric conductivity and soil particle size tended to decline, yet soil organic matter tended to increase. Soil available phosphorous tended to increase in the early reclamation period, yet it tended to decline after about 49 years of reclamation. Soil nitrate nitrogen, soil ammonia nitrogen and pH changed slightly in different reclamation years. Soil physical and chemical properties reached a steady state after about 30 years of reclamation. 2) According to the results of PCA analysis, the weighted value (0.97 in total) that represents soil nutrient factors (soil nitrate nitrogen, soil organic matter, soil available phosphorous, soil ammonia nitrogen, pH and soil particle size) were higher than the weighted value (0.48 in total) of soil limiting factors (soil salinity, soil electric conductivity and soil moisture). The higher the F value is, the better the soil quality is. 3) Different land use types play different roles in the soil function maturity process, with farmlands providing the best contribution. 4) Soil physical and chemical properties in the reclamation area were mainly influenced by reclamation time, and then by land use types. The correlation (0.1905) of the composite index of soil function ( F) with reclamation time was greater than that with land use types (−0.1161). [ABSTRACT FROM AUTHOR]

Abstract: We compared reproductive characteristics of Scirpus mariqueter and Spartina alterniflora in monocultures and mixed communities to assess the importance of clonality in the population distribution and colonization of the two species. In the core S. alterniflora zone, individuals were taller and there were fewer underground tillers than in the Spartina–Scirpus zone. Every sexual S. alterniflora individual produced about two underground tillers in the S. alterniflora zone, which was two thirds as many as in the Spartina–Scirpus zone. In contrast, the height of sexual S. mariqueter was the highest in the mixed zone, whereas the numbers of flowering individuals and vegetative individuals were the highest in the core and the Scirpus–tidal flat zones, respectively. In the Scirpus–tidal flat zone each sexual individual produced 14 vegetative individuals, which was 23 times that produced in the mixed zone, and 45 times that in the core zone. Aboveground biomass and density of sexual individuals decreased from the core to the Scirpus–tidal flat zone. The ratio of aboveground to belowground biomass was lower in core zones of the two species than in their mixed zones. From the S. alterniflora to the tidal flat zone there was a decrease in salinity and redox potential and an increase in soil moisture. [Copyright &y& Elsevier]