Estimating realized and potential carbon storage benefits from reforestation and afforestation under climate change: a case study of the Qinghai spruce forests in the Qilian Mountains, northwestern China

Greenhouse gas emission has been scientifically shown to be the primary cause of observed global climate change. The reduction of greenhouse gas levels in the atmosphere deserves international attention. Aside from strategies to reduce emissions, increasing carbon (C) storage by forests has become an alternative method to lower carbon dioxide (CO₂) levels. The present study assesses the potential of C storage to decrease gas emission by restoring cleared and disturbed spruce (picea) forests in the Qilian Mountains, northwestern China. We first introduced and tested a new method for live aboveground biomass (AGB) estimation. We then used the method to define the relationship of AGB with topographic wetness index (TWI) and precipitation seasonality for total AGB estimation and quantification of the realized C storage in the live AGB of existing spruce forests. The same strategies were adopted to estimate the total AGB and the related potential C storage in the projected potential spruce forest distribution. A species distribution model was used, and the results showed that the AGB of the Qinghai spruce forests ranged between 2.30 and 4.96 Mg per plot (0.021 ha), i.e., 110 Mg ha^-1 to 236 Mg ha^-1). Actual total AGB was measured at 33 Tg, and C storage was 17.3 Tg in existing spruce forests. Potential total AGB and potential C storage were greater if the cleared and the potential C storage was ~50 Tg.