Cork oak landscapes in Portugal

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The choice of the sub-domain

According to Costa and Pereira (2004), the economy of the cork industry in Portugal depends decisively on two aspects:
(1) the production of cork, as a supplier of industrial raw material; and
(2) the production of natural cork stoppers, as a determining factor, to justify the high costs of the raw material.
Based on these two most relevant aspects of the Portuguese cork industry, and given the vast extent of the cork domain, where several industrial sub-sectors thrive, we have narrowed down our study to one of those two sectors; however, we will provide a brief overview of the main subsectors that comprise the domain of cork (Section 1.8, p. 30).
The primary focus of our study is the cork stopper. Our motivation relates with the fact that the manufacture of cork stoppers is the backbone of this chain of production – i.e., the forestry production of cork oak – since it is the product that holds the most significant share of exports within the scope of the Portuguese agriculture sector. Albeit its light consumption of 30-40% of raw material, yet generating 80% of added value, the cork stopper is the cornerstone of the cork oak chain of production in the national exports – a status still up to date (see INPI 2005).
Cork stoppers are a manufactured product that depends entirely on the domain of cork. Therefore, we will, to some extent, address the super-domain of cork – the source of the raw material – since the typology of cork stoppers is determined depending on the quality of the cork. This means that cork quality – which is conditioned by the high calibre (thickness) of the plank – is a critical factor to determine which final products are obtainable from a given cork plank, right after being stripped from the tree.
The same happens with regards to the intermediate manufacturing processes to transform this raw material, depending on the thickness of the plank. There is one simple goal underlying the determination of the quality and the future of a cork plank: to maximise the use of the extracted cork. Thus, depending on the quality of the cork, one may obtain natural cork products, on the one hand, or products composed of agglomerated cork granules, on the other, where the former require the highest quality and inherent maturity of the tree. In contrast, the latter use cork classified with a lower quality, e.g., leftover pieces of broken planks, lower parts of the tree and cork planks extracted from juvenile trees, just to name a few.

Cork bark – an ancient raw material

As a raw material, cork has many applications and has been used by man since ancient times. The first known references to the application of cork point to the floating properties of this material. One of the first applications of cork in ancient times was as a floating device, e.g., as buoys in the fishing activity – an application that is believed to have been discovered by the Egyptians in the 4th century BC (see Taber, 2009). Gil (2014) states that cork is a material whose “applications have been known since Antiquity, especially in floating devices and as stoppers for beverages, mainly wine, whose market, from the early twentieth century, had a massive expansion, particularly due to the development of several cork based agglomerates.” (p.1). The first references to its applications date back to more than 3000 years BC, namely not only in the floating devices we have already mentioned, but also as a sealant, as material to produce footwear and beehives, or even to insulate houses, as well as applications in household utensils or for therapeutic purposes (see Gil, 2015). According to Taber (2009), no one knows precisely when someone decided to seal a wine container with cork for the first time. However, it is known from the writings of the Greek historian Thucydides that “the peoples of the Mediterranean began to emerge from barbarism when they learned to cultivate the olive and the vine” (p.8). This author further mentions that the discovery of pottery circa 6000 BC made it possible for people to store and trade wine – the vast majority of trade in those times relied on only three products: wine, grain, and olives or olive oil. The most popular containers were amphoras and soon were adopted by winemakers, for they could carry a large variety of both dry and liquid products. These amphoras were used for nearly 6000 years and could be found in several sizes. The first pieces of evidence of a kind of stopper to prevent the wine from turning acidic9 belonged to the Egyptians. By circa 3000 BC, Egypt was the centre of wine production. The methods they used to produce wine are clearly described in frescoes that can still be admired today. However, by that time, cork was not only used in Egypt but also in Babylon and Persia. In addition to its use in fishing gear, cork has also been found in Carthaginian cemeteries in Sardinia in engraved sheets, supposedly used to store precious materials, and also as the lids of urns found in some “nuraghi” – cone-shaped monuments. In some Egyptian sarcophagi, amphoras with cork plugs were also found to store food (see APCOR, 2019).
For economy of space, further notes regarding historical pieces of evidence are available in Annex 1. The inclusion of this topic intends to demonstrate the cultural heritage of this domain.
Notwithstanding, we will highlight in the next lines the pieces of evidence that are closely related to the Portuguese legacy.

Some historical facts in the international context

The systematic exploration of the cork oak trees that characterises the Iberian Peninsula and which still exist today in Catalonia and Portugal only started in the 18th century, when the production of cork stoppers became the primary goal. It was also during this century that the first works on the chemical composition of cork were developed, mostly in studies carried by an Italian chemist named Brugnatelli. The production of the first compendium on subericulture (the cultivation of Suber family trees) dates back to this period as well. By the end of this century, in 1790, the compendium “Azinheiras, Sovereiras e Carvalhos do Além-Tejo” [holm oaks, cork oaks and oaks of Além-Tejo] was published and signed by a Portuguese author, Joaquim Pedro Sequeira (see APCOR 2019).
In 1700, cork stoppers began to be used and in 1770, with the beginning of the Port wine trade, the cork stopper industry started to flourish in northern Portugal associated with this sector (see APCOR, 2019). Taber (2009) mentions that this was the era when cork stoppers had their most significant boost given the emergence of new bottles – in a more stable shape for both standing on the table and stocking them in stacks – in addition to the signing of the “Methuen Treaty between Portugal and England. This treaty was both a military and a commercial accord that gave privileged trade access to both countries in the other’s market” (p.14).
In 1750, the first factory for the manufacturing of stoppers was set up in Girona, Spain, and one hundred years later, the industry was already extended across the country. Finally, in the 19th century, France, Italy and Tunisia decided to join the systematic exploitation of cork oak forests, and countries as different as Russia or the United States also started planting these trees (see APCOR, 2019).

Portuguese cork history in a nutshell

According to APCOR (2019), Portugal was a pioneer regarding environmental legislation, since the first agrarian laws that protect the cork oak forests appeared in the beginning of the 13th century, more precisely in 1209. In 1292, King Denis prohibited the felling of cork oaks in Alcáçovas (Alentejo).
The first reference to cork extraction and use of bark in the tanning of animal skins dates back to the year 1320. Later, in 1438, more references are made to the export of Portuguese cork to Flanders.
During the Portuguese Discoveries (15th – 16th century), the builders of ships and caravels that set out to discover new worlds used cork oak to manufacture the parts that were more exposed to the weather. They argued that the “sóvaro”10, as it was called in those times, was the best bonding material for the ships: besides being extremely resistant, it never rotted. Further applications were also found in those centuries, namely in the construction industry: in 1510, several objects made of cork were represented in the window of the chapterhouse of the Convent of Cristo, in Tomar; and in 1560, in two other convents: “Convento dos Capuchos”, in Sintra, and the Carmelitas, in Buçaco. These two convents used cork on the walls and ceiling of the cells (see APCOR, 2019).
Further mentioned by APCOR (2019), several initiatives have been launched in recent decades, aiming at research and the design of international standards for the cork industry. The Confédération Européenne du Liège11 (CE Liège), founded in 1987, stands out: formed by cork federations belonging to several countries, this organisation presented in 1996 the International Code of Cork Stopper Manufacturing Practices, an essential document for quality control in the manufacturing of stoppers.
In the 21st century, cork uses have been spreading, particularly to innovative areas such as Design for Sustainability and Eco-Design. Cork has consistently proven to be a field of interest whose scope of novel applications has been continuously evolving, for new generations of artists seek to create everyday objects from materials that are 100% natural and that contribute to environmental sustainability. Concerning fashion, cork occupies an increasingly prominent place, as well as in other industries, such as transport and sport.
This raw material has been used for many purposes due to its intrinsic properties. It can be found on NASA12 and ESA13 shuttles; competition boats; tennis and cricket balls; and even incorporates internationally awarded design pieces. Beyond these exotic applications, cork is commonly used in the construction industry as acoustic, thermal and vibration insulation (walls, ceilings, floors); false ceilings; wall covering, floors and ceilings; baseboards; linoleum; granules for filling spaces and mixtures with mortars; insulating and expansion or compression joints; as well as for industrial purposes, such as anti-vibration for machinery and insulation for industrial cold (see Gil, 2007). These are just a few of the many applications of cork.
In brief, what stands out in cork is the quality of this excellent raw material and particularly its multiple modern applications and extraordinary ability to meet the current generations’ market demands. From footwear industry to pharmaceuticals, and even space shuttle engine components, along with a multiplicity of other applications, we have been witnessing the fast-technological development of the cork industry given the current social trends of ecological awareness and related market requirements.

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The Mediterranean endemic cork oak tree

Cork comes from the cork oak tree, which is known by the scientific community as Quercus Suber L.
The cork oak (Quercus Suber L.) is an evergreen broad-leaved tree, from the Fagaceae family, that grows in the forests located in the coastal regions of the western Mediterranean basin. Cork oak trees can live for centuries, between 200-250 years (some authors point at 250-350). They are usually 15-20 meters high, but under ideal conditions, they can reach 25 meters. The stem’s diameter at a man breast’s height can reach 200 cm. The leaves are 4-7 cm long, dark green on the top and paler underneath, thus forming a round-topped head with a glossy green colour. The acorns are 2-3 cm long with a deep cup. The most interesting characteristic of this tree is its outer bark formed by a continuous layer of suberised cells that constitute the external protection of the stem and branches, which is commonly known as cork – a naturally renewable raw material. The bark can be up to 20 cm thick and corresponds to the dermal system that protects the tree from forest fires (see Boshmonart, 2011; Gil & Varela, 2008).
The principal use of this tree is as a source of raw material for industry, namely its cork, which is obtained by stripping the bark from the trunk. Since the natural goal of the bark is to serve as a measure of protection for the tree during forest fires, it re-sprouts from the stem after the tree suffers any fire damage (see EUFORGEN, 2020). According to Boshmonart (2011), this fire-resistant property has been an evolutionary adaptation to the Mediterranean climate where fire is an important ecological factor.
The cork oak is a tree that thrives in areas exposed to both drought and heavy rainfall. It requires a mild annual temperature and prefers sandy and lightly structured soils. Forest landscapes with cork oaks are biologically diverse, which is why many cork oak forests are protected ecosystems in Europe (see EUFORGEN, 2020).

The cork oak bark

Cork is obtained by stripping the bark from the trunk – a procedure that occurs mainly in summer. The cork bark is manually extracted with the help of specific axes and comes out from the tree in the form of semi-tubular planks, leaving the tree with a thin layer of new cork still covering the functional secondary phloem14 on the trunk. The first moment of debarking a young tree has to comply with strict forestry guides: it cannot occur before the tree has reached 0.7 meters in perimeter and 1.3 meters high. The cork oak tree cannot be totally stripped from its bark, for it would not thrive if that were to be made (see Gil, 2007).

Table of contents :

The domain under focus
Theoretical framework, purpose and methodology
Research questions
Outline of the thesis
1. Description of the domain: cork
1.1. Motivation
1.2. The choice of the sub-domain
1.3. Cork bark – an ancient raw material
1.3.1. Some historical facts in the international context
1.3.2. Portuguese cork history in a nutshell
1.4. The Mediterranean endemic cork oak tree
1.4.1. The cork oak bark The layered structure of cork bark
1.5. Cork oak forests
1.5.1. The Portuguese forest
1.6. Cork oak landscapes in Portugal: the montados
1.7. Cork production – an economic asset
1.8. The three subsectors of the industry of cork
1.8.1. From the forest to the bottle – a short overview of a natural cork stopper’s journey
1.8.2. The transformation subsector The quality of the cork bark after boiling
1.8.3. Cork stoppers – a product from the transformation sub-sector In the line of manufacturing natural cork stoppers In the line of manufacturing agglomerated cork stoppers Natural cork discs
1.8.4. Cork stopper typology
1.8.5. The quality of cork stoppers The classification of cork stoppers TCA, the chemical compound 2,4,6 – Trichloroanisole
1.8.6. Standardisation in the scope of the manufacture of stoppers
1.8.7. ISO: International Organisation for Standardization; ISO / TC87 – Cork
2. Corpus
2.1. Corpus definition
2.2. Sinclair’s definition
2.3. Pearson’s choice: McEnery and Wilson’s definition
2.4. McEnery and Wilson’s definition
2.5. Baker, et al. definition
2.6. Costa’s definition: specialised corpus
2.7. An overview of pioneering studies in Corpus Linguistics
2.8. Terminology and corpora
2.9. Criteria for corpus design
2.9.1. Four main criteria for corpus building
2.9.2. Machine-readable
2.9.3. Size
2.9.4. Sampling
2.9.5. Balance
2.9.6. Internal and external criteria The broad external criteria The broad internal criteria
3. TermCork: A corpus-based research to perceive domain-specific concepts
3.1. Domain-specific corpus: purpose and design
3.1.1. Corpus criteria design: text type, format and publication date
3.1.2. The communicative setting
3.1.3. The language eligibility criteria
3.1.4. Composition of the text collection, written in Portuguese
3.2. The corpus of analysis
3.2.1. Composition of the multilingual text collection Multimodal corpora
3.3. Corpus management
3.4. Corpus processing
3.4.1. Querying the corpus with CQL
3.5. Ten (10) definitions to organise a typology of cork stoppers
4. Definition
4.1. Intensional definition
4.1.1. Essential characteristics
4.1.2. Differential characteristics
4.1.3. Descriptive characteristics
4.2. Analysis and representation of textual definitions
4.2.1. Linguistic analysis of Definition 1
4.2.2. Linguistic analysis of Definition 2
4.2.3. Linguistic analysis of Definition 3
4.2.4. Linguistic analysis of Definition 4
4.3. The relevance of lexical markers for modelling special knowledge information
5. Conceptual analysis
5.1. Conceptual analysis of Definition 1
5.1.1. Function, parts and substance
5.2. Conceptual analysis of Definition 2
5.2.1. Complementary information found in Definition 2
5.3. Conceptual analysis of Definition 3
5.4. Conceptual analysis of Definition 4
5.5. A brief overview
6. Building the ontology
6.1. From CmapTools to Protégé – Definition 1: <Stopper>
6.2. The formal description and annotations of CorkStopper in Protégé
6.2.1. The description of <NaturalCorkStopper> in Protégé
6.2.2. The description of <MonoPieceNaturalCorkStopper> in Protégé
6.3. Finishing processes
6.3.1. Finishing process or not: a differential characteristic modelled with complex axioms
6.3.2. The Boolean operators “or” and “not” to express the manufacturing stage
6.3.3. Semi-manufacturedCorkStopper, the goal of the operator “not”
6.3.4. The Boolean operators and the plurality of syntaxes to express them
6.3.5. The extension of FinishingProcesses Systematisation of concepts falling under the category of FinishingProcesses
6.3.6. A competency question to validate the systematisation: what is an InkMarkingOperation?
6.3.7. What is a CorkStopper with FinishingProcesses? Description of Semi-finishedStopper in Protégé An example of <Semi-finishedStopper> classification
6.3.8. Description of the concept FinishedStopper An example of FinishedStopper
6.4. Hierarchical systematisation of the associative relations to relate CorkStopper and FinishingProcesses
6.4.1. Domain and range of the relation hasShapeElementEdge
6.4.2. Ontological triples: a kind of declarative assertions
6.4.3. Classification of two instances as Semi-finishedStopper
6.5. Additional information to the definition: the case of the “technical cork stopper N+N” 273
6.5.1. Descriptive characteristics
6.6. Some remarks: the long name of concepts
6.7. Some conclusions
Overall remarks
Some insights
Future work


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