Studies On Riparian Leaf Litter Decomposition In Xiangxi River Watershed

To provide information for understanding nutrient cycling and energy flow in fluvial ecosystems, this paper focused on leaf litter decomposition in Xiangxi River in northwestern Hubei Province, China. The objective of this research was to examine how rates of leaf litter decomposition in three plant species (Cotinus coggygria var.pubescens, Acer oliverianum and Acer flabellatum.) varied along an elevation gradient. For the purpose, mass loss dynamics of them were investigated using mesh bags. The three altitudinal plots were located in the headwater at alt. 1160m, 930m, 658m and lentic pool at alt 136m in Xiangxi River watershed. Leaf litter bags had been deposited in the stream water and on the riparian woodland for 90 days.Our results showed that after 90 days, the dry mass loss of leaf litter ranged from 13% to 80%. The dynamics of dry mass loss followed the exponential decay equation. In the first 3 days, dry mass of all the leaf litter lost rapidly. This leaching period was attributed to a physical processing of soluble compound. The dynamics of dry mass loss on the woodland showed fluctuated dynamics in 90 days. C.coggydia var.pubescens appeared medium decomposition rate that was significantly lower than that of A.oliverianum and A.flabellatum (p<0.05) . But there was not significant difference between the rates of A.oliverianum and A.flabellatum. However, elevation had no significant influence on the rates (p>0.05) . A.flabellatum leaf litter decomposed significantly much slowly (the rate ranged from 0.0027 to 0.0036 d^-1) on the woodland than in the stream. C.coggydia var.pubescens and A.oliverianum appeared higher rates in the lentic plots (alt. 136m) than three lotic plots.Carbon content in leaf litter decreased following mass loss. Elevation and species factor affected the C content dynamics significantly during the primary stage of breakdown. Different moisture and velocity condition also lead to significant variance of C content. C content of leaf litter decomposing on the woodland was higher than in the water.Nitrogen content in leaf litter increased with time and appeared fluctuated dynamics. It was not affected by elevation variation in the stream and woodland. C.coggydia var.pubescens and A.oliverianum in the pool appeared lower nitrogen content than in the streams. There were significant differences between the nitrogen...