European gorse
Ulex europeaus
Family: Fabaceae
Fire effect on plant
European gorse typically survives fire, even the above ground stems, with the exception of severe ground fires that consume the deep organic horizon (Zouhar 2005).
Key traits
European gorse is capable of resprouting from low portion of stems and roots (adventitious buds and root crown) following burning (Zouhar 2005). Aboveground biomass of european gorse may be consumed by fire, but charred and fire-killed stems typically remain upright (Johnson 2001; CMB, SJB, personal observations).
European gorse generates seed banks with as many as 20,000 seeds/m2 within the top 6cm of the soil (Zenkiewicz and Gaskin 1978) and seeds can remain viable in the soil for at least 15 years (Hill et al. 2001). The seeds have a hard seed coat that typically requires scarification. Fire appears to accelerate seed germination, where it is suggested that an increase in soil temperatures during more severe fires may scarify the seed coat or volatilize organics within the seed that otherwise prevented germination (Rolston and Talbot 1980; Zenkiewicz and Gaskin 1978). In heat treatment experiments heating for 5 minutes at 105oC for 5 ins resulted in ~79% of seeds germinating (Butler 1976). Seeds can be dispersed several meters from an explosive seed dispersal mechanism.
Plant response to fire
Habitats dominated by european gorse are one of the most fire-prone types of shrubland (Baeza et al. 2002). Gorse can accumulate fuel rapidly (Baeza et al. 2002) and its leaves have high volatile contents making it highly flammable (Madrigal et al. 2012). Moreover, as it grows it retains its older dead branches and needles/pines meaning that it has a large volume of live volatile rich fuel but also a large volume of dry easily ignitable fuel. Hence European gorse burns rapidly and with high intensity. European gorse is classified as a pyrophytic shrub and it is noted as one of the best known fire-climax species in the UK (Mayhead 1990) and carries frequent, low severity fires.
European gorse is often a pioneering species in burned areas (Lee et al. 1986) and rapid growth is possible with 1 year old stands capable of producing 1100 lbs (dry weight) per acre in a single year (Hoshovsky 2000). Following low severity fires european gorse seems to reestablish mostly from resprouting, whereas growth from seeds tends to dominate following high severity fires.
European gorse occurs both in areas with natural wildfire regimes and in those with prescribed fires, it typically thrives in fire-maintained heathland (Zouhar 2005). European gorse is likely the UKs most clearly pyrophytic shrub that appears to not only encourage fire but is well adapted to and improved by fire.
Timing of life history
Perennial species. Seeds likely produced from second growing season. Flowering January to June.
Conservation status
None.
References
Baeza, M.J., De Luis, M., Raventós, J., Escarré, A. 2002. Factors influencing fire behaviour in shrublands of different stand ages and the implications for using prescribed burning to reduce wildfire risk. Journal of Environmental Management 65:199–208 [Empirical evidence; Academic literature]
Hill, R. L., Gourlay, A. H., Barker, R. J. 2001. Survival of Ulex europaeus seeds in the soil at three sites in New Zealand. New Zealand Journal of Botany 39: 235-244 [Empirical evidence; Academic literature]
Hoshovsky, M. C. 2000. Ulex europaea L. In: Bossard, Carla C.; Randall, John M.; Hoshovsky, Marc C., eds. Invasive plants of California's wildlands. Berkeley, CA: University of California Press: 317-321 [Empirical evidence; Academic literature]
Johnson, P. N. 2001. Vegetation recovery after fire on a southern New Zealand peatland. New Zealand Journal of Botany. 39: 251-267 [Empirical evidence; Academic literature]
Madriga,l J., Marino, E., Guilarro, M., Hernando, C., and Diez, C . 2012. Evaluation of the flammability of gorse (Ulex europaeus L.) managed by prescribed burning. Annals of Forest Science 68: 387-397 [Empirical evidence; Academic literature]
Mayhead, G. J. 1990. Fire protection in Great Britain. Commonwealth Forestry Review 69: 21-27 [Empirical evidence; Grey literature]
Rolston, M. P., Talbot, J. 1980. Soil temperatures and regrowth of gorse burnt after treatment with herbicides. New Zealand Journal of Experimental Agriculture 8: 55-61. [Empirical evidence; Academic literature]
Zabkiewicz, J. A.; Gaskin, R. E. 1978. Effect of fire on gorse seeds. Proceedings, 31st New Zealand Weed and Pest Control Conference. [Empirical evidence; Academic literature]
Zouhar, Kris. 2005. Ulex europaeus. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.usda.gov/database/feis/plants/shrub/uleeur/all.html [Expert opinion; grey literature]