不同经营强度下毛竹丛枝菌根共生体对氨氧化微生物的影响

利用原位微宇宙试验将丛枝菌根(Arbuscular mycorrhiza,AM)真菌菌丝与根系区分,设置菌根室(RA)和菌丝室(AH)两个分室处理,以粗放经营(extensive management,EM)毛竹林为对照,研究集约经营(Intensive management,IM)条件下毛竹林土壤丛枝菌根共生体对氨氧...

Impacts of Mycorrhiza Symbionts on Ammonia-Oxidizing Microorganisms as Affected by Management Intensity of Phyllostachys pubescens Forests

[Objective] In this comparative study, impacts of soil arbuscular mycorrhizal symbionts on ammonia-oxidizing microbial communities and their response mechanism in moso bamboo (Phyllostachys pubescens) groves different in management intensity were investigated, in an attempt to provide a theoretical basis for scientific and rational application of nitrogen fertilizer in moso bamboo forests and contribution to mitigation of global climate change.[Method] Sample sites of bamboo groves similar in standing condition but different in management intensity, intensive and extensive, were selected for this field experiment, in each site, four 10 m×10 m quadrats or sample plots were set up, and in each sample plot two microcosmic systems were built up with PVC and nylon nets different in mesh number. With the aid of the microcosmic system, mycorrhiza fungal mycelia were separated from the mycorrhizal root system into two compartments:the mycorrhizal chamber (RA) and the mycelial chamber (AH). Once the systems were fixed, they were left in the soil and cultured in situ for 3 months. Soil samples were collected from the microcosmic systems with a soil auger for analysis in the laboratory. The soil samples were prepared into suspensions, (1:2.5=soil:water) for determination of soil pH with a pH meter; Alkali-hydrolyzale nitrogen (AN) was determined with the alkali-hydrolyzed diffusion method; available phosphorus (AP) was extracted with ammonium fluoride and hydrochloric acid solution and determined with a molybdenum-antimony colorimetry; available potassium (AK) was determined with the flame photometric method; soil organic C (SOC) with the potassium dichromate oxidation method; Soil nitrification potential with the aerobic culture method; copy numbers of amoA gene of ammonia-oxidizing archaea and bacteria with the Real-time quantitative PCR; and ammonia-oxidizing microbial community with the high-throughput sequencing technique.[Results] Results show that both intensive management and extensive management reduced significantly soil pH in the mycelial chambers (AH) in the moso bamboo forest, and only intensive management did soil alkali-hydrolyzed nitrogen in the mycelial chamber (AH). No significant difference was found between the two compartments of the same system in nitrification potential, but the soil nitrification potential in the mycorrhizal chamber (RA) in the bamboo forest was significantly higher under intensive management than under extensive management. AOA in the mycorrhizal chamber and mycelium chamber was significantly lower in gene abundance under intensive management than under extensive management, while AOB in the mycelium chambers was significantly decreased in gene abundance regardless of management intensity. Ammonia-oxidizing microbial communities did not vary much in composition or structure in either chamber under either management. However, network analysis shows that the ammonia-oxidizing microorganisms in the bamboo forest under intensive management displayed better interaction and symbiosis relationship, but less competition than those in the bamboo forest under extensive management.[Conclusion] To sum up, AM mycelia significantly reduce soil pH and AN content in intensively managed moso bamboo forests. Intensity of forest management does have significant impacts on nitrification potential, which however does not differ much between the two mycorrhizal compartments. Intensive management has significant effects on gene abundance of AOA and AOB in the AM mycelial compartment. Although management intensity does not have much impact on structure of the ammonia-oxidizing microorganism community in the soil, intensive management does dull nutrient competition among ammonia-oxidizing microorganisms to a certain extent.