The pedogenesis of the Etna lava
The Etna lava embracing the vine
It is often said that the volcanic ground, the Etna lava, represents a great heritage for those who live on Etna.
The lavic soil is very fertile and lends itself well to the cultivation of vines. Surely, this simple sentence represents a popular truth known to all wine enthusiasts. Nonetheless, a newly formed lava field looks harsh, desert-like and completely unsuitable to life for several years. This apparent paradox has an explanation in the concept of soil and in the pedogenesis process that we tried to describe at best in the previous articles (as in the The soil and the Etna wines ). This process is particularly interesting and peculiar on the Etna lava.
The process of recolonisation, i.e the return to life, on the Etna lava fields, depends mainly on the abiotic phenomena that “degrade” the bedrock and create ideal conditions for the development of first organisms. The young volcanic products are “inhospitable” also for their vitreous nature, hardly changeable by exogenous agents. Instead, in mineralized soils are favoured the processes of alteration of crystalline structures and, consequently, there are many more nutrients available for life.
Therefore, to give life to a soil, also the surface of a young Etna lava must undergo processes of mechanical erosion and chemical alteration; always supplied by water (rain).
For example, during the pedogenesis process of basaltic lavas, the plagioclase – typical material of the Etna- alters to different new components, including the clay minerals, which are basic compounds of a fertile soil.
The importance of the age of lava for the formation of a fertile soil.
Hence, it’s understandable how the mosaic of the vegetation that is created is directly related to the conditions of the lava surface and then its age. Lichens are the first colonizers of lavas; for example, the Stereocaulon vesuvianum (characteristic of the Etna) colonised the lavas of the 1910 eruption after only 6 years. However, this also means that for 6 years that ground has been completely infertile. The popular belief concerning the high volcanic fertility is only true when the lava surface finally turns into soil.
The lichens build the soil that fills the fissures of the lava rough surface, catching the organic matter and the rock deteriorated by weather agents. This process introduces the first invasive vascular plants (pioneer species) that grow exactly from the fissures so altered. In this matter, the presence of the pioneer species as the Genista aetnensis and Spartium junceum (brooms) play a key role, since these species, both leguminous plants, fix the atmospheric nitrogen directly into the soil. This natural fertilization process creates over time a better environment for more complex plants that require a stable cycle of mineral elements.
The vegetable succession
In the vegetal succession of pedogenesis – that is the theory according to which in a given site different phytocoenosis (vegetation in general) occur in a specific time sequence – are distinguished the primary and the secondary successions.
The primary succession begins from an infertile ground and progressively increases in complexity up to a mature stage. The secondary succession, as for example the vineyards, begins after that the pre-existing vegetation cover has been removed or remodeled for natural or anthropic causes. This is the case of a cultivated field that has been abandoned; or a wood that has been removed, or a fertile lava field that is assigned to wine-producing use.
From a newly formed lava to a fantastic Nerello Mascalese vineyard elapses the entire process of erosion and alteration, the pedogenesis, the leaching (that contributes to the pedogenesis and removes soil too) and all the vegetal primary succession. For example, at an altitude of 700 meters, if no action is taken with machines to crumble the lavas and artificially facilitate the formation of the soil, it will take at least 2 or 3 centuries. Of course, the timing varies depending on the environmental conditions in which the lava is located (altitude, solar radiation, average annual temperature, raininess, etc).
The lava of Palmento Martinella
The PalmentoMartinella, inside the vineyards of the Emilio Sciacca Etna Wine winery, is located on the lower north-east side of Mount Etna in the geological environment of the lavas of the formation Pietracannone. These lavas are the eruptive products of the Mongibello, the last volcanic phase of the Etna, i.e the last 15.000 years of the volcano history. Particularly, the lava flow that covers the entire zone is the Piano Arrigo one, so the lower member (the most ancient) of the formation Pietracannone, with a time range between 15.000 and 3,900 years ago.
The lava field rises still today immediately south of the town Linguaglossa and shows a “aa” type of morphology, i.e. with a particularly rough and irregular surface. Most of the lava flow is today covered by soil and alluvial deposits, as it also occurs in the vineyards of the Martinella. This lava originally had a light grey colour, with a fabric (mineral texture), mainly organized in small crystals (microcrystalline texture). Only plagioclase, an essential mineral in the fertilization process, was occasionally present in the form of crystals with larger dimensions. After thousands of years of erosion and pedogenesis, it has turned into a soil 84% sandy, extremely rich in nutrients, with a pH of about 6,3 particularly favourable to the cultivation of the vine.
Recent and regular analyses of the soil reveal high values of assimilable iron, as well as calcium and magnesium.
The high values of assimilable nutrients and the sub-acid PH of the soil are perfectly compatible with what was mentioned above about the Etna lavas and enhance the enological value. Indeed, also the resultant wine matches with these analyses and considerations. Particularly, these kinds of soils and the corresponding high draining capacity, are often associated with wines with a pleasant light structure and good acidity. All these are some of the peculiarities that make the Emilio Sciacca Etna Wine labels valuable products in the Etna wine scene.