1. Arbolapp includes the most common wild trees in the biogeographical unit made up by Andorra, continental Portugal, peninsular Spain and the Balearic Islands. The Spanish and Portuguese archipelagos of the North Atlantic (islands of the Canaries, Madeira, Azores, Cape Verde and the Savage Isles) are not included in this project because they correspond to a different unit, the Macaronesian region, with flora more similar to that of northern Africa. However, the Arbolapp team is working on a new app specifically dedicated to trees from the Canaries.
2. The best place to identify trees using Arbolapp is in their natural environment. The content includes wild species, i.e., those which grow naturally in forests or fields, without human intervention. The species that are normally cultivated and that only occasionally naturalise are not included. That is the case of some fruit trees (e.g., apple, quince, medlar, and various plums) and numerous forest and garden plants have been left out (e.g., cedars, cypresses and some palms). Therefore, this app will not always be able to help you identify the trees you find in parks, gardens, streets, orchards and other agricultural and forestry land.
3. Wild trees may either be native to the region or non-native species introduced by humans that have become established in the wild. Among the non-native species are those that have been cultivated since ancient times (e.g., the common pear, almond, London plane, white mulberry, pomegranate and date palm), those which have a considerable range as cultivated forest (e.g., eucalyptuses, Monterey pines, Canadian poplars, bay willows and basket willows), or which are garden plants (e.g., honey locust, tree of heaven, and black locust). All of these have escaped and become naturalised and, in some cases, they have become invasive, displacing the native vegetation.
4. Arbolapp is dedicated to trees and arborescent shrubs. According to the botanical dictionary Botßnica de Font Quer, a tree is a ôwoody plant, at least 5 m tall, with a simple stem (in this case known as a ‘trunk’) up to the so-called ‘crux’, which branches out in the form of a crown, with considerable growth in its thicknessö. It is not always easy to differentiate trees from shrubs, because there are species that can take a tree or shrub form according to the circumstances. Arbolapp includes all the species of trees on the Iberian Peninsula and Balearic Islands and most of the shrubs that can naturally become trees , known as ‘arborescent shrubs’. Keep in mind that the development of some of these species is limited by adverse ecological conditions, slow growth, or the action of humans, so they are often seen in shrub form.
5. When you are identifying a tree, try to observe more than one specimen or, at least, look at different parts of the plant. Trees are living beings that are conditioned in their growth and aspect by many factors: climate, soil, altitude, time of the year, age, problems and deformations caused by disease or attacks by herbivores or parasites, human intervention, and so on. Therefore, some characteristics can vary or be more irregular, and this makes it advisable to have the greatest possible amount of information.
6. In the case of the leaves, which in Arbolapp are the main identification elements, we recommend that you observe the completely developed adult examples, as well as looking at different parts of the plant and not only at the ends of the branches, as in some species they are arranged differently in the middle or at the ends. It is also a good idea to look at the ground to find old leaves from the previous year if the new ones are not yet sufficiently developed.
7. You can choose between two types of search: guided or open. The guided search involves a series of alternatives where you have to choose the statement that agrees or is most similar to the characteristics of the tree which you want to identify. The option you choose will send you to another alternative, and so on until you arrive at a genus or species. The open search allows you to mark the most obvious characteristics of the tree you are looking at until you find the species, or at least a few options to choose between which will include the one that you are looking for.
8. If at any point in the search you have a doubt and do not know which option to select, you can choose one of these possibilities:
> It may be that you cannot find the organs or parts of the tree you need to look at in order to select an option. For example the flowers and fruit are generally visible for a shorter period in the year than the leaves. In this case, we recommend you click ‘See possible trees’. This will allow you to consult the information sheets for the species the search has narrowed it down to up to this point, and you can look at these to find the species you are trying to identify.
> If, however, you are able to see the characteristics indicated but none of the options is appropriate for the tree you are trying to identify, it may be that you have made a mistake in a previous step. In this situation you have the option of going back to any of the previous steps and choosing a new alternative.
> Finally, if several or all of the options seem valid, keep in mind the fact that the characteristics of trees can be very variable, even within a single specimen. For this reason, in certain steps some species have two or three entries, where more than one option has been included. This means that when more than one of the alternatives is true for the characteristic you are looking at, you can choose any of them.
9. The end result of the search is a tree’s information sheet or a list of trees. Arbolapp has 122 information sheets, 119 of which are of species and three of which are genera: Tamarix, which includes 6 species, Acacia, 11 species, and Eucalyptus, 7. In these cases it is not possible to reach a species because identification at this level is complex even for people with botanical knowledge. For other genera, such as Pinus (pines), Populus (poplars), Quercus (oaks), Salix (willows), and Sorbus (rowans), it will probably be difficult to arrive at species level, due to their morphological variability, the ease with which they hybridise with other species in the genus, or the presence of reforested areas using similar-looking non-native species.
10. Arbolapp is aimed at anyone who wishes to begin looking at or improve their knowledge of the wild trees in their surroundings. For this reason, a special effort has been made to use easy-to-understand language and simple explanations. The most technical terms, sometimes necessary in order to understand the botany, are highlighted so you can click on them to find out their meaning, although they also appear in the app’s glossary.
11. The texts, maps, illustrations and photographs in Arbolapp are based on the scientific knowledge generated by the Real Jardín Botánico (RJB; Royal Botanical Garden), which is part of the Consejo Superior de Investigaciones Científicas (CSIC; Spanish National Research Council). The reference work used in the selection of trees is Flora iberica, developed by Spanish and Portuguese research personnel at the RJB and intended for identifying the vascular plants of the Iberian Peninsula and Balearic Islands. However, we have taken into consideration the latest revisions, specialist consults and the nomenclature changes forced by the application of the rules referring to the classification, retention or rejection of the names accepted in Flora iberica. In developing the distribution maps for each species we have included both the natural range as well as the zones where the trees in this guide have become established in the wild. As a complement to this we have also used the program Anthos, which is developed by the RJB with support of Fundación Biodiversidad, to provide information on the internet about the biodiversity of plants in Spain. We have also used various scientific papers and oral communications given by researchers in the field of botany. Additionally, for invasive species, their current distribution was updated according to the Atlas of invasive alien plants of Spain.
