L. Eklundh et al., Investigating relationships between Landsat ETM plus sensor data and leaf area index in a boreal conifer forest, REMOT SEN E, 78(3), 2001, pp. 239-251
The aim of this paper is to investigate the feasibility of using Landsat ET
M+ data for the determination of leaf area index (LAI). The investigation i
s prompted by the need for obtaining spatially distributed data on LAI to b
e used as input for carbon modelling of northern boreal forests. Detailed f
ield data have been collected in a coniferous forest area in Uppland, centr
al Sweden, dominated by Norway spruce and Scots pine. A forest canopy refle
ctance model (Kuusk and Nilson, 2000) has been used to simulate stand refle
ctances in the Landsat ETM+ wavelength bands as a means of investigating th
e theoretical reflectance response to LAI changes. The analysis shows that
the response to changes in LAI is strongest in the visible wavelength bands
, particularly Channel 3, whereas only weak response is noted in the NIR ba
nd and for some vegetation indices [simple ratio (SR) and NDVI]. Modelled r
eflectances are influenced by various other factors, particularly ground re
flectance and leaf biochemical properties. Observed reflectances from the L
andsat ETM+ sensor have been compared with reflectance modelling results an
d with field-based LAI estimates. The results indicate that LAI estimation
using inverse canopy reflectance modelling may be difficult, given the larg
e number of input parameters required and the current level of uncertainty
in these parameters. Statistical relationships between LAI and observed ETM
+ reflectances are strongest in ETM+ Channel 7. (C) 2001 Elsevier Science I
nc. All rights reserved.