The biomass and organic carbon distribution characteristics of each part of Cyclobalanopsis gilva were analyzed, and the biomass and organic carbon content models were constructed to provide basic theoretical parameters for the later screening of high carbon sink Cyclobalanopsis gilva families.

The standard tree of Cyclobalanopsis gilva with diameter of 4-14 cm was selected as the research object, the aboveground and underground samples were collected by single plant felling method and full digging method respectively. The biomass and organic carbon content were measured, and the biomass and organic carbon distribution differences of each organ were analyzed. The allometric growth equation was constructed.

1) With the increase of diameter class, the volume increases accordingly, and the growth rate of volume between adjacent diameter classes is “W” shape; 2) The aboveground biomass and organic carbon content of different diameter classes of Cyclobalanopsis gilva showed trunk (peeled) > living branch > leaf > bark > dead branch. The underground part was fine root lower than other parts. The aboveground biomass and organic carbon content accounted for more than 80%, while the underground biomass and organic carbon content accounted for less than 20%; 3) The tree height and DBH of Cyclobalanopsis gilva had a significant linear relationship with total biomass and organic carbon per plant (P<0.01). The fitting effect of biomass and organic carbon content model was the best in total biomass per plant, followed by trunk (peeling). The optimal fitting model equation of total biomass per plant was lnTBS = 2.233lnD + 0.138lnH-1.574, and the optimal fitting model equation of total organic carbon content per plant was lnTOCC = 2.112lnD + 0.578lnH-2.794.

Trunks and living branches are the main parts of the growth of C. gilva. Combined with DBH and tree height growth indicators, C. gilva families with large biomass and high carbon content can be screened out. In the later management process, attention should be paid to the growth of trunk shape of C. gilva.