4.2 PhytOC long-term sequestration potential
Many previous studies have assessed the potential of PhytOC sequestration in various ecosystems, such as forest, grassland, wetland and agriculture ecosystems (Parr et al., 2010; Parr et al., 2009; Li et al., 2013b; Zuo et al., 2011). But most of these assessment are based on the PhytOC production in plant aboveground biomass, ignoring that in belowground biomass. A recent study (Chen et al., 2018) reports that the belowground biomass in a bamboo forest accounts for 39.41% of the total plant biomass.. Another recent study (Zhang et al., 2019) shows that the litter layer in bamboo forest plays a important role as phytOC storage. In native steppes, plant aboveground biomass turns to litter in current year, while the belowground biomass is huge and accumulated over multiple years (Chai, et al., 2014; Dai, et al., 2012; Hou, et al., 2014). Qi et al. (2016) shows that phytOC production from the belowground part is much greater than that from the aboveground parts for the typical steppe. The results of the present study confirms the previous findings with more data from three steppe types along a precitation gradient, and indicate the necessity to involve the belowground part in the assessment of PhytOC production and sequestration potential.