Photosynthesis & respiration

We have been busy working on our research projects. We completed our transplant experiment, which we like to call our little garden. We have planted grass, two different species of moss, and a cyanobacteria. In the coming years, we will check their progress and measure how the soil beneath them is changing.

Recently, we have been busy measuring photosynthesis and respiration from plants and soil. This is how we can describe how “busy” they are. When plants photosynthesize, they take up CO

₂ from the atmosphere and lock it away inside the plant. Respiration is the opposite process, where the carbon inside of organisms is released back to the atmosphere as CO₂. (Even humans release CO₂ when we respire. When we breathe, we take in oxygen and release CO₂.) To measure how active our plants and soil are, we measure how much CO₂ is taken up by photosynthesis and how much is released by respiration. This is how we can measure the amount of carbon moving into and out of the soil ecosystem. We want to know which plants photosynthesize the most. We also want to learn whether the microorganisms living in the soil respire more when they live under certain plants.

To do this, we use an infrared gas analyzer. That’s a fancy name for a machine that uses infrared light to measure the concentration of CO₂. We place the chamber on top of the plants and soil to trap the atmosphere inside. If the plants are photosynthesizing, the CO₂ in the chamber will start to decrease, because plants take up CO₂. If we use a dark chamber like in the photo below, photosynthesis will stop. But if the plants and microbes are respiring, the CO₂ inside the chamber will increase, because we all exhale CO₂ when we breathe.

We have measured plant photosynthesis and soil respiration from all of our study plants in all of the stages of succession. So we have done a lot of hiking to all of our sites where we find the different stages of succession. We get very tired, but we have a lot of data now!