Effects Of Phyllostachys Pubescens Invasion And Management Model On Soil Arbuscular Mycorrhizal Fungal Communities And Their Mechanisms

Moso bamboo(Phyllostachys pubescens)is the most important bamboo species in China.Recently,the bamboo forest invasion and human management have resulted in significant growth of moso bamboo forest area,and led to great changes of forest ecosystems consequently.Arbuscular mycorrhizal(AM)fungi are ubiquitous in terrestrial ecosystems,and could be affected by the shifts of environment.To investigate the effects of moso bamboo invasion and different management models on soil AM fungi communities and their mechanisms.High-throughput sequencing technique and phospholipid fatty acid(PLFA)analysis were used to analyze the variation of AM fungi communities and biomass,as well as their relationships with soil organic carbon sequestration.The results were as follows:(1)Moso bamboo forest expansion increased soil AM fungal neutral lipid fatty acid(NLFA)biomass,easily extracted glomalin-related soil protein(EE-GRSP)and water-stable macroaggregates.We observed that soil AM fungi biomass contribute largely to both soil macroaggregates and EE-GRSP,which were tightly correlated with soil organic C.The influence of bamboo forest expansion on soil C sequestration was mainly due to its indirect effect on AM fungi biomass.AM fungal communities showed strong niche differentiation,and were highly structured by forest type(P=0.001),and marginally correlated to soil properties(i.e.p H and soil organic C)during moso bamboo forest expansion.Our results indicated that bamboo forest expansion significantly changed soil AM fungal communities and increased fungal biomass,which in turn contributed to soil aggregation and C sequestration.(2)Soil nutrient contents decreased in content with the increasing extensive management age in moso bamboo forests.Moreover,the 18 year old plots were significantly lower than the 5 plots in both GRSP content and AM fungi biomass.We observed that the soil EE-GRSP was positively correlated with organic C,available K,and available N(P<0.05),and AM fungal phospholipid fatty acid(PLFA)biomass positively and significantly correlated with available N(P<0.01).The percentage of macroaggregates was found positively and significantly correlated with the of AM fungal PLFA biomass(P<0.01).In soils under long-term extensively management moso bamboo forests,Glomus increased in relative abundance while Acaulospora decreased significantly(P<0.05).The results indicated that AM fungal communities extensive management moso bamboo forest soils varied sharply from those under masson pine plantation(P=0.001).AM fungal communities were found significantly related to soil moisture(P=0.005)and available N(P=0.001),but marginally to available P(P=0.014).(3)In long-term intensivele managed moso bamboo forests,both soil AM fungi NLFA biomass and total GRSP content decreased significantly(P<0.05).Intensive management greatly altered soil AM fungi community composition,and not only soil N and P,but also K availability are the most important driving factors.Soil macroaggregate(250-2000 μm)proportion decreased 20-29% in bamboo forest soils with more than 15 years of intensive management history.Soil macroaggregate proportion and organic C content were found significantly correlated with AM fungi biomass and total GRSP content,indicating high risks of soil erosion and organic C decomposition in long-term intensively managed moso bamboo forests.