Ecology

Characteristics

This kind of ecosystem is one of the most representative ones of the Iberian Peninsula and it is completely associated with the Mediterranean climate regions. In these regions, the climate is notable for its marked seasonality: dry and hot summers, cold winters and humid and warm autumns and springs. These climatic factors along with geological and pedological factors provoke the development of a determinate type of vegetation, known as “xerophyte”, whose main characteristic is its adaptation to a climate where the heat and droughts of summer mark a group of morpho-physiological adaptations. Because of the forest uses and the uses that over the time the man has given to the Mediterranean mountains, in this and even when it currently is far from its natural potential, it’s still possible to see a mosaic of vegetal communities, more or less changed by the humans, that still allows our animal and vegetal diversity. We can find the best conserved areas where the orography, the low population density or the soils’ poverty haven’t benefited the human activity.

In these type of plant formations, and although the structure of this kind of forest is based on three layers of vegetation, formed by communities of arboreal and bushy species of sclerophyllous and persistent leaves, of great resistance to the prolonged droughts, and herbaceous species that form the lower vegetation layer. Among the three typical arboreal species we can find the Holm oak (Quercus ilex sub. ballota), the Cork tree (Quercus suber), the Muricated oak (Quercus faginea), the wild-olive tree (Olea europea var. sylvestris) and the carob tree (Ceratonia siliqua). As main species of bushy species we can find the mastic tree (Pistacea lentiscus), laburnum (Phyllirea angustifolia), arbutus (Arbutus unedo), myrtle (Myrtus communis), species of rockrose (Cistus sp.) etc. The species that belong to the herbaceous type are those who have annual character (therophytes).

Plant communities appear inside of this type of forest and they are connected to the presence of water and they appear along the riverbanks. This is what we know as “gallery forest” and it’s formed by different deciduous species like the poplar (Populus sp.), the ash tree (Fraxinus sp.), tamarisk (Tamarix sp.), and bushes like the sarsaparilla (Smilax aspera), the bramble (Rubus ulmifolius), the honeysuckle (Lonicera implexa), and the ivy (Hedera helix), among others.

The Mediterranean forest is one of the ecosystems that present a greater faunal diversity with a wide representation of reptiles, birds, mammals, amphibians and invertebrates. Just to name a few we emphasize the Imperial Eagle (Aquila adalberti), the Shod eagle (Hieraaetus pennatus), the Black Vulture (Aegypius monachus), the deer (Cervus elaphus), the Wild Boar (Sus scrofa), the lynx (Lynx pardinus), the ichneumon (Herpestes ichneumon), the fox (Vulpes vulpes), the badger (Meles meles), the ocellated lizard (Lacerta lepida), the genet (Genetta genetta), the rabbit (Oryctolagus cuniculus), and the linnet (Sylvia sp.), among others.

Species as the lynx and the Imperial eagle are endemic to the Iberian Peninsula and are completely connected to the existence of this type of forest. The degradation of this kind of habitats has been, along with the diminution of the rabbits’ population, one of the main reasons why these species have suffered an important decline.

Antecedents of the Mediterranean forest

The current landscape in the Iberian Mediterranean environment is the result of the evolution of a group of events of diverse nature that have originated changes of continuous evolution in the forests’ composition. In other words, the Mediterranean mount has not always been here, this way by pollen records, etc we know that in the Iberian Peninsula 3-5 million years ago the forest formations were dominated by subtropical taxa and that 3’2-2’3 million years ago a series of climatic changes takes place and retract this formations and allow the apparition of conifers, like Pinus or Cedrus along with other typical Mediterranean as Oleas, Pistaceas and Quercus. Subsequently, glaciations from Europe, up to twenty, cause an alternation of different thickness forests mixed with steppe formations, dominated by Pines and Oaks for times. The last glaciation, 20000 years ago approximately, is the main responsible of the current floristic structure in our country: deciduous forests with predominance of the Atlantic climate in the North and the Mediterranean forest that constitutes the forestall climax (around the 75% of the Peninsula) dominated by the Mediterranean climate (with the structure and species described previously).

The landscape modelling in the Peninsula has joined as a decisive factor in recent times, the human (the man). Undoubtedly, the man’s relationship with his environment has not always been to the detriment of this one. In the Palaeolithic period, small familiar clans of gatherers-hunters should have a nomad character to feed themselves. These groups had to interact with the environment without producing important environmental changes. In the Holocene, from the Neolithic, the population became sedentary, first in small towns, promoting the labour’s division (agriculture, livestock farming, mining industry, etc) every time with a bigger capacity of pressure over the environment. The Industrial revolution represented a qualitative leap in the environment’s capacity of modelling, due in part to the spectacular increase of the population. At this time in the Iberian Peninsula, it’s estimated that 64% of the country could be forestall area, higher percentage than the current one. In 1859, it has been estimated that of those 32 million hectares, between 5 and 7 of them had been alienated by the General Alienation Law and posterior modifications. This ownership change provoked by the liberal policy of that moment, caused the breaking-up of bushes, cork oaks, holm oaks, etc. to sell wood and firewood to the growing industrial demand of raw materials (mining, foundries, railways, etc.) Many of these lands, which went onto private hands, increased in an important way the agricultural production of vineyards, olive trees and legumes. An example of a practise used by then and which came till the end of the last century: it was usual in some livestock farming zones to burn the mount every 3-5 years, whose objective was to obtain more nutritious pastures. The continued fires eliminated the bushes even going so far as to make the oak wood disappear. Even today we can observe extensive patches of thickets that remind us that time. Another more recent example of mismanagement over the forested area happens between 1946 and 1974, when approximately 600.000 Mediterranean forestal hectares were sown by fast-growing species like pine or eucalyptus. In the hills of Andújar, Cardeña and Montoro the thin fertile layer was dropped or terraced to sow these species. Later, the wooded zones growth demonstrated the inefficiency of the timber policy. A high percentage of the Iberian lynx’s habitat was changed in the occupied areas by this species. Currently, it’s estimated that between 15-20% of the pine forest in Cardeña-Montoro and Andújar is occupied by the Iberian lynx. This deterioration of the habitat coincided with the arrival of the myxomatosis, disease which decimated the rabbit’s populations, main food of the Iberian lynx, in a 95%. Later the RHD (rabbit haemorrhagic disease) would come.

The disagreements between owners, community policies, conservationists and citizens who claim an increasing public use, should be minimized to every pretension of ecological niche construction of the different parts by the Mediterranean mount, encourage and support the economical profitability with the ecological diversity and a long-term sustainable management over the economical crises. It would be a question of avoiding in the future new and deep transformations in large patches of the Mediterranean forest and its structure. This is something that since the agricultural revolution in the 1960’s has been simplified.

Climate and strategies of the Mediterranean forest

The climate is one of the main factors that limit the reception and food availability in the Mediterranean area. The growth of plants in the Mediterranean forest is slow because of shortage and irregularity of rainfall. The warm summers and humid winters, at first beneficial for the plants growth, nevertheless prevent it, because of the dryness of the summer and the cold of the winter. This way, in summer the sclerophyllous vegetation (hard, small, leathery leaves) adopt some strategies that try to avoid the water stress, like the production of volatile oils, waxes, hair, invagination or closing of the stomata, development of a radicle pivoting system that delves deeply into the ground, etc. These strategies slow down the photosynthesis processes and their relationship with the growth of the plants. In general, it will never be possible to think about high productions of wood but it’ll be possible to think about high productions of firewood to produce coal. After the summer, the late rains arrival some years, joined to the temperatures decrease, provokes that the pastures production, so long-for as necessary for the herbivores, to be rachitic, finding its bigger production in the spring’s beginning. Early or late frosts can also damage the fructification or flowering of the plants, joined to the irregularity on the abundance of food. The climate can condition important factors as the creation of the soil. The leaves of the Mediterranean vegetation are, generally hard and with thick ribs and cellular walls slow down together with the rains scarcity the physical aggressions that facilitate the paedogenesis’ processes. An important adaptation of the Mediterranean forest, considering the high probability of fires in the summer, consists in the re-growth capacity of a wide variety of plants after them. The cinders, rich in phosphorus, potassium or calcium, help with the essential nitrogen the cistaceae, lamiaceae, noble or wooded scrubland to sprout with great force from the vine. A curious adaptation to the fire is the cork oak’s tree. The cork is a thick layer of hollow and dead cells that protects and blocks the way of the fire to the vital areas of the tree.

Finally, commenting an interesting co-evolutionary process between fauna and flora in the Mediterranean mount, the birds of the northern Europe migrate to the Mediterranean basin or to Africa, coinciding with its non-reproductive phase. The plenty of attractive and beefy fruits, rich in proteins as well as arthropods of the Mediterranean scrub mean that many species use this area as migratory passage or for the winter season. These individual (calculated in at least 300 million of passerines) joined to the resident ones, play a fundamental role in the dispersion and stratification of seeds (mutualism). However, this is not an exclusive labour of the birds, medium carnivores as the fox (Vulpes vulpes), the badger (Meles meles) or the marten (Martes foina) also contribute significantly in this dispersion. With their food bogey and the decrease of food in autumn and winter, coincides with the fructification of the most part of the scrubland. The result can be easily observed in this epoch because of the high percentage of seeds in their droppings.

Traditional uses and exploitation of the Mediterranean forest

Traditionally, the Mediterranean forest has been transformed by the human being for agriculture and farming, therefore it is a natural and cultural ecosystem, provided with an important historical component. Its meaning and patrimonial value have evolved to the societies’ beat, playing an essential economic role in rural areas. It has been produced systematically an elimination of the woody cover to obtain cultivation grounds, as well as making a dawned and turning some lands to pasture to obtain areas of pasture for livestock. On a small-scale, small transformations of this nature that increase the surface of “ecotone” zones (rim areas between different habitats, for example between a scrubland and a pasture) can increase the biodiversity of a determined area. Nevertheless, this intensive management and transformation of the environment provokes an imbalance, or a balance slanted towards some species, that builds up over time. Often, this kind of transformations leads to the alternation of the well preserved Mediterranean mount with land that were converted into pasture surfaces, small parcels with cereals, olive trees and other types of crops in whom is favoured the diversity of landscapes and habitats. This kind of alterations of the primitive forest in favour of an economic activity, have no reason to exclude animals like the lynx, they can coexist always when the conditions of the habitat are minimally advantageous for the species and there is a sufficient presence of rabbits. Although the best territories in terms of quality of the habitat and plenty of prey are managed by dominant individuals, there are young dispersing lynxes and adults in olive groves and pastures with enough scrub. The presence of the lynx does not suppose any problem for the activity’s development but it supposes an enrichment of the habitat for its important ecological function and as a jewel of our natural heritage.

A Mediterranean climax forest has low productive value for the human being, who obtains bigger benefits in its degradation stages. The pasture is the result and the main support on which the current economic activities on the Mediterranean forest are based on. In addition, this ecosystem has permitted to host an important associated fauna, among them for example is, the hibernation of the crane (Grus grus) or the pigeons (Columba palumbus). This complex producing system created by the human being, agro-sylvo-pastoral, scene of hunting, rotations and cultivations, has been simplified by the dehumanization of the environment. Currently a pure pasture (clarified oak wood and grassland) has high productivity applications, limited to certain seasons, of which take use principally the hunting and the cattle, when the pastures are more nutritive or the rise that takes advantage from the Iberian pig. This, joined to the current low profitability of the forests, should encourage the owner of a forestal ground to the economic diversification for the sake of a major efficiency with the subsidies support where it has to prime quality and biodiversity facing high production and low prices. The overexploitation of properties (intensive farming, abusive holm oak’s pruning with difficult healing, no regeneration of the mount, etc.) that collapses the potentiality of the mount should be corrected in any case. The above mentioned potentiality supposes generating a high production of usable resources. Currently, we advocate a compatible management of the hunting along with the cattle or the cork, as one of the major resources in a rich and diverse environment. The role of the noble scrub is lately is gaining relevance as a decisive factor of food in the summertime for the hunting, highlighting its role in survival at the new feet of oak or cork in their early years (96 % of the current plantation of cork-trees does not have a suitable regeneration). In addition, it maintains a greater structural complexity of habitats that favours other species like the wild boar, birds, rodents... and, of course, their predators that also use it as a refuge or to feed themselves. As an example we’ll talk about the rabbit, essential link of the food chain on that 40 species of predators feed of, some of them specialized in its capture like the Iberian lynx and the Imperial eagle. The rabbit is also a fundamental piece for the smaller hunting. The formation of a mosaic of vegetation that interleaves pastures along with denser formations like Macchia or planting formations, of which also takes advantages the smaller hunting and the bigger hunting, in a suitable population balance, next to the border effect, is more self-sustaining by minimizing for the manager of hunting the need for extra food contributions (bigger hunting in Sierra Morena). Also, the heterogeneity of these scrubs stimulates the production of honey and fungus. This way, recently, the private property is considering with interest the recent tests about the mycorrhizal colonization of fungus, like the Black truffle and others with high commercial value.