How do trees contribute to carbon sequestration?

Trees play a crucial role in carbon sequestration primarily through the process of photosynthesis. During photosynthesis, trees absorb carbon dioxide (CO2) from the atmosphere. This CO2 is then used to create sugars, which serve as energy sources for the tree and are also incorporated into the tree’s structure, including its trunk, branches, leaves, and roots. This process effectively removes carbon from the atmosphere and stores it in the tree's biomass, thus helping to combat climate change by reducing the overall concentration of greenhouse gases.

While other options may describe important ecological functions of trees, they do not directly relate to the process of carbon sequestration. For instance, releasing oxygen during photosynthesis is a byproduct of carbon absorption but not the mechanism by which carbon is sequestered. Preventing soil erosion and conserving moisture are beneficial environmental functions of trees, but they do not impact carbon storage directly. Lastly, promoting the growth of smaller plants is an indirect benefit of tree growth, as larger trees can create a habitat conducive to the survival of undergrowth, but it does not address how trees sequester carbon specifically.

Thus, the primary function involved in carbon sequestration is the absorption of carbon dioxide, making the first option the correct choice in this context