Mário Belchior Ávila Gomes
Jardim Botânico do Faial / Direcção Regional do Ambiente
9900 Horta - Portugal
The archipelago of the Azores is located in the North Atlantic between the latitudes of 36º 55´ N and 39º 34 N and the longitudes of 25º 00 W and 31º 30 W. It comprises nine islands with the total area of 2235 square kilometres. The highest altitude is 2351 metres (Pico Island). These are oceanic islands. The distance from the island of Faial (the one located closer to the geographical centre) to Europe is 1480 Kms and 1900 Kms to Newfoundland. These islands are part of the biogeographical region called Macaronesia, the Azores being the northernmost area. The Azores anti-cyclone dominates the climate and it its relative position to the islands that determines the weather conditions. This fact creates an oceanic climate with minor temperature variations, large amounts of precipitation and a very high relative humidity, which is rarely below 75% RH. There is an increase in precipitation from east to west and also in altitude placing the Azores in the humid and hyperhumid zone of Macaronesia.
The Azores were discovered in 1431 and settlement of each island was initiated in different years. Faial was settled starting in 1466. The earliest descriptions of the Azores describe. The existence of dense and tall forests convering the islands almost totally and a large quantity of land and sea birds. This type of forest know nowadays as Laurisilva can be described as a pluristratified epiphyteous forest, with broad leaf perennial trees and bushes. This forest is rich in epiphytic species growing in mild temperatures (with subtropical characteristics) and high relative humidity. In a climax situation the diversity is quite high, with some trees reaching between 10 and 20 meters in height and a large number of endemisms.
From the early beginning of the settlement the destruction of the forests took place, both for the supply of wood and wheat growing. Several domesticated animals were introduced, some becoming eventually wild, such as rabbits that constitued important factors for the destruction of the forest community. In the 19 th century when a large amount of the forest had already been destroyed several exotic species were introduced. Such is the case of Pittosporum undulatum (for hedges), Acacia melanoxlon (for wood), Hydrangeia macrophylla and Hedychium gardneranum (for gardens) which became aggressive invaders occupying extensive areas of the natural forests which were already in the early stages of a state of decay. The Pittosporum replaced almost entirely the Erica and Faya forests up to an altitude of 600 mts. The Hedychium and the Hydrangea colonized the streams, cliffs and open spaces of forest, continuing its spreading until today.
In the 20th century an economy directed towards the raising of cattle and linked with a forestry policy based on the mass plantation of Criptomeria japonica (a fast growing species), brought about the destruction of extensive natural forest zones at altitudes above 600 mts, transforming them in grazing fields and artificial forests. In some islands this situation led to the extinction of the Laurissilva and in other islands to a strong reduction and fragmentation of its area. The case of the island of Faial is typical of what happened in the Azores. Map number 3 represents the potential area of the Laurissilva and map number 4 reflects the present day situation. Since it is a situation that leads to the decay of the forest or even to its extinction, we came to the conclusion that it would be critical that we create the Botanic Garden of Faial, where we would cultivate and reproduce the plants of the Azores, especially those that are considered most at risk. Thus we would also make possible the existence of a collection of endemic and / or autochthonous plants of the Azores and Macaronesia that would also be available to environmental education programs. To this end the Botanic Garden was built on an area of 5600 sq. metres at an altitude of 100 metres. It comprises two collections:
- flora of the Azores and Macaronesia with 95 species;
- medicinal and aromatic plants with 80 species.
Meanwhile we realized that the area of the Botanical Garden was very small. It would be necessary to expand it and a plot of land with an area of 5.6 hectars at an altitude of 400 meters was purchased. The area was made up of artificial pasture (4 hectars) natural forest mixed with the exotic Pittosporum undulatum (0.6 ha.), a raised bog associated to Azoren heaths of Erica scoparia ssp. azorica and small seasonal ponds (1ha).
The area occupied by pasture was divided by hedges of not native plants such as Hidrangea macrophyla, Elaeagnus umbellata and Banksia sp. and large stretches invaded by Rubus divaricatus. The climate in that spot is characterized by high degrees of rainfall and strong NW and SW winds, which are frequent during more than six months each year and often reach over 120 km / hour.
Table 1 shows some meteorological data:
|Precipitation mm/year||Temperature º C||Insolation % of Total Aver./ Year in Coldest Months||Insolation % of Total Aver./ Year in Hottest Months||Summer||Winter|
How it shows the table it is an area with mild temperatures and very low percentage of insolation. The soil is fertile with a rather impermeable layer of 0.50 m. depth approximately. The original rock (basalt) can be found at an average depth of 3 metres. The land is basically level with mild slopes that never reach more than 3 metres. We devised a management plan for the area which was divided in 6 zones:
- area for the reintroduction of Laurisilva forest of the Azores (3ha.).
- wetlands to be recuperate
- are a for the reintroduction of endemic Azorean heaths (Calluna - - Erica - Daboecia)
- collection of the flora of the Azores and Macaronesia.
- collection of old varieties of fruit trees.
- area for support services and a visitors centre.
When the management plan was completed the work was programmed as follows:
- Eradication of non-native plants: from January of 1996 and following years.
- Construction of the main paths: from March to May of 1996.
- Draining of the soil: from March of 1996 to March of 1999.
- Expansion of the wetlands: from June to September of 1996.
- Gathering of plants in the wild: from January to May 1996 and following years.
- Cutting and seeding: from October of 1996 to March of 1991 and following years.
- Reintroduction of the Laurisilva: from May of 1996 and following years.
- Reintroduction of the Azorean heaths : from May of 1991 until the end of 1999.
- Installation of a collection of the flora of the Azores and Macaronesia: from June of 1999 and following years.
- Collection of old varieties of fruit trees: 2000 and following years.
- Visitors Centre and support services: 2000 and following years.
Of the tasks scheduled above the one that raised the most difficulty was the reintroduction of species, especially as concerns the Laurisilva, since it is a complex type of relic forest with a high degree of endemism. Besides, there had been no previous attempts of reintroduction in the Azores. Therefore we had to take into consideration the following:
- The existence of studies on the sociology, ecology and distribution of the plants, alone or in community.
- The need for the observation of the behavior of the different species as regards their growth. The observation is only possible in areas of abandoned pastures that had previously been natural forest.
- How to obtain plants in large enough quantity without specialized production facilities.
- What percentages of the different species to be reintroduced per unit of space.
- What is the influence on the area of reintroduction of the two main limiting factors: the overabundance of water (rain and fog) and the wind.
- And above all, which forest might have existed previously in the area, since at this altitude there exist only fragments of a mixture of primitive forest with a huge quantity of invading exotic plants.
The existing bibliography and field observations indicate that after the destruction of a forest and / or the decay of a pasture the species of trees that can be considered pioneer in those areas are the following:
- Below 400 meters the community of Myrica faya e Erica scoparia ssp. azorica.
- Above 400 meters there is a dominance of Erica scoparia ssp. azorica.
The reference to altitude herein used varies according to rainfall and soil structure. In some areas, mainly in altitudes above 600 meters, one can detect a quick colonization with Erica (3-5 years) and later on gradually other species are to be found, such as Juniperus brevifolia, Ilex perado ssp. azorica, Frangula azorica, and Vaccininum cylindraceum. In sheltered areas we can see Laurus azorica, Viburnum tinus ssp. subcordatum. The herbaceous such as Leontodon filli, L. Rigens Tolpis azorica, Rubia peregrina and ferns such as Blechnum spicant and Woodwardia radicans colonize rapidly the open spaces of the forest. Nevertheless, it is believed that without human intervention it would be necessary for the complete renewal of the natural forest of the Azores a period of time of about 200 years.
Another problem that presented itself was how to obtain a minimum of 8000 plants of different species destined for on area of 3 ha. in a short period of time (about 2 years). It was decided to utilize different methods, depending on the reproductive characteristics and taking into account the fact that the Botanic Garden does not possess rooting greenhouses and does not utilize micropropagation methods.
Below we indicate in percentages how some 8000 plants for the reintroduction were obtained, up to April of 1998:
Species In the wild Cutting Seedling Juniperus brevifolia 95% 5% 0% Ilex perado ssp. azorica 98% 0% 2% Calluna vulgaris 100% 0% 0% Viburnum tinus ssp. subcordatum 50% 48% 2% Daboecia azorica 100% 0% 0% Erica scoparia ssp. azorica 80% 0% 20% Euphorbia stygiana 20% 0% 80% Laurus azorica 99% 1% 0% Myrica faya 70% 0% 30% Myrsine Africana 100% 0% 0% Piconnia azorica 20% 0% 80% Frangula azorica 98% 0% 2% Prunus lusitanica ssp. azorica 0% 50% 50%
One can verify that the gathering of plants in the wild was the most productive method, with the added advantage of maintaining a larger genetic diversity. This gathering is made in the island of Faial only, therefore eliminating the risk of genetic pollution. All the plants were kept in containers between 3-6 months, one year in some cases in a sheltered spot at on altitude of 400 metres. They were watered every two weeks with a solution of 10 grams / 10 littres of Phostrogen. The planting took place in two periods: April - May and October - November. The distance between plants varies from 1-2 meters and they are fertilized at the time of planting and for two years thereafter with 150gr/plant of a compound fertilizer ( N-7% P-21% K-7% Ca-25% S-6%). The percentage of failure after planting has not reached more than 5% in average, being higher in Laurus, Picconia and lower in the other species. As regards the percentage of plants of each species for the area to be the target of reintroduction we thought that the following composition would be reasonable:
SPECIES ENDEMISM % Juniperus brevifolia Endemic to the Azores 5 Ilex perado ssp. azorica Endemic to the Azores 15 Viburnum tinus ssp. subcordatum Endemic to the Azores 5 Erica scoparia ssp. azorica Endemic to the Azores 25 Euphorbia stygiana Endemic to the Azores 1 Laurus azorica Endemic to Macaronesia 15 Myrica faya Autochthonous 20 Myrsine Africana Autochthonous 2 Picconia azorica Endemic to the Azores 5 Frangula azorica Endemic to Azores and Madeira 5 Prunus lusitanica ssp. azorica Endemic to the Azores 2
These percentages though somewhat tentative reflects approximately what could be observed in the remnants of the mixed forest that still remain in the area at about 400 meters of altitude.
Within the area earmarked for the reintroduction there were 0,6 ha. of a forest made up in 50% of old trees of Erica, Juniperus, Frangula, Vaccinium, Myrica, IIlex, and the rest made up by invader Pittosporum undulatum. The invasive plants were cut down. This should apparently have enhanced the conditions of the others. However, because the root system of this type of forest is very superficial, they were in large part uprooted by the wind.
One must come to the conclusion that this type of forest can only survive in close formation which can well withstand the wind. For that purpose a large amount of rapid growing Myrica faya, was planted among the other trees and by natural regeneration several thousand Erica scoparia ssp. azorica grew.
Between 1996 and 1998 some 6.000 trees were planted in the remaing area set aside for the reintroduction. Those trees were listed in the above table. Their behavior towards the outside climatic factors that affect them the most could already be observed.
After the initial two years of the reintroduction one could already verify that in fact the rain and the wind are the factors that made the plantation of a Laurisilva forest in the Azores most difficult. The overabundance of water killed some plants mainly Myrica faya and Picconia azorica that in the future must be planted where the accumulation of water is not possible.
As for the wind it damage strongly all the species with the exception of Erica scoparia spp. azorica and Juniperus brevifolia. The most sensitive specie was Prunus lusitania ssp. azorica, The violence of the wind compounded with the large number of days that it actually blows destroys part of the top of the perennial trees resulting in a delay in growth. To reduce the influence of the previous two factors the following were taken :
- opening of drainage ditches on the spots of higher water concentration;
- planting the species that more sensitive to the excess of water at a higher level in relation to the ground and in sloping areas with good drainage;
- planting of hedges of Erica in rows perpendicular to the dominant winds, each row separated from the next by some 20 metres;
- increasing the density of the Erica, planting them between the rows of already existing trees;
- creating two small forests of Erica on the nearby areas so as to shield some of the wind;
- creating strips of decaying pasture perpendicular to the dominant winds to enhance the natural growth of Erica.
Nevertheless we believe that in the short term these actions will not be sufficient. An artificial barrier will be built with a minimum height of 2m in rows perpendicular to the wind and 20 to 25 metres from each other. As for the herbaceous, small shrubs and ferns their reintroduction is scheduled to take place in 1999. For that purpose we will have to create special habitats such as sheltered, shady ravines. Experiments have already been made with a small number of plants, namely Tolpis azorica and Leontodon rigens, Rumex azoricus (successfully), Ammi huntii and Lycopodium cernuum (unsuccessfully) and ferns Culcita macrocarpa, Woodwardia radicans, Diplazium caudatum, Athyrium filix-femina and Asplenium scolopendrium (with success). In 1998, from through seeding, the following species of herbaceous were reproduced.
HERBACEOUS SPECIES n.º Ammi huntii 50 Leontodon filii 100 Leontodon rigens 50 Tolpis azorica 30 Scabiosa nitens 10 Hypericum foliosum 100 Rumex azoricus 150 Ranunculus cortusifolius 70
Some of the species were obtained through seeding on sand washed with distilled water and covered with a paper filter. A fungicide was applied on the seeds and on the water. Good results have thus been obtained for Tolpis azorica, Leontodon filli, L. rigens, Ranunculus cortusifolius. For other species we have used the method of seeding in peat that had been treated with a fungicide and a permanent water supply. The results have been very good for the Hypericum foliosum and Rumex azoricus. In the both cases natural indirect light was used at normal temperatures. Some time after germination, depending on the species, the seedlings are transferred to pots filled with organic soil. Fungicides and insecticides are used whenever necessary. The seedlings are fertilized every two weeks with a solution of 10 grs/10 lit of water of Phostrogen. The pots are placed in a spot sheltered from the wind and an altitude of 100 meters for six months.
Keeping in mind the results obtained until now, it seems that this is one of the ways to follow in future attempts at reintroduction in the Azores, at least for forests located between 400 and 600 meters. Althrought exact cost estimates have not been made, we can state the amounts involved for the first 3 years are rather high, requiring intensive manpower. It should also be pointed out that the weather conditions in altitude are rather adverse, at least for on average of 6 months per year, preventing quite often the completion of the planned tasks. It is also necessary to invest in research, especially where an effective and cost efficient reproduction of the species that are considered difficult is concerned. Given that the Laurisilva has a valuable rare genetic potential, we should in establishing new pastures and artificial forest, take into consideration the importance of these values in futures agricultural and foresteral policies.
- Allorge, P. et V. (1946) - LES ÉTAGES DE VÉGÉTATION MUSCINALE AUX ILES AÇORES ET LEURS ÉLÉMENTS. Contribuition a létude du peuplement des Iles Atlantides: 386-444.
- Ávila Gomes, M. (1988) - O PROJECTO BIÓTOPOS DO PROGRAMA CORINE NA R. A. AÇORES. Alguns dados para a sua caracterização, SRES-DHUA-Horta.
- Bettencourt, M. L. (1979) - O CLIMA DOS AÇORES COMO RECURSO NATURAL. O clima de Portugal, fasc. XVIII. INMG. Lisboa.
- Carthy, J. D. (1955) - ASPECTS OF THE FAUNA AND FLORA OF THE AZORES. Dep. Zool. Queen Mary College, London.
- Costa Neves, H. (1987) - A IMPORTÂNCIA DA PRESERVAÇÃO DA FLORESTA LAURISILVA DA ILHA DA MADEIRA. I Jornadas Atlânticas de Protecção do Meio Ambiente. Angra do Heroísmo
- Dansereau, P. (1968) - VÉGETATION DE LA MACARONÉSIE. Finisterra. Rev. Portuguesa de Geografia Vol. III, 6: 175-181 Lisboa.
- Dias, E. (1989) - FLORA E VEGETAÇÃO ENDÉMICA NA ILHA TERCEIRA. Universidade dos Açores. Angra do Heroísmo.
- Dias, E. (1993) - METHODOLOGICAL PROBLEMS ON SYNTAXONOMY OF ISLANDS VEGETATION BIOVOLUME AS A RICHER ABUNDANCE - STRUCTURAL PARAMETER. 36th Int. Ass. of Veget. Sc. Symposium.
- Gandullo, J. M. - ESTUDIO ECOLOGICO DE LA LAURISILVA CANARIA. Icona.
- Haggar, J. P. (1988) - THE STRUCTURE, COMPOSITION AND STATUS OF THE CLOUD FORESTS OF PICO ISLAND IN THE AZORES. Biological Conservation 46.7-22.
- Haggar, J.P., Westgarth-Smith, A. R. and Penman (1989) - THREATENED FLORA AND FORESTS IN THE AZORES. Oryx, Vol. 23 n.º3.
- Hansen, A. & Sunding, P. (1993) - SOMMERFELTIA. FLORA OF MACARONESIA. 4 edition. University of Oslo.
- Humphries, C.J.T. (1979) - ENDEMISM AND EVOLUTION IN MACARONESIA. Plants and Islands. pp. 171-197. - Morelet, A. (1860) - NOTICE SUR LHISTOIRE NATURELLE DES AÇORES. Paris.
- Padron, C. V., Borges, J. N. et al. (1981) - LA LAURISILVA. ESTUDIOS SOBRE CONSERVATION FLORESTAL. Instituto Nacional para la Naturaleza. Monografias 46.
- Palhinha, R. T. (1966) - CATÁLOGO DAS PLANTAS VASCULARES DOS AÇORES. Soc. Est. Açorianos Afonso Chaves.
- Santos, Arnoldo (1989) - BOSQUES DE LAURISILVA EN LA REGION MACARONESICA. Conselho da Europa.
- Sergio, C. (1984). THE DISTRIBUTION AND ORIGIN OF MACARONESIAN BRYOPHITE FLORA. Journ. Hattoni. Bot. Lab. n.º 56: 7-13.
- Sjögren, E. (1973) - RECENT CHANGES IN DE VASCULAR FLORA AND VEGETATION OF THE AZORES ISLANDS. Memórias da Sociedade Broteriana. Vol. XVII.
- Sjögren, E. (1989) - BRYOPHYTE VEGETATION IN THE AZORES ISLANDS. Memórias da Sociedade Broteriana. Vol. XXII.
- Sunding, P. (1979) - ORIGINS OF THE MACARONESIAN FLORA. Plants and Islands. pp. 13-40.
- Trelease, W (1897) - BOTANICAL OBSERVATION ON THE AZORES. Annual Rep. Missouri Bot. Garden.
Copyright 1999 NBI