How do Plants Capture Carbon?
Trees as well as all other plants produce their own food through a process called photosynthesis. Photosynthesis uses the energy from sunlight, water from the soil and CO2 from the air to produce a simple sugar and oxygen. The sugar is then transported through tubes in the leaf to the roots, stems and fruits of the plants.
Research has shown that in most cases rate of plant growth under otherwise identical growing conditions is directly related to the level of carbon dioxide concentration.
The amount of carbon dioxide a plant requires to grow may vary from plant to plant, but tests show that most plants will stop growing when the CO2 level decreases below 150 ppm. Even at 220 ppm, a slow-down in plant growth is significantly noticeable.
Colorado State University conducted tests with carnations and other flowers in controlled CO2 atmospheres ranging from 200 to 550 ppm. The higher CO2 concentrations significantly increased the rate of formation of dry plant matter, total flower yield and market value. See http://homeharvest.com/carbondioxideenrichment.htm
In a related study, to test how a CO2-enriched atmosphere will actually affect the environment, the researchers at Duke University Nicholas School of the Environment and Earth Sciences bathed test plots within a growing loblolly forest near Duke with computer-controlled levels of the gas expected in the air worldwide by mid-century. This same experiment was performed by Oak Ridge National Laboratory in plots of sweetgum-dominated woodlands in eastern Tennessee. At both the Duke and Oak Ridge test sites the extra carbon dioxide is released from arrays of tower-mounted valves that are computer-controlled to ensure reliable concentrations regardless of wind direction.
During the first three years of these continuing seven-year experiments, the extra CO2 boosted overall pine growth by 25 percent and sweetgum production by 21 percent, according to the "Science" report.
Fortunately for us, plants often produce more food than they need, which they store in stems, roots, seeds or fruit. We can obtain this energy directly by eating the plant itself or its products, like berries, carrots, tomatoes, rice or potatoes.
Carbon dioxide in the atmosphere is incorporated as fixed carbon into the roots, trunk, branches and leaves of trees, with roughly 50% of tree carbon storage occurring in the woody biomass. The shedding of leaves does not constitute a large carbon release, as only 3% of tree carbon storage occurs in foliage, and most will be absorbed by the soil. Carbon is released to both the soil and the atmosphere when the biomass decays.
Photosynthesis is the first step in the food chain that connects all living things. Every creature on earth depends to some degree on green plants. The oxygen that is released by the process of photosynthesis is an essential exchange for all living things.
Forests have been called the "lungs of the earth" because animals (and humans) inhale oxygen and exhale carbon dioxide in the process of breathing, and plants take in carbon dioxide and give off oxygen in the process of photosynthesis. Additionally, forests are also important ecological habitats for many other plants, insects, and animals.