Understory vegetation should not be ignored in the estimation of forest carbon stocks in Qilian Mountains National Nature Reserve

The Qilian Mountain National Nature Reserve is an important ecological barrier in northwestern China; therefore, it is of great importance to accurately evaluate the carbon storage of its main arbor forest. In this study, the Tianlaochi Basin of Qilian Mountain Nature Reserve was used as the research area to measure the carbon storage of the main arbor forests and determine the relationship between neglect of understory vegetation and errors in estimated carbon storages. The results showed that: (1) The total carbon storages of Picea crassifolia and Sabina przewalskii in Qilian Mountain Nature Reserve were 6.05 x 107 and 9.48 x 106 Mg and the carbon density were 426.07 Mg/hm2 and 338.72 Mg/hm2, respectively. (2) The understory carbon storage of Picea crassifolia and Sabina przewalskii accounted for 7.03% and 5.5% of the total carbon storage, respectively (6.81% combined). When the understory vegetation was neglected, the carbon storage in Qilian Mountain Nature Reserve was estimated to be less than 9.72 x 105 Mg. (3) There are large areas of Picea and Sabina forests worldwide; therefore, ignoring understory vegetation in these systems when estimating the carbon stock will lead to underestimations. Our research can provide a reference when estimating the carbon storage of similar tree species.