Response Of Boreal Forest Rhizosphere Microbes To Nitrogen Addition

Our country's boreal forests play an important role in coping with global climate change.Under the trend of increasing global nitrogen deposition,the research on the response of the underground rhizosphere of boreal forests to nitrogen deposition had not yet obtained consistent results.For this reason,this experiment set four levels of nitrogen application:blank control(CK,0g N m^-2yr^-1),low nitrogen(LN,2.5g N m^-2yr^-1),medium nitrogen(MN,5g N m^-2yr^-1),high nitrogen(HN,7.5g N m^-2yr^-1),to study the physical and chemical properties,rhizosphere effects,and soil microbes of the rhizosphere and bulk soil of Larix gmelinii,a dominant tree species in northern forests.The direction and intensity of community structure,relative abundance,and diversity of response to long-term artificial nitrogen addition were expected to provide a reference for the study of the response of the underground part of the northern forest ecosystem to nitrogen deposition.The results showed that:nitrogen addition significantly changed some soil characteristics related to soil C cycle,the bulk soil TC content under medium nitrogen addition was significantly lower than that of the control and the rhizosphere high nitrogen group;the rhizosphere MBN content under high nitrogen addition was significantly higher than that of the control group and the bulk soil nitrogen group;the rhizosphere and bulk soil bacterial and fungal communities had different responses to nitrogen addition:the response of the fungal community was greater than that of the bacterial community,and the source of the difference in response.It was the diversity of the fungal community,the rhizosphere effect weakens the microbial changes caused by nitrogen addition;the addition of nitrogen significantly changes the diversity of the rhizosphere and bulk fungal community;the diversity of the soil fungal community after the addition of nitrogen turned into a negative rhizosphere effect;bacterial advantage Proteobacteria and Basidiomycota,the dominant fungal population were significantly negatively correlated with the Shannon diversity index;there were significant differences between bacteria and fungi at different taxonomic levels in each treatment group with nitrogen addition,which can be used as an indicator species.