Abstract: The process of CO2 entering the plant through photosynthesis was divided into two phases: plant absorption and soil fixation. It had been studied that the capacities of these four samples, which were Vulpiamyuros, Vicia villosa Roth, rapeseed and natural grass, absorbing CO2 through photosynthesis and that the variation of organic carbon amount in soil. And we also did some work on loss of biomass, carbon amount in early and last resudue decomposition. The result showed that Vicia villosa Roth had the most powerful capacity in carbon absorbing, which reached 3596.7-4822.3kg·ha⁻¹·y⁻¹. The remaining carbon should be the most after three months of cutting, clustering and decomposing and could reach a value of 1164.55-2529.97kg·ha⁻¹. Rapeseed had the highest value of carbon emission in the four plants, which reached the average of 5679.75kg·ha⁻¹ and the highest of 6316.67kg·ha⁻¹ which was 1.56 times as much as the CK. The quantity of fixed carbon in the soil covered by rapeseed was the highest of 4790.75kg·ha⁻¹·y⁻¹, which was 1.4 times more than the CK. This thesis can be used as an instruction for selecting right ground plants in jujube orchard and also be useful for decreasing carbon dioxide from air to come to the carbon neutral.

Key words: Carbon sink, Climate change, Ground cover, Soil organic carbon