Fire Severity Drives the Natural Regeneration of Cytisus scoparius L. (Link) and Salix atrocinerea Brot. Communities and the Germinative Behaviour of These Species

Abstract

Research Highlights: Data indicated that fire severity modulates natural regeneration of Cytisus scoparius and Salix atrocinerea communities and drives much stronger effects on the germination of the dominant species. Background and Objectives: Previous studies demonstrated that fire severity induces different behaviours in plant species. Mother plant age is an important feature that must also be considered in plans of forest restoration. The objectives were to determine, in field studies, the effect of fire severity on the natural regeneration of C. scoparius and S. atrocinerea communities, to know the role of mother plant age on the germination of seeds of C. scoparius and S. atrocinerea, and to quantify their germination response at different levels of fire severity, in laboratory settings. Material and Methods: We have analysed the role of fire severity on the natural regeneration of C. scoparius and S. atrocinerea communities considering cover and height. Forty 30 × 30 m plots were randomly located in C. scoparius and S. atrocinerea communities. Fire severity on the germination of dominant species was tested through different levels of smoke, charcoal, ash, and heat. Results: High severity reduced the vertical cover and growth in height of the two communities and favoured the increase of cover of woody species in the C. scoparius community and herbaceous species in the S. atrocinerea community. Mother plant age determined germination percentages of C. scoparius seeds. Germination of C. scoparius was increased by moderate heat, and heat and smoke; and fire severity greatly reduced germination of S. atrocinerea. Conclusions: The regeneration responses after fire were largely controlled by interactions between the fire severity and the individual species regeneration strategies. For restoration purposes, C. scoparius seeds should be treated with 80 °C and smoke for 10 min, in order to increase germination; however, Salix seeds should be used without treatment and immediately after dispersion.

Effect of the Forest-Mine Boundary Form on Woody Colonization and Forest Expansion in Degraded Ecosystems

“…Genista florida showed also vegetative reproduction in the study area [47], which has been considered the most successful means of colonization in reclaimed mines of Germany [48] and the USA [3]. In turn, the massive spread of Cytisus scoparius colonizing open areas has been closely linked to specific traits of invasive species such as the production of high amounts of seeds forming a long-lasting seed bank [49], a capacity to establish in areas immediately after a disturbance and fast initial growth [40,50,51].…”

Fire and seed maturity drive the viability, dormancy, and germination of two invasive species: Acacia longifolia (Andrews) Willd. and Acacia mearnsii De Wild

“…In a more severe and recurring fire scenario, both species will have advantage over native species because both Acacias germinate rapidly, with high percentages, and produce seeds at early ages (2-3 years, personal observation). Other native species adapted to fire such as Ulex europaeus L., C. scoparius, or P. tridentatum (Reyes and Casal 2008;Cruz et al 2020) are shrubs and therefore could not compete with invading trees that grow very fast in height. Among the native vegetation of Galicia, two fast-growing tree species could compete with the two studied species without fire, Salix atrocinera Brot.…”

“…and Betula pendula Roth. ; however, their germination is not stimulated by fire (Reyes and Trabaud 1997;Cruz et al 2020), and its competitiveness would be compromised after fire.…”

Effect of fire factors (smoke, ash, charcoal and heat) on seeds of plant species

“…Combined treatments of several fire factors can also be done, for example [7] : SCAH: Smoke 10 min + Charcoal of studied specie + Ash 1 + 80 °C, 10 min. SH: Smoke 10 min + 80 °C, 10 min.…”