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• Bamboo invasion increased the complexity of bacterial and fungal co-occurrence network. • Bacterial and fungal community-level habitat niche breadths increased gradually by bamboo invasion. • The deterministic process of bacterial and fungal community assembly generally was enhanced by bamboo invasion. • Soil dissolved organic matter was the most important factors mediating the bacterial and fungal community assembly. Moso bamboo (Phyllostachys edulis) invasion into adjacent broadleaf forests has been widely observed across subtropical China, and has induced negative effects on aboveground biodiversity. However, how bamboo invasion influences soil microbial community structure and assembly process remains largely unknown. We investigated the changes in diversity, structure and assembly processes of bacterial and fungal communities in an evergreen broadleaf forest following Moso bamboo invasion. Soil samples were collected from three forests (a pure Moso bamboo forest, an adjacent mixed bamboo-broadleaf forest, and a non-invaded broadleaf forest) along twelve invasion transects. Our results showed that bamboo invasion increased soil pH and decreased the contents of soil organic carbon (SOC), dissolved organic carbon (DOC), total and available nitrogen and phosphorus nutrients. Bamboo invasion significantly increased the diversity indices (i.e., OTU richness and Shannon index) of both bacteria and fungi and changed their community compositions (P < 0.05). Bamboo invasion significantly decreased the relative abundance of Actinobacteria and Basidiomycota whereas increased those of Ascomycota and Mortierellomycota. The co-occurrence network analysis displayed more connected and complex relationships of both bacterial and fungal communities in bamboo forest. Bamboo invasion increased the community-level habitat niche breadths of both bacterial and fungal communities due to increased abundances of generalists. The stochastic process of bacterial and fungal community assembly weakened and the deterministic process enhanced generally as a result of bamboo invasion. The migration rate of bacterial communities (0.615) was higher than that of fungal communities (0.037), indicating that dispersal limitation less affect bacteria taxa. Random forest model demonstrated that DOC content, followed by mineral N, were the most important factors mediating the bacterial and fungal community assembly. Taken together, our results suggest that bamboo invasion strongly altered the assembly of bacterial and fungal communities by regulating the deterministic-stochastic balance, which deepens our understanding of the role of bamboo invasions on ecological processes. [ABSTRACT FROM AUTHOR]

Intensive management practices, such as inorganic fertilization, soil tillage and understory removal, have been widely used to increase bamboo products and economic return in Moso bamboo ( Phyllostachys pubescens ) forests. Arbuscular mycorrhizal fungi (AMF) play a critical role in soil aggregation and carbon cycling. However, little is known about the effects of such long-term soil disturbance on soil AMF community composition and abundance, and their linkage to aggregation in Moso bamboo forests. We investigated soil chemical properties, water-stable soil aggregates, glomalin-related soil protein (GRSP), AMF community composition and biomass across a chronosequence of long-term intensively managed Moso bamboo forests (0, 10, 15, 20 and 25 years of intensive management) in a subtropical region of China. Our results showed that intensive management resulted in significant decreases in soil pH and high accumulations of soil available N, P and K contents. Both soil AMF biomass (indicated by neutral lipid fatty acid) and total GRSP content were significantly decreased with increasing duration under intensive management. High-throughput sequencing showed that intensive management greatly altered soil AMF community composition, and soil available N, P and K were important driving factors shaping it. Soil macroaggregate (>250 μm) proportion decreased by 20–29% in bamboo forest soils after 15 years of intensive management. Soil macroaggregate proportion and organic C content were found significantly and positively correlated with AMF biomass and total GRSP content, respectively, indicating a high risk of soil erosion and organic C depletion when AMF biomass was reduced in long-term intensively managed bamboo forests. In conclusion, our study suggests that long-term intensive management induced alterations in abundance and community composition of AMF are responsible for the decrease in soil aggregation in the Moso bamboo forests. Alternative management practices, such as reduced tillage and organic amendments, are urgently needed to improve AMF community in order to enhance soil aggregation and C sequestration in Moso bamboo forests. [ABSTRACT FROM AUTHOR]

• Bamboo invasion consistently increased soil pH and organic C content across three sites. • Bamboo invasion consistently decreased fungal ITS gene abundances across the sites. • Bamboo invasion improved the closeness of soil bacterial but not fungal communities. • Total soil enzyme activities positively correlated with the abundances of fungi rather than bacteria. Moso bamboo (Phyllostachys edulis) invasions into adjacent forests have been reported to threaten aboveground biodiversity and alter belowground soil processes. However, the impacts of bamboo invasion on soil microbial community composition, co-occurrence network and enzyme activity remain largely unknown. We presented a cross site field investigation on soil bacterial and fungal communities and enzyme activities in three forests (an original broadleaf forest, a mixed bamboo-broadleaf forest and a pure bamboo forest) at three sites in South China. Our results showed that bamboo invasion consistently increased soil pH (by 6.72% − 17.56%) and soil organic carbon concentrations (by 11.75% − 40.63%) across the three sites. Bamboo invasion consistently decreased fungal ITS gene abundances across the sites, but had little effect on bacterial 16S rRNA gene abundances and diversity indices. The community composition of both bacteria and fungi and their functional guilds differed among the three sites and were significantly (P < 0.05) affected by bamboo invasion. Bamboo invasion significantly decreased the relative abundances of ectomycorrhizal but increased those of soil saprotrophs. The complexity of co-occurrence network of bacterial communities was increased whereas that of fungal communities was decreased due to bamboo invasion. The activities of soil enzymes involved in C, N and P cycling were also altered by bamboo invasion, and they were significantly positively correlated with the abundances of fungal ITS gene and ectomycorrhizal rather than those of bacteria and predicted metabolic function. This study suggested that bamboo invasions into adjacent broadleaf forests had contrasting effects on soil bacterial and fungal communities by shifting microhabitats towards a condition that is unfavorable for some fungal functional guilds, which were tightly associated with soil functioning. These results highlight the need for sustainable forestry management against bamboo invasion to maintain fungal diversity and network complexity. [ABSTRACT FROM AUTHOR]

• Masson pine stand development changed community composition of root-associated fungi. • Near mature stands had remarkably higher enzyme activity but lower fungal diversity. • The composition of root-associated fungi had a direct impact on enzymatic stoichiometry. • Stand development altered enzymatic stoichiometry by affecting fungal composition. Root-associated fungal communities play a key role in plant productivity and soil processes in forest ecosystems. However, how diversity and composition of root-associated fungi change with forest development and their linkage with soil enzyme activities remain largely unknown. We characterized the root-associated fungal communities, plant and soil properties, and extracellular enzyme activities along a chronosequence spanning young (15 years old) to over-mature (63 years old) Pinus massoniana forest development stages. Our results showed that P. massoniana roots harbored diverse root-associated fungal communities and they varied with forest development. Near-mature (36 years old) forest stands had the lowest alpha-diversity but higher relative abundances of ericoid mycorrhizal and activities of enzymes involved in C, N and P acquisition. The relative abundances of ectomycorrhizal fungi and endophyte were higher in middle-age (24 years old) and mature stands (45 years old), whereas the relative abundance of ericoid mycorrhizal fungi was highest in the near-mature stand. Soil pH, soil C:P and N:P ratios were important factors shaping the diversity and composition of root-associated fungal communities. Structural equation modeling indicated that changes in the community composition, but not richness of root-associated fungi, had significant correlations with soil enzymatic C:N and N:P stoichiometry. In conclusion, this study suggests that different stand development stages exhibit distinct diversity and composition of root-associated fungal communities, which affecting soil functions in terms of enzymatic activity. [ABSTRACT FROM AUTHOR]

• Microbial composition and metabolic function were compared among three biochars. • Biochar increased N availability and decreased soil acidity in a bamboo plantation. • Biochar increased soil PLFAs and enzyme activities involved in C, N and P cycling. • Microbial functioning changes towards a faster C turnover in biochar treated soil. • Changes in soil acidity and soil nutrient availability are key driving factors. Biochar has been known as means to increase soil carbon (C) storage, and at the same time to ameliorate soil acidity and enhance plant growth. However, how biochar addition affects microbial community composition and metabolic function in subtropical plantation soils and their linkage with soil quality change is still poorly understood. We selected bamboo stick, corn straw and peel of Carya cathayensis as feedstocks to produce three biochars at 350 °C by slow pyrolysis, and added them to an acid bamboo (Phyllostachys praecox) plantation soil. Changes in soil nutrient and C availability, soil acidity, plant biomass, and microbial function in terms of C source utilization and soil enzyme activities were investigated after a three-month greenhouse trial. The results showed that the biochars from corn straw and peel significantly increased plant biomass, soil pH, organic C, total nitrogen (N) and dissolved organic N contents, while decreased exchangeable H+ and exchangeable Al3+ concentrations. The concentration of total phospholipid fatty acids (PLFAs) was increased significantly under biochars from corn straw and peel. The activities of β-D-cellobiosidase, N-acetylglucosaminidase and acid phosphatase were significantly increased by peel biochar. Soil basal respiration and microbial utilization rate of carbohydrates, carboxylic acids and amino acids compounds were significantly increased under the three biochars, suggesting a higher capacity of biochar-treated soil to catabolize C sources. Increased plant biomass was related to the increased N availability and decreased acidity. Our study suggests that biochar–induced changes in soil acidity and soil nutrient availability are key drivers shaping the composition of microbial communities and enhancing their catabolic capacity, but the effects on soil microbial function vary depending on feedstock origins. [ABSTRACT FROM AUTHOR]