Effects of prescribed burning on soil microorganisms

• Autor(a) principal: Luís, Rosa de Jesus Marques
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/33679
• topic: High mountain; Asín de Broto; Low-intensity; Fire; Shrubland; Superficial soil; Colony-forming unit

Fire is an integral part of nature, but it has come to assume the role of threat, in particular, due to the frequency and scale that wildfires have acquired in recent years. Prescribed burning can be a fire prevention tool because it removes vegetable fuel in excess. However, it is necessary to know the effects of its application to understand how it affects natural ecosystems, including the soil. The main objective of this work is to evaluate the effects of prescribed burnings on high mountain soil microorganisms, simultaneously evaluating changes in the chemical and physical properties of the soil. The study area is located in Asín de Broto, in the Central Pyrenees, Spain. To develop this study, samples were collected from three different depths (0-1, 1-2, and 2-3 cm) and at 16 different points: 4 points never burned (UB), 4 points immediately after a prescribed burning (B0), 4 points where a prescribed burning was performed 5 years ago (B5) and 4 points where a prescribed burning was performed 9 years ago (B9). For the determination of densities and porosity, a single sample was collected at each of the 16 points, with a depth between 0 and 6 cm. No significant changes in soil moisture were observed at any depth over the years. In the B0 samples, significant increases were observed in porosity, pH, and electrical conductivity, between 0 and 1 cm, and structural stability, pH, organic matter content, and electrical conductivity at depths between 1 and 3 cm. In samples B5, the structural stability decreased between 0 and 2 cm, but remained similar to the values before fire from 2 to 3 cm; pH remained higher at all depths; the organic matter content decreased between 0 and 1 cm, but remained higher between 1 and 3 cm; electrical conductivity returned to pre-burning values at all depths. In samples B9, structural stability returned to pre-fire values between 0 and 2 cm, but decreased between 2 and 3 cm; pH remained high at all depths; the organic matter content returned to pre-fire values between 0 and 1 cm, but maintained high values at other depths; electrical conductivity remained similar to pre-fire values at all depths. In the biological properties, in samples B0, a decrease in CFU of bacteria between 0 and 1 cm was observed, but without significant changes between 1 and 2 cm; there was an increase in fungal CFU between 0 and 2 cm. In samples B5, there was an increase in bacterial CFU between 0 and 1 cm, but a decrease between 1 and 2 cm; in fungi, there was a decrease between 0 and 1 cm, but the number of CFU remained similar between 1 and 2 cm. It was concluded that prescribed burning does not significantly affect most physical and chemical properties of the soil and may even have positive effects on some properties, even after nine years. However, the microorganism communities are severely affected and do not recover at the end of this period.