Managing fires in a woody encroachment context: Fine fuel load does not change across fire seasons in a Guinean savanna (West Africa)

Abstract

Fine surface fuels play a key role in driving fire spread, and therefore play an important role in wildfire management in savannas. In protected areas of the Guinean savannas (humid savannas of West Africa), despite prescribed early-dry season (EDS) or mid-dry season fire (MDS), woody encroachment is increasingly occurring. Recently, N'Dri et al. (2022) showed that late-dry season (LDS) fire applied at least three successive years alternating with a maximum of two successives EDS or MDS fires could reduce woody encroachment in protected areas of the regions. However, the relationship between time of burning (TOB) and fine fuel load (standing grass and fallen leaves of grasses and trees) remains uncertain. In a 10-year experimental field study (2013–2023), we monitored fine fuel load under annual fires set in three different TOB within the dry season: EDS, MDS and LDS. We also explored how fuel loads were influenced by fireline intensity and vice-versa, in addition to grass growth dynamic during one year after each fire. Results showed that grass grows faster in height after fires, reaching the highest peak (∼2 m) in November regardless of the TOB. Overall, the TOB within the dry season did not affect significantly the total fine fuel load even after 10 years (1.22 ± 0.12, 1 ± 0.09 and 0.96 ± 0.09 kg m−2 respectively for EDS, MDS and LDS fires). Nevertheless, in EDS plots, the greatest biomass of grass and litter was generally observed in alternate years. This is most likely due to a high decomposition rate and termite activity which played a rôle in maintaining basic levels. Overall, fireline intensity did not influence the subsequent fine fuel load recorded in November and fine fuel load recorded just before fires did not influence fireline intensity. Given the results of the current study, the best procedure in setting successive fires to reduce woody encroachment in Guinean savannas, remains that of N'Dri et al. (2022).