Montado ecosystem.

The Montado is an agrosilvopastoral system explored at several levels – trees, bushes and herbs – according to the potential of each region.On the tree level it can be made up of oaks like cork oak (Quercus suber), holm oak (Q. rotundifolia) and less frequently pyrene oak (Q. pyrenaica) and portuguese oak (Q. faginea), in pure or mixed populations with variable densities. The ground cover is occupied by pastures used by cattle or is used for dry land crops on a rotation system. The natural pastures can be occupied by shrubs, in variable proportions.Humans are an integral and fundamental part of this ecosystem. It was through our clearing action that the montados were created, ever since we started intervening on our natural surroundings. Human management is necessary, in a more or less intensive way, in order to maintain the montado. Without this intervention, the system evolves, naturally to form a dense forest, where people have more difficulty obtaining resources.The way this process of transformation of the Mediterranean forest developed influenced the structure of the system as it presents today. Some older practices still persist, now without context, making more difficult the adaptation of the system to the new ways of agrarian production. Other ways emerged, some well adapted to the system, other causing more or less serious disturbances.The montado is a system for using the soil developed on a physical background that involves climate, pedological and geomorphological factors with specific characteristics. It is why this ecosystem is restricted to such a limited area, when compared to other ecosystems in our planet.

At Mediterranean latitudes, (30º-40º) the effect of the moist winds coming from the west (the sea), during the winter, soothing the continental cold, alternates with the dry and hot winds of summer, associated with subtropical high pressures. During winter, the Mediterranean basin is also subject to winds coming from the North Atlantic. These cold and moist masses of air warm up when in contact with the Mediterranean Sea, forming low pressures. These, then, result in short periods of intense rainfall, causing easy erosion of the soil. During summer the Azores High moves north, while hot and dry winds move up from the Sahara seaside (Sirocco wind).As for the geomorphological aspects, the montados occupy preferably flat lands or softly rolling hills. They can occupy more steep areas, but in that situation the risk of erosion of the soil is high, being recommended it stays covered with bushes, in a more natural structure.Several abiotic factors act differently to create a large diversity of variants in the system. The inclines and running of nutrients to lower areas, the various levels of sun exposure, the various types and depths of soils, as well as the various densities of arboreal cover, combine with different interventions of humans over time, level of pressure of grazing, cycles of rupture and pressure of usage, to create an extreme diversity in the patterns of the montado. From this diversity results a mosaic of structurally and ecologically interdependent systems.

The physical background represents the potential resources available to be transformed by the biological components of the system. First vegetation, then herbivores, then carnivores and finally humans, who take advantage of all of them and try to maximize the resources, in a sustainable way. When it comes to climate, the montado is embedded in the Mediterranean region that offers these particular conditions: hot dry summers that last at least three months, and winters that are, on the other hand, moist and tempered or cold. Rainfall presents a wide range withing the same year, and over the years, varying between 300 and 800 mm annually and more focused in some seasons than other (especially winter and spring). The values for rainfall and the timing of its occurrence influence, in a very significant way, the composition and quantity of the pastures and the availability of food for cattle.