Effects Of Simulated Root Secretions On The Abundance Of Nitrification And Denitrification Genes

Artificial forest and potted soil methods were adopted in this experiment.In order to understand characteristics of soil bacterial community structure and abundance of acidic forest soil responsed to seasonal change in red soil hilly region of southern China,soil samples were collected from man-made forest soils with slash pine?pinus elliottii?and oiltea camelli?camellia oleifera Abel.?in January,April,July and October during two years.Quantitative polymerase chain reaction and terminal restriction fragment length polymorphism?T-RFLP?were used to determine the bacterial abundance and community composition of 16s rRNA gene.The results showed that the bacteria abundance,soil nitrate nitrogen,ammonia nitrogen and DOC content in Oiltea Camelli soil were significantly higher than those in Slash pine soil,and the soil bacterial community structure had obvious differentiation between the two tree species.Soil bacteria abundance and soil physicochemical properties fluctuated when seasons changed,but the interannual change was inconsistent.The bacterial community structure had no obvious seasonal variation and the common species in four seasons were dominated in each soil.The soil bacteria abundance positively related to the soil moisture inoiltea camelli soil,but the soil nitrate nitrogen,ammonium nitrogen and DOC content were closely related to soil bacteria community structure.In conclusion,tree species had more influence than seasonal change on soil bacteria abundance and community structures,and soil nutrient status induced by tree species was the key factor regulating the soil bacterial community structure.Based on the long-term simulated root system model with four different treatments developed?no fertilization control,nitrogen fertilizer application without carbon source control,glucose and nitrogen fertilizer,oxalic acid and nitrogen fertilizer?,taking the rhizosphere soil and non-rhizosphere soil samples in the simulated root system model as the research object,modern molecular biology technology applied to study the influence of long-term carbon source on the abundance of 16s rDNA,nitrification amoA and denitrification nirK,nirS and nosZ I genes in upland red soil.The results showed that the effects of carbon source on the treatment of nitrification and denitrification diversity genes were different under long-term culture conditions.The medium and long term application of carbon source in upland red soil reduced the gene abundance of all the above genes,but there were slight differences between the rhizosphere and non-rhizosphere soil and the treatment of different carbon sources.In general,long-term carbon source treatment changed the gene abundance and community structure of 16s rDNA,nitrification amoA and denitrification nirK,nirS and nosZ I to different degrees.The study also found that the amount of different genes in the soil during the nitrification process of archaea amoA>bacteria amoA.The number of different genes in the denitrification process was nirK+nirS>nosZ I,and this abundance sequence was consistent with the development process of denitrification.The proportion of 16s rDNA is about 10%.The study also found that adding carbon source made soil samples significantly correlated with the distance of simulated root system and soil residual NO₃^-,DOC,and NH₄⁺.N₂O is higher at the initial stage of emission,and becomes lower and more stable after two days.It also confirms the enhancement of nitrification and denitrification intensity at the initial stage of culture after adding carbon source.Then the microbial activity was inhibited due to the restriction of the soil background.