Aextoxicon Research Articles

Composition of Paleocene forests from Antarctica based on fossil wood

A new assemblage of fossil wood of Paleocene age from Seymour Island, Antarctic Peninsula, is described. Conifer species have been identified, belonging to the fossil genera Agathoxylon, Phyllocladoxylon, Protophyllocladoxylon, and Podocarpoxylon. Angiosperm fossil wood species are assigned to Nothofagoxylon, Caldcluvioxylon, and Myrceugenellites. New wood types have been described with possible affinity to Atherospermataceae and Asteraceae (daisy family). A newly identified fossil angiosperm species, Aextoxicoxylon jacksius, has been recorded from Antarctica for the first time. It shares traits with modern Aextoxicon punctatum and other Aextoxicoxylon wood from South America but is considered a separate species due to significant differences in vessel density, ray height, and frequency. This study indicates, in accordance with previous studies that conifers were the most common elements in the Paleocene Antarctic vegetation. In particular, Agathoxylon being the most dominant wood type. Nothofagoxylon was the most common angiosperm wood type. Overall the composition of the Antarctic Paleocene vegetation deduced from the presence of fossil wood resembles that of the modern warm to cool temperate forests of Tasmania, New Zealand and southern South America. Possible upland and lowland forest types have been identified, with the lowland forests likely most similar to the modern mixed cool temperate forests on South Island, New Zealand, and Tasmania. The upland forests were similar to the modern open canopy Araucaria-Nothofagus forests on the high Andes today.

Phylogeny of Berberidopsidales based on nuclear and chloroplast loci, with the description of a new species of Berberidopsis endemic to Central Chile

AbstractBerberidopsidales comprises two families: monotypic Aextoxicaceae (Aextoxicon punctatum in Chile and Argentina) and Berberidopsidaceae. The latter includes Australian monotypic Streptothamnus (S. moorei) and Berberidopsis (B. beckleri in Australia and B. corallina in Chile). A new Berberidopsis species from the Central Chilean Andes is here described. Phylogenetic analyses based on nuclear and chloroplast data clarified the relationships within Berberidopsidales. The new species, Berberidopsis granitica, is sister to the Chilean endemic B. corallina, and this clade is sister to the Australian B. beckleri. The dated molecular phylogeny places the split between the South American B. corallina and B. granitica into the late Miocene/early Pleistocene and the split between South American and Australian Berberidopsis to the late Miocene and Pliocene, suggesting transoceanic dispersal rather than vicariance. Climatic niche analyses show two distinct and non‐overlapping climatic niches for the Australian and southern South American species. Berberidopsis granitica and B. corallina also differ clearly in their habitat and morphology, in addition to their climatic niche. Berberidopsis granitica has a very restricted distribution area and grows in the Andes under montane climatic conditions, unique within Berberidopsidales.

Historia de la vegetación del sitio Huapilacuy II durante el Holoceno Medio a partir del análisis polínico y de macrofósiles vegetales, Isla Grande de Chiloé, Chile

This study examines the new fossiliferous site Huapilacuy II of Mid-Holocene age (7,344±51-6,865±58 cal years BP.) located in the northwestern coast of the Isla Grande de Chiloé. This area was not affected by the successive Pleistocene glaciations, and therefore it presents a biogeographic relevance as a potential area of refugia and stability for the vegetation. The presence of plant macrofossils contained in a sedimentary sequence of ca. 300 cm thick, confers a special interest to the site, due to the scarce information available on this type of indicator in paleoenvironmental studies of southern Chile. Additionally, several pollen-based reconstructions from the southern Lake District of Chile (40-44˚ S), document the Holocene sequence of recolonization by the different temperate rainforests types that today occupy this region, although there are non-Holocene records for the Pacific coast of the region. The aim of this study is to reconstruct the local environmental conditions and paleoecology based on the stratigraphic context and the analysis of plant macrofossils at the site Huapilacuy II. In addition, based on the pollen analysis of the deposit, we provide new information to reconstruct the regional characteristics of the vegetation during the Middle-Holocene. In particular, the plant macrofossil record of marsh species contained in the sediments of the lower section of the studied sedimentary sequence, together with the pollen analysis of the same sequence, document a first phase of plant colonization at 7,344±51 cal yrs. BP, with predominance of Poaceae, ferns, and trees with regeneration capacity in open areas, such as Embothrium coccineum and Drimys winteri. The analysis of leaf macrofossils and palynomorphs recovered from several intercalated layers, from the middle section of the sedimentary sequence, show the local and regional development of dense and very humid forests dominated by Aextoxicon punctatum, associated with several species of Myrtaceae. The presence of soil moisture indicator species, such as Luma chequen, Myrceugenia sp. and Myrtaceae Blepharocalyx-type is consistent with the sedimentary environment and the local development of swamp or riverine forests. This hygrophile forest environment is also consistent with the assemblage of fossil mosses, dominated by species that grow today in dense closed-canopy forests, such as Weymouthia, Ptychomnium, Rigodium, Porothamnium and Eucamptodon.
 The regional correlation of the pollen spectra from Huapilacuy II and other records from the Lake District allows us to establish latitudinal and longitudinal differences of tree composition in the temperate-rainforests that expanded during the Early to Mid-Holocene. In particular, this study established for the northwestern coast of the Isla Grande de Chiloé the presence of the coastal association of the valdivian forest (As. Lapagerio-Aextoxiconetum), currently distributed along the Chilean coastline between 30˚- 43˚S. In contrast, the Valdivian associations recorded in other areas of the region exhibit the dominance of Eucryphia cordifolia, Caldcluvia paniculata, Weinmannia trichosperma and different species of Nothofagus. Despite the differences in tree composition, the fossil bryophyte species recorded in several of the sites compared are common with those reported for Huapilacuy II, thus showing the wide ecological range of Chilean bryophytes associated with closed-canopy temperate-rainforests.

Restoring native forests from Pinus radiata plantations: Effects of different harvesting treatments on the performance of planted seedlings of temperate tree species in central Chile

Extensive areas of native vegetation have been cleared to establish commercial exotic tree plantations in south-central Chile, a region known as a world biodiversity hotspot. Despite increasing societal demands to restore native forests in parts of the landscape, documented experiences for this form of restoration are lacking. We conducted a landscape-replicated experiment to test the influence of different harvesting treatments (clearcut, strip-cutting and unharvested control) on the early establishment of native tree species in 20-year-old Pinus radiata plantations. Group plantings of shade-intolerant (Nothofagus dombeyi; Nothofagus obliqua), semi-tolerant (Nothofagus alpina; Laurelia sempervirens) and shade–tolerant species (Aextoxicon punctatum; Cryptocarya alba) were established across the treatments, and seedling performance and water status were monitored during the first two growing seasons. Mean survival was significantly higher in the strip-cuttings (77%) and control (70%) than in the clearcuts (38%), while mean height and root collar diameter growth were significantly higher in the strip-cuttings (16 cm year−1; 0.2 cm year−1) and clearcuts (16 cm year−1; 0.2 cm year−1) than in the control (5 cm year−1; 0.1 cm year−1). Shade-intolerant and semi-tolerant species showed the highest growth responses to openings. Leaf water potential was significantly higher in seedlings in the strip-cuttings than those in the control and clearcuts, and stomatal conductance was significantly higher in the strip-cuttings and clearcuts than in the control. Higher seedling performances and lower water stress in the strip-cutting treatment suggest that partial canopy removal is a suitable method for artificial regeneration of native tree species with different shade tolerances for native forest restoration from P. radiata plantations.

Genome Sequence of a Potentially New Buttiauxella Species, Strain B2, Isolated from Rhizosphere of Olivillo Trees (Aextoxicon punctatum).

We announce the draft genome sequence of strain B2, which belongs to a potentially new Buttiauxella species, isolated from soil associated with rhizosphere of olivillo trees (Aextoxicon punctatum). Its size is 4,967,099 bp, and its G+C content is 49.1%. The genome of strain B2 carries genes related to rhizobacteria that promote the growth of plants.

Mapeo y caracterización servicio ecosistémico de provisión y recreación en la cordillera de Nahuelbuta (37º30’’ - 38º00’’ Sur)

Los servicios ecosistémicos son los beneficios que las personas obtienen de los ecosistemas naturales. La caracterización y cuantificación de los servicios ecosistémicos contribuyen a la gestión sustentable de los recursos naturales. Los bosques son ecosistemas que otorgan múltiples servicios, entre los que se destacan servicios de provisión de productos forestales no maderables y servicios culturales de recreación. En este contexto el estudio se enfocó en el análisis y evaluación de los servicios ecosistémicos de la Cordillera de Nahuelbuta a través del mapeo y cuantificación de dichos servicios. Se analizó cómo influye el grado de naturalidad de las formaciones boscosas en la generación de estos servicios. Se estimó el stock de productos forestales no maderables concentrándose en frutos, semillas y hongos. Los resultados arrojan que el área alberga hasta 36 especies que proveen productos forestales no maderables en las formaciones boscosas de Bosque mixto templado de Nahuelbuta de Nothofagus dombeyi y N. obliqua y el Bosque laurifolio templado costero de Aextoxicon punctatum y Laurelia sempervirens. En relación al servicio de recreación se estimó un alto potencial de recreación y ecoturismo en la zona, en especial los sectores de Caramávida, Trongol y Parque Nacional Nahuelbuta los cuales presentan una adecuada combinación de atributos para la recreación tales como recursos singulares, belleza escénica, accesibilidad y capacidad de atracción turística. Los resultados revelan la necesidad de una urgente y adecuada protección de aquellas áreas núcleos en donde se concentra la mayor provisión de los servicios ecosistémicos analizados.

Shrub facilitation drives tree establishment in a semiarid fog‐dependent ecosystem

AbstractQuestionsThe exceptional occurrence of tall rain forest patches on foggy coastal mountaintops, surrounded by extensive xerophytic shrublands, suggests an important role of plant–plant interactions in the origin and persistence of these patches in semi‐arid Chile. We asked whether facilitation by shrubs can explain the growth and survival of rain forest tree species, and whether shrub effects depend on the identity of the shrub species itself, the drought tolerance of the tree species and the position of shrubs in regard to wind direction.LocationOpen area–shrubland–forest matrix, Fray Jorge Forest National Park, Chile.MethodsWe recorded survival after 12 years of a ~3600 tree saplings plantation (originally ~30‐cm tall individuals) of Aextoxicon punctatum, Myrceugenia correifolia and Drimys winteri placed outside forests, beneath the shrub Baccharis vernalis, and in open (shrub‐free) areas. We assessed the effects of neighbouring shrubs and soil humidity on survival and growth along a gradient related to the direction of fog movement.ResultsB. vernalis had a clear facilitative effect on tree establishment and survival since, after ~12 years, saplings only survived beneath the shrub canopy. Long‐term survival strongly depended on tree species identity, drought tolerance and position along the soil moisture gradient, with higher survival of A. punctatum (>35%) and M. correifolia (>14%) at sites on wind‐ and fog‐exposed shrubland areas. Sites occupied by the shrub Aristeguietia salvia were unsuitable for trees, presumably due to drier conditions than under B. vernalis.ConclusionsInteractions between shrubs and fog‐dependent tree species in dry areas revealed a strong, long‐lasting facilitation effect on planted tree's survival and growth. Shrubs acted as benefactors, providing sites suitable for tree growth. Sapling mortality in the shrubland interior was caused by lower soil moisture, the consequence of lower fog loads in the air and thus insufficient facilitation. While B. vernalis was a key ecosystem engineer (nurse) and intercepted fog water that dripped to trees planted underneath, drier sites with A. salvia were unsuitable for trees. Consequently, nurse effects related to water input are strongly site and species specific, with facilitation by shrubs providing a plausible explanation for the initiation of forest patches in this semi‐arid landscape.

Floral development of Berberidopsis beckleri - can an additional species of the Berberidopsidaceae add evidence to floral evolution in the core eudicots?

Berberidopsis beckleri is one of three species of the family Berberidopsidaceae. The flower of Berberidopsis is unusual for core eudicots in being spiral with an undifferentiated perianth. In a previous study of the sister species B. corallina , it was suggested that Berberidopsidaceae represent a prototype for the origin of the bipartite perianth and pentamery in core eudicots. The floral development of B. beckleri was investigated with a scanning electron microscope and compared with previous studies on B. corallina and Aextoxicon punctatum of Berberidopsidales. Flowers are inserted at the end of short shoots, which are not distinguishable from a pedicel. The initiation of perianth parts is highly predictable and spiral with a divergence angle of 137·5°, in a progression of a variable number of bracts to weakly differentiated sepaloid and petaloid tepals. The androecium most often consists 11 stamens arising in a rapid sequence. Compared with B. corallina , the number of perianth parts and stamens is more variable and there is no evidence of an alternation of shorter and longer plastochrons leading to a whorled arrangement. However, the gynoecium is generally pentamerous and arises from five primordia. The carpels are laterally connected into massive intercarpellary ridges on which ovules are initiated. The position of Streptothamnus within Berberidopsidaceae is questioned. It is demonstrated that the floral development of Berberidopsis beckleri lies within a gradient from spiral flowers without perianth differentiation leading to flowers with differentiated sepals and petals. The arrangement of flowers in compact inflorescences in B. corallina and Aextoxicon leads to a more stabilized arrangement of organs in whorls. The inherent variability of the flower of Berberidopsis is well correlated with the limited canalization of flowers in taxa at the base of the core eudicots and could act as a prototype for the current eudicot floral Bauplan.

Crecimiento anual de cuatro especies arbóreas con yemas desnudas nativas de los bosques templados húmedos de Patagonia.

Las especies vegetales que habitan en regiones con bajo nivel de estacionalidad en el clima suelen presentar rasgos morfo-arquitecturales que ocurren con menor frecuencia en especiesde regiones con clima estacional. El objetivo de este estudio fue evaluar el crecimiento primario en vivero de cuatro especies leñosas típicas de los bosques templados húmedos de Patagonia, conocidoscomo selva valdiviana, donde el grado de estacionalidad es menos marcado que en otros bosques patagónicos. Las especies estudiadas, Aextoxicon punctatum, Luma apiculata, Myrceugenia exsucca ySophora microphylla, comparten con muchas especies tropicales la posesión de yemas desnudas. Se evaluaron, durante un año calendario, la fenología, el crecimiento y la ramificación del eje principal de plantas marcadas. El crecimiento primario en estas especies fue marcadamente estacional, como en se ha registrado en especies arbóreas con yemas escamosas con las que coexisten. Sin embargo, se detectaron notables diferencias intra- e inter-específicas en el inicio y la finalización del crecimiento; L. apiculata y M. exsucca (Myrtaceae) presentaron mayores variaciones que las restantes dos especies.Nuestros resultados indican la intervención de varios factores reguladores del crecimiento primario en las especies estudiadas, como ocurre en especies con crecimiento continuo.

Environmental conditions shape soil bacterial community structure in a fragmented landscape

Several biogeographical hypotheses have been proposed to explain microbial distribution, but there is ongoing debate about the magnitude of the contribution of niche–based processes and historical contingencies in determining patterns of microbial structure. In this context, currently fragmented relict forests of olivillo (Aextoxicon punctatum Ruiz et. Pav.), which belonged to a continuous community along the coast of Chile during the Pleistocene, and their surrounding scrublands are ideally–suited for testing these hypotheses, since they remain as patches located at the northern tip of the distribution of the relicts. In each study site, edaphic and geographic variables were determined, and the bacterial structures were evaluated at the genetic and metabolic levels through fingerprint approaches along with multivariate analytical methods including redundancy (RDA) and variance partitioning (VPA) analyses. Forests possessed lower pH, and higher contents of moisture and organic matter. In addition, bacterial communities from both habitats differed, whereas the bacterial communities of the forests in different regions were very similar to each other. Our conclusion is that current abiotic soil factors, but not past events due to the historical connection of the forests, account for the variance in the structure of these soil bacterial communities.

The avifauna of Bosque Fray Jorge National Park and Chile's Norte Chico

The avifauna of Chile is relatively depauperate, comprising 469 extant species, of which 213 are terrestrial. However, the Coquimbo Region presents a broad ecological transition from the hyperarid Atacama Desert to the north, and the more mesic Chilean Mediterranean region of central Chile, resulting in relatively high species diversity. Approximately 130 species are found here, 8 of which are endemic to Chile although not to this region. Bosque Fray Jorge National Park is a 9959 ha Biosphere Reserve dominated by matorral habitat and hosting up to 123 bird species. Through avian surveys and banding over nearly a decade we have documented 63 terrestrial species and discerned predictable seasonal and interannual structure to avian assemblages, at least through an extended dry period. Recent studies in the matorral habitats of the park indicate seasonal patterns that fall into 4 patterns: year-round residents, winter visitors, summer breeders, and transients. Short-term banding studies demonstrate co-occurring wintering and breeding cohorts among species of Sierra-finches (Phrygilus) in the park; such assemblages and dynamics are reminiscent of North American Mediterranean avian assemblages and pose interesting ecological comparisons. In this period of surveys there appears to have been a gradual transition of the avifauna that may be a response to anthropogenic influence and/or climate change. Research on the foraging behavior of 2 insectivorous species indicate that one of these is convergent on better-known North American taxa while the other clearly is not; these efforts suggest useful avenues for further comparative research. A remarkable coevolutionary association between the Chilean Mockingbird (Mimus thenca) and endoparasitic mistletoes (Tristerix) provides insight into potential convergent ecologies in desert regions with different evolutionary histories.Less than 1% of the park comprises temperate forest remnants that subsist due to extensive water input from fog. Research in these remnants has emphasized the role of habitat fragmentation on avian assemblage composition and on reproductive ecology by forest-dependent species. The avifauna here comprises a subset of that found in intact Valdivian rainforest to the south, and forest remnant size alone explains over 90% of the variation in species numbers. One species has been particularly well studied; the Thorn-tailed Rayadito (Aphrastura spinicauda) is more abundant and has higher nestling survival in larger fragments. We summarize other work on stress responses and variation in song structure in this species. Finally, the role of birds in tree recruitment here has important implications in the face of a recent history of reduction in sizes of forest remnants; numerous birds consume the fruit of the dominant tree, olivillo (Aextoxicon punctatum), but they fail to promote successful recruitment because they defecate viable seeds in locations that provide poor survival of seedlings.Ornithological research in Chile is undergoing a modest renaissance, and while dryland avifaunas are characterized more by what is not known and has yet to be studied than by actual ecological understanding, they provide a baseline for many exciting studies ranging from natural history to the role of migration to comparative dynamics of independent lineages in North and South America.

Functional traits variation explains the distribution of Aextoxicon punctatum (Aextoxicaceae) in pronounced moisture gradients within fog-dependent forest fragments.

Climate change and fragmentation are major threats to world forests. Understanding how functional traits related to drought tolerance change across small-scale, pronounced moisture gradients in fragmented forests is important to predict species’ responses to these threats. In the case of Aextoxicon punctatum, a dominant canopy tree in fog-dependent rain forest patches in semiarid Chile, we explored how the magnitude, variability and correlation patterns of leaf and xylem vessel traits and hydraulic conductivity varied across soil moisture (SM) gradients established within and among forest patches of different size, which are associated with differences in tree establishment and mortality patterns. Leaf traits varied across soil-moisture gradients produced by fog interception. Trees growing at drier leeward edges showed higher leaf mass per area, trichome and stomatal density than trees from the wetter core and windward zones. In contrast, xylem vessel traits (vessels diameter and density) did not vary producing loss of hydraulic conductivity at drier leeward edges. We also detected higher levels of phenotypic integration and variability at leeward edges. The ability of A. punctatum to modify leaf traits in response to differences in SM availability established over short distances (<500 m) facilitates its persistence in contrasting microhabitats within forest patches. However, xylem anatomy showed limited plasticity, which increases cavitation risk at leeward edges. Greater patch fragmentation, together with fluctuations in irradiance and SM in small patches, could result in higher risk of drought-related tree mortality, with profound impacts on hydrological balances at the ecosystem scale.

Seabirds modify El Niño effects on tree growth in a southern Pacific island

Oceanic island ecosystems are particularly sensitive to El Niño effects due to their dependence on energy and nutrient inputs from marine systems. Seabirds play a key role in transporting resources of marine origin to insular ecosystems. We report tree-growth patterns showing how the effects of El Niño rainy events on tree species in a southern Pacific island depend on the presence of local seabird colonies. We performed manipulative experiments in order to assess the mechanisms underlying these patterns. Tree ring data showed that, in normal years, the growth of all tree species (Aextoxicon punctatum, Cryptocarya alba, and Pinus radiata) was significantly lower in seabird sites compared to adjacent patches without seabirds (control sites). In contrast, in El Niño years, trees formerly hosting seabird colonies grew more than those in control sites. Experiments showed that (1) pine plants on soil from seabird sites grew more than those on soil from control sites, (2) pine individuals with seabird feces on their leaves grew less than those sprayed with an aqueous solution, and (3) soil moisture had little effect on plant growth. The stress produced by massive cormorant nesting on trees, which impairs tree growth and physiological performance, is relieved during El Niño events because of seabird migration due to decreased prey availability and pouring rains that flood nests. Soils enriched by the seabird guano, together with the increased water availability associated with El Niño, foster the growth of trees from seabird sites. We suggest that El Niño may be a key determinant of tree performance in forest communities from island and coastal ecosystems of the Pacific Ocean.

Diverging drought-tolerance strategies explain tree species distribution along a fog-dependent moisture gradient in a temperate rain forest

The study of functional traits and physiological mechanisms determining species' drought tolerance is important for the prediction of their responses to climatic change. Fog-dependent forest patches in semiarid regions are a good study system with which to gain an understanding of species' responses to increasing aridity and patch fragmentation. Here we measured leaf and hydraulic traits for three dominant species with contrasting distributions within patches in relict, fog-dependent forests in semiarid Chile. In addition, we assessed pressure-volume curve parameters in trees growing at a dry leeward edge and wet patch core. We predicted species would display contrasting suites of traits according to local water availability: from one end favoring water conservation and reducing cavitation risk, and from the opposite end favoring photosynthetic and hydraulic efficiency. Consistent with our hypothesis, we identified a continuum of water use strategies explaining species distribution along a small-scale moisture gradient. Drimys winteri, a tree restricted to the humid core, showed traits allowing efficient water transport and high carbon gain; in contrast, Myrceugenia correifolia, a tree that occurs in the drier patch edges, exhibited traits promoting water conservation and lower gas exchange rates, as well low water potential at turgor loss point. The most widespread species, Aextoxicon punctatum, showed intermediate trait values. Osmotic compensatory mechanism was detected in M. correifolia, but not in A. punctatum. We show that partitioning of the pronounced soil moisture gradients from patch cores to leeward edges among tree species is driven by differential drought tolerance. Such differences indicate that trees have contrasting abilities to cope with future reductions in soil moisture.

737. AEXTOXICON PUNCTATUM

Aextoxicon punctatum Ruiz & Pavón, the olivillo, is a poisonous dioecious evergreen tree native to the sub-Antarctic forests of Chile and Argentina. Though introduced to cultivation during the late 1920s it has always remained rare. A tree of Aextoxicon punctatum is now fruiting at Kilmacurragh Botanic Gardens, Ireland. Details of the tree's habitat, ecology and its discovery and subsequent introduction are discussed.

Microsatellite markers for the relict tree Aextoxicon punctatum: The only species in the Chilean endemic family Aextoxicaceae

We screened 10 microsatellite loci for the dioecious, rainforest tree Aextoxicon punctatum, a species belonging to a monotypic family and genus, endemic to southwestern South America (30-43°S). Polymorphisms were evaluated in 108 adult trees from four populations, including the northern and southern extremes of the geographic range of Aextoxicon in Chile. All 10 microsatellites revealed polymorphic variation. A total of 69, 57, 59, and 69 alleles were found in 40 (Fray Jorge), 19 (Santa Ines), 21 (Quebrada del Tigre), and 28 (Guabun) individual trees, respectively. The mean expected heterozygosity per population ranged from 0.70 to 0.72. These polymorphic microsatellites will be useful in assessing the genetic structure and conservation status of Aextoxicon throughout its historically fragmented geographic range. Parentage analysis will provide additional insights into the key historical and contemporary processes that have mediated population differentiation in this species.

Floral Development and Anatomy of Aextoxicon punctatum (Aextoxicaceae‐Berberidopsidales): An Enigmatic Tree at the Base of Core Eudicots

Floral development and anatomy were investigated in the monotypic Aextoxicaceae (one species: Aextoxicon punctatum), one of two families of Berberidopsidales, to understand its putative relationship with Berberidopsidaceae and clarify floral evolution in basal core eudicots. Aextoxicon is dioecious, with unisexual flowers that display a late abortion of male and female organs in the respective genders. Flowers are pentamerous or hexamerous and are enclosed by a calyptra derived from the congenital fusion of two bracteoles. Initiation sequence and number of sepals, petals, and stamens are variable and mostly spiral, without clear transition between organ categories, and a single carpel initiates without evidence of a second carpel. The ovary contains two apical‐marginal ovules. Floral anatomical data suggest that the nectaries are receptacular in nature. Aextoxicon displays floral characters found in basal angiosperms, such as a unicarpellate gynoecium, an interrupted hoodlike outer integument, little diff...

Seedling Mortality and Herbivory Damage in Subtropical and Temperate Populations: Testing the Hypothesis of Higher Herbivore Pressure Toward the Tropics

ABSTRACTHerbivory rates are generally thought to be higher in tropical than in temperate forests. Nevertheless, tests of this biogeographic prediction by comparing a single plant species across a tropical‐temperate range are scarce. Here, we compare herbivore damage between subtropical and temperate populations of the evergreen tree Aextoxicon punctatum (Olivillo), distributed between 30° and 43° S along the Pacific margin of Chile. To assess the impact of herbivory on Olivillo seedlings, we set up 29 experimental plots, 1.5 × 3 m: 16 in forests of Fray Jorge National Park (subtropical latitude), and 13 in Guabún, Chiloé Island (temperate latitude). Half of each plot was fenced around with chicken wire, to exclude small mammals, and the other half was left unfenced. In each half of the plots we planted 16 seedlings of Olivillo in December 2003, with a total of 928 plants. Seedling survival, leaf production and herbivory by invertebrates were monitored over the next 16 mo. Small mammal herbivores killed ca 30 percent of seedlings in both sites. Nevertheless, invertebrate herbivory was greater in the temperate forest, thus contradicting the expected trend of increasing herbivore impact toward the tropics. Seedling growth was greater in subtropical forest suggesting better conditions for tree growth or that higher invertebrate herbivory depressed seedling growth in the temperate forest. Invertebrate herbivory increased toward temperate latitudes while small mammal herbivory was similar in both sites. We suggest that comparison of single species can be useful to test generalizations about latitudinal patterns and allow disentangling factors controlling herbivory patterns across communities.

Epiphyte diversity and biomass loads of canopy emergent trees in Chilean temperate rain forests: A neglected functional component

We document for the first time the epiphytic composition and biomass of canopy emergent trees from temperate, old-growth coastal rainforests of Chile (42°30′S). Through tree-climbing techniques, we accessed the crown of two large (c. 1 m trunk diameter, 25–30 m tall) individuals of Eucryphia cordifolia (Cunoniaceae) and one large Aextoxicon punctatum (Aextoxicaceae) to sample all epiphytes from the base to the treetop. Epiphytes, with the exception of the hemi-epiphytic tree Raukaua laetevirens (Araliaceae), were removed, weighed and subsamples dried to estimate total dry mass. We recorded 22 species of vascular epiphytes, and 22 genera of cryptogams, with at least 30 species of bryophytes, liverworts and lichens. The dominant vascular epiphytes were Fascicularia bicolor (Bromeliaceae), Raukaua laetevirens, Sarmienta repens (Gesneriaceae), and filmy ferns (Hymenophyllaceae). Epiphyte loads per tree ranged between 134 and 144 kg dry mass, with 60–70% water. The hemi-epiphytic tree R. laetevirens added between 1 and 2.6 t of dry mass to each host tree. A main component of epiphyte biomass, making 70% of the weight, was detritus and roots, while leaves, stems, and fronds made up the remaining 30%. Emergent trees hold a high proportion of the regional diversity of epiphytes: 33% of all flowering epiphytes, and 50% of all filmy ferns described for Chilean temperate forests. Dry epiphyte biomass associated only with the emergent E. cordifolia trees in coastal forests was estimated in 10 t/ha. Epiphyte biomass may store up to 300 l of water in each emergent tree, and add 40–150% of photosynthetic biomass to the tree crowns. Based on this evidence, epiphytes may play key but generally neglected roles in ecosystem carbon uptake, water storage, and nutrient cycling. Moreover, emergent trees represent nuclei of biodiversity and ecosystem functions distributed throughout mature forests. Forest management should recognize large trees as significant management units for the preservation of biodiversity and ecological functions.

BIOCHEMICAL PROPERTIES IN VASCULAR EPIPHYTES SUBSTRATE FROM A TEMPERATE FOREST OF CHILE

The temperate forests of south-central Chile belong to the association Lapageria aextoxiconetum Oberdorfer vegetation, dominated by Aextoxicon punctatum R. et P., elderly and multi-layered, where the strata are emergent, dominant and co-dominant, shrub and herbaceous epiphytes. This work is the first report of measurements of some biochemical properties in samples from vascular epiphytes substrate in temperate forests. We evaluated the most frequent ecological situations: bifurcated trees (BT), dead standing trees (SDT) and medium gap border trees (MGBT), ES were compared with the surrounding soil forest land (SS) as control. The microbial biomass and enzyme activities of substrate were higher in ES of BT, situation probably due to optimal micro-environmental conditions (moisture and humidity, temperature, organic matter (OM) content and nutrient availability); similarly, lower levels of activity were found in ES in MGBT situation. We found a statistically significant correlation (p ≤ 0.05) between evaluated microbial biomass and enzymatic activities. Furthermore, the biochemical properties were influenced by factors such as moisture, temperature, pH and OM content and all of these factors correlated significantly (P≤0.01) among them. These results demonstrate a difference between ES and SS in BT that should be explored to gain insights in understanding the processes of decomposition using the natural microcosms that ES provides.