Litter decomposition and associated macro-invertebrate functional feeding groups in a third-order stream of northern Guangdong
粤北地区溪流中的树叶分解及大型底栖动物功能摄食群

By placing 5 mm-and 0.1 mm mesh bags with Dracontomelon duperreanum(Anacardiaceae)and Syzygium jambos(Myrtaceae)litters in the Hengshishui Stream,a third-order stream in northern Guangdong of China,this paper studied the decomposition of the litters and the colonization of macro-invertebrates over a 101-day period.The results showed that the decomposition rate of D.duperreanum litter in 5 mm-and 0.1 mm mesh bags was 0.0247 d-1 and 0.0151 d-1,while that of S.jambos litter was 0.0108 d-1 and 0.0095 d-1,respectively,indicating that D.duperreanum litter decomposed faster than S.jambos litter,and the decomposition rates of these two kinds of litters were higher in coarse mesh bag than in fine mesh bag.Among the colonized macro-invertebrate functional feeding groups,scraper occupied the highest proportion(36%),followed by collector(33%),predator(25%),and shredder(6%).At the middle and late stages of the experiment,the total number of individuals and the numbers and densities of dominant groups of macro-invertebrates on D.duperreanum litter were significantly higher than those on S.jambos litter.It was suggested that in the subtropical medium-size streams where shredders are few or absent,scrapers play an important role in the breakdown of litter.The low decomposition rate of S.jambos litter was mainly due to its high content of polyphenols which inhibits microbial activity and makes the litter less eatable to the macro-invertebrates.