Effects of iron addition on soil organic carbon mineralization characteristics under different vegetation types in Mount Luya
To explore the effect of iron(Fe)addition on soil organic carbon(SOC)turnover under different vegetation types,meadow,shrub,and forest samples obtained from surface soil(0-10 cm)and subsurface soil(10-20 cm)from Mount Luya in Shanxi,northern China,were incubated in the laboratory to study the effects of Fe addition on SOC mineralization characteristics.A first-order kinetic equation was used to fit the SOC mineralization process.Six main results were obtained.First,the SOC mineralization trend in meadow,shrub,and forest soils was consistent,indicating that mineralization was faster in the early stage.The SOC mineralization rate was the highest at the beginning of cultivation(1 d)and significantly decreased by 44.4％,57.0％,and 54.6％in the early stage of cultivation(1-20 days),slowed down significantly,and tended to be stable in the later stage.Second,the physicochemical properties of meadow,shrub,and forest soil were significantly different,with SOC,total nitrogen,alkaline hydrolytic nitrogen,available phosphorus,and soil water content decreasing with increasing soil depth.Third,the cumulative mineralization amount,mineralization rate,and mineralization efficiency of SOC in different soil layers of different vegetation types were greater at 0-10 cm than at 10-20 cm,with higher values in meadow and forest soils than in shrub soil.Fourth,addition of Fe(Ⅱ)inhibited the SOC mineralization rate in meadow,shrub,and forest soils.The rate of inhibition in meadow and forest soils(19.4％-32.6％)was higher than that in shrub soil(20.2％-28.3％).Additionally,Fe(Ⅱ)addition had a stronger protective effect on the SOC of the subsurface soil(24.9％-32.6％)than on that of the surface soil(16.0％-19.4％).Fifth,SOC mineralization in soil samples of the different vegetation types followed a first-order kinetic equation.The Cp/SOC values of shrub soil(4.86-7.87)were significantly lower than the values of meadow and forest soil(5.50-12.9),indicating that the SOC sequestration capacity was significantly weaker in meadow and forest soils than in shrub soil.The addition of Fe(Ⅱ)significantly decreased the soil Cp/SOC ratio,indicating that the addition of Fe(Ⅱ)promoted SOC sequestration in all vegetation types.Sixth,stepwise regression analysis showed that SOC,pH,and total phosphorus were the main driving factors affecting SOC mineralization.The collective findings indicate that vegetation type is an important factor affecting SOC mineralization and that the addition of Fe(Ⅱ)promotes SOC sequestration,which is closely related to nutrient availability and soil properties.This study provides basic data on how Fe oxides drive soil SOC turnover in different vegetation types on Mount Luya in the context of climate change.
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