Effects Of Wetland Soil Invertebrates On Plant Litter Decomposition Processes

Wetland plant litter is a huge pool of organic material and nutrient.Its decomposition is a key ecological process which links nutrient cycle and energy flow of wetland ecosystem.Soil invertebrates can influence on the plant litter decomposition processes through breakdown or graze activities.However,their role is usually been neglected in numerous studies of litter decomposition.Lake Poyang is the largest freshwater lake in China and one of the Wetlands of International Importance,which has extremely seasonal water level fluctuations.As so far,there is little information available on soil invertebrates affect plant litter decomposition in Lake Poyang.To solve this scientific question,here we conducted a field manipulative experiment to measure the decomposition of three dominant plant(Carex cinerascens,Triarrhena lutarioriparia,Phragmites australis)litter in Lake Poyang for further understanding the ecological role of soil invertebrate.Main results are as follows:(1)Decomposition rates of three plant litter obviously varied with experimental periods,likely due to seasonal effects.The highest decomposition rate of C.cinerascens was 0.01384 g/d when experiment reached 180 days.Meanwhile,T.lutarioriparia and P.australis reached their highest decomposition rates at 120 days and 105 days,respectively.The total decomposition rates of three plant litter were P.australis > T.lutarioriparia > C.cinerascens.And plant litter in bags with large size had higher decomposition rate than litter bags with small size.(2)During the decomposition processes,C,N and P concentrations of plant litter all had release-enrichment-release phases.While the enrichment of P concentrations of three plant litter was observed in 45 days.Results from Pearson relationship analysis indicated that decomposition rate of T.lutarioriparia litter in large size bags had a significant positive correlation with N/P ratio.(3)A total of 24 taxonomic groups of soil invertebrate species was identified in all litter bags,belonging to 3 families and 17 genera.22 species were collected fromlitter bags of C.cinerascens,20 species were collected from litter bags of T.lutarioriparia and 21 species were collected from P.australis.There were no significant variations in abundance,biomass or diversity of soil invertebrate among three plant litter bags.Higher total abundance and biomass were observed during the early phase of decomposition and reached the peak in May.In this study,chironomids were the most abundant species in soil invertebrate,and their abundance was up to74.89%.(4)Soil invertebrate accelerated the decomposition rates of three plant litter,making contributions from 18.51% to 49.59%.Their contribution was much higher during early(15-75 d)and middle(120-150 d)phases of decomposition.Meanwhile,a significant relationship was found between the breakdown rates of C.cinerascens and P.australis and soil invertebrate abundance,revealing that this fauna played an important role in plant litter decomposition processes in Lake Poyang.