Bioturbation Effect Of Crab Activities On Surface Soil In Tidal Flat Wetlands

As a part of food chain in wetlands,benthos influence the structure and properties of wetland soil and the growth of wetland vegetation through feeding,excretion,burrowing and other life activities.The activities of benthos are of great value to the improvement of wetland ecological function.To study the effect of benthos on sediments and its mechanism can provide reference for bioremediation based on benthos disturbance.In this paper,three typical beach plant communities such as Spartina alterniflora,Imperata cylindrica and Phragmites australis in Dafeng Milu National Nature Reserve were studied and the effects of different cave densities of Chiromantes dehaani on soil water content,bulk density(BD),salinity,total organic carbon(TOC),total nitrogen(TN)and total phosphorus(TP)were analyzed.The results showed that:(1)in autumn,the soil salinity in the enclosure of multi crab was significantly lower than that in the few crab area.The crab disturbance increased the soil moisture content and reduced the soil bulk density.The soil C/N and C/P in the multi crab area were significantly higher than that in the few crab area.(2)In winter,there were significant differences in the number of crab caves among different treatments in three plant communities.The number of crab caves in the natural area of S.alterniflora community was significantly fewer than that in the two enclosed treatment areas.The number of crab caves in the natural area of I.cylindrica community and P.australis community was significantly fewer than that in the multi crab area.In the community of S.alterniflora and I.cylindrica,the content of TOC and TN in the area with high disturbance intensity of crabs was low,while in the community of P.australis,the content of TOC and TN in the area with high disturbance intensity of crabs was high.The soil C/N and C/P in the multi crab area of S.alterniflora and I.cylindrica community were significantly lower than those in the few crab area,while in the P.australis community the difference was not significant.(3)In winter,the content of surface soil TOC in the multi crab and few crab areas of S.alterniflora and I.cylindrica communities was lower than that in the crab mound,while the content of surface soil TOC in different treatment areas of P.australis communities was higher than that in the crab mound.The content of TN in the surface soil of the two plants in the crab area and the natural area was slightly lower than that in the crab mound.(4)With the growth and death of crabs,the number of crab caves decreased in autumn and winter,but the content of TOC and TN increased in autumn and winter.From the early stage of plant growth to plant wilt,the content of soil TOC and TN increased significantly,and the value of soil C/N decreased significantly.(5)In autumn,there was only significant positive correlation between the content of TN and TP in S.alterniflora community.In different plant communities,the impact of crab disturbance in winter on the surface soil factors was different.In S.alterniflora community,the greater the disturbance intensity of crabs was,the lower the content of TOC and TN was.In I.cylindrica communities,the higher the crab disturbance intensity was,the higher the BD was.In P.australis communities,the higher the disturbance intensity of crabs was,the higher the soil salinity was.Crab disturbance significantly promoted the growth of S.alterniflora.The research found that the disturbance of C.dehaani decreased the stability of organic matter,accelerated the decomposition of carbon and nitrogen,and reduced the content of carbon and nitrogen in the surface soil in S.alterniflora and I.cylindrica communities.At the same time,the disturbance of crabs promoted the growth of biomass of S.alterniflora but the effect on the surface soil disturbance of P.australis community was opposite.