Diversity of germination strategies and seed dormancy in herbaceous species of campo rupestre grasslands

Abstract

The effects of fire on the vegetation vary across continents. However, in Neotropical fire-prone grasslands, the relationship between fire and seed germination is still poorly understood, while their regeneration, especially after strong anthropogenic disturbance, is challenging for their conservation. In the present study, we assessed diversity of germination strategies in 15 dominant herbaceous species from Neotropical altitudinal grasslands (locally known as campos rupestres). We exposed seeds to several fire-related treatments. We also compared germination between regularly and post-fire fruiting species. Finally, we investigated the diversity of dormancy classes aiming at better understanding the biogeography and phylogeny of seed dormancy. Germination strategies varied among families. Velloziaceae and Xyridaceae produced non-dormant, fast-germinating seeds. Cyperaceae and Poaceae showed an extremely low or null germination due to a high proportion of unviable or embryo-less seeds.The seeds of campo rupestre grasslands are fire resistant, but there is no evidence that fire triggers germination in this fire-prone ecosystem. Although heat and charred wood did not promote germination, smoke enhanced germination in one grass species and decreased the mean germination time and improved synchrony in Xyridaceae and Velloziaceae. Fire had a positive effect on post-fire regeneration by stimulating fruit set in some Cyperaceae and Poaceae species. These species produced faster germinating seeds with higher germination percentage and synchrony compared to regularly fruiting Cyperaceae and Poaceae species. This strategy of dispersion and regeneration seems to be an alternative to the production of seeds with germination triggered by fire. Physiological dormancy is reported for the first time in several clades of Neotropical plants. Our data help advance the knowledge on the role of fire in the regeneration of Neotropical grasslands.

To resist or to germinate? The effect of fire on legume seeds in Brazilian subtropical grasslands

“…However, our study showed that after the exposure to high temperatures, seeds still germinated. Those results are very consistently with what has been reported to some grass species from the Brazilian subtropical grasslands (Overbeck et al 2006) and herbaceous species in the Cerrado ecosystem (Fichino et al 2012;2016;Le Stradic et al 2015). When species from Cerrado were compared to forest species, the exposure to high temperatures did not affect negatively the Cerrado species, while forest species showed lower germination percentages (Ribeiro et al 2013;Ribeiro & Borghetti 2014).…”

Disturbance as a factor in breaking dormancy and enhancing invasiveness of African grasses in a Neotropical Savanna

“…A similar result was found by Martins & Silva (2001), where temperatures of 40ºC and 55ºC were not effective on stimulating the germination of U. brizantha. Recent studies showed that fire did not enhance the germination of grasses and forbs of open physiognomies of Cerrado but seeds were resistant to high temperatures (Le Stradic et al 2015;Fichino et al 2016). Also, heat-shock of 100 °C did not affect germination percentages of invasive species in the Chilean matorral (Gómez-González et al 2011).…”

“…On the other hand, some studies have shown decreased germination (Auld & O'Connel 1991;Ribeiro et al 2013), or no relevant effect (e.g. Le Stradic et al 2015;Fichino et al 2016).…”

Alcaligenes faecalisassociated with Mimosa calodendron rizhosphere assist plant survival in arsenic rich soils

“…This is reiterated by some promising empirical attempts that, notwithstanding, still have low success (Stradic et al, 2015). According to the importance of microorganisms in the association between soil and plants, it is possible that this low success results from changes in the composition of the soil microbiota or its association with plant roots, which reduce the adaptive potential.…”