Biogeography and climate
biogeography​
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The biogeographic regions show the extension of the areas with common climatic, orographic and geobotanical characteristics. The Miño basin is framed in the following regions:
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Eurosiberian(or Atlantic depending on theHabitats Directive): hilly, montane and subalpine floors
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Mediterranean: oromediterranean, supramediterranean and mesomediterranean floors
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ThePhytogeography makes a description of the potential (not current) vegetation of a region. Salvador Rivas MartÃnez develops theVegetation Series Map of Spain (1981-1987) based on the revision of the vegetation series by Luis Ceballos (1941).
The most important vegetation series in the Miño basin are:
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18bb – Pyrenean oak groves (Holco mollis-Quercetum pyrenaicae sigmetum). Supra-Mesomediterranean series Western Carpeta, Orensano-Sanabriense and Leonesa humid-hyperhumid Silicicola Pyrenean oak (Quercus pyrenaica). It is located in the Sil basin, towards the eastern mountains of the basin (Masizo Central Ourensano, Montes de León and Bierzo). It occupies 15% of the basin. The mature stage or climax of these series corresponds to dense oak groves, quite shady, creators of brown soils with mull.
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8c- Acidophilic oak forests (Rusco aculeati-Quercetum roboris sigmetum). Galician-Portuguese hill series acidophyll oak (Quercus robur). Middle valley of the Miño, region of O Ribeiro and international basin. It occupies 14% of the basin. Corresponds in its optimal stable to a dense oak grove of oaks (Quercus robur), which can carry a certain amount of melojos (Quercus pyrenaica), hollies (llex aquifolium), chestnut trees (Castanea sativa), laurels (laurus nobilis) and cork oaks (Quercus suber). In the undergrowth of the carballeda, in addition to a good number of sciophilous nemoral herbs there is a more or less dense shrubby undergrowth in which Mediterranean elements are usually found, coexisting with other Euro-Siberian deciduous plants or those from a wider area . The area of this series seems to coincide quite well with the hilly floor of the Galician-Portuguese sector.
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8d – Acidophilic oak forests (Vaccinio myrtilli-Quercetum roboris sigmetum). Galician-Portuguese montane series oak acidophilus (Quercus robur). It is distributed especially by the Lugo plateau. It occupies 30% of the basin. Its stable optimum or climax to a dense oak forest that is home to plenty of perennial shrubs and herbs. They grow on base-poor siliceous substrates, generally on deep soils.​
Climate
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Climate classification (J. Papadakis):
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High Minho:​ in this zone of the basin a climate prevailsfresh maritime mediterranean, but also cool temperate Mediterranean (Terra Chá) and temperate Mediterranean.
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Sil: one climate prevailscool temperate mediterranean. In the Cantabrian zone (region of Laziana) there is a humid Patagonian-type climate, as in the Massif Central of Ourense (both zones also have a cold temperate climate. A Mediterranean-type climate predominates in Leonese Bierzo tempered.
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Minho Low: a climate type prevailsTemperate Mediterranean. Towards the mouth it progressively presents climates of the continental Mediterranean type, maritime Mediterranean and, finally, on the coast, warm maritime.
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temperatures
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Annual average: The mean in the basin is11ºC. Regarding the average annual temperature values, the minimum (4 ºC) are reached in the mountainous area of Sanabria and the Sierra de la Cabrera (SE of the basin). In general, the eastern mountainous zone (Masizo Central Ourense, Montes de Sanabria, Montes de León and in the region of Laciana (Cantabrian Mountains)) oscillates mean annual values of 7ºC. In the Miño Bajo area, from the Ourense basin to the mouth of the Atlantic Ocean, the mean annual values range between 14ºC, being the highest in the basin.
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Mean of the maximums of the warmest month: The mean of the basin is26ºC. The maximum values (28-32 ºC) are located in the Miño valley from Ourense to Monção, in the Monforte de Lemos and Ponferrada basins. The minimum (< 20 ºC) are located in the mountains of Sanabria and Sierra de la Cabrera.
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Average of the minimums of the coldest month: The mean of the basin is1ºC. The minimum values are located in the eastern mountain ranges (-4 to -2 ºC, reaching -6 ºC at some point). The maximum values for this parameter are reached on the Atlantic coast (4-6 ºC).
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Rainfall (P):The average annual rainfall in the basin ranges between1000-1400mm. The lowest values occur, especially, in the Ponferrada basin, oscillating between 600 and 800 mm per year. The maximum values (1600-2500 mm) occur in the Massif Central of Ourense, in the northern part of the Bierzo region, in the O Courel mountains and in the Condado region.
- Humidity regime (J. Papadakis): almost the entire basin is in a humidity regime characterized asME - Humid Mediterranean, but the areas of the Atlantic coast of A Guarda, the Ourense Central Massif, the Sierra de Os Ancares, the comarca Leonesa de Laciana (Cantabrian Mountains) and the sierra da Cova da Serpe (in the North) are found in a regimeHu - Wet.
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Annual mean evapotranspiration - ETP (Thornthwaite): the mean of the basin oscillates around the 650mm, being greater (700-800 mm) in the coastal zone and in the basins of Ourense, Monforte and Ponferrada. The minimum values (500-600 mm) are located in the area of the Ourense Central Massif, in the mountains of Sanabria, in the Montes de León and in the area of the Cordillera Cantábrica.
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Aridity index (P/ETP): this index indicates the scarcity of water or moisture in the air or on the ground. In the entire basin, the index is greater than 0.75.
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R-Factor (Wischmeier and Smith Rain Erosivity Index (USLE)): The highest values (400-600) occur in the upper part of the Tea river and in the SuÃdo and Faro de Avión mountain ranges, extending northwards, reaching the Ulla river. High values (300-400) also occur in the Massif Central of Ourense and in the Sierra do Courel, as well as in the Louro river valley and in the Condado region and the Portuguese Alto Minho. In the Miño Alto area and in the Sil basin, the minimum values of the basin generally occur, between 100-200.
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Sources:
