Effects Of Nitrogen And Phosphorus Addition On Soil Microbial Community Diversity In Forests Of Different Latitudes In Eastern China

Soil microorganisms play an important role in soil environment.By maintaining soil fertility,alleviating soil pollution,and regulating the decomposition of soil organic matter and nutrient circulation,as well as the formation of soil structure,soil microorganisms control many underground processes that are critical to the functioning of the ecosystem.Nitrogen?N?and phosphorus?P?are generally considered to be key growth limiting elements controlling species composition,diversity and productivity of forest ecosystems.For a long time,different researchers have conducted in-depth studies on the impact of nitrogen and phosphorus addition on soil microbial diversity in a single site or a single forest type,but few studies have been conducted on the latitude spatial distribution law of the impact of nitrogen and phosphorus addition on soil microbial diversity.Therefore,we established a multi-site nitrogen and phosphorus fertilization experiment in three different forest soil types in China?subtropical forest,warm temperate forest and cold temperate forest?in 2013.This paper reported the response of soil respiration,soil microbial community composition and enzyme activity to nitrogen and phosphorus addition in forest system at different latitudes after 4-5 years of NP addition treatment.Soil respiration was determined by stationary chamber method and gas chromatography,and microbial community composition was determined by phospholipid fatty acid?PLFA?and soil hydrolase activity was determined by Microplate fluorimetric assay method.The main research results are as follows:?1?Addition of N had a significant positive effect on soil microbial biomass and community composition in cold temperate forest.On the contrary,addition of N can reduce soil respiration in warm temperate forest,which has a significant negative effect on soil microbial biomass and community structure.In subtropical forests,addition of N inhibited microbial community,but had no significant effect on microbial biomass;?2?P addition significantly increased the microbial biomass in the subtropical forest and changed the composition of its microbial community,but P addition only showed a significant positive effect on the fungal biomass in the cold temperate forest soil.P addition increased soil respiration in both cold temperate forest and subtropical forest.P addition had no significant change in microbial biomass and community composition in warm temperate forest;?3?The interaction of N and P significantly increased the soil microbial biomass and changed the community composition in subtropical forests,while the results were reversed in warm temperate forests.In cold temperate forest,the interaction between N and P significantly changed the community composition,but had no effect on microbial biomass;?4?Compared to CK treatment,N,P and NP treatment make cold temperate forest?Changbai Mountain?soil?G activity significantly increased respectively 40.4%,42.8%and 120.1%,N and NP treatment make warm temperate forests?Jigong Mountain?soil?G activity significantly increased by 109.3%and 133.6%respectively,and P addition make the subtropical forest?Dinghu Mountain?soil?G activity significantly dropped by 34.9%.For soil NAG activity,compared with CK treatment,P and NP treatment in cold temperate forest?Changbai Mountain?increased its activity by 122.4%and 67.9%respectively.N,P and NP treatment increased the soil NAG activity of warm temperate forest?Jigong Mountain?by 78.9%,52.8%and124.4%,respectively.N and P treatment reduced and increased soil NAG activity by11.1%and 16.8%,respectively,in subtropical forests?Dinghu Mountain?.Compared with CK treatment,the soil activity of APA in cold temperate forest?Changbai Mountain?was significantly reduced by 28.6%by P treatment alone.The soil APA activity of the warm temperate forest?Jigong Mountain?was increased by 29.4%and decreased by 46.9%by N and NP treatmen.The N,P and NP treatments increased subtropical forest?Dinghu Mountain?soil APA activity by 47.4%,70.0%and 49.1%,respectively;?5?For?G/NAG,compared with CK treatment,the addition of N and NP significantly increased its in the cold temperate forest?Changbai Mountain?soil,while the addition of P significantly decreased its ratio.In the soil of warm temperate forest?Jigong Mountain?,the addition of N and P increased and decreased?G/NAG by 16.8%and 23.5%,respectively.In the soil of subtropical forest?Dinghu Mountain?,the addition of N significantly increased it by 28.2%,while P and NP treatment reduced it by 52.6%and 20.2%,respectively.For?G/APA,in the cold temperate forest?Changbai Mountain?soil,the addition of N,P and NP significantly increased?G/APA compared with CK treatment.In the soil of the warm temperate forest?Jigong Mountain?,only the effect of NP addition on G/APA was significant.In the subtropical forest?Dinghu Mountain?soil,the addition of N,P and NP significantly reduced the?G/APA.For NAG/APA,in the cold temperate forest?Changbai Mountain?soil,the addition of P and NP increased NAG/APA significantly,while the addition of N decreased NAG/APA significantly.In the warm temperate forest?Jigong Mountain?soil,the addition of N,P and NP significantly increased the NAG/APA by37.0%,74.1%and 337.0%,respectively.In the subtropical forest?Dinghu Mountain?soil,the addition of N,P and NP reduced the ratio by 42.0%,21.4%and 32.8%respectively;?6?In the cold temperate forest?Changbai Mountain?,?G activity was positively correlated with NO₃^-N?p<0.001,R=0.762?and DOC?p=0.012,R=0.611?,and negatively correlated with TC content?p=0.037,R=-0.524?.In the warm temperate forest?Jigong Mountain?,?G activity was only significantly positively correlated with soil TC content?p=0.004,R=0.682?;In subtropical forests?Dinghu Mountain?,?G activity was positively correlated with DOC content?p=0.001,R=0.751?,and was negatively correlated with AP content?p<0.000,R=-0.824?and TP content?p=0.001,R=-0.761?.For NAG activity,there was a significant correlation between its activity and TP content?p=0.002,R=0.706?and pH?p=0.050,R=0.497?in cold temperate forest?Changbai Mountain?.In the warm temperate forest?Jigong Mountain?soil,the content of AP?p=0.005,R=0.663?and TC?p=0.004,R=0.671?were positively correlated with it,while pH?p=0.013,R=-0.606?and the content of DOC?p=0.002,R=-0.711?were negatively correlated with it.For APA activity,there was no significant correlation between APA activity and environmental factors such as SWC,pH,DOC,NH₄⁺N,NO₃^-N,AP,TN,TC and TP in cold temperate forest?Changbai Mountain?soil.In the warm temperate forest?JiGong Mountain?soil,APA activity was significantly positively correlated with DOC?p=0.006,R=0.650?and significantly negatively correlated with AP?p<0.000,R=-0.807?and TP content?p=0.027,R=-0.551?.In the subtropical forest?Dinghu Mountain?,there was a significant positive correlation between soil APA activity and soil NH₄⁺N?p=0.027,R=0.551?,soil AP?p=0.021,R=0.570?and soil TP?p=0.031,R=0.539?contents;?7?In the cold temperate forest?Changbai Mountain?,there was no significant correlation between?G activity related to C cycle,NAG activity related to N cycle and APA activity related to P cycle.In warm temperate forest?Jigong Mountain?,?G activity was positively correlated with NAG activity?R²=0.6204,p=0.000?,and there was no significant correlation between?G activity and APA activity,or between NAG activity and APA activity.In the subtropical forests?Dinghu Mountain?,the correlation between?G activity and NAG activity was significantly negative?R²=0.4811,p=0.003?,the correlation between?G activity and APA activity was slightly significant?R²=0.2049,p=0.078?,and the correlation between NAG activity and APA activity was not significant.The results of this study will provide a theoretical basis for the in-depth understanding of the long-term effects of nitrogen and phosphorus addition on forest ecosystems at different latitudes,as well as for revealing the law of soil microbial changes in different forest ecosystems,and for predicting the dynamic changes and development trends of microbial diversity patterns and functional stability in different forest ecosystems under the background of global climate change?especially the change of nitrogen and phosphorus?.