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Karst/ Carso

• Overview
• History of the Karst
• Classical Karst
  • Sinkholes in the classical Karst
  • Ponds in the classical Karst
  • Flora in the classical Karst
  • Bora
  • Local gastronomy in the classical Karst
• References

Overview

Karst is an interesting natural phenomenon, rich with landscape shapes and underground cavities. It is found all over the world, where water interacts with soluble bedrock such as limestone or dolostone. Rain picks up CO₂ in the atmosphere or in the soil, and makes carbonic acid (H₂CO₃). This mildly acidic water begins to dissolve the surface of the soluble bedrock. Over time, dissolved cavities enlarge, shaping surface rock and making rich underground drainage system and many caves.

The origin of the topography comes from the German name for Kras, a region in Slovenia partially extending into Italy where it is called Carso and where the first scientific research of the Karst topography was made. This region, called Classical Karst, contains many caves, have a unique landscape and biological characteristics. During the winder, strong wind, called Bora, flows. It influenced the architecture of villages and towns. The region is also famous among climbers, since it contains many rocks, warm temperatures, and almost no snow during the winter, which allows climbing all over the year.
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History of the Karst

The first scientific approach to explore the phenomenon was made by Slovenian JV. Valvazor, who already in the XVII century communicated English Royal Society about the aspects of the Karst region. Later, in 1784, Austrian JN. Nagel described and sketched some caves of the Karst of Trieste. The first theory about the Karst topography was formulated in 1771 by brothers Gruber from Ljubljana. They postulated that crashes of antique caves came from the activity of the underground rivers. The theory explained the origin of some landscape forms and the disappearance and reappearance of some lakes in the region of the the Karst. However, at that time the theory was too fantastic and was forgiven. In 1778, French Baltasar Hacquet presented a theory of corrosion. He reasoned that the rain contained acid, which corroded calcium from the stone. The theory was right, but at that time the scientists did not know neither about the acid in the rain, nor the calcium in the stone. Hacquet was also forgiven. Now we know that both brothers Gruber and Hacquet were right.
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Classical Karst

The Classical Karst is extended for 450 km² from Isonzo river in the West, Vipacco river in the North, the most westerly part of Brkini hills in the East, and the Istria peninsula in the South. The Karst plateau is extended in direction SE-NW, slightly descending towards West. The oriental part has an altitude of 400 m above sea level, while the part, most proximal to Isonzo river, is elevated about 100 m above sea level. The town of Se�ana in Slovenia is the center of the Classical Karst.

The speed of corrosion depends on the origin of the rock, the amount of the precipitation and the medial seasonal temperature. Classical Karst contains all favorable conditions, and, therefore, comprises many caves and other cavities. The superficial has a typical form, composed of hundreds small furrows, cracks and holes, and round- or prolonged-shaped pockets.

In Slovenia, the most famous caves are Vilenica (the oldest tourist cave in the world), Lipica cave, Divaca cave, Kacna cave, Postojna cave and �kocjan caves. �kocjan caves have about 5 kilometres of underground passages, caves more than 200 meters deep and many waterfalls. The Reka River disappears underground in Velika dolina, flows underground through Skocjan caves for 34 km, and then close to Adriatic Sea it becomes the source of the Timav River. They belong to one of the UNESCO world heritage sites. Postojna cave is a 20,570 m long cave system. In Italy, there is the Grotta Gigante, the biggest tourist cave in the world, and many more smaller caves. Caves of the Karst usually are dry, and contain stalactites and stalagmites, which are formed during millions of years.

The Karst has another interesting phenomenon, namely lakes, which are fed up with an underground water sources. Doberdo del Lago, found in the Italian region Friuli-Venezia Giulia, is one of a few examples, that is fed by underground rivers. In Slovenia, close to Cerknoca there is Cerknica lake, which water level have cdrastic seasonal hanges.
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Sinkholes in the classical Karst

The landscape of Karst comprise many sinkholes (dolina in Italian). When the underground cavity is close to the superficial of the earth, with time it collapses and makes a depression in the landscape- a sinkhole. They have various shapes and sizes. Italian Karst has more than 6000 sinkholes, of which almost 400 have the diameter more than 100 m. The depth can be from few meters to about 70 meters. Depending on the depth, the borders of a sinkhole could be gentle or steep. The majority of sinkholes are present in the central part of the Karst plateau, where bigger masses of soluble bedrock are. For example, in Monrupino village there are more than 100 sinkholes per km².

Sinkholes present an interesting biological phenomenon- a microclimate with a thermal inversion. Usually, going downward, the temperature increases (0.6 C⁰ every 100 m). Going down in a sinkhole, the temperature decreases for 7 C⁰ every 100 m, thus, 12 times more! Moreover, the North to South orientation is also thermally inversed. The sun shines most of the time to the north face of a sinkhole and, thus, on this side it is warmer than on the south side. The microclimate is particularly visible during the spring and the autumn. Different plant species grow and flower at the altitudes, which differ only several meters!
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Ponds in the classical Karst

One more interesting phenomenon of the Karst is Pond, called Stagno in Italian, and Kal in Slovenian. These modest size water sources were used to water cattle in the past. They support local communities of plants and water animals, increasing biodiversity of the region. Moreover, ponds enrich the view of the environment.

The bedrock of the Karst is composed of soluble minerals, thus, rainwater does not remain at the superficial of the land. For that reason, it was important to keep ponds as a water source for cattle. Most of the ponds in the Karst had natural origin, but later were modified in order to increase the amount of water in them.



In the province of Trieste, there have been at least 50 ponds in the past. Around 1970, only 30 of them remained, and at the present day, even less remained. These ponds have a diameter from 5 to 30 m, are deep from 30 cm to 3 m, and have a volume from 5 m³ to 1000 m³ (data of 1970).

In the province of Trieste, the biggest one in terms of superficial area and volume is the pond of Contovello. In 1965, its superficial area was 936 m², volume- 1035 m³, and the depth- 2.2 m. At present it is a bit smaller.

The water level oscillates during the season. Ponds contain the maximal level of the water at the end of the autumn and at the end of the spring, while the minimal levels are in August and in February. During these periods, the level of the water could increase or decrease up to 0.5 m. The temperature of the water varies during the day and the night, and during the season, especially in small ponds. The level of oxygen and nutrients is also altering seasonally. Ponds are become frozen during the winter. Therefore, the living conditions for plants and animals are not favorable ones.

Nevertheless, there are growing vertical plants, mainly of Typha, Heleocharis and Juncus genus, and immerse plants, such as Helodea, Chara, Potamogeton and Ceratophyllum. Lemna genus plants are found in some of the ponds.
At present, ponds are not used any more; they are decaying because of both natural and anthropogenic reasons. However, there are attempts to save them.
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Flora in the classical Karst

During the Bronze and Stone Age, the Karst was covered by oak forests (Quercus pubescens), which were gradually cut by man. Venice was built from oaks, cut in the northeast part of the Mediterranean Sea, including Trieste, Istria, Cres and Krk islands. Two less demanding plants, the hornbeam and the ash-tree replaced oak trees. They were widely used for economic human activities.

At the beginning of the XIX century, because of the construction of the railway, reforestation works were started in the province of Trieste. Coniferous trees, such as black pines from Austria, Himalayan cedars ( Cedrus deodara ), atlantic cedars ( Cedrus atlantica ), Greek firs ( Abies cephalonica), Caucasian firs ( Abies nordmanniana ) and others were introduced as experimental species in Bazzoni wood. However, during the first and second word wars, most of them were cut. The remaining ones are growing difficultly, and does not disseminate around. An exception is black pine, which diffused widely in the area. Today the main tree species in the Karstic wood are Quercus pubescens, Pine nero, Ostrya carpinifolia and Fraxinus Ornus. The bushy area is made of juniper, sumac, elderberry and hawthorn. They were used for centuries in medicine, crafts and industry.

A sinkhole forest is different from a forest of the Karst plateau. Sinkholes have cooler and wetter microclimate. The deeper and narrower a sinkhole is, the bigger temperature difference between inside and outside the sinkhole exists, because colder area is heavier, and it remains at the bottom of a sinkhole. The most diffused trees in this forest are Asarum europaeum and Carpinus betulus. The latter one, white birch, likes humid and fertile terrain. Once it was growing in Central Europe plains, but as they became agricultural areas, now the birch is growing only in small marginal areas.

Even if it is colder, the sub-forest of a sinkhole forests is rich herbal species, because the conditions prevent from cold wind. These herbs are blooming early in the spring, when the trees are without the leaves and pass the sunshine to the ground. The peak of blooming is in March and April.

Today only about 30 % of the province of Trieste is covered by forests.

The meadows of Karst contain many plant species, because of their geographical conditions. Mediterranean Sea, Alpine and continental plants found suitable conditions to grow there. During the last centuries, cattle breading and pasturing were common human activities, which allowed preserving plant diversity.

Due to deforestation, some areas of the Karst became moorland with emerging rocks, harsh arid climate during the summer and strong wind regularly blowing. Thus, only the least demanding plants can withstand such conditions. To date, thanks to deforestation, the situation changed in the moorland. Many plant species are growing there, and the Karstic moorland with the spring flowering and the autumn colors became a characteristic landscape of the Karst.
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Bora

An integral feature of the Karst region is strong wind, called Bora. It is a northeastern katabatic wind (which flows downhill), found in the Adriatic Sea, Greece, Russia and Turkey. Its name derives from the Greek mythological figure Boreas, the North Wind. Because the region separates the Adriatic coast with Mediterranean climate from the Julian Alps range with continental climate, two air masses meat each other and tend to equalize. As a result, extreme Bora wind often occurs.

It has influenced the region's traditional lifestyle and architecture. Towns and villages on the coast are built densely with narrow streets in part because of the wind. Buildings in several towns and villages have short roof tiles or even stones on their roofs to prevent the roof tiles from being blown off. Chains and ropes are occasionally stretched along the sidewalks in downtown Trieste to facilitate pedestrian traffic.
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Local gastronomy in the classical Karst

Karst region in Italy and Slovenia is famous for its vine, called Terrrano. Its quite source red wine, made from local grapes. In villages, it is served by local people in their house for a short period of time. The place, where wine is served, is called osmizza. The name comes from the Slovenian world "osem", which means eight, since historically they were allowed to be opened only for eight days per year. Together with wine, prosciutto, another typical product from meat, could be found at osmizza.
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References

S. Polli & G. Alberti (1968-1969) Atti del museo civico di storia naturale di trieste volume XXVI, issue 4, N. 5-6, p. 81-127.
Carsiana botanical garden
About sinkholes, pdf document in italian
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