Genetic Resources and Crop Evolution 00: 1–0, 2001. 2001 Kluwer Academic Publishers. Printed in the Netherlands.
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Conservation strategies and management guidelines for wild Prunus genetic resources in Andalusia, Spain ´ Jose Luis Vivero, J. Esteban Hernandez-Bermejo and Josefa Prados Ligero* ´ ´ The Botanic Garden of Cordoba , Avda. de Linneo s /n, 14004 Cordoba , Spain; * Author for correspondence Received 24 March 2000; accepted in revised form 2 February 2001
Key words: Andalusia, Conservation guidelines, Genetic resources, Prunus, Spain
Abstract Six species of the genus Prunus occur in Andalusia. Matters regarding their ecology, ethnobotanical aspects and conservation are discussed, as well as knowledge about the germplasm of those species with greater economic importance and their degree of conservation, namely: P. avium, P. mahaleb and P. insititia. Various conservation measures are proposed for wild germplasm and for the germplasm of local varieties: a) conservation efforts should target the best populations, except in the case of P. avium and P. insititia, where every individual should be addressed, including both wild and local cultivars; b) the Dehesa del Camarate (Sierra Nevada) is proposed as an area for in situ germplasm conservation; c) the awareness of the importance of Prunus germplasm should be increased among forest workers, environmental managers and the public; d) some silvicultural techniques are proposed, such as mixed Prunus patches, hedge treatment, Z-tree selection at the early stages and the protection of root suckers; e) improved, selected P. avium and P. mahaleb germplasm should be used at highly productive sites since these two species can be cultivated as high value timber trees; f) some Prunus species can also provide profitable NTFPs in the region. Details regarding different collection areas are covered. Finally, some topics are recommended for scientific research. Three tables and a distribution map of Prunus species in Andalusia are included.
Introduction The purpose of this paper is to draw attention to Prunus germplasm in Andalusia, its conservation status and to outline management guidelines, thus providing the basic information that is necessary for this germplasm’s protection and use. A practical goal is that selected sites be proposed for accessions and silvicultural practices that promote the management and use of Prunus species in the region. Very few inventorial studies have been done on the wild Prunus species found in the Mediterranean Basin, in spite of the fact that such inventories are a prerequisite for gene conservation strategies for tree species (Turok et al. 1998). High altitude adaptations and pest resistance that were revealed in ecogeographical surveys of wild relatives of fruit trees are suggestive, since the commercial varieties that are traditionally cultivated at lower altitudes (, 600 m) are very sensitive to
pathogens (Toval and Vega 1988). The genus Prunus is very important from an agricultural perspective, since it includes some very important fruit trees, namely almond, apricot, peach, plum and cherry trees, all of them cultivated in Andalusia. There are 12 wild Prunus species in Europe (Webb 1968), 8 of which ´ de la occur on the Iberian Peninsula (Blanca and Dıaz Guardia 1999). Wild Prunus, especially P. mahaleb, P. insititia and P. spinosa, are very valuable in the improvement of rootstocks that are currently being developed. P. avium is also highly valued for its wood. At present, there is a European Cooperative Program for the Conservation and Exchange of Crop Genetic Resources (ECP/ GR) directly involved in Prunus germplasm conservation, and a Prunus Working Group that was created specifically for this matter. But it seems that the germplasm native to Spain (Socias 1996) has not been a serious consideration within these conservation frameworks.
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2 Targeted species
Species of minor economic importance
Andalusia, the southern part of the Iberian Peninsula, is a cross road between two continents and three biogeographical regions. Moreover, it is home to a wide variety of regional climates and several mountain ranges with high peaks (Sierra Nevada, 3478 m). These features have created an enormous diversity in the region’s flora, with up to 4000 taxa, more than 450 of which are classified as restricted regional endemics ´ (Hernandez-Bermejo and Clemente 1994; Rivas-Mar´ tınez et al. 1997). This same species diversity in Andalusia can be observed in the genus Prunus, with the presence of six out of the eight wild species, namely: P. avium, P. insititia, P. mahaleb, P. prostrata, P. ramburii and P. spinosa. The other two species, P. lusitanica L. and P. padus, L. are not currently present in the region, but it is quite probable that they were in the past. They disappeared mainly ´ due to the climate constraints (Vivero and HernandezBermejo 1997). P. lusitanica was sighted in Sierra de ´ Algeciras, province of Cadiz and P. padus in Sierra Nevada, province of Granada. Of the six species found in Andalusia, this paper focuses on the species which have a distinct economic or social value: P. avium, P. insititia and P. mahaleb. Though the other three are of minor importance economically (P. prostrata, P. ramburii and P. spinosa), their main features are outlined and included in the general conservation guidelines. Their distribution in the eight provinces of Andalusia is shown in Table 1 and Figure 1. P. avium is a special case since it grows wild and cultivated at the same time in many places and it is difficult to distinguish natural forms from cultivated ones. Since it is a traditional crop in the region, its many semi-domesticated and wild forms make Andalusia an important center for germplasm diversity on the Iberian Peninsula.
Prunus prostrata Labill Its name comes from its prostrate growth habit, since it adapts to the microtopography of the rocks where it grows. It is distributed throughout the Mediterranean Basin. In Spain, it only occurs in the oro-mediterranean thermotype found in the eastern provinces (see Table 2 and Figure 1). In Andalusia, it is widespread all along the Baetic Range, reaching all the way to ´ Cadiz in the south, with no threats to its survival foreseen in coming years. No uses for this species are reported in literature, nor known from the field. The ´ herbarium at the Botanic Garden of Cordoba houses more than 50 specimens from the region. Recently, a different and more erect form (P. prostrata f. erecta ´ Molero) was found in Sierra del Jobo, Malaga (Lora and Vivero 1998). Prunus spinosa L. This species grows in nearly all the European countries, the Caucasus, northwestern Africa and southwestern Asia, all the way to Iran. It prefers calcareous soils in rocky places and on ledges, at either high or low elevations. It is more abundant in the north and center of Spain, and is only rarely found in the south. It occurs in all of the provinces of Andalusia, but only in very few places. Watkins (1976) considers it one of the parental species of P. domestica. Another hypothesis indicates that it may be the parental species of P. insititia, which, later on, evolved towards P. domestica. The latter of the two would thus conserve the characteristics of its primitive parental species, P. spinosa. Its fruits are used in the north of Spain to produce a liquor called ‘Patxaran’, which is in great demand in the Spanish market (Ruiz 1989). It is not
Table 1. Presence and population sizes of Prunus species in the eight provinces of Andalusia.
P. avium P. insititia P. mahaleb P. prostrata P. ramburii P. spinosa
´ Almerıa
Granada
´ Malaga
´ Jaen
´ Cordoba
? x x X XXX ?
XX XX XX X XXX X
x X XXX XX
XX XX XXX XX
XX X
XX
XX
x
Legend: (XXX) big population; (XX) abundant; (X) rare; (x) one or two localities.
Sevilla x x
x
´ Cadiz x XXX X X
Huelva X x
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Figure 1. Distribution of Prunus species in Andalusia.
threatened regionally, nor in a larger context. Its uses and ethnobotanical applications in the region are very rare and localized, therefore we do not consider it necessary to immediately develop a specific conservation and management plan for its germplasm, since it
will benefit from the conservation plans that will be applied to the species of major economic importance. It potentially could be quite valuable as a rootstock for commercial Prunus species in genetic improvement programs. It seems that there are many genotypes
4 Table 2. Conservation and ethnobotanical features of the germplasm of Prunus species in Andalusia.
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IUCN category Degree of Endemncity 2 Biogeographical singularity 3 Ethnobotanical importance 4 Importance of wild germplasm 5 Likelihood of sustainability 6 Regional occupancy 7 Neglected crops 8 Susceptibility to genetic effects of natural regeneration systems 9 Minimum bioclimatic level 10 Maximum bioclimatic level 10 Population size 11 Habitat specific 12 Flagship species 13 Wood 14 Relative endemicity 15 Threats
P. avium
P. insititia
P. mahaleb
P. prostrata
P. ramburii
P. spinosa
VU WD Intermediate High High
VU WD Low Intermediate Intermediate
LRcd WD Intermediate Intermediate High
nt MB Low Low Low
VU EA High Low Low
nt WD Low Intermediate Inter
Low 580 Important Low
Intermediate 250 Important Low
High 1700 Little Low
None 1350 None Low
Intermediate 1200 None High
Intermediate 720 Little Low
Meso Supra , 1000 Yes Yes High Low Fire, tree felling and natural decline
Meso Supra , 5000 No No Low Low Fire
Meso Oro , 10000 No No Intermediate Low Fire
Meso Oro . 10000 Yes No Low Intermediate None
Supra Oro , 10000 Yes No Low High Fire, local use and biological factors
Termo Supra , 5000 No Medium Low Low Fire
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´ After Vivero and Hernandez-Bermejo (1997). EA: Endemism restricted to Andalusia. MB: Restricted to Mediterranean Basin. WD: Widely distributed. 3 Ecological and geographical characteristics of the species that make their gene pool somewhat different from other populations within the same distribution range (i.e. adaptation to higher elevations or drier climate, border area of a broader range, relic species, different subspecies or varieties). 4 See Table 1. 5 Present and potential future importance of their germplasm for use in genetic improvement programs, for rootstock properties, disease tolerance, wood quality, characteristics of the fruit, etc. 6 After Newton (1998). Depending on which part of the tree and with what intensity it will be used, the sustainability will be higher or lower. 7 The total occupancy area (km 2 ) is estimated by the index: UTM 3 100 3 CA, where UTM is the number of grid squares (10 3 10 km 2 ) and CA is the maximum percentage of each UTM grid square physically occupied by the species. 8 This aspect refers to the agricultural or economical importance of the species in the past. 9 The actual susceptibility will vary per species, biology, population size, and how extensively the silvicultural system is applied (Joyce et al. 1999). And the genetic effects that affect the genetic variability can be: local extirpation (the loss of a local population due to regeneration failure), inbreeding depression, genetic drift and high grading (leaving phenotypically undesirable trees for seed production). 10 ´ After Rivas-Martınez et al. (1997). Thermomediterranean (0–700 m); Mesomediterranean (700–1300 m); Supramediterranean (1300–1800 m); Oromediterranean (1800–2800 m). 11 ´ Estimated number (after Hernandez-Bermejo et al. (1998)). 12 After Rabinowitz (1981). 13 Species that are well known by the public and are well considered. The possibility of obtainining program funding is higher than for other species. 14 High: Highly valued wood with several applications. Intermediate: Wood used to make small objects, or in specific activities. Low: Wood with no or just a few restricted applications at present. 15 After (Freitag and Van Jaarsveld 1997). 2
resistant to PPV in wild P. spinosa populations that could be used as dwarfing rootstocks or intrageneric stocks for plums and apricots (Ogasanovic 1996). Prunus ramburii Boiss. This is the only Prunus species endemic to Spain,
with a very restricted range at high altitudes (1200– 2000 m) in the three Baetic mountain ranges: Sierra ´ Nevada, Sierra de Baza-Filabres and Sierra de Gador. Lower altitudes represent a barrier to its extension. In this ancient, widespread genus, it is quite uncommon to find an endemism with such a restricted range. It is a neoendemism whose origins date back to the
5 Quaternary, with P. spinosa as ancestor (Vivero and ´ Hernandez-Bermejo 1998). Due to its reduced range, its endemicity and several threats it faces, such as fire, tourism and low seed production, it is rated Vulnerable and has appeared in the recently published world list of threatened trees (Oldfield et al. 1998). Therefore, a program has been outlined to conserve its populations in Andalusia, as is explained in this paper. Some of its biological features should be highlighted, such as its pronounced demand for light exposure and its very low fructification levels (Vivero and ´ Hernandez-Bermejo 1998). Nonetheless, it is commonly propagated by vegetative means (root propagules). It is abundant within its range, forming characteristic shrub communities, with some populations that are protected in Natural Areas. There is no literature regarding its uses, but we report that a kind of ‘Patxaran’ liquor is made with its fruits in the Sierra Nevada National Park.
Species of major economic importance
Andalusia, it occurs in scattered populations on several mountains at elevations of 1300 to 1800 m, in habitats that favor this species because the lack of water is mitigated during the summer months. The climate nowadays, with its long dry summers, greatly restricts its range in the region and may even affect its survival in the next decades. In Sierra Nevada, it is not clear whether the populations are wild or naturalized. ´ In Malaga, all the populations seem to come from trees escaped from cultivation, either recently or some centuries ago, since the habitats where they occur are not those most suitable to them. Prunus avium is rated ´ vulnerable in this region (Vivero and Hernandez-Bermejo 1997). In response to frequent summer droughts, P. avium grows in the wet ravines of the Andalusian mountain ranges, in circle formations produced by saplings which grow from the main tree’s roots. It also appears at the bottom of cliffs, as a result of seed dispersal by birds and mammals. It prefers cool, deep soils, since it has a taproot capable of growing very deep. Though it is indifferent to edaphic conditions, it does grow better in acidic soils. As a crop, it has traditionally been associated with marginal orchards in mountain areas in Spain. In some countries, such as Canada, France and Belgium, breeding and genetic improvement programs for commercial varieties and rootstocks were started several decades ago. At present, there are wild P. avium germplasm evaluation programs in UK, Belgium, in Navarra (Puertas and Traver 1997) and Galicia (Vega 1996), Spain, among others. Most of them focus on improving timber quality.
Prunus avium L.
Prunus insititia L.
Its natural range includes Europe, western Asia and northern Africa, but it has been introduced or naturalized in many countries. During Quaternary glaciations, as can be inferred from its present distribution and from paleobotanic and paleoenvironmental data, the Iberian Peninsula probably was a refugium for P. avium coming from central Europe, as was the case ` for Quercus spp. (Dumolin-Lapegue et al. 1997) and Fagus spp. (Demesure et al. 1996). This is why it is considered a relict species with declining populations. There are scattered populations in a geographical strip stretching from Sierra Nevada to peninsular Italy, which occur between its core range in central Europe and the southern limits of its range in the Atlas Mountains of Morocco. On the Iberian Peninsula, it is common in the north, becoming rarer in the south. In
This species occurs in Europe, the Middle East and northern Africa. On the Iberian Peninsula, it occurs in ´ de la nearly all of the provinces (Blanca and Dıaz Guardia 1999). It prefers hedges and forest borders in meso- and supra-mediterranean thermotypes, normally with scattered or very few individuals per stand. It is found in mountain areas in all of the eight provinces of Andalusia, at elevations no higher than 1600 m (see Table 2), though five of the provinces have only one population each. Some of these individuals may actu´ ally be naturalized P. domestica (in Malaga or the ´ Sierras Subbeticas, Cordoba). It always occurs in wet habitats: in ravines, along steep pathways and slopes, in hedges, and in riparian or oak forest borders. It is indifferent to edaphic conditions (Ruiz de la Torre and Ceballos 1971).
Prunus x fruticans Weihe This hybrid species, described 100 years ago, has rarely been sighted on the Iberian Peninsula. It has recently been recorded in three places: Granada, Cuenca and Girona (see Figure 1). Its origin is not yet clear. It is either a natural hybrid of P. spinosa and P. insititia, or of P. insititia and P. domestica, the latter option being more probable than the first.
6 Prunus mahaleb L. This species is widely distributed throughout the Mediterranean Basin, reaching all the way to Norway in the north and to Iraq in the east. It is quite abundant on the Iberian Peninsula, and its presence has been recorded practically over the entire peninsula (Blanca ´ de la Guardia 1999). Its ecology on the and Dıaz Iberian Peninsula is quite varied, with individuals found growing on high rocky mountains as well as at sea level, and in cool, wet places or on exposed, sunny slopes. In Andalusia, it occurs in the Baetic Range, where it normally grows in scattered groups throughout the forest. It is widespread on mountains, in deep valleys, in canyons, on cliff walls and in gorges. It occurs at altitudes between 1050 and 1900 m, which is higher than the elevations where these plants are normally found on the rest of the Iberian Peninsula (Vivero et al. ). It prefers sunny places, but it can be seen growing well in shaded fissures and holes, with no light; or in very wet, dark ravines. Based on these facts, we considered this a very shade tolerant species, though it does prefers warmer, well-lit places. It clearly prefers calcareous soils, but there are two rather interesting populations (Sierra de Horna´ ´ in silicechuelos, Cordoba and Sierra Morena, Jaen) ous soils. Its reproduction biology has been studied ´ 1993; Guitian ´ et al. 1993; Herextensively (Guitian rera and Jordano 1981).
fruits. Fruit: wild trees yield between 4 and 16 kg of fruit, that can be eaten fresh or in jams. The fruit is also an important food source for birds, mammals and insects living in the forest. Gardening: it is used for its brilliant autumn foliage. Timber: a heavy hardwood with a dark reddish grain pattern that is highly valued for carvings and furniture making. After walnut, it is the hardwood that is second most in demand in the ´ de Rueda 1991). Medicinal European market (Orıa Uses: see Table 3. The fruit peduncles boiled in water are used as a diuretic, and for bladder and liver infections (Sierra Nevada, Sierra de Baza and ´ Cordoba). Other Uses: its flowers are popular with bees, which produce a strongly scented honey from the nectar. Prunus insititia
Economic and ethnobotanic interest
Agriculture: its main use is as a rootstock for stone fruit trees, mainly plums and apricots. Because P. insititia belongs to the Prunus subgenus that shares a common gene pool with other subgenera, it is able to act successfully as a rootstock. Fruit: they can be eaten either fresh or dried, being excellent laxatives. Timber: reddish-pink, with a fine, compact grain, perfectly suited for polishing to a rich luster. Medicinal Uses: see Table 3. Its most extended use is as a laxative and as an ingredient in common cold remedies. The leaves and seeds also contain a glucoside, amygdalin, that is used in the pharmaceutical industry as a substitute for bitter almond essential oil (Ruiz de la Torre and Ceballos 1971).
Prunus avium
Prunus mahaleb
P. avium is one of the most useful trees of Europe. In many cases, it generates a higher profit than Eucalyptus, Pinus and exotic Abies species, as a result of its multiple by-products. One of the main constraints for its use in plantings is its initial delay in fructification (8–10 years), though it does grow as a pioneer species during the first stage. At present, its impact on the Iberian ecosystems is minimal, since it only occurs at low densities. Given its multiple uses and scarcity, it has been used extensively for several decades in reforestation and landscape management plans undertaken in central Europe, especially in Germany and France. Agriculture: wild specimens are used as rootstocks in some areas (Sierra de Aracena, Huelva). Beverages: homemade spirits are made from the macerated
Agriculture: at present, this species is one of the most widely used rootstocks in the sweet cherry orchards of Spain, especially in Aragon and Catalonia, where it is well suited to the dry and calcareous soils found there (Herraiz 1992; Gella 1990). These rootstocks permit the cultivation of commercial varieties of P. avium, which is more adapted to wet, acidic soils. The Moors used it as rootstock when they introduced its cultivation in the Iberian Peninsula. Fruit: though the fruit is not currently consumed in Andalusia, it is used to elaborate traditional desserts in Iran and Iraq. Gardening: several special garden cultivars exist which are mainly planted in central European countries. It is also used to form hedges since it sprouts readily after pruning. Timber: whitish-pink, with a pleasant scent due to the essential oil (coumarin) it contains. It has a
7 Table 3. Medicinal and other uses of the major Prunus species Prunus avium Antihistamine Hemorrhoid treatment Diuretic Bladder infection relief Rheumatism treatment Antispasmodic drugs Laxative Astringent Digestive aid Sedative Cold remedies Rootstock Alcoholic beverages Fresh fruit Gardening Timber Honey
Prunus insititia
d d d d d d
Prunus mahaleb
Prunus ramburii
Prunus spinosa
d
d
d
d d
Prunus prostrata
d d d d d d d d d d
d d d d d d
very homogeneous grain and is readily polished. It is used to make cigar boxes, pipes and walking sticks. Theophrastus (4th century B.C.) mentions that its wood was used for carriage axles and for plows. Medicinal Uses: see Table 3. It is a digestive aid and a diuretic.
Current situation of germplasm evaluation in Andalusia Although the flora of Andalusia has been relatively well researched, its tree germplasm has not been surveyed to the same extent, with no reference materials on the topic. Variation patterns within species, subspecies or varieties are entirely undocumented in many cases, as for Prunus, both for wild populations and for local cultivars. Little has been done with regard to the collection of wild germplasm, and only some notes can be found about germplasm accessions in the region. For example, there are no accessions of wild P. avium from Andalusia at the Experimental Research Center in Aula Dei, Zaragoza; and at the ´ Aragon Regional Government;s Department of Fruticulture, there are only several wild germplasm accessions for P. ramburii. P. mahaleb, in spite of being a valuable genitor for rootstock breeding programs and for seedling plantations, is barely present in the state-run genebanks of Europe, and almost non-existent in Spanish genebanks (Socias 1996). Some work has recently been done with this species in Turkey and Yugoslavia (Gass et al. 1996). Moreover,
d d d d
d d d d d
most of the institutions have tended to preserve the germplasm of commercial varieties in their collections, rather than that of wild Prunus species. Additionally, some old cultivars have been replaced by the introduction of modern cultivars. This situation has caused the extinction of many locally developed and climatically well-adapted old cultivars (Gass et al. 1996). Andalusia is still home to many local old cultivars of P. avium, since little work has been done in the region to commercially improve this crop in recent decades. Therefore, a project should be undertaken to collect, evaluate and conserve these varieties, which may result in very interesting material for current genetic improvement projects. Due to the methodological approach, it was outside the scope of this paper to embrace the local landraces of Prunus fruit trees and their evaluation. Vigorous wild P. avium individuals with good tree structure (a straight trunk with light branching) can be used for clonal trials in timber-oriented cherry breeding programs, as has been done in East Malling, UK and in Gembloux, Belgium. Or well adapted P. spinosa and P. mahaleb trees can be used as a source of resistance and tolerance to biotic and abiotic stress. Some areas that must be surveyed and evaluated are proposed as Provenance Areas in this paper, since they are primarily where these local varieties occur. In other cases, Selected Seed Stands would be advisable in the Natural Parks (NP) and the Regional Natural Areas (RNA) in order to develop specific programs to conserve this wild germplasm. See Figure 2 for a map
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Figure 2. Protected natural areas in Andalusia.
with the regional network of protected natural areas in Andalusia.
General guidelines for Prunus conservation efforts General guidelines for a useful, cost-effective conservation program and specific silvicultural practices for managing the region’s Prunus germplasm are outlined in this section. These guidelines and subsequent conservation efforts are based in large part on the excellent paper on noble hardwood species issued by Rotach (1999), with the necessary modifications required to adapt his guidelines to the Mediterranean Region and to the specific characteristics of the Prunus species in Andalusia. As is the case with several of the species studied, this adaptation is especially important in less than optimal areas on the northern and southern borders of the species’ distribution area. Some silvicultural practices and conservation efforts are proposed as well, in order to increase the numbers of trees, to enhance public awareness of these trees, to improve the quality of the wood and its market profitability and to reduce its competition with other species. For a summary of the features of these Prunus species, see Table 2. For a better analysis, we will combine in situ and ex situ
measures in the hands-on conservation efforts, though we believe that whenever possible, the former should be higher priority than the latter. Guideline 1.A.: Conservation and promotion efforts should focus on ecologically optimal sites, natural niches or special habitats, although all P. avium, P. insititia and P. x fruticans individuals should be conserved whether they are located in ecologically optimal sites or not. Concentrating efforts on ecologically optimal sites will lead to less intensive silvicultural interventions and will thus allow us to focus our efforts on the so-called ‘core populations’. In marginal or border areas where these species are rare or in situations where they are severely threatened, other conservation measures should be undertaken regardless of site conditions. P. avium shows a border area pattern in the region, since it is quite far from its optimal ecological and climatic niche. As mentioned before, most of the habitats where it occurs are relict and highly sensitive to degradation and destruction. For P. x fruticans, this is even more evident, since it only occurs in one or two places (though its taxonomic position inside the group is not yet clear). Other possible efforts could be focused on limiting in situ measures to populations of more than 20 individuals, as proposed in Turok et al. (1998). For P. avium and P. insititia, concentrating conservation efforts on
9 stands with more than 20 individuals seems reasonable; while for P. mahaleb and P. spinosa, the populations should have more than 50 individuals. A population is defined as at least 20 individual trees, all distanced more than 50 m apart and distributed over an area not exceeding 10 hectares (adapted from Demesure (1998)). Guideline 1.B.: Some Prunus species should be favored in special stand structures or habitats that are particularly advantageous Such special habitats should be managed primarily for the endangered minor or rare species. The following special habitats are interesting for less competitive Prunus species, i.e. ones which require more sun exposure, are slower growing and are smaller in stature, such as P. insititia, P. mahaleb, P. ramburii and P. x fruticans: a) Forest borders Special treatment of the forest border is necessary in order to promote these species. Patch-size plantings is the favored solution since competition with other shrubs will be severe in the stand-establishment phase. b) Hedges or small forest patches dispersed over agricultural land. It is well known that these forest patches are not only important landscape elements, but are also valuable as retreats for plants and animals, as wind barriers and much more. Conservation efforts As mentioned above, P. avium is a relict species with declining populations in the region, therefore the protection of all its populations and individuals should be strictly enforced, also including naturalized local cultivars and old abandoned varieties. Nonetheless, we cannot forget that it also is a species with commercial value (the price and demand for its timber continue to rise) and some silvicultural guidelines for its utilization will be drawn up as well. The best stand is on the northern slopes of the Sierra Nevada National Park (Dehesa del Camarate) in a mixed old broadleaf forest with Quercus pyrenaica Wild., Sorbus aria (L.) Crantz, Sorbus torminalis (L.) Crantz, Salix caprea L., Betula pendula Roth subsp. fontqueri (Rothm.) G. Moreno et Velasco, Acer opalus Mill. subsp. granatensis (Boiss.) Font Quer et Rothm. and Malus sylvestris (L.) Mill. This forest is a private property even though it is located within the National Park, therefore it could follow a timber management program. Considering its extention, its excellent state of conservation, its significant population figures for several interesting, threatened species and its econ-
omic potential for timber and non-timber products, this area should be selected for a pilot program on tree germplasm conservation and utilization. It is a key place for linking seed conservation, in situ management of genetic diversity conservation and the sustainable use of timber and other products and services, such as tannins, mushrooms, wood, coppice, pulp, soft wood, game preserves and grazing areas for cattle. This pilot program is to be controlled by the National Park authorities. This area is a real hotspot for rare and threatened trees in Andalusia, and two other Prunus species also occur there: P. insititia in low numbers and P. ramburii at higher altitudes. The stands with the best and biggest populations of P. mahaleb are in the Sierra de Grazalema RNA ´ (Sierra del Endrinal and Pinar del Torreon), in the Sierra de Cazorla, Segura and las Villas RNA (Madera ´ Perea fields), the oak forest in valley and the Hernan ´ the Sierra de las Nieves RNA and the Sierra Magina RNA (the north face of Cerro Campanario). Although it grows very well in shady locations, it prefers sunnier exposures and hence it is a potentially good candidate for border silvicultural practices. There are considerable populations of P. ramburii in the three main mountain ranges where it occurs, since this is its optimal habitat. The best stands are in Sierra de ´ Gador, a rather important natural area with outstanding plant endemisms that is not under any legal protection, in the Sierra Nevada NP (Trevenque, Puerto de la Ragua, Dehesa del Camarate and Vereda de la Estrella) and in the Sierra de Baza RNA (at higher altitudes). Special attention should be paid to the species’ border areas, since this is where it adapts to a lower habitat, namely Sierra de Filabres, Sierra ´ Mecina and Sierra de Lujar. Most P. insititia individuals occur in isolated groups scattered over the mountain ranges, with some ´ small stands in the Sierras Subbeticas RNA, the Sierra Nevada NP (Vereda de la Estrella, Dehesa del Camarate, Maitena valley), the Sierra de Cazorla, Segura and las Villas RNA (Madera valley) and the Sierra de las Nieves RNA (Genal valley). This species will benefit most of all from silvicultural practices along the forest boundaries and hedges, since it is not very competitive and it is seriously threatened by introgression and genetic drift. Finally, since P. spinosa and P. prostrata are widely distributed throughout the mountain ranges of Andalusia with high population figures, no special conservation measures are proposed in this area. As for P. x fruticans, the only place where it is known that it grows in the region should be better
10 surveyed and its population totally protected. Some ex situ measures are recommended below, such as collecting and setting up a core collection for cultivation. All the aforementioned stands, due to the number of trees, can all be considered Selected Seed Stands for each species and hence properly managed to obtain high quality, selected, certified seeds for several purposes. All these areas will thus have an additional economic value. Guideline 2: For the successful conservation and promotion of Prunus species, public perception of most of these species needs to be improved, especially the least known species. People working in the field need to be better trained and better motivated. As is logical, perception or awareness have a direct correlation with knowledge, information and motivation. Consequently, the promotion of Prunus species will neither be efficient nor successful unless the personnel working in the field are properly trained and committed. Fortunately, in the Andalusian network of Natural Areas and National Parks, most of the field personnel know and easily recognize these Prunus species and know where they are located. Nonetheless, most of the personnel are not aware of the species’ economic and ecological importance as genetic resources. This same awareness principle must be applied to government managers and park visitors. All of these Prunus species are frequently found in small populations in the natural sites within the region. Their populations could thus be increased considerably by training and supervising field staff to undertake early interventions in young stands. Conservation efforts Firstly, several workshops for foresters and forest keepers should be organized in the Natural Areas where these species occur in order to increase their knowledge and appreciation of these Prunus species (as well as several other threatened, broadleaved species) and their ecological and economic importance in the region. A network of regional decisionmakers, forest keepers and researchers could then be set up in order to bring information about Prunus species up-to-date and to undertake conservation and management activities with their germplasm. Secondly, permanent expositions or in situ collections should be established in the Natural Areas where they occur in order to raise awareness among visitors. These collections would fulfill a triple role: as tourist attraction for the area, the promotion of species awareness,
and as approved seed or seedling suppliers for other natural areas or commercial gardening enterprises. This last idea, already mentioned in Guideline 1, would not only increase the awareness of Andalusian plant germplasm, but would also produce economic benefits. A better knowledge of the genus Prunus in Andalusia would lead to more intensive use and enhanced consideration of its germplasm, either in revegetation programs, slope fixing or in appropriately weighing its importance in Environmental Impact Assessments. Guideline 3: For species that are threatened by introgression from domesticated germplasm (namely, P. avium and P. insititia), natural regeneration needs to be accompanied by plantings. Germplasm should be highly diverse and contain a large proportion of wild genotypes from each respective origin / source. For certain species, natural regeneration may not be sufficient for gene conservation. P. avium and P. insititia may, owing to their occurring at low densities, primarily cross-pollinate with domesticated individuals (commercial or local cultivars) outside the forest, and hence, it is doubtful whether P. insititia and P. avium populations in Andalusia can be considered as having any pure wild germplasm. For gene conservation, these species need to be enriched with genetically diverse material which contains a high proportion of undomesticated genotypes. Therefore, a reasonable solution for the above-mentioned species is the establishment of seed orchards which contain natural wild genotypes and produce genetically diverse material. The conservation of these Prunus species may require more effort and financial backing. Since P. avium can generate high revenues from the market price for its timber, these efforts may be worthwhile for the regional government and for some timber companies. Conservation efforts The establishment of a Special Seed and Seedling Orchard with the aim of conserving and enhancing genetic variation in the wild germplasm of P. avium and P. insititia could be carried out by one research ´ institution, such as the Botanic Garden of Cordoba, in order that all the efforts, research and material be centralized in a single place, thus enhancing the interbreeding and the increase of genetic variation. Some preliminary research should be carried out in order to better determine which stands or individuals have real wild germplasm (by using molecular
11 markers or historical and geographical data). There will be many cases that create doubt, such as individuals growing in abandoned farm plots, in areas close to a road, or in semi-urban areas, etc. Moreover, special tree germplasm should also be included in this seed orchard, such as the germplasm from P. mahaleb found growing in acid soil (Sierra Morena, Collado de ´ and Conquista in Cordoba) ´ los Jardines in Jaen or from old growth individuals (P. avium in Sierra de ´ Aracena and P. mahaleb in Sierra Magina). Here are some examples of naturalized or semi-domesticated germplasm with no clear wild origin: P. insititia / P. ´ domestica in Sierra Bermeja and Sierras Subbeticas; P. x fruticans and its relationships with the former taxa and wild P. avium in Sierra Nevada, Sierra de ´ Aracena and Sierra Magina. In order to avoid future introgression from non-native germplasm, the genetic material from reforestation programs should be carefully checked and, whenever possible, come from certified Andalusian material. Special care should be taken both in the establishment of new orchards of P. avium and P. domestica in the ranges where their wild relatives occur, and with the possible introduction of P. spinosa in Sierra Nevada for the elaboration of the ´ de la Sierra’, since it produces larger, liquor ‘Patxaran more abundant fruit than P. ramburii. Guideline 4. 1.: Silvicultural techniques to enhance Prunus populations in Andalusian forests. In Pinus or Quercus dominated sites, Prunus species should be planted in mixed patches ( groups of trees) rather than as single trees. The growth rates for these species differ considerably from those of pines and oaks, which are the dominant Mediterranean tree species, and the competitive ability for many of the Prunus species in question is generally rather weak (with the exception of P. ramburii and P. avium, which are pioneer species). In groups of trees, these growth differences are less important since competition is restricted to the contact zone between the species. Therefore, group mixtures are recommended since they are more stable, silviculturally less intensive and thus more efficient than tree-by-tree mixtures. Guideline 4. 2.: In young stands with a high proportion of Prunus species, initial interventions should be aimed at favoring them primarily. At least one intervention is necessary at the thicket or pole stage, using early plus tree (Z-tree) selections, in order to conserve and favor existing Prunus species. The first 10 years are decisive for the survival of most Prunus species, since all of them (except P.
prostrata and P. ramburii) easily lose out to the competition during their first 10–15 years. Early intervention therefore is essential for their survival and conversion into future stands. At least one intervention during the thicket stage is necessary to regulate the mixture and to favor all the forest Prunus species. Because of financial constraints, early interventions need to be kept to a minimum and restricted mainly to stands with high proportions of Prunus species. If Prunus individuals are selected as a top priority, their chance of survival can be increased considerably with little investment. For Prunus species still occurring in moderately large populations (P. ramburii, P. prostrata and P. spinosa), efforts and financial resources should be invested primarily in supporting natural regeneration and early interventions. The promotion of some species depends primarily on vegetative propagation. The species P. avium and P. insititia frequently produce root suckers. Consequently, the promotion of Prunus species is especially promising in stands where a certain number of mature individuals occur. Root suckers can develop at a distance of up to 25 m from the main trunk, so immature individuals should not be cut, but rather left as standards until they reach maturity. In addition, protection against grazing is necessary in most cases since Prunus seedlings are especially vulnerable. Conservation efforts Since the conservation and enhancement of broadleaf species in Mediterranean forests should be a common goal in all the silvicultural practices undertaken either for conservation or commercial purposes, these three practices must be performed in many forests in Andalusia, especially in the mixed forests and in those that are under protection. These practices should be added to the regional Natural Areas’ forest management plans and their use should be promoted among the wood and forestry industries (either by legal means or by state grants). Guideline 5: If a high silvicultural intensity can be guaranteed, P. avium and P. mahaleb /may also be promoted on highly productive sites. Growth and productivity would be optimal on such sites and the return on investments would be high for both species. For these plantations, only improved material with the best phenotypic quality should be used. Today, biological diversity is as equally important an objective as production. Consequently, all minor Prunus species should be favored, even if the mix-
12 tures are not ideal from a silvicultural perspective. The economic potential of some Prunus species is very high. We believe that the prospects for the future are even better, since certification would increase the demand for locally, ecologically and sustainably produced wood and non-wood products. P. avium and P. mahaleb would both profit considerably from certified sustainable production of their useful and highly valued timber. These species are more valuable than the dominant species (Pinus or Quercus), in spite of the fact that their production volume is lower. P. avium, P. insititia, P. ramburii and P. spinosa would benefit from the certification of some products other than wood, the so-called Non-Timber Forest Products, as explained below in detail. Wood quality primarily depends on stem form and the branching habit, and these traits are often unsatisfactory for these Prunus species because they have been suppressed for too long. For example, production values for P. avium are often insufficient due to its frequent forking and sinuous stem forms. Improving these traits by breeding would thus considerably enhance the value of its timber. Genetic improvement and seed production are efficiently achieved in seed orchards that have selected, tested clones. Considering the difficulties that exist in the collection of a large number of seeds from some Prunus species, orchard seeds may even be more diverse since the genes of more trees may be represented in the offspring. Finally, Non-Timber Forest Products (NTFP) are becoming more and more a source of high income for well managed forests. So far, their importance and economic value with regards to the forests of Andalusia has yet to be assessed as a whole. Up till now, the increasing economic importance of NTFPs in our region can only be inferred from ethnobotanical studies (Lange 1998; Font Quer 1961). Conservation and commercial efforts As for goals regarding commercial activities and profitability, P. avium is the most suitable species. Not only does it provide timber that has a high market value and is in high demand, it also produces some important NTFPs, such as scented honey, medicinal substances and fruit. Since this is the case, it clearly should be proposed for a germplasm management plan with the aim of increasing both its timber quality and productivity. Therefore, a project to survey, collect and breed selected trees should be started, and approved seed orchards for seedling production and commercial production orchards should be estab-
lished. The logging of its timber should be strictly monitored and controlled in the entire region, especially in those areas with higher growth densities (Sierra Nevada and Sierra de Aracena). The same type of collecting, evaluating and breeding programs should be applied to both the cultivars and naturalized varieties of P. avium and P. insititia. The setting up of a collection of P. avium for the ´ cultivation of local cultivars in the Sierra Magina RNA and the Sierra de Aracena and Picos de Aroche RNA will undoubtedly be useful in order to avoid the imminent loss of old varieties, which are already disappearing, as they are rapidly being replaced by modern, more productive varieties. Local cultivars of the P. domestica-P. insititia complex should be collected in the Sierra Nevada National Park and the ´ Sierra Magina RNA, where they were locally used as rootstocks and as minor fruit trees. Some of them still do occur, scattered over old, abandoned plots on these mountains ranges. P. mahaleb has the potential to produce quality wood (for musical instruments, pipes and small carved objects), so selected seed stands could be set up in the Sierra de Grazalema RNA, the ´ Sierra Magina RNA and in the Sierras de Cazorla, Segura and las Villas RNA. For P. ramburii, its most important potential uses are as a slope retainer and in reforestation schemes. Since it is a species that is well adapted to the Mediterranean climate and soil, and since it produces an extensive root system, it is perfectly suitable for plantings designed to prevent erosion caused by rainfall on mountain slopes and for revegetation programs on arid and deforested ranges, such as Sierra de Baza ´ and Sierra de Gador. Depending on whether it becomes commercially profitable to use its fruit for beverages, a program to control fruit harvesting and to avoid allochthonous introductions (P. spinosa) may be necessary, especially in Sierra Nevada. Until another certification system is applied in the region, all Prunus germplasm, as well as other forest products from the region, will need a ‘certificate of origin’, issued by the regional Environmental Agency ´ de Medio Ambiente). This certificate (Consejerıa guarantees the origin, purity and sanitary conditions of seeds and germplasm from Andalusia. It seems that a preliminary Seed Zones Map has recently been issued for Spain, though it has not yet been published. Guideline 6: Scientific research to be done regarding the botany, wood quality improvement, nontimber forest products and rootstocks properties of Prunus species. Though no scientific research in germplasm evalua-
13 tion and breeding programs was done during recent decades for most of the minor broadleaf tree species in Spain, several current projects address these issues, though they are mainly being conducted in northern Spain (Puertas and Traver 1997; Traver et al. 1997; Vega 1996). They target P. avium as the most interesting species, for its potential and the revenues it can produce. In several EU countries, similar breeding projects are being developed for P. avium (Department of Forest Genetics of SLU in Sweden, INRA in France, and in Germany). In Spain, and primarily in Andalusia, further research in Prunus germplasm should target the following topics: a) genetic variation studies of Prunus species using modern tools (such as molecular markers) should be undertaken in order to improve our knowledge of the genetic structure of populations, help to better target conservation efforts and monitor the consequences of management plans; b) the delineation of climatic breeding zones, for Prunus and all forestry species; c) taxonomic studies of the P. domestica-P. x fruticans-P. insititia complex; d) the survey, collection and description (using IPGRI descriptors) of cultivars and other naturalized material of P. avium, P. mahaleb and P. insititia in several of the mountain ranges in Andalusia. No species is severely endangered either locally or globally in the area, so the conservation of local Prunus cultivars that still survive should be the priority since they are disappearing on a daily basis. The genetic studies proposed may have a number of practical applications for the conservation of Prunus species, applications that will differ depending upon the Prunus sub-group to be implemented in. In the wild-naturalized-cultivated genetic pool of P. avium and P. insititia, different populations (those mentioned in the paper) could be evaluated so as to determine their indigenous character. Besides, in the undoubtful indigenous species (P. mahaleb, P. ramburii and P. spinosa) intraand inter-population variability can be assessed and used to soundly ellaborate management plans for germplasm conservation in the region.
important in P. avium, which has a considerable gene pool in the region. Both P. avium and P. mahaleb have a great future as minor hardwood species. These efforts will enhance public awareness, promote resource management and launch silvicultural practices aimed at the conservation of every Prunus species in Andalusia. a) Conservation efforts should target the best populations (of more than 20 individuals for P. avium and P. insititia and more than 50 individuals of P. mahaleb and P. spinosa), but the special conditions and the importance in the region of the first two species, oblige us to address all individuals, including the wild trees and local cultivars. b) The awareness of the importance of Prunus germplasm should be increased among forest workers, environmental managers and the public. c) For wild P. avium and P. insititia trees suffering introgression from domesticated material, highly diverse material coming from selected seed orchards should be planted in order to conserve the native wild genes among the natural populations. d) With the aim of enhancing Prunus conservation, some silvicultural techniques are proposed, such as mixed Prunus patches, hedge treatment, Z-tree selection at the early stages and the protection of root suckers. e) P. avium and P. mahaleb can be cultivated as high value timber trees. In this case, improved and selected germplasm should be used at highly productive sites. Other Prunus species can provide some profitable NTFPs. f) The main research to be done in the coming years is the evaluation and collection of the germplasm of those species with greater economic importance, in order to avoid, or at least mitigate, the rapid loss of cultivars and the wild gene pool. No Prunus species is locally threatened in Andalusia at present. Finally, we consider that global germplasm conservation schemes can provide a cost-effective way of safeguarding the valuable genetic resources of Andalusian Prunus species. Other programs that are more species-focused would be very expensive and therefore not affordable for the regional government.
Conclusions So far, the Prunus germplasm of Andalusia has neither been properly assessed nor collected. Thus, some management and conservation guidelines need to be implemented in order to avoid the genetic erosion and extinction of wild germplasm and of many local cultivars. Genetic erosion is especially
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