Vertical distribution of soil organic carbon in Cunninghamia lanceolata plantation

Taking Chinese fir plantation as the research objective , vertical distribution of soil organic carbon (SOC) and its relationship with soil pH value , total nitrogen content and soil C/N ratio in Chinese fir plantation were studied .In addition , different land use types of Chinese fir plantation were compared .The results showed that the vertical distribution of SOC in Chinese fir plantation varied with soil depth .The differences of SOC concentration in different layers were as follows :0 -15cm soil layer (20.6 gkg-1) 15 -30 cm soil layer (17.1 gkg-1) 30 -45 cm soil layer (12.4 gkg-1) 45 -60 cm soil layer (9.8 gkg-1) 60 -75 cm soil layer (8.2 g kg-1).Average SOC concentration with three kinds land use types was ranked as follows :the closed Chinese fir forest lands (13.6 g kg-1) the economic forest lands (12.3 g kg-1) the fallow lands after farming (11.0 gkg-1).SOC concentration of different layers in Chinese fir plantation had a positive linear correlation with the soil pH value (r 0.40), and a significant positive relationship with the contents of total nitrogen (r 0.81) and C N ratio (r 0.87).[ Ch , 2 fig .2 tab .14 ref .]