Knowing how to calculate Leaf Area Index (LAI) the correct way is vital to understanding the photosynthetic output of plants. LAI is the ratio of the upper surface of the leaves of the vegetation divided by the area of the ground covered by the plant. Because leaves usually are stacked and overlap, the LAI often is greater than one. You can employ are a variety of expensive electronic equipment to help you measure LAI. However, you also can calculate the ratio by hand.
Things You'll Need
- Graph paper
- Tape measure
Measure a small section of ground where the plants that you would like to calculate LAI are growing. The smaller the area the less leaves you will have to measure.
Strip all of the leaves off the plants in the area you have measured.
Trace all of the leaves onto graph paper.
Calculate the surface area of all of the leaves by adding all of the squares inside of the tracing lines of the leaves. Convert to centimeters.
Divide the total leaf surface area by the area of the ground from where the leaves were collected.
Tips & Warnings
- Measure a small area of ground so that you don't have to count too many leaves. However, too small a portion will make your LAI statistically invalid. Try to sample between a 6- to 1-foot square area, though the area ultimately will depend on what kind of plant for which you are calculating LAI.
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