The Effect of Ashes on Seed Viability and an Epigeic Worm's Mortality

Overview

Objectives/Goals In 2005, Rancho Palos Verdes suffered a 200 acre wildfire. This project investigates the effect of residual ashes to the viability of seeds indigenous to the area, expressed through seed germination rates and seed embryo root elongation; and the mortality rate of the epigeic (surface dwelling) earthworm Eisenia fetida. While wildfires are destructive, ironically, ashes are occasionally a recommended fertilizer, and some chaparral plant species have adapted to particular fire regimes. Methods/Materials Each species of seed was exposed to 5 concentrations of ashes in 5 containers, 10 seeds each, with sterile silica sand, (a 6th cup, excluded ashes: control), kept in a dark germinator (20-23.9°C) until germination started, then 16-18°C dark-8hrs to 22-24°C light-16hrs, and examined upon control#s 65% (or maximum) germination. Prior exposure, each species was treated to overcome dormancy. E. fetida was exposed to the same 5 concentrations in 5 containers, 10 worms each, with sterile soil (a 6th container excluded ashes: control), kept in the dark (20-24°C) 14 days; then mortality was recorded. Both procedures were replicated 3 times. Substrates were kept 35% moist @ 6.8-7pH. Ashes were made from vegetation common to the wildfire area. Results For all 6 seed species, the mean germination rates: 7%, 23%, 38%, 58%, 64%, 85%; mean elongation (cm): .53, 1.97, 2.21, 3.13, 3.78, 4.16. E. fetida#s mortality ranged: 33%, 3%, 0%, 7%, 0%. Results were based on 5 ash levels + control in this sequence: 2.35cm, 1.17cm, .59cm, .29cm, .15cm, none. Tested ashes contained surplus phosphorous (>14ppm) & potassium (>220ppm). At the highest concentration level 3 species of seed failed to germinate. Conclusions/Discussion Thus, while research suggests some flora benefit from ashes, ashes at all 5 concentration levels inhibited the germination rates and embryo root elongation of all 6 species of herbaceous plant seeds, native to Rancho Palos Verdes' chaparral and coastal scrub. The overall mean germination rate decreased up to 92% and the overall mean root elongation decreased up to 87%, compared to the control groups. The elevated level of phosphorous & potassium found in the ashes may have caused or contributed to the reduced germination rates and root elongations. E. fetida suffered up to a 33% mortality. Thus, residual ashes, especially high concentrations, following a wildfire, should be dispersed to promote restoration.

Awards (1)

• First Place

Competition history

• CSEF 2009 Toxicology (Junior Division Only) · Entry J2305

Resources

• CSEF project summary ↗

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