Microbial Diversity In The Phyllosphere Of Masson Pine And Its Decomposition Of Litter Needle

Plant phyllosphere is one of the important microbial habitats,and its microbial community composition affects plant growth,development,and nutrient cycling of forest ecosystems.Pinus massoniana Lamb.,as one of the main tree species in barren mountain afforestation in the south of the Yangtze River in China,has strong adaptability and plays an important role in barren mountain management and environmental improvement.At present,the research work on the phyllosphere microbes of P.massoniana has not started,and the diversity and function of the phyllosphere microbes of P.massoniana are still unclear.Some studies have pointed out that the phyllosphere microorganisms,as the first microbial group to colonize the litter,may directly participate in the decomposition of the litter,and we infer that the phyllosphere microorganisms of P.massoniana may play an important role in the decomposition of the litter needles.Based on this,this study took P.massoniana needles as the research object,and used high-throughput sequencing to elucidate the microbial diversity of its phyllosphere,and indoor decomposition experiments revealed the decomposition potential of pine phyllosphere microorganisms to littered needles.the result shows:(1)The microbes in the leaves of P.massoniana are diverse.A total of 1,232 OTUs of phyllosphere bacteria and 509 OTUs of phyllosphere fungi were found by amplicon high-throughput sequencing technology.On the whole,Proteobacteria,Firmicutes,and Cyanobacteria are the dominant phyla of P.massoniana phyllosphere bacteria,while Ascomycota and Basidiomycota(Ascomycota)and Basidiomycota(Basidiomycota)is the dominant door.Seasonal changes affected the foliar microbial composition of Pinus massoniana,with the highest bacterial species richness in spring,with 1,122 OTUs.The species richness of fungi was the highest in winter,with 515 OTUs.Chlorophyte bacteria are greatly affected by seasonal changes.Among them,Cyanobacteria is the dominant phylum in spring,Proteobacteria is the dominant phylum in summer and winter,and phyllobacteria in autumn The phylum Firmicutes is the dominant phylum.The composition of foliar fungi was stable in each season,and Ascomycota was the dominant phylum.In addition,there were1,018 phyllosphere bacteria and 366 phyllosphere fungi in each season.These seasonal coexisting microorganisms play an important role in the adaptation of P.massoniana to environmental changes(especially seasonal changes in temperature and rainfall).(2)With the increase of stand age,the microbial diversity in the leaves of Pinus massoniana showed different trends.The phyllosphere bacterial diversity of Pinus massoniana showed a trend of decreasing at first and then increasing with the increase of stand age;the fungal diversity of Pinus massoniana showed a trend of first increasing,then decreasing and then increasing.The 40-year-old P.massoniana had the highest species richness in phyllosphere bacteria,with 1,257 OTUs.The species richness of 40-year-old P.massoniana was the highest,with 460 OTUs.The predominant flora of foliar bacteria is greatly affected by the age of the forest.Among them,the phylum Proteobacteria is the dominant phylum for12-year-old and 22-year-old P.massoniana phylum,while the phylum Cyanobacteria is the dominant phylum for 12-year-old and 22-year-old P.massoniana phyllosphere bacteria.Cyanobacteria was the dominant group;the phyllosphere fungi of P.massoniana were relatively stable,and Ascomycota was the dominant phylum at all forest ages.There were 796 phyllosphere bacteria and 290 phyllosphere fungi in each forest age of Pinus massoniana.These shared microorganisms may be closely related to the development of Pinus massoniana.(3)The phyllosphere microbial community changed after the needles of Pinus massoniana were apoptotic.A large number of bacterial and fungal OTUs were shared between living needles,apoptotic needles(not yet in contact with soil)and decomposed needles.The results of indoor decomposition experiments showed that phyllosphere microorganisms carried by apoptotic needles could directly participate in the decomposition of P.massoniana litter needles.The decomposition process of P.massoniana needles can be divided into two stages: rapid decomposition period(the first 8 months)and slow decomposition period(after 8 months).The overall decomposition rate was as follows: foliar microbes + soil microbes(N+S)treatment > foliar microbes(N+SS)treatment > soil microbes(SN+S)treatment.There is a synergistic effect between phyllosphere microorganisms and soil microorganisms in the process of needle decomposition of P.massoniana.The decomposition rate of litter needles was significantly positively correlated with the rates of lignin and cellulose decomposition(P<0.01),but had no significant correlation with the activities of lignin and cellulolytic enzymes.Ligninolytic enzyme-polyphenol oxidase was significantly negatively correlated with peroxidase activity,while cellulolytic enzyme-β-glucosidase activity was positively correlated with cellobiosidase activity(P<0.01).(4)With the decomposition of litter needles,the microbial communities colonized on litter needles under different treatments showed different trends.With N+S treatment,the diversity of phyllosphere bacteria first decreased and then increased with the prolongation of decomposition time;the phyllosphere fungi showed a trend of first increase and then decrease with the prolongation of decomposition time.With N+SS treatment,the diversity of phyllosphere bacteria first decreased and then increased with the prolongation of decomposition time;the phyllosphere fungi showed a trend of first decrease and then increase with the prolongation of decomposition time.In SN+S treatment,bacterial diversity first decreased and then increased with the prolongation of decomposition time,while phyllosphere fungi first decreased and then increased with the prolongation of decomposition time.Overall,the SN+S treatment had the highest diversity,with a total of 1,700 bacterial OTUs and 203 fungal OTUs in each decomposition period.Under N+SS treatment,the total number of phyllosphere bacterial OTUs was 1,544,and the total number of phyllosphere fungal OTUs was 170 at each decomposition time.Under N+S treatment,the total number of phyllosphere bacterial OTUs was 1,219,and the total number of phyllosphere fungal OTUs was 182 at each decomposition time.These coexisting microorganisms in different periods may be the core microorganisms in the decomposition process of litter needles.From the analysis of the correlation between microbial taxa and the decomposition indicators of litter needles,Acidothermus is closely related to cellulose decomposition and may be involved in the decomposition of litter needles.Oidiodendron is closely related to lignin decomposition and may be involved in lignin decomposition of litter conifers.To sum up,this study preliminarily clarified the diversity of bacteria and fungi in the phyllosphere of P.massoniana,and confirmed for the first time that microbes in the phyllosphere can directly participate in the decomposition of pine needles.The excavation of the leaf core microbiome provides a theoretical basis.