Leaf area index
（重定向自Leaf area ratio）
![](/Images/godic/202501/23/LAI_Respiration0527.gif")
![A hemispherical photograph of forest canopy. The ratio of the area of canopy to sky is used to approximate LAI.](/Images/godic/202501/23/Hemiphoto_monarch_habitat10527.jpg")
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, m / m) in broadleaf canopies. In conifers, three definitions for LAI have been used: