English Oak
Quercus robur
Family: Fagaceae
Fire effect on plant
English oaks can survive fire. Young trees may be top-killed but below-ground buds may survive
Key traits
The English oak is a long-lived, deciduous tree. The seedling of this species has a very strong and quick-growing tap-root that can elongate at the rate of 3-7 mm per day and which is usually 20-30 cm long at the end of the first year (Jones, 1959). This below-ground structure allows survival through top-killing, whether that be cutting or fire (Petersson et al, 2020). New vigorous stems develop and form their own adventitious roots. After 10-20 years, the oak may grow tall enough to reach a height where they are invulnerable to surface fires, as leaves and buds are held above the flaming zone and a thick, deeply-fissured and insulating bark has developed (Jones, 1959). Fires which are severe enough to injure the cambium may cause 'fire-scars' (vertical strips of dead cambium which subsequently become depressions) and trees may become stag-headed.
Oaks produce large acorns which may survive fire buried in the seedbank. Seedlings can establish in relatively dark understory conditions, but require ample irradiance for survival and growth once energy reserves of the cotyledons are exhausted (Johnson et al, 2018), and so disturbance such as fire that opens up the canopy may benefit seedling establishment (Petersson et al, 2020). There is some evidence that English Oak germination may be enhanced by smoke/charcoal, with higher germination rates seen for acorns treated with smoke or charcoal (90-94% germination) relative to untreated acorns (87% germination; Reyes et al, 2006).
Plant response to fire
English oaks are considered to be ‘fire adapted’ due to their high resprouting capacity and thick bark (Petersson et al, 2020). Fire is suggested to be an integral part of temperate oak ecosystems, with oaks benefitting from periodic fire that increases light availability and allows faster growth rates (Petersson et al, 2020). In North America, failed oak regeneration has been linked in part to fire suppression during the last century (Brose et al, 2001; Dey et al, 2019). Thus, prescribed burns and stand thinning to increase light availability are used extensively in the United States to restore and regenerate oak ecosystems (Dey & Hartman, 2005).
Timing of life history
Long-lived tree. Seeds produced from ~40 years of age (Forestry England 2024). Flowering April to May.
Conservation status
None.
References
Brose, P. , Schuler, T. , van Lear, D. , & Berst, J. (2001). Bringing fire back: The changing regimes of the Appalachian mixed‐oak forests. Journal of Forestry, 99, 30–35 [Empirical evidence; Academic literature]
Dey, D. C. , Knapp, B. O. , Battaglia, M. A. , Deal, R. L. , Hart, J. L. , O'Hara, K. L. , … Schuler, T. M. (2019). Barriers to natural regeneration in temperate forests across the USA. New Forests, 50(1), 11–40. [Empirical evidence; Academic literature]
Dey, D. , & Hartman, G. (2005). Returning fire to Ozark Highland forest ecosystems: Effects on advance regeneration. Forest Ecology and Management, 217, 37–53. [Empirical evidence; Academic literature]
Johnson, P. S. , Shifley, S. R. , Rogers, R. , Dey, D. C. , & Kabrick, J. M. (2018). The ecology and silviculture of oaks (3rd ed.). Wallingford, UK: CABI. [Empirical evidence; Academic literature]
Jones, E. W. (1959). Quercus L. Journal of Ecology, 47(1), 169–222. [Empirical evidence; Academic literature]
Petersson LK, Dey DC, Felton AM, Gardiner ES, Löf M. (2020) Influence of canopy openness, ungulate exclosure, and low-intensity fire for improved oak regeneration in temperate Europe. Ecol Evol. 10(5):2626-2637. [Empirical evidence; Academic literature]
Reyes, O., Casal, M. (2006). Seed germination of Quercus robur, Q. pyrenaica and Q. ilex and the effects of smoke, heat, ash and charcoal. Annals of Forest Science 63: 205-212. [Empirical evidence; Academic literature]