Temperate Forests Of South America Research Articles

Identification of main variables in forest management for recovery of endemic species habitat in burned areas of southern Chile

Wildfires are among the most serious disturbances that affect forest biodiversity, damaging both flora and fauna. In some burned areas, vegetation recovery is a long and complex process that requires the support of restorative actions. This study evaluated changes in forest structural features after a fire that affect habitat suitability for Rhinocryptids, an endemic group of bird species that are indicators of biodiversity in the temperate forests of South America. The study area was the Malleco National Reserve, Chile, where the main ecosystems are temperate forests. Four species from the Rhinocryptidae family of birds were used as bioindicator species. This group of species is endemic to temperate forests in South America. After fires occurred in 2002 and 2015, affecting temperate forests dominated by several Nothofagus species, two field inventories were carried out in 2016 and 2018. These inventories recorded the presence of Rhinocryptids and some forests structural features. Differences between the two stages of forest regeneration were assessed using statistical tests (T-test and Wilcoxon–Mann–Whitney test) and a classification model was proposed to determine the presence of Rhinocryptidae species. The statistical analysis of forest structural features showed that the variables more relevant in the habitat recuperation are vertical stratification (p-value < 0.001) and understory cover (p-value = 0.053). The trained decision tree to predict the presence of Rhinocryptidae species had an accuracy of 65.22%. This model showed that the coexistence of more than one Rhinocryptidae species occurs when vertical stratification is not mono-stratified and the density is lower than 335 trees ha−1. Our results can help forest managers to consider forest structure as a suitable habitat for certain major wildlife species when implementing post-fire recovery plans.

Morphological description of the White-throated treerunner (Pygarrhichas albogularis, King 1831) in the Cape Horn Biosphere Reserve, Chile

The sub-Antarctic Magellanic ecoregion is one of the most pristine wilderness areas remaining on the planet, and is home to the southernmost forest ecosystems in the world, which are protected by the Cape Horn Biosphere Reserve (CHBR). In these forests, birds are the group of vertebrates with the largest number of species. However, essential aspects of the ecology and morphology of several species in this region are still understudied. These species include the White-throated treerunner (Pygarrhichas albogularis, King 1831), considered a “living fossil” as it is the only living species of the genus Pygarrhichas. In addition, this Furnariid is endemic to the temperate forests of South America. Using the 23-year database of the Long-Term Ornithological Research Program of Omora Park (54º56’S, 67º38’W), based on monthly captures and banding of forest birds, we describe the morphology, longevity, and presence of the White- throated treerunner in the CHBR. Between 2000 and 2022, 91 individuals were captured, including 29 recaptures. Based on these recaptures we determined that this species can live for at least five years. Morphometric measures showed a positive correlation between bill measures and tarsus length with both tail and wing lengths. The average weight varied for each season but not significantly. The greater presence on old-growth forests sites suggests a dependence of treerunners on large trees. This study expands the knowledge about the natural history of the White-throated treerunner, particularly about its populations inhabiting the world’s southernmost forests

Structural complexity is a better predictor than single habitat attributes of understory bird densities in Andean temperate forests

Abstract The simplification of forest structural complexity, caused by anthropogenic land-use practices, is one of the main threats to understory specialist birds. We examined the association of both single structural attributes and structural complexity, with the density of 4 understory bird species in the Global Biodiversity Hotspot “Chilean Winter Rainfall-Valdivian Forests” of South America. Between 2011 and 2013, we surveyed habitat attributes and conducted bird point counts in 505 plots in Andean temperate ecosystems in Chile. In each habitat plot, we measured understory density, volume of coarse woody debris (CWD), number of snags, diameter at breast height (DBH) of trees, and leaf litter depth. With these attributes, we developed an index of stand structural complexity (ISC). On average, old-growth forests had higher values for understory density, CWD volume, DBH, and litter depth than secondary forests and open fields, and thus greater values of ISC. The density of understory birds was positively correlated with the ISC for the Rhinocryptidae Pteroptochos tarnii, Scelorchilus rubecula, and Scytalopus magellanicus. We also found a positive association between understory density and litter depth, with the density of the Furnariidae Sylviorthorhynchus desmursii. However, this latter species showed a negative association with the density of snags. Our results suggest the utility of using an index of structural complexity, rather than single or even additive habitat attributes, for determining the density of understory specialist birds. We recommend that management plans should promote the retention of habitat attributes that contribute to the structural complexity of temperate forests of South America and beyond.

Tree-cavity survival for biodiversity in temperate forests of South America: A multi-scale approach

Tree cavities are critical habitat attributes for a diversity of species that use them for reproduction and shelter. Worldwide, their availability has shown an intense decline in forests because of the loss of old-growth stands and the reduction in cavity recruitment. These disturbance processes are influenced by factors occurring across different scales: from cavities to landscapes. We analyzed the survival of 613 cavities in 455 trees in old-growth and second-growth forests over 10 years in Andean temperate forests in southern South America, Chile. Kaplan–Meier and Cox proportional hazards models were used to determine median cavity survival and its influencing factors at the cavity, tree, stand and landscape scales. The median survival was six years. Non-excavated cavities (6 years) survived longer than excavated cavities (4 years), with a significantly longer lifespan in large decaying trees. Cavities’ survival was strongly influenced by cavity- and tree-scale factors, including their origin, the vertical cavity depth, tree decay class, tree branch order and tree diameter class. In old-growth forests, most cavities were found in live decaying trees, while in second-growth forests they were mostly in long-dead trees (snags). We suggest that management should maintain forest structural complexity, retaining dead wood and trees in different stages of decay to permit a continuous supply of substrates over time for the formation of cavities.

Climate change can disrupt ecological interactions in mysterious ways: Using ecological generalists to forecast community-wide effects

Ecological interactions are the backbone of biodiversity. Like individual species, interactions are threatened by drivers of biodiversity loss, among which climate change operates at a broader scale and can exacerbate the effects of land-use change, overharvesting, and invasive species. As temperature increases, we expect that some species may alter their distribution towards more amenable conditions. However, a warmer and drier climate may impose local effects on plants and animals, disrupting their interactions before noticeable changes in distribution are observed. We used a mutualistic trio from the temperate forests of South America to theoretically illustrate how climate change can disrupt ecological interactions, based on our current knowledge on this system. This study system comprises three generalist species with intersecting roles: a keystone mistletoe, a pollinator hummingbird, and a frugivorous marsupial that disperses the seeds of many species. On the one hand, drought causes water stress, increasing mortality of both mistletoe and host plants, and reducing the production of flowers and fruits. These resource shortages negatively impact animal's foraging opportunities, depleting energy reserves and compromising reproduction and survival. Finally, warmer temperatures disrupt hibernation cycles in the seed-dispersing marsupial. The combined result of these intersecting stressors depresses interaction rates and may trigger an extinction vortex if fail to adapt, with deep community-wide implications. Through negatively affecting generalist mutualists which provide resilience and stability to interaction networks, local-scale climate impacts may precipitate community-wide extinction cascades. We urge future studies to assess climate change effects on interaction networks rather than on singular species or pairwise partnerships.

Molecular n-alkyl leaf waxes of three dominant plants from the temperate forest in South America

The n-alkyl leaf waxes of the temperate forest of South America are poorly studied, despite being a biogeographically isolated forest spanning wide environmental conditions. To evaluate whether local species adaptation and environmental changes influence the n-alkyl leaf wax composition, we measured the molecular abundance and distribution of n-alkyl leaf waxes (n-alkanoic acids, n-alkanes and n-alkanols) of three dominant native species from southern temperate forest in South America. We surveyed Araucaria araucana (n = 9), Nothofagus dombeyi (n = 17) and Chusquea sp. (n = 21) at different elevations. The relationship of n-alkyl leaf wax abundance and distribution with elevation is not significant in any species, except for n-alkane ACL (average chain length) in Chusquea sp. Significant correlations are found for n-alkanoic acid abundance with precipitation and aridity in Chusquea sp. and n-alkane abundance and ACL with temperature in A. araucana. These data suggest a species-specific response to environmental variables. The main similarity in the three species is a higher abundance of n-alkanoic acids (>60%) relative to other n-alkyl leaf waxes. Only n-alkanols are not correlated to any environmental variable, and neither ACL nor Cmax overlap among species. These results suggest n-alkanols as a potential chemotaxonomic indicator at a lower taxonomic level in the region.

Large trees and decay: Suppliers of a keystone resource for cavity‐using wildlife in old‐growth and secondary Andean temperate forests

AbstractTree cavities are a keystone resource for many wildlife species worldwide. In Andean temperate forests of South America, many species of birds, mammals and reptiles use cavities to achieve their life history requirements. However, information on cavity supply and drivers of cavity production in these forests remains largely undocumented. We examined the patterns of tree‐cavity supply in successional native forests, exploring the potential drivers of cavity occurrence and relative abundances in Andean temperate ecosystems of southern Chile. In 10 forest stands, we established 369 vegetation plots and measured 7951 trees. For each tree, we recorded the species and measured the diameter at breast height (DBH), decay class and number of cavities. While tree density was much higher in secondary than in old‐growth forest stands, the density of nonexcavated cavities was higher in old‐growth than in secondary forests. Cavity occurrence and relative abundances (number of cavities per tree) were higher in large decaying and standing dead trees (i.e. habitat legacies) than in young healthy trees. Importantly, DBH and decay had a stronger influence on the supply of nonexcavated than excavated cavities. Our results highlight the importance of old‐growth forest stands, tree decay processes and habitat legacies for securing a continuous supply of a keystone habitat resource for tree cavity‐using wildlife in a global biodiversity hotspot of South America.Abstract in Spanish is available with online material.

Gevuina avellana and Lomatia dentata, two Proteaceae species from evergreen temperate forests of South America exhibit contrasting physiological responses under nutrient deprivation

Gevuina avellana and Lomatia dentata are Proteaceae species from evergreen temperate forests, but only G. avellana can colonize nutrient deprived volcanic depositions. We hypothesized that under nutrient deprivation, G. avellana would present higher survival, physiological performance, and adjustment regarding cluster root (CR) formation and carboxylate exudation rate than L. dentata. We evaluated relative growth rate, maximal photosynthetic rate, photochemical performance, nitrogen (N) and phosphorus (P) leaf concentrations, specific leaf area, photosynthetic P and N use efficiency (PPUE and PNUE), CR formation and carboxylate exudation rate. Plants were grown in a greenhouse, using recent volcanic substrate and watered with different nutrient Hoagland (H) solutions: modified full Hoagland, without P, without N, or tap water. Both species showed high survival. G. avellana exhibited higher growth rates (RGR), and higher CR number and biomass allocation under nutrient deprivation, but lower carboxylate exudation rates than L. dentata. Malate, oxalate and succinate were detected in root exudates of G. avellana but only oxalate in L. dentata. However, PPUE and PNUE were higher in L. dentata than in G. avellana . Our hypothesis was not entirely accepted, CR formation was more “constitutive” in G. avellana, and composition of carboxylates was more diverse, with lower exudation rates than L. dentata. Moreover, L. dentata showed higher PNUE and PPUE, partly explained by thinner leaves. Different responses are related with edaphic conditions, where both species inhabit: more diverse to G. avellana and restricted to developed soils to L. dentata.

Physiological dormancy broken by endozoochory: Austral parakeets (Enicognathus ferrugineus) as legitimate dispersers of calafate (Berberis microphylla) in the Patagonian Andes

Abstract Aims Seed dispersal by endozoochory is an important process in plant regeneration and the establishment of new populations. Seeds with dormancy may especially benefit after disperser gut passage. However, the ways in which gut passage affect the germination of plant species with physiological dormancy remain unclear. Here, we experimentally assessed the mutualistic interaction between the Austral parakeet (Enicognathus ferrugineus) as a disperser of calafate (Berberis microphylla), a thorny bush inhabiting the understory of the Austral temperate forests of South America with seeds that are characterized by deep physiological dormancy. Methods Germination success and viability of calafate seeds obtained from faeces and from intact fruits were tested under four treatments: (i) digested seeds, (ii) digested seeds with faecal extract, (iii) intact seeds from fruit and (iv) intact seeds from fruit with pulp. Important Findings About 65% of the Austral parakeet droppings contained calafate seeds. Viability of seeds did not differ between treatments. However, germination was significantly higher in digested seeds than in intact seeds from fruits, while no difference was found between faecal and pulp extracts. Neither faecal matter nor fruit pulp provided seeds with any ecological advantages derived from enhancing germinability, but did confer some disadvantage in germination time. Faecal matter is expected to be completely lacking around seeds after several months under snow before germinating in the following spring, given intense washing due to persistent rain and the spring thaw in the Patagonian Andes. The higher germinability along with faster germination of digested seeds supports the hypothesis of a legitimate mutualistic interaction between Austral parakeets and calafate. We hypothesized that the passage through the disperser digestive tract might break physiological dormancy as differences in germinability between ingested and non-ingested seeds. Our results highlight the relevant role of endozoochory in plant species with physiological dormancy living in highly seasonal environments.

Range-wide genetic structure in the thorn-tailed rayadito suggests limited gene flow towards peripheral populations

Understanding the population genetic consequences of habitat heterogeneity requires assessing whether patterns of gene flow correspond to landscape configuration. Studies of the genetic structure of populations are still scarce for Neotropical forest birds. We assessed range-wide genetic structure and contemporary gene flow in the thorn-tailed rayadito (Aphrastura spinicauda), a passerine bird inhabiting the temperate forests of South America. We used 12 microsatellite loci to genotype 582 individuals from eight localities across a large latitudinal range (30°S–56°S). Using population structure metrics, multivariate analyses, clustering algorithms, and Bayesian methods, we found evidence for moderately low regional genetic structure and reduced gene flow towards the range margins. Genetic differentiation increased with geographic distance, particularly in the southern part of the species’ distribution where forests are continuously distributed. Populations in the north seem to experience limited gene flow likely due to forest discontinuity, and may comprise a demographically independent unit. The southernmost population, on the other hand, is genetically depauperate and different from all other populations. Different analytical approaches support the presence of three to five genetic clusters. We hypothesize that the genetic structure of the species follows a hierarchical clustered pattern.

Age and terminal reproductive attempt influence laying date in the thorn‐tailed rayadito

Age‐specific variation in reproductive effort can affect population dynamics, and is a key component of the evolution of reproductive tactics. Late‐life declines are a typical feature of variation in reproduction. However, the cause of these declines, and thus their implications for the evolution of life‐history tactics, may differ. Some prior studies have shown late‐life reproductive declines to be tied to chronological age, whereas other studies have found declines associated with terminal reproduction irrespective of chronological age. We investigated the extent to which declines in late life reproduction are related to chronological age, terminal reproductive attempt or a combination of both in the thorn‐tailed rayadito Aphrastura spinicauda, a small passerine bird that inhabits the temperate forest of South America. To this end we used long‐term data (10 years) obtained on reproductive success (laying date, clutch size and nestling weight) of females in a Chilean population. Neither chronological age nor terminal reproductive attempt explained variation in clutch size or nestling weight, however we observed that during the terminal reproductive attempt older females tended to lay later in the breeding season and younger females laid early in the breeding season, but this was not the case when the reproductive attempt was not the last. These results suggests that both age‐dependent and age‐independent effects influence reproductive output and therefore that the combined effects of age and physiological condition may be more relevant than previously thought.

Sex Ratio and Abundance Fluctuations of Sarcosaprophagous Calyptratae (Diptera): Field Evaluation of Two Sampling Techniques

Abundance of sarcosaprophagous Calyptratae species was monitored by using baited traps and active captures with hand net. Analysis of field data collected in three protected areas in the Valdivian temperate forest of South America (Lanín National Park, Lago Puelo National Park, and Los Alerces National Park) indicated that bottle traps baited with putrescine is a reliable method to estimate local abundance of sarcosaprophagous species by comparison to the active capture method. Also, we describe and compare general patterns of sex bias for four dominant species: Sarconesia magellanica (Le Guillou), Calliphora vicina Robineau-Desvoidy, Microcerella spinigena (Rondani), and Oxysarcodexia varia (Walker). From these analyses, it can be concluded that abundance fluctuations of flies showed significant relationship between the sampling methods. This study showed that besides the expected interspecific differences in trapping efficiency, there are acute intraspecific differences of sex ratios between sampling methods.

GERMINATION AND SEEDLINGS DEVELOPMENT OF THE THREATENED SPECIES Quillaja brasiliensis

ABSTRACT Brazil is a mega diverse country, but as consequence of habitat degradation several plant species are threatened. Quillaja brasiliensis is a rare and threatened tree species of the temperate forests of South America. We investigated protocols for germination, seedling growth and transplantation. We discuss some ecological matters that could affect the species’ establishment. We evaluated germination under a range of storage periods, temperature and light conditions, the effects of transplantation and the development of seedlings under two sowing methods. We found that seeds germinated rapidly and have a high germination rate. Temperature infl uenced germination vigour, and photoperiod infl uenced synchrony. There was increased and faster germination under controlled culture conditions. The high germination rate and rapid growth qualify Q. brasiliensis as a potential species for restoring degraded areas and enrichment programmes.

Geographic body size variation in ectotherms: effects of seasonality on an anuran from the southern temperate forest.

BackgroundBody size variation has played a central role in biogeographical research, however, most studies have aimed to describe trends rather than search for underlying mechanisms. In order to provide a more comprehensive understanding of the causes of intra-specific body size variation in ectotherms, we evaluated eight hypotheses proposed in the literature to account for geographical body size variation using the Darwin’s frog (Rhinoderma darwinii), an anuran species widely distributed in the temperate forests of South America. Each of the evaluated hypotheses predicted a specific relationship between body size and environmental variables. The level of support for each of these hypotheses was assessed using an information-theoretic approach and based on data from 1015 adult frogs obtained from 14 sites across the entire distributional range of the species.ResultsThere was strong evidence favouring a single model comprising temperature seasonality as the predictor variable. Larger body sizes were found in areas of greater seasonality, giving support to the “starvation resistance” hypothesis. Considering the known role of temperature on ectothermic metabolism, however, we formulated a new, non-exclusive hypothesis, termed “hibernation hypothesis”: greater seasonality is expected to drive larger body size, since metabolic rate is reduced further and longer during colder, longer winters, leading to decreased energy depletion during hibernation, improved survival and increased longevity (and hence growth). Supporting this, a higher post-hibernation body condition in animals from areas of greater seasonality was found.ConclusionsDespite largely recognized effects of temperature on metabolic rate in ectotherms, its importance in determining body size in a gradient of seasonality has been largely overlooked so far. Based on our results, we present and discuss an alternative mechanism, the “hibernation hypothesis”, underlying geographical body size variation, which can be helpful to improve our understanding of biogeographical patterns in ectotherms.

Molecular and fossil evidence disentangle the biogeographical history of Podocarpus, a key genus in plant geography

AbstractAimThe genus Podocarpus (Podocarpaceae) provides an opportunity to contrast biogeographical hypotheses within and among continents, and to analyse divergence between disjunct tropical and temperate forests of South America. We developed a calibrated phylogeny of Podocarpus to reconstruct the ancestral areas and potential expansion routes within Podocarpaceae.LocationPodocarpus consists of two extant subgenera: Foliolatus from Asia and Oceania, and Podocarpus located in Gondwanan continents and north to the Caribbean. The paper focuses mainly on the area occupied by the latter subgenus.MethodsWe combined previously published and novel DNA sequences with fossil records. New species sequenced are members of Podocarpus subgenus Podocarpus from South and Central America. We assembled DNA sequences of the chloroplast (matK and rbcL) and nuclear (ITS1 and ITS2) to analyse phylogenetic relationships within Podocarpus subgenus Podocarpus by Bayesian methods, which were calibrated using macrofossils that could be confidently identified as modern genera. Ancestral areas were inferred using the dispersal–extinction–cladogenesis model.ResultsThe phylogenetic reconstruction inferred a minimum age for the origin of Podocarpus s.l. in the late Cretaceous–early Palaeogene (63 Ma) and strongly supported monophyly of the genus Podocarpus and of subgenera Podocarpus and Foliolatus. Subgenus Podocarpus consists of two monophyletic, latitudinally structured clades. One clade consists of temperate American species while the other includes species from tropical‐subtropical Africa and South America.Main conclusionsThe history of the subgenera within Podocarpus is older than previously reported: they can be traced back to late Cretaceous–early Palaeocene biogeographical connections between Australasia and South America through Antarctica. Latitudinally disjunct lineages within South America most probably diverged from widespread ancestors as a result of a persistent arid barrier that was established prior to the late Palaeogene. The calibrated age for the Tropical–Subtropical clade suggests an Atlantic–subtropical biogeographical corridor between South America and Africa long after the breakup of Gondwana and the stabilization of the circum‐Antarctic current.

External morphology, chondrocranium, hyobranchial skeleton, and external and internal oral features of &lt;i&gt;Rhinoderma rufum&lt;/i&gt; (Anura, Rhinodermatidae)

The species of Rhinoderma Duméril &amp; Bibron are endemic to the temperate forests of South America in southern Chile and Argentina (Formas et al. 1975). Both have specialized reproductive modes, Rhinoderma darwinii Duméril &amp; Bibron undergoes complete embryonic and larval development in the mouth of the male: newly metamorphosed frogs are expelled into the terrestrial environment (Jorquera et al. 1972). In contrast, embryos of R. rufum (Philippi) do not remain in the male's mouth, but instead are expelled into the water as larvae (Jorquera et al. 1974). Jorquera et al. (1972, 1974) described the normal development of both species. The chondrocranial morphology and visceral skeleton of R. darwinii was described by Lavilla (1987) and its internal oral features by Wassersug &amp; Heyer (1988). The table of normal development of R. rufum (Jorquera et al. 1974) emphasized the duration of each stage of development: however, some features currently used for comparative purposes in tadpole morphological studies were not included or described only briefly. In this work, I include a detailed description of the morphology, particularly of the mouthparts, of the tadpoles of R. rufum, and describe the chondrocranium, hyobranchial skeleton, and the internal features of the oral cavity in this species. In addition, I compare the morphology of the mouth, chondrocranium, and hyobranchial skeleton of the congeneric tadpoles, considering different modes of feeding (endotrophic in R. darwinii versus exotrophic in R. rufum). Last, I present some thoughts about the evolution of larvae of Rhinoderma.

Ecological consistency across space: a synthesis of the ecological aspects of Dromiciops gliroides in Argentina and Chile

Dromiciops gliroides is an arboreal marsupial found in the temperate forests of South America (36-43 °S). This species is the sole extant representative of the order Microbiotheria, and is a key seed disperser of many native plant species, including the keystone mistletoe Tristerix corymbosus. Here, we synthesized the current knowledge on the ecological aspects of this species, and compared the available information from Argentina and Chile. Population density (23 ± 2 (mean ± SE) individual/ha) and home range (1.6 ± 0.6ha) appear to be relatively similar across a marked ecological gradient in the mainland, but lower densities (7 ± 2 individual/ha) and smaller home ranges (0.26 ± 0.04ha) were detected at island sites. We detected regional variation in body condition in Chile, but there were no significant differences across a wider E-W gradient. Movement patterns fit a random walk model; such behavior might have important consequences in shaping plant's spatial patterns. Although our data suggest that D. gliroides is more tolerant to habitat disturbance than previously thought, its incapability to disperse across non-forested areas suggests that the rapid rate of habitat loss and fragmentation that characterizes southern temperate forests likely poses a serious threat to this species. These ecological similarities are surprising given that forests studied receive dramatically different rainfall and correspond to distinct forest types. The evidence synthetized here dispels some of the myths about this species but also stresses the need for more comprehensive ecological studies across its distribution range.

Mycorrhizal Status of Obligate and Facultative Epiphytic Ferns in a Valdivian Temperate Forest of Patagonia, Argentina

Arbuscular mycorrhizae (AM) influence the growth, morphology and fitness of the plant species they colonize. Despite the abundance and importance of epiphytes in forest dynamics, little is known about AM in these plants. Abundant epiphytes are present in the Valdivian temperate forests of South America, where ferns are one of the most important components of the epiphytic vascular flora. The aim of this work was to analyze the occurrence of AM in sporophytes of obligate and facultative epiphytic fern species in a Valdivian temperate forest of Patagonia, Argentina. We examined the roots of 10 epiphytic fern species. Roots of 66 sporophytes were collected from tree trunks and branches between 0.5 and 2 m height above the ground and were stained by using a modified Phillips and Hayman (1970) method. Of the 10 species examined in the present study two were found to be obligate epiphytes, six were facultative epiphytes and two could not be classified because few individuals were found. Most of them lacked AM structures, except for seven Hymenophyllum sporophytes which were rooted in soil and possessed scarce knobby hyphae and structures similar to coils and vesicles. Abundant dark septate fungi were observed within the cortex of all samples. The absence of AM in epiphytes may be explained by different ecological or taxonomic reasons, but in this study we suggest that root morphology may be an important factor influencing mycorrhizal behavior in ferns.

When do nurse plants stop nursing? Temporal changes in water stress levels in Austrocedrus chilensis growing within and outside shrubs

AbstractQuestion: Does the proximity of shrubs affect seasonal water stress of young Austrocedrus chilensis trees (a native conifer of the Austral Temperate Forest of South America) in xeric sites?Location: A. chilensis xeric forest in northwest Patagonia, Argentina.Methods: We examined the dependence of predawn twig water potential on tree development (seedling to adult) and proximity to nurse shrubs during spring and summer. We analysed spatial associations of seedlings, saplings and adult trees with nurse shrubs, and also evaluated if trees affected shrub canopy vitality.Results: Water stress in Austrocedrus trees was affected by shrub presence. Small trees (i.e.&lt;0.5 m in height) growing in the open were most stressed, particularly in summer. Small trees growing within a shrub canopy had low water stress and little change between spring and summer. The opposite trend, however, was true for the medium‐height category (i.e. 0.5‐1.5 m in height); trees in this size category were more stressed when growing within the shrub canopy than in the open. Larger Austrocedrus trees (i.e.&gt;2 m in height) were not affected by shrub presence. Austrocedrus trees were spatially associated with shrubs in all height classes; however, the percentage of living shrub canopy decreased with tree height.Conclusions: In xeric areas of northwest Patagonia, the strength and direction of interactions between A. chilensis and shrubs, in terms of tree water stress, are dynamic and modulated by tree size and environmental conditions. Overall, positive effects of shrubs on early developmental stages appear to be more important than subsequent negative interactions, since nursing effects could generate a spatial association of shrubs and Austrocedrus trees that persists through later successional stages. These findings shed light on mechanisms behind successional changes, and have important conservation and management implications.

The potential key seed-dispersing role of the arboreal marsupial Dromiciops gliroides

Marsupial seed dispersal is a rare phenomenon, although it may be ecologically significant in southern South America. The marsupial Dromiciops gliroides is endemic to the northern part of the temperate forest of South America. Here we describe the food habits and examine the potential role of D. gliroides as a seed disperser. We evaluated the diet of this marsupial in its natural habitat and in captivity. Dromiciops gliroides is omnivorous showing high consumption of a diversity of fruits. In captivity, D. gliroides consumed fruits from 80% of 22 native plant species we examined. Experiments conducted with fruits from two common understory shrubs show that seed passage through the digestive tract of D. gliroides enhances germination. Our results suggest that this species may have an important role as a seed disperser in the temperate forest of South America, which might offset a scarcity of frugivorous bird species.