3.5 The PhytOC sequestration potential and its relations with environmental factors
The PhytOC stock in the aboveground biomass ranged from 0.38±0.07 to 0.71±0.09 kg ha-1, and was significantly lower in desert steppe than in two typical steppes (P <0.05); and PhytOC stock in the belowground biomass ranged from 4.67±0.16 to 8.79±0.36 kg ha-1, and was significantly lower in desert steppe and dry typical steppe than in wet typical steppe (P < 0.05) (Table 3).
The PhytOC production flux of steppe communities were estimated based on the NPP and its PhytOC content, and were 0.38, 0.71 and 0.66 kg ha-1 yr-1 from the aboveground part (ANPP), and 7.88, 9.14 and 21.01 kg ha-1yr-1 from the belowground part (BNPP), respectively in the desert steppe, dry typical steppe and wet typical steppe (Table 3).
Both plant community aboveground biomass (AGB) and PhytOC content varied significantly across sites; these two plant parameters, and soil bioavailable Si content change synchronously with the current-year annual precipitation (Spearman rank correlation coefficient is 1 among these factors). In contrast, the variation in plant community belowground biomass (BGB) and PhytOC content across sites was more correlated with the long-term mean values of environmental factors, such as mean annual precipitation (MAP) and temperature (MAT), soil bulk density, pH and SOC content (Spearman rank correlation coefficient is 1 among these factors).