Using prescribed fire in a post harvesting Eucalyptus globulus plantation: first effects

• Autor(a) principal: Lima, Mariana Isabel Almeida
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/36864
• topic: Low severity fire; Eucalypt; Forest management; Soil impacts; Stump resprouting

Prescribed fire may be a good technique for the management of harvest residues in Eucalyptus globulus plantations, however the knowledge of the impacts of this technique on the soil and the forest plantations is a little scarce, due to the high variety of results obtained by previous studies. The main objective of this work was to determine the effects of the prescribed fire to manage harvest residues on the soil physical and chemical properties. A study area was established, a 10 years old first rotation plantation harvested during September of 2021, in Quintarrei, Valongo, Oporto, Portugal. After initial soil physical and chemical characterization and biomass accumulation assessment, the prescribed fire treatment was performed on December 16th of 2021. Soil burn severity was evaluated by visual assessment soil and forest floor changes and by monitoring the topsoil temperatures with thermocouples. As shown by the results, prescribed fire was efficient decreasing the biomass loads and fire risk, while having a low fire severity of 1. Soil physical (mean weight diameter, stoniness, granulometry and bulk density) and chemical parameters (pH, electric conductivity, organic matter, exchangeable cations (Ca²⁺, Mg²⁺, K⁺ and Na⁺), exchangeable acidity, cation exchange capacity (ECC), cation saturation (EBSl), extractable phosphorus, and micronutrients (Zn, Cu, Mn, Fe)) were monitored in February, a month and a half later. Stump resprouting was assessed 4.5 months after prescribed fire installation and stem size was measured at that same time and again in September 2022, 10 months after prescribed fire installation. While all of the physical parameters remained unaltered, pH, cations exchange capacity, cation saturation, extractable phosphorus, Mg²⁺, Ca²⁺, K⁺ and Mn increased in the prescribed fire treatments, and exchangeable acidity, Al and Fe decreased. The increased nutrients in the soil and the unchanged physical parameters indicate that prescribed fire can be a good technique for the management of harvest residues in eucalyptus globulus plantations. This hypothesis is also supported by stump resprouting and stem growth, which was very similar in the control and prescribed fire treatment of both blocks however, further monitorization is necessary to understand its viability.