Fire season differentially affects resprouters in a Cistus-Erica shrubland of central Spain

Abstract Background Many plants survive fire by resprouting from lignotubers partially or completely buried in the ground. Resprouting success after fire could vary with fire season due to changes in plant carbohydrate reserves, soil moisture, and plant water status, among other factors. It may also depend on plant size, as this affects lignotuber depth in the soil. We investigated the effects of fire season on resprouting success (%) and speed (time to reach 50% of resprouting, t 50 ) in two lignotuberous species ( Erica arborea and Phillyrea angustifolia ) in a shrubland of central Spain. Over three consecutive years, three 13 × 14 m plots were burned early (ES) and late (LS) in the fire season (end of June and early October, respectively). Before fire, individuals were permanently marked after being classified as small, medium, or large. Predawn plant water potential (Ψ pd ) was measured during the fire season. Resprouting was monitored for up to two years. We used repeated measures ANOVA to test the effects of fire season and year (within-subjects effects), and plant size (between-subjects effects) on resprouting success (%) and t 50 . Results Resprouting success in E . arborea increased from ES to LS fires, and with plant size, while P . angustifolia was unaffected by fire season or plant size. The fire year did not directly affect resprouting success but interacted with fire season (for both species) and plant size ( E . arborea ). t 50 was unaffected by fire season in E . arborea , but it significantly affected P . angustifolia , which showed smaller values after ES burns. t 50 varied by fire year in both species, especially when plant water potentials were low. Plant size also affected t 50 in P . angustifolia . Ψ pd and t 50 for both species combined were negatively related, with a more pronounced effect in LS fires. Conclusions Our results show that the demography of the two resprouters will be differentially affected by fire season, alone or in interaction with the fire year and plant size. E . arborea was highly sensitive to fire season, particularly the smaller individuals, and to ES burns. In contrast, P . angustifolia was highly insensitive. t 50 response among species differed by fire season, fire year, or size. Ψ pd determined t 50 of both species combined. These responses could impact long-term population structure and community dynamics of this Mediterranean shrubland.