Responses Of Soil Carbon And Nitrogen Components To Simulated Soil Warming And Nitrogen Deposition In Chinese Fir Plantation

Uncertainty about the tropical and subtropical forest ecosystem and its underground process how to response to the climate change in the future,and lacking the corresponding test data support in predictable models,therefore,setting up soil warming and nitrogen deposition simulative experiment is necessary in the tropical and subtropical regions.Adopting warming and nitrogen addition the two factors orthogonal experimental design,the experimental plots were located in the forest ecological system and global change research station of Sanming City in Fujian Province,control(CT),warming(W),nitrogen(N),warming and nitrogen(WN)four treatments were selected,five replicates per treatment.Using phospholipid fatty acid(PLFA)to analyze the changes of microbial community composition;to analyze changes in soil enzyme activity with 96 microplates method;quantitative analysis the change of soil carbon and nitrogen pools,recalcitrant carbon and nitrogen pools by using two sulfuric acid hydrolysis to discuss warming,nitrogen addition,nitrogen addition and soil warming interaction how to affect different soil carbon and nitrogen components in subtropical forest.The results are as follows:(1)The content of LPI-C(H2SO4-labile carbon pool ?)in soil was significantly reduced 26%(P<0.05)by increasing temperature,but,nitrogen addition,nitrogen addition and warming interaction treatments have no significant changes.The content of LPII-C(H2SO4-labile carbon pool ?)was significantly declined(P<0.01)with soil warming,nitrogen addition,warming and nitrogen addition interaction treatments by 36%,31%,34%(P<0.05)respectively.However,there was no significant difference in RP-C(recalcitrant carbon pool)content between control and the other treatments.This indicates that soil warming enhance the decomposition of soil active carbon pool(LPI-C,LPII-C),and accelerate the circulation of soil active carbon pool.Nitrogen addition,soil warming and its interaction significantly enhanced beta glucosidase activity and cellobiohydrolase activity,correlation analysis also shows that the change of active carbon and the degradation enzyme of soil carbon pool was significantly correlated.The results showed that the decrease of active carbon content in soil was affected by enhanced the soil beta glucosidase and cellobiohydrolase activity.(2)The content of LPI-N(H2SO4-labile nitrogen pool I)in soil was significantly reduced 21%(P<0.05)by increasing temperature,but,nitrogen addition and warming interaction treatments was significantly reduced 14%(P<0.05)and have no significant change with warming.This indicates that increasing temperature is the major factor to decrease soil active nitrogen pool I.The content of LPII-N(H2SO4-labile nitrogen pool II)was significantly declined(P<0.01)with soil warming,nitrogen addition by 25%and 18%,respectively.And there was a significant difference between warming and nitrogen addition.However,there was no significant change in the interaction between warming and nitrogen addition,indicating that the single factor effects of warming or nitrogen addition respectively could significantly affect the content of soil active nitrogen pool II.The content of RP-N(recalcitrant nitrogen pool)in soil was significantly reduced 20%(P<0.05)by increasing temperature,but,warming,nitrogen addition,nitrogen addition and warming interaction treatments have no significant change with control.As mentioned above,warming is the main factor causing the change of soil nitrogen content.(3)Warming treatment of ammonium nitrogen did not change significantly;but nitrogen addition and the interaction of nitrogen and soil warming significantly increased the content of ammonium nitrogen were 49%and 59%(P<0.05)respectly,all of them were significantly different from warming treatment.This indicates that nitrogen addition is the mainly cause with the increase of ammonium nitrogen content in the plots.Warming increased 57%the content of nitrate nitrogen(P<0.05),nitrogen addition treatment significantly reduced the nitrate content of 52%(P<0.05),and there was no significant difference between the interaction of nitrogen and soil warming and control,these show that,the nitrate nitrogen content was affected by double effects of nitrogen addition and soil warming,and the effects of nitrogen and soil warming can weaken each other.