Abstract: Differences in utilization patterns affect the carbon cycle of grassland ecosystems. Evaluating the carbon sequestration capacity of grassland ecosystems under different utilization patterns will help to establish relevant ecological management strategies, and so have practical significance for mitigating greenhouse gas emissions from grasslands. Based on a field survey and laboratory tests, the carbon sequestration capacity of two typical grassland types (WT: warm temperate tussock, and WS: warm temperate shrub-tussock) under four utilization patterns (FUG: fenced and unexploited grassland, SMG: scattered grazing+mown grassland, SGG: seasonally grazed grassland and AGG: all-year-grazed grassland) in Henan Province were studied. The results indicated that no difference was found in the vegetation biomass of WT (P>0.05). However, the vegetation biomass of WS under SMG was significantly greater than that of FUG and AGG (P<0.05). Under FUG, the vegetation biomass of WT was significantly greater than that of WS (P<0.05). No significant difference existed in the underground and root carbon density between WT and WS (P>0.05). With respect to the carbon density of vegetation (shoot+root), the management regimes ranked: FUG>SMG>AGG>SGG (2187.93-4211.56 g C·m^-2) in WT. However, the soil carbon density of WT under SGG (13369.07 g C·m^-2) was significantly greater than that of FUG (2544.25 g C·m^-2) (P<0.05). For WS, the root carbon storage was no significant difference among them (P>0.05). For all utilization patterns, the root system was the major contributor to vegetation carbon density in both WT (87.42%) and WS (81.52%). With respect to the carbon density of the total grassland ecosystem, soil C (excluding roots), accounted for 91.72% and 84.98% of total C in WT and WS, respectively. Hence, soil carbon density was the major factor determining carbon sequestration capacity of both types of grassland, under all utilization patterns. This study provides scientific data to assist with rational allocation of grassland resources and for accurate assessment of carbon sequestration capacity of Henan grasslands.

Key words: utilization pattern, warm-temperate (shrub) tussock, biomass, carbon density, carbon distribution