Chilean Temperate Rainforests Research Articles

Climbing plants in a temperate rainforest understorey: searching for high light or coping with deep shade?

While the climbing habit allows vines to reach well-lit canopy areas with a minimum investment in support biomass, many of them have to survive under the dim understorey light during certain stages of their life cycle. But, if the growth/survival trade-off widely reported for trees hold for climbing plants, they cannot maximize both light-interception efficiency and shade avoidance (i.e. escaping from the understorey). The seven most important woody climbers occurring in a Chilean temperate evergreen rainforest were studied with the hypothesis that light-capture efficiency of climbers would be positively associated with their abundance in the understorey. Species abundance in the understorey was quantified from their relative frequency and density in field plots, the light environment was quantified by hemispherical photography, the photosynthetic response to light was measured with portable gas-exchange analyser, and the whole shoot light-interception efficiency and carbon gain was estimated with the 3-D computer model Y-plant. Species differed in specific leaf area, leaf mass fraction, above ground leaf area ratio, light-interception efficiency and potential carbon gain. Abundance of species in the understorey was related to whole shoot features but not to leaf level features such as specific leaf area. Potential carbon gain was inversely related to light-interception efficiency. Mutual shading among leaves within a shoot was very low (<20 %). The abundance of climbing plants in this southern rainforest understorey was directly related to their capacity to intercept light efficiently but not to their potential carbon gain. The most abundant climbers in this ecosystem match well with a shade-tolerance syndrome in contrast to the pioneer-like nature of climbers observed in tropical studies. The climbers studied seem to sacrifice high-light searching for coping with the dim understorey light.

Environmental and ecological architects: Guidelines for the Chilean temperate rainforest management derived from the monito del monte (Dromiciops gliroides) conservation

El cambio de uso de la tierra es una de las principales amenazas a la biodiversidad. Habitats naturales como el bosque templado lluvioso de Sudamerica han sido degradados, fragmentados y eliminados rapidamente. En consecuencia, es prioritario el manejo y conservacion de los remanentes, para lo que es necesario contar con una politica ambiental acorde. Las acciones de conservacion referentes al bosque lluvioso templado se han abordado mayormente desde una perspectiva de especies individuales, con poco enfasis en la conservacion a nivel de ecosistema. Mas aun, la informacion generada en este ambito tampoco ha permeado en el desarrollo de politicas ambientales. Utilizamos el estudio de caso del monito del monte (Dromiciops gliroides) para ilustrar como el conocimiento actual en ecologia y conservacion de una especie puede ser utilizado para generar una nueva politica ambiental. Dromiciops gliroides es una especie dependiente del bosque, con un importante rol ecologico y un gran interes evolutivo y de conservacion. Para garantizar su persistencia, proponemos dos componentes de gestion del habitat, a incorporarse en los planes de manejo: la estructura y la conectividad. La estructura hace referencia al arreglo espacial y la presencia de elementos estructurales clave que influyen en la calidad del habitat, mientras que conectividad se refiere a la conectividad funcional del paisaje. Conservando al monito del monte, se conservarian tambien otras especies dependientes del bosque y asi las interacciones ecologicas y los procesos ecoevolutivos, que determinan finalmente la conservacion del bosque lluvioso templado.

&lt;I&gt;Megalastrum&lt;/I&gt; (Dryopteridaceae) of the Circumaustral region: Chile, Argentina, and Southern Islands of the Atlantic, Pacific, and Indian Oceans

Abstract In this treatment we revise the circumaustral fern species of Megalastrum found primarily between 33–45° latitude South. These species are found in the Valdivian temperate rain forests of Chile and Argentina, the Juan Fernandez Islands in the South Pacific, the Tristan da Cunha archipelago in the southern Atlantic, and Ile Amsterdam and Ile Saint-Paul in the southern Indian Ocean. Megalastrum is absent from Australia and New Zealand. Seven species are treated in total. Two species and two varieties of Megalastrum have generally been recognized in Chile and the Juan Fernandez Islands. In this treatment, we recognize four species for the region, one of which is elevated to the species rank (M. glabrius stat. nov.), and one which is new (M. masafuerae sp. nov.). Within the Tristan da Cunha archipelago, two species occur: M. aquilinum comb, nov., and another here described as new, M. peregrinum sp. nov. Ile Amsterdam and Ile Saint-Paul harbor one species that is described here as new: M. taafense sp....

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.

Vertical distribution of Hymenophyllaceae species among host tree microhabitats in a temperate rain forest in Southern Chile

AbstractQuestion: Are differences in microhabitat preferences of co‐occurring epiphytic Hymenophyllaceae species (filmy ferns) correlated with differences in ecophysiological responses to light availability and humidity in the host tree?Location: The Andean foothills in south‐central Chile.Methods: We evaluated the distribution pattern of nine filmy fern species in microhabitats that differ in light availability and humidity in four host tree species. A DCA was developed to assess Hymenophyllaceae species microhabitat preference in terms of canopy openness (CO) and relative humidity. We assessed whether differences in chlorophyll content, maximum photochemical efficiency (Fv/Fm), photosynthetic capacity (Amax), evapotranspiration (E) and instantaneous water use efficiency (WUE) are consistent with any pattern.Results: CO and relative humidity differed significantly with height in the host trees. While CO increased with height in a host tree, relative humidity decreased. DCA analysis showed that filmy fern species distribution within and among trees was mainly explained by the relative humidity of the microhabitat. Chlorophyll content, chlorophyll a/b ratio, Amax and E differed significantly among filmy fern species. Amax and E were correlated with axis 1 scores from the DCA analysis.Conclusions: The vertical distribution and abundance of filmy fern species in Chilean temperate rain forest seems to be closely related to the different microhabitats offered by host trees. This pattern may reflect interspecific differences in ecophysiological traits related both to light availability and humidity. Our results suggest that humidity is the main environmental factor driving functional responses and habitat preferences of these filmy fern species.

Photochemical efficiency of PSII and photoprotective pigments in seedlings and adults of two Proteaceae with different shade tolerance from the Chilean temperate rain forest

Se estudia la variacion estacional en los parametros de amortiguamiento (quenching) energetico del fotosistema II y los pigmentos fotoprotectores en plantulas y adultos de dos Proteaceas con diferente tolerancia a la sombra: Embothrium coccineum J. R. et G. Foster (intolerante) y Lomatia ferruginea (Cav.) R. Br (tolerante). Se prueba la hipotesis que la especie intolerante a la sombra favorece los procesos fotoquimicos de energia conducentes a la asimilacion de C02 mientras que la tolerante a la sombra exhibe principalmente una disipacion no fotoquimica de la energia ante condiciones de luz desfavorables. Las diferencias en la disipacion de energia deben ser mas evidentes en plantulas que en adultos debido a que las condiciones de luz y temperatura de sus ambientes son mas contrastantes en este estado. La eficiencia fotoquimica maxima de las especies fluctuo entre 0.70-083. La eficiencia fotoquimica efectiva, el amortiguamiento fotoquimico y la tasa de transporte de electrones fue mayor en plantulas de E. coccineum que en las de L. ferruginea. Los parametros energeticos de amortiguamiento fotoquimico fueron mayores en adultos que en plantulas, pero a menudo similar entre los periodos del dia, estaciones, especies y estados de desarrollo, con excepcion de menores valores en las plantulas de E. coccineum en verano. Plantulas y adultos presentaron un mayor pool de xantofilas al mediodia en verano que en invierno, mientras que el pool de anteraxantina + zeaxantina fue siempre mayor al mediodia. Luteina experimento el mayor incremento durante el verano. Plantulas y adultos de E. coccineum mantuvieron una alta fotosintesis, una mayor proporcion de centros abiertos y mayor ETR que la especie tolerante a la sombra. Se concluyo que la especie intolerante a la sombra, E. coccineum, fue capaz de utilizar mas de la energia absorbida en la fotosintesis a traves de su ciclo de vida que la especies tolerante. Estas diferencias son consistentes con el caracter pionero, mayor tasa de crecimiento y mas amplia distribucion altitudinal y latitudinal de E. coccineum con respecto a L. ferruginea.

The canopy beetle faunas of Gondwanan element trees in Chilean temperate rain forests

AbstractAim To describe the coleopteran fauna occurring in canopies of temperate Gondwanan tree species in terms of their diversity and guild and taxonomic structures, and to test the proposition that this structuring reflects the Gondwanan origins of this fauna.Location The Andes and the coastal cordillera of temperate Chile.Methods Canopy fogging was used to sample beetles from 29 trees. The samples were statistically described using Schao and the Simpson diversity index D. Cluster analyses and multi‐dimensional scaling (MDS) were performed. The taxonomic and guild structures of the Chilean coleopteran fauna were compared quantitatively with those found in other parts of the world using homogeneity chi‐square and t‐tests.Results A collection of 25,497 beetle specimens was obtained primarily from Nothofagus dombeyi, Nothofagus obliqua and Araucaria araucana. The specimens collected were distributed between 485 morphospecies and included 107 putative, new generic‐level taxa and 223 apparently undescribed species. Estimates of the size of the canopy beetle fauna showed that 600+ species were likely to be present. The communities found on a tree species differed markedly between years. MDS plots showed less community divergence between tree species for predators than for phytophages and xylophages. The guild structure was similar to that found on Australian ‘Gondwanan’ trees but differed significantly from the community structures found on ‘Laurasian’ tropical and temperate trees in supporting fewer phytophages and saprophages, but more xylophages. The predator guild showed a different pattern, with tropical faunas differing from those of more temperate regions, irrespective of hemisphere, as did the distribution of superfamilies.Main conclusions The beetle fauna found in the canopies of N. dombeyi, N. obliqua and A. araucana was large (600+ species), with about half of the species undescribed. Schao was found to vary with sample size and to give lower estimates of S than species attenuation curves, raising the possibility that the two methods are estimating the sizes of different statistical communities. It is possible that the attenuation curve is estimating the number of species to be found on a particular tree species, while Schao is estimating the ‘carrying capacity’ for beetle species of individual trees, and this varies from tree to tree. Care also needs to be taken in experimental design when monitoring temporal changes in forest insect communities given the difference in communities found between years in this study. The proportions of phytophages, saprophages and xylophages resemble those of a ‘Gondwanan’ rain forest from Australia and differ significantly from those of tropical and temperate ‘Laurasian’ forests.

Natural selection on ecophysiological traits of a fern species in a temperate rainforest

Unlike other species of the genus Blechnum, the fern Blechnum chilense occurs in a wide range of habitats in Chilean temperate rainforest, from shaded forest understories to abandoned clearings and large gaps. We asked if contrasting light environments can exert differential selection on ecophysiological traits of B. chilense. We measured phenotypic selection on functional traits related to carbon gain: photosynthetic capacity (Amax), dark respiration rate (Rd), water use efficiency (WUE), leaf size and leaf thickness in populations growing in gaps and understorey environments. We assessed survival until reproductive stage and fecundity (spo- rangia production) as fitness components. In order to determine the potential evo- lutionary response of traits under selection, we estimated the genetic variation of these traits from clonally propagated individuals in common garden experiments. In gaps, survival of B. chilense was positively correlated with WUE and negatively correlated with leaf size. In contrast, survival in shaded understories was positively correlated with leaf size. We found positive directional fecundity selection on WUE in gaps population. In understories, ferns of lower Rd and greater leaf size showed greater fecundity. Thus, whereas control of water loss was optimized in gaps, light capture and net carbon balance were optimized in shaded understories. We found a significant genetic component of variation in WUE, Rd and leaf size. This study shows the potential for evolutionary responses to heterogeneous light environments in functional traits of B. chilense, a unique fern species able to occupy a broad successional niche in Chilean temperate rainforest.

Litter Quality and Climate Decouple Nitrogen Mineralization and Productivity in Chilean Temperate Rainforests

We measured litter quality, N mineralization, air and soil temperatures, soil moisture, and aboveground net primary production (ANPP) at 18 plots in three forest types typical of full‐stature forests found on western slopes of the Cordillera de Piuchué (CP) on Isla de Chiloé in southern Chile. The primary objectives were to examine the range of net N mineralization across forest types that have different vegetation and litter composition, assess probable controls on mineral N production and leaching, and to determine if the relationship between N mineralization and ANPP was similar to that observed in cool temperate northern hemisphere forests. Average annual litter lignin/N ratios were high in the evergreen montane broadleaf forest plots (50:1) and very high in the montane conifer plots (80:1). Net N mineralization during the summer months was correspondingly low (1.2 and 2.2 kg ha−1, respectively). The high litter lignin content and associated low rate of N mineralization can explain the extremely low concentrations of mineral N in soils and upland streams of this region. In the broadleaf evergreen coastal forest plots, lignin/N ratio was lower (23:1) and N mineralized was considerably greater over the same measurement period than in the montane forest plots (14 kg ha−1). In contrast to findings in many cool temperate northern hemisphere forests, ANNP in the broadleaf forest type was high (average 11.1 Mg ha−1 yr−1) in spite of the low net N mineralization rates, and ANPP and net N mineralized were not correlated. Net N mineralization was best correlated with litter quality, soil temperature, and soil moisture content, and ANPP was best correlated with growing degree days.

Vascular epiphytes in the temperate zones–a review

Vascular epiphytes are typically associated with tropical rainforests, whereas their occurrence in temperate forests is little appreciated. This review summarises the available information on epiphytism in the temperate zones (> 23.5 latitude), which has not been reviewed omprehensively for more than a century, and critically analyses the proposed mechanisms behind the observed biogeographical patterns. Although in the temperate zone epiphytic vascular plants are rarely as impressive as in tropical forests, there are noteworthy exceptions. Temperate rain forests of Chile and New Zealand, or montane forests in the Himalayas are comparable to many tropical forests in terms of epiphyte biomass and diversity, but differ in their taxonomic spectrum temperate epiphyte communities are generally dominated by ferns and fern-allies. Other temperate areas are not, however, necessarily barren of epiphytes, as repeatedly implied. Quite in contrast, local populations of epiphytes in a large number of other non-tropical areas in both the southern and the northern hemisphere can be quite conspicuous. The proposed reasons for the latitudinal gradients in epiphyte abundance and diversity (water scarcity or low tempera-tures). are not fully convincing and, moreover, still await experimental verification. Other factors, both historical (e.g., Pleistocene extinctions) and ecological (e.g., prevalence of conifers in the northern hemisphere), should also be taken into consideration to obtain a comprehensive explanation of the extant global distribution of vascular epiphytes.

Vertical distribution of fine root biomass of emergent Nothofagus dombeyi and its canopy associates in a Chilean temperate rainforest

In south-central Chile, basal area and wood volume development of Nothofagus spp. in some forests has been shown to be independent of that of associated tree species. Although this has been attributed to the emergent habit of Nothofagus, here we explore the possible role of belowground resource partitioning. We measured fine root biomass and vertical distribution of emergent Nothofagus dombeyi and its canopy associates in an old-growth rain forest, to test for evidence of vertical partitioning of belowground resources. Fine roots were sampled to a depth of 80 cm in three plots. Total fine root biomass averaged 4685 g m −1, N. dombeyi contributing about 22% of this figure. Roots were concentrated mainly in the upper horizons, with 69% of the total occurring at <30 cm. However, fine root biomass of N. dombeyi declined significantly more steeply with depth than that of its associates did, the average contribution of N. dombeyi to total fine root biomass decreasing from 29% in the uppermost 10 cm, to little more than 1% at 70–80 cm. The observed differences in rooting depth could be linked to differences in mycorrhizal syndromes: ectomycorrhizal Nothofagus might be expected to be more shallow-rooted than the VAM and non-mycorrhizal canopy species, because of the reportedly greater ability of ectomycorrhizal species to assimilate organic nitrogen from the litter layer. A degree of belowground resource use complementarity may therefore minimize competition between N. dombeyi and its associates, and could thus contribute to the additive basal area and productivity observed in these forests.

Survival and growth of seedlings of 12 Chilean rainforest trees in two light environments: Gas exchange and biomass distribution correlates

Abstract Mortality, growth, gas exchange and biomass distribution were measured in the seedlings of 12 Chilean temperate rainforest angiosperm trees in two contrasting artificial light environments (150 and 12 μmoles m−2 s−1), in order to explore life history diversity in this forest type, and examine the physiological and/or morphological traits associated with interspecific variation in seedling performance. Gas exchange traits were measured only in the high‐light treatment (150 μmoles m−2 s−1), owing to the very small size of leaves in the low‐light treatment. Relative growth rates (RGR) in high light were strongly correlated with photosynthetic capacity (P&lt; 0.0001). Mortality rates in low light had a strong positive correlation with light compensation point (P = 0.007) and photosynthetic capacity (P = 0.004). Furthermore, high‐light RGR was strongly positively correlated with low‐light mortality (P = 0.001). Biomass distribution traits showed little relationship with mortality or growth within either light level, except for a marginally significant positive correlation (P = 0.04) between leaf area ratio and mortality in low light. In view of the large interspecific differences in final size, the weak relationships between biomass distribution parameters and plant performance could be partially attributable to ontogenetic drift in these traits. Among taxa with high mortality rates in low light, short‐lived species (e.g. Aristotelia chilensis) had lower light compensation points, had greater phenotypic plasticity and grew much faster in both light environments than did longer‐lived species (Nothofagus dombeyi, Weinmannia trichosperma, Eucryphia cordifolia). Results support the view that survival of first‐year seedlings in low light is not enhanced by morphological traits that maximize growth potential (e.g. high leaf area ratio), and that leaf‐level gas exchange traits have an important role as determinants of interspecific variation in seedling performance. However, the limited range of interspecific variation observed in light compensation points indicates that other traits apart from those that we measured (e.g. carbon storage) must also be involved in seedling shade tolerance differences. The weak relationship between longevity and shade tolerance level among our 12 species suggests that it may not be feasible to ordinate life histories of Chilean temperate rainforest trees on a single axis of trait variation.

NESTING BIOLOGY OF TAPACULOS (RHINOCRYPTIDAE) IN FRAGMENTED SOUTH-TEMPERATE RAINFORESTS OF CHILE

Abstract We studied the effect of forest fragmentation on the nesting biology and reproductive success of three species of tapaculos (Rhinocryptidae) in relation to forest size, edge effects, and disturbance from livestock or logging over a 6-year period (1993–1999) in Chilean temperate rainforest. Overall, Mayfield nest success (n = 360) among the three species ranged from 64% to 85%, and predation accounted for 64% of nest losses. Considering all types of losses, nest mortality was similar in fragmented and unfragmented forest, but predation was higher in fragmented forest. Successful nest sites of the Chucao Tapaculo (Sclerochilus rubecula; the species with the largest sample size) were nearer forest edges, better concealed, closer to the ground, and had longer entrance tunnels, on average, than depredated nests. Reuse of nest sites by chucaos was more common in forest fragments with livestock or logging than in undisturbed forests, but reuse was independent of forest size. Success of second broods was...

Germination requirements and seedling shade tolerance are not correlated in a Chilean temperate rain forest.

• In a comparative study of 26 Chilean temperate woody species, the following questions were addressed. Are germination requirements correlated with seedling light requirements? Can germination requirements be used to delimit pioneer and nonpioneer guilds? • To assess dependence of germination on canopy gaps, germination percentages were compared experimentally in gap and understorey environments. Seedling light requirements were quantified by determining the mean light environment naturally occupied by juveniles of each species. • Germination was significantly higher in the gap than in the understorey in>30% of the species, although only one germinated exclusively in the gap. In the understorey, germination was higher in 19% of species, whereas 50% were indifferent to germination environment. Several light-demanding species germinated abundantly in the understorey. Both cross-species analysis and phylogenetically independent contrasts showed that seedling light requirements were not correlated with responsiveness of germination to the gap environment. • Results suggest that germination requirements and seedling light requirements are not coupled, and that requirement of canopy gaps for germination cannot be used to delimit pioneer and nonpioneer guilds in a Chilean temperate rain forest.

Juvenile tree growth rates and species sorting on fine‐scale soil fertility gradients in a Chilean temperate rain forest

AbstractAimWe sought to clarify the role of juvenile tree growth rates in species sorting along fine‐scale fertility gradients in the coast range forests of southern Chile.LocationIn montane forests in the coast range, the conifer Fitzroya cupressoides occupies the poorest soils, whereas dominance shifts to the evergreen angiosperms Nothofagus nitida and/or Weinmannia trichosperma on moderately infertile sites. On the most fertile sites, N. nitida is usually the sole overstorey dominant.MethodsWe examined the effects of soil depth and nitrogen availability on height growth and leaf nitrogen levels of the three common overstorey dominants. Sapling height growth rates and foliage nitrogen concentration were measured in 20 large gaps (&gt;0.1 ha), on sites of varied soil depth and potential N‐mineralization rates.ResultsHeight growth rates of Weinmannia and Nothofagus were strongly positively correlated with both soil depth and potential N‐mineralization. Height growth of Fitzroya was strongly correlated with soil depth, but not with N‐mineralization. Nothofagus and Weinmannia enjoyed large growth‐rate advantages over Fitzroya on the more fertile soils of the study area, and this advantage was reduced or nullified (but not reversed) on poor soils. This pattern was associated with species differences in nitrogen use: on fertile soils, Nothofagus and especially Weinmannia, achieved more height growth per unit of leaf N than Fitzroya, whereas differences were minimal on poor soils.Main conclusionsResults suggest that comparative height growth rates of juvenile trees, associated with nitrogen productivity differences, play a key role in determining eventual dominance on productive sites, but that traits other than growth (possibly related to nutrient retention) are more important on low fertility sites. Disturbance regimes appear to vary in relation to site fertility, and differential species responses to this superimposed disturbance gradient are also probably influential in determining overstorey composition.

Foliage area and crown nitrogen turnover in temperate rain forest juvenile trees of differing shade tolerance

Summary 1 Shade‐tolerant angiosperm trees are reported to require relatively fertile soils in temperate forests. We explored the possibility that high foliage allocation in shade‐tolerant species could result in higher whole‐plant nitrogen demands than in light‐demanding trees of comparable diameters. We measured foliage mass and area, leaf life span, and nitrogen (N) content of fresh foliage and leaf litter for juveniles of 11 evergreen angiosperms in a Chilean temperate rain forest. This permitted estimation of annual nitrogen losses in leaf litter fall by individuals of a given diameter. 2 Leaf life spans were longest in shade‐tolerant species. The highest leaf N levels were found in small short‐lived early successional trees, whereas among longer‐lived species there was no general relationship of leaf N with shade tolerance level. Shade‐tolerant species had lower N resorption efficiencies, and therefore higher leaf litter N concentrations on an area basis, than light‐demanding associates. 3 Foliage mass, foliage area and total crown N pool were strongly positively related to shade tolerance level. 4 Interspecific variation in annual N losses in leaf litter fall was more closely related to foliage area (R2 = 0.52) than to N concentration of leaf litter (R2 = 0.31) or leaf lifetimes (R2 = 0.01). Although the short‐lived early successional species Embothrium coccineum had the highest annual crown N losses of the 11 species, shade‐tolerant species had higher annual losses than light‐demanding overstorey dominants of comparable longevities. 5 The results are consistent with the proposal that the costs of obtaining enough N for crown maintenance and expansion may constrain the fitness of shade‐tolerant angiosperm trees in late successional stages on infertile sites, when soil nutrient availability is reduced by increased uptake and sequestration in biomass and litter. On the other hand, high N loss rates may be more sustainable for short‐lived early colonists that complete their life cycles in the initial stages of secondary succession, when nutrient availabilities are often relatively high.

Comparative Demography and Diversity of Small Mammals in Precordilleran Temperate Rainforests of Southern Chile

Small mammals were studied in two southern Chilean temperate rainforests in the precor-dillean Andes during 2 low-rainfall years following the 1982 El Niño event. Forests had somewhat different levels of canopy, shrub, and herbaceous cover, and species richness of trees but most of the same plants. Most captures were of four sigmodontine rodents, Akodon olivaceus, Abrothrix longipilis, Abrothrix sanborni, and Oligoryzomys longicaudatus; five other species and a putative hybrid were recorded. Maximum numbers were in January–July (late summer to winter) and lower numbers in August–December (late winter to early summer). All species had seasonal reproduction in September–April (spring to autumn). A. olivaceus and A. longipilis generally were long-lived, whereas survival rates were low for O. longicaudatus. Responses after the 1982 El Niño were small, and some populations increased during 1984. Populations of A. olivaceus fluctuated more than those of A. longipilis; those of A. sanborni were low and O. longicaudatus was sporadic and irruptive. Lower-elevational Chilean and precordilleran Argentine forests have similar species composition, but differences in demography and dominance of the former by more widespread, omnivorous A. olivaceus, animalivorous-fungivorous Abrothrix, and granivorous O. longicaudatus. Opportunities for immigration may explain greater homogeneity of populations of small mammals in Chilean rainforests relative to Argentine ones. Although responses to El Niño and subsequent droughts were weak, flowering episodes of bamboo (Chusquea) can have strong effects due to increased availability of food.

A new genus and species of long-clawed mouse (Rodentia: Muridae) from temperate rainforests of Chile

A new genus and species of long-clawed mouse (Rodentia: Muridae) from temperate rainforests of Chile

Quantitative Habitat Associations of Small Mammals along an Elevational Transect in Temperate Rainforests of Chile

Distribution and abundance of small mammals in temperate Andean rainforests are correlated with elevation. To interpret such patterns, we examined elevational variation in habitats and habitat use by small mammals. Elevation accounts for significant variation in 22 of 24 habitat metrics, reflecting the diminishing stature and more open canopies of higher-elevation rainforests. Principal-components analysis of habitat shows significant multivariate effects of elevation. Mammal species differ significantly in use of about half of the habitat variables, in ways generally consistent with morphology, behavior, and diet. Abundant species appear to occupy typical habitats along the transect, whereas rarer species are associated with more distinctive habitat types. Species overlap substantially in their use of habitats, but analyses of trap captures indicate that species are segregated at finer spatial scales. Spatial segregation at this scale may contribute to the coexistence of abundant species and congeners. Elevational variation in habitat and specific habitat associations provide a plausible explanation for correlations of mammalian distribution and abundance with elevation.

Distribution and Abundance of Small Mammals along an Elevational Transect in Temperate Rainforests of Chile

Assemblages of small mammals in temperate Andean rainforests of southern South America are diverse but poorly known. Herein, we describe an elevational transect through temperate rainforests in Valle de La Picada, Chile, during February and March, 1984. The transect consisted of standardized removal trapping (165 traps set in lines at ca. 7-m intervals and operated for 6 consecutive days) at each of seven elevations: 425 m, 505 m, 620 m, 715 m, 820 m, 920 m, and 1,135 m. A total of 514 small mammals representing two species of marsupials and seven species of sigmodontine rodents was collected. Trap success averaged 7.4% across traps, days, and elevations. Number of captures by individual traps during the sample period was indistinguishable from a Poisson distribution, both throughout the transect and at individual levels, suggesting independence of captures among traps. Captures were biased significantly by trap type, with museum specials securing significantly more Dromiciops australis and all forms of Akodon than Sherman live traps; the same biases were suggested by captures of Irenomys tarsalis and Auliscomys micropus . As expected, total number of individuals taken at each elevation declined throughout the sampling period while the cumulative number of species rose. Number of species, number of individuals, and species diversity varied inversely with elevation. Number of species and species diversity taken each day reached a maximum after 2–4 days of sampling. Captures of Rhyncholestes raphanurus, Akodon sanborni , putative hybrids of A. sanborni and Akodon longipilis , and I. tarsalis were correlated inversely with elevation. Conversely, D. australis, A. longipilis , and A. micropus were taken more commonly at higher elevations, whereas captures of Oryzomys longicaudatus, Akodon olivaceus , and Geoxus valdivianus appeared unrelated to elevation. Systematic sampling procedures are viewed as essential for describing fundamental patterns of abundance and distribution that can be compared with other studies.