this region is characterized, according to Koppen classification,
as Cwa — mesothermal with dry winter. Its soil is characterized
as Latosolo (Oliveira et al., 1999). The area has plan
topography with no soil variations, resulting in a great
environmental homogeneity. Between the two dates of the study
(May 14" and June 17?) is observed the decrease of average
rainfall (21.6mm — last 12 years), average temperature (1.0°C —
last 19 years) (CIAGRO, 2012) and photoperiod (17.0min —
last year) (APOLOI1 1, 2011).
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Figure 1. Study area location
Those three stands of the study area were projected with eight
trees each line, 3.0m spacing between trees, and 7.0m line
spacing, totaling 40 individuals for each stand. They were
planted in 1988 and nowadays they are in maturity. According
to Gonçalves (1998), the PB235 clone is a secondary Malayan
clone, which is a result of the primary clones crossing - PB 5/51
x PB S/78. The adult trees reveal a homogenous branch
formation, and the leaves are green with intense coloring. In the
other hand, the GT1 clone is a primary clone developed in the
rubber tree plantation called Gondang Tapen, in Java,
Indonesia. The canopy opening is very late and it has a variable
habit. The leaves, during the immaturity period, are big, dark-
green and bright, and are smaller when they reach the maturity
period.
According to the environmental data exposed above, it is
possible to observe that the only environmental heterogeneity
among the studied stands is the insolation difference. The stand
located near Northwest (clone PB235) is exposed to the sun in
two faces, and its plantation lines, which are closer to the west,
receive full lighting in the afternoon. Therefore, the stand of the
GTI clone, central, is environmentally closer to the Southeast
stand of the PB235 clone. In order to distinguish the stands of
the PB235 clone, the qualifications PB235-NW and PB235-SE
were applied during this work.
2.2 ProSpecTIR-VS hyperspectral sensor and processing
The ProSpecTIR-VS sensor works using two imaging
subsystems: one is in the Visible/Near infra-red region —
VIS/NIR (400-990nm), and the other is located in the
Shortwaves infra-red region — SWIR (970 a 2,500nm), called
Eagle and Hawk, respectively. This sensor, when operating in
Brazil, was placed on board of SPECTIR/FOTOTERRA
company's airplane. The images obtained for this research
presents 357 channels, with about 5nm each, distributed along
the VIS/NIR (125) and SWIR (238) regions, and with 1.0m of
spatial resolution. The imaging process happened in May, 14^
2010 and in June, 17" 2010. The data were delivered to the 1A
processing level and with UTM 23S projection system and
WGS 84 datum.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
The reflectance images were georeferenced from their
respective GLT (Geographic Lookup Table) files. Polygons
were generated over the images obtained on both dates (May
14^ and June 17") from the three rubber plantations’ stands:
PB235-NW, GT1 e PB235-SE.
Spectral libraries were created using the average behaviour of
each stand for each studied date.
2.3 ASD FieldSpec-3 Hi-Res spectrometer and processing
The ASD FieldSpec-3 Hi-Res spectrometer detects
electromagnetic radiation during the spectral interval from 350
to 2,500nm, and has high resolution (1,250 channels), of which
500 channels in the range from 350 to 1,000nm with a 1.4nm
sampling interval and 750 channels that cover the range from
1,000 to 2,500nm, with a 2.0nm sampling interval.
For the collection of the photosynthetically active leaves, one
individual was selected for each plantation line and, randomly,
the leaves which occupied the canopy were collected. At the
research laboratory unit, we measured five leaves/tree, of which
the averages spectra were extracted. This process was done one
year after the images were obtained, in May 18" and June 17",
2011.
The average spectra for each stand and month were resampled
for the 357 bands of the ProSpecTIR-VS airborne sensor.
The spectral behaviour of the targets at canopy and leaf level for
May and June were compared to some spectral data generated
by specialists, such as Barret (1999) and Blackburn (2007). In
order to enhance the spectral differences between the clones and
the stands, considering the sun exposure heterogeneity, ratios
were applied between spectra.
3. RESULTS AND DISCUSSION
3.1 Visible — VIS (400-700nm)
The spectral variations in both work scales show that, between
600 and 700nm, the GTI clone presented the greatest losses of
a and b chlorophylls, from May to June (Figures 2 and 3). The
spectra present significant differences, mainly in this region,
once in the GTI clone canopy, in June. In this moment the GTI
clone shows ubiquitous presence of reddish leaves with
advanced senescence, highlighting the response of the carotenes
with the approach of winter.
Even so in different shading conditions, in leaf scale and in this
spectral region, it is possible to observe a similarity between the
stands of same clone, PB235-NW and PB235-SE (Figure 3).
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Wavelength (nm)
Figure 2. Spectral behaviour in canopy scale from 600 to
700nm, for May and June, of the Rubber trees stands: GTI,
PB235-SE and PB235-NW
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