Abstract:
The leaf area index (LAI) product from the Moderate Resolution Imaging Spectroradiometer (MODIS) is important for monitoring and
modelling global change and terrestrial dynamics at many scales. The algorithm relies on spectral reflectances and a six biome land cover
classification. Evaluation of the specific behaviour and performance of the product for regions of the globe such as Australia are needed to assist
with product refinement and validation. We made an assessment of Collection 4 of the MODIS LAI product using four approaches: (a) assessment
against a continental scale Structural Classification of Australian Vegetation (SCAV); (b) assessment against a continental scale land use
classification (LUC); (c) assessment against historical field-based measurement of LAI collected prior to the Terra Mission; and (d) direct
comparison of MODIS LAI with coincident field measurements of LAI, mostly from hemispherical photography. The MODIS LAI product
produced a wide variety of geographically and structurally specific temporal response profiles between different classes and even for sub-groups
within classes of the SCAV. Historical and concurrent field measurements indicated that MODIS LAI was giving reasonable estimates for LAI for
most cover types and land use types, but that major overestimation of LAI occurs in some eastern Australian open forests and woodlands. The six
biome structural land cover classification showed some significant deviations in class allocation compared to the SCAV particularly where
grasslands are allocated to shrubland, savanna woodlands are allocated to shrubland, savanna and broadleaf forest, and open forests are allocated
to savanna and broadleaf forest. The land cover and LAI products could benefit from some additional examination of Australian data addressing
the structural representation of Eucalypt canopies in the “space of canopy realisation” for savanna and broadleaf forest classes.
