Pumilio Forests Research Articles

Genetic diversity and population structure in Nothofagus pumilio, a foundation species of Patagonian forests: defining priority conservation areas and management

Patagonian forests are the southernmost temperate forests in the world, and Nothofagus pumilio is one of their most ecologically important tree species (i.e., a foundation species). It presents great adaptability and a wide distribution range, making it a suitable model for predicting the performance of trees facing global climate change. N. pumilio forests are increasingly threatened by extreme climatic events and anthropogenic activities. This study aims to identify priority conservation areas and Genetic Zones (GZs) for N. pumilio, promoting the implementation of specific practices to ensure its management and long-term preservation. Thirty-five populations (965 trees) sampled across its distribution (more than 2200 km latitudinally) were genotyped with SSRs, and geographical patterns of genetic variation were identified using Bayesian approaches. The phylogeographic patterns of the species and geomorphological history of the region were also considered. Six priority conservation areas were identified, which hold high allelic richness and/or exclusive allelic variants. Eighteen GZs were delineated based on the genetic structure of this species, and maps showing their distributional range were drawn up. Overall, this study defines management units based on genetic data for N. pumilio for the first time, which will facilitate the establishment of sustainable practices and highlight priorities for investment of conservation funding.

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.

Tree-growth at the rear edge of a Nothofagus pumilio Andean forest from Northern Patagonia show different patterns and a decline in the common signal during the last century

Nothofagus pumilio is the dominant tree species at high elevations in the southern Andes between 35° and 55° S. Despite the number of tree-growth studies on this tree species, there is scarce information about the growth patterns and its relation with climatic variability at its lower elevation margin of distribution in the windward side of the Andes. In this study we focus on the altitudinal rear edge of a N. pumilio forest growing on the Pacific side of the northern Patagonian Andes to determine the main temporal patterns of tree radial growth, identify its relations with regional and large-scale climate and to assess the temporal variation of common signal in tree growth at centennial time-scales.A Principal Component Analysis (PCA) between trees for their common period 1850–2010 indicates the existence of more than one pattern of tree growth within this lower altitudinal margin, which exhibit contrasting relations with climate. The tree ring chronology and the PC1 amplitude of tree growth shows negative correlation with maximum temperature during spring-summer while the PC2 shows the contrary. Maps and correlation functions indicate that the PC1 and PC2 patterns of N. pumilio growth are significantly related with high latitude climate variability induced by the Antarctic Oscillation (AAO) during spring-summer in an opposite manner, with the PC1 (PC2) negatively (positively) correlated with the poleward displacement of the storm tracks driven by the mid- and high-latitude dipole pressure in the Southern Hemisphere. The running PCA between the standardized tree ring-width series shows a decreasing trend in the percentage of variance explained by the first mode of tree growth, indicating a centennial scale loss in the common signal of growth within the population, especially since mid-20th century when the behavior of the AAO was unprecedented within the context of the last millennium.Given that the future climatic scenario for northern Patagonia as predicted by models would led to more arid conditions forced by the positive trend of the AAO, we expect that the main pattern of N. pumilio growth at the rear edge of Choshuenco volcano will be negatively affected. Despite the present knowledge about N. pumilio radial growth in treeline environments, specific research is needed to gain insights about the complexity of the climate-growth relationship at its low elevation margin, in order to evaluate anomalies in tree growth patterns in the habitat where N. pumilio grows and competes with other low elevation species more tolerant to warmer conditions.

Ground-dwelling spiders and understory vascular plants on Fuegian austral forests: Community responses to variable retention management and their association to natural ecosystems

Variable retention mitigates negative effects of traditional harvesting on biodiversity, maintaining legacies in harvested forests as habitat for sensitive species, and generating other habitats for early-seral species. Their assessment, including drivers, has a high concern for society. Likewise, species association with ecosystems in the landscape (as different forest types, grasslands and peatlands) are unknown for some taxa and regions, and could explain species flow into harvested areas. Therefore, we evaluated the forest harvest impact on ground-dwelling spiders and vascular plants, their diversity and association to vegetation types in the landscape matrix, and richness and abundance correlations with forest structure. Six natural common habitats were studied in Tierra del Fuego (Argentina), where variable retention has been implemented: aggregated (AR) and dispersed (DR) retention in harvested Nothofagus pumilio forests, unharvested primary forests (NPF) as reference, grasslands (G), peatlands (P), and unharvested N. antarctica forests (NAF). We surveyed spiders (N = 432, by 6 habitats × 6 replicates × 6 collections × 2 years), and vascular plants (N = 36, by 6 habitats × 6 replicates), and characterized forest structure in wooded ecosystems. We determined for both taxa richness, relative abundance (total captures/ground cover) and Shannon-Wiener and Pielou indices, compared assemblage composition and indicator species among harvesting treatments and vegetation types, and analyzed correlations. We sampled 752 individuals of spiders from 33 species (six families), and 79 vascular plant species (28 families) that averaged 52% total vegetation cover. Total spider captures and overall richness were higher in DR > NPF > AR, although differences were not detected at plot level for any variable. For understory vascular plants, richness and cover were the highest on DR, followed by AR and NPF, as well as at plot level, with no affectation in indices. Likewise, highest richness and abundance occurred in NAF and NPF for spiders, and in NAF and G for vascular plants, with unique assemblages in each vegetation type despite the shared species. Assemblages also differed in harvested areas, including species of other vegetation types mainly in DR, where new conditions were generated by reduction of forest structure variables (evidenced by negative correlations), while AR maintained species composition similar to NPF, contributing to the conservation of forest specialists. Indicators occurred for both taxa in several habitats. This study highlights the importance of different vegetation types for spider and plant conservation at landscape level, while provides tools for developing monitoring strategies and conservation policies.

Influencia del paisaje en las cortas de protección en bosques de Nothofagus pumilio en Tierra del Fuego, Argentina: Cambios en la estructura forestal y respuesta de la regeneración

During the last thirty years, shelterwood cuts has been the most applied regeneration method in Nothofagus pumilio (lenga) forests. This treatment was implemented without any consideration of the landscape, and without considering yield gradients (e.g. stand site qualities), environmental restrictions (e.g. soil water availability) or potential natural disturbance factors (e.g. wind exposure). The objective was to evaluate the dynamics of the remnant forest structure and the natural regeneration 10 years after harvesting across the landscape considering different environmental gradients. Sampling plots were established in nine stands distributed across Tierra del Fuego, Argentina (north, east and south areas) where forestry activity has been concentrated during the last years. The selected areas presented differences in the rainfall regime (402 to 446 mm yr-1) and site qualities of the stands (2.6 to 3.3). Forest structure was similar among the studied areas, nevertheless harvesting intensity was variable (30 % to 57 %) generating different remnant basal areas (BA) (22 to 47 m² ha-1) and woody debris accumulation in the forest floor (167 to 230 m³ ha-1) after harvesting, or in combination with local wind-throws. The current forest structure presented differences in BA (6 to 34 m² ha-1) and established regeneration (49 to 110 thousand ha-1) that varied in height (0.6 to 1.0 m) and growth (4.1 to 12.8 cm yr-1) according to the area and the received damage due to abiotic and biotic factors. We can conclude that forests located along the considered landscapes and environmental gradients differentially responded to the proposed silvicultural treatments, where climate influenced over the post-harvest canopy stability and the established regeneration. For this, it is mandatory to define different silvicultural strategies throughout the landscape.

Performance of different logging systems in the shelterbelt cutting of the Nothofagus pumilio forest in America

Nothofagus pumilio forests constitute the most economically important forest stand in southern Argentina and Chile. Total volume stocking and volumetric yield vary according to site quality, degree of occupation, growth stage and forest history of the stand. The objective of this work was to evaluate the stocking and the productive potential in quantity and quality of products for the sawmilling industry, using three harvesting systems (short logs, long logs and complete shafts) in the protection cut of a N. pumilio forest of site quality III in Tierra del Fuego (Argentina). The trials were conducted in an irregular mature forest with two strata and abundant regeneration (3.0 ha; RDI 93.8–113.4%). Total volumes varied between 726.5 and 850.3 m3∙ha-1, with a volume/basal area ratio of 11.8 to 12.1 m3∙m-2. The harvesting rates obtained were: 45.5% for complete logs, 21.3% for long logs and 22.4% for short logs. A model was used to estimate the timber volume for each system, where full shafts resulted in a significant increase in timber volume. Considering new alternatives in the planning of harvesting in forest management for N. pumilio forests, such as the system of complete shafts, allows obtaining higher harvesting rates, increasing the benefits for the forestry company and minimizing the damage to the forest, due to the shorter distance of the machinery in the forest harvesting.

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.

Disturbance History and Dynamics of an Old-Growth Nothofagus Forest in Southern Patagonia

The identification of disturbance events using disturbance chronologies has become a valuable tool in reconstructing disturbance history in temperate forests worldwide; yet detailed reconstructions of disturbance history and their effect on the structure and dynamics of the old-growth Nothofagus forests in the southern Patagonia are scarce. We reconstructed forest dynamics and disturbance history of an old-growth N. pumilio forest in the Toro River Valley, Santa Cruz, Argentina using dendroecological techniques. Since a variation in the disturbance regimes was expected with changing elevation, we sampled at different elevations. We found distinct differences in forest structure, dynamics, and disturbance history with changes in the elevation. The disturbance chronologies provided robust evidence that forests in the study area have been subjected to multiple disturbance events over the last 200 years. Yet, recognizing the agent of disturbance could be difficult in these montane forests and further studies are required. Moreover, disturbances might have varied from frequent, moderate- to high-severity events to less frequent and more severe events. This study represents the first of its kind for the temperate forests of Patagonia.

Strengthening mycorrhizal research in South America.

Strengthening mycorrhizal research in South America.

Recovery of understory assemblage along 50 years after shelterwood cut harvesting in Nothofagus pumilio Southern Patagonian forests

Harvesting modifies the understory due to changes in the overstory structure, microclimate and soil properties. The impact is directly related to the harvesting intensity, although studies are usually developed in logged areas (low impact) avoiding stockpiled areas (high impact). Understory resilience is quite variable, and recovery time remains unknown for different management practices and different temperate forests. The objectives of this work were: (i) to evaluate recovery of understory vascular plants and forest structure in Nothofagus pumilio forests of South Patagonia (Argentina) along a chronosequence of years-after-harvesting (YAH) (1–5, 6–10, 20–30, >50) in shelterwood cuts compared to unharvested forests (UF), and (ii) to analyze differences in the understory recovery in areas with different impact intensity due to the harvesting: low impact harvesting (LIH) in logged areas vs. high impact harvesting (HIH) in stockpiled areas. We selected 12 harvested areas with different YAH, and in each area we sampled three forest treatments (LIH, HIH, UF) with 5 replicas (N = 12 × 3 × 5 = 180). In each sampling unit we analyzed the forest structure (primary or remnant overstory and secondary forests), environmental (soil moisture) and understory variables (richness, cover and species assemblage patterns) through univariate and multivariate statistical analyses. Remnant forest structures presented significant decay in the dominant height along the chronosequence, and an increasing in the secondary forest variables, as well as in the crown cover (remnant + secondary forests). Lower values of forest structure variables were observed in HIH than LIH, but without significant differences between them. Most of treatment levels presented significant differences with UF, and values become similar with time. Understory presented significant differences in richness and cover along the chronosequence, with values become more similar to UF on time. Harvesting impact levels also presented differences, e.g. 104% and 144% more exotic species cover in LIH and HIH compared with 20% in UF. However, greater significant differences were found among treatments for their species assemblage patterns, mainly in the first stages of the chronosequence (e.g., between UF and LIH at 6–10 YAH); meanwhile in the last stage (>50 YAH), species assemblage patterns become similar with UF, both for LIH and HIH. We conclude that understory vascular plant assemblage of N. pumilio forests recovers patterns after 50 YAH, being more similar to original ones as the crown cover reaches similar values to unharvested forests, showing N. pumilio forests as highly resilient to shelterwood cut harvesting, even in high impacted areas.

Soil mycobiota under managed and unmanaged forests of &lt;i&gt;Nothofagus pumilio&lt;/i&gt; in Tierra del Fuego, Argentina

Background: Management practices can modify the productivity of forests and the associated microbial diversity of soil. The soil mycobiota is considered a key factor in the ecological functions of forests. Forests of Nothofagus pumilio (Poepp. &amp; Endl.) Krasser (Nothofagaceae) are the main source of timber and one of the most important economic resources in the province of Tierra del Fuego (Argentina). However, there is no information on the impact of forest management interventions for the soil mycobiota, which can be reliable biological indicators of disturbance.Methods: Fungi were isolated from samples of soil collected under several Nothofagus pumilio forests subjected to different types of management and periods of time since the intervention. Types of management were represented by harvested forest with a shelter wood cutting, stockpile area and control forest without intervention and the periods of time since intervention were 1, 5–10 and 50 years. Species richness, evenness and Shannon’s diversity index of the mycobiota in each condition of management were calculated. Additionally, the effect of seasonality was analysed.Results: The soil mycobiota was represented by 70 taxa. Richness and/or Shannon’s diversity index of the mycobiota between undisturbed forest and stockpile area were higher in May (autumn) than in September or November. There were no differences in mycobiota diversity between dates in the harvested forest.Conclusions: Our results indicate that the forest intervention per se did not negatively affect the soil culturable mycobiota composition of N. pumilio forests in Tierra del Fuego (Argentina).

Twelve-year dynamics of alien and native understorey plants following variable retention harvesting in Nothofagus pumilio forests in Southern Patagonia

Disturbances have frequently been shown to increase the invasibility of plant communities. Harvesting, the most common and severe type of anthropogenic disturbance in forests, creates pulses of enhanced resource availability for alien plants and for native colonizers. However, it is unclear for how long initial changes in species composition of the understorey persist after harvesting. Using annually surveyed permanent plots (n = 72 plots across six stands), we analysed temporal changes of plant understorey composition of Patagonian Nothofagus pumilio forests during 12 years under three different conditions created by variable retention harvesting: retained forest patches (aggregates) of 30 m radius in a density of one patch ha−1 (AR), dispersed retention within the influence of the aggregate (DRI), retained dispersed single trees (DR); and primary unharvested forests as control (PF). Our results show that: (i) cover of native forest species in the understorey declined only very slowly in AR, but alien species cover increased strongly and became dominant nine years after harvesting (YAH); (ii) DR and DRI supported higher cover of alien species in the understorey than AR and PF, and alien species became dominant two to three YAH. Yet, they started to decline following a peak at eight YAH; (iii the cover of native forest species in the understorey was high in the beginning but alien species became dominant in DR and DRI after four and seven YAH, respectively. Tree regeneration significantly influenced understorey dynamics, i.e. (iv) in DR, a negative relationship with alien species cover, and a positive relationship with native colonizers from other habitats; (v) in DR and in DRI, this relationship was negative with alien species richness; (vi) in DRI, it was positive with native colonizers from associated environments (cover and richness). We conclude that alien plants invade Patagonian forests after harvesting, but decline with time when tree regeneration is established. Our results highlight the role of harvesting in facilitating plant invasions in forests, and how the spatio-temporal trajectories of such invasions are influenced by different levels of disturbance created by harvesting according to the position within the resultant matrix.

Land sharing in South Patagonia: Conservation of above-ground beetle diversity in forests and non-forest ecosystems

Land-sharing strategies, as variable retention silvicultural proposals, are useful to mitigate harmful effects of economic activities on forest biodiversity; benefits have been reported worldwide for several organisms. However, we suggest that this approach could be useful to improve beetle conservation not only in forests but also in other ecosystem types, based on the results from Southern Patagonia (Argentina). We studied above-ground beetle communities using pitfall traps in Nothofagus pumilio forests, Mulguraea tridens shrublands, and magellanic steppes. The forests were located in Tierra del Fuego Province, while the shrublands and the steppes were in Santa Cruz Province. In forests and shrublands, we compared retention approaches (aggregated/dispersed retention harvesting in forests, and managed cut and retention strips in shrublands) vs. control situations (without harvesting/cuttings). In dry and humid steppes, both impacted by livestock, we evaluated grazed and exclusion paddocks, comparable to structural retentions (reference areas without grazing do not exist). Richness, abundance, frequency, Shannon-Wiener diversity and Pielou evenness indices, and similarity among assemblages were evaluated using univariate and multivariate statistical tests. In forests and shrublands, retention approaches (aggregated/dispersed and strips) allowed the partial or total maintenance of beetle community richness, preserving them similar to natural and non-impacted ecosystems. In dry and humid steppes, exclusion areas presented significantly different richness, abundance and diversity of arthropod assemblages, but with inverse trends: lower values in grazed areas than in exclusions in dry steppe, and higher values in grazed areas than in exclusions in humid steppe. We concluded that land-sharing could be implemented in forests and non-forest ecosystems to preserve beetle communities, being the variable retention approaches and the grazing exclusion areas good alternatives for private or public lands. Likewise, we consider that legislation to promote conservation (like National Law 26331) should not be only applicable for and implemented in forests, but also in non-forest ecosystems.

Suitable conditions for natural regeneration in variable retention harvesting of southern Patagonian Nothofagus pumilio forests

BackgroundVariable retention (aggregated and dispersed retention) harvesting proposed for Nothofagus pumilio was designed for timber purposes and biodiversity conservation. Harvesting by opening canopy generates different microenvironments and creates contrasting conditions for seedling establishment, growth, and eco-physiology performance due to synergies (positives or negatives) with biotic and abiotic factors. This study evaluated the regeneration in different microenvironment conditions within managed stands during 5 years after harvesting. Remnant forest structure after harvesting and different microenvironments were characterized in managed stands, where 105 regeneration plots were measured (3 stands × 7 microenvironments × 5 replicas). We characterized the seedling bank, as well as growth and ecophysiology performance of the regeneration. Univariate and multivariate analyses were conducted for the comparisons.ResultsMicroenvironments offered different environmental conditions for natural regeneration (soil moisture and light availability). Seedling under debris and dicot plants showed better eco-physiological performance, establishment, and growth than plants growing under monocots or located in the dispersed retention without the protection of other understory plants. The most unfavorable microenvironment conditions were high canopy cover of remnant trees (inside the aggregates or close to trees in the dispersed retention) and heavily impacted areas (skidder extraction roads).ConclusionsFavorable microenvironments in the harvested areas will improve the natural recruitment, growth, and eco-physiology performance of the natural regeneration after harvesting. It is necessary to develop new silvicultural practices that decrease the unfavorable microenvironments (e.g., road density or excessive woody accumulation), to assure the success of the proposed silvicultural method.

Radial Growth Patterns Associated with Tree Mortality in Nothofagus pumilio Forest

Tree mortality is a key process in forest dynamics. Despite decades of effort to understand this process, many uncertainties remain. South American broadleaf species are particularly under-represented in global studies on mortality and forest dynamics. We sampled monospecific broadleaf Nothofagus pumilio forests in northern Patagonia to predict tree mortality based on stem growth. Live or dead conditions in N. pumilio trees can be predicted with high accuracy using growth rate as an explanatory variable in logistic models. In Paso Córdova (CO), Argentina, where the models were calibrated, the probability of death was a strong negative function of radial growth, particularly during the six years prior to death. In addition, negative growth trends during 30 to 45 years prior to death increased the accuracy of the models. The CO site was affected by an extreme drought during the summer 1978–1979, triggering negative trends in radial growth of many trees. Individuals showing below-average and persistent negative trends in radial growth are more likely to die than those showing high growth rates and positive growth trends in recent decades, indicating the key role of droughts in inducing mortality. The models calibrated at the CO site showed high verification skill by accurately predicting tree mortality at two independent sites 76 and 141 km away. Models based on relative growth rates showed the highest and most balanced accuracy for both live and dead individuals. Thus, the death of individuals across different N. pumilio sites was largely determined by the growth rate relative to the total size of the individuals. Our findings highlight episodic severe drought as a triggering mechanism for growth decline and eventual death for N. pumilio, similar to results found previously for several other species around the globe. In the coming decades, many forests globally will be exposed to more frequent and/or severe episodes of reduced warm-season soil moisture. Tree-ring studies such as this one can aid prediction of future changes in forest productivity, mortality, and composition.

Potential biodiversity map of understory plants for Nothofagus forests in Southern Patagonia: Analyses of landscape, ecological niche and conservation values

The role of understory plants in native forests is critical for ecosystem function, wildlife protection and ecosystem productivity. The interest to estimate biodiversity increased during the last decades at landscape level. The objective was to elaborate a map of potential biodiversity (MPB) of understory species of Nothofagus forest using potential habitat suitability maps (PHS) of 15 plants in Santa Cruz province, Argentina. Additionally, we asked the following questions: (i) Were plant species differentially distributed according to the forest types?, (ii) do forest types represent different plant species assemblage with specific ecological niche requirements?, and (iii) is it possible to detect hotspots in the MBP according to the forest types? We used 721 plots database of vascular plants, from where 15 indicator species were identified. The assemblage species for different forests (Nothofagus antarctica, N. pumilio and evergreen mixed) were analysed using a detrended correspondence analysis. Also, we explored 41 potential explanatory variables to develop PHS, and combined these maps to obtain one MPB (1–100%). Finally, we analysed the outputs into a GIS through different landscapes alternatives to detect hotspot areas. Marginality and specialization values allowed identifying species assemblage that presented similar variability in the habitat requirements. MPB varied across the landscape, with higher values in the south and lower values near glaciers. MPB had the highest values in N. antarctica forest with >50% cover at landscape level. N. antarctica present more hotspots than N. pumilio forests, mainly in the south, compared to mixed evergreen forests which present few hotspots near glaciers. These results can be used as a tool to design new management and conservation strategies at landscape level.

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.

A Self-Calibrated Non-Parametric Time Series Analysis Approach for Assessing Insect Defoliation of Broad-Leaved Deciduous Nothofagus pumilio Forests

Folivorous insects cause some of the most ecologically and economically important disturbances in forests worldwide. For this reason, several approaches have been developed to exploit the temporal richness of available satellite time series data to detect and quantify insect forest defoliation. Current approaches rely on parametric functions to describe the natural annual phenological cycle of the forest, from which anomalies are calculated and used to assess defoliation. Quantification of the natural variability of the annual phenological baseline is limited in parametric approaches, which is critical to evaluating whether an observed anomaly is “true” defoliation or only part of the natural forest variability. We present here a fully self-calibrated, non-parametric approach to reconstruct the annual phenological baseline along with its confidence intervals using the historical frequency of a vegetation index (VI) density, accounting for the natural forest phenological variability. This baseline is used to calculate per pixel (1) a VI anomaly per date and (2) an anomaly probability flag indicating its probability of being a “true” anomaly. Our method can be self-calibrated when applied to deciduous forests, where the winter VI values are used as the leafless reference to calculate the VI loss (%). We tested our approach with dense time series from the MODIS enhanced vegetation index (EVI) to detect and map a massive outbreak of the native Ormiscodes amphimone caterpillars which occurred in 2015–2016 in Chilean Patagonia. By applying the anomaly probability band, we filtered out all pixels with a probability &lt;0.9 of being “true” defoliation. Our method enabled a robust spatiotemporal assessment of the O. amphimone outbreak, showing severe defoliation (60–80% and &gt;80%) over an area of 15,387 ha of Nothofagus pumilio forests in only 40 days (322 ha/day in average) with a total of 17,850 ha by the end of the summer. Our approach is useful for the further study of the apparent increasing frequency of insect outbreaks due to warming trends in Patagonian forests; its generality means it can be applied in deciduous broad-leaved forests elsewhere.

Variable retention forestry conserves habitat of bird species in Patagonian Nothofagus pumilio forests

Variable retention is an alternative harvesting system that could be implemented instead the more traditional ones (e.g. shelterwood cut for N. pumilio forests in southern Patagonia), because it was designed not only for timber purpose, but also for conservation. However, the impact of different retention types on diversity is not clear, e.g. stenotopic and eurytopic bird species. The objective of this work was to analyse the habitats (inside, edge or outside of aggregated retention) and the use of strata (canopy, stem, debris and floor) for different bird species under two different variable retention harvesting types (aggregated + dispersed retentions, or ggregated retention + clear-cuts). We analysed four years of bird observation data in variable retention harvested and unharvested forest permanent plots located in Tierra del Fuego province (Argentina) belonging to PEBANPA (Parcelas de Ecologia y Biodiversidad de Ambientes Naturales en Patagonia Austral) network, also with understory and crown cover data. Statistical analysis included uni- and multivariate tests, and comparisons with unharvested forests. We inventoried nine bird species, six of which showed significantly different habitat preference in variable retention types (Carduelis barbata, Phrygilus patagonicus and Tachycineta leucopyga in aggregated + dispersed retentions, and Enicognathus ferrugineus, P. patagonicus, T. leucopyga, Troglodytes aedon and Zonotrichia capensis in aggregated retention + clearcuts). Likewise, all evaluated species presented differential use of strata, and some species changed comparing harvested and unharvested forests. DCA (Detrended Corresponded Analysis) highlighted association between species and habitats (e.g. P. patagonicus is more related to outside aggregated retentions) as well as differences between variable retention types, showing that bird species move toward edges when clear-cuts were carried out, among aggregated retention, instead of dispersed retention. These results support the effectiveness of the variable retention to conserve habitat of bird species inside managed forests, which satisfy both stenotopic and eurytopic species requirements.

Growth responses after a future crop tree thinning and a thinning from below in a second-growth Nothofagus pumilio forest in Tierra del Fuego, Chile

Nothofagus pumilio (lenga) is the most important native species for timber production in southern Patagonia both in Chile and Argentina. Thinning application to second-growth N. pumilio forests has been limited in Patagonia, probably because of the long time necessary for the investment to be recovered. In addition, experimental trials have focused mostly on thinnings from below, leaving a high residual stand density, which has led to a modest growth response. Using measurements (1995–2014) obtained from a thinning trial carried out in a second-growth N. pumilio forest located in Tierra del Fuego (Chile), the objective of this case study was to analyze whether selective thinnings with future crop trees (in the sense of Z-Baumen thinning) promote greater growth responses than those from a thinning from below. In addition, we explored the associations between climatic factors and age on N. pumilio tree growth. Trial treatments comprised a control, a thinning from below and a future crop tree thinning. The growth response after a future crop tree thinning was greater and lasted for a longer period (10 yrs) than did the thinning from below (4 yrs). The tree basal area and diameter at breast height (dbh) growth increased with dbh and annual absolute minimum temperature and decreased with age for the unthinned treatment during the period from 1977–2014 (~70–110 yrs old). Our results suggest that the future crop thinning might be a better alternative than the thinning from below for secondary N. pumilio forests in Patagonia due to the greater growth response while being a less intensive silvicultural method.