North Alentejo, The Landscapes
|The North Alentejo is an area characterised by an enormous diversity of nature and of landscape, a result, basically, of the many physical, biological and cultural influences that are integrated here.|
On the one hand, there the characteristics of the Alentejan plain, with wide open horizons, shaped by the extensive exploitation of the soil, and, on the other hand, landscapes that are more typical of the north, mountainous and cold.
Among a varied mosaic of wheat-fields, cork-oak woodlands, holm-oak, chestnut and olive groves, pinewoods, eucalyptus plantations, vineyards, market gardens and orchards, coppices and thickets, riverside spinneys, water courses and reservoirs, the majestic Serra de Sao Mamede rises aloft, with its imposing and robust quartzite ridges, the fulcral and determining element of the whole of the natljral and cultural environment of North Alentejo.
The Serra de Sao Mamede, the central feature of the Natural Park with the same name, has a wide variety of landscapes, resulting from an almost always harmonious cooperation between Humankind and Nature. Amidst the typically upland natural landscape, characterised by a wild, bare, rocky surroundings, there is a proliferation of different kinds of biotopes and habitats.
Here is found the southern-most distribution of many Atlantic plant species and communities. It is the most important and most complex range of hills south of the Tagus (Tejo). At its highest it is 1,025m, it stretches in a NW-SE direction for about 40 kilometres from Castelo de Vide in the north, and is a little more than 10 kilometres wide.
It is granitic in the south-west, which extends from Portalegre and Fortios, through Ribeira de Nisa and Carreiras, to the ridge situated to the south of Castelo de Vide. But the greater part is made up of schists, greywacke (a dark sandstone), limestone and quartzites, a lithology reflected in the variety of the soils found here.
Serra de Sao Mamede presents one of the rare outcrops of Devonian rock systems that exist in Portugal. This stratigraphic layer, dating from between 450 and 350 million years ago, is to be found, together with other rocks, in the dolomitic limestone which extends throughout the valley between Escusa and Porto de Espada.
Associated with these limestones and their exploitation are the former Escusa lime ovens which were, at the beginning of the 20th century, the most important industry in the region. In the Escusa quarry, in some of the larger fissures, can be seen typical limestone formations -stalactites and stalagmites.
A geological accident worth mentioning is the Castelo de Vide fault, the most important alpine tectonic fault in the serra. It consists of a fracture in the quartzite crest of the senhora da Penha ridge, a left-handed disconnection which spurns the crest itself for about 300 metres.
This fault is accompanied most of the way by a vein of quartz and is above the place where the medicinal mineral springs of Castelo de Vide are situated. A mountainous landscape rising from the plain, the Serra de Sao Mamede has two central plateaux.
Of its wide, wet and fertile valleys, the finest are those of Escusa, Porto de Espada, s. Julicio, Porto Roque and soverete, from which rise the summits of Castelo de Vide (762m), Marvcio (865m), Selada (823m), Portalegre (638m), S. Mamede (1025m) and Fria (900m).
The valleys are corridors for a network of watercourses, tributaries of the hydrographic basins of the Rivers Tagus and Guadiana, which, in their part of the serra, offer well-developed riverside tree-coverings of poplar, willow and ash. Among the walnuts, chestnuts, oaks and olives, the landscape is varied, sometimes geometrically patterned, with small, irrigated fields, meadows, vegetable plots and orchards.
In the Escusa valley, between Castelo de Vide and Marvao, the chestnuts are integrated within a semi-forest system, the souto, similar to the cork-oak plantations. The plantations are in real decline as, little by little, they have given place to the "wild" chestnuts (planted for the production of wooden poles, obtained by polling the trees) or have been substituted by olives.
Also the plantations of Pyrenean oak and the climatic vegetation of the serra are today found only in very restricted areas. The Maritime Pine, introduced in unmixed plantations, today occupies a large area of the surface of the serra, principally at higher altitudes.
The creation of the Natural Park marks, appropriately for the heritage of its nature and its landscape, the beginning of the restoration of the traditional agricultural systems of the serra, in a degraded state at the end of the 19th century because of the campaigns for cereals. Agriculture continues to be the dominant economic activity in the region.
In the most mountainous area, to the north, small and medium-sized properties predominate, with a diversified use, which results in the consequent compar- tmentalisation of the space: groves of oak, chestnut groves and cork-oak plantations, alternating with olive groves, pines and eucalyptus, and dry arable land alternating with small irrigated fields and coppices, at the higher altitudes.
To the south, small and medium-sized properties are substituted by large estates, predominantly concerned with extensive arable agriculture, at times combined with cork-oak and olive groves and with livestock rearing.
The NW-SE alignment of the massif of S. Mamede confers on it very special characteristics from the point of view of natural heritage, particularly in terms of flora. This is due to the hot and dry Mediterranean type of climate on the south-west facing slopes, and cold and wet, clearly Atlantic, on the north-east facing slopes. On the highest hillsides and peaks of the serra are found Atlantic species such as Luzulu lactea, Ferulaga capifolia, Micropyrum patens and Arnoseris minima, for which common names are unknown.
Close to the oak and chestnut groves, it is possible to find peculiar vegetal species, some of which are rare, such as Lamium bifidium, Trisetum scabriusculum, Iberian Gramineae (grasses) and endemic to the Iberian Peninsula, Luzula campestris, Limidorum abortivum (Violet Birds Nest Orchid), Euphorbia nicaeensis (a variety of Spurge) and other quite curious plants such as the locally-named "Erva-pinheira-orvalhada", of the Equisetum species, known for its carnivorous nature.
Some slopes of the serra are still found clothed in undergrowth noticeable among which is Genistela tridenta, a kind of broom (much used for lighting fires and whose flower is used to make medicinal tea for treating the stomach and the liver), Genista triacanthos, also a broom, Narrow-leaved Cistus, Genista tracanthos, a common heather, and Scottish Heather.
On the southward facing slopes, covered to a greater or lesser density with cork-oak and holm-oak, there is noticeably Mediterranean undergrowth where Gum Cistus, Lavender, Rock-roses and Pteridium aquilinium, a kind of fern, predominate. The diversity in the ecological conditions of Serra de S. Mamede also determines the diversity of the fauna present here.
Of particular interest are the Otter, Cabrera's Vole and, in the north of the serra, the stable presence of the Iberian Lynx. Also present are protected species of birds such as Bonelli's Eagle and the Griffon Vulture which share the region with the sparrowhawk, the short-toed Eagle, the Black-shouldered Kite, the Red Kite and Montagu's Harrier.
Among the mammals are the Badger, the Polecat, the Weasel, the Mongoose, the Genet, the Wild Cat, the Fox, the Rabbit and the Wild Boar, whose populations are truly expanding. The limestone caves of the serra, in particular the former mine of Cova da Moura, are home to important colonies of bats.
Situated in the Serra de Sao Mamede, the most important cave in the country, and one of the most important in Europe, serves as shelter to the breeding colony of almost 20,000 schreiber's Bat, a protected species, classified as "vulnerable". This cave is also important as a hibernation cave for other species such as Bechstein's Bat, classified as an "endangered" species, and very rare in Portugal.
The rivers and streams that are most important, as well as having rich fish populations, entertain the presence of numerous amphibians and reptiles, important among which, by being endemic to the Iberian Peninsula, are the Lacerta shreiberi, "Lagarto-de-agua" ("water lizard", which represents here an isolated population), the Alytus cisternasii ("Iberian midwife toad") and the Triturus boscai, Bosca's newt.
As well as the Serra de Sao Mamede, there are other places in North Alentejo whose landscape is dominated by a geology with a physionomy and characteristics close to that of granitic hills, that is, the massif of Santa EulAlia and the region of P6voa e Meadas.
The massif of Santa Eulalia, with its characteristic granitic outcrops, is a geologically important sub-volcanic structure. It has a roughly elliptical shape, running approximately W-E, composed of granite which is seen in two varieties: those of the centre (grey), more recent, and those surrounding (pink). The pink colour of the latter, which in some cases intensifies into a reddish pink, is funda- mentally due to the nature of the minute quantities of feldspar crystals and also those of quartz.
Further north, above the Serra de Sao Mamede, the region of Povoa e Meadas is a granitic area, relatively flat, in which the rocky outcrops form a typical "chaos of blocks", among which stand out some examples of stalk- like boulders such as "Pedra Delicada", the "delicate rock". The chaos of blocks is made up of boulders scattered and dispersed by chance, moulded through time by the action of erosive agents.
The granite, like all of the rocks, gradually becomes degraded through variations in temperature, by water, by wind and by human beings. In the least resistant areas, the rock loses its consistency, forming fissures, fractures, demarcating the parts of the rock most resistant to change, shaping the blocks.
Little by little, these become rounded, and the alteration to the rock is accelerated, due to the great increase in the surface area exposed to the erosive forces and this progressively changes the feldspars and small traces of secondary minerals, the clays, which compose the surrounding soils.
In these areas of poor soil, determined by the rock outcrops, there are meadows and fallow land as well as woods of Pyrenean oak, particularly around the reservoir of P6voa e Medeas. These woodlands are semi-forest systems of oaks (holm- -oak, cork-oak, Pyrenean oak) with an artificial structure rather like a park, influenced by the traditional agricultural multi-use practices of a sylvan-pastoral kind.
These systems are associated particularly with the extensive use of non- -irrigated land (fodder and grain), open pasture (which is the result of crop rotation which these practices demand) and/or pasture improved by clover and legumes. They are, moreover, very open environments compared with other types of woodland, with a distribution of trees that is very often regular and uniform.
In general, the holm-oak woods are less dense than those of the cork-oak, due to the fact that their association with the production of cereals is older and more intense. Also the holm-oaks normally have a top that is lower and wider than the cork-oaks, in that their fundamental purpose is the production of fruit, while the production of cork requires that the cork-oaks have boughs that are higher and straighter.
The origin of the oak-woods appears to be connected to the non-enclosure of holm-oaks and cork-oaks, which went on to assume an increasingly important role in the
systems of production, bringing together sylvan-pastoral and agricultural activities. according to Fragoso Sequeira (1790), "due to nature and to chance" the holm-oak woods had their origin in the Portalegre region, in the middle of the 17th century, "through the protection of woodland, because of the local importance of herds of pigs at that time".
According to the same author, it was also in the region of Portalegre that the cork-oak began to be exploited in the oak-plantation system. Although this use of the cork-oak had begun to some extent in the 17th century, it was only in the 19th century that it enjoyed a great expansion, by virtue of the new markets for corks created in response to the demand for bottling wines of quality, such as champagne.
Until then, cork had only been used on a small scale in the production of. honey and wax and in the manufacture of buoys. Curiously, it is in the north of the Alentejo, particularly Serra de sao Mamede and in the region around, that we today find these "park woodlands". In fact, as already referred to, as well as the cork-oak and holm-oak woodlands, it is still possible in this region to find an interesting combination of chestnut woods, although only in small areas located to the north of the Serra (Nisa, P6voa and Meadas) and in the part of the Serra exposed to the NE -the groves of sweet chestnuts and "wild" chestnuts -and two unsung forms of woodland used particularly for agro-pastoral purposes: the Pyrenean oak wood and the mixed Pyrenean and cork-oak wood. As a magnificent example of the latter, the one that has developed on granitic soil between Tolosa and Arez is outstanding.
A little further north, between Nisa and sao Sjmao, we can see a mosaic that is representative of the Alentejan landscape. A predominantly schist soil presents a varied cover, composed of characteristically steppe-type land (grasslands), areas of shrub and thicket (cistus and olive), and woodlands of cork-oak and holm-oak.
Also, between Castelo de Vide and Alpalhao, the landscape is open, shrubby scrubland, with holm-oaks, cork oaks and Pyrenean oaks dotted among a matrix of meadows, non-irrigated arable land, wheat-Iands and small blankets of broom, where species of birds of the open plain, such as the Little Bustard, are commonly found. Further south, in the Arronches-Monforte-Campo Major triangle, the finest examples of holm-oak woodland in the country are found.
With luxuriant trees and extensive woods, and structurally heterogeneous in terms of undergrowth, they are an excellent example of different types of traditional use. Part of this extensive area corresponds to the Site of the Nature 2000 Network of Campo Major. This site, as well as the well-preserved holm- -oak woodlands, with year-long pasture and certain typical perennial plants, also contains important habitats for annual herbaceous rushes.
The presence of the Caia reservoir supports this range of habitats and ensures the existence of a relatively important well-watered perimeter, with the cultivation of rice and tomatoes being specially distinguished. But the dominant landscape is that offered by the non-irrigated/irrigated corn and olives.
The bird community to which these grasslands offer habitat is fairly simple, with little diversity, but very well conserved because of species protection. Noteworthy is the presence in the region of a population of the threatened and emblematic Great Bustard, the biggest bird in the continent of Europe, as well as other important species such as Montagu's Harrier, the Little Bustard and the Grouse. Between Arronches and Mosteiros, the extensive holm-oak woodlands present a fairly heterogeneous cover, with areas of cereal, arable- -pasture land and a dense covering of cistus.
The holm-oak woods between Arronches and S. Eulalia, comparatively earlier, are more open, with the trees spread out in regular, uniform patterns (like a "park"). These are the different forms that the oak woodlands can present - resulting from the involvement of different factors (the level of human intervention, the density of the trees, the nature of the soil, among others) -which make this an important reservoir of biological diversity.
And, associated with these woodlands, there is found a typical bird-Iife, the most important of which are the Nuthatch, the Orphean Warbler, the Spotless Starling, the Woodlark and the Buzzard. In the extreme south-west of North Alentejo, in an area which extends principally through the Council areas of Avis, Ponte de Sor, and a small part of Alter do Chao, there are cork-oak woods situated on sandy soils of the Miocene period, which are relics of our natural heritage.
A significant part of this area is included in the Site of Cabecao, integrated in the Nature Network 2000. At times, the cork- -oak woodland is mixed with holm-oak, or is even dominated by it. There are also certain areas where it is mixed with the quercus faginea, Portuguese oak. As well as their economic relevance, the cork-oak woods are of great ecological importance, especially in maintaining a high biological diversity and in conserving a cultural heritage associated with these agro-ecosystems, profoundly adapted to the unfavourable Mediterranean climate conditions, where poor soils predominate.
They have a rich bird-Iife, particularly for the population of birds of prey, exceptional for its richness and the density of individual species. Birds of prey that are common are the Black Kite and the Red Kite, the Booted Eagle, the Short-toed Eagle, and the Goshawk, among other species. In this same extreme south west, near to Maranhao (Avis Council area), the Valley of the River Sede offers us one of the most beautiful agrarian landscapes of the whole of North Alentejo.
This long valley, surrounded on both sides by mixed woodlands, cistus and small areas of stone pine and eucalyptus, with some large trees among them, is a multi-coloured melange of cultivated plots, geometrically patterned, only interrupted by a tongue of water and its tree-Iined banks.
The whole of the valley is under intense agricultural exploitation, in which olives and the cultivation of irrigated crops such as tomatoes, corn and sorghum predominate. The scrub-Iands are natural or semi-natural communities which give rise to a type of landscape in which the dominant element is the presence of shrubs with, at times, some scattered trees or copses.
Shrub species are dominant. In North Alentejo there is a varied combination -Quercu$ coccifero, Kermes oak (limestone), plantations of broom and gorse (both characteristic of granitic soils) and Gum Cistus -and, as well as their ecological importance, they make a valuable contribution to the already vast range of colour in the landscape of the region.
Reference has already been made to the scrub-Iands which clothe some of the slopes of the Serra de sao Mamede, in general dominated by heathers, together with Narrow-leaved Cistus, with Genistela tridentata, and with Genista triacanthus. However, whenever accidental causes or the persistent action of man have led to the disappearance of the tree cover, in general it is the Gum Cistus that has taken over the new spaces, forming, as can be observed in some areas of the Serra de sao Mamede, i both dense and scanty growth (monospecific thickets).
In North Alentejo, as in the Alentejo in general, chalky soils are not very much represented and, for this reason, the areas of Quercus coccifera assume great importance for the ecology and for the landscape when they are present. Here we would point to those of Vaiamonte (Monforte) and Sousel for their density and size. The slopes of some of the rivers and streams of North Alentejo present dense communities of shrubs with a high level of diversity in the flora as, for example, in certain parts of the Nisa and Seda rivers.
Downstream from the Povoa e Meadas reservoir, the Nisa is surrounded by groves of Pyrenean oak with a varied and fairly dense population of shrubs (including infestations of Acacias), where the presence of species such as Ruscus aculeatus, Butcher's Broom, are indicators of a state of evolution directed towards a potential vegetal cover. These areas of shrubland are Jrefuge for larger-sized fauna.
It is easy, here, to see traces of wild boar and of deer. Also, downstream of the dam of the reservoir at Maranhao, the Seda flows through a very enclosed valley, with rock slopes and steep escarpments. These slopes, and the nature of the substratum, limit human activity and, consequently, the plant cover.
These scrublands are predominantly an area of fairly poor substratum, with rocky outcrops and thin schist soils, and with little diversity in the composition of its flora, which is mainly cistus, lavender and gorse. However, in places where the soil is deeper, there is a more diverse shrub population, as is indicated by the presence of species such as Myrtle, the Strawberry Tree and Phyl/rea angustifalia, among others.
The humid zones of North Alentejo correspond to the water courses which are distributed by the hydrographic basins of the Tagus and the Guadiana, and the bodies of water such as reservoirs created and maintained by man for agriculture, for herds and flocks, to supply local populations and for recreation. The most important tributaries of the River Guadiana are the Xevora, the Caia, the Abrilongo and the soverete.
They are river systems of a markedly torrential nature, suffering an accentuated fall in water or even a complete interruption in their flow during the summer. The Abrilongo, which functions as the border with Spain for a great part of its length, has tree-Iined banks, sometimes densely so, with highly diverse flora, and with trees of taller stature such as ash, poplar, willow and alder forming the tree cover.
The undergrowth of shrubs is made up of brambles, Honeysuckle, wild roses, among other climbers and shrubs. Next to the river, in the less dense sections of undergrowth, grow Tamarisk, Oleander, Blackthorn and Hawthorn. Among this riverside vegetation lives a bird population that is diverse and characteristic, such being the case with the Wren, the sardinian Warbler, and the Golden Oriole.
Close to the river, between the vegetation and the water line, the Rufous Bush-Chat is fairly common. After the junction with the River Xevora, the riverside vegetation becomes less dense and is essentially composed of Oleander, Willow, Buckthorn and Poplar. In the sections where the sides of the river are formed by banks of earth, they are favoured by Bee-Eaters, Sand Martens and Kingfishers, installed here in their nests after excavating deep burrows.
The River Caia is one of the most important water courses for the conservation of the Anaecypris hispanica and the Chandrostoma lemmingii, the straight-mouthed Nase, fish species endemic to the Iberian Peniflsula with a distribution restricted to the Guadiana basin and classified "endangered" and "rare" respectively.
There also co-exist in it the only two species of Portuguese fresh-water turtle: the "common" and the "striped". On the Caia is the Caia reservoir, the most important store of water in the whole of the south-western part of North Alentejo, used not only for irrigation but also fort the provision of water to local populations. It has great biological importance since it attracts a large and diverse aquatic bird-life in the winter, where the Mallard, the Garwall, the Red-Crested Pochard, the Wigeon, the Shoveler, the Teal, the Coot and the Great Crested Grebe are noticeable among others. A
s well as these species of winter-visitor aquatic birds, and also the herons and egrets (the Cattle Egret, the Purple Heron, the Grey Heron), in the Caia reservoir, other aquatic birds can be seen, such as species of limicoles, Spoonbills, Cormorants and terns. The vegetation on the banks as well as on the "islets" formed by rocky outcrops are important places for nesting, refuge and rest. With their origin in the north-eastern Alentejo (Serra de Sao Mamede and the surrounding region) the principal tributary systems of the River Tagus are the Sever, the Nisa, the Sor and the Seda.
They are water courses that flow for almost the whole year, and on them, with the exception of the Sever, have been constructed important reservoirs: that of P6voa e Meadas (Nisa), Maranhao (Seda) and Montargil (Sor).
The River Sever, throughout its length as far as the Tagus, presents a number of places that are both rough and pleasant, resulting from the coarseness of granite in conjunction with the leafy and restful river-bank tree cover, with poplars and ash. The river has a fish population some of which is made up by the endemic Cyprinidae. The Otter is also fairly common, as in all of the rivers and reservoirs of North Alentejo.
Of all of the birds associated with this river, the Dipper assumes particular importance by being a protected species. Here several species of amphibians and reptiles characteristic of the North and Centre of the country are fairly common, and have the southern limit of their distribution in the Serra de Sao Mamede, as is the case with the Rana iberica, the Iberian frog, and the Lacerta schreiberi. The hydrographic basin of the River Nisa represents a high level of surface drainage (bed-rock impermeable and soils with little permeability) and, for this reason, is subject to little flooding. Below the P6voa e Meadas reservoir, the river landscape changes as the river flows through a deep, steep-sided, meandering valley, as is typical in areas of schist topography.
Close to the dam wall there is a waterfall, where the water discharged from the dam experiences a considerable drop. Further south, the River Seda fills the Maranhao reservoir and, below this, gives rise to a flat valley which we have already referred to. Despite the intense agriculture, the tree cover along the line of the river is in a good state of conservation, with willows and poplars clearly obvious.
Although there is a serious threat presented by the profusion of exotic species, the Seda protects a fish population of nigh conservation value, represented by Boce, Roach (Rutilus 7Iburnoides), Barbel, Nase (Chondostoma lemmingi), and Loach :Cobitis maroccana).
The Maranhao reservoir is found where the Seda is very enclosed, which allows hydro-electric exploitation, although only of secondary importance. It is fed by the Raia and Avis rivers, as well as by the River Seda. The resulting river curves to the north and, close to Cabecao, joins the Sor to form the River Sorraia.
Finally, a reference to the River Tagus. With its source in the Sierra de Albarracin (Spain), after flowing for nearly 1 ,000 km, it connects the Alentejo with Beira, by way of deep valleys and schist escarpments, which comprise the last refuge of the Black Stork -, and with Ribatejo, here by way of gentle and fertile plains. But in Gaviao, land of the lamprey, it visits the Alentejo, offering us a fascinating river landscape.
Courtesy of Tourism Region of Sao Mamede