Fire facilitates ground layer plant diversity in a Miombo ecosystem

Abstract

Background and aims: Little is known about the response of ground layer plant communities to fire in Miombo ecosystems, which is a global blind spot of ecological understanding. We aim to (i) assess the impact of three experimentally imposed fire treatments on ground layer species composition, and compare it with patterns observed for trees; and (ii) analyse the effect of fire treatments on species richness to assess how responses differ among plant functional groups.

Methods: At a 60-year-long fire experiment in Zambia, we quantified the richness and diversity of ground layer plants in terms of taxa and functional groups across three experimental fire treatments of late dry-season fire, early dry-season fire, and fire exclusion. Data were collected in five repeat surveys from the onset of the wet season to the early dry season.

Key results: Of the 140 ground layer species recorded across the three treatments, fire-maintained treatments contributed most of the richness and diversity, with the least number of unique species found at the No-fire treatment. The Early-fire treatment was more similar in composition to the No-fire treatment than to the Late-fire treatment. C4 grass and geoxyle richness were highest in the Late-fire treatment, and there were no shared sedge species between the Late-fire and other treatments. At a plot level, the average richness in the Late-fire treatment was twice that of the fire exclusion treatment.

Conclusions: Heterogeneity in fire seasonality and intensity supports diversity of a unique flora by providing a diversity of local environments. African ecosystems face rapid expansion of land and fire management schemes for carbon offsetting and sequestration. We demonstrate that analyses of the impacts of such schemes predicated on the tree flora alone will highly likely underestimate impacts on biodiversity. A research priority must be a new understanding of the Miombo ground layer flora integrated into policy and land management.

Keywords: C4 grass; Miombo; biodiversity; encroachment; fire management; fire regime; geoxyle; ground layer; herbaceous; plant functional group; savanna; species richness.