The browser you are using is not supported by this website. All versions of Internet Explorer are no longer supported, either by us or Microsoft (read more here: https://www.microsoft.com/en-us/microsoft-365/windows/end-of-ie-support).

Please use a modern browser to fully experience our website, such as the newest versions of Edge, Chrome, Firefox or Safari etc.

Default user image.

Lars Eklundh

Professor

Default user image.

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

Author

  • Helena Eriksson
  • Lars Eklundh
  • Andres Kuusk
  • Tiit Nilson

Summary, in English

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.

Department/s

  • Dept of Physical Geography and Ecosystem Science

Publishing year

2006

Language

English

Pages

408-418

Publication/Series

Remote Sensing of Environment

Volume

103

Issue

4

Document type

Journal article

Publisher

Elsevier

Topic

  • Physical Geography

Keywords

  • transfer
  • vegetation indices
  • canopy reflectance models
  • leaf area index (LAI)
  • radiative
  • forests

Status

Published

Research group

  • remote sensing

ISBN/ISSN/Other

  • ISSN: 0034-4257