The fraction of a tree's mass that consists of atoms taken from the atmosphere is primarily composed of carbon, as trees undergo photosynthesis to convert carbon dioxide from the atmosphere into organic compounds. However, it's important to note that trees also acquire nutrients from the soil, which contributes to their overall mass.
During photosynthesis, trees use energy from sunlight, water from the ground, and carbon dioxide from the air to produce glucose (a sugar) and oxygen. The glucose is then used as a building block to synthesize more complex organic compounds, such as cellulose, lignin, and other components of the tree's structure.
The carbon in the glucose molecule originates from carbon dioxide (CO2) in the atmosphere. Through a series of chemical reactions, carbon dioxide is converted into organic carbon compounds. The oxygen released during photosynthesis is released back into the atmosphere.
The specific fraction of a tree's mass that is derived from atmospheric carbon can vary depending on the tree species, environmental conditions, and other factors. However, on average, it's estimated that roughly 50% of the dry mass of a tree comes from carbon acquired from the atmosphere during photosynthesis.
It's worth noting that trees also take up other essential elements and nutrients from the soil, such as nitrogen, phosphorus, potassium, and various micronutrients. These elements contribute to the overall mass and composition of the tree but do not come directly from the atmosphere.
In summary, approximately 50% of a tree's dry mass consists of carbon that was originally acquired from the atmosphere through the process of photosynthesis. The remaining mass is derived from other nutrients and elements obtained from the soil.