Estrutura de florestas secundárias nos sistemas de manejo com e sem queima em Igarapé - Açu, Pará.

Abstract

The use of fire to prepare an agricultural area results in the elimination of organisms from the soil and significant losses of nutrients, impairing carbon sequestration and storage, essential functions for global climate regulation. An alternative to replace this practice is the method of cutting and grinding vegetation, which maintains a dense layer of organic matter on the soil surface, providing coverage and protection against erosion. In this sense, the work aims to evaluate the influence of the area preparation method in the Traditional (Cutting and Burning) and Alternative (Cutting and Crushing) Systems on the regeneration of capoeira, in the years 2016 and 2022, located in Igarapé-açu. A survey of tree regeneration was carried out in three preselected areas, called cut and burn (CQ), cut and crush (CT) and forest as reference (R) with sizes of 2 ha each. 10 plots were installed in the areas of CQ, CT and R, with dimensions of 10 m x 10 m each, arranged systematically. Data collection was carried out in August 2016 (3-year secondary forest) and 2022 (4-year secondary forest), and included all individuals with a diameter at breast height - DAP≥2.0 cm. To estimate the total height (HT) of individuals, visual estimates were applied. The inventoried individuals were locally identified with their respective scientific names by two parabotanists from EMBRAPA Amazônia Oriental and noted in a field spreadsheet. The plots analyzed come from long-term studies of secondary vegetation management linked to the SHIFT-Capoeira Project, currently called Tipitamba. In the period from 2016 to 2022, floristic richness (S) decreased in the CT method from 56.6 to 36, while in the CQ it varied from 52.6 to 45.4, and in the R it went from 75.8 to 63.5. The floristic similarity between CT-CQ was 38.5% and 39.3%, CT-R was 22.7% and 20.1%, and CQ-R was 17.1% and 31.2%. Floristic diversity (H’) in CT went from 2.14 (2016) to 1.35 (2022), in CQ it went from 2.06 to 1.98, and in R it went from 2.32 to 2.2. Dry biomass (BS) in CT increased from 3.4 to 4.15 t.ha־¹, with carbon stock (EC) from 1.53 to 1.87 Mg ha־¹. In CQ, BS varied from 1.4 to 2.52 t.ha־¹, with EC from 0.63 to 1.13 Mg ha־¹. In R, BS reduced from 5.27 to 4.93 t.ha־¹, with EC from 2.37 to 2.22 Mg ha־¹. The CT area preparation method is more suitable for capoeira regeneration, promoting greater floristic diversity, equitability, height growth, and achieving values of dry biomass and carbon stock close to those observed in area R. This approach can be considered a more sustainable and effective alternative than CQ in the studied context. However, it is crucial to take into account not only ecological, but also social and economic aspects when making decisions about management practices for capoeira areas.