In situ seed storage affects germination responses to fire-related cues in Cerrado species

Fire-related cues can influence germination and seedling establishment in fire-prone ecosystems by breaking physical dormancy (PY) or stimulating germination in species with water-permeable seeds. However, most studies rely on fresh seeds and overlook how soil seed bank storage may change germination responses to fire cues. We investigated whether in situ seed storage affects germination responses to heat shock and smoke in Cerrado species.

Seeds of 13 Cerrado species, dispersed at the beginning of either the dry or rainy season, were collected and exposed to heat shock (100°C and 200°C for 1 min) and smoke water treatments. Remaining seeds were buried in the field and exhumed after 1, 3, 6, 9, and 12 months. After each retrieval, seeds were exposed to the same fire-related cues and germinated under controlled conditions for 30 days.

In situ seed storage changed germination responses to fire-related cues in more than 60% of the studied species, but responses were highly species-specific. Smoke effects changed over time in two non-dormant species, with germination either increasing or ceasing after burial. Storage increased sensitivity to heat shock in seeds with PY, leading to higher germination after exposure to 200°C compared to fresh seeds. Species dispersing during the rainy season generally showed rapid loss of viability and weak responses to fire-related cues, whereas several species dispersing during the dry season maintained viability and exhibited stronger storage-related changes in germination.

Our results demonstrate that germination responses to fire-related cues in Cerrado species depend not only on the fire cue itself, but also on seed storage time and dispersal season. These storage-mediated and species-specific responses suggest that recruitment dynamics in tropical savannas are more complex than inferred from experiments using only fresh seeds.