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Our knowledge about the structure and function of Andean forests at regional scales remains limited. Current initiatives to study forests over continental or global scales still have important geographical gaps, particularly in regions such as the tropical and subtropical Andes. In this study, we assessed patterns of structure and tree species diversity along ~ 4000 km of latitude and ~ 4000 m of elevation range in Andean forests. We used the Andean Forest Network (Red de Bosques Andinos, https://redbosques.condesan.org/) database which, at present, includes 491 forest plots (totaling 156.3 ha, ranging from 0.01 to 6 ha) representing a total of 86,964 identified tree stems ≥ 10 cm diameter at breast height belonging to 2341 identified species, 584 genera and 133 botanical families. Tree stem density and basal area increases with elevation while species richness decreases. Stem density and species richness both decrease with latitude. Subtropical forests have distinct tree species composition compared to those in the tropical region. In addition, floristic similarity of subtropical plots is between 13 to 16% while similarity between tropical forest plots is between 3% to 9%. Overall, plots ~ 0.5-ha or larger may be preferred for describing patterns at regional scales in order to avoid plot size effects. We highlight the need to promote collaboration and capacity building among researchers in the Andean region (i.e., South-South cooperation) in order to generate and synthesize information at regional scale.

Global warming is forcing many species to shift their distributions upward, causing consequent changes in the compositions of species that occur at specific locations. This prediction remains largely untested for tropical trees. Here we show, using a database of nearly 200 Andean forest plot inventories spread across more than 33.5° latitude (from 26.8° S to 7.1° N) and 3,000-m elevation (from 360 to 3,360 m above sea level), that tropical and subtropical tree communities are experiencing directional shifts in composition towards having greater relative abundances of species from lower, warmer elevations. Although this phenomenon of ‘thermophilization’ is widespread throughout the Andes, the rates of compositional change are not uniform across elevations. The observed heterogeneity in thermophilization rates is probably because of different warming rates and/or the presence of specialized tree communities at ecotones (that is, at the transitions between distinct habitats, such as at the timberline or at the base of the cloud forest). Understanding the factors that determine the directions and rates of compositional changes will enable us to better predict, and potentially mitigate, the effects of climate change on tropical forests. With global warming, Andean forests are changing to include more trees of low-elevation, heat-loving species but rates of compositional change are not uniform across elevations and are insufficient to keep species in equilibrium with climate.

• Recent studies have demonstrated that ecological processes that shape community structure and dynamics change along environmental gradients. However, much less is known about how the emergence of the gradients themselves shape the evolution of species that underlie community assembly. In this study, we address how the creation of novel environments leads to community assembly via two nonmutually exclusive processes: immigration and ecological sorting of pre-adapted clades (ISPC), and recent adaptive diversification (RAD). We study these processes in the context of the elevational gradient created by the uplift of the Central Andes. • We develop a novel approach and method based on the decomposition of species turnover into within- and among-clade components, where clades correspond to lineages that originated before mountain uplift. Effects of ISPC and RAD can be inferred from how components of turnover change with elevation. We test our approach using data from over 500 Andean forest plots. • We found that species turnover between communities at different elevations is dominated by the replacement of clades that originated before the uplift of the Central Andes. • Our results suggest that immigration and sorting of clades pre-adapted to montane habitats is the primary mechanism shaping tree communities across elevations.

Context. Exploring how Indigenous People interact with plants through their functional traits allows us to understand the ecological bases of plant selection. Functional traits can help explain why certain plants are consistently chosen for specific purposes across diverse cultural contexts. However, these relationships are complex and remain insufficiently explored. Here, we ask (1) which functional traits are most important in shaping different uses? and (2) do similarities in trait–use associations across Indigenous communities reflect patterns of knowledge convergence? Methods. We conducted fieldwork across nine different Indigenous communities spanning a 1800 km distance in western Amazonia. In total, we sampled 115 0.1‐ha plots, recording the abundance of 1856 woody plant species. For these species, we collected data on 13 different functional traits, primarily measured in the field, with additional values sourced from TRY and other databases, and conducted in situ ethnobotanical interviews with 25 Indigenous male participants, focusing on 14 distinct use categories. We analysed (1) trait–use relationships using generalized linear models and (2) the similarity in trait selection for each use across communities using generalized linear mixed models. Results. Plants used for medicine or food were associated with multiple traits, including reproductive traits, exudates and life form. In contrast, culturally specific uses such as rituals, cosmetics or recreational were linked to more specific traits, particularly wood density and lianas. Across communities, we observed widespread convergence in trait–use associations, suggesting shared patterns of plant use despite cultural differences. However, 24% of the trait–use combinations showed divergence, indicating local adaptation or cultural specificity. Synthesis and applications. Plant selection by Indigenous communities is not random; rather, it is guided by functional traits that consistently support human well‐being. We named this pattern ‘functional selection convergence’, highlighting how ecological function and traditional knowledge interact across distinct cultural contexts. This convergence shows the importance of functional ecology explaining traditional plant selection. Our findings are a call for a trait‐based ethnobotanical approach to document and better preserve the ecosystem services essential to Indigenous livelihoods. Nevertheless, we emphasize the need for future research to involve broader and more diverse ethnobotanical participation. Read the free Plain Language Summary for this article on the Journal blog. Resumen Contexto. Explorar cómo las comunidades Indígenas interaccionan con las plantas a través de sus rasgos funcionales nos permiten entender las bases ecológicas de la selección de plantas. Los rasgos funcionales nos pueden ayudar a explicar por qué ciertas plantas son elegidas para propósitos específicos, a través de distintos contextos culturales. Sin embargo, estas relaciones con complejas y todavía quedan por explorar. Nos preguntamos, 1) ¿qué rasgos funcionales son los más importantes a la hora de configurar los distintos usos? y 2) ¿las similitudes en las asociaciones rasgo‐uso entre comunidades Indígenas reflejan patrones de convergencia de conocimiento? Métodos. Llevamos a cabo trabajo de campo en nueve comunidades Indígenas a lo largo de un gradiente latitudinal de 1,800 km en la Amazonía Occidental. En total, tomamos datos de 115 parcelas, de 0.1 ha cada una, recogiendo la abundancia de 1,856 especies de plantas leñosas. Para estas especies, tomamos datos de 13 rasgos funcionales, principalmente medidos en el campo, con valores adicionales provenientes de TRY y otras bases de datos. También tomamos datos in situ de entrevistas etnobotánicas a 25 participantes Indígenas hombres, centrándonos en 14 categorías de uso. Analizamos 1) la relación entre el rasgo y el uso con modelos lineares generalizados y 2) la similitud de selección del rasgo para cada uso a través de las comunidades utilizando modelos lineares generalizados mixtos. Resultados. Las plantas utilizadas para medicina o alimentación fueron asociadas con multitud de rasgos, incluyendo rasgos asociados con la reproducción, exudados y forma de vida. Por otro lado, los usos más culturales, como rituales, cosméticos o recreacionales tuvieron relación con rasgos más específicos, particularmente densidad de madera y las lianas como forma de vida. A través de comunidades Indígenas, observamos que existe una convergencia de conocimiento de las asociaciones rasgo‐uso, sugiriendo patrones compartidos de uso a pesar de las diferencias culturales. Sin embargo, el 24% de las combinaciones mostraron divergencia de conocimiento, indicando una adaptación local o especificidad cultural. Síntesis y aplicaciones. La selección de plantas por las comunidades Indígenas no es aleatoria; de hecho está guiada por rasgos funcionales que mantienen el bienestar humano. Hemos nombrado este patrón como “selección functional convergente”, que destaca cómo la función ecológica y el conocimiento tradicional interaccionan a través de distintos contextos culturales. Esta convergencia muestra la importancia de la ecología funcional para explicar la selección tradicional de plantas. Estos resultados llaman a una aproximación a la etnobotánica con base funcional para documentar y preservar mejor los servicios ecosistémicos esenciales para los recursos de las personas Indígenas. Sin embargo, destacamos la necesidad en el futuro de aplicar una participación etnobotánica más diversa y amplia. Read the free Plain Language Summary for this article on the Journal blog.

It is largely unknown how South America’s Andean forests affect the global carbon cycle, and thus regulate climate change. Here, we measure aboveground carbon dynamics over the past two decades in 119 monitoring plots spanning a range of >3000 m elevation across the subtropical and tropical Andes. Our results show that Andean forests act as strong sinks for aboveground carbon (0.67 ± 0.08 Mg C ha −1 y −1 ) and have a high potential to serve as future carbon refuges. Aboveground carbon dynamics of Andean forests are driven by abiotic and biotic factors, such as climate and size-dependent mortality of trees. The increasing aboveground carbon stocks offset the estimated C emissions due to deforestation between 2003 and 2014, resulting in a net total uptake of 0.027 Pg C y −1 . Reducing deforestation will increase Andean aboveground carbon stocks, facilitate upward species migrations, and allow for recovery of biomass losses due to climate change. Here, the authors investigate the aboveground carbon sink efficiency of Andean forests. The study shows the high potential of these forests to serve as future carbon refuges, and urges to reduce deforestation and increase restoration.

Why do forest productivity and biomass decline with elevation? To address this question, research to date generally has focused on correlative approaches describing changes in woody growth and biomass with elevation. We present a novel, mechanistic approach to this question by quantifying the autotrophic carbon budget in 16 forest plots along a 3300m elevation transect in Peru. Low growth rates at high elevations appear primarily driven by low gross primary productivity (GPP), with little shift in either carbon use efficiency (CUE) or allocation of net primary productivity (NPP) between wood, fine roots and canopy. The lack of trend in CUE implies that the proportion of photosynthate allocated to autotrophic respiration is not sensitive to temperature. Rather than a gradual linear decline in productivity, there is some limited but nonconclusive evidence of a sharp transition in NPP between submontane and montane forests, which may be caused by cloud immersion effects within the cloud forest zone. Leaf-level photosynthetic parameters do not decline with elevation, implying that nutrient limitation does not restrict photosynthesis at high elevations. Our data demonstrate the potential of whole carbon budget perspectives to provide a deeper understanding of controls on ecosystem functioning and carbon cycling.

Aim: Tropical elevation gradients are natural laboratories to assess how changing climate can influence tropical forests. However, there is a need for theory and integrated data collection to scale from traits to ecosystems. We assess predictions of a novel trait-based scaling theory, including whether observed shifts in forest traits across a broad tropical temperature gradient are consistent with local phenotypic optima and adaptive compensation for temperature. Location: An elevation gradient spanning 3,300 m and consisting of thousands of tropical tree trait measures taken from 16 1-ha tropical forest plots in southern Perú, where gross and net primary productivity (GPP and NPP) were measured. Time period: April to November 2013. Major taxa studied: Plants; tropical trees. Methods: We developed theory to scale from traits to communities and ecosystems and tested several predictions. We assessed the covariation between climate, traits, biomass and GPP and NPP. We measured multiple traits linked to variation in tree growth and assessed their frequency distributions within and across the elevation gradient. We paired these trait measures across individuals within 16 forests with simultaneous measures of ecosystem net and gross primary productivity. Results: Consistent with theory, variation in forest NPP and GPP primarily scaled with forest biomass, but the secondary effect of temperature on productivity was much less than expected. This weak temperature dependence appears to reflect directional shifts in several mean community traits that underlie tree growth with decreases in site temperature. Main conclusions: The observed shift in traits of trees that dominate in more cold environments is consistent with an 'adaptive/acclimatory' compensation for the kinetic effects of temperature on leaf photosynthesis and tree growth. Forest trait distributions across the gradient showed overly peaked and skewed distributions, consistent with the importance of local filtering of optimal growth traits and recent shifts in species composition and dominance attributable to warming from climate change. Trait-based scaling theory provides a basis to predict how shifts in climate have and will influence the trait composition and ecosystem functioning of tropical forests.

General patterns of forest dynamics and productivity in the Andes Mountains are poorly characterized. Here we present the first large-scale study of Andean forest dynamics using a set of 63 permanent forest plots assembled over the past two decades. In the North-Central Andes tree turnover (mortality and recruitment) and tree growth declined with increasing elevation and decreasing temperature. In addition, basal area increased in Lower Montane Moist Forests but did not change in Higher Montane Humid Forests. However, at higher elevations the lack of net basal area change and excess of mortality over recruitment suggests negative environmental impacts. In North-Western Argentina, forest dynamics appear to be influenced by land use history in addition to environmental variation. Taken together, our results indicate that combinations of abiotic and biotic factors that vary across elevation gradients are important determinants of tree turnover and productivity in the Andes. More extensive and longer-term monitoring and analyses of forest dynamics in permanent plots will be necessary to understand how demographic processes and woody biomass are responding to changing environmental conditions along elevation gradients through this century.

As Open Science practices become more commonplace, there is a need for the next generation of scientists to be well versed in these aspects of scientific research. Yet, many training opportunities for early career researchers (ECRs) could better emphasize or integrate Open Science elements. Field courses provide opportunities for ECRs to apply theoretical knowledge, practice new methodological approaches, and gain an appreciation for the challenges of real-life research, and could provide an excellent platform for integrating training in Open Science practices. Our recent experience, as primarily ECRs engaged in a field course interrupted by COVID-19, led us to reflect on the potential to enhance learning outcomes in field courses by integrating Open Science practices and online learning components. Specifically, we highlight the opportunity for field courses to align teaching activities with the recent developments and trends in how we conduct research, including training in: publishing registered reports, collecting data using standardized methods, adopting high-quality data documentation, managing data through reproducible workflows, and sharing and publishing data through appropriate channels. We also discuss how field courses can use online tools to optimize time in the field, develop open access resources, and cultivate collaborations. By integrating these elements, we suggest that the next generation of field courses will offer excellent arenas for participants to adopt Open Science practices.