Answer:
a) tree roots expel carbon into the soil as they grow.
Explanation:
Roots offer physical anchoring to the soil of the tree, with water uptake and inorganic nutrition as its principal activity.
The absorption and the transfer of ions and the growth and maintenance of the roots themselves require energy, therefore releasing CO2 into the ground and into the air.
A diverse ground microbiota exists underneath the earth in addition to the plant roots. Their work results in carbon dioxide being released into the soil, which flows into the air. This soil microbiota is responsible for decomposing the litter and, in general, any dead organic matter in the soil. It may breathe more than half of the total soil respiration. Soil temperature and humidity strongly affect root and microbial activity. In warm and moderately moist soils, soil breathing is highest.
