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

Óscar Cruz,Otilia Reyes,Juan García-Duro,Sheila F Riveiro,Candela García-García,Mercedes Casal

doi:10.3390/f11020124

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.

Highlights

Fire regimes are expected to change in many areas of the world due to changes in climate and land use, causing larger, more frequent, and more severe fires [1,2,3]
The vertical structure of both communities reflects important differences between them; the community of C. scoparius is a high shrubland community, in which the development of the layer over 4 m high is scarce and, in contrast, the community of S. atrocinerea is a forest community that tends to increase the cover of the upper stratum over time (Table 1)
We found that the combination of smoke, charcoal, ash, and heat (SCAH), on the one hand, and smoke and heat (SH), on the other, produced a very sharp increase in germination reaching levels of 60% for seeds from Young Plants (YP) and 80% in seeds from OP (Figure 4a)

Summary

Introduction

Fire regimes are expected to change in many areas of the world due to changes in climate and land use, causing larger, more frequent, and more severe fires [1,2,3]. The severity of fire can have a strong impact on early succession after fire, which will determine the structure and functioning of forest ecosystems [8]. Understanding the relation between fire severity and the natural regeneration of communities is essential for mitigating the adverse effects of fires and for maintaining beneficial ecosystem functions and services [9]. The relevance of post-fire restoration is likely to increase as fire regimes worldwide are expected to be altered, with an increase in fire recurrence, extent, and/or severity of wildfires due to the ongoing climate change [10,11]

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Conclusion