Citation: Koffi, K.F.; N’Dri, A.B.; Srikanthasamy, T.; Lata, J.-C.; Konaté, S.; Konan, M.; Barot, S. The Demographic Response of Grass Species to Fire Treatments in a Guinean Savanna. Fire 2022, 5, 193. https://doi.org/10.3390/fire5060193 Academic Editors: Eva K. Strand, Darcy H. Hammond and Grant J. Williamson Received: 15 September 2022 Accepted: 8 November 2022 Published: 16 November 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). fire Article The Demographic Response of Grass Species to Fire Treatments in a Guinean Savanna Kouamé Fulgence Koffi 1,2, *, Aya Brigitte N’Dri 1 , Tharaniya Srikanthasamy 2 , Jean-Christophe Lata 2,3 , Souleymane Konaté 1 , Marcel Konan 1 and Sébastien Barot 2 1 Research Training Unit in Natural Sciences, Environment and Sustainable Development Research Pole, Laboratory of Ecology and Sustainable Development, Ecology Station of Lamto/CRE, Nangui Abrogoua University, 02 BP 801 Abidjan 02, Côte d’Ivoire 2 Institute of Ecology and Environmental Sciences-Paris, Sorbonne Université, CNRS, IRD, INRAE, Université de Paris, UPEC, 4 place Jussieu, 75005 Paris, France 3 Department of Geoecology and Geochemistry, Institute of Natural Resources, Tomsk Polytechnic University, 30 Lenin Street, Tomsk 634050, Russia * Correspondence: koffi.fulgence@univ-na.ci Abstract: Fighting tree encroachment using fire promotes C4 perennial grasses but likely affects their demography according to the fire date during the dry season. We analyzed the impact of four fire treatments (early, middle, late and no fire) on the demography of the four dominant perennial grasses (Andropogon canaliculatus, Andropogon schirensis, Hyparrhenia diplandra and Loudetia simplex) in a Guinean savanna of West Africa (Lamto, Côte d’Ivoire). We carried out a yearly demographic monitoring of each grass individual during five years (2015–2019) on three plots by treatment and parametrized a size-classified matrix model with five circumference classes. The results showed that A. schirensis, H. diplandra and L. simplex declined (λ < 1.0) under late fire and will disappear after 10 years, as did L. simplex under the middle fire. Stasis influenced the most λ values and stable class distribution was nearly achieved in all species under all treatments. The size of L. simplex should increase under early and late fires. Our results suggest that late fire is the most detrimental fire regime for grasses in this Guinean area, contrary to early and middle fires, which could be recommended to savanna managers. Keywords: fire treatment; Guinean savanna; perennial grass; demography; population growth rate; size-classified matrix model 1. Introduction Savannas are defined by the coexistence of trees and grasses maintained by distur- bances such as fires, when the annual rainfall is above 650 mm [1]. In fact, fire permits the fighting of tree encroachment which threaten savannas and their biodiversity, by preventing an increase in tree cover and colonization by forest plants. To assess the effectiveness of fire in fighting tree encroachment, many studies have addressed its impact on tree demog- raphy [2–4], while studies on grass demography are rare (but see Garnier and Dajoz [5]). However, in humid savannas, perennial grasses dominate the grass stratum because they represent 70–98% of the total above-ground biomass [6], which make them the main source of fuel for fire [7,8]. The biomass of grass and its dryness change throughout the dry season; fire characteristics also change depending on its timing. Therefore, there are currently debates on the impact of this timing on savanna functioning and the best fire period to manage vegetation and biodiversity [9–11]. It is well known that savanna trees and grasses are adapted to fire [12,13] with fairly well-known underlying mechanisms. For example, trees have developed several mecha- nisms allowing them to persist as avoiders (species that grow quickly in the absence of fire), resisters (species that develop thick bark) or resprouters (species that regenerate from their Fire 2022, 5, 193. https://doi.org/10.3390/fire5060193 https://www.mdpi.com/journal/fire