Characteristics And Influencing Factors Of Soil Organic Carbon Mineralization At Different Temperatures And Illuminations In Subtropical Forests

Global warming has become an indisputable fact,forest soil carbon emission and sequestration plays an important role in the global carbon cycle.With economic development,forest clear-cutting lead to a large area exposed,to changes soil temperature and illuminance,which impact on forest soil carbon dynamics and global climate change cannot be ignored.Our study selected surface soils(0-10 cm)from Cunninghamia lanceolata(CUL),native forest of Castanopsis kawakamii(CAK),native forest of Castanopsis carlesii(CAC),in the Nature Reserve of Castanopsis kawakamii,Fujian Province.By incubation experiments simulation the temperature and illuminance of bareland,investigating characteristics and influencing factors of soil organic carbon(SOC)mineralization in subtropical forest.The conclusions as following:(1)Warming and illuminance significantly promote SOC mineralization,there was an interaction effect,and the temperature impact on SOC mineralization greater than illumination.There was significantly difference in there forest types of SOC mineralization and soil temperature sensitivity.Cumulative SOC mineralization in CUL was significantly greater than CAK and CAC,Q10 values in CAK was significantly less than CUL and CAC.At incubation 117 day,soil DOC content and soil enzyme activities significant increase with the increaseing soil temperature and illuminance;Illuminance had a greater impact on soil microbial community structure than temperature.Correlation analysis showed that cumulative SOC mineralization had a significantly positive correlattion with soil DOC,microbial respiration quotient,fungal PLFAs,the fungus bacteria ratio and soil enzyme activity(p<0.05).Q10 value of soil was significantly correlated with SOC,total nitrogen,DOC content and Humification Index(p<0.05).(2)Sterilization experimental results show that photodegradation including biological processes and abiotic processes,warming has no significant effect in abiotic process of photodegradation,but significantly promote CO2-C emissions in biological process of photodegradation.The main reason may be illumination can directly breakdown of soil lignin shielding,more C compounds available to microbial decomposers,soil DOCconcent increase,aromatic compounds decrease.Under warming conditions,soil enzyme activities and microbial efficiency enhancement.(3)The effect of illumination time on SOC mineralization vary due to different temperatures.20?,cumulative SOC mineralization of illuminance 12h,24h per day was significantly greater than illuminance 0h per day;30?,cumulative SOC mineralization rose significantly with increase of illumination time.Q10 values tended to increase with illumination time extended,but the difference was not significant(p>0.05).Correlation analysis showed that SOC mineralization has a significant positive correlation with soil DOC content,microbial respiration quotient and hydrolase activity(p<0.05).