Effects of heat on the germination of sclerophyllous forest species in the highlands of Madagascar

Abstract

International audienceThe effects of fire on germination have been extensively studied in many ecosystems. Several studies have shown that plant species in ecosystems frequently exposed to fire can survive through two main mechanisms: vegetative regeneration (re-sprouts) and recruitment of new individuals from a fire-resistant seed bank. In Africa, an increase in temperature can break seed dormancy and stimulate germination of some herbaceous and woody species. In Madagascar, the once widespread highland ecosystems dominated by woody species are now highly fragmented and dominated by anthropic grasslands and fields, with a significantly reduced area occupied by sclerophyllous forests referred to as ‘tapia woodlands’. Six species of this endemic vegetation type were studied: Abrahamia ibityensis (Anacardiaceae), Aphloia theiformis (Aphloiaceae), Carissa edulis (Apocynaceae), Pentachlaena latifolia (Sarcolaenaceae), Uapaca bojeri (Phyllanthaceae) and Vaccinium secundiflorum (Ericaceae). Germination tests were conducted (i) by soaking seeds in water for 24 h (imbibition) or (ii) by exposing the seeds to dry heat. Four different temperatures (40, 60, 80 and 120°C) were applied, and seeds were exposed for 10, 30, 60 and 90 min. To simulate hotter faster-burning fires, two higher temperatures (100 and 120°C) were also used by exposing seeds to dry heat for 5 min. The results did not reveal any significant effect of 24-h water imbibition on germination. For most species, germination decreased with increasing temperature of treatment using dry heat. Uapaca bojeri did not germinate under any treatment. Further studies on the biological and ecological characteristics of tapia woodland species in response to fire are needed to help guide conservation, management and restoration activities focusing on this endemic vegetation type

Drivers of fire occurrence in a mountainous Brazilian cerrado savanna: Tracking long-term fire regimes using remote sensing

“…The timing of fire occurrence is also relevant to determine the damages to leafing, flowering, fruiting and/or germination processes, impacting seedlings and reducing recruitment, as well as favoring specific groups of species that are fire tolerant or fire resistant (Alvarado et al, 2015(Alvarado et al, , 2014Hoffmann, 1998). The peak in active fires, observed on MODIS data from Serra do Cipó between the end of the dry season and the beginning of the wet season (September and October), is consistent with other cerrado studies.…”

Biodiversity hotspots and Ocbil theory

“…microrefugia and climate change (Cooper et al 2011;Keppel et al 2012;Ashcroft and Gollan 2013;Brendonck et al 2014;Mee and Moore 2014;Barrett and Yates 2015), the evolution of trees (Raven and Andrews 2010;Cramer 2012), clonality (Binks et al 2015), the occurrence of OCBISs (old, climatically buffered, infertile seascapes - Langlois et al (2012), significant gaps in Darwinian evolutionary theory (Hopper and Lambers 2009), old salt lake systems (Bui et al 2014a, b), and evolution of novel aquatic traits (Tuckett et al 2010;Davies and Stewart 2014). Seed biological studies are beginning to explore the relevance of Ocbil theory to their discipline (Tuckett et al 2010;Hidayati et al 2012;Wilman et al 2014;Alvarado et al 2015b;Edwards et al 2015;Ribeiro et al 2015).…”

The eco‐evolutionary history of Madagascar presents unique challenges to tropical forest restoration

“…Alvarado et al (2014) found that forest fragments with apparently less‐frequent fire regimes showed greater tree diversity and sapling density, though fire frequency and management regime were not directly measured in this study. When assessing individual species to investigate the mechanism of this observed hindered post‐fire regeneration, Alvarado et al (2015) found that the seeds of many native highland tree and shrub species did not germinate in response to heat treatments meant to simulate fire. They found a modest ability among some native species to survive exposure to high heat, though it was not clear how this degree of fire tolerance compared to similar biogeographic regions outside of Madagascar.…”