Because prescribed mid-dry season burn (MDS) failed in preventing shrub encroachment in wet savannahs of central Côte d’Ivoire, other times of burning are under investigation to identify a successful one. However, the management mainly focuses on vegetation, neglecting soil biodiversity including earthworms despite their critical role in soil functioning. This study explores how earthworms are impacted when shifting savannah burning from MDS to early-dry season (EDS) or late-dry season (LDS). It was carried out at three sites comprised of three plots each, where the fire treatments were respectively and annually applied for eight years. Earthworms were sampled using the Tropical Soil Biology and Fertility (TSBF) 25 cm × 25 cm x 30 cm-soil monolith protocol. Relative to MDS (352 ind. m −2 ), total earthworm density was lower under the alternative burns particularly LDS (229 ind.m −2 ). EDS fire strongly suppressed epigeic earthworms' population while LDS fire reduced endogeic earthworms by 60 % relative to MDS. Consequently, earthworm community composition was markedly altered by EDS, and weakly by LDS (40 % and 18 % of Colwell complementarity, respectively). Importantly, earthworm species richness and Shannon-Weaver index were lower under both alternative burns. Thus, EDS fire was the most detrimental to epigeic earthworms whilst LDS fire, to the entire earthworm community. Although earthworms were influenced by soil attributes, it is likely that their phenology during the dry season critically determined their responses to fires. After eight years of implementation, neither of the alternative burning regimes can be considered a viable substitute for MDS with regard to earthworm diversity conservation. These findings are of vital importance for the development of management strategies aimed at the integrated conservation of biodiversity in wet savannahs, highlighting the need to reconcile MDS burning with other shrub-control techniques that are less destructive to soil fauna. • Fire severity was critically determined by the phenological stage of earthworms (EW). • EW density and diversity decreased under alternative EDS and LDS fires vs. prescribed MDS fire. • EDS fire more strongly suppressed epigeic EW and markedly altered community composition. • LDS fire was the most severe for the entire community, specifically for endogeic EW. • Neither of the alternative fires is a viable substitute for MDS fire with regard to EW diversity conservation.
Yapo et al. (Thu,) studied this question.