Apologies for the tardiness today. The server's been down due to recent electrical outages on campus. – Daniel
It's not often I permit photographs with people in them to appear on BPotD, but exceptions are occasionally warranted – in this case, for scale. Today's photograph is courtesy of Miguel Rodrigues (the photographer) and Pedro Nuno Teixeira Santos (pictured) of Portugal. Thank you to both of you once again!
Pedro sent along the image and these measurements (by Miguel) of the tree: the height is 19m (62 ft.), the circumference of the trunk is 5.91m (19ft.) and the highest measured diameter of the crown is 37m (121 ft.). As Pedro succinctly states: “It's an amazing tree... one of the biggest cork oaks I have ever seen.”. Pedro has also written about this plant (accompanied by more photographs) in Sua majestade on the weblog, A sombra verde.
Quercus suber, or cork oak, is well-known for the renewable resource it provides: cork. The thick, rugged outer layer of bark can be harvested multiple times over the life of the tree, the first time at 25 years of age and then after every nine to twelve years. The individual in today's photograph appears to have different sections of it harvested in different years, with the reddish area on the right being the most recent site of cork collection. From some trees, the harvest can be one tonne of cork; considering its density, that's an impressive volume of cork.
The cork produced by Quercus suber is high in the waxy substance known as suberin. This, in addition to the quantity of bark produced, provides its most-desirable qualities: elasticity, near-impermeability, and low-density. Wikipedia covers the uses of cork: bottle stoppers, fishing floats and buoys, musical instrument-making, floor tiles and concrete-cork composite materials. If you are interested in the harvesting and production process of wine corks, read natural cork production from one of the cork manufacturers.
An excellent article on Quercus suber is available from ecology.info: Cork Oak (Quercus suber): The Roles of its Bark by Juli G. Pausas of the Centro de Estudios Ambientales del Mediteráneo in Valencia, Spain.
Quercus suber is native to southwestern Europe and northern Africa (in addition to where it grows naturally, it is also cultivated throughout the region; Portugal is responsible for half of the production). The Plants for a Future Database details a few non-cork uses of the species. If you'd like more photographs, visit Friedrich Lohmüller's page on Quercus.