As we know that the plants is universal producer.Plant absorb CO2 from atmosphere by the help of photosynthesis from where plant make glucose ,oxygen and energy and then plant exhale O2 but in plants there is another process is going on called respiration which exhale same amount of CO2 as consumed in photosyntesis and in autumn the leaves fall on the soil which on later decomposed and release carbon dioxide this whole cycle is called carbon cycle !!
