Organic Carbon in Soil Aggregates and Its Dynamic Changes of Larch Plantations in Black Soil Region

Following 8,21,30,37 and 52-year-old larch(Larix gmelini) plantations in typical black soil region,a study was undertaken to examine soil organic carbon distribution characteristics of aggregates and dynamic changes of plantations by measuring and analyzing composition of dry aggregates,organic carbon content and organic carbon storage of different aggregate size fraction.Results showed that during soil depth of 0-30 cm,the composition proportion of aggregates was distribution in shape of ∧with decreasing size fraction.The percentage of 2~5 mm size fraction accounted the largest proportion and existed significant difference from those of other size fractions (P0.05).The organic carbon contents of all different size aggregates in topsoil,range of 32.17~48.75 g/kg,were higher than those in subsoil,range of 28.82~33.53 g/kg.Lowest organic carbon content was found in 2~5 mm aggregate and which was significant different from those of other size fraction aggregates (P0.05).The changing trend of organic carbon storage during soil profile was very similar to that of dry aggregate distribution among larch plantations with different ages.The soil organic carbon storage in topsoil was higher than that in subsoil.Organic carbon storage in 2~5 mm aggregate was also the highest in all size fractions.We concluded that changes of organic carbon storage in soil aggregates were mainly determined by the composition of soil aggregates,but for the organic carbon contents.It presents a theoretical basis for further researches and assessments on SOC of larch plantation.