Effects Of Simulated Warming And Nitrogen Deposition On Soil Microbes And Enzyme Activities In Chinese Fir In Mid-subtropical

Global warming and nitrogen deposition have been provoking a series of environmental problems, which attracted much attention of research workers, government agencies and the international society. The trend of global warming and nitrogen deposition will continue in the next few decades, depending upon the latest research. These changes may not only impact the growth of aboveground vegetation, but also change belowground soil environment, and this will directly or indirectly affect the microbial process. Microbial biomass and soil enzymes play significant roles in terrestrial environments, particularly through the decomposition of SOM, carbon sink or source dynamically and the transformation of soil nutrient. However, little knows about that how global warming and nitrogen deposition will affect the soil microbial and soil enzyme in the subtropical zone. Therefore, with setting the underground cables to warming, which combining with simulated nitrogen deposition experiment. We aim to study the responses of the microbial biomass and soil enzymes activity to the short-term simulated warming and nitrogen deposition in young Chinese fir (Cunninghamia lanceolata) in Sanming Fujian province in subtropical China. The results showed that,(1) Soil microbial biomass. Warming caused MBC, MBN, MBP significantly decreased by 19.2%,40.1% and 37.3% respectively; Nitrogen addition makes the MBC significantly increased to 19.71 mg kg-1, compared with the control plot increased by 11.4%, but there is no significant effect on the MBN and MBP. Compared with separate warming and nitrogen treatment alone, the simulated warming and nitrogen addition MBC, MBN, MBP significantly decreased by 44.3%,44.3% and 44.3% respectively. In addition, warming significantly increased the MBC/MBN, MBC/MBP. Nitrogen application significantly increased the MBC/MBP. Analysis of variance showed that warming has significant effects on MBC, MBN, MBP, and nitrogen significantly promotes the microbial activity, promoted the accumulation of MBC, interaction of warming and nitrogen also has a significant influence on MBC, MBN and MBP. Compared with separate warming and nitrogen addition, the interaction of warming and nitrogen addition obviously inhibits the accumulation of soil microbial quantity.(2) Soil enzyme activity. Warming significantly reduced the C-targeting and N-targeting enzyme activity, make the ?G and NAG a significant reduction in 29.2% and 49.8% respectively. AP, aim to decompose soil P, significantly increased 62.4% after warming. Nitrogen addition significantly increased the C-targeting enzyme activity, PHO aiming to decompose lignin increased by 47.9%.But the accumulation of inorganic nitrogen N the limit cycle of the accumulation of related enzymes NAG, no significant effect on P cycle related enzyme activity. Warming and nitrogen addition treatment significantly reduced the decomposition of hydrogen peroxide and other toxic substances related enzyme activity, leading to the PEO activity all processing level the lowest 5.26 ?mol g-1 h-1,74.6% less than the control. Under the condition of relatively abundant nutrient, soil pH and water content are the primary environmental factors affecting the soil enzyme activity.(3) Soil microbial community structure. Warming inhibits the growth of bacteria and Fungi, G+ and G-, ACT, Fungi and AMF biomass was significantly decreased 35.4%, 37.2%,32.7%,37.6% and 29.7% respectively. Nitrogen addition promoted the growth of bacteria and Fungi, the G+ and G-, ACT, Fungi, AMF biomass were significantly increased by 48.5%,48.5%,44.3%,49.1%,34.6%, and their proportion in the total PLFA was increased too. The interaction of warming and nitrogen addition also inhibits the growth of bacteria and fungi. Warming and nitrogen were likely to having similar microbial with warming treatment; Microbial quantities such as temperature, soil pH and MBC segment is longer, The RDA analysis showed that temperature, soil pH and MBC were the main reason that result in the change of soil microbial communities.(4) High-throughput sequencing. The advantage of the bacteria population was Acidobacteria, Proteobacteria, Actinobacteria and Chloroflexi, their relative abundance were 35.7%,31.6%,14.3% and 35.7% respectively.In warming plots, the relative abundance of Acidobacteria and Proteobacteria fell by 9.8% and 9.1% respectively, while the relative abundance of Actinobacteria and Chloroflexi increased by 7.4% and 5.5%, respectively. Warming decreased bacterial species diversity index (Shannon index) and dominant concentration index (Simpson index), showed that bacterial community diversity of species was decreased, and the advantage of the effect of strain strengthen. Nitrogen addition does not changes in the bacterial community structure, means that bacteria on short-term nitrogen add remains functional redundancy and functional recovery. The advantage of the fungal community population is Ascomycota, Basidiomycota and Zygomycota. Their relative abundance is 36.8%,22.6% and 17.8%, respectively. Little change after warming Ascomycota relative abundance, relative abundance and Basidiomycota increased by 8.5%, Zygomycota is decreased by 17.1% to 4.9%. Basidiomycota, Zygomycota after nitrogen increased by 7.2% and 7.2% respectively. Warming and nitrogen addition showed the change of the fungal community structure similar to that of the warming.