Cork Oak (Quercus suber):
The Roles of Its Bark
Juli G. Pausas
Centro de Estudios Ambientales del Mediteráneo (CEAM)
Cork oak (Quercus
suber) is an evergreen tree native to the western Mediterranean Basin
countries of Portugal, Spain, Morocco, Algeria, Italy, Tunisia, and
France. The main difference between this species and its relatives is
its unique outer bark. Each year, cork oak produces a layer of suberized
phellem cells that are not shed but rather accumulate in the form of
annual rings. This external layer of cork can reach a thickness of more
than 15 cm and constitutes the tree’s main protection from fire and
In the Mediterranean Basin, cork has been used by humans at least since
ancient times (Egyptians, Greeks, Romans) for sealing jars, for roofing,
for making beehives, and in many other ways. A French Benedictine monk
(Dom Pierre Pérignon, ca. 1638–1715), is considered responsible for the
widespread use of cork stoppers to preserve wine in bottles (Figure 16).
Since the 1600s, cork use has grown with the wine industry. Currently,
cork is also still used for insulation, decoration, and fishing buoys.
Cork is harvested manually at 9-12 year intervals (when it is about 3-cm
thick) by skilled local people. Cork stripping has to be done with care
and when the phellogen is active (i.e., in late spring and early
summer). If performed at an inappropriate time, stripping may kill parts
of the stem or even the entire tree, because the inner bark is removed
down to the vascular cambium.
Currently, it is very difficult to
understand the success of the wine industry without due consideration of
cork. But, perhaps more importantly, the cork industry is the main
driver of cork oak woodland conservation because cork production depends
on sustainable woodland management (Figure 17).
The principal ecological role of the corky bark is to protect trees from
wildfire damage; the strong insulating characteristics of cork shields
inner stem tissues from heat. Cork oak evolved in fire-prone
Mediterranean ecosystems, and its thick outer bark confers on this
species a distinct advantage over its competitors. Thanks to their thick
insulating bark, cork oaks also resprout vigorously from stem buds, and
thus even when the crown is damaged, it recovers quickly after fires (Pausas
The capacity to resprout from buds on the upper trunk after fires
is a rare feature among tree species, shared with some Eucalyptus
species and few others. Finally, although other tree species living in
fire-prone ecosystems have evolved corky barks, none have outer bark as
thick or as valuable as cork oak.
(1997) Resprouting of Quercus suber in NE Spain after fire.
Journal of Vegetation Science 8: 703-706
photograph at top of the page shows a cork oak that has had the bark on
its lower trunk removed. Note that the bark higher up is still
intact. Photo by Ian Francis (Australia).
the second page of Bark Ecology.