Protected from fire, but not from harm: seedling emergence of savanna grasses is constrained by burial depth

Light affects the germination and normal seedling development of Neotropical savanna grasses

“…For grasses, germinants may develop only the root or the shoot (abnormal seedlings; Supplementary Table S2), which impedes nutrient absorption or photosynthesis, reducing the potential of seedling emergence from the soil seed bank. The high production of abnormal seedlings may also reinforce the recruitment bottleneck caused by low seed quality (Supplementary Table S3), low seedling emergence and seedling mortality at the onset of the rainy season (Frasier et al, 1987; Silva et al, 1990; Carmona et al, 1998; Fontenele et al, 2020). Our study shows that light availability had strong effects constraining the production of normal seedlings for native species (Fig.…”

“…In summary, as the potential of seedling recruitment of invasive species is minimally reduced by light (Fig. 1) and burial depth (Dantas-Junior et al, 2018; Musso et al, 2019), their presence in the soil seed bank could outcompete native species whose seeds show high production of abnormal seedlings and low seedling emergence if buried (Fontenele et al, 2020). Native species, however, may depend on seeds on the soil surface of open vegetation gaps to successfully recruit new individuals since their seeds are light-dependent.…”

“…In the Cerrado, approximately 90% of the seeds in the seed bank are located in the first 10 mm of soil, and few are on the surface (Andrade and Miranda, 2014). Grass seeds are normally small and light-weight (Carmona et al, 1999; Aires et al, 2014; Fontenele et al, 2020) and may have structures such as hygroscopic awns (Johnson and Baruch, 2014). These are attributes that increase the chances of seed burial (Long et al, 2015).…”

“…These are attributes that increase the chances of seed burial (Long et al, 2015). Seeds in the soil seed bank may emerge if they are not deeply buried (Fontenele et al, 2020), while seeds on the surface may be shaded by nearby adult plants. However, open vegetation gaps may provide the necessary conditions for seedling establishment, as competition is reduced and light is abundant.…”

“…The germination of Cerrado grasses is usually hindered by dormancy, low-quality seeds or poor seed viability (Carmona et al, 1998(Carmona et al, , 1999Kolb et al, 2016;Fontenele et al, 2020). Light and temperature regulate seed dormancy and germination (Adkins et al, 2002;Finch-Savage and Leubner-Metzger, 2006;Long et al, 2015), but the literature about the effects of light availability on the germination of Neotropical savanna grasses is scarce (Carmona et al, 1997(Carmona et al, , 1998Kolb et al, 2016;Ramos et al, 2019).…”