Comparação dos valores estimados por amostragem na caracterização da estrutura de uma área de floresta na Amazônia com as informações registradas no censo florestal

Abstract

O objetivo deste trabalho foi comparar valores estimados obtidos por amostragem com os valores verdadeiros registrados no Censo Florestal (inventário 100%) de uma área de floresta na Amazônia. Foi simulada uma amostragem sistemática, atendendo às exigências do IBAMA (BRASIL, 2007), com unidades amostrais de 2 ha e intensidade amostral de 14% em uma área de 1.000 ha, que foi submetida a um Censo Florestal. Neste e na simulação do inventário florestal, consideraram-se apenas a população com DAP > 40 cm e uma lista de 60 espécies que foram identificadas como a população de árvores consideradas de valor comercial. Foram avaliados os desvios da abundância, da área basal e do volume por hectare da amostragem em relação à população. Os desvios foram avaliados em relação às espécies individualmente e às espécies agrupadas, de acordo com a classificação de preço utilizada pelo Serviço Florestal Brasileiro. Também foram avaliados os desvios por classe de diâmetro, por grupo e para o total da população. Mesmo com intensidade amostral de 14%, seis espécies (10%) não foram registradas na amostra, resultando em desvios de 614% para mais e 100% para menos em relação à abundância, à área basal e ao volume.

The aim of this work was to compare the estimated values obtained by sampling with the actual values recorded in the Forest Census (inventory 100%) of a forest area in the Amazon. A systematic sampling was simulated, attending the requirements of IBAMA, with 2-ha sample units and sampling intensity of 14% in a 1,000-ha area, which was subjected to a forestry census. The census and simulation of forest inventory considered only the population with DBH > 40 cm and a list of 60 species which were identified as the population of trees considered of commercial value. It was evaluated the deviations of abundance, basal area and volume per hectare of sampling in relation to population. Deviations were evaluated with respect to individual species and species grouped according to the classification of price used by the Brazilian Forest Service. Deviations were also evaluated by diameter class, by group, and the total population. Even with sampling intensity of 14%, six species (10%) were not recorded in the sample, resulting in deviations from more than 614% to more and 100% to less in relation to abundance, basal area and volume. The aim of this work was to compare the estimated values obtained by sampling with the actual values recorded in the Forest Census (inventory 100%) of a forest area in the Amazon. A systematic sampling was simulated, attending the requirements of IBAMA, with 2-ha sample units and sampling intensity of 14% in a 1,000-ha area, which was subjected to a forestry census. The census and simulation of forest inventory considered only the population with DBH > 40 cm and a list of 60 species which were identified as the population of trees considered of commercial value. It was evaluated the deviations of abundance, basal area and volume per hectare of sampling in relation to population. Deviations were evaluated with respect to individual species and species grouped according to the classification of price used by the Brazilian Forest Service. Deviations were also evaluated by diameter class, by group, and the total population. Even with sampling intensity of 14%, six species (10%) were not recorded in the sample, resulting in deviations from more than 614% to more and 100% to less in relation to abundance, basal area and volume.