Measuring Leaf Area Index

Leaf area index (LAI) is a dimensionless quantity that characterizes plant canopies. It is defined as the one-sided green leaf area per unit ground surface area (LAI = leaf area / ground area, m2 / m2) in broadleaf canopies.[1] In conifers, three definitions for LAI have been used:

Half of the total needle surface area per unit ground surface area [2]
Projected (or one-sided, in accordance the definition for broadleaf canopies) needle area per unit ground area
Total needle surface area per unit ground area[citation needed]