Comparison Of Soil Microbial Composition And Diversity Between Mixed And Monoculture Rubber Plantations In Wenchang,Hainan Province,China

This study aimed to compare monoculture and mixed rubber plantations in terms of their soil bacterial and fungal composition.An Illumina MiSeq sequencing analysis was performed to investigate the composition and diversity of the soil bacterial and fungal communities among three different rubber(Hevea brasiliensis)plantations: monoculture,mixed 1(Hevea brasiliensis and Mytilaria laosensis),and mixed 2(Hevea brasiliensis and Michelia macclurei)in Hainan.The results showed that the bacterial composition of the three rubber plantations was basically similar.However,there was a significant difference in fungal communities among the three rubber plantations at both the phylum and OTU level.The species richness,Chao,and Shannon diversity of bacterial communities of monoculture rubber plantations were higher than the mixed 1 and mixed 2 rubber plantations,whereas all diversity indexes of fungal communities were relatively equal for the monoculture and mixed rubber plantations.The results of redundancy analysis ordination of bacteria at family level revealed that the soil organic matter(SOM),total nitrogen(TN)and total phosphorus(TP)did not change among the monoculture and mixed plantations.The highest total potassium(TK)was measured in mixed1,followed by monoculture and mixed 2 rubber plantations.The chemical properties such as TP,and SOM on the bacterial community composition had little influence,describing 6.53%,9.74%,and 11.19% of the variance,respectively.However,f??norank?c??JG37-AG-4,f??Acidobacteriaceae??Subgroup?1?,f??norank?c??Actinobacteria,f??Pseudonocardiaceae and f??Xanthomonadales?Incertae?Sedis,had positively variation.In addition,TN,Rubber Forest,TP,TK and SOM for fungal community composition at family level had little effect,describing only 5.50%,5.49%,3.61%,3.15%,and 2.96% of the variance,respectively.Furthermore,f??norank?o??Tremellales,f??unclassified?k??Fungi,f??Mortierellaceae,f??Trichocomaceae,f??Nectriaceae,and f??unclassified?c??Sordariomycetes,had also positively variation.The bacterial communities at phylum level revealed that the SOM,TP and Rubber Forest on the bacterial community composition had little influence,describing 7.01%,6.75%,and 6.49% of the variance,respectively.While,in respect of fungi,this variable combination explains21.49% of the total variance of phylum abundance.But,soil pH,WC,and Rubber forest were described 12.16%,11.91% and 9.06% of the total variance,respectively.The pH,WC,Rubber forest,TP,TN,TK and SOM,had positive variation with p??Basidiomycota,p??unclassified?k??Fungi,p??Rozellomycota and p??Ascomycota.The bacterial communities at class level showed that the bacterial communities had strongly positively associated with TK and Rubber Forest,but negatively correlated TN,TP,SOM,WC and soil pH.However,in case for of fungi at class level the ordination was strongly positively correlated with TP,pH,WC,SOM and TN,but negatively correlated Rubber Forest and TK,which explained 19.24% of the total variance.The results of Heatmaps Pearson correlation of bacteria at class level showed that the c??KD4-96 had highly positive correlation with TN.Furthermore,c??Betaproteobacteria,c??norank?p??Saccharibacteria and c??Deltaproteobacteria had also positive correlation with soil pH.In case of fungi at class level revealed that the c??Pezizomycetes was positively correlated with SOM and c??Archaeorhizomycetes was positively correlated with TN,respectively.The results of bacterial Pearson's correlation at genus level found that g??norank?f??YNPFFP1 and g??Bradyrhizobium had strongly negative correlation with TK,whereas Variibacter had positive correlation with WC.Furthermore,the fungi Pearson's correlation at genus level was observed that the g??unclassified?c??Sordariomycetes had strongly positive correlation with TN rather than other fungal species at genus level.The results of bacterial Pearson's correlation at family level observed that the f??Pseudonocardiaceae had strongly negative correlation with TK.The results of fungi Pearson's correlation at family level showed that the f??unclassified?c??Sordariomycetes was highly positive correlated with TN.We suggest that the alkaline fertilizers should be applied in mixed rubber plantations to improve the soil pH and,consequently,to increase the total diversity of the rubber plantation.Overall,long-term studies should be conducted to understand the behavior of bacteria and fungi in different forest species with addition of different feasible organic alone and co-application with mineral amendments.