FIRE FREQUENCY CHANGES CHEMICAL AND BIOLOGICAL SOIL PROPERTIES?

Resumo

Fire is a high-impact disturbance in the ecosystem, and its severity depends on the frequency. We hypothesized that burning could affect soils' chemical and microbiological parameters subject to different fire regimes. We studied three areas covered by concretionary petroferric Plinthosols in Cerrado. The assessed areas received the following treatments: burned annually from 2014 to 2017, burned in 2014 and 2016, and no fires during the same period. Three deformed soil samples were collected at each site to determine their chemical properties, soil microbial respiration, soil microbial biomass, metabolic quotient, and total organic carbon content. We also tested the significance of the PCA axis by permutation tests. The scores of the significant axis were used to test the null hypothesis of equality of the treatment by mensa of permutation tests. The permutation tests applied to PCA scores suggest that the frequently burned  holds the minor soil fertility, while but not-burned and the biannual burned site save the same fertility levels. Concerning microbiota biomass and soil carbon, our results suggest a gradient in which the lowest content were found in frequently burned sites and the highest content in the biannualy burned ones. We concluded that fire impacts were dependent on their frequency.