The Effects Of Warming And N Deposition On SOM In Chinese Fir Plantation At Molecular Level

Global warming and nitrogen(N)deposition are both aspects of global change.Soil organic matter(SOM)played an important role of the global C cycle since it contained about twice the concentration of C than the atmosphere.Hence,subtle effects on SOM might cause announced response to global C cycle.In this study,we combined the biomarkers and solid state 13C nuclear magnetic resonance technology to investigate the composition and degradation extent of SOM in molecular level under the global change.We set 4 treatments of control(CT),warming(W,5? above average soil temperature),N addition(AN,40 kg N ha-1 yr-1)and their interaction(WN),each treatments had 5 replications.The results showed:1)W caused the decline in MBN and MBP(p<0.05).W also inhibited the total PLFA amounts and microbial growth.The results of microbial biomass C:N:P stoichiometry showed that W significantly increased MBC:MBN ratio and decreased MBN:MBP ratio(p<0.05).It indicated that W inhibited the microbial growth with aggravating microbial N-limited problems.2)W increased the C:N atom ratio in loose combined HA that promoted nitric oxide decomposition.However AN decreased the E4/E6 ratio and hue coefficient?lgK,indicating that AN increased the complexity of construction.The infrared spectroscopy showed no difference under the treatments.3)The result of 13C NMR showed that soil was abundant in Alkyl C.However,W decreased the content of Carboxyl/carbonyl C by 1.09%.The value of Aromaticity did not significant change under different treatments.In general,the struction of SOM did not reveal too much change.4)W significantly decreased the free lipids(short-chain n-alkanoic acids,cyclic aliphatic compounds and carbohydrate)and bound lipids(ester-bound fatty acids,cutin-derived compounds and suberin-derived compounds)(p<0.05).AN only declined the ester-bound short-chain fatty acids.However,lignin content showed no significant difference between treatments.This shows that the labile components of SOM are vulnerable to decompose.However,the recalcitrant componets of SOM were relatively stable under the climate change.5)The results of regression analysis showed the decline in the free and bound aliphatic compounds was caused by effects of soil temperature(p<0.05),indicating that the labile componets of SOM were primarily effected by soil temperature.However,when warming and N addition combined,the results more closely mirrored those observed with N addition than warming alone.N addition are the dominate factor to the interraction due to relives the substrate and microbial biomass N limited problems.