Leaf litter breakdown of <i>Phyllostachys heterocycla</i>, <i>Lithocarpus glabra</i> and <i>Lindera glauca</i> in a headwater stream of Xitiaoxi watershed, upper reaches of Taihu Basin, China

Abstract

In order to explore the impact of the change of the dominant leaf litter source in stream from broad leaf trees to a bamboo tree of Phyllostachys heterocycla on headwater stream ecosystem and their associated benthic macroinvertebrates,we compared the leaf physical and chemical characters of Phyllostachys heterocycla,Lithocarpus glabra and Lindera glauca,and then evaluated the leaf litter breakdown of above three species using coarse-mesh litter bags in a headwater stream of Xitiaoxi watershed,Zhejiang Province.The concentrations of nitrogen,phosphorus and the thickness of the three categories of leaves varied significantly.The nitrogen concentration of bamboo tree leaf(30.23 g/kg) was much higher than that of L.glabra(20.98 g/kg) and L.glauca(9.69 g/kg).Moreover,the leaves of P.heterocycla(k=0.00592 d-1) decomposed faster than those of L.glabra(0.00297 d-1) and L.glauca(0.00212 d-1).No significant differences were observed in macroinvertebrates abundance and biomass among the three leaf types,however,the macroinvertebrate abundance and biomass varied significantly during the sampling period.Proportions of the functional feeding groups showed that shredders was the most abundant group,which represented 40.3% of individuals and 41.6% of the macroinvertebrate biomass,indicating it was an important component of fauna associated with litter breakdown.The dominant shredder taxon is Lepidostoma,which constructs nests based on broadleaves,and accounts for 14% of the total macroinvertebrate individuals.Because bamboo leaves are narrower,with higher concentrations of nitrogen and phosphorus,and defoliation occurs every two years.We concluded that when the leaf litter source of headwater streams dominated by bamboo leaf,it might change the concentrations of nitrogen and phosphorus in the stream water,the annual amount of leaf litter into stream,the retention time,and the macrobenthos community structure.