Abstract Detail



Ecology

Soares, Vanessa [1], Scremin-Dias , Edna [2], Daibes, Luís Felipe [3], Damasceno-Junior, Geraldo [2], Pott, Arnildo [2], De Lima , Liana [2].

Role of Fire on Regeneration from Seed of Two Pioneer Species of a Tropical Wetland.

Contrasting responses of seed germination to fire have been reported in different vegetation throughout the globe. In Brazil, the Pantanal harbors one of the largest floodplains in the world, marked by a seasonal climate, faced periods of flooding, followed by a dry season frequently subjected to fires. We aimed to understand the role of fire on regeneration from seed in the Pantanal, using two pioneer species from the riparian forest as study models: Sesbania virgata and Guazuma ulmifolia. Both species displayed physically dormant seeds. To test the effect of fire on germination, seeds were subjected to (1) laboratory heat shocks and (2) field-simulated experimental burns, besides the controls  In Experiment 1 we subjected seeds to the temperatures of 65, 85, 105, 125, and 145°C (all treatments ±5°C), during exposure times of five minutes under laboratory conditions. In Experiment 2, simulating field conditions, seeds and corky fruits were placed upon the soil surface, and seeds buried two centimeters belowground and then subjected to experimental burns. We recorded seed water content after heat shocks, and the proportions of germinated, hard, and dead seeds in both experiments. Additionally, seed viability (tetrazolium test) was recorded following the experimental burns. For both species, up to 50% of seeds remained hard, ungerminated, and with no signs of imbibition, under the exposure up to 85±5°C indicating a relative tolerance to this temperature but showing no dormancy break. Otherwise, germination percentage and seed water content decreased for both species with the enhancement of heat shocks, while the proportion of dead seeds increased with temperatures. In the experimental burns, direct exposure to fire killed nearly all seeds placed upon the soil surface. However,  seeds buried belowground kept hard up to 80 and 40% for S virgata and G.ulmifolia, respectively. For S. virgata, buried seeds showed slightly increased germination (18%) compared to the untreated control (~6%) and seeds inside the corky fruits remained viable up to 37%. While G. ulmifolia seeds decreased germination following the treatments and seeds inside the corky fruits reduced the proportion of hard and viable seeds after fire. Thus, the fire has shown little to no effect on dormancy break but may rather deplete viability according to seed position in the soil or inside the corky fruits, except those protected in the soil seed banks. Our study provides crucial information to understand seed tolerance to increased fire frequency and to introduce native seeds on restoration initiatives in disturbed tropical wetlands.


1 - Federal University of Mato Grosso do Sul, Department of Botany, Institute of Biosciences, Campo Grande, Mato Grosso do Sul, 79070-900, Brazil
2 - Federal University of Mato Grosso do Sul, Department of Botany, Institute of Biosciences, Cidade Universitária s/n, Campo Grande, Mato Grosso do Sul, 79070-900, Brazil
3 - Sao Paulo State University, Department of Botany, Institute of Biosciences, Av. 24-A 1515, Rio Claro, São Paulo, 13506-900, Brazil

Keywords:
Brazilian wetland
Fire ecology
seed viability
seed hardness
Guazuma
Plant ecology
Pantanal
Sesbania
seed germination
seed physiology
heat shock.

Presentation Type: Poster Time and date to be determined
Number: PEC014
Abstract ID:574
Candidate for Awards:Ecological Section Best Graduate Student Poster


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