GEOÖKO VOLUME/BAND XXXI, 28-49 GÖTTINGERN 2010
FOREST STRUCTURES OF THE JUAN FERNANDEZ ISLANDS, CHILE: SIGNIFICANCE FOR BIRD COMMUNITY AND CONSERVATION
INGO HAHN, PABLO VERGARA & UWE RÖMER
ZUSAMMENFASSUNG
Drei Grundtypen der Waldstruktur werden auf dem Juan Fernandez-Archipel identifiziert und analysiert: Kulturwald/Forst der basalen Stufe, nativer Wald der montanen Stufe und nativer Baumfarn-Wald der subalpinen Stufe. Für den Kulturwald/Forst auf Robinson Crusoe sind die eingeschleppten Eucalyptus und Cupressus charakteristisch. Der montane Wald wird durch endemische Myrtenbäume der Gattung Myrceugenia auf beiden Hauptinseln dominiert. Der subalpine Baumfarnwald ist durch ein Mosaik der Gattungen Dicksonia und Drimys auf die Insel Alejandro Selkirk beschränkt, denn auf Robinson Crusoe wird diese Höhenstufen nicht erreicht. Die strukturellen Parameter divergieren stark sowohl zwischen autochthonen und allochthonen Waldtypen als auch zwischen autochthonen Wäldern unterschiedlicher Höhenstufen. Der montane Wald auf Robinson Crusoe und Alejandro Selkirk zeigt ähnliche strukturelle Muster, aber die Bestände auf Selkirk sind stärker verinselt und artenärmer. Die deutlichen strukturellen Unterschiede der analysierten Waldtypen spiegeln sich in der Vogeldiversität und -dichte wider. Native Wälder bevorteilen ein gleichmäßigeres Vorkommen von Arten und liefern einen diverseren Vogellebensraum; Kulturwälder/Forste können nur für einzelne heimische Vogelarten aufgrund bestimmter ökologischer Gegebenheiten von Bedeutung sein. Endemische Vögel hängen hochgradig von nativen Waldstrukturen ab, weil sie angepasst sind an spezifische Muster der Nahrungssuche, der Nistplatzwahl und des Schutzes von Fressfeinden. Anthropogen verursachte Zerstörung solch nativer Waldstrukturen hat mehrere Vogelarten an den Rand des Aussterbens gebracht. Naturschutz-Management muss die Wiederherstellung des gesamten Inselökosystem zum Ziel haben, beginnend mit Ausrottungsprogrammen für die eingeschleppten Säugetiere.
Schlüsselworte: gefährdete Endemiten, Inselökologie, Pflanze-Tier-Interaktionen, Naturschutz, Ökosystem-Management, Vogelanpassung.
SUMMARY
Three principal forest structure types were identified and analysed on the Juan Fernandez Archipelago: cultivated forest of the basal region, native montane forest, and native sub-
28 alpine tree-fern forest. In the cultivated forest of Robinson Crusoe the introduced Eucalyptus and Cupressus are characteristic. The montane forest is dominated by endemic myrtle trees Myrceugenia and found on both major islands. The sub-alpine tree-fern forest is a Dicksonia- Drimys mosaic restricted to Alejandro Selkirk. Structural parameters between autochthonous and allochthonous forest types diverge strongly as well as between autochthonous forests of different altitude levels. The montane forests of Robinson Crusoe and Alejandro Selkirk show similar structural patterns, but stands are more scattered and species-poor on Selkirk. The clear structural differences between the analysed forest structures are reflected in bird diversity and abundance. Native forests favour a more equal occurrence of species and prepare a more diverse bird habitat; cultivated forests may be of importance for single species in regard to a specific ecological feature. Endemic birds highly depend on native forest structures, as they are adapted to specific patterns of forage, nest site, and shelter from predation. Human-related destruction of such native forest structures has brought several bird species close to extinction. Conservation management should restore the island ecosystem, starting with an eradication program of the introduced herbivores.
Keywords: animal-plant interaction, bird adaptation, ecosystem management, island ecology, nature conservation, threatened endemics.
1 INTRODUCTION
The structure of forests generally depends on the plant species present and the environmental impacts (Korpel 1995, Haberle 2003, Stuessy et al. 2005). In turn, forest structures have been identified to be a decisive factor for the presence of a certain animal community or occurrence of a specific bird species (e.g. Mattes 1988). On the Juan Fernandez Islands birds are the sole native land vertebrates, and the only animal group yet investigated in regard to its community ecology (Hahn et al. 2005, 2009). However, several of the endemic bird species are critically endangered and about to disappear from the community. According to King (1980, 1985), Simberloff (1978), and Wiens (1994) the main reason for extinction in island birds is the destruction and degradation of vegetation. Besides the bird community, a great number of other plant and animal species directly depends on the specifity of forest. Thus, the presentation of detailed forest structure patterns would enable a comparison of the demands of endemic birds, helping to identify significances for the community, and finally provide a basis for conservation management (Ricci 2006, comp. also Gerold & Markussen 2007). Skottsberg (1953) has given a provisory but comprehensive description of plant communities, including the first data on height and coverage of several of the archipelago’s forests. However, since his field studies in the years 1916 to 1918 introduced numerous species invaded forests, changed plant composition and structure, or even formed complete allochthonous stands. In the second half of the last century further aspects of forest ecology or selected units have been the matter of investigation (Kunkel 1956, Schwaar 1979, Stuessy
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1992, Stuessy & Ono 1998), and advances in description and classification of the FLORA FERNANDEZIANA were made (Marticorena et al 1998, Bernadello et al 2006, Baeza et al. 2007, Wheeler 2007). In the year 2002 Greimler et al. (2002a) presented a detailed description of vegetation distribution on Robinson Crusoe Island (comp. also Moreira-Muñoz 2007). However, all these valuable surveys did not prepare recent information on structural patterns: and from the ornithological view specific scales not congruent with the present results derived from botanical methodology are favourable. The main question of this survey is: Which forest structures exist on the Juan Fernandez Islands, and which importance do they have for endemic versus invasive landbirds? No such investigations yet exist, but it can be hypothesised that endemic landbirds are more bound to native forest structures on islands than invasive landbirds. Therefore a comparative avifauna-focussed analysis of the forest environments of the Juan Fernandez Archipelago is aimed at, combining methodological approaches and data from vegetation structure research, phyto-coenology, and ornithology.
2 METHODS
The Juan Fernández Archipelago is of volcanic origin and situated in the south-east Pacific Ocean off the coast of Chile (33° 28' 48'' S to 33° 47' 57'' S and 78° 47' 12'' W to 80° 47' 44'' W). It consists of the islands Robinson Crusoe (formerly Másatierra), Alejandro Selkirk (formerly Másafuera), Santa Clara, and some small rocks (Fig. 1). The easternmost Robinson Crusoe (47.11 km², 915 m high) is located 567 km away from the continent, the westernmost Alejandro Selkirk (44.64 km², 1320 m) another 167 km west of Robinson Crusoe, the smaller Santa Clara (2.23 km², 375 m) only 1.5 km south-west of Robinson Crusoe. The whole archipelago is a Chilean national park since 1935 and UNESCO Biosphere Reserve since 1977, except from the San Juan Bautista settlement. More detailed (bio)geographical descriptions may be taken from Castilla (1987), Skottsberg (1920-1956), and Stuessy & Ono (1998).
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Fig. 1. Geographical position of the Juan Fernandez Archipelago National Park and its single islands Alejandro Selkirk, Robinson Crusoe and Santa Clara in the south-eastern Pacific Ocean off mainland Chile. The cold Humboldt Current causes a similar temperate oceanic climate in the islands like in southern Chile between 38° and 41° S latitude.
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From 1992 to 2009 five field campaigns were carried out to study the ecology of the Juan Fernández Archipelago. All three major islands were visited during a total of 315 days. Composition and distribution of vegetation types may be compared to Skottsberg (1953), Greimler et al. (2002a), Hahn et al. (2005), and Hahn (2006). Forest structures are described on the base of structural vegetation analyses. These were made by measuring any plant individual in regard to its position, height, thickness of the stem, and crown extension to the directions within a sample plot. Data registration was completed by drawing rough sketches and taking photo shots. Field data then were transferred drawing on millimetre scaled paper. To also document the entire plant species composition in selected sample plots, vegetation relevees were carried out using the method of Braun-Blanquet (1964). These relevees were useful for comparisons to the results of Greimler et al. (2002a) as well as Skottsberg (1953), the latter following the Swedish school. Completing tabular data of species name, stem diameter, storey coverage, and height are given in the appendices.
3 RESULTS
3.1 FOREST STRUCTURE ANALYSES
Principally the forests can be distinguished between types of the islands Robinson Crusoe and Alejandro Selkirk as well as between allochthonous and autochthonous types. Native forests once covered major parts of both these islands, as illustrated and reported from the 17th and 18th century (e.g. Walter & Robins 1748, comp. Danton et al. 1999). Through man-made fires, selective cutting, impact of introduced herbivores, and competition by alien tree species their range declined to actually about 12 % of the archipelago’s superficies (Hahn 2006). As Robinson Crusoe became the place of a small continuous settlement from 1850 on, it was frequented more often by sailors and received a higher number of invasive species than Alejandro Selkirk (comp. Greimler et al. 2002b). Photo documents by Skottsberg (1956) show that the settlement surroundings were free of any forests in 1918, probably as the native trees already had been cut and the vegetation then had been kept low by domestic herbivores. However, in 1935 the island was declared a national park and locals were not allowed to exploit native trees any longer. To cover the need for fire wood and constructive material, cultivated forests were planted: Eucalyptus globulus, Cupressus macrocarpa, Pinus radiata and Albizzia lophantha became frequent and now form a belt around the San Juan Bautista village. To document the cultivated forest of the basal region near the settlement, a structure analysis within a sample plot of a typical young (30-40 years) Eucalyptus-Cupressus stand was carried out (Fig. 2). For its floristic composition one may refer to vegetation relevee 10 (app. a).
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Fig. 2. Structure analysis of a cultivated forest in the basal region of Isla Robinson Crusoe. This allochthonous Eucalyptus-Cupressus stand was located in an island-like forest at the Plazoleta del Yunque at 220 m above sea level. Further structure and site data are given in the appendices a (relevee 10) and c.
In this typical stand two tree storeys are distinguished: the upper is exclusively formed by Eucalyptus globulus, with their canopies ranging from about 10 m to a maximum of 26 m high. The lower tree storey is formed by Cupressus macrocarpa and young Eucalyptus globulus reaching a maximum height of 12 m; Aristotelia chilensis occurs only locally and not growing higher than 8 m. The long lower branches of the cypresses reach down to 1.5 m above the surface and have grown into cover gaps of more intensive sun light (Fig. 2: e.g. trees 3 and 6). The numbers of single tree individuals correspond to the running numbers of the appendix. 33
Fig. 3. Structure analysis of the autochthonous forest in the lower montane region of Isla Robinson Crusoe. This forest stand is located in Valley Anson at 320 m above sea level. Further structure and site data are given in the appendices a (relevee 3) and c.
In spite of the human impact, the montane forest on Robinson Crusoe survived in the central regions, although allochthonously influenced in some areas. Its spatial and altitudinal range allows to distinguish in a lower and an upper forest level (Greimler et al. 2002a, Skottsberg 1953), the lower being tall-trunked with a dense canopy and the moister upper part including many ferns. Fagara mayu has its main occurrence in the lower forest level, whereas the number (and coverage) of Drimys confertifolia is increasing towards the upper level. The Chonta Juania australis is very scattered in lower altitudes and more abundant only above 500 m. In the autochthonous forest of the lower montane region a structure analysis in a sample plot was carried out (Fig. 3). The stand belongs to the Myrceugenia-Drimys association of Robinson Crusoe (comp. Skottsberg 1953).
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Fig. 4. Structure analysis of an autochthonous tree-fern forest in the sub-alpine region of Alejandro Selkirk Island. This Dicksonia externa-Drimys confertifolia stand is located in the southern half of the island at 1020 m above sea level. Further structure and site data are given in the appendices b (relevee 11) and c.
The plot site was chosen for the presence of all dominant tree species and the avifaunistic- relevant detail structures. The highly covering Drimys confertifolia and Fagara mayu of this stand are in the senescence stage. Only one tree storey is formed, above which the canopies are densely closing (90 %). The narrow-growing Myrceugenia fernandeziana breaks through the canopy storey only in gaps of these (Fig. 3: trees 3 and 18). In the shrub storey (here 0.5 – 2 m) and the above storey of 2 – 6 m height partly numerous upgrowth of M. fernandeziana is recognised. This is predominantly the case in areas downhill of dominant mature trees. These high upgrowth numbers at this site indicate the species’ high shade tolerance. Contrarily upgrowth of Drimys confertifolia and Fagara mayu were rarely recognised within closed forest stands, but young D. confertifolia were frequent where a stand had entered the breakdown stage.
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The montane forest of Alejandro Selkirk has suffered severe fires and therefore is only present in small scattered relict patches. In drier island regions, like in the north-east, the endemic congener Myrceugenia schulzei still builds mono-species stands, showing very similar habits. Upgrowth is here completely absent, as feral goats inhibit any regeneration. A significant natural difference between the two major islands is the higher altitude of Alejandro Selkirk, and along with this the appearance of sub-alpine and alpine vegetation levels (comp. Zeiss & Hermosilla 1970). The sub-alpine level is characterised by moist and cold climate, hosting autochthonous tree-fern forests. Like in figure 4, Dicksonia externa always shows a high coverage in this forest type; at numerous sites it is mixed with single trees or groups of Drimys confertifolia.
The “tree islands” formed by Drimys confertifolia reach a maximum height of 5 m (Fig. 4, tree 9) at 1020 m altitude; their canopies close very tight with those of the tree-ferns. Dicksonia externa may reach a height of up to 4 m (Fig. 4, e.g. tree-fern 23) or more in the brook beds. However, it mostly forms its own 1.2 to 2 m high tree-fern storey. At sites without Drimys confertifolia (app. b, relevees 13-15) the tree-ferns grow densely. Specimens of the mostly stem-less fern Lophosoria quadripinnata (Fig. 4, ferns 38-41) become more abundant with increasing altitude; in the analysed plot they are restricted to border areas of the Drimys canopies. The dense cover of the tree-fern forest allows only very little undergrowth, thus the surface is dominated by the reddish-brown litter of fallen fern fronds.
3.2 Birds in forest structures
In the sample plot of the cultivated forest of the basal region (Fig. 2) the hummingbirds Sephanoides fernandensis (endemic) and S. sephaniodes (invasive) were regularly observed, the tyrant Anairetes fernandezianus (endemic) and the thrush Turdus falcklandii magellanicus (invasive) only occasionally. These four bird species represent the only forest birds present on Robinson Crusoe Island (see Fig. 5). The importance of this allochthonous forest type derives from flowering Eucalyptus globulus: several hummingbirds regularly feed on these nectar- rich sources and have established their territories. Hummingbirds also feed on the pollen of the cypresses: they were seen flying along the horizontal branches (comp. Fig. 2, e.g. tree 6), sucking the pollen with their long tubular tongue, and raising up much other. Contrarily, this forest is of minor importance for the insectivorous tyrant and the mainly frugivorous thrush, as arthropods find limited life conditions and berries are bound to the Aristotelia chilensis specimens. Cypress structures are also suitable for the construction of bird nests: the ornithologist F. Johow (pers. comm. 2003) localised one Sephanoides fernandensis nest attached to a thin twig in c.7 m height in 2002 and IH one Turdus falcklandii magellanicus nest in a forked branch at 4.0 m in 1994.
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Fig. 5. Forest bird species of the Juan Fernandez Archipelago. Top left and centre: Male and female of the endemic Juan Fernandez Firecrown Sephanoides fernandensis (with visible sexual dichromatism); Top right: invasive Green-backed Firecrown Sephanoides sephaniodes while breeding (white eye dot characteristic); bottom left: endemic Juan Fernandez Tit-tyrant Anairetes fernandezianus; bottom centre: invasive Austral Thrush Turdus falcklandii magellanicus; bottom right: endemic Masafuera Rayadito Aphrastura masafuerae. The firecrowns and the tit-tyrant occur on Robinson Crusoe, the rayadito on Alejandro Selkirk, and the thrush on both islands. All photos by the authors.
In the native forests of the montane regions the same four bird species were registered, but common. Structures provide more arthropod prey and hummingbird flowers for feeding than those of any other habitat on Robinson Crusoe. The tyrants are foraging in the canopy storey, in pairs or groups, acrobatically flying and hopping through the branches, searching on twigs and leaf for prey. For the hummingbirds, these native forests are the place of forage and nesting. At Rhaphithamnus venustus (e.g. Fig. 3, tree 13) flying insects were captured and nectar sucked off the flowers. Numerous nests of Sephanoides fernandensis and S. sephaniodes were found in the vicinity of this sample plot. Both construct their nests at the tips of thin flexible twigs of young Myrceugenia fernandeziana, but S. fernandensis higher
37 above the surface (3.5 - 5 m and more) and S. sephaniodes lower (normally 2-3 m). They use fine fern fibre, mosses, and few Myrceugenia leaves as nesting material. S. fernandensis also integrate white spider nets. Turdus falcklandii magellanicus is foraging in these forests less frequent than in allochthonous habitats, but predominantly prefers the forest structures for breeding: 14 out of 16 nests (Hahn unpubl. data) were located 3-6 m high in forks of the main stems of young Myrceugenia fernandeziana, similar to the trees 1 and 5 in figure 3.
The autochthonous forest of the montane region of Alejandro Selkirk is “frighteningly quiet”. The hawk Buteo polyosoma exsul and Turdus falcklandii magellanicus frequent its canopy cover only occasionally for perching. Both species have been registered similarly in the autochthonous tree-fern forest of the sub-alpine region, but the other three bird species are lacking from Alejandro Selkirk. Selkirk’s montane forest is only inhabited by the endemic rayadito Aphrastura masafuerae at higher sites: the rayadito was continuously recorded above 800 m altitude, but was nearly completely absent below. It forages on Drimys confertifolia und Dicksonia externa for arthropod prey, creeper-like running up the trunks and tit-like moving on fronds and twigs through the stand, sometimes hanging up-side down. All trunks, branches and twigs of Drimys are covered with epiphytes in this altitude, like mosses, lichens, and Hymenophyllaceae. The rayadito was observed searching in these structures systematically and preying on various arthropods. Its absence in the montane forest and from altitudes below 800 m may not be linked directly to vegetation structure, but more likely on food dependency and population parameters. As its population size recently has decreased to about only 140 specimens (Hahn et al. 2004) habitats of lower suitability may stay unoccupied.
4 DISCUSSION
The clear structural differences between the three analysed forest types derive from the tree species’ habits and the geographical site conditions. A comparison of the two principal forest types from Robinson Crusoe shows that the native stand is structurally richer than the cultivated one, on the macro as well as on the micro scale. Endemic birds were generally favoured in the native forest: their movement and behaviour patterns appear to be possible in such structures only. Additionally the dense canopy cover of montane and sub-alpine forest types shelters the small endemic birds from raptor attacks. Field observations show that Anairetes fernandezianus and Aphrastura masafuerae may become victims of the aerial predators Falco sparverius fernandensis and Buteo polyosoma exsul respectively, when they are leaving the protective native vegetation (Hahn et al. 2004, Hahn 2006). Presumably therefore A. masafuerae leave this shelter only in case of exception, are generally absent from areas with anthropogenic impact or areas split up in patches. Thus an intact native tree-fern forest is the essential basis for its occurrence; in turn, the small area still showing these structural characters may be the reason for its low numbers and high degree of threat (comp. IUCN 2010). 38
The flower agglomerations of the native hummingbird-pollinated plants are suitable for the endemic Sephanoides fernandensis, as they are sufficiently concentrated to enable feeding territories (comp. Colwell 1989). Contrarily, distributions of allochthonous flowers, like those of Aristotelia chilensis and Rubus ulmifolius, are much more decentralised, and therefore favour the invasive S. sephaniodes; this bird is more mobile than S. fernandensis at these flowers but sub-dominant in establishing territories. However, the flowers of Eucalyptus globulus represent an exception, as they are more efficiently used by S. fernandensis in spite of their dense agglomerations. This may be an exemplary case of an introduced tree being of high importance to an endangered endemic bird.
In turn, the trochiliphilous plants depend on the hummingbirds. This important role of pollinating native plants is given evidence on Alejandro Selkirk: the endemic hummingbird Sephanoides fernandensis leyboldi was last seen in 1908 by the Swedish botanist Skottsberg (Skottsberg 1956, Johow 2003), and now stated to be extinct. The island’s trochiliphilous plants are lacking their principal pollinator. Nowadays only few such plants persist, which in turn might be the reason why the recently immigrated S. sephaniodes were unable to establish a permanent population on Alejandro Selkirk (Hahn et al. 2009).
The density and habitat use pattern shown by endemic and invasive landbirds confirms the general hypothesis. In relation to the overall populations of the investigated landbirds (comp. also Hahn et al. 2005, 2006), the endemics were more bound to native (forests) stands, and the invasive birds were more evenly spread over all present habitat types. This corresponds to assumptions derived from habitat selection theory of mainland generalist species (Fretwell & Lucas 1970, Latta & Faaborg 2002, Chen et al. 2008). The more evenly distributed invaders, namely S. sephaniodes and T. falcklandii, prefer degraded habitats what identifies them as habitat generalists, an attribute which had made them becoming similarly successful and widespread on the mainland (Johnson 1965, 1967, Vergara & Armesto 2009). Although endemic landbirds might increase their populations or distribution area after anthropogenic habitat change (Carty et al. 2000, Trainor 2007), this was not the case for Robinson Crusoe’s endemics because they are forest specialists, showing a clear habitat preference for the native relict forests.
Endemic species used perturbed habitats little, probably due to their evolved morphological and behavioral attributes making them specialized in using native forest structures, as suggested for oceanic landbird species (e.g. Blondel 2000). In addition, exotic scrub stands probably offer few resources (e.g., nectar and insects) for endemics and are often exposed to strong winds. Although not assessed in this study, perturbed habitats also may act as barriers for endemic species, reducing the connectivity between native forest patches.
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The connective investigation of forest structures and bird adaptations gives evidence that applied conservation activities must focus on the entire archipelago’s ecosystem. Existing forests should be preserved and strictly protected from any severe anthropogenic activity. New alien immigrations (comp. Cuevas & Le Quesne 2006, Fernández & Sáiz 2007, Sol et al. 2008) and man-made fires (last in 2001; comp. also Dierböck et al. 2003, Haberle 2003) have to be inhibited and sanctioned, otherwise exotic scrubs and grasslands will become even more abundant. Areas formerly covered by native forests should be re-forested by clearing any substitutive vegetation and planting native tree species. However, prior to this all introduced mammals have to be eradicated, starting with goats on Alejandro Selkirk and cattle and cats on Robinson Crusoe. If domestic cats are removed from the settlement on Robinson Crusoe, the endemic hummingbird population will surely increase, and in turn would support the pollination and growth of native plant species. Thus, goat and cat eradication would not only have a direct positive effect on native vegetation structures, but also prevent the extinction of Chile’s two most threatened and critically endangered bird species: the Masafuera Rayadito and the Juan Fernandez Firecrown.
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APPENDIX: TABULAR NOTES TO THE STRUCTURE ILLUSTRATIONS OF THE FIGURES 1-3.
The three sample plot sites of the structure analyses (Fig. 1-3) and their plant specimens are described through additional data: location, incline, species names, specimen numbers, height (m), and stem diameter (cm). The latter was taken in 1.5 m height (Fig. 1 & 2) and in 0.3 m (Fig. 3).
Tab. 1: Plant specimens in a 25 x 5 m (125 m²) plot on the natural platform of the Plazoleta del Yunque (Anson Valley, Juan Fernandez Islands, Chile, 220 m altitude; see Fig. 1), . near to the stone fundament of Hugo Weber’s house. Direction: from West (100°) to East (280°), exposed to the west (280°); average slope = 8° (18 %).
Number Species name Stem diameter (cm) Height (m) 1. Eucalyptus globulus 22.0 18 2. Eucalyptus globulus 36.0 24 3. Cupressus macrocarpa 23.8 10 4. Eucalyptus globulus 27.8 23 5. Cupressus macrocarpa 7.4 6.5 6. Cupressus macrocarpa 22.2 12 7. Eucalyptus globulus 15.0 12 8. Cupressus macrocarpa 9.2 8 9. Eucalyptus globulus 46.2 26 10. Cupressus macrocarpa 12.0 9 11. Eucalyptus globulus 15.0 14 12. Cupressus macrocarpa 20.6 11 13. Eucalyptus globulus 33.4 21 14. Cupressus macrocarpa 13.6 9.5 15. Eucalyptus globulus 12.0 11 16. Aristotelia chilensis 6.4 5 17. Cupressus macrocarpa 12.4 7.5 18. Cupressus macrocarpa 24.2 11 19. Eucalyptus globulus 15.0 13 20. Eucalyptus globulus 10.8 10 21. Aristotelia chilensis 8.2 5.5 22. Aristotelia chilensis 6.6 5 23. Aristotelia chilensis 11.6 8 24. Eucalyptus globulus 47.4 23 25. Eucalyptus globulus 15.0 12 26. Aristotelia chilensis 8.2 6 27. (dead) Aristotelia chilensis 7.4 5
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Tab. 2: Plant specimens < 2.5 m height in a 25 x 5 m (125 m²) plot on the natural platform of the Plazoleta del Yunque (Anson Valley, Juan Fernandez Islands, Chile, 320 m altitude; see Fig. 2), 50 m south-west of the path directing to the El Yunque mountain. Direction: from south west (330°) to north-north-east (30°), exposed to north-north-east (30°); average slope = 8,5° (19 %).There was a natural tree-fell originated gap 50 m east of the plot. Upgrowth of 1 to 2.5 m height was illustrated in figure 2 in both perspectives, but not showing number and canopy extension (for visual reasons).
Number Species name Stem diameter (cm) Height (m) 1. Myrceugenia fernandeziana 4.8 6 2. (dead) Myrceugenia fernandeziana 4.4 6 3. Myrceugenia fernandeziana 48.8 15 4. Myrceugenia fernandeziana 2.6 3.5 5. Myrceugenia fernandeziana 4.4 5.5 6. Myrceugenia fernandeziana 3.2 4 7. Myrceugenia fernandeziana 2.8 4 8. Myrceugenia fernandeziana 3.2 2.5 9. Myrceugenia fernandeziana 2.2 3 10. Myrceugenia fernandeziana 2.8 4 11. Myrceugenia fernandeziana 2.2 3 12. Fagara mayu 16.2 12.5 13. Rhaphithamnus venustus 4.2 4 14. Myrceugenia fernandeziana 10.2 11.5 15. Myrceugenia fernandeziana 8.2 10 16. Drimys confertifolia 122.6 16.5 17. Myrceugenia fernandeziana 4.4 5.5 18. Myrceugenia fernandeziana 29.6 16 19. (dead) Myrceugenia fernandeziana 6.6 7 20. Myrceugenia fernandeziana 2.0 3 21. Myrceugenia fernandeziana 1.6 2.5 22. Myrceugenia fernandeziana 12.0 10.5 23. Myrceugenia fernandeziana 1.6 3 24. Myrceugenia fernandeziana 2.0 2.5 25. Myrceugenia fernandeziana 2.0 2. 5 26. Myrceugenia fernandeziana 27.0 12 27. Fagara mayu 96.4 16 28. Myrceugenia fernandeziana 8.2 8.5 29. Myrceugenia fernandeziana 1.6 2.5 30. Myrceugenia fernandeziana 20.6 15 31. (dead) Myrceugenia fernandeziana 11.2 4 32. Myrceugenia fernandeziana 2.0 2.5
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Tab. 3: Plant specimens in a 15 x 3 m (45 m²) plot on a saddle located 30 m south-east of the rock towers “Tres torres” (Juan Fernandez Islands, Chile, 1020 m altitude; see Fig. 3), 50 m north-west of the water place. Direction: from north-north-west (210°) to south-south-east (150°), exposed to south-south-east (150°); average slope = 14° (31 %).Only Dicksonia externa individuals are illustrated in figure 3 in both perspectives, which had already grown a stem.
Number Species name Stem diameter (cm) Height (m) 1. Dicksonia externa 12.8 1.30 2. Dicksonia externa 14.4 1.10 3. Dicksonia externa 12.8 1.60 4. Dicksonia externa 8.6 1.25 5. Dicksonia externa 7.6 0.80 6. Dicksonia externa 12.8 0.35 7. Dicksonia externa 12.8 0.55 8. Dicksonia externa 8.2 1.05 9. Drimys confertifolia 50 5 10. Dicksonia externa 9.6 0.95 11. Dicksonia externa 9.0 0.65 12. Dicksonia externa 17.8 2.65 13. Dicksonia externa 16.0 2.20 14. Dicksonia externa 9.8 0.70 15. Dicksonia externa 16.8 1.85 16. Drimys confertifolia 38 4.5 17. Dicksonia externa 17.6 2.40 18. Dicksonia externa 17.6 2.55 19. Dicksonia externa 19.8 3.90 20. Dicksonia externa 10.6 1.30 21. Dicksonia externa 7.6 0.35 22. Dicksonia externa 11.8 1.65 23. Dicksonia externa 13.4 3.45 24. Dicksonia externa 12.0 1.05 25. Dicksonia externa 13.4 2.00 26. Drimys confertifolia 58 4.5 27. Dicksonia externa 12.8 1.70 28. Dicksonia externa 9.8 0.85 29. Dicksonia externa 8.2 1.10 30. Dicksonia externa 10.2 0.75 31. Dicksonia externa 9.0 0.40 32. Dicksonia externa 13.4 0.35 33. Dicksonia externa 16.2 2.30 34. Dicksonia externa 9.6 0.50 35. Drimys confertifolia 43 4 36. Dicksonia externa 7.4 2.35 37. Dicksonia externa 8.0 1.65 38. Lophosoria quadripinnata (without stem) 1.55 39. Lophosoria quadripinnata (without stem) 1.60 40. Lophosoria quadripinnata (without stem) 0.90 41. Lophosoria quadripinnata (without stem) 0.50
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ACKNOWLEDGEMENTS
IN MEMORIAM:
First of all, we like to commemorate all islanders and local staff who lost their lives through the resent Tsunami of 27 February 2010. They all loved the unique nature of their remote place “Fernandensis”, and helped during our field studies in various kinds. The Chilean CONAF granted our island and national park work permissions: special thanks go to M. Galvez, J. Reyes, J. Mesa, G. Gonzalez, C. Diaz, I. Leiva, and the rangers Alfonso, Bernardo, Danilo, Esteban, Guillermo, Manuel, Nino, Oscar, Jorge, and Ramon. We thank also Rojas and López families on Juan Fernández for hospitality, especially Sra. Elsa Rojas Rivadeneira (†) for her excellent cooking. The scientists M. Fernández, R. Schlatter, H. Mattes, A. Vogel, and W. Beisenherz were valuable partners to discuss and/or comment parts of an earlier manuscript. Lillian Harris additionally revised the English writing. Two anonymous reviewers made valuable comments on the manuscript, and we like to thank them for a number of useful suggestions. The study was supported by DAAD, HUMBOLDT Foundation and FONDECYT 11080085. All research activities comply with the current laws of Chile.
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Anschrift der Autoren:
PD Dr. Ingo Hahn (Corresponding author) Biogeography and Landscape Ecology Res. Grou Institute of Landscape Ecology University of Münster Robert-Koch-Str. 28 D–48149 Münster Germany and Departamento de Ecología Pontificia Universidad Catolica de Chile Alameda 340, Casilla 114-D, Alameda 340, Santiago Chile [email protected]
Dr. Pablo Vergara Departamento de Ingeniería Geográfica Universidad de Santiago de Chile Av. Lib. B. O'Higgins 3363 P.C.: 7254758 Santiago Chile
PD Dr. Uwe Römer Institute of Biogeography University of Trier Am Wissenschaftspark 25-27 D-54296 Trier Germany
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