AimsThe grassland in southwestern China is mainly warm and tropical grass and shrub grassland, accounting for approximately one-tenth of the national grassland area. Analysis of the relationship between shrub coverage and the grassland carbon pool and its composition is of great significance for accurately assessing carbon storage in the southwestern grassland, which grassland is still in the secondary succession stage.
MethodsIn a field investigation, 41 representative plots of different geomorphic types in southwestern China were divided into three types according to shrub coverage: no shrub grassland community (shrub coverage is 0), low shrub coverage grassland community (shrub coverage is 0-10%) and high shrub coverage grassland community (shrub coverage is 10%-30%). Carbon density was calculated by measuring the aboveground and underground biomass and litter biomass of grassland communities at different shrub coverage levels, as well as plant and soil carbon content.
Important findings The results showed that with increasing shrub coverage and species richness in grasslands, the ecosystem vegetation carbon density increased from 0.304 kg·m ^-2 to 1.574 kg·m ^-2, and the roots and litter carbon density also showed growth trends. The soil carbon density increased from 7.215 kg·m ^-2 to 9.735 kg·m ^-2, and the ecosystem carbon density increased from 7.519 kg·m ^-2 to 11.309 kg·m ^-2, with increasing shrub coverage. Regarding the composition of the grassland carbon pool, the soil carbon pool of the low shrub coverage grassland accounted for the smallest proportion of the ecosystem carbon pool. In summary, the increase in shrub coverage changes the composition of the grassland ecosystem carbon pool and leads to an increase in the amount of ecosystem carbon. Therefore, when estimating the grassland ecosystem carbon pool, it is necessary to overall plan for and take into account the changes in grassland shrub coverage in southern China.