Microbiological Meclianism Of Decomposition Of Bamboo Litter And Screening For Double-Effect Potassium-Solubilizing Bacteria

Phyllostachys edulis is one of the main economic trees,some bamboo forestry land degradated because of the low-level of intensified operation.Litter decomposition is the main way to nutrient return to the forest ecosystem,and the soil microorganism is the key factor for the litter decomposition and nutrient return.In order to provide a theoretical basis to effectively improve the soil fertility of bamboo forestry,the biological and environmental factors must make clear.We choosed Jinggang Mountain National Nature Reserve and Dagang Experimental Forest Farm as studied sites to explore the decomposition characteristics of the bamboo litter(BL)and their effecting factors using litterbag method.We also investigated the distribution characteristics of the mineral potassium-solubilizing bacteria(MPSB)in bamboo forestry,and analyzed the high efficient strains which could determine mineral silicon and potassium releasing.The main findings are as follows:(1)Decomposition rate of litter of bamboo leaves showed early decompose rapidly,while kept stable during the middle and later stage.Among the four different types of stands,the decomposition rates were the highest for bamboo forestry.The litter residual rate of bamboo was 20.82%(in bamboo forestry),26.69%(in broad-leaf forestry,BBLL),28.58%(in Chinese fir forestry,BCFF),30.68%(in Crytomeria forest,BCF)across the 2-year decomposition course.The content of total silicon and total phosphorus of bamboo litters in four different types of stands showed the slightly volatile increase,and both of them showed an accumulation-release pattern,which released quickly in the early then slowly in the middle and later stage.(2)Due to the effects of the decomposition of plant litter,the content of soil available silicon(SAv Si),soil total silicon(STSi)and soil amorphous silicon(SAr Si)in bamboo forestry a trend of decrease-increase-decreasewhile the content of soil organic silicon(SOr Si)and total phosphorus showed a release-enrichment-release pattern.In bamboo forestry,the content of soil available silicon in the later stage was significantly lower than those in the early stage(p<0.05),while the soil organic silicon(SOr Si)and total phosphorus in the later stage was significantly higher than those in the early stage(p<0.05).Content soil total silicon(STSi)and soil amorphous silicon(SAr Si)in bamboo forestry had no significant differences between the earlier stage and the later stage.The soil ratio of Si/P fell in the early stage sharply,and then fluctuated smoothly.(3)Protebacteria(22.14%～50.12%),Acidobacteria(14.42%～47.75%)and Planctomycetes(2.76%～30.83%)were the most abundant bacterial taxa during the decomposition process.The relative abundance of Acidobacteria in the early stage were significantly higher than those in the other stages(p<0.05),while that of Planctomycetes showed a reverse trend.Ascomycota(2.86%～57.62%),Basidiomycota(6.27%～56.63%)and Mortierellomycota(3.22%～66.10%)were the most abundant fungal taxa during the decomposition process.The relative abundance of Ascomycota and Basidiomycota in the early stage was significantly higher than those in the other stages(p<0.05),while that of Mortierellomycota showed a reverse trend.(4)Based on the multidimensional scaling analysis(NMDS),the results showed that the fungal and bacterial communities showed significant structure with stand type,which means that community composition of the indigenous microorganisms could not change by adding the bamboo litter and the community structure could be changed.With the decomposition time prolonging,the richness of the soil bacterial community in bamboo forestry increased,while the evenness and diversity decreased.The richness,evenness and diversity of soil fungal community in bamboo forestry in later stage were significantly higher than in the other stages(p<0.05).Furthermore,distance based redundancy analysis(db-RDA)indicated that the soil pH was significantly correlated with the change of the bacterial community,while the soil pH and available silicon were significantly related to the change of the fungal community.(5)Based on statistics of the number of colony-forming unit(CFU),MPSB showed a certain degree of preference,and the number of CFU in the bamboo was maximum.moreover,the number of CFU in the soil of the bamboo roots rhizosphere was significantly higher than that of the rhizosphere soil.There are 36 strains which could solubilize both silicate and potassium,which belonged to Paenibacillus,Kocuria,Bacillus,Staphylococcus,Pantoea and Burkholderia,Pseudomonas,Pantoea,Enterobacter,Quadrisphaera and Arthrobacter,in which the dominating genus in Jinggang Mountain National Nature Reserve was Paenibacillus and Bacillus,while in Dagang Experimental Forest Farm was Burkholderia.The strain NR33 possessed the widest inhibitory spectrum,and the isolate BF79 took the second place.The strain NR33 and BF69 showed high resistance to antibiotics including spectinomycin,rifampicin,ampicillin and kanamycin,both strains could survive well in the sterilized soil.Results of outdoor colonization test showed that strains NR33 and BF69 could be successfully colonized in the unsterilized soil.The above results indicated that the richness of soil fungi and bacteria increased gradually during decomposition process.The fungal and bacterial communities showed significant structure with stand type by adding bamboo litter to different stands,which indicated that community composition of the indigenous microorganisms could not change while the community structure could be changed.Furthermore,litter decomposition could change the microbial community succession,and the soil pH was the main factor controlled the succession of microbial community during the litter decomposition processes in Jinggang Mountain National Nature Reserve.