Measuring biomass changes due to woody encroachment and deforestation/degradation in a forest-savanna boundary region of central Africa using multi-temporal L-band radar backscatter

E. T.A. Mitchard*, S. S. Saatchi, S. L. Lewis, T. R. Feldpausch, I. H. Woodhouse, B. Sonké, C. Rowland, P. Meir

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

176 Citations (Scopus)

Abstract

Satellite L-band synthetic aperture radar backscatter data from 1996 and 2007 (from JERS-1 and ALOS PALSAR respectively), were used with field data collected in 2007 and a back-calibration method to produce biomass maps of a 15000km2 forest-savanna ecotone region of central Cameroon. The relationship between the radar backscatter and aboveground biomass (AGB) was strong (r2=0.86 for ALOS HV to biomass plots, r2=0.95 relating ALOS-derived biomass for 40 suspected unchanged regions to JERS-1 HH). The root mean square error (RMSE) associated with AGB estimation varied from ~25% for AGB<100Mgha-1 to ~40% for AGB>100Mgha-1 for the ALOS HV data. Change detection showed a significant loss of AGB over high biomass forests, due to suspected deforestation and degradation, and significant biomass gains along the forest-savanna boundary, particularly in areas of low population density. Analysis of the errors involved showed that radar data can detect changes in broad AGB class in forest-savanna transition areas with an accuracy >95%. However, quantitative assessment of changes in AGB in Mgha-1 at a pixel level will require radar images from sensors with similar characteristics collecting data from the same season over multiple years.

Original languageEnglish
Pages (from-to)2861-2873
Number of pages13
JournalRemote Sensing of Environment
Volume115
Issue number11
DOIs
Publication statusPublished - 15 Nov 2011
Externally publishedYes

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