Characteristics Of Nematode Communities And Their Responses To Spartina Alterniflora Invasion In The Litter Decomposition In Hangzhou Bay

Coastal salt marshes are ecosystems with unique functions,hydrology,soils and vegetations.They were formed by the interaction between aquatic ecosystems and terrestrial ecosystems and were also one of the most vulnerable ecosystems to invasion.With the change of elevation,the rapid change of environmental factors and biological communities are one of the most prominent features to the salt marsh.Litter decomposition process of salt marsh is not only affected by the regulation of the environmental factors with the elevation change.The change of microenvironment and litter quality led by Spartina alterniflora invasion can affect litter decomposition process of salt marsh.Nematode is an important animal group to litter decomposition of salt marshes,which can directly regulate the composition and activity of microbial community and indicate the structure and function of the decomposition food web.It revealed that the environment change led by elevation gradient affect on litter decomposition through to studied the comparative of the Phragmites australis decomposition process of salt marshes in different elevation dynamic and nematode communities.By comparing the dynamics and characteristics of nematode communities in the decomposition of invasion S.alterniflora and native P.australis in two kinds of habitats,revealed litter quality and habitats changes led by biological invasion in salt marsesh affect on the decomposition process,provided scientific basis for the protection and management of salt marshes.1)During the study,a total of 33 namatode genus were found in Hangzhou Bay,belonging to 28 families,7 orders.2)We studied the decomposition process of P.australis in high marsh,middle marsh,low tide,and mudflat with litter box method.The results showed that the decomposition rate of the early were fastest in mudflat and low marsh,the dry weight residual rate was lowest at the post-decomposition period.The number of nematodes was no significant difference between P.australis with control in mudflat and low marsh,and the percentage of algae nematodes of P.australis was highest.But,the number of nematodes in the litter box was significantly higher than control after 128 days,and mainly feed on bacterial nematodes.It showed that the mechanism of nematodes into the litter box mainly lied in the natural diffusion and just regarding the litter box as habitat in mudflat and low marsh,and actively attract climax in high marsh.The maturity index and structure index of the nematodes in the P.australis container were lower,indicating that the plant debris increased the fertility of the nematodes.Nematode of metabolic footprint and bacterial footprint of high marsh were significantly higher than mudflat,low marsh and middle marsh,suggesting that the nematodes metabolic activity of high marsh was increased,especially bacterial nematodes.3)To assess the influence of S.alterniflora invasion on litter decomposition,this study selected the S.alterniflora and P.australis in two different vegetation community as the research site,compared S.alterniflora to P.australis in the decomposition process in two habitats and the nematode community features by the litter box method.The results showed that the nitrogen content of the S.alterniflora was higher and the degradation was more rapid.the number of nematodes in S.alterniflora box in the whole experiment process was most,P.australis less,the number of nematodes of control least all the time.Nematodes metabolic footprint especially bacterial footprint of S.alterniflora than P.australis,which showed that the quality difference of S.alterniflora and P.australis was the main reason that changing litter decomposition and nematode communities.Litter decomposition rate of S.alterniflora and P.australis straw were no significant differences in two kinds of habitats and differences of nematode density,diversity,maturity index and metabolic footprint in two kinds of habitats were not significant,showed that litter decomposition process and nematode community affected by the change of soil physical and chemical environment led by S.alterniflora invasion was not obvious.4)To test the soil characteristics and soil nematode communities of salt marshes elevation and habitat types of hangzhou bay,to analy the potential impact of litter decomposition process factors of salt marsh wetland,we investigated soil physical and chemical characteristics and nematode communities in different seasones in hangzhou bay.The results showed that there were some differences between the soil bulk density,water content,electrical conductivity,total carbon and total nitrogen content in the salt marshes with obvious differences between the flood frequency and flood time.The effects of seasones on soil nematode density in different marshes were significant.The number of nematodes,nutritional group diversity index and maturity index of soil nematodes were significant in sampling marshes and seasones.The nematodes of low marsh had the highest diversity index and nutrition biodiversity as height increased gradually reduce and usually had high proportion of algae nematodes in low marsh,the percentage of bacterial nematode tend to increased with the increasing of elevation.The basic index of nematodes decreased with the increase of the elevation in both autumn and winter,but the structural index trend was reversed.CCA analysis showed that mudflat and low marsh had higher water content and electrical conductivity,and the number Mononchoides,Theristus and Viscosia is more.the high marsh had higher total carbon and total nitrogen content,and Tylenchus and Rhabditis was more.