modeling of carbon flow in preserved and degraded

MODELING OF CARBON FLOW IN PRESERVED AND DEGRADED
CAATINGA LANDSCAPE AND AGROECOSYSTEM
D. C. Grilo¹, W. Franca-Rocha¹, E. F. Borges¹ V. G. Petrere²
¹Universidade Estadual de Feira de Santana – UEFS, Feira de Santana, Brazil
E-mail: [email protected], [email protected], [email protected]
²Embrapa Semiárido, Petrolina, Brazil
E-mail: [email protected]
1. INTRODUCTION
The increase in concentration of greenhouse gases, especially those containing carbon, generating environmental
changes very fast. Among the main causes of this concentration is the burning of fossil fuels, both at industrial
and urban level, and the devastation of forest areas, mainly for agricultural use.
Improper land use is a routine practice in the semiarid region of northeastern Brazil. These types of activity drive
high levels of carbon to the atmosphere and reduce the sources sinks. Plants recover the CO2 through
photosynthesis that fix carbon in the biomass of vegetation, and thus constitute, along with their waste, natural
stocks. The caatinga biome stands out for having a high capacity for carbon storage, which makes substantial
relevance to the environment and society [1]. This study aimed to determine the rate of carbon flux in the
different systems through the use of vegetation indexes specialized measures and measurement of vegetation
photosynthetic
2. METHODOLOGY
The study was conducted in the region of Petrolina (Brazil) in experimental fields of agriculture. The landscape is
caatinga, with different forms of anthropogenic and agricultural managements (grazing and planting of mango).
The caatinga is characterized by the occurrence of seasonal drought, with intermittent regimes of rivers and
deciduous vegetation. The biome is dominated by xerophytic vegetation types - dry vegetation, which make up a
warm, rugged landscape. These climatic conditions influence the dynamic photosynthetic and therefore the
phenological traits of endemic plants.
To determine the flow of CO2 was carried out data collection and field investigations to collect information and to
validate the results of digital image processing (DIP). Was used as a spatial database the scene 217/66 Landsat
TM 5, the day 27/11/2010 and 10/06/2011, extracted from the database of INPE.
The indices used were the NDVI index (normalized difference vegetation) and SPRI (Photosynthetic Reflectance
Index rescheduled for positive values). It is possible to determine the flow of CO2 through the integration of those
indexes (NDVI PRI) and this integration measures the efficiency of carbon sequestration [2], [3].
The spectral indices NDVI and PRI are expressed according to equations 1 and 2:
NDVI = (R4 − R3 ) (R4 + R3 )
(1)
PRI = (R1 − R2 ) (R1 + R2 )
(2)
Where Ri is the sensor spectral band of Landsat 5 Thematic Mapper.
Thus, to obtain the flow of CO2 were performed the following processing steps: (a) the generation of the PRI and
NDVI, (b) rescheduling of the PRI, generating SPRI [3] - to eliminate negative values, (c) determining the flow
rate of carbon, made from the multiplication of the two indexes.
3. RESULTS AND DISCUSSION
Carbon sequestration by plants means the process of element removal from the atmosphere through
photosynthesis. The absorption of this element through photosynthetic processes of plants enables the production
of energy necessary for their survival, and provide the removal of greenhouse gas.
In both study periods, which correspond to situations of drought and rain, had, as expected, different behaviors of
carbon efficiency.
During the dry season, the areas with greater vegetative activity, agricultural management, showed the highest
values of CO2 flux, ranging from 0.263 to 0.305 µm, as expressed in Figure 2. The local agencies that regularly
receive nutrients through fertilization and are constantly irrigated. This allows the plants are healthy and therefore
with good conditions to perform their physiochemical activities.
The mango trees, which are an irrigated crop in this industry are large-sized trees that have an enormous capacity
to absorb carbon depending on the amount of leaves in each individual and the size of their leaf area. At planting,
the dry period showed a similar behavior to the rainy season in relation to carbon flux. There was little variation
in leaf structure of plants, since they did not suffer severe water stress.
The spectral behavior of the mango crop at the two stations were similar. There was a high reflectance in band 4
of the TM sensor (from 0.76 to 0.90 µm), spectral range that expresses well the vegetation, due to the
morphostructural features of the mango crop, especially its leaves with high chlorophyll. In addition, the red side
of the TM, was pointing to a high absorption and dense green vegetation.
These characteristics of absorption and reflection bands proved to be mapped, reaching high values of the flow of
CO2, representing areas with blue colors at the image below (Figures 2A and 2B).
In contrast, areas of Buffel grass showed the lowest CO2 streams, such as stress figures 1A and 1B. Even in the
rainy season the grass was shown with the lowest flow, excluding the areas of exposed soil. In the dry season, the
cultivation of irrigated showed a high water stress. The grass recorded a high absorption in the near infrared, as is
elucidated in Fig 1A. Thus, the low reflectance in band 4, influence the result of low carbon flux. The band
showed a red reflectance greater than the infrared region, influencing the flow rates recorded.
During the rainy season the reflectance values are presented in relation to distinct dry season. The graph in Figure
1B shows an absorption in band 3 and a reflection in the near infrared region due to grazing have become more
healthy, with no water restrictions. Figure 1 below shows the pasture healthy.
Figure 1 - Spectral Signature of grazing (A) dry and (B) rainy season
The preserved and disturbed parts of the caatinga had different carbon efficiency behavior due to seasonality.
In the dry season, both plots reported carbon fluxes lower than irrigated handling areas. This is justified by the
characteristic of most plants of the caatinga, losing their leaves in order to adapt to semiarid state, as shown in
Figure 2A. Consequently, these plants under stress are limited in the performance of photosynthetic activities. The
the image of Figure 2A outlines this state of reduced photosynthetic activity. The plants exposed to water stress
showed a high flow values ranging from 0.186 to 0.305 µm.
However, the rainy season in these areas had a higher efficiency of carbon flux, resembling areas of irrigated
crop, as indicated in Figure 2 B.
What was observed is that in a state of climax caatinga showed an increase in the rates of carbon absorption.
Nevertheless, there was a diversity of values in the plots. The area had preserved even in the rainy season, sites
with low flow rates, due to the structure of plants, which have small leaves. Already degraded caatinga low values
are directly linked, not only the characteristics of the plant, but especially to the locations of exposed soil, due to
the spacing between the plants.
Figure 2: Image of the flow of CO2 (A) dry and (B) rainy season
4. CONCLUSIONS
Through the calculated indices NDVI and SPRI could be measure the locations that have a higher flow of CO2,
which correspond to areas where plants have more leaf area and lower water stress.
Despite the growing areas have a higher efficiency of carbon flux, it is important to note that the maintenance of
vegetation is configured as the best alternative for reducing carbon emissions to the atmosphere, because these
areas have large storage of this element.
The results show that studies on the spectral behavior of the caatinga vegetation types help us to identify features
associated with carbon flux.
5. REFERENCES
[1] V. Giongo, Carbono no Semiárido Brasileiro. In: XVIII Reunião Brasileira de Manejo e Conservação do Solo e da Água, 2010,
Teresina. Viçosa : Sociedade Brasileira de Ciência do Solo, 2010.
[2] A.F. Rahman, J.A. Gamon, D.A. Fuentes, D. Prentiss, H. Qiu, Modeling CO2 Flux of Boreal Forests Using Narrow-Band Indices From
Aviris Imagery. Aviris Workshop, JPL/NASA, Pasadena, Califórnia, 2000.
[3] G. M. M. Baptista, Validação da Modelagem de Seqüestro de Carbono para Ambientes Tropicais de Cerrado, por Meio dos Dados
Aviris e Hyperion. In: XI Simpósio Brasileiro de Sensoriamento Remoto, Belo Horizonte. Anais em Cd-Rom. São José Dos Campos:
INPE, 2003.
[4] P. C. F. Lima, R. A. Seitz,. Comportamiento Silvicultural de Especies de Algarrobo en Petrolina - Pe, Región Semiárida de Brasil. In:
Congresso Latinoamericano Iufro, 1998