Throughout history, the town planning criteria have prioritized the amount on the quality

Used in isolation, forming small groups, in large masses or forming alignments in streets, tree allows you to demarcate boundaries and areas, provide isolation or create barriers Visual, protect the wind, the Sun or noise, embellish or give shade in recreational spaces. In the city, the width of the streets do not always allow to let grow the tree freely, also the quality of the soil is not always the best.

In fact, the tree in the city was subject to situations of permanent stress and, in general to radically different conditions to them to be in their natural environment, which is why municipal plans, addressing the urban integration of this living elementThey must consider issues such as the nature and the limitations of the numerous existing species, as well as the environment in which will be located, the characteristics of the soil, climate or pollution should bear.

Tree suitable for space but insufficient tree grids.

Historically, since, with the advent of democracy, green spaces in the city gained importance and were considered vertebradores elements within the urban axes, urban planning criteria with regard to implementation of green spaces have had more to do with the quantity with quality. The responsible politicians, in an effort to respond to the will of the citizen - for obvious reasons-, which has been claiming the presence of parkland and woodland road, it has 'sold' their actions in this field in the form of figures: square meters, number of trees plantados… Thus, in the large cities of our country citizenship has seen how in recent decades to the streets of the city they were being granted to each their own row of trees. In just a few years went to live in patched cities of trees planted everywhere indiscriminately. So tells us Dina Alsawi President of the Association of professionals of the green spaces of Catalonia and the technique of gardening of the Commonwealth of municipalities of the metropolitan area of Barcelona: "Is pursuing an Anglo-Saxon image which we cannot pretend our features both as climatic dimension;" It is clear that the presence of road woodland is unquestionable, the citizen claimed, and is an element of order and an exceptional space delimiter, but should not be planted in all partes… "The tree must be located on wide tracks, which has space to develop air way, where can be maintained and controlled with a cost and minimum energy consumption."

There are too many linear plantations made in small holes and on unsuitable soil in our cities

In the same sense manifests Xavier Fàbregas, Professor of gardening and landscaping of the Superior School of Agriculture of Barcelona, of the Polytechnic University of Catalonia. Fàbregas explains that "making the city an aggressive environment for vegetation, both for the bioclimatic conditions space, to be found are species that live well in the urban environment." Trees that can grow, that can provide what they need, invest in new pavement allowing the viability of the growth of the roots, invest in a quality land and buy trees also quality, i.e., that are well cultivated", as well as rethink the urban design, projecting wider sidewalks and seek growth in natural ports without so many interventions".

As a result of the lack of planning, the incorrect preparation of soil or the inadequate selection of species the skyline has been throwing examples of weak or ill, trees other evil anchored to the ground and that they easily fall with strong windstrees pruned drastically to avoid inconvenience to the residents of the adjoining homes, roots that invade pipes, raised pavement and crack muros… Other common mistakes when it comes to locate road woodland are the lack of protection of the trunk in some hot spots such as the entry of a Ford, interference with vertical signs or traffic lights or the lack of foresight in the maintenance.

The amazing resilience of this be live is that it is considered almost inmortal…, so the idea that the tree endures "that throw you", we find too many times with a panorama of woodland unsightly and dysfunctional. Is that the environment of the urban forest is today much more hostile to the of half a century ago: stricter practicality, more demanding technical Compactions, gathered from rain, phasing out of the space (air and underground), aggression and constant alterations, etc.

But not everything is a matter of poor planning. It is true also that large cities, like Madrid or Barcelona, and characterized by having a very aged trees, have experienced deep urban transformations that have brought about a change in the conditions of life of trees. "Small towns, on the other hand, - points the Professor Fàbregas - have a younger trees, and therefore more suited, also the problem of space tends to be less".

The creation of urban spaces is, at present, a task requiring multidisciplinary and, at this stage equipment, local authorities are aware that the introduction and presence of green spaces and street trees is not minor issue. Nobody now disputes the need to incorporate the technical table of any civil engineering specialists in the green. Organic matter exists and is mixed with inert matter that urbanizing our soils, so it is now a component more architectural projects or urban engineering, with all that their presence implies. Dina Alsawi explains in this regard that "for some time, is in new spaces and in the civil works involved a technical agricultural engineer in elements such as ajardinamientos, access to water, etc."

Trees with insufficient tree grates that rise up the pavement and desaconsejadas pruning.

Here are some of the aspects on which begins to put order in the phases of design and implementation of urban development projects so far, not be seen, they have been the source of problems and have generated an enormous cluster of expenses: rational use of species of adult development suited to the space available; correct location and separation sufficient points of planting between themselves, and on buildings and routes of traffic; adequate budgetary allocations and demand and quality control of plant (structure of the plant, training, presentation of the root, etc.); requirement and the quality control of soil and subsoil; proper design of floor tiles and tree grates; coexistence of trees (and roots) with underground services, and control of subsequent changes in the environment of the tree, especially on the ground.

Here are some guidelines to achieve an efficient urban forest, i.e., optimal in relation funcionalidad-coste. The first thing to take into account to achieve cost-effective solutions will be select species whose natural port not enter into conflict with the adjoining buildings, so that requires minimal interventions. So the width of sidewalks wherever planted street tree should not be less than the 3 or 4 metres; in any case must choose small species. More sidewalk space to major ports or with cups globose and aparasoladas species can be selected.

Climatic factors, such as light, temperature, relative humidity of the air, the regime of winds or rainfall, and the characteristics of the soil, have a decisive impact on the development of the tree and in the realization of their physiological functions. Each plant species has a suitable climate under which will reach this full and optimum development, however, there are species with less tolerance than others to adapt to changes in some of these factors, hence the importance of considering the physiology of the species to be used. But, without doubt, one of the biggest problems of the planted trees in the city is the quality of the soil, place where it has to be the root device of the tree; It is common to find us with impoverished soils, sometimes with an excess of lime or sometimes very compacted, which is compounded by the presence of pipes for water, gas, electricity and telephone.

Too often we see to walk around our cities plantations of urban alignments in holes of few dimensions and on soils unsuitable for a proper root development.

Seto badly located under the tree.

Add to this the fact that not all trees have the same root system: some species extend horizontally, which are those that cause further damage, and others delve more into the ground. However growth patterns come largely marked by the characteristics of the soil, such as moisture, nutrients, texture or depth.

Other elements to be taken into account when selecting species put, ornamental features include: If we want to be leaf deciduous or Evergreen, which give varying degrees of shade depending on the season, assess what kind of results generatedIf they mancharán the floor or whether or not they are toxic or cause allergies, etc.

They must be assessed, also, the different alternatives in irrigation systems (today the most widespread is drip irrigation), carrying out a programme of prevention and monitoring of possible pests and diseases, in addition to regular plant protection treatments, as well as the desirability of pruning, factor in which is have been committed, according to the experts, the greatest mistakes. Finally it is advisable to avoid the monoculture, because they encourage development than monófagas pests and also make our streets fall into monotony; introducing species diversity, promote the existence of urban fauna.