Dynamics of Nitrogen and Phosphorus Content during Leaf Litter Decomposition in Xiangxi River Watershed,the Three Gorges Region

Litter from riparian vegetation has long been recognized as an important energy flow in aquatic systems.Many researches on litter breakdown in drainage areas have been conducted,which could be used for assessing for the health of streams.To provide information for understanding nutrient cycling and energy flow in fluvial ecosystem,this paper focused on the leaf litter decomposition in Xiangxi River watershed,the Three Gorges region.The objective of this research was to examine the dynamics of nitrogen and phosphorus content of leaf litter decomposition in three plant species(Cotinus coggygria var.pubescen,Acer oliverianum and Acer flabellatum)along an elevation gradient using mesh bags.Three altitudinal plots were located in headwater at altitute of 1160 m,930 m and 658 m in Xiangxi River watershed.Leaf litter bags had been deposited in stream water and on the riparian woodland for 90 days.Our results showed that after 90 days,the dynamics of dry mass loss followed the declining exponential equation.No significant differences were found between original N content of leaf litter and leaf litter decomposition rates.The initial P content was strongly negatively correlated with decomposition rates.N and P content of leaf litter in Cotinus coggygria var.pubescens have a significant differences between Acer oliverianum and Acer flabellatum.However,elevation had no significant influence on dynamics of N and P content of leaf litter.Acer flabellatum leaf litter decomposed significantly much slowly in the woodland than in the stream.P content of Acer flabellatum leaf litter had a significant difference between in the stream and on the woodland,but N content had no significant differences.