The Impact of Vegetation Type On Denitrification Activity in the Tributary Sediments.

A woody plant has a perennial stem that is above ground and covered by a layer of thickened bark and adapted to survive from one year to the next; as a result, the stem supports continued vegetative growth above ground from one year to next. However, herbaceous vegetation type has low C:N ratio and lignin content, resulting in easily decomposition. It can be expected that the difference of vegetation type can drive the rate of litter decomposition, which can influence the level of available carbon to denitrifiers. In order to explain the impact of different vegetation type on the supply of organic carbon content to denitrifiers in the tributary sediments, the cellulase, β -glucosidase and phenolic oxidase enzyme activities were measured with sediments and litters. Our results showed that the tributary sediment surrounded by woody vegetation had lower cellulase activities in litters and sediments than the tributary sediment surrounded by herbaceous vegetation type. Generally, the herbaceous litter in grasslands has a relatively low C:N ratio since it contains more nitrogen than woody species. Therefore, higher nitrogen content of herbaceous plant could drive more active cellulase activities in the tributary sediments and litter. In case of phenol oxidase, the change of activity was observed in the sediments; however the difference was not significant. Potential denitrification activity in the tributary sediments surrounded by herbaceous vegetation was higher than that of woody vegetation system. Therefore, the difference vegetation type can determine the level of labile carbon source, which could drive the denitrification activity in tributary sediments.