Verbyla, D. L. 2005.
Assessment of the MODIS Leaf Area Index Product (MOD15) in Alaska
International Journal of Remote Sensing. 26(6):1277-1284.
Abstract. The Moderate Resolution Imaging Spectroradiometer (MODIS) Leaf Area
Index (LAI) Product (MOD15A2) was evaluated for the growing seasons of 2000
through 2004 in Alaska. The LAI estimate may be affected by three factors not
directly related to canopy leaf area: snow melt, cloud contamination and conifer
forest versus broadleaf shrub canopy type. Increases in MODIS LAI values
occurred during the snowmelt period, prior to leaf flush along an elevation
gradient in central Alaska. This false LAI increase prior to broadleaf budburst
could lead to an overestimate of growing season length based on the MODIS
LAI product. During the spring greenup period, there were temporal dips in
MODIS LAI estimates for up to 57% of the pixels. This decrease in MODIS LAI
value was likely due to cloud contamination, despite use of the MODIS quality
control information to select pixels that were cloud-free. The MODIS LAI
algorithm may be sensitive to variation in near-infrared reflectance due to canopy
type rather than leaf area. For example, coniferous boreal forests typically have a
higher LAI than shrub tundra. However, the maximum seasonal LAI estimate
from the MODIS product was consistently higher from shrub tundra areas
compared to coniferous boreal forest areas. There was a strong correlation of the
MODIS LAI estimate with MODIS near-infrared reflectance among conifer and
broadleaf shrub frames. This could lead to overestimates of LAI in areas where
coniferous forest is replaced by broadleaf shrub following wildfire in boreal
forest regions.
Email: D.Verbyla@uaf.edu
Last updated: April 2005