The Effects Of Warming On Soil Organic Carbon Mineralization In Subtropical Broadleaved And Coniferous Forests

Soil organic carbon,the largest component of carbon pool in terrestrial ecosystem,whose response and acclimation to global warming is of great significance for predicting future climate change.Forest soils,which derive from granite and sandstone,were chosen in this study to thoroughly analyze mechanisms of soil organic carbon mineralization under three different environmental scenarios:?)in situ forest soil(IFS);?)refilled soils in heated columns(RHC);?)incubated soil under varied temperature(IVT).Results are as follows:(1)Soil organic carbon mineralization in IFSSeasonal variation of both soil respiration(Rs)and mineral soil respiration(Rm)followed a single-peak curve.Rs and Rm are both peaked in summer and reached the minimum in winter.Significant difference of annual flux among Castanopsis Lanceolata natural forest(NF),Castanopsis Lanceolata plantation(CAC)and Castanopsis Lanceolata secondary forest(CSL)could not be detected for either Rs(1585 g C m2yr-1 for CAS 1449 g C m2 yr-1 in NF;and 1344 g C m2yr-1 for CSL)and Rm(765 g C m2yr-1 for CAS;699 g C m2yr-1 in NF;and 762 g C m2yr-1 for CSL).Annual carbon fluxes of NF,CAS and CSL calculated based on low frequence(bimonthly)respiration measurement were underestimated by 66.7%,6.8%and 10%relative of measurements by high frequency(half an hour).(2)Soil organic carbon mineralization in RHCAnnual carbon flux from sandstone soil enhanced with increased warming amplitude(+2?,+5?,+7?).Annual carbon respirations from granite soil were significantly amplified by soil warming 5??Increased amplitudes of annual carbon flux from granite soils(24%)were greater than sandstone soils(18%)under the same warming scenario(+5?).Shading treatment(decreasing illuminance of 80%)and increased soil moisture content respectively and 5.8%compared with control,but no significant difference of annual carbon flux between treatment and control could be found(P>0.05).(3)Soil organic carbon mineralization in IVTTemperature increasing accelerate soil carbon mineralization rates of both granite and sandstone soil incubated under constant temperature,and respiration rates declined gradually with incubation time.Principal component analysis indicated that parent rock,followed by forest type,could explain the most variation of soil carbon mineralization under constant incubation;regulated by Iron-Aluminium Oxides,soil carbon mineralization rates were higher in granite soil than sandstone soil.Organic carbon content of severely degraded granite soil increased markedly after incubation 360 days,which could be reasonably explained by the existence of carbon-fixing bacteria.Incubation under variable temperature significantly promoted soil carbon mineralization of SNF and had no effect on carbon mineralization of SCUL.