Regional Park of the Middle Course of the river Guadarrama and its surroundings

The surface of the Regional Park is classified according to its degree of protection in three zones:

1. Maximum protection zones: are the most interesting and ecological value. The objective is to conserve natural and cultural resources and the maintenance of ecological processes to prevent their degradation. It includes:

• Groves and plains of the Guadarrama and Aulencia rivers.
• Encinares of the ramp of the saw.
• Holm oaks over the detrital countryside.
• Mixed masses of oaks and pines on the detrital countryside.

2. Protection and improvement zones: They correspond to the land that has undergone a profound transformation due to the traditional processes of agricultural and forestry use. In these areas, the conservation and recovery of the ecosystem is essential. Are included:

• Mixed masses of oak and pine on the Rampa de la Sierra.
• Replacement stages of holm oak on the Rampa serrana
• Stages of substitution of holm oak on the detrital countryside.

3. Activity maintenance areas: They are characterized by their agricultural activity, which is mainly focused on rainfed crops. It also includes land with repopulation of pines. Are included:

• Repopulation pine forests on the detrital countryside.
• Rainfed crops on the detrital countryside.

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The Geology of the Park can be roughly broken down into three large units:

• Mountainous area comprised by the Sierra de Guadarrama,
• Transition zone known as Rampa de la Sierra,
• Sunken area called Cuenca del Tajo.

Image Source: Geological Map E: 1: 50.000 from the IGME MAGNA Series

In this geological section the three units are observed. The formation of these units is related to the presence of a large fracture known as the South Fault.

The Sierra de Guadarrama is located between the provinces of Madrid, Segovia and Ávila. It is formed by a chain of mountains with a northeast-southwest orientation and is about 80 kilometers long.

It is part of a larger mountainous unit such as the Central System. This, in turn, divides the Central Iberian Plateau into two sub-plateaus, constituting a limit for the hydrographic basins of the Tagus and Duero rivers.

The geomorphology of this natural space is conditioned by the geological units previously described. Thus, from the fault to the north, the landscape of granite boulders predominates, while to the south the forms and deposits originating from fluvial currents on sedimentary materials dominate, that is, mainly gullies, ravines, terraces and plains.

Origin and geological evolution

Primary Era (Paleozoic): The Hercynian Orogeny takes place. The collision of two large continental masses generates an extensive mountain range known as the Hercynian Massif. The first rocks that will form the Sierra de Guadarrama date from this context. We refer mainly to granites and gneisses.

High School (Mesozoic): The huge mountain range suffers strong erosion processes, being devastated. This, added to the continuous rise and fall of the ocean water level, causes the dominant rocks in this period to be sedimentary (mainly limestone, marl and sandstone).

Tertiary era (Cenozoic): A new Orogeny called Alpine occurs. The clash of Africa with the Iberian Peninsula "wrinkles" the continental crust forming the Central System, thus giving rise to the Sierra de Guadarrama. The subsequent fragmentation into blocks of the Sierra, the birth of the current hydrographic network and erosion, begin to configure the mountain landscapes and their surroundings.

Quaternary era: A glaciation is established in the Northern Hemisphere. At present there are still traces of the glaciers in the Sierra de Guadarrama.

8.000 years ago, the last interglacial period was established, temperatures rose and the ice retreated to the polar ice caps. This melting helped to consolidate the network of rivers in the Sierra de Guadarrama. The force of the water generated valleys and terraces, giving rise to the current morphology of the landscape.

The Guadarrama river rises in the Madrid mountain range of the same name, collecting the waters that flow down from Puerto de la Fuenfría, Cerro Ventoso and Siete Picos, through the La Vega and Navalmedio streams.

From its source until it flows into the Tagus River, already in the province of Toledo, the river follows a long journey from north to south. Its main tributary is the Aulencia.

In its course there are three well-differentiated sections:

• The high or mountain section: It is characterized by the strong unevenness that its waters save. It has a strong erosive power that manifests itself in the narrow valleys that it models.
• the middle section: It runs along the foot of the mountain, presenting a smaller unevenness, which causes a lower speed of its waters and therefore a lower erosive power.
• the lower leg: Crosses the sedimentary plain. As the slope is low, the river flows slowly, producing sedimentation of the eroded materials in the upper reaches.

The existing climatology for the Regional Park area is within general climatic conditions typical of the continental mediterranean climate. The main climatic parameters of interest for the area are:

- Average annual temperatures around 12 - 14 ºC.
- Average annual rainfall that ranges between 637 mm in the northern zone and 420 mm in the central-southern zones.
- Prevailing winds from the southwest.

The main types of soil present in the Regional Park are:

a) MINERAL SOILS CONDITIONED BY THE TOPOGRAPHY: they are located on the slopes or slopes of mountains and valleys, and undergo rejuvenation processes and/or limited evolution. In this case, we find:

• Dystric Regosols: very abundant soil in the Regional Park. They originate from the denudation of the Sierra and subsequent deposition in the Rampa and the fields during the Miocene and are the original material from which the soils are formed, they are loose, unconsolidated and with a coarse texture. The vocation of these soils is fundamentally agricultural or forestry.

• Umbrian Leptosols: soils located in the northern part of the Regional Park. They present coarse textures typical of the starting material and are associated with other types of soils such as: lithic leptosols or cambisols. The vocation of these soils is clearly forestry and they present a high fragility against erosive phenomena due to their sloping disposition.

• Eutric Fluvisols: poorly evolved soils from alluvial materials. These soils are distributed at the bottom of the valley through which the river flows and on its fluvial terraces, they have a clear agronomic vocation and are the sustenance for the remains of gallery forests with high environmental value in the territory. These soils are associated with others as you ascend to the successive terraces of the river slopes.

b) MINERAL SOILS CONDITIONED BY THE TIME OF EVOLUTION: They are fundamentally minerals but they present a higher degree of evolution than the previous ones.

• Eutric Cambisols: they are the characteristic soils of the countryside, preferably of the forests that still remain in the Regional Park and are well represented throughout the territory. The starting material is the arkose from Madrid and they have a clear cereal and/or forestry vocation.

c) MINERAL SOILS CONDITIONED BY THE CLIMATOLOGY: they present an argic horizon, horizon of enrichment in clay fraction. Two types of units are distinguished:

• Luvisols: of two types, the gleycs that present hydromorphic problems (reduction of iron oxides due to the anaerobic atmosphere of the soil) and are associated with fluvisols in the river; and the haplic Luvisols that are located in flat areas of the countryside, associated with Cambisols and Regosols. The vocation of these soils is clearly agricultural, having been used since ancient times by man.

• Haplic Alisols: located in the northern area of ​​the Regional Park, associated with Cambisols. The vocation of this unit is forestry, being the support for the best oak patches that are preserved in the territory.

The Regional Park is made up of three dominant landscapes of great diversity and ecological value: the Mediterranean forest, the riparian forest and the crops and wastelands.

El Mediterranean forest It is basically made up of holm oaks in their different stages of succession, accompanied in most cases by stone pine, the product of old reforestation, which sometimes forms monospecific masses. Holm oaks appear above all in the North zone, in the Rampa de la Sierra, where the relief is more abrupt, granitic materials dominate and the soils are of poorer quality, although they are not exclusive to the North, but can also be observed in areas of the South where the relief is smoother and the materials are detrital.

As we move towards the South of the Park, there is a tendency to increase the crops, represented mainly by the cereal. It can be said that in the center and south of the Park there is a codominance between crops and areas with more or less natural vegetation, the former linked to the flatter areas, while the rest appear in ravines, streams, more inaccessible areas. , etc. In this last period, numerous areas of cultivation have been abandoned, which is why even more areas of wasteland to pasture with scrub.

Cereal is the crop par excellence in the Regional Park, in which different shades and color contrasts can be seen from the rest of the wooded and/or cultivated surfaces. The spatial distribution of the cultivation plots in the territory gives it a heterogeneous aspect.

The axis that constitutes the riparian vegetation, associated with the main watercourses, gives the landscape its own character. The trees associated with the riverbeds sometimes constitute a visual barrier that prevents the two banks from being visually connected.

The urban surface, although absent from the Regional Park area, constitutes a clear conditioner of the landscape of this territory.

DETERMINATION OF LANDSCAPE UNITS

If we delve a little deeper into the three dominant landscapes of the Park that we have just seen, we can establish 9 subgroups of landscape units, closely linked to the type of geomorphology, vegetation and land use they present. These subgroups correspond, broadly speaking, to the following territories:

• Mixed masses of oak and pine on the ramp of the mountain range.
• Encinares or their first stages of substitution on the ramp of the saw.
• Mixed masses of oak and pine on the detrital countryside.
• Encinares or their first stages of substitution on the detrital countryside.
• Pine forests on the detrital countryside.
• Rainfed crops on the detrital countryside.
• Mosaic of crops and brooms on the detrital countryside.
• Riverbanks and associated vegetation.
• Others (scrapping, gravel pits, landfills, etc.).