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The absence of co-evolved mutualists of plants invading a novel habitat is the logical corollary of the more widely recognized 'enemy escape'. To avoid or overcome the loss of mutualists, plants may co-invade with nonnative mutualists, form novel associations with native mutualists or form associations with native cosmopolitan mutualists, which are native but not novel to the invading plant. We tested these hypotheses by contrasting the ectomycorrhizal fungal communities associated with invasive Pinus contorta in New Zealand with co-occurring endemic Nothofagus solandri var. cliffortioides. Fungal communities on Pinus were species poor (14 ectomycorrhizal species) and dominated by nonnative (93%) and cosmopolitan fungi (7%). Nothofagus had a species-rich (98 species) fungal community dominated by native Cortinarius and two cosmopolitan fungi. These results support co-invasion by mutualists rather than novel associations as an important mechanism by which plants avoid or overcome the loss of mutualists, consistent with invasional meltdown.

1. Ecological memory, often determined by the extent and type of retained biological legacies present following disturbance, may produce persistent landscape patterns. However, after fire, the persistence or switch to an alternative state may depend on the complex interplay of ecological memory (biological legacies) and potential effects of new external factors influencing the post-fire environment. The current study assesses both the strength of ecological memory resulting from biological legacies of pre-burn vegetation types as well as post-fire effects of livestock. 2. Following a severe fire in 1999, we set up a network of long-term exclosures to examine the effects of legacies and cumulative herbivory by cattle on fuel types, amounts, distribution, flammability and microenvironmental conditions in two post-fire communities representing alternative firedriven states: pyrophobic Nothofagus pumilio subalpine forests and pyrophytic Nothofagus antarctica tall shrublands in northwestern Patagonia, Argentina. 3. Our results show that the retained post-disturbance legacies of tall shrublands and subalpine forests largely determine fuel and flammability traits of the post-fire plant communities 16 years after fire. The importance of biological legacies retained from the unburned plant communities was reflected by the substantially higher amounts of total fine fuel, greater vertical and horizontal fuel continuity and the higher temperatures reached during experimental tissue combustion at post-fire shrubland compared to post-fire forest sites. 4. We show that herbivores may produce antagonistic effects on flammability by decreasing tissue ignitability, total fine fuel and litter depth, and disrupting the vertical and horizontal fine fuel continuity, therefore reducing the probability of fire propagation. However, cattle can increase ratios of dead to live fine fuels, reduce soil moisture, and inhibit tree height growth to canopy size, consequently impeding the development of a closed pyrophobic forest canopy. 5. Synthesis. Our results support the hypothesis that biological legacies, most importantly the dominance by pyrophytic woody plants that resprout vigorously vs. the dominance by pyrophobic obligate seeders, favour fuel and flammability characteristics at the community level which reinforce the mechanisms maintaining pyrophytic shrublands vs. pyrophobic forests. Herbivory by introduced cattle can partially blur sharp pyrophobic/pyrophytic state boundaries by promoting the development of novel post-fire transitional states.

The Patagonian Forest Earthcreeper (Upucerthia saturatior) is a distinctive furnariid that inhabits the Patagonian forests of central-western Argentina and adjacent Chile within the Nothofagus Center of Endemism. After its description as a species in 1900, U. saturatior was quickly subsumed, without comment or study, as a subspecies of the Scale-throated Earthcreeper (U. dumetaria), a treatment followed by most subsequent authors. On the basis of an apparent geographical cline within U. dumetaria and a reanalysis of the morphology and plumage of reported intergrades between U. dumetaria and U. saturatior, there is no evidence of intergradation between these taxa. Upucerthia saturatior differs from U. dumetaria by its song ('p-p-tirik-tirik-tirik-tirik-tirik-tiruk' vs. 'pli-pli-pli-pli-pli . . .'), which is also three times faster in dumetaria, call ('pep' vs. 'keep'), morphology (smaller and darker with a short black bill vs. larger and paler with a long brown bill), distinctive tail pattern, breeding habitat (forest borders vs. shrubby steppe and open highland habitats), and migration patterns (trans-Andean vs. north-south). These differences exceed those between U. jelskii and U. albigula and are far greater than those between U. jelskii and U. validirostris; they overwhelmingly support ranking U. saturatior as a full species. The existence of a forest-dwelling species of Upucerthia parapatric to an open-country Upucerthia provides an opportunity for testing the role of habitat shift between dry exposed habitats and forest habitats (and vice versa) during speciation.

PurposePinaceae (pine family) trees are native to the Northern Hemisphere and their invasion into the Southern Hemisphere is a growing problem threatening biological diversity. Pinaceae are ectomycorrhizal (ECM) and their invasions are facilitated by non-native and co-invasive ECM fungi. Nothofagaceae species (southern beeches) are dominant overstory trees across large swaths of the Southern Hemisphere and are the only widespread ECM trees native to southern South America (SSA). This observational study investigates the in situ impact of Pinaceae invasions upon native soil fungi associated with Nothofagaceae hosts in SSA.MethodsWe performed soil nutrient testing and metabarcode sequencing of fungi in the rhizosphere of Nothofagus antarctica and Nothofagus dombeyi invaded by Pinaceae trees to determine whether co-invasive fungi might impact native soil fungi. Sampling transects extended from invasions into adjacent Nothofagus stands without invasive Pinaceae.ResultsThe fungal community composition of the Nothofagaceae rhizosphere was dominated by plant-associated Mortierellaceae OTUs in metabarcode data. Mortierellaceae OTU relative abundance was significantly reduced near invasions of Pinus contorta (Pinaceae). Invasions of Pseudotsuga menziesii (Pinaceae) and Pinus contorta were associated with reduced relative abundance of Nothofagus-associated ECM OTUS in the Nothofagus rhizosphere. Pinus contorta invasions were also associated with reduced soil organic matter, total carbon, total phosphorus, and total nitrogen.ConclusionFurther empirical study is warranted to investigate the hypothesis that Mortierellaceae and Pinaceae-specific /suillus-rhizopogon ECM fungi compete for nutrients bound in soil organic matter. Such competition may have potential long-term legacy effects upon post-invasion restoration efforts and implications for Pinaceae invasions globally.

Background Climate change projections for western Patagonia, Argentina, predict a 1–3 °C increase in air temperature and a 10–30% reduction in precipitation by the end of this century, which will probably lead to more frequent and intense forest wildfires. Nothofagus are dominant tree species in Andean-Patagonian Forests ecoregion and are known to form symbiotic associations with ectomycorrhizal fungi (EcM). Forest fires threaten EcM, which play a critical role in ecosystem structure and functioning. In this study, we evaluated the impact of recent wildfires in Nothofagus forests on the taxonomic and functional diversity of soil fungi, with emphasis on EcM. Specifically, we aimed to identify fire-resistant fungal species that may contribute to forest restoration programs. To this end, we collected 151 composite soil samples from five paired burned and unburned (control) plots and assessed alpha and beta diversity responses to wildfires based on environmental DNA (eDNA) analysis. Results Soil fungi species richness was negatively affected by the interaction of wildfire with soil pH and nitrogen content. In contrast, Shannon’s index and Inverse Simpson’s index were positively influenced by wildfires, with calcium, phosphorus, and organic carbon of soil showing significant interactions. EcM species richness was negatively affected by wildfire, whereas diversity indices increased. In the soil fungal community, wildfire led to species turnover, whereas in the EcM community wildfire promoted a nestedness associated with species loss. Additionally, representative operational taxonomic units (OTUs), including Cortinarius sp. and Lyophyllum sp. were primarily associated with burned plots, suggesting their tolerance to wildfire disturbance. Conclusions In the fungal soil community, wildfire appeared to reduce species richness, while increased evenness, and species replacement. In contrast, the EcM community was largely lost, persisting as a reduced subset of pre-existing taxa. Active forest restoration through the inoculation of seedlings with native fire-tolerant EcM species could enhance tree establishment, growth, and survival in post-fire environments.

Aim: To determine the soil characteristics of Nothofagus-dominated rain forests in an ultramafic region (i.e. soils having high concentrations of metals including Mg, Fe and Ni), and whether soil characteristics may explain the location of monodominant rain forest in relation to adjacent mixed rain forest and maquis (shrub-dominated vegetation). Location: New Caledonia. Methods: Soil characteristics were compared among six Nothofagus-dominated rain forests from a range of altitudes and topographic positions. At four of these sites, comparisons were made with soils of adjacent mixed rain forest and maquis. Results: Soil characteristics varied among the monodominant Nothofagus forests, largely due to differences between ultramafic soils and soils influenced by non-ultramafic intrusions. The soils of all vegetation types had low concentrations of nutrients, particularly P, K and Ca (both total and extractable/exchangeable), and high total concentrations of Ni, Fe, Cr and Mn. There were significant differences between the rain forests and adjacent maquis in soil concentrations of several elements (N, P, Ca, Mg and Mn), more so in surface soils than at depth, but much of this pattern may be caused by effects of vegetation on the soil, rather than of soil on the vegetation. However, there were no significant differences in soil concentrations of any mineral elements between Nothofagus forest and adjacent mixed rain forest. Main conclusions: We found no evidence for soil mediation of boundaries of Nothofagus rain forest with mixed rain forest, and little evidence for the boundaries of either forest type with maquis. We suggest that the local abrupt boundaries of these monodominant Nothofagus forests are directly related to temporal factors, such as time since the last wildfire and frequency of wildfire, and that disturbance is therefore a major causal factor in the occurrence of these forests.

BackgroundTree regeneration is a key component of resilience because it promotes post-disturbance recovery of forests. Northwestern Patagonia from Argentina is occupied by Nothofagus alpina (Na), N. obliqua (No), and N. dombeyi (Nd) forests that grow along an intense precipitation gradient, managed throughout shelterwood silvicultural system by technicians of the Lanin Natural Reserve. The objective of this study was to evaluate the influence of seeding cuttings over the dynamics of Nothofagus mixed forests across landscape (precipitation gradient) based mainly on the composition and abundance of tree regeneration, permanent sampling plots and generalized linear mixed models. In particular, we analysed: (i) the structure of sexual and asexual regeneration during < 10, 10–20 and > 20 years after harvest (the dynamics of managed forests), and (ii) the structure of sexual regeneration in primary and managed forests after > 20 years of harvest (the effect of silviculture).ResultsNd was the most abundant species in the regeneration of managed forests during all periods in both sites despite its lower contribution to the adult cohort. During the 10–20 years period after harvest, the humid site exhibited higher regeneration density than the mesic site (120,000 and 6000 ind ha−1, respectively), and it decreased afterwards. The number of established regeneration (> 2 m height) was lower for Na in the mesic site and for No in the humid site (0 and 57 ind ha−1, respectively). However, in comparison to No, Na showed a higher number of sprouted stumps and sprouts per stump, and a higher sprout height in the mesic site. No exhibited higher sprout mortality in the humid site. Finally, the regeneration of primary forests showed lower density and height, and a more balanced composition than that of managed forests.ConclusionsThe silvicultural effects on the mixed forest regeneration dynamics was strongly influenced by the condition of sites. Therefore, management prescriptions should be adjusted in order to consider the environmental variation occurring through the entire landscape. An adaptive management that considers the pattern and process of sexual and asexual regeneration and disturbance will contribute to promote a greater resilience of mixed forest ecosystems.

Infrequent, high-intensity disturbances can have profound impacts on forested landscapes, changing forest structure and altering relative species abundance. However, due to their rarity and the logistical challenges of directly observing such extreme events, both the spatial variability of disturbance intensity and the species-specific responses to this variability are poorly understood. We used observed patterns of mortality across a fire severity gradient following the 2009 Black Saturday fires in southeastern Australia to simultaneously estimate (1) species- and size-specific susceptibility to fire-induced mortality and (2) fire intensity. We found broad variation in patterns of fire susceptibility among the 10 tree species (five eucalypts and five non-eucalypts) sufficiently abundant for analysis. Among the eucalypts, Eucalyptus obliqua was the most resistant to fire-induced mortality, with trees of ~25 cm DBH having a 50% probability of surviving even the most intense fires. In contrast, E. regnans had 100% mortality across all size classes when subjected to high-intensity fire. Basal resprouting occurred in six of the study species and, when accounted for, fundamentally changed the mortality profile of these species, highlighting the importance of resprouting as an adaptation to fire in these landscapes. In particular, the two iconic cool temperate rainforest species (Nothofagus cunninghami and Atherosperma moschatum) were strong resprouters (~45% of individuals were able to resprout after being top-killed by fire). We also found evidence for compositional shifts in regeneration above threshold values of fire intensity in cool temperate rainforest and mixed forest sites, both of which have important conservation values within these landscapes. The observed patterns of species- and size-specific susceptibility to fire-induced mortality may be used to anticipate changes in forest structure and composition in the future. In addition, they may also help guide forest management strategies that reduce the length of time individual trees are exposed to potentially lethal fires, thereby increasing the resilience of these forests to future fires.

Mortality patterns were analyzed in a one-year old Nothofagus dombeyi plantation at mid-elevation in the Chilean Andes. Ripley's univariate function was used to detect spatial patterns of mortality and damage (as reflected in crown dieback) of seedlings by assigning them into four categories: no crown damage, 1/3 of the crown damaged, 2/3 of the crown damaged and dead. Through correspondence analysis, variables (plant attributes, topography, weed competition, neighboring vegetation and fertilization) that could affect mortality were tested. At the end of the first growing season 67% of the seedlings survived, and by the end of the following dormant season only 37% were alive. Mortality patterns were random for seedlings with 1/3 of the crown damaged, and clustered for all other categories. Environmental variables with the greatest influence on mortality were increasing distance to a neighboring 10m tall plantation, absence of tall vegetation cover and convex micro-topography. Results suggest that large temperature oscillations with events of freezing temperatures (defined as the reported lethal temperature for 50% of its leaves) during the growing season, and severe frost during the dormant season, were the main causes of mortality and damage. The convenience of providing seedlings with some shelter when outplanted, or with an appropriate cold-acclimation treatment to resist low freezing temperatures when outplanted in open fields in harsh cold regions of the south-central Andes is discussed.

The objective of the study was to estimate the diameter at different stem heights and the tree volume of the Nothofagus obliqua (Mirb.) Oerst., Nothofagus alpine (Poepp. et Endl.) Oerst. and Nothofagus dombeyi (Mirb.) Oerst. trees using artificial neural networks (ANNs) and comparing the results with estimates obtained from six traditional taper functions. A total of 1380 trees were used. The ANN trained to estimate the stem diameter with the best performance generated RMSE values in the training phase of 7.5%, and 7.7% in the validation phase. Regarding taper functions, Kozak’s model generated better RMSE indicators, but performed not as well as that generated by the ANN. The ANN estimation of the total volume was carried out in two phases. The first used the diameter estimation to determine the volume at one-centimeter intervals along the stem (one-phase ANN), and the second used the estimation of the one-phase ANN as an additional variable in an ANN that directly estimated the tree cumulative volume (two-phase ANN). The two-phase ANN method generated the best performance for estimating the cumulative volume in relation to one-phase ANN and the Kozak taper function, generating RMSE values for N. obliqua, N. alpina and N. dombeyi of 9.7%, 8.9% and 8.8%, respectively.