Abstract: During the decomposition of emergent plants, nutrients are released into water, which will influence water quality, ecosystem stability, and even material cycling in the wetland. It is important to study the decomposition of emergent plants for the understanding of nutrient cycling in the wetland. In this study, we examined the degradation patterns of Phragmites australis and Typha latifolia, two typical aquatic plant species in Hengshui Lake, under different nitrogen concentrations. We further analyzed the effects of nutrient release on water quality during decomposition. The results showed that there were significant differences between those two species in terms of residue rate and effect on water quality. The decomposition process of both species had obvious stages. The residue rate was higher at the beginning and lower in the later stage. The decomposition rate of both species was improved by about 20% at the beginning, but the final degradation rate was not affected. The water quality indices during the decomposition of both species showed a trend of “slow rise-rapid rise-slow decline”. The effect of Phragmites australis decomposition on water quality was significantly higher than that of Typha latifolia, but the high nitrogen condition had no obvious effect on nutrient concentration in the water.

Key words: emergent plant, decomposition, nutrient, water quality