A general Landsat model to predict canopy defoliation in broadleaf deciduous forests

Philip A. Townsend, Aditya Singh, Jane R. Foster, Nathan J. Rehberg, Clayton C. Kingdon, Keith N. Eshleman, Steven W. Seagle

Research output: Contribution to journalArticle

62 Scopus citations

Abstract

Defoliation by insect herbivores can be a persistent disturbance affecting ecosystem functioning. We developed an approach to map canopy defoliation due to gypsy moth based on site differences in Landsat vegetation index values between non-defoliation and defoliation dates. Using field data from two study areas in the U.S. central Appalachians and five different years (2000, 2001, 2006, 2007, and 2008), we fit a sigmoidal model predicting defoliation as a function of the difference in the vegetation index. We found that the normalized difference infrared index (NDII, [Band 4-Band 5]/[Band 4+Band 5]) and the moisture stress index (Band 5/Band 4) worked better than visible-near infrared indices such as NDVI for mapping defoliation. We report a global 2-term fixed-effects model using all years that was at least as good as a mixed-effects model that varied the model coefficients by year. The final model was: proportion of foliage retained=1/(1+exp(3.057-31.483*[NDII baseyear-NDII disturbanceyear]). Cross-validation by dropping each year of data and subsequently refitting the remaining data generated an RMS error estimate of 14.9% defoliation, a mean absolute error of 10.8% and a cross-validation R 2 of 0.805. The results show that a robust, general model of percent defoliation can be developed to make continuous rather than categorical maps of defoliation across years and study sites based on field data collected using different sampling methods.

Original languageEnglish (US)
Pages (from-to)255-265
Number of pages11
JournalRemote Sensing of Environment
Volume119
DOIs
StatePublished - Apr 16 2012

Keywords

  • Change detection
  • Defoliation
  • Gypsy moth
  • Landsat
  • NDII

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    Townsend, P. A., Singh, A., Foster, J. R., Rehberg, N. J., Kingdon, C. C., Eshleman, K. N., & Seagle, S. W. (2012). A general Landsat model to predict canopy defoliation in broadleaf deciduous forests. Remote Sensing of Environment, 119, 255-265. https://doi.org/10.1016/j.rse.2011.12.023