Abstract: The authors determined the Si concentration of mature leaves from 48 plant species along the Zhangjiang River Watershed,Fujian Province,and then investigated its relation to soil traits and its phenogenetic variations in different taxonomic groups.The results showed that the Si concentration varied significantly within different plant species,and the average value was 1.23%.Among these plants,Hippochaete debile beared the highest content as up to 5.88%,while Rhodomyrtus tomentosa was the lowest,only 0.02%.In terms of plant family,the plants of Graminae,Equisetaceae,Osmundaceae,Pteridaceae,Commelinaceae and Moraceae were rich in Si,with 17 species could be identified as Si accumulators, which shared the average Si content of 2.53%,while the other 31 species were non-accumulators since the average Si content was only 0.28%.The authors also noticed that water and clay content of soil increased along the upstream of Zhangjiang River to the downstream,which resulted in the increase of Si content in the soil accordingly.The Si concentrations of Lantana camara and Commelina communis were positively related to the effective Si content in the soil,while that of Aegiceras corniculatum and Kandelia obovata had positive relationships with the salinity of soil.