ANÁLISE COMPARATIVA ENTRE FLORESTA NATIVA E FLORESTA PLANTADA DE PINUS: ESTUDO EM MICROBACIAS EXPERIMENTAIS NO PARANÁ

Abstract

Each type of land use and cover influences the environment in different ways; understanding the impacts of human actions/changes on different uses is crucial for conservation. Therefore, this research aimed to analyze whether water quality is affected by the replacement of native vegetation with planted vegetation. The study was conducted in two micro-basins, one with native forest and one with planted forest, in Telêmaco Borba, Paraná, a municipality which is a benchmark for the representation of planted forests in Brazil. To understand the changes in water quality, the trophic state index (TSI) was used, considering total phosphorus. Additionally, precipitation, flow, nitrate, and total phosphorus parameters were analyzed. Data collection was conducted from 2004 to 2024 by the Cooperative Program on Monitoring and Modeling of Watersheds, which conducts research in collaboration with the company responsible for the area and the Forest Hydrology Laboratory at ESALQ/USP. Nitrate values in the planted watershed exceeded those in the native watershed in years with extreme precipitation events (2009, 2015) and in the 2023 rainy season. For phosphorus, in the years where there was a significant difference, the values in the native watershed were higher. However, in 2004 (0.075 mg/L), 2008 (0.043 mg/L), and 2022 (0.048 mg/L), the planted forest watershed presented higher averages, coinciding with years of below-average flows, a relationship explained by the negative correlation between phosphorus and flow. Regarding the TSI, both watersheds presented similar behavior, with classification ranging from ultraoligotrophic to mesotrophic. Even so, except for 2004, the average values in the native watershed were higher in most years. For both phosphorus and TSI, this difference may be related to the higher proportion of silt in the native watershed, which influences nutrient retention and availability in the aquatic system. The study also showed that, for all parameters analyzed, the years during and after forest management did not show substantial increases, indicating that changes in land use and land cover did not directly compromise water quality. Additionally, through the application of NDVI, it was possible to identify the time required for vegetation cover to return to pre-management conditions, demonstrating the resilience of planted vegetation in canopy recovery. These results contribute to a deeper understanding of the effects of different vegetation covers and mosaic management practices on environmental monitoring and water quality management in watersheds.