Factors influencing seed germination in Cerrado grasses

Abstract

Few studies address the ecology of herbs of Cerrado grasslands, which are ecosystems where the long dry season, high temperatures, insolation, fire and invasive grasses greatly influencing germination and the establishment of plants. We assessed germination of 13 species of Poaceae from Cerrado grasslands under nursery conditions or in germination chambers, the latter with i) recently collected seeds and seeds after six months storage, ii) under constant and alternating temperatures, and iii) in the presence and absence of light. Germinability, mean germination time (MGT) and required light were quantified to elucidate factors involved in successful germination. Germinability was low for most grasses, probably because of low seed viability. For most species, germinability and MGT were not altered by seed storage. Germination percentages were higher at alternating temperatures and in the presence of light, factors that are more similar to natural environmental situations compared with constant temperature or the absence of light. Our findings indicate that alternating temperatures and light incidence are key factors for germination of species of Poaceae. The maintenance of these environmental factors, which are crucial for the conservation of Cerrado grasslands, depends on appropriate management interventions, such as fire management and the control of biological invasion. Keywords ABSTRACTFew studies address the ecology of herbs of Cerrado grasslands, which are ecosystems where the long dry season, high temperatures,

Native remnants can be sources of plants and topsoil to restore dry and wet cerrado grasslands

“…In contrast to other studies in the Cerrado ecoregion that found positive outcomes using direct seeding of trees, forbs, and grasses (Silva et al ; Pellizzaro et al ), in our study, direct seeding of native grasses did not show itself to be an efficient way to restore either the dry or the wet cerrado grasslands. In climate chamber conditions, we recorded low germination rates, as has been observed for other nonwoody cerrado species (Le Stradic et al ; Kolb et al ; Pellizzaro et al ). Seed dormancy occurs in an expressive number of savanna species as a strategy to prevent germination under unfavorable environmental conditions for establishment (Ramos et al ; Escobar et al ), and low seed viability is reported by several savanna grass species (Carmona et al ; Le Stradic et al ; Kolb et al ).…”

“…In climate chamber conditions, we recorded low germination rates, as has been observed for other nonwoody cerrado species (Le Stradic et al ; Kolb et al ; Pellizzaro et al ). Seed dormancy occurs in an expressive number of savanna species as a strategy to prevent germination under unfavorable environmental conditions for establishment (Ramos et al ; Escobar et al ), and low seed viability is reported by several savanna grass species (Carmona et al ; Le Stradic et al ; Kolb et al ). In addition, some studies have pointed out the importance of microorganisms in the germination and establishment of savanna native grasses (Veenendaal et al ; Martins et al ), and these associations are still poorly understood in the cerrado vegetation.…”

“…There is no water deficiency in the cerrado wet grassland, making it possible for seed germination throughout the year, even in the dry season (Ramos et al ). Seeds from wet grasslands have higher germination rates and less dormancy (Kolb et al ; Ramos et al ), indicating that filters in the wet grasslands may be related more to establishment (i.e. competition) than to germination per se.…”

Changes in irradiance and soil properties explain why typical non-arboreal savanna species disappear under tree encroachment

“…The higher soil moisture and the lower radiant energy can reduce soil temperature in the forested savanna. Furthermore, soil temperature would become more stable, hindering the germination of species that need fluctuations in temperature to break the dormancy of their seeds (Kolb et al 2016). These aspects can lead to a reduction in germination success of cerrado understorey plants and, thus, compromise the persistence of these species in the encroached community.…”

Resilience and restoration of tropical and subtropical grasslands, savannas, and grassy woodlands

“…For restoration of tropical grasslands, knowledge is slowly increasing about the transfer (Le Stradic, Buisson & Fernandes, 2014a;Le Stradic et al, 2016;Pilon et al, 2018) and propagation of old-growth grassland species Oliveira et al, 2012;Le Stradic et al, 2014b;Gomes et al, 2018), yet for most ecosystems such information remains scarce or non-existent, particularly for herbaceous species (Fernandes, 2016). Complicating matters, emerging research on species of the Cerrado, Katanga copper outcrops (Central Africa), and Queensland (Australia), suggests that many graminoids -a functional group that is critical to ecosystem flammability and livestock forage -produce few seeds, much of which is of low quality (Silcock & Scattini, 2007;Boisson et al, 2015;Le Stradic et al, 2015;Kolb et al, 2016;Dayrell et al, 2017). As such, the opportunities for reintroduction and propagation via seed sowing, soil transfer, and hay transfer, are often extremely limited (Le Stradic et al, 2014a; but see Le Stradic et al, 2014b;Sampaio et al, 2015;Gomes et al, 2018;Pilon et al, 2018).…”