| Nematodes are the most widely distributed invertebrates in the soil and an important member of the soil ecosystem.They occupy multiple different nutrient levels in the soil food web and participate in the process of organic matter decomposition and nutrient circulation,which is important to maintain the stability of soil ecosystem structure.Over the past few decades,intensive human activities have led to the loss and degradation of a large number of coastal wetlands.In particular,the reclamation of wetland into farmland seriously affected the soil condition.However,it is not clear how coastal wetland reclamation affects soil nematode communities.To this end,this paper relies on two typical coastal wetlands in Tianjin: Beidagang Wetland and Qilihai Wetland.Wetland soils and corresponding farmland soils that have been cultivated for many years in the vicinity are collected to analyze the changes of soil nematodes community structure and diversity after years of cultivation of coastal wetland for farmland,so as to understand the effects of long-term cultivation on soil nematodes in tianjin coastal wetland.The main research results are as follows:(1)A total of 8626 nematodes were captured in this study,belong to 33 genera.The dominant genera were Acrobeloides,Prismatolaimus,Microdorylaimus,Helicotylenchus and Pratylenchus.After a long period of cultivation,the number and species of nematodes increased,with a small increase in Beidagang area,and a significant increase of 194.25% and 56.25% in Qilihai area,respectively.In different nematode c-p trophic groups,the proportion of c-p2 and c-p3 nematodes was relatively high,up to 30%-50%.After reclamation,c-p2 group increased and c-p3 group decreased,but not significantly.Among the different nutritive groups of nematodes,bacterial nematodes and plant parasitic nematodes were more abundant.After reclamation,the numbers of parasitic nematodes and predation/omnivore nematodes in Beidagang decreased significantly,and the numbers of fungal nematodes increased significantly,but there was no significant change in the Qilihai.The long-term cultivation of coastal wetlands enriched the species and quantity of nematodes,which were mainly contributed by nematodes of c-p1 and c-p2,as well as nematodes of bacterial nematodes and fungal nematodes.(2)After a long-term reclamation,the variation trend of diversity index of soil nematodes in the two wetlands was consistent,the diversity index(H'),evenness index(J'),richness index(SR)and nutrient diversity index(TD)all increased to different degrees,and the diversity index(H')and richness index(SR)increased significantly after reclamation in the Qilihai area.After long-term reclamation,there was no significant change in the functional index except the enrichment index(EI)in Qilihai sea.Combining diversity index and functional index that reclamation is conducive to stability nematode community for a long time,increase the complexity of the food web,increasing the biodiversity and ecosystem stability.In particular,in this study,the farmland in the Qilihai was least disturbed and the food web was in a stable and mature state,which also reflected the high degree of wetland degradation in the Qilihai wetland and Beidagang wetland.(3)In the correlation analysis between soil physical and chemical properties and nematodes,the pH value has a prominent effect on nematodes,c-p1,c-p2 and fungal feeding nematodes were negatively correlated with the content of total nitrogen,organic carbon and pH.Diversity index(H'),uniformity index(J'),richness index(SR),nutrient diversity index(TD)were significantly correlated with pH value.However,there was no significant correlation between the functional index(WI,NCR,MI)and pH value,total nitrogen content,organic carbon content and water content,but PPI/MI was negatively correlated with total nitrogen and organic carbon content. |
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