Submitted to: Restoration Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2023
Publication Date: 3/20/2023
Citation: Muscha, J.M., Vermeire, L.T., Angerer, J.P. 2023. Fire reduces Russian olive seed germination and seedling survival with increasing fuel load. Restoration Ecology. 11. Article e13904. https://doi.org/10.1111/rec.13904.
DOI: https://doi.org/10.1111/rec.13904

Interpretive Summary: Russian olive (Elaeagnus angustifolia) is an aggressive invasive tree species that establishes within riparian areas in the western United States. It is very hard to control once established and control methods can be expensive. Studies have been conducted to examine scarification and cold treatment effects on germination and establishment of Russian olive seeds. However, to date, fire effects on seeds and newly emerged seedlings have not been documented. We sought to address this information gap by subjecting Russian olive seeds and seedlings to three different fuel loads (1,500, 3,000, and 4,500 kg/ha-1) and a non-burned control. Our results indicated that with no fire, 40% of Russian olive seeds germinated. However, fire at any of the three fuel loads reduced germination. For new seedlings (< 10 weeks old), fire killed all but one of the 250 seedlings tested, indicating the susceptibility of young seedlings to fire-induced mortality. Results from our study indicate that fire does not enhance Russian olive seed germination but reduces seed viability. In addition, fire could potentially be used as a management practice to reduce numbers of Russian olive seedlings less than one year old.

Technical Abstract: Elaeagnus angustifolia (Russian olive) is an invasive tree common within riparian areas in the western United States. Control methods can be expensive and regular monitoring is necessary to control stump and root sprouts, and newly established seedlings. Studies have assessed scarification and cold treatment effects on germination and establishment of Russian olive seeds. However, fire effects on seeds and newly emerged seedlings have not been documented. Russian olive seeds were subjected to fire at three fuel loads (1,500, 3,000, and 4,500 kg/ha-1) and a non-burned control. With no fire, 40% of seeds germinated and fire at any of the three fuel loads reduced germination. Germination was reduced to one-fifth of the non-burned level with fire at the 1,500 kg/ha-1 fuel load and did not differ from 0% at the 4,500 kg/ha-1 fuel load. The probability of at least one seed germinating from the 50-seed lots decreased as all measures of temperature and time-temperature increased. Fire killed all but one of the 250 seedlings tested, indicating Russian olive seedlings at 10 weeks old or younger were very susceptible to fire-induced mortality. However, some seedlings did not die immediately following fire and produced new axillary buds. Although all but one seedling died, bud production after fire was interpreted as an indicator of potential resistance to fire. Our results indicate that fire does not enhance Russian olive seed germination and is deleterious to seed viability. Fire could potentially kill most Russian olive seedlings that are less than one year old.