Effects of intraspecific competition on growth, architecture and biomass allocation of Quercus Liaotungensis

Liaodong oak (Quercus liaotungensis) is an ecologically important tree species on the Loess Plateau in China that experiences strong intraspecific competition. Therefore, here, we aimed to clarify the strategies of Liaodong oak under intraspecific competition by examining the growth, architecture, and biomass allocation, and analyzed their relationships with the competition intensity. We found that intraspecific competition severely limited the accumulation of biomass in Liaodong oak and this competition was asymmetric among individuals. Intense competition among these trees resulted in a greater allocation of biomass to the belowground parts, allowing them to compete for moisture, which is a limited resource. Aboveground, the trees tended to allocate more resources to their trunks to ensure that tree height growth was not affected, resulting in a decreased diameter at breast height (DBH)/tree height ratio and tapering of the tree, thereby improving stem quality. By contrast, the amount of biomass that was allocated to the branches was greatly reduced through a reduction in the diameter and length of the branches rather than the number of branches.