Spectral characterization of mangrove leaves in the Brazilian Amazonian Coast: Turiaçu Bay, Maranhão State

Flávia Rebelo-Mochel,Flávio J Ponzoni

doi:10.1590/s0001-37652007000400009

Abstract

Mangrove communities are tropical systems which have fewer species than tropical forests, especially in Latin America and display a single architecture, usually lacking the various strata commonly found in other forest ecosystems. The identification of mangrove communities by orbital data is not a difficult task but the most interesting challenge is to identify themselves by the dominant species. The first step toward that floristic identification is the spectral characterization of detached leaves. Leaves from four species of mangrove trees were spectrally characterized considering the Directional Hemispherical Reflectance Factor (DHRF) determined through radiometric measurements using an integrating sphere LICOR 1800 attached to a spectroradiometer SPECTRON SE-590. In the visible bands (0.45-0.69 microm) the button-shaped mangrove Conocarpus erectus was brighter and the red mangrove Rhizophora mangle was darker than the other two species which shows very close DHRF values. Otherwise the black mangrove Avicennia germinans and the white mangrove Laguncularia racemosa can be distinguished from one another in the Near Infra Red (NIR) region (0.76-0.90 microm and in this region of the spectrum the DHRF of C. erectus and R. mangle become very close.

Highlights

Mangroves are valuable coastal systems (Cintrón and Schaeffer-Novelli 1992, Robertson 1992, Lacerda et al 1993)
The mangrove species that occur in this region are Rhizophora mangle, Avicennia germinans, Laguncularia racemosa and Conocarpus erectus, facing estuarine fringes, basins, hypersaline environments, riverine channels and freshwater wetlands
Disregarding the aspects related to the architecture of canopies dominated by these species one should expect when using airborne or orbital data high reflectance values in canopies of C. erectus in the visible bands

Summary

Introduction

Mangroves are valuable coastal systems (Cintrón and Schaeffer-Novelli 1992, Robertson 1992, Lacerda et al 1993) They are known to protect the environment against erosion and flooding, to process pollutants and waste discharge contaminated with heavy metals (Silva et al 1990), to export organic matter to estuarine areas and thereby increasing fisheries yield (Cintrón and Schaeffer-Novelli 1983, Twilley 1985), as to shelter threatened species (Rebelo-Mochel et al 1991, RebeloMochel 1993). The use of Multispectral Scanner (MSS) and TM satellite images to identify mangrove areas along the Brazil coast has previously been accomplished by Herz and Jaskow (1985), Herz (1985), Pires (1986), Pires and Herz (1987, 1988) and Herz (1991). The Atlantic coast of Americas has 3 species of Rhizophora, 2 of Avicennia, 1 of Conocarpus and 1 of Laguncularia

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Methods

Conclusion