Above-ground carbon storage in Pinus pumila along an alpine altitude in Khingan Mountains, Inner Mongolia of China

The carbon (C) cycle in alpine ecosystems is sensitive to climate change, but information about the C storage in its undergrowth is scarce. In October 2017, a total of 6231 Pinus pumila (Pall.) Regel trees were investigated for above-ground growth and density in 60 sub-plots (10×10 m) from 12 stands (50 × 50 m) along the altitudinal gradient (800-1500 m a.s.l.) in Great Khingan Mountains, Inner Mongolia, Northeast China. Sites were characterized by different crown densities (CDs) from 20% to 90%. Height and root-collar diameter (RCD) were higher in stands with CDs of 40-70% than CDs of 20-30%. Stem density (SD) and crown area (CA) had a positive correlation with altitude and CD. Equations from local shrub models were used to adapt the allometric growth models for estimation. There were variations in estimated above-ground C density depending on the model and the involvement of the canopy area. Above-ground C storage in P. pumila individuals ranged from 0.05-2.46 kg tree-1, which corresponds to C storage density ranged from 0.17-37-ton ha-1. The C density in P. pumila increased with crown density instead of stem density along increasing altitudinal gradients and increasing RCD. Hence, the crown density and diameter of a P. pumila plant can be used to predict the above-ground C density of its natural population.