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DYNAMICS OF RADARSAT BACKSCATTERING VALUES RELATED TO PRIMARY AND
SECONDARY FOREST BIOMASS STRUCTURE IN SW AMAZONIA, BRAZIL.
Joäo Roberto dos Santos*
Hermann Johann Heinrich Kux*
Maria Silvia Pardi Lacruz*
Frank J. Ahern**
Ron W. Pietsch**
* Instituto Nacional de Pesquisas Espaciais-INPE
CP. 515 CEP. 12227-010 Sáo José dos Campos - SP. - Brasil
Fax.: +55 12-345 6449 jroberto(a)ltid.inpe.br
**Canada Centre for Remote Sensing - CCRS
588 Booth Street, Ottawa, Ontario KIA 0Y7
Fax.: 613-947 1385
ahern@ccrs.nrcan.gc.ca
Commission VII, Working Group 6
KEY WORDS: biomass, tropical rainforest, secondary succession, RADARSAT, Amazonia, monitoring.
ABSTRACT
The principal objective of this study is to evaluate the relations among the Radarsat backscatter and biophysical parameters,
(biomass), of primary and secondary forest. Another objective is to analyze the usefulness of this SAR sensor system to discriminate
among the land cover classes of the region surrounding Rio Branco (Acre State, Brazil). Two RADARSAT scenes at begin of dry
and wet seasons were used. This dataset underwent the following pre-processing: reduction of speckle, scaling of data from 16 to 8
bits real integer, and extraction the backscattering values (linear Y? unities). Afterwards these scenes were registered to a TM-Landsat
image to improve the identification of the classes: primary forest with and without bamboo; initial, intermediate and advanced
natural regrowth; pasture at distinct phenological conditions and burned areas. Ground control campaigns were performed to acquire
dendrometric data (DBH and height of the arboreal individuals) in several plots of the primary and secondary forest. The biomass
was estimated by the most adequate allometric equations for each vegetation type. Furthermore, diagrams of the biomass from
primary and secondary forest are presented and discussed together with the seasonal backscatter signals. The multitemporal analysis
of Radarsat data shows the behavior of the dynamics of other land cover from this area.
1. INTRODUCTION
At SW Amazonia there has been, in the last few years, a gross
annual deforestation rate of about 1,200 Km?/year
(INPE/IBAMA, 1998). The non-controlled deforestation of this
region is very detrimental for any policy related to the self-
sustainable development of this region. Several studies (Keil et
al.,1996; Schmidt et al., 1997) on this issue have been made
with data obtained from both optical (TM/Landsat) and
microwave (ERS-1, SIR-C and more recently JERS-1) sensor
data. The environmental monitoring in Brazil has been
conducted with remote sensing data, which has allowed studies
on the evaluation of such sensor data for the analysis of land use
dynamics and biomass changes within a defined region. Within
this frame the objective of this study is to evaluate the relations
among the RADARSAT backscattering values and biophysical
parameters (biomass) of primary and secondary forest. The
others intents are to analyze the seasonal variations based on
backscatter data and to show the usefulness Radarsat to
characterize other landuse classes.
2. DESCRIPTION OF STUDY AREA
The area under study (S 9? 35' - S 10° 20° and W 67° 40° - W
68° 15°) includes a section along the highway Xapuri - Rio
Branco - Sena Madureira and Rio Branco - Humaitá
Colonization Project (PAD) in Acre State, Brazil (Figure 1).
This region is covered by ombrophilous tropical rainforest (with
or without bamboo formations) and by anthropic areas like
pastures and secondary succession areas. The commercial
interests in Acre State are directed towards rubber tapping from
Hevea Brasiliensis, and exploration from Brazil nuts. More
recently, since the opening of the BR-364 road, large
deforestation activities took place for cattle raising and selective
logging. Geological, geomorphologic and edaphic descriptions
from this region are found in BRASIL (1990). The dry season
starts by April/May and continues until the end of September.
Figure 1. Section of the area under study in a color composite of
TM/Landsat and RADARSAT images.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 527
