**4. Used data**

188 Biodiversity Loss in a Changing Planet

The vegetation cover consists predominantly of UUES *cerrado stricto sensu*, but other types of vegetation, e.g. *campo cerrado* are also found. The *cerrado sensu stricto* in this area is composed

The UUES located in the plateaux sub-region (scarps that resulted from the erosive action of waters) in the Cerrado of the Southwest of Piauí, within the boundaries of the cities of Baixa Grande do Ribeiro and Santa Filomena, about 730 km from Teresina, the State capital. Fig. 2

The average altitude of the plateau in the UUES is 620 meters. With a typically tropical climate, this area has high average temperatures, varying between 24 and 26 ºC, with absolute maximum annual reaching 40 °C. The relative humidity of air oscillates between 60 and 84% and the average annual precipitation levels are below 800mm. Regarding its physiography Piaui is a typical zone of transition, i. e., a mixture of biomes such as the *Caatinga*, the *Closed Deciduous Forest* and *Cerradão*. Finally, the aforementioned economies of the two municipal districts are predominantly agricultural, particularly grain production,

The fire is usually used to clean lands, e. g. the preparation for planting or pasture. According to Medeiros (2002), a forest fire is a fire that starts in several types of vegetation, running out of control, which can be intentionally started or have natural causes such as sunlight. Large forest fires can be considered a serious threat to biodiversity conservation and the maintenance of ecological processes. This threat is particularly serious for small areas, sections isolated by cities or agricultural monocultures and areas with rare and/or

The risk and intensity of damage are vary depending on the size of the area, age, intensity of the fire and time of year. Fires have been a matter of continuous concern in the dry season, when most of the damage to the ecosystem could be experienced in cities located in the

endangered species, because these ecosystems are very susceptible to fire.

referred area, which were covered by smoke and ash (Medeiros, 2002).

of grasslands, with dense cover of grass and low trees.

Fig. 2. Location of the Uruçuí-Una Ecological Station

such as soybean and corn (Medeiros & Cunha, 2006).

**3. Forest fire** 

shows the location and boundaries of UUES.

The scanner Thematic Mapper (TM), coupled in Landsat 5, sense data in seven spectral bands simultaneously. Band 6 senses thermal infrared radiation and can only acquire night scenes. The resolution on the ground (spatial) in bands 1-5 and 7 are 30 square meters and in band 6 is 120 square meters.

Bands 1 (blue, 0.45-0.52m), 2 (green, 0.52-0.60m) and 3 (red, 0.63-0.69m) are obtained in the waves lengths of the visible in the electromagnetic spectrum; while the bands 4-7 are collected in infrared region (4 - infrared near, 0.76-0.90m; 5 – infrared medium, 1.55- 1.75m; 6 – infrared thermal, 10.4-12.5m; and 7 – infrared medium, 2.08-2.35m). Additional information on program Landsat can be seen in NASA (2011).

Only bands 3 and 4 were used in the experiments conducted in this paper. Band 2 was only used in the generation of the color composition (Fig. 3). An image was obtained in the quarter ASO (August, September and October) of every studied year, which corresponding to the drought periods. This study comprises the years 1985, 1987, 1989, 1996, 1998, 2000, 2007, 2008 and 2010, in agreement with the readiness of TM data and with the occurrence of the climatic phenomena El-Niño and La-Niña. Fig. 3 shows the UUES in 1989.

Fig. 3. Image of the UUES area in 1989

Identification and Analysis of Burned Areas in Ecological Stations of Brazilian Cerrado 191

The areas corresponding to the "burned" features are identified in the IR and NDVI images (Fig. 4a and 4b). Due to the spectral characteristics of this feature (burned), the digital values in the NDVI image are negative and close to value -1. So, a threshold T is empirically established to isolate the burned areas from the other features in the image. All digital values of the NDVI image smaller or equal to T are labeled as belonging to the feature "burned", and the others (>T) as "unburned". The same procedure is used in IR imaging,

The resulting images of threshold T and T1 applications are submitted to convolution with the morphological operator "opening", aiming to eliminate the noise in T and T1 operations. The opening of NDVI or IR images by operator B (structuring element) is obtained by the erosion of these images with B, followed again by dilation of the resulting image by B. The mathematical representation of the morphological operation with the NDVI image is given

 NDVI о B = (NDVI B) B (2) The structuring element B can be defined in many ways: linear, circular, rectangular or diagonal. The entire process involved in the identification of burned areas is accomplished by routines developed in MatLab2007a. Finally, the burned areas obtained from the NDVI and IR images are added (arithmetic operation), to fill up spaces that were not visible with

The classification of vegetation types affected by forest fires within the study area (UUES) is done by *in loco* visits. The present study was conducted by a group of researchers and members of ICMBio (Chico Mendes Institute for Biodiversity Conservation) responsible for monitoring the UUES. The group crossed the UUES, passing through a rural road towards

Some central points of the burned areas detected in the digital images are used as reference in the collection of information concerning the type of vegetation in this area. In each point,

(a) (b)

Fig. 4. Near infrared band - IR (a) and NDVI image (b)

**5.3 Identification of burned areas in digital images** 

but the magnitude of new threshold is T1.

by equation 2.

the use of other techniques.

**5.4 Classification of the Biome in UUES** 

the North and the South, and used also a side access road.

Imaging processing is performed using the software MatLabR2007a, Multispec3.2 and Envi4.2.
