| As an important non-wood forest product,moso bamboo(Phyllostachys edulis)has great economic and ecological value and social benefits.Due to the increased planting of moso bamboo and its rapid growth and reproduction speed,natural forests are being replaced by moso bamboo monocultures,which affects the ecological functions of forest ecosystems,for example the soil nitrogen cycle.In this study,surface soil(0 — 20 cm)was collected in eight moso bamboo invasion belts in Tianmushan,Lushan and Wuyishan in China.Samples were taken from typical moso bamboo expansion regions: monoculture moso bamboo forest(BB),mixed forest(BBBL),and original forest(BL).Terminal-restriction fragment length polymorphism(T-RFLP)and quantitative PCR(q PCR)were used to study the community structures and abundances of nitrogen-fixing microbes,ammonia oxidizing archaea(AOA)and ammonia oxidizing bacteria(AOB)during moso bamboo invasion process.To assess the effects of moso bamboo invasion on soil nitrogen cycle related microbial communities,data was analyzed using multi-response permutation procedures(MRPP)to estimate the influence of geographic location,and redundancy analysis(RDA)to reveal the major chemical properties explaining variation in communities.Results from invasion belts in Qinglongshan,Shimendong and Jinshanmen in Tianmushan National Nature Reserve showed that moso bamboo invasion changed the abundances of soil nitrogen cycle related microbes.According to the q PCR analysis,the abundance of nitrogen-fixing bacteria decreased significantly in Jinshanmen,the abundance of AOA decreased significantly in all three belts,and that of AOB in Qinglongshan and Shimendong(P < 0.05).The terminal restriction fragment(T-RF)compositions of soil nitrogen cycle related microbes in BB,BBBL,and BL were different.MRPP showed that nitrogen-fixing bacterial community structures were significantly different between BL and BBBL,and BL and BB in Shimendong,and between BB and BBBL,and BB and BL in Jinshanmen(P< 0.05).AOA community structures were significantly different in all three forest types in all three belts(P < 0.05),with the exception of BB and BBBL in Jinshanmen.Both nitrogen-fixing bacteria and AOA community structures were significantly different between the three invasion belts(P < 0.05).The correlation analysis and RDA showed that different soil chemical properties explained the variation in community compositions in different invasion belts.Results from invasion belts in Biyun'an,Huanglongsi and Baxian'an in Lushan National Nature Reserve showed that moso bamboo invasion significantly increased the abundance of soil nitrogen cycle related microbes in Baxian'an.According to the q PCR analysis,there were no significant changes in the abundances of nitrogen-fixing bacteria and AOA in Biyun'an and Huanglongsi,whereas the abundance of AOB increased in Biyun'an and decreased in Huanglongsi(P < 0.05).MRPP results showed that the differences in nitrogen-fixing bacterial community structures between BL and BB,and BL and BBBL in Huanglongsi,and BB and BL in Baxian'an were highly significant(P < 0.01).The differences in AOA community structure between BB and BL in Baxian'an were highly significant(P < 0.01).Also,the differences in both nitrogen-fixing bacteria and AOA community structures between the three invasion belts were highly significant(P < 0.01).The correlation analysis and RDA showed that different soil chemical properties explained the variation in community compositions in different invasion belts.Results from invasion belts at site A and site B in Wuyishan National Nature Reserve showed that moso bamboo invasion significantly(P < 0.05)decreased the abundance of AOA and increased that of AOB,but did not affect nitrogen-fixing bacteria.MRPP results showed that nitrogen-fixing bacterial community structure between BB and BBBL both in A and B sites were not significantly different,whereas the differences between other forest types were significant(P < 0.05).AOA community structures were significantly different between all forest types in both sites(P < 0.05).The differences in both nitrogen-fixing bacteria and AOA community structure between two invasion belts were highly significant(P < 0.01).No significant correlations between soil chemical properties and microbial indicators were detected.RDA showed that different soil chemical properties explained the variation in community compositions in different invasion belts.Available potassium explained the variation in AOA community structure in both A and B sites(P = 0.026).Totally,moso bamboo invasion caused the increase of soil p H,and the abundance of nitrogen-fixing bacteria and AOA were higher in BB than BL,AOB was easily influenced but differently between all invasion belts,the community structure of these microbes were all changed.The influence of invasion belts' location even greater than the influence of moso bamboo invasion.No unified soil chemical properties were the main factors caused the microbes' variation. |
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