14.3. LAI (Leaf Area Index)ΒΆ

  • Varies with phenology (state of the vegetation e.g. leaf on or leaf off, bud burst).

  • Measure of the area of leaf surface relative to the ground area. If you look up at an adult, healthy tree there will be typically many layers of leaves between the ground and the top of the canopy. Hence the LAI values are typically greater than 1 \(m^2\ m^{-2}\).

  • Units: \(m^2\ m^{-2}\)

Parameters LAI influences

  • Albedo

  • Roughness length and displacement

  • Aerodynamic resistance

  • Surface/ canopy resistance

  • Surface interception of water

Porosity

If air can blow through an object (e.g. a tree) it is more porous than those one the that air can not (e.g. buildings). The latter are referred to as bluff bodies. Trees porosity may change through the year with phenology. For example, when deciduous plants lose their leaves (fall off) they become more porous.

Modelling of LAI

  • Depends on:

    • temperature (growing degree days)

    • solar radiation/day length

Measurement of LAI

  • Direct measurements

    • Destructive sampling - measuring the area of all the leaves of a tree

    • Collect all the leaves that fall off and measuring their area

  • Indirect measurements

    • Measurements (above and below the canopy) of radiation (e.g. using LAI-2000, LI-COR) which are then used to infer LAI

    • Satellite based products e.g. MODIS

Tip

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  2. Please report workshop manual issues at GitHub Issues. Go from the page with the problem - an automatical link will be inserted. Thanks.