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Impact of understory vegetation on forest canopy reflectance and remotely sensed LAI estimates

Eriksson, Helena LU ; Eklundh, Lars LU ; Kuusk, Andres and Nilson, Tiit (2006) In Remote Sensing of Environment 103(4). p.408-418
Abstract
Forest leaf area index (LAI), is an important variable in carbon balance models. However, understory vegetation is a recognized problem that limits the accuracy of sate I lite-estimated forest LAI. A canopy reflectance model was used to investigate the impact of the understory vegetation on LAI estimated from reflectance values estimated from satellite sensor data. Reflectance spectra were produced by the model using detailed field data as input, i.e. forest LAI, tree structural parameters, and the composition, distribution and reflectance of the forest floor. Common deciduous and coniferous forest types in southern Sweden were investigated. A negative linear relationship (r(2) = 0.6) was observed between field estimated LAI and the degree... (More)
Forest leaf area index (LAI), is an important variable in carbon balance models. However, understory vegetation is a recognized problem that limits the accuracy of sate I lite-estimated forest LAI. A canopy reflectance model was used to investigate the impact of the understory vegetation on LAI estimated from reflectance values estimated from satellite sensor data. Reflectance spectra were produced by the model using detailed field data as input, i.e. forest LAI, tree structural parameters, and the composition, distribution and reflectance of the forest floor. Common deciduous and coniferous forest types in southern Sweden were investigated. A negative linear relationship (r(2) = 0.6) was observed between field estimated LAI and the degree of understory vegetation, and the results indicated better agreement when coniferous and deciduous stands were analysed separately. The simulated spectra verified that the impact of the understory on the reflected signal from the top of the canopy is important; the reflectance values varying by up to 18% in the red and up to 10% in the near infra-red region of the spectra due to the understory. In order to predict the variation in LAI due to the understory vegetation, model inversions were performed where the input spectra were changed between the minimum, average and maximum reflectance values obtained from the forward runs. The resulting variation in LAI was found to be 1.6 units on average. The LAI of the understory could be predicted indirectly from simple stand data on forest characteristics, i.e. from allometric estimates, as an initial step in the process of estimating LAI. It is suggested here that compensation for the effect of the understory would improve the accuracy in the estimates of canopy LAI considerably. (c) 2006 Elsevier Inc. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
transfer, vegetation indices, canopy reflectance models, leaf area index (LAI), radiative, forests
in
Remote Sensing of Environment
volume
103
issue
4
pages
408 - 418
publisher
Elsevier
external identifiers
  • wos:000239882000003
  • scopus:33746744383
ISSN
0034-4257
DOI
10.1016/j.rse.2006.04.005
language
English
LU publication?
yes
id
71c27ba0-6f1b-416b-8cce-78249d4af035 (old id 395440)
date added to LUP
2016-04-01 11:53:09
date last changed
2020-01-29 02:22:00
@article{71c27ba0-6f1b-416b-8cce-78249d4af035,
  abstract     = {Forest leaf area index (LAI), is an important variable in carbon balance models. However, understory vegetation is a recognized problem that limits the accuracy of sate I lite-estimated forest LAI. A canopy reflectance model was used to investigate the impact of the understory vegetation on LAI estimated from reflectance values estimated from satellite sensor data. Reflectance spectra were produced by the model using detailed field data as input, i.e. forest LAI, tree structural parameters, and the composition, distribution and reflectance of the forest floor. Common deciduous and coniferous forest types in southern Sweden were investigated. A negative linear relationship (r(2) = 0.6) was observed between field estimated LAI and the degree of understory vegetation, and the results indicated better agreement when coniferous and deciduous stands were analysed separately. The simulated spectra verified that the impact of the understory on the reflected signal from the top of the canopy is important; the reflectance values varying by up to 18% in the red and up to 10% in the near infra-red region of the spectra due to the understory. In order to predict the variation in LAI due to the understory vegetation, model inversions were performed where the input spectra were changed between the minimum, average and maximum reflectance values obtained from the forward runs. The resulting variation in LAI was found to be 1.6 units on average. The LAI of the understory could be predicted indirectly from simple stand data on forest characteristics, i.e. from allometric estimates, as an initial step in the process of estimating LAI. It is suggested here that compensation for the effect of the understory would improve the accuracy in the estimates of canopy LAI considerably. (c) 2006 Elsevier Inc. All rights reserved.},
  author       = {Eriksson, Helena and Eklundh, Lars and Kuusk, Andres and Nilson, Tiit},
  issn         = {0034-4257},
  language     = {eng},
  number       = {4},
  pages        = {408--418},
  publisher    = {Elsevier},
  series       = {Remote Sensing of Environment},
  title        = {Impact of understory vegetation on forest canopy reflectance and remotely sensed LAI estimates},
  url          = {http://dx.doi.org/10.1016/j.rse.2006.04.005},
  doi          = {10.1016/j.rse.2006.04.005},
  volume       = {103},
  year         = {2006},
}