Fire cues and germination of invasive and native grasses in the Cerrado

Abstract

Fire-related cues may enhance seed recruitment in flammable ecosystems and differences in fire-germination responses of invasive vs. native species can drive the invasion process. We evaluated the effects of heat shock and smoke water solution treatment on seed germination of invasive (Melinis minutiflora, Urochloa decumbens, U. brizantha) and native grasses (Axonopus pressus, Aristida setifolia, Gymnopogon foliosus) of the Cerrado. The effect of fire temperature was tested by exposing seeds to heat shock treatments of 60, 100, and 200 °C for one minute, comparing them to untreated seeds. The effect of smoke was tested by soaking seeds for 24-h in an aqueous smoke comparing them to seeds soaked in distilled water. Differences among treatments were evaluated by ANOVA and randomization tests. None of the tested species had germination stimulated by the temperature or smoke. Both species of Urochloa experienced decreased viability with increasing temperature, while seeds of native species and M. minutiflora tolerated heat shock up to 200 °C. The invasive grasses usually germinated faster than the native grasses. Germination time is therefore a crucial trait driving the invasion process, irrespective of fire-related cues. Other seed traits (e.g. dormancy) and higher resprouting capacity may help invasive species to persist in frequently burned savannas.

Fire‐released seed dormancy ‐ a global synthesis

“…Open circle = no‐smoke control; filled circle = smoke pretreatment; open square = no‐heat control; filled square = fire‐type heat pretreatment. Collated from 293 tests undertaken in 12 studies (Jeffery et al ., 1988; Crosti et al ., 2006; Travlos, Economou & Karamanos, 2007; Reyes & Trabaud, 2009; Tavşanoğlu, 2011; Chou, Cox & Wester, 2012; Ribeiro, Pedrosa & Borghetti, 2013; Galindez et al ., 2016; Paredes et al ., 2018; López‐Mársico et al ., 2019; Fernandes et al ., 2020; Gorgone‐Barbosa et al ., 2020). Inset: the best‐fit curves with 95% confidence intervals (GAM, P < 0.0001; untransformed data).…”

Alterações químicas de solos da Caatinga sob cultivo da Cryptostegia madagascariensis

“…O aumento da umidade em ambos os solos sob crescimento das plantas jovens de C. madagascariensis elevou os teores de sódio, refletindo dessa forma, desequilíbrio nutricional causado pelos distúrbios na absorção, mesmo assim não prejudicou o crescimento da espécie. Esse comportamento está de acordo com Gorgone- Barbosa et al, 2020, tendo em vista que os altos teores de Cálcio podem apresentar desequilíbrios nos sítios de ligação no metabolismo das plantas.…”

“…A invasão biológica altera tanto as condições químicas dos solos invadidos, como a salinidade, a umidade, o pH e os teores de Carbono e Nitrogênio (Gorgone- Barbosa et al, 2020), como também as condições físicas do solo, como por exemplo a estabilidade dos agregados (Barbosa et al, 2019). Uma espécie invasora que se destaca como redutora da salinidade do solo é Prosopis juliflora, que além de se comportar como redutora da salinidade, também se destaca por reduzir o pH, a condutividade elétrica e os níveis de sódio trocáveis (Mojzes et al, 2020).…”

Are wildfires affecting seed germination in cactus? An experimental assessment

“…Fire is one of the main ecological factors affecting vegetation dynamics worldwide (Bond & Keeley 2005;Pausas & Keeley 2009), influencing species survival and growth, as well as the establishment of new individuals from seeds (Paula & Pausas 2008;Pausas & Keeley 2014). In fire-prone ecosystems, many species have developed seed germination strategies to tolerate or even be stimulated by fire-related factors, such as smoke, charred wood and the high temperatures associated with fire (Keeley & Fotheringham 2000;Hanley et al 2001;Luna et al 2007;Zuloaga-Aguilar et al 2011;Fichino et al 2016;Gorgone-Barbosa et al 2020). Although the germination response to heat shock of many species from different regions has been widely studied, works have largely focused on trees, shrubs, forbs and grasses (e.g.…”

“…2016; Gorgone‐Barbosa et al . 2020). Although the germination response to heat shock of many species from different regions has been widely studied, works have largely focused on trees, shrubs, forbs and grasses (e.g.…”