Alex Fajardo

Universidad de Talca · Instituto de Investigación Interdisciplinario

Deadwood is a large global carbon store with its store size partially determined by biotic decay. Microbial wood decay rates are known to respond to changing temperature and precipitation. Termites are also important decomposers in the tropics but are less well studied. An understanding of their climate sensitivities is needed to estimate climate c...

Non‐structural carbohydrates (NSCs) mediate plant survival when the plant’s carbon (C) balance is negative, suggesting that NSCs could predict plant survival under C stress. To examine this possibility, we exposed saplings of six temperate tree species to diverse levels of C stress created by the combination of two light conditions (full light avai...

Plant life-history variation reflects different outcomes of natural selection given the strictures of resource allocation trade-offs. However, there is limited theory of selection predicting how leaves, stems, roots, and reproductive organs should evolve in concert across environments. Here, we synthesize two optimality theories to offer a general...

Wood density (WD), a key trait in the trait‐based approach of plant ecology, represents a carbon investment trait that varies across species and reflects a trade‐off between metabolism and longevity. Across species, WD has been found to vary with phylogeny, moisture, temperature, and xylem anatomy (e.g., vessel diameter). However, we know little ab...

Worldwide drought events causing tree growth decline and mortality are altering the carbon (C) balance of forest ecosystems. One unexplored aspect of trees’ vulnerability is whether responses to drought may be linked to species’ niche breadth. Using the most severe 2015-2016 El Niño drought event in the last 70 years in Patagonia, we determined pre...

Key message: At the sixth and seventh years of a drought event in south of Chile, non-structural carbohydrate (NSC) concentrations were similar between healthy and unhealthy trees of Araucaria araucana (Molina) K. Koch, and growth did not decrease, suggesting that leaf loss prevented C shortage in unhealthy trees. Context: Tree drought resistance a...

Understanding adaptive genetic variation is key for predicting the evolutionary response of species and populations to climate change, decisively influencing management and conservation decisions. Landscape genomics provides a framework to disentangle the effects of local adaptation from those of geographic distance and demographic history, through...

Animals, such as termites, have largely been overlooked as global-scale drivers of biogeochemical cycles 1,2 , despite site-specific findings 3,4 . Deadwood turnover, an important component of the carbon cycle, is driven by multiple decay agents. Studies have focused on temperate systems 5,6 , where microbes dominate decay ⁷ . Microbial decay is se...

The process of forest degradation, along with deforestation, is the second greatest producer of global greenhouse gas emissions. A key challenge that remains unresolved is how to quantify the critical threshold that distinguishes a degraded from a non‐degraded forest. We determined the critical threshold of forest degradation in mature stands belon...

Premise: Wood density is a crucial plant functional trait related to plant strategies. Its ecological importance in small-stature growth forms (e.g., shrubs) has not been extensively examined. Given that hydraulic conduit dimensions vary positively with plant height and that there is a negative relationship between conduits' diameter and wood dens...

The effective use of functional traits to explain species coexistence has been hindered by the scarce use of demographic variables, such as growth, with the association between functional traits and growth often assumed rather than tested. In this study, using spatial point‐pattern analyses, we spatially related three functional traits linked to pl...

Con su imponente grandeza, el pequeño número de especies de árboles gigantes ha granjeado una desproporcionada atención científica. Para corregir esta tendencia, en este estudio nos centramos en las especies arbóreas de baja altura, que a menudo crecen a la sombra de los árboles gigantes y también en muchos otros lugares. El hecho de que los árbole...

Forests are being impacted by climate and land-use changes which have altered their productivity and growth. Understanding how tree growth responds to climate in natural and planted stands may provide valuable information to prepare management in sight of climate change. Plantations are expected to show higher sensitivity to climate and lower post-...

La competencia y la beneficencia [facilitación] simultáneas pueden tener importantes repercusiones en la estructura de la comunidad vegetal". Hunter y Aarssen (1988) "... los mecanismos responsables del ensamblaje de una comunidad vegetal que son los que determinan la naturaleza y la magnitud de los efectos de la facilitación en la composición de l...

Significance For most of its path through plant bodies, water moves in conduits in the wood. Plant water conduction is crucial for Earth’s biogeochemical cycles, making it important to understand how natural selection shapes conduit diameters along the entire lengths of plant stems. Can mathematical modeling and global sampling explain how wood con...

In his letter to the editor, Körner (2021) commented on our recent assessment of climate impacts on tree growth at treeline (Camarero et al. 2021). We share some of his opinions such as the non‐linear responses of growth to temperature. We also agree that focusing on temperature‐dependent processes such as growth can improve forecasts of treeline r...

Worldwide drought events have been reported to cause tree growth decline and mortality, thus altering the carbon (C) balance of forest ecosystems. While most of the attention has been focused on the physiological mechanisms associated with drought‐induced tree responses of a few species at specific locations, the ecological attributes of these spec...

The success of invasive plants is influenced by many interacting factors, but evaluating multiple possible mechanisms of invasion success and elucidating the relative importance of abiotic and biotic drivers is challenging, and therefore rarely achieved. We used live, sterile or inoculated soil from different soil origins (native range and introduc...

Climate warming is expected to positively alter upward and poleward treelines which are controlled by low temperature and a short growing season. Despite the importance of treelines as a bioassay of climate change, a global field assessment and posterior forecasting of tree growth at annual scales is lacking. Using annually resolved tree‐ring data...

Background and aims: The twig cross-sectional area and the surface area of leaves borne on it are expected to be isometrically correlated across species (Corner's rules). However, how stable this relationship remains in time is not known. We studied the interspecific and intraspecific twig leaf area-cross-sectional area (la-cs) and other scaling r...

Background and aims: Plants have the potential to adjust the configuration of their hydraulic system to maintain its function across spatial and temporal gradients. Species with wide environmental niches provide an ideal framework to assess intra-specific xylem adjustments to contrasting climates. We aimed at assessing how xylem structure in the w...

Flowering plants predominantly conduct water in tubes known as vessels, with vessel diameter playing a crucial role in plant adaptation to climate and reactions to climate change. The importance of vessels makes it essential to understand how and why vessel diameter, plant height, and other ecological factors are interrelated. Although shoot length...

•Variation in xylem conduit diameter has traditionally been explained by climate, while other evidence suggests that tree height is the main driver of conduit diameter. We tested the effect of climate versus stem length on vessel diameter in two tree species (Embothrium coccineum, Nothofagus antarctica) that both span an exceptionally wide precipit...

Background and aims: Cluster roots (CRs) constitute a special root adaptation that enables plants to take up nutrients, especially phosphorus (P), from soils with low nutrient availability, including recent volcanic deposits. It is unclear, however, how CR species interact with non-cluster root (NCR) species, and how substrates' fertility modulate...

Aims Rising temperature and declining summer precipitation due to the 1970s‐climate shift in southern South America have reduced forest productivity at dry sites. Here, we worked with the most widespread Southern Hemisphere tree line species, Nothofagus pumilio, across contrasting climatic conditions and determined whether rising atmospheric CO2 co...

Premise: Two fundamental hypotheses on herbivore resistance and leaf habit are the resource availability hypothesis (RAH) and the carbon-nutrient balance hypothesis (CNBH). The RAH predicts higher constitutive resistance by evergreens, and the CNBH predicts higher induced resistance by deciduous species. Although support for these hypotheses is mi...

1.Several plant species have the potential to facilitate the presence of other plant species in the community, and yet most of our knowledge on this phenomenon comes from studies considering only one facilitator species. What happens when there are two facilitator species in the community? Are the facilitation effects by one species being altered b...

It is assumed that widespread, generalist species have high phenotypic variation, but we know little about how intraspecific trait variation (ITV) relates to species abundance and niche breadth. In the temperate rainforest of southern Chile, we hypothesized that species with wide niche breadth would exhibit 1) high among‐plot ITV, 2) a strong relat...

Premise of the study: It is unclear to what extent the co-occurrence of angiosperm and gymnosperm species in some marginal ecosystems is explained by reduced growth in angiosperms due to carbon (C) limitation and by high stress tolerance in gymnosperms associated with lack of vessels and resource conservation. Methods: We examined growth pattern...

With their imposing grandeur, the small number of very tall tree species attract a disproportionate amount of scientific study. We right this bias by focusing here on the shorter trees, which grow in the shade of the giants and many other places besides. That tall trees are so restricted in distribution indicates that there are far more habitats av...

Human societies depend on an Earth system that operates within a constrained range of nutrient availability, yet the recent trajectory of terrestrial nitrogen (N) availability is uncertain. Examining patterns of foliar N concentrations and isotope ratios (δ15N) from more than 43,000 samples acquired over 37 years, here we show that foliar N concent...

Ecological regime shifts may lead to a loss of resilience if the affected ecosystem experiences rapid and irreversible changes affecting its structure and function. Coupled regime shifts in climate variability and forest growth have been rarely described, albeit they should play a prominent role on forest dynamics. Patagonia hosts the largest fores...

Invasive plant impacts vary widely across introduced ranges. We tested the hypothesis that differences in the eco‐evolutionary experience of native communities with the invader correspond with the impacts of invasive species on native vegetation, with impacts increasing with ecological novelty. We compared plant species richness and composition ben...

Significance As trees worldwide experience mortality or dieback with increasing drought and low tundras grow taller with warming, understanding the link between plant height and climate is increasingly important. We show that taller plants have predictably wider water-conducting conduits, and that wider conduits within species are more vulnerable t...

Background and Aims Trees adjust the configuration of their conductive system in response to changes in water availability, maximizing efficiency in wet environments and increasing safety in dry habitats. However, evidence of this general trend is not conclusive. Generalist species growing across broad climatic gradients provide an ideal framework...

Understanding patterns of functional trait variation across environmental gradients offers an opportunity to increase inference in the mechanistic causes of plant community assembly. The leaf economics spectrum (LES) predicts global tradeoffs in leaf traits and trait‐environment relationships, but few studies have examined whether these predictions...

The wood economics spectrum provides a general framework for interspecific trait-trait coordination across wide environmental gradients. Whether global patterns are mirrored within species constitutes a poorly explored subject. In this study, I first determined whether wood density co-varies along with elevation, tree growth and height at the withi...

Anthropogenic fires and land-use change, including the conversion from native to exotic species canopies, are two major types of disturbances that strongly affect the functioning of forest ecosystems around the world. These disturbances alter the resource availability for plants, which may lead to changes in species richness. Here we examined the r...

Since growth is more sensitive to drought than photosynthesis, trees inhabiting dry regions are expected to exhibit higher carbohydrate storage and less growth than their conspecifics from more humid regions. However, the same pattern can be the result of different genotypes inhabiting contrasting humidity conditions. To test if reduced growth and...

Climate change and rising atmospheric CO2 concentrations (ca) are expected to affect forests worldwide. The effects of climate change, however, have not been deeply assessed in humid forest biomes from the southern Hemisphere where climate is not warming but drying. This is the case of the temperate rainforest in southern Chile, where the endemic a...

SharedIt link: hFp://rdcu.be/oM9F for full text Temperature is a primary driver of the distribution of biodiversity as well as of ecosystem boundaries. Declining temperature with increasing elevation in montane systems has long been recognized as a major factor shaping plant community biodiversity, metabolic processes, and ecosystem dynamics. Elev...

Although the principal mechanism determining treeline formation appears to be carbon

Background and Aims Ecologists are increasingly using plant functional traits to predict community assembly, but few studies have linked functional traits to species’ responses to fine-scale resource gradients. In this study, it was tested whether saplings of woody species partition fine-scale gradients in light availability based on their leaf mas...

1. Plant species sometimes perform extraordinarily well when introduced to new environments, through achieving higher growth rates, individual biomasses or higher densities in their receiving communities compared to their native range communities. One hypothesis proposed to explain enhanced performance in species' new environments is that their soi...

The transition from seedlings into trees at alpine tree lines is a temperature-limited process that ultimately sets the tree line elevation at a global scale. As such, tree lines may be key bioassays of global warming effects on species distributions. For global warming to promote upward tree line migration, as predicted, seedlings must be availabl...

Carbon (C) storage is considered a key component to plant survival under drought and shade, although the combined effects of these factors on survival remain poorly understood. We investigated how drought and shade alter the C dynamics and survival of tree seedlings, and whether drought limits the access to or usage of stored C. We experimentally a...

Pinus contorta, one of the most invasive tree species in the world, has been proposed as a model species for improving our understanding of invasion ecology. In this study, we assessed the impact of P. contorta invasions on the species richness, diversity and species traits of a resident treeless steppe community. In a Pinus contorta invasion gradi...

Premise of the study: The study of scaling examines the relative dimensions of diverse organismal traits. Understanding whether global scaling patterns are paralleled within species is key to identify causal factors of universal scaling. I examined whether the foliage-stem (Corner's rules), the leaf size-number, and the leaf mass-leaf area scaling...

A basic assumption of the trait-based approach in plant ecology is that differences in functional trait values are greater between species than within species. We questioned this assumption by assessing (1) the relative extent of inter- and intraspecific leaf trait variation throughout a complete growing season (phenological variation) in a group o...

The growth limitation hypothesis (GLH) is the most accepted explanation for treeline formation, but it has been scarcely examined in Mediterranean treelines, which are located at lower elevations than temperate treelines. The GLH states that low temperature is the ultimate environmental driver for treeline formation, constraining C-sinks (i.e. tiss...

Recent studies have shown that accounting for intraspecific trait variation (ITV) may better address major questions in community ecology. However, a general picture of the relative extent of ITV compared to interspecific trait variation in plant communities is still missing. Here, we conducted a meta-analysis of the relative extent of ITV within a...

AimsWhile treeline positions are globally correlated to growing season temperatures, seedling establishment, an important process of alpine treeline dynamics, is additionally controlled by regional-scale factors such as snow cover duration, desiccating winds and biotic interactions. Knowing that alpine treelines have shown contrasting responses to...

Background and aims: Disturbances, dispersal and biotic interactions are three major drivers of the spatial distribution of genotypes within populations, the last of which has been less studied than the other two. This study aimed to determine the role of competition and facilitation in the degree of conspecific genetic relatedness of nearby indiv...

Fire and land-use change are two major types of disturbances that strongly affect the structure and function of forest ecosystems around the world, although their impacts can be difficult to quantify due to concomitant changes in climate or other land-use change factors. In this study we examined how fire and subsequent land-use conversion impacted...

Recent studies have shown that accounting for intraspecific trait variation (ITV) may better address major questions in community ecology. However, a general picture of the relative extent of ITV compared to interspecific trait variation in plant communities is still missing. Here, we conducted a meta-analysis of the relative extent of ITV within a...

A study about the effects fire and posterior land-used management have on soil properties and processes in Patagonia, Chile. Soil properties and processes under Pinus ponderosa are the most similar to pre-fire conditions under Nothofagus cover.

Background and aims: There is a growing concern about how forests will respond to increased herbivory associated with climate change. Carbon (C) and nitrogen (N) limitation are hypothesized to cause decreasing growth after defoliation, and eventually mortality. This study examines the effects of a natural and massive defoliation by an insect on ma...

• Southern South American (SA) Proteaceae species growing in volcanic soils have been proposed as potential ecosystem engineers by tapping phosphorus (P) from soil through their cluster roots and shedding nutrient-rich litter to the soil, making it available for other species. We tested whether Embothrium coccineum (Proteaceae) has effectively lowe...

Background/Question/Methods The focus of the trait–based approach to study community ecology has mostly been on trait comparisons at the interspecific level. This is mainly because at large–scale environmental gradients, species turnover overrates intraspecific trait variation. In nature, however, there are many generalist species that can prevail...

An innovative hypothesis to explain the higher carbon (C) and nitrogen (N) storage in woody tissues of winter deciduous species as compared to evergreen species is that these storages reflect an adaptation to tolerate herbivory. Support for this hypothesis has been little when manipulative defoliations used partial and/or single–season defoliations...

The growth limitation hypothesis (GLH) is the most accepted mechanistic explanation for treeline formation, although it is still uncertain whether it applies across taxa. The successful establishment of Pinus contorta--an exotic conifer species in the southern hemisphere--above the Nothofagus treeline in New Zealand may suggest a different mechanis...

Cluster roots are a characteristic root adaptation of Proteaceae species. In South African and Australian species, cluster roots promote phosphorus (P) acquisition from poor soils. In a South American Proteaceae species, where cluster roots have been scarcely studied and their function is unknown, we tested whether cluster-root formation is stimula...

I. II. III. IV. V. VI. VII. VIII. References SUMMARY: Models describing the biotic drivers that create and maintain biological diversity within trophic levels have focused primarily on negative interactions (i.e. competition), leaving marginal room for positive interactions (i.e. facilitation). We show facilitation to be a ubiquitous driver of biod...

Background/Question/Methods Globally, alpine treeline positions are defined by temperature which has led to the assumption that treelines would rise in response to climate change. But recruitment above treeline is also controlled by local drivers which modulate the effect of climate. This study aims to measure the relative effect of abiotic (temp...

Recent functional trait studies have shown that trait differences may favour certain species (environmental filtering) while simultaneously preventing competitive exclusion (niche partitioning). However, phenomenological trait-dispersion analyses do not identify the mechanisms that generate niche partitioning, preventing trait-based prediction of f...

Background and Aims The most plausible explanation for treeline formation so far is provided by the growth limitation hypothesis (GLH), which proposes that carbon sinks are more restricted by low temperatures than by carbon sources. Evidence supporting the GLH has been strong in evergreen, but less and weaker in deciduous treeline species. Here a t...

Background/Question/Methods Cone production is known to decrease with altitude due to low growing season temperatures, which reduces the developmental period available to cone buds at the alpine treeline. However, the microclimate experienced by individual plants differs from ambient air temperature: wind has a direct negative effect on plant mic...

Background/Question/Methods Facilitation (positive interactions among individuals or species) has emerged as a dominant ecological mechanism in many ecosystems. Three dominant lines of evidence in ecological research have placed facilitation as a process a) whose net effect is greater in more stressful locations, b) that is not important where nic...

Background/Question/Methods The classical view of deciduous tree species having higher dependence on carbon reserves for spring leaf-out and growth than evergreen species has been challenged lately; just a small proportion of carbon reserves in deciduous trees is indeed used during the leaf-out period. Thus, an unsolved and relevant ecological qu...

Multi-stemmed trees (tree clusters) in Nothofagus pumilio, a dominant tree species in Patagonia, are very uncommon and are restricted to the edge of second-growth forests following human-provoked fires. No vegetative reproduction has been reported so far. The genetic structure of multi-stemmed trees of this species was investigated and it was hypot...

In low temperature-adapted plants, including treeline trees, light-saturated photosynthesis is considerably less sensitive to temperature than growth. As a consequence, all plants tested so far show increased nonstructural carbohydrate (NSC) tissue concentrations when exposed to low temperatures. Reduced carbon supply is thus an unlikely cause for...

1. Altitudinal tree line ecotones (ATE) are among the most sensitive plant formations facing global warming as the altitudinal decrease in temperature is considered the driver controlling the upper elevation limit of tree lines world-wide. In this study, we attempted to answer the following questions: (i) how have the conditions during the last 2–3...

Conducting botanical and ecological explorations with the objective of studying the floristic composition of post-fire communities in the Aysen Region, we found new regional records of the fern Botrychium dusenii (H. Christ.) Alston (Ophioglossaceae). These findings, that extend the north limit of the species distribution, occurred in open areas af...

Conducting botanical and ecological explorations with the objective of studying the floristic composition of post-fire communities in the Aysén Region, we found new regional records of the fern Botrychium dusenii (H. Christ.) Alston (Ophioglossaceae). These findings, that extend the north limit of the species distribution, occurred in open areas af...

Trees universally decrease their growth with age. Most explanations for this trend so far support the hypothesis that carbon (C) gain becomes limited with age; though very few studies have directly assessed the relative reductions of C gain and C demand with tree age. It has also been suggested that drought enhances the effect of C gain limitation...

Facilitation (positive interactions) has emerged as a dominant ecological mechanism in many ecosystems. Its importance has recently been expanded to include intraspecific interactions, creating the potential for higher-level natural selection within species. Using multiple lines of evidence, we show that conspecific facilitation within the southern...