Tree Nothofagus Research Articles

Disentangling the ecological value of tree hollows to wildlife along elevation gradients: The case of southern temperate forests

The ecological importance of tree hollows relies on environmental factors that influence microhabitat requirements for wildlife. Thus, the value of hollows as thermal microhabitats should increase with elevation, but understanding this phenomenon involves a separate assessment of hollow use and site occupancy. Here, we evaluated the use of tree hollows by vertebrates and invertebrates along elevational gradients in southern Chilean temperate forests. Camera trap and Bayesian models were used to analyze separately hollow use and site occupation. Four of seven invertebrate taxa and 21 of 25 vertebrate species used hollows. All lizard and mammal species (rodents, bats, kodkods, and opossums) were found using hollows, while 13 bird species (77 %) did it. The hollow occupation of only two species responded to elevation, with Chilean opossums being more likely to use hollows as elevation increased, while black-throated huet-huets exhibited the opposite pattern. Chucao and Magellanic tapaculos increased their occurrence probability as elevation increased while that of jewel and blue-bellied lizards increased with elevation. Giant bumblebees, austral thrushes, and Chilean opossums preferred hollows in evergreen (non-Nothofagaceae) tree species while huet-huets preferred hollows in Nothofagus trees. A strong positive association between hollow density and elevation was also found. These results suggest Chilean opossums benefit from using hollows at high altitudes due to their sensitivity to low temperatures while the lower availability of tree hollows at low altitudes causes black-throated huet-huets to be limited by hollows. Thus, wildlife conservation in these forests requires the maintenance of hollows in different tree species along elevational gradients.

Trophic facilitation in forest restoration: Can Nothofagus trees use ectomycorrhizal fungi of the pioneer shrub Leptospermum?

The benefits of plant-to-plant facilitation in ecological restoration are well recognized, yet the potential for indirect trophic facilitation remains understudied. Nothofagus (southern beech; Nothofagaceae) is an iconic southern hemisphere tree genus that is frequently the focus of ecological restoration efforts. One aspect of Nothofagus ecology that may limit restoration success is the availability of appropriate ectomycorrhizal fungi. It has been suggested that pioneer dual-mycorrhizal hosts such as Leptospermum species (Myrtaceae) could facilitate Nothofagus establishment by providing fungal inoculum, but the capacity for Nothofagus to use Leptospermum ectomycorrhizal fungi is unknown. To investigate potential indirect facilitation, we conducted a common garden pot trial to determine if Nothofagus cliffortioides (mountain beech) can use symbionts from Leptospermum scoparium (mānuka) ectomycorrhizal communities. Nothofagus and Leptospermum seedlings were grown in monoculture and mixed pairs with reciprocal "home" and "away" soil fungal inoculum. ITS2 metabarcoding of eDNA from hyphal ingrowth bags revealed that Nothofagus and Leptospermum inoculum contained different ectomycorrhizal fungal communities, but that half of the common ectomycorrhizal taxa identified were found in both soil types, suggesting generalist fungi exist. Nothofagus was able to form associations with some fungal species originating from Leptospermum inoculum, however, probable spore contamination meant that the proportion of root colonization associated with those species was ambiguous. Root ectomycorrhizal colonization rates were positively associated with seedling biomass, and there was some evidence of a home soil inoculum advantage in Nothofagus, but these effects were minor. Additionally, we found evidence that home inoculum provides a protective advantage against drought stress for Leptospermum seedlings. Our results indicate the potential for using Leptospermum to promote Nothofagus establishment in restoration plantings and highlight the possible benefits of considering fungal mutualists in ecological restoration projects.

Uncovering the hidden hosts: Identifying inoculum reservoirs for Phytophthora pseudosyringae in Nothofagus forests in Chile

AbstractMortality of Nothofagus trees in native forests in Chile has been observed for more than 30 years. Phytophthora pseudosyringae was identified as the causal agent of partial defoliation and bleeding cankers on Nothofagus obliqua and N. alpina. Nevertheless, to improve the conservation of natural resources it is crucial to determine potential native hosts that may act as inoculum reservoirs. Two N. obliqua stands were visited and all native plant species with symptoms resembling those caused by Phytophthora spp. were examined. Seven isolates from cortical and foliar tissues were isolated and subsequentially identified as P. pseudosyringae. Pathogenicity tests were carried out on eight species from a native forest. P. pseudosyringae caused cankers in N. obliqua, N. dombeyi and Persea lingue. Under natural conditions, no symptoms were detected on leaves of Cryptocarya alba, N. dombeyi, N. obliqua or Peumus boldus, but lesions were formed in inoculation assays under a controlled environment, suggesting that these species may act as hosts. Leaf necrosis in P. lingue was observed in both natural and controlled conditions. P. pseudosyringae can sporulate on lesions of C. alba, N. dombeyi and N. obliqua leaves. In Sophora macrocarpa, sporulation was observed both on asymptomatic tissues and on lesions. The frequent association of S. macrocarpa in the understorey of Nothofagus spp. strengthens the putative role of S. macrocarpa as an inoculum reservoir for epidemic events in Nothofagus. This is the first study carried out in the Southern Hemisphere on the life cycle of P. pseudosyringae in native Nothofagus forests.

Endophytic seed-associated microbial diversity and its impact on seedling growth of the Andean tree Nothofagus obliqua (Mirb.) Oerst

Endophytic seed-associated microbial diversity and its impact on seedling growth of the Andean tree Nothofagus obliqua (Mirb.) Oerst

Environmental evolution of western Tierra del Fuego (∼54°S) since ice-free conditions and its zonal/hemispheric implications

By virtue of its position adjacent to the Drake Passage, Tierra del Fuego in South America allows examining the vegetation and environmental history of the southernmost continental landmass outside Antarctica, and the evolution of the Southern Westerly Winds-Southern Ocean (SWW–SO) coupled system since the Last Glacial Maximum (LGM). For that purpose, we studied sediment cores from Lago Charquito, a small closed-basin lake in central-west Tierra del Fuego with a continuous lacustrine record since ∼17.3 ka. Ice-free conditions at the site imply a ∼70 km retreat of the Bahía Inútil glacier lobe from its LGM position during a ∼800-year interval, a trend that continued until its disappearance ∼100 km upstream from L. Charquito, ∼800 years later. Our palynological data show an open landscape dominated by cold-tolerant shrubs and herbs between ∼17.3–12.9 ka, with increases in precipitation of SWW origin at ∼16.3 ka, ∼14.7 ka, between ∼8.7–7.6 ka, and after ∼6.8 ka. Warming at ∼12.9 ka initiated an abrupt afforestation trend that stalled during the early Holocene (∼12–8.7 ka) owing to a precipitation decline and wildfires, and later resumed in response to invigorated SWW. We hypothesize that sparse Nothofagus tree populations inhabited the periphery of the Patagonian Ice Sheet (PIS) during the LGM and migrated toward the Andes contemporaneous with glacier recession as temperature rose during the Last Glacial Termination (T1). We posit that besides establishing topographic and climatic barriers for land biota, the PIS enabled the connectivity of cold-tolerant hygrophilous plant populations along a humid fringe adjacent to its land-based perimeter, despite the presumably dry conditions downwind from the eastern PIS margin. Our results suggest that southward shifts or expansion of the SWW toward or beyond Tierra del Fuego enhanced upwelling and ventilation of deep waters in the SO, northward shifts or weakening had the opposite effect. We observe that the time evolution of atmospheric CO2 concentrations, high-latitude air and sea-surface temperatures, and sea level during T1 fall short in explaining the timing and abruptness of the Bahía Inútil glacier lobe collapse, and quite possibly multiple other glacier lobes from the PIS.

Teline monspessulana Can Harm the Chilean Native Tree Nothofagus obliqua: Effects on Germination and Initial Growth.

Teline monspessulana is highly invasive in several countries around the world. This species pressurizes and displaces several native and endemic tree species in south-central Chile such as Nothofagus obliqua, the native species of greatest timber interest. We determined the effects induced by allelochemical stress of T. monspessulana on N. obliqua germination and initial growth. Germination was evaluated under in vitro conditions and in natural substrate obtained from sites inhabited by N. obliqua and from nearby areas invaded by T. monspessulana. Controls irrigated with tap water and treatments with aqueous extracts of aerial organs of the invasive species were used. Morphometric and morphological variables were evaluated, and the composition of alkaloids and phenols from the plant organs used for the aqueous extracts was determined. The substrates were also chemically characterized. Allelochemicals synthesized by T. monspessulana caused germination and growth inhibition and tissue-level alterations, as well as leaf and root damage in N. obliqua seedlings. In the aerial organs of T. monspessulana, the quinolizidine alkaloids aphylline, caulophylline, anagyrine, and sophocarpine were mainly detected. In addition, 21 phenolic compounds were identified, including gallic acid, vanillic acid, chlorogenic acid, p-coumaric acid, and quercetin. The phytotoxic potential of T. monspessulana can compromise the natural multiplication of N. obliqua and its survival from its first phenological stages. This interdisciplinary study model facilitated the clarification of the plant-plant relationship mediated by allelochemicals. The model can be replicated to investigate other interspecific interactions between invasive and native species.

With a Little Help From My Friends: Hyperparasitism Allows a Generalist Mistletoe to Expand Habitat Use

Mistletoes largely vary in the number of species that they can parasitize. In the temperate rainforests of southern Chile, we found two mistletoe species: Tristerix corymbosus, a generalist species able to parasitize at least 30 plant species, and Desmaria mutabilis, which only parasitizes Nothofagus trees (that T. corymbosus is unable to parasitize). Nevertheless, we found some Nothofagus trees parasitized by T. corymbosus. How is this happening? We found that T. corymbosus parasitize D. mutabilis individuals, which are parasitizing Nothofagus trees. Such hyperparasitic relationship allows T. corymbosus to be present in Nothofagus-dominated forests, which otherwise will not be possible. Photo 1. Tristerix corymbosus flowering during the austral winter in the Nahuelbuta National Park, southern Chile. This mistletoe species flowers between March and October, being the main nectar source for hummingbirds during this period. Photo credit: Francisco E. Fontúrbel. Photo 2. Desmaria mutabilis flowering during the austral summer (January) in Nahuelbuta National Park. While its flowering period is relatively short (about 1 month), D. mutabilis flowers are intensely visited by pollinators, including hummingbirds and several kinds of insects. Photo credit: Francisco E. Fontúrbel. Photo 3. Desmaria mutabilis parasitizing a Nothofagus pumilio tree. The picture shows late flowers and some unripe fruits. Photo credit: Francisco E. Fontúrbel. Photo 4. Several Desmaria mutabilis mistletoes in an old-growth Nothofagus spp. forest stand at the Nahuelbuta National Park. Photo credit: Francisco E. Fontúrbel. Photo 5. A Tristerix corymbosus mistletoe parasitizing a Desmaria mutabilis individual, which is parasitizing a Nothofagus pumilio tree. Photo credit: Francisco E. Fontúrbel. These photographs illustrate the article “With a little help from my friends: Hyperparasitism allows a generalist mistletoe to expand habitat use” by Fontúrbel et al. published in Ecology. https://doi.org/10.1002/ecy.3919

Influence of environmental conditions and initial sapling size in Nothofagus survival and growth: Implications for restoration of burnt sub‐Antarctic forests

AbstractThe sub‐Antarctic forests in Tierra del Fuego mountains are considered one of the few remaining wilderness areas on the planet; however, human disturbances like wildfires, exotic species, and so forth exacerbate their degradation. In 2012, a human‐caused wildfire started in a remote forest‐mountain area, and 2 years after that, a reforestation project began to restore the natural canopy layer. Saplings of the native Nothofagus trees were obtained through the bare root method from undisturbed areas. In this study, we evaluated the influence of (1) macro‐ (considering natural topography and vegetation physiognomy) and micro‐environments (topography, canopy cover, substrate, and understory cover) affected by fire; and (2) the extraction size of the saplings (initial size), on survival and growth of planted saplings, over 5 years. Total sapling survival was 41.4% with a mean growth rate of 8.46 cm year−1. Survival and growth were influenced by the studied variables. At a macro‐environment level, tree saplings showed higher success in well‐drained zones, meanwhile at the micro‐environment level saplings performed better in those that contribute to retain soil moisture and avoiding evapotranspiration. We conclude that environmental features influence differentially depending on the scale of analysis. To restore burnt temperate forests applying the bare root method, we recommended using Nothofagus saplings <40 cm tall for better results. In this sense, we demonstrated the effectiveness of the method since comparable results were obtained in other restoration experiences. This method can also be applied in areas without nursery material, when the biology of tagged plants was appropriated, for example shallow growth of root systems, formation of natural tree seedling banks. This work represents one of the few medium‐term restoration experiences reported for the southernmost forests of the planet: our findings could be applied in other reforestation experiences, making noticeable improvements in the recovery process.

A saproxylic weevil acts as an ecosystem engineer: Impacts across multiple trophic levels

Although the degradation of dead trees plays an important role in biodiversity maintenance, only a few species of pioneer saproxylic beetles trigger their early degradation, thus acting as ecosystem engineers. Pioneer saproxylic beetles may be functionally more important when the properties of dead wood hinder its decay. In Patagonian rainforests, recently dead evergreen trees are massively colonized by a unique pit weevil species (Psepholax dentipes), while Nothofagus tree species host several pioneer beetle species. We evaluated if P. dentipes acts as an ecosystem engineer in evergreen trees only, positively affecting saproxylophagous beetles and Magellanic woodpeckers. We compared P. dentipes abundance between dead trees of evergreen and Nothofagus species. A causal model was used to test P. dentipes facilitation on woodpeckers and saproxylophagous beetles, while the foraging preferences of woodpeckers for trees colonized by P. dentipes were evaluated with zero-inflated models. Psepholax dentipes were more abundant in evergreen trees than in Nothofagus trees, in both cases affecting positively foraging woodpeckers. However, the positive P. dentipes effect on woodpeckers was stronger in evergreen trees than in Nothofagus trees, while a positive P. dentipes effect on saproxylophagous beetles was found only in evergreen trees. Woodpeckers selected trees with more holes of P. dentipes, but this effect weakened as trees became more decayed. Our results support the role of P. dentipes as ecosystem engineers in dead evergreen trees as they improve microhabitat conditions for saproxylophagous beetles and foraging woodpeckers, while serving as prey for woodpeckers.

Hanseniaspora smithiae sp. nov., a Novel Apiculate Yeast Species From Patagonian Forests That Lacks the Typical Genomic Domestication Signatures for Fermentative Environments.

During a survey of Nothofagus trees and their parasitic fungi in Andean Patagonia (Argentina), genetically distinct strains of Hanseniaspora were obtained from the sugar-containing stromata of parasitic Cyttaria spp. Phylogenetic analyses based on the single-gene sequences (encoding rRNA and actin) or on conserved, single-copy, orthologous genes from genome sequence assemblies revealed that these strains represent a new species closely related to Hanseniaspora valbyensis. Additionally, delimitation of this novel species was supported by genetic distance calculations using overall genome relatedness indices (OGRI) between the novel taxon and its closest relatives. To better understand the mode of speciation in Hanseniaspora, we examined genes that were retained or lost in the novel species in comparison to its closest relatives. These analyses show that, during diversification, this novel species and its closest relatives, H. valbyensis and Hanseniaspora jakobsenii, lost mitochondrial and other genes involved in the generation of precursor metabolites and energy, which could explain their slower growth and higher ethanol yields under aerobic conditions. Similarly, Hanseniaspora mollemarum lost the ability to sporulate, along with genes that are involved in meiosis and mating. Based on these findings, a formal description of the novel yeast species Hanseniaspora smithiae sp. nov. is proposed, with CRUB 1602H as the holotype.

The biogeography of Dromiciops in southern South America: Middle Miocene transgressions, speciation and associations with Nothofagus

The current distribution of the flora and fauna of southern South America is the result of drastic geological events that occurred during the last 20 million years, including marine transgressions, glaciations and active vulcanism. All these have been associated with fragmentation, isolation and subsequent expansion of the biota, south of 35°S, such as the temperate rainforest. This forest is mostly dominated by Nothofagus trees and is the habitat of the relict marsupial monito del monte, genus Dromiciops, sole survivor of the order Microbiotheria. Preliminary analyses using mtDNA proposed the existence of three main Dromiciops lineages, distributed latitudinally, whose divergence was initially attributed to recent Pleistocene glaciations. Using fossil-calibrated dating on nuclear and mitochondrial genes, here we reevaluate this hypothesis and report an older (Miocene) biogeographic history for the genus. We performed phylogenetic reconstructions using sequences from two mitochondrial DNA and four nuclear DNA genes in 159 specimens from 31 sites across Chile and Argentina. Our phylogenetic analysis resolved three main clades with discrete geographic distributions. The oldest and most differentiated clade corresponds to that of the northern distribution (35.2°S to 39.3°S), which should be considered a distinct species (D. bozinovici, sensu D’Elía et al. 2016). According to our estimations, this species shared a common ancestor with D. gliroides (southern clades) about ~13 million years ago. Divergence time estimates for the southern clades (39.6°S to 42.0°S) ranged from 9.57 to 6.5 Mya. A strong genetic structure was also detected within and between clades. Demographic analyses suggest population size stability for the northern clade (D. bozinovici), and recent demographic expansions for the central and southern clades. All together, our results suggest that the diversification of Dromiciops were initiated by the Middle Miocene transgression (MMT), the massive marine flooding that covered several lowlands of the western face of Los Andes between 37 and 48°S. The MMT resulted from an increase in global sea levels at the Miocene climatic optimum, which shaped the biogeographic origin of several species, including Nothofagus forests, the habitat of Dromiciops.

Surviving after an eruption: Ecosystem dynamics and mycorrhizae in Nothofagus pumilio forests affected by the 2011 Puyehue Cordón-Caulle tephra

Volcanic eruptions affect ecosystems drastically, and ectomycorrhizal fungi (EM) may play a critical role in forest regeneration. Nothofagus species are usually ectomycorrhizal. The 2011 Puyehue Cordón-Caulle volcanic complex (PCCVC) eruption covered vast areas of N. pumilio forests with thick tephra deposits. The main objectives of this work were to characterize the forest environment following tephra deposition, and to analyze the natural regeneration and development of N. pumilio and associated EM communities. Three study sites were selected and sampled two and three years after the PCCVC eruption. Two sites had a thick tephra layer (50 cm); in one of them most of the tree layer was dead (Highly Affected-Tephra) whereas in the other, most of the adult trees were alive (Affected-Tephra). The third site had minimal tephra deposition (Non-Affected). Physicochemical properties of the substrate, biological environmental factors and EM behavior of N. pumilio seedlings and adults were evaluated in all three sites. The physicochemical properties of the substrate and environmental characteristics differed among sites. Both seedlings and adults had EM in all three sites. The frequency of six-month-old seedlings with EM (40%) and their colonization values (<12%) were significantly lower in both tephra-affected sites than in the Non-affected site (100% and 80 %, respectively). However, all the 18-month-old seedlings from the tephra-affected sites had EM and their colonization increased almost to the value of the seedlings from the Non-Affected site. In both tephra-affected sites N. pumilio seedlings were associated with some exclusive fungal species, which could have a primary successional role. The early, increasing EM colonization recorded in seedlings after the eruption supports the idea of the strong dependence of Nothofagus trees on this symbioses, and highlights that this mutualism could be an effective adaptive mechanism under stressful conditions. Our findings also suggest that EM symbiosis in N. pumilio persists even after a severe disturbance and is regulated by several factors such as time after eruption, availability and type of mycorrhizal inoculum, plant development and physicochemical substrate composition.

Características del bosque asociadas a la ocurrencia del pulmonado endémico &lt;i&gt;Macrocyclis peruvianus&lt;/i&gt; (caracol negro) en la Región del Maule, Chile central

En muchos moluscos terrestres las relaciones entre su abundancia y las características de sus hábitats aún son poco conocidas. En este trabajo, se estudian las relaciones entre el tipo de vegetación y condiciones del micrositio donde habita el caracol terrestre endémico a Chile Macrocyclis peruvianus (caracol negro) en la Región del Maule, Chile central. Nuestros resultados indican que los bosques de Nothofagus alessandrii, árbol en peligro de extinción, así como los bosques higrófilos de la zona central de Chile, son hábitat de M. peruvianus resaltando la importancia de conservar este tipo de bosques para la supervivencia de este molusco.

A relic of the past: current genetic patterns of the palaeoendemic tree Nothofagus macrocarpa were shaped by climatic oscillations in central Chile

The Mediterranean-type forest of central Chile is considered a 'biodiversity hotspot' and a relic of a wider ancient distribution produced by past climatic oscillations. Nothofagus macrocarpa, commonly known as 'roble de Santiago', is a threatened palaeoendemic of this forest, poorly represented in the protected area system. This tree has been repeatedly misidentified as the sister species N. obliqua, which has affected its recognition and protection. Only a few populations of N. macrocarpa remain within a matrix of intensive land use that has been affected by recent forest fires. We tested the hypothesis that current populations of N. macrocarpa are a relic state of a previously widespread range, with the aim of contributing to its identification, its biogeographical history and the design of conservation measures using genetic information. We analysed remnant N. macrocarpa forests using nuclear (nDNA) and chloroplast DNA (cpDNA) sequences, conducted phylogenetic and phylogeographical analyses to reconstruct its biogeographical history, and assessed microsatellites [simple sequence repeats (SSRs)] to determine contemporary patters of diversity within and among all remnant populations. We also examined the degree of past, current and potential future isolation of N. macrocarpa populations using ecological niche models (ENMs). The species N. macrocarpa was confirmed by nDNA sequences, as previously suggested by chromosomal analysis. Small isolated populations of N. macrocarpa exhibited moderate to high genetic diversity according to SSRs. cpDNA analysis revealed a marked past latitudinal geographical structure, whereas analysis of SSRs did not find such current structure. ENM analyses revealed local expansion-contraction of the N. macrocarpa range during warmer periods, particularly in the northern and central ranges where basal-most cpDNA haplotypes were detected, and recent expansion to the south of the distribution. Genetic patterns confirm that N. macrocarpa is a distinct species and suggest a marked latitudinal relic structure in at least two evolutionarily significant units, despite contemporary among-population gene flow. This information must be considered when choosing individuals (seeds and/or propagules) for restoration purposes, to avoid the admixture of divergent genetic stocks.

Sapwood-inhabiting mycobiota and Nothofagus tree mortality in Patagonia: Diversity patterns according to tree species, plant compartment and health condition

Temperate forests ecosystems are threatened by declines and diseases worldwide. Causes have been investigated during the last decades allowing, in some cases, to relate such deterioration to climate change or pathogens but, in many cases, causes have not yet been elucidated. In recent decades, a phenomenon of grouped mortality, whose etiology remains unknown, has been observed in the two most distributed Nothofagus species of North Patagonian forests. This study aimed to assess sapwood-inhabiting fungal diversity of N. dombeyi and N. pumilio trees in healthy and affected stands in order to determine whether health condition shape these fungal communities, to characterize such patterns and, to seek for the likely pathogens associated with tree damage. Seven sites in Los Alerces National Park (Chubut, Argentina), were sampled seasonally for two years. Eighty-eight fungal taxa were recovered and identified. Spatial heterogeneity across plant compartments was found, involving community composition and structure, with stem harbouring greater diversity than root. It was found that the sapwood in both Nothofagus species was inhabited by different fungal species, in high richness and showing different patterns according to health condition and plant compartment. Health condition was a stronger driver of N. dombeyi sapwood-inhabiting fungal community than it was for N. pumilio; the latter evidenced plant compartment as a stronger driver of such community. Nothofagus pumilio presented higher frequency of decomposition agents in both affected and healthy trees than it was in N. dombeyi, indicating a greater wood deterioration of its stands. More decomposition agents and potential pathogens have been found in symptomatic stands of N. dombeyi than in healthy stands, although their frequency patterns do not allow the inference of conclusions about the primary fungal agent causing tree mortality. Our findings suggest a secondary role of living-wood-inhabiting mycobiota in tree damage processes as an expression of tree stress caused by climatic factors.

Initial response of understorey vegetation and tree regeneration to a mixed‐severity fire in old‐growth Araucaria–Nothofagus forests

AbstractQuestionsFire is a key factor influencing Araucaria araucana forests, but the impact of fire severity on the understorey vegetation is not well understood. In this study we seek to answer the following questions: (a) how do initial plant diversity, composition and spatial distribution of the understorey vegetation change in response to different levels of fire severity; and (b) does the abundance of dominant tree species exhibit different patterns across a fire severity gradient shortly after fire?LocationOld‐growth Araucaria araucana–Nothofagus pumilio forests in the Andes of south‐central Chile (38° S, 71° W) burned in 2015.MethodsWe evaluated the post‐fire plant regeneration across a fire severity gradient ranging from unburned forests to areas of high fire severity. One year after fire (in February 2016), we measured woody and herbaceous species richness, abundance, height, origin (native vs exotic species), life forms and the spatial pattern of plant recovery.ResultsPlant species richness and abundance were significantly higher within the unburned forest and low fire severity areas one year after fire, compared to areas of high and moderate fire severity. Overall, nearly 50% of the species present in the unburned forest were not found in areas of high severity, including the tree Nothofagus pumilio. Rapid vegetative resprouting of pioneer species such as Chusquea culeou resulted in an aggregated spatial distribution of plants after fire.ConclusionsPlant diversity and the abundance of Araucaria araucana and Nothofagus pumilio were reduced in areas of high fire severity one year after fire. Exotic species were more abundant within areas of low severity, being likely mediated by cattle browsing. Our research makes clear the potential changes in forest composition and structure if dominant tree species are not capable of recovering after fire. We recommend the exclusion of cattle within fire‐affected areas and planting Nothofagus pumilio in areas of high fire severity.

Species of accidental woody epiphytes vary between host trees in Tasmanian wet forests

Little is known about accidental epiphytes in Australian temperate forests. In western Tasmania, we determined whether: (1) the occurrence and abundance of accidental epiphytes increases with moisture availability and the size of host; (2) the species of host affects the occurrence of individual taxa of accidental epiphytes; (3) moist microhabitats favour accidental epiphytes. We recorded the accidental woody epiphytes on 21 trees in each of 20 locations and measured attributes of the host and the location and attachment height of the individual epiphytes. Epiphyte occurrence, but not abundance, was associated with the basal area of host tree, January rainfall and the taxon of the host. Eucalypts, gymnosperms and tree ferns were the outstanding hosts. The rainforest tree Nothofagus cunninghamii occurred as an epiphyte on eucalypts more than expected, while Proteaceae species occurred less than expected. In contrast, there was a strong positive association between the gymnosperm Athrotaxis selaginoides as a host and Proteaceae as epiphytes, possible reflecting their joint status as palaeoendemics. Accidental epiphytes were concentrated on the west and south-west of trees and near their bases, further indicating a strong effect of moisture availability on their occurrence. Our results reinforce the importance of conserving old growth forest to maintain ecosystem complexity.

Detecting Nothofagus pumilio Growth Reductions Induced by Past Spring Frosts at the Northern Patagonian Andes.

Extreme climatic events, such as late frosts in spring during leaf flush, have considerable impacts on the radial growth of temperate broadleaf trees. Albeit, all broadleaved species are potentially vulnerable, damage depends on the particularities of the local climate, the species, and its phenology. The impact of late spring frosts has been widely investigated in the Northern Hemisphere, but the potential incidence in Southern Hemisphere tree species is still poorly known. Here, we reconstruct spring frost occurrence at 30 stands of the deciduous tree Nothofagus pumilio in its northern range of distribution in the Patagonian Andes. We identified tree ring-width reductions at stand level not associated with regional or local drought events, matching unusual minimum spring temperatures during leaf unfolding. Several spring frosts were identified along the northern distribution of N. pumilio, being more frequent in the more continental Argentinean forests. Spring frost in 1980 had the largest spatial extent. The spring frosts in 1980 and 1992 also induced damages in regional orchards. Spring frost damage was associated with (i) a period of unusually warm temperatures at the beginning of leaf unfolding, followed by (ii) freezing temperatures. This study helps expand our understanding of the climatic constraints that could determine the future growth and dynamics of Andean deciduous forests and the potential use of tree-rings as archives of extreme events of spring frosts in northern Patagonia.

Early arboreal colonization, postglacial resilience of deciduous Nothofagus forests, and the Southern Westerly Wind influence in central-east Andean Patagonia

The history and dynamics of deciduous Nothofagus forests along the eastern slopes of the central Patagonian Andes (44°-49°S) remain insufficiently studied and understood, particularly at timescales ranging from centuries to millennia. Available fossil pollen records point to time-transgressive responses of the arboreal vegetation to climatic changes during the Last Glacial Termination (T1) and early Holocene, and spatial heterogeneity since then along north-south, east-west, and elevation transects. The degree to which these results represent biogeographic and climatic trends, varying environmental gradients, or site-specific phenomena has not been assessed in detail. Here we present a fossil pollen and macroscopic charcoal record from Lago Churrasco (45°41′S, 71°49′W), a small closed-basin lake located in the deciduous Nothofagus forest zone of the central-east Andes of Chilean Patagonia. Our results suggest that Nothofagus trees colonized newly deglaciated terrains at ∼16,000 cal yr BP and formed scrublands/woodlands several millennia earlier than reported by previous studies east of the Andes. This suggests expansion and local densification of tree populations sourced from the eastern margin of the Patagonian Ice Sheet during the Last Glacial Maximum, with the additional implication that temperature and precipitation conditions favorable for tree survival and reproduction developed early during T1. We posit that the amount of moisture delivered by the Southern Westerly Winds was not a limiting factor for arboreal expansion during T1 in this sector of the central Patagonian Andes. Closed-canopy Nothofagus forests established at ∼10,000 cal yr BP and have remained essentially invariant despite climate change and natural disturbance regimes. This resilience was challenged and exceeded by human disturbance during the 20th century through the use of fire, leading to deforestation and spread of invasive exotic species in an extraordinarily rapid event. Our record suggests a permanent influence of the Southern Westerly Winds over the last 10,000 years, with relatively modest variations at centennial and millennial timescales.

Ectomycorrhizal fungi and soil enzymes exhibit contrasting patterns along elevation gradients in southern Patagonia.

The biological and functional diversity of ectomycorrhizal (ECM) associations remain largely unknown in South America. In Patagonia, the ECM tree Nothofagus pumilio forms monospecific forests along mountain slopes without confounding effects of vegetation on plant-fungi interactions. To determine how fungal diversity and function are linked to elevation, we characterized fungal communities, edaphic variables, and eight extracellular enzyme activities along six elevation transects in Tierra del Fuego (Argentina and Chile). We also tested whether pairing ITS1 rDNA Illumina sequences generated taxonomic biases related to sequence length. Fungal community shifts across elevations were mediated primarily by soil pH with the most species-rich fungal families occurring mostly within a narrow pH range. By contrast, enzyme activities were minimally influenced by elevation but correlated with soil factors, especially total soil carbon. The activity of leucine aminopeptidase was positively correlated with ECM fungal richness and abundance, and acid phosphatase was correlated with nonECM fungal abundance. Several fungal lineages were undetected when using exclusively paired or unpaired forward ITS1 sequences, and these taxonomic biases need reconsideration for future studies. Our results suggest that soil fungi in N.pumilio forests are functionally similar across elevations and that these diverse communities help to maintain nutrient mobilization across the elevation gradient.