Effects of Spatial Expansion Between Phragmites Australis And Cyperus Malaccensis On Temporal Variations And Bioaccumulation of Vanadium In Coastal Marshes of The Min River Estuary, Southeast China

Vanadium (V) plays important roles in physio-ecological processes of marsh plants. To investigate the effects of spatial expansion between native invasive species (Phragmites australis, PA) and common native species (Cyperus malaccensis, CM) on temporal variations and bioaccumulation of V in coastal marshes of the Min River estuary, in situ filed sampling was conducted in PA marsh (PAM, before expansion), CM marsh (CMM, before expansion) and ecotonal marsh (EM, during expansion, marsh plants were denoted by PA' and CM') at different seasons by space-for-time substitution method. Results showed that, over all sampling seasons, the mean V contents in marsh soils ranged from 99.71 to 108.41 mg·kg-1 which exceeded its background value in soils of Fujian province (78.3 mg·kg-1). The V levels in soils differed among seasons or marshes. Higher V contents in soils of PAM, EM and CMM generally occurred in spring and winter. Over all sampling seasons, the V levels in profiles of EM were much higher than those of PAM and CMM. The temporal variation of V levels in soils of EM might rest with the alterations of soil pH, SOM and plant ecological traits during the spatial expansion. Although the V contents in PA, PA', CM' and CM differed among tissues, both the roots/stems (R/S) and roots/leaves (R/L) ratios were larger than 1 while the stems/leaves (S/L) ratios were less than 1, implying that the values in roots were much higher than those in other tissues. The V levels in tissues differed among species or seasons, which could be interpreted by the differences in ecological traits among plants and the competitive absorption for V by plants during the spatial expansion. Allocations of V in organs differed among seasons or species and roots were the main V stock of plant subsystems. This paper found that the V in soils of the Min River estuary existed enrichment process and the spatial expansion between PA and CM promoted its enrichment in soils and its bioaccumulation by plants.