Effects Of Bird Aggregation On Soil Properties And Soil Microbial Communities In A Patchy Forest

The process of urbanization is going on all over the world,which leads to the fragmentation of forest vegetation and the reduction of bird habitat.Forest fragments in urban parks are one of the few places for birds to live in,so these forest fragments can attract a large number of birds to gather.The guano is an important fertilizer for plant growth.However,excessive guano deposited by large colonies of birds has been found to modify soil properties by significantly N and P increase,which in turn,can alter soil microbial community composition,potentially affecting the survival of plants and the forests' fragments sustainability by changing the microbial function.Therefore,we put forward the following scientific questions:whether the guano deposited by dense aggregation of birds will alters the chemical properties of soil,and then affect the soil microbial community in urban forest fragments.We hypothesized that the guano deposited by dense aggregation of birds alters the chemical properties of soil,and thereby changing the soil microbial community in urban forest fragments,which may affect the sustainability of forest patches.In order to test the hypothesis,we compared the soil properties,microbial communities and function of with bird aggregations forest and without bird aggregations forest in two forested islands,one in Liuhuahu Park and the other in Wanzuitou park,Guangzhou.The main conclusions are as follows:1.The soil chemical properties were significantly affected by excessive guano deposited by large colonies of loirds.In Liuhuahu Park,the contents of total nitrogen(TN),total organic carbon(TOC),nitrate nitrogen(NO3-),ammonia nitrogen(NH4+)and available phosphorus(AP)in sites with bird aggregations were significantly higher than those in sites without bird aggregations;the pH value in bird aggregation sites was significantly lower.In Wanzuitou Park,the contents of NO3-and AP in sites without bird aggregations increased significantly.Guano deposition induced soil eutrophication and acidification.2.The soil bacteria community composition and diversity were significantly affected by excessive guano deposited by large colonies of birds.In Liuhuahu Park,there was a high a diversity in the bacterial community in sites without bird aggregations.In the two parks,there were differences in soil bacterial community composition at phylum and genera levels between with bird aggregations areas and without bird aggregations areas.The relative abundance of Actinomycetes in sites with bird aggregations was significantly lower than that in sites without bird aggregations.Guano deposition induced soil bacterial diversity and relative abundance decreased.3.The soil fungal community composition and diversity were significantly affected by excessive guano deposited by large colonies of birds.In Liuhuahu Park,there was a high a diversity in the fungal community in sites without bird aggregations.In the two parks,the composition of soil fungal community at phylum and genus levels was different between with bird aggregations areas and without bird aggregations areas.In Liuhuahu Park,the relative abundance of Ascomycetes was significantly lower in sites with bird aggregations than in sites without bird aggregations.In Wanzuitou Park,the relative abundance of the Glomeromycota in sites with bird aggregations wassignificantly lower than that in sites without bird aggregations.Guano deposition induced soil fungal diversity and relative abundance decreased.4.Guano deposition have affected the functional microbial guilds.Among the bacterial functional guilds,the proportion of aerobic nitrite oxidizing bacteria,nitrate reducing bacteria and cellulose-decomposing bacteria in sites with bird aggregations decreased significantly.Among the fungal functional guilds,the abundance of saprophytic fungi in sites with bird aggregations was significantly lower than that in sites without bird aggregations in Liuhuahu Park.The relative abundance of pathogenic fungi in t sites with bird aggregations was significantly higher in Wanzhuitou Park.Decrease or increase in the levels of these functional microbial guilds may affect the decomposition of organic matter and plant resistance to disease.5.Changes in soil chemical properties resulted in changes in soil microbial communities.The results of redundancy analysis(RDA)showed that TN,NO3-and pH significantly affected the genus composition of the fungal community in Liuhuahu Park.Pearson analysis showed that there was a significant correlation between soil properties and fungal phylum composition and diversity.The relative abundance of Ascomycetes,Basidiomycetes and the ? diversity of the fungal were explained by NO3-,NH4+ and pH in Liuhuahu Park,respectively.In Wanzuitou Park,TOC,AP,and NO3-explained the changes in the relative abundance of Ascomycetes,Staphylococcus,and the ? diversity of the fungal,respectively.The aggregation of birds led to changes in soil properties,which in turn altered the composition of soil microbial communities in two urban forest fragments.