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).