Espécies arbóreas presentes na zona urbana de Altamira - Pará: índices espaciais e diversidade florística

Abstract

In recent decades, the interest in studying the urbanization process in cities has become an extremely important subject, since this phenomenon is not planned. Disregarding regional differences, it becomes very distant to design more sustainable cities. One of the ways to achieve this sustainability is by promoting actions that encourage the insertion of afforestation achieving positive effects, such as the alleviation of the heat resulting from asphalting and the implementation of urban spaces. Thus, the promotion of afforestation in cities is one of the ways to minimize the adverse effects of climate in cities and improve the quality of life of the inhabitants. This work was carried out at the headquarters of the municipality of Altamira, located in the southwest region of Pará state. It was performed in three stages: (i) mapping of tree planting from manual vectorization to generate a cloud of points that enabled the analysis through the application of Kernel Density Statistics of the spatial distribution of tree species using calculation of environmental parameters for estimative, such as Vegetation Coverage Index (CVI) and Percentage of Vegetation Coverage (PCV); (ii) acquisition of remote sensing images with low cloudiness during the dry season, referring to the years 2011 and 2021 from the Satellites Landsat 5 Sensor TM and Landsat 8 Sensor Tirs, respectively, with images acquired on National Institute for Space Research (INPE) website; and (iii) survey of tree census in three neighborhoods of the city based on the largest coverage indices calculated in the first stage of the research to determine the Shannon-Weaver, Simpson, and Pielou Equability Indices. It was observed that the distribution of afforestation in Altamira is very variable and deficient, where most of the city's neighborhoods have a tree density deficit. The central neighborhoods are the most consolidated and have the highest densities of individuals. The PCV was 0.49% and the ICVH was 1.72 m² of canopy/inhabitant. Values under recommended by the United Nations Organization - UN and the Brazilian Society of Urban Arborization - SBAU. For the year 2011, the terrestrial thermal conditions in the city of Altamira varied between a minimum of 23.97°C and a maximum of 34.80°C, maintaining a constant around 32°C in the urbanized area, out of line with the maximum temperature 34°C was registered in a few points of the city, with an average temperature of 32.09°C at Centro neighborhood. In 2021, the temperature in Altamira reached a minimum of 23.35°C and a maximum of 33.89°C. The result of calculating the indices for the Premem, Jardim Uirapuru and Esplanada do Xingu neighborhoods showed the following values, respectively: a) Shannon-Weaver diversity (H'): 1.73, 1.81, 2.28; b) Pielou equability (J'): 0.65, 0.57, 0.72, and c) Simpson (C): 0.69, 0.71, 0.85, respectively. Qualitative analysis indicated that the higher the value of C, the lower the diversity of species, therefore, the highest distributed diversity is found in the Premem neighborhood. For the quantitative analysis, 793 tree individuals were cataloged, divided into 61 species, belonging to 40 botanical families which was found that 68% are exotic species and 32% are native. It is observed that the arrangement of the spatial distribution of urban trees did not follow the growth of the urban fabric, allowing the emergence of areas with low tree density which ended up in the urgency of a policy elaboration that contemplates green areas in our city, in order to humanizing roads and public areas and contributing to the regulation of the microclimate in Altamira, with positive effects on the well-being of the population and those who transit through here. Thus, this study has the necessary attributes to support urban planning in actions aimed at promoting comfort and the future attenuation of thermal sensation events, valuing the planting of native species to the detriment of exotic ones.