Navegando por Palavras-chave "Vegetation structure"

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    Caracterização de manguezais: relação entre unidade amostral e estrutura da vegetação
    (Universidade Federal de São Paulo, 2016-05-23) Medeiros, Aline Silveira [UNIFESP]; Christofoletti, Ronaldo Adriano [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    The mangrove ecosystem is characterized by occupying coastal areas in regions close to the tropics, being subjected to high salinity and temperature conditions, tides action and low oxygen concentration. This environment has important ecological and economic functions, such as organic matter production; protecting the coast against natural phenomena; providing food and habitat for endemic and from other environments species; providing products for human populations. Different anthropogenic impacts have led to changes in this ecosystem, and with its increasing loss, it is necessary to identify efficient means for studies on the characteristics of this vegetation, which have highest accuracy and precision and that, in contrast, require the shortest time possible. Facing this issue, this study examines the size of sampling units to estimate structural parameters of the mangrove trees species populations, as well as the community, considering relative standard error as precision indicator, the relative disparity as accuracy indicator and the Wiegert?s product as best ratio cost (time) - data variance indicator. The relative standard error tended to continuously show itself pursuant to the variation in the sampling unit size. On the other hand, the relative disparity tended to be reduced by the growth of the sampling unit, being lower than 5% for units exceeding 625 m². Considering Wiegert?s product for the characterization of mangroves which structure and composition are similar to this study, the use of sets of 225 m² sampling units was more suitable. The characterization of a 1600 m² area by two 225 m² units (that is to say, sampling 28% of the total area) provided a disparity from 5% to 13%. Considering that many times the use of large areas is sought, preventing a sample that represents 28% of the total study area, it must be considered that estimates? accuracy in most cases will be lower, with disparities above the range 5% to 13%. The accuracy achieved, therefore, is limited by cost and extension of the area studied.