Effects Of Organic Farming On Bird Species Diversity And Composition In Rice Fields Of Shanghai

Organic farming,a way to cope with the decline of farmland ecosystem function,has been gradually applied,and its role in the maintenance or conservation of farmland biodiversity has been widely recognized.Since organic farming was applied in the rice fields in Shanghai,the research on planting technology has developed rapidly,but its impact on biodiversity has not been evaluated.Because birds are sensitive to the change of farmland habitats,located in the upper middle of the food chain,have distinct niche differentiation,and are easy to identify in taxonomy,they are good indicators of the health of farmland ecosystem.In this study,birds were selected as indicator organisms,and rice fields in Shanghai were taken as research objects.From November 2018 to October 2019,bird diversity,community composition and structure of organic and conventional rice fields in Songjiang,Jiading,Fengxian and Chongming were calculated month by month.In order to provide the basis for the protection and restoration of urban farmland ecosystem,we compared the differences of bird communities between the two kinds of fields,analyzed the seasonal dynamics,and discussed the relationship between bird community distribution and environmental factors.The main results are as follows:1)A total of 60 species of 11161 birds were recorded,belonging to 11 orders and 29 families.Among them,the proportion of resident birds was the largest,accounting for 43.33%,the proportion of winter and summer migratory birds was 50.00%,and the proportion of tourist birds was 6.67%;The proportion of songbirds was the largest,accounting for 58.33%,and the proportion of waders was 27.78%;The dominant species were Eurasian Tree Sparrow and Spotted Dove;The proportion of insectivorous birds was the largest,accounting for 38.33%.2)The number of orders,families and species of birds recorded in organic rice fields was significantly higher than that in conventional rice fields(p<0.01);The species richness and abundance of resident birds,winter migratory birds and summer migratory birds in organic rice fields were significantly higher than that in conventional rice fields(p<0.05);The species richness and abundance of songbirds and waders in organic rice fields were significantly higher than that in conventional rice fields(p<0.05);The species richness and abundance of carnivorous birds and insectivorous birds in organic rice fields were significantly higher than that in conventional rice fields(p<0.01);The species richness and abundance of birds listed in "China-Australia Migratory Bird Agreement",the "three haves" protected animal list in China and the “list of key protected wild animals in Shanghai" in organic rice fields were significantly higher than that in the conventional rice fields(p<0.05).3)The seasonal changes of birds in rice fields are obvious.The species richness of birds in rice fields was the largest in April and the smallest in November,and the abundance was the largest in February and the smallest in August.The species richness and abundance of organic rice fields were significantly higher than that in conventional rice fields in spring,summer and autumn(p<0.05);The species richness and abundance of resident birds in organic rice fields were significantly higher than that in conventional rice fields in summer and autumn(p<0.01);The species richness and abundance of summer migratory birds in organic rice fields were significantly higher than that of conventional rice fields in spring and summer(p<0.05);The species richness and abundance of songbirds in organic rice fields were significantly higher than that of conventional rice fields in summer(p<0.05);The abundance of waders of organic rice fields was significantly higher than that in the conventional rice fields in summer,autumn and winter(p<0.05);The species richness of carnivorous birds in organic rice fields was significantly higher than that in the conventional rice fields in autumn and winter(p<0.01);The abundance of carnivorous birds and insectivorous birds in organic rice fields was significantly higher than that in the conventional rice fields in summer,autumn and winter(p<0.05).4)The results of RDA analysis showed that soil pollution and soil animals were the important factors driving bird composition in rice fields;The first axis was mainly related to the abundance of small and medium-sized soil animals,polycyclic aromatic hydrocarbons and heavy metals,and the second axis was mainly related to semivolatile organic compounds and heavy metals.The distribution of organic rice fields plots was negatively correlated with mercury of heavy metals;The distribution of conventional rice fields plots was positively correlated with mercury,zinc,lead and copper of heavy metals,and positively correlated with nitrobenzene-d5 and 2,4,6-tribromophenol of semivolatile organic compounds.In terms of residential types of birds,the resident birds were positively correlated with the abundance of small and medium-sized soil animals;Winter and summer migratory birds were negatively correlated with the mercury of heavy metals.In life types of birds,there was a positive correlation between the abundance of land birds and small,medium-sized soil animals;The waders are mainly negatively related to nitrobenzene-d5 and 2,4,6-tribromophenol of semivolatile organic compounds.In terms of feeding habits of birds,carnivorous,insectivorous and omnivorous birds are mainly negatively related to mercury of heavy metals.In conclusion,the different cultivation patterns of organic and conventional rice fields in Shanghai had an impact on bird communities in rice fields.The organic cultivation pattern could significantly improve bird species diversity and optimize species composition,which was the result of the joint drive of chemical and biological environment factors in rice fields.This study provides a basis for the protection and restoration of urban farmland ecosystem.