Correlation between distribution of soil organic carbon and soil physical properties for different secondary forests in Mangshan

ObjectiveThe relationship between soil organic carbon(SOC) distribution and physical properties of three types of secondary forests in Mangshan National Forest Park, Hunan, in order to provide reference for soil carbon storage calculation and soil carbon sequestration in the forests. MethodThirty-two soil samples in nine treatment plots had been collected which were set up in three types of secondary forests including Chinese fir , Pinus kwangtungensis and bamboo at altitude of 1230-1300 m. SOC, bulk density and field capacity of the samples were measured. Variance analysis, correla-tion analysis and regression analysis were conducted to study distribution characteristics and its relation with bulk density and field capacity. ResultSOC content in different layers of the three forests were significantly different (P<0.05, the same below). With the increase of soil depth,SOC generally decreased, but the variation range of SOC was different among these three types of secondary forests. There was a significant difference in variation between different soil layers. The proportions of SOC in 0-40 cm layer of Chinese fir(77.7%), P. kwangtungensis(77.1%) and bamboo(85.9%) forests were different.According to regression analysis, SOC-bulk density fitted value R for Chinese fir, P. kwangtungensis and bamboo forests were 0.632, 0.727 and 0.615 respectively. For Chinese fir forest, there was extremely significant correlation between SOC and bulk density(P<0.01, the same below). There was extremely significant difference or significant difference between SOC and field capacity in three types of forests. Variance analysis showed that there was extremely significant difference in clay , silt and sand contents at the same layer between different types of forests. Clay, silt and sand contents were not significantly correlated with SOC content(P>0.05), but there was extremely significant correlation between sand and clay, silt. At all vertical layers, sand content was higher than those of clay and silt in three types of forests. ConclusionSOC of different types of secondary forests in Mangshan is closely related with soil physical properties. Bulk density, field capacity, soil me-chanical composition can serve as indexes for forest management and increasing forest soil carbon sequestration.