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Funding: Data collection was largely funded by the UK Natural Environment Research Council (NERC) project TREMOR (NE/N004655/1) to D.G., E.G. and O.P., with further funds from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES, finance code 001) to J.V.T. and a University of Leeds Climate Research Bursary Fund to J.V.T. D.G., E.G. and O.P. acknowledge further support from a NERC-funded consortium award (ARBOLES, NE/S011811/1). This paper is an outcome of J.V.T.’s doctoral thesis, which was sponsored by CAPES (GDE 99999.001293/2015-00). J.V.T. was previously supported by the NERC-funded ARBOLES project (NE/S011811/1) and is supported at present by the Swedish Research Council Vetenskapsrådet (grant no. 2019-03758 to R.M.). E.G., O.P. and D.G. acknowledge support from NERC-funded BIORED grant (NE/N012542/1). O.P. acknowledges support from an ERC Advanced Grant and a Royal Society Wolfson Research Merit Award. R.S.O. was supported by a CNPq productivity scholarship, the São Paulo Research Foundation (FAPESP-Microsoft 11/52072-0) and the US Department of Energy, project GoAmazon (FAPESP 2013/50531-2). M.M. acknowledges support from MINECO FUN2FUN (CGL2013-46808-R) and DRESS (CGL2017-89149-C2-1-R). C.S.-M., F.B.V. and P.R.L.B. were financed by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES, finance code 001). C.S.-M. received a scholarship from the Brazilian National Council for Scientific and Technological Development (CNPq 140353/2017-8) and CAPES (science without borders 88881.135316/2016-01). Y.M. acknowledges the Gordon and Betty Moore Foundation and ERC Advanced Investigator Grant (GEM-TRAITS, 321131) for supporting the Global Ecosystems Monitoring (GEM) network (gem.tropicalforests.ox.ac.uk), within which some of the field sites (KEN, TAM and ALP) are nested. The authors thank Brazil–USA Collaborative Research GoAmazon DOE-FAPESP-FAPEAM (FAPESP 2013/50533-5 to L.A.) and National Science Foundation (award DEB-1753973 to L. Alves). They thank Serrapilheira Serra-1709-18983 (to M.H.) and CNPq-PELD/POPA-441443/2016-8 (to L.G.) (P.I. Albertina Lima). They thank all the colleagues and grants mentioned elsewhere [8,36] that established, identified and measured the Amazon forest plots in the RAINFOR network analysed here. The authors particularly thank J. Lyod, S. Almeida, F. Brown, B. Vicenti, N. Silva and L. Alves. This work is an outcome approved Research Project no. 19 from ForestPlots.net, a collaborative initiative developed at the University of Leeds that unites researchers and the monitoring of their permanent plots from the world’s tropical forests [61]. The authros thank A. Levesley, K. Melgaço Ladvocat and G. Pickavance for ForestPlots.net management. They thank Y. Wang and J. Baker, respectively, for their help with the map and with the climatic data. The authors acknowledge the invaluable help of M. Brum for kindly providing the comparison of vulnerability curves based on PAD and on PLC shown in this manuscript. They thank J. Martinez-Vilalta for his comments on an early version of this manuscript. The authors also thank V. Hilares and the Asociación para la Investigación y Desarrollo Integral (AIDER, Puerto Maldonado, Peru); V. Saldaña and Instituto de Investigaciones de la Amazonía Peruana (IIAP) for local field campaign support in Peru; E. Chavez and Noel Kempff Natural History Museum for local field campaign support in Bolivia; ICMBio, INPA/NAPPA/LBA COOMFLONA (Cooperativa mista da Flona Tapajós) and T. I. Bragança-Marituba for the research support. Tropical forests face increasing climate risk1,2, yet our ability to predict their response to climate change is limited by poor understanding of their resistance to water stress. Although xylem embolism resistance thresholds (for example, Ψ50) and hydraulic safety margins (for example, HSM50) are important predictors of drought-induced mortality risk3-5, little is known about how these vary across Earth's largest tropical forest. Here, we present a pan-Amazon, fully standardized hydraulic traits dataset and use it to assess regional variation in drought sensitivity and hydraulic trait ability to predict species distributions and long-term forest biomass accumulation. Parameters Ψ50 and HSM50 vary markedly across the Amazon and are related to average long-term rainfall characteristics. Both Ψ50 and HSM50 influence the biogeographical distribution of Amazon tree species. However, HSM50 was the only significant predictor of observed decadal-scale changes in forest biomass. Old-growth forests with wide HSM50 are gaining more biomass than are low HSM50 forests. We propose that this may be associated with a growth-mortality trade-off whereby trees in forests consisting of fast-growing species take greater hydraulic risks and face greater mortality risk. Moreover, in regions of more pronounced climatic change, we find evidence that forests are losing biomass, suggesting that species in these regions may be operating beyond their hydraulic limits. Continued climate change is likely to further reduce HSM50 in the Amazon6,7, with strong implications for the Amazon carbon sink. Publisher PDF

Aim: The latitudinal biodiversity gradient is considered a first-order biogeographical pattern for most taxonomic groups. Latitudinal variation in plant diversity is not always consistent, and this could be related to the particular characteristics of different forest types. In this study, we compare latitudinal changes in floristic diversity (alpha diversity), composition (beta diversity) and dominance across different tropical forest types: floodplain, terra firme and submontane forests. Location: Western Amazonia (Ecuador, Peru and Bolivia). Taxon: Woody plants. Methods: We inventoried 1978 species and 31,203 individuals of vascular plants with a diameter at breast height ≥ 2.5 cm in 118 0.1-ha plots over an 1800 km latitudinal gradient in three different forest types. The relationships between alpha diversity, latitude and forest type were analysed using generalised linear mixed models. Semi-parametric permutational multivariate analysis of variance was used to investigate the effects of latitude and forest type on beta diversity. Dominant species abundances were correlated with non-metric multidimensional scaling ordination axes to reflect their contributions in shaping changes in beta diversity. Results: Alpha diversity increased towards equatorial latitudes in terra firme and submontane forests but remained relatively constant in floodplains. Beta diversity of all forest types changed with latitude, although less clearly in floodplains. Also, in floodplain forests, there were fewer dominant species contributing to beta diversity and more species homogeneous along the gradient. Main Conclusions: Latitudinal diversity patterns are manifested in alpha and beta diversity since latitude summarizes climatic and edaphic changes. However, we found different responses of each forest type. In floodplain forests, inundation regime is a stronger predictor than latitude, limiting floristic diversity and composition. Changes in dominant species abundance over gradients explained species composition, but floodplain forests harboured more homogeneous dominant species than well drained forests. It is key to study environmental trends and habitat characteristics of each forest type to understand their species diversity and dominance patterns

Plot-based monitoring has yielded much information on the taxonomic diversity and carbon (C) storage in tropical lowland forests of the Amazon basin. This has resulted in an improved understanding of the relationship between lowland forest biomass dynamics and global change drivers, such as climate change and atmospheric CO2 concentration. Much less attention has been paid to the mountain ecosystems of South America that comprise montane forests and alpine vegetation (páramo, puna, high Andean grasslands, wetlands, and alpine heath). This vegetation complex provides a variety of ecosystem services and forms a natural laboratory along various physiographic, geological and evolutionary history/biogeography, and land use history gradients. Here, we review existing empirical understanding and model-based approaches to quantify the contribution of mountain ecosystems to ecosystem service provision in the rapidly changing socioecological setting of the South American mountains. The objective of this paper is to outline a broad road map for the implementation of mountain vegetation into dynamic global vegetation models (DGVM) for use in Earth System Models (ESM), based on our current understanding of their structure and function and of their responsiveness to global change drivers. We also identify treeline processes, critical in mountain ecosystems, as key missing elements in DGVMs/ESMs, and thus explore in addition a treeline model. Stocktaking of the availability of empirical data was undertaken from eight research sites along the Andes and in south-eastern Brazil. Out of eight sites, two (one each in Venezuela and Brazil) had some climate, ecological and ecophysiological data potentially suitable to parametrise a DGVM. Tree biomass data were available for six sites. A preliminary assessment of the Joint UK Land Environment Simulator (JULES) DGVM was made to identify gaps in available data and their impacts on model parametrisation and calibration. Additionally, the potential climate-determined elevation of the treeline was modelled to check the DGVM for its ability to identify the transition between the montane forest and alpine vegetation. Outcomes of the evaluation of the JULES land surface model identified the following key processes in montane forests: temperature-related decrease in net primary production, respiration, and allocation to above-ground biomass and increase in soil C stocks with elevation. There was a variable agreement between simulated biomass and those derived from field measurements via allometric equations. We identified major gaps between data availability and the needs for process-based modelling of South American mountain vegetation and its dynamics in DGVMs. To bridge this gap, we propose a transdisciplinary network, composed of members of the theoretical/modelling and empirical scientific communities, to study the natural dynamics of mountain ecosystems and their responses to global change drivers locally, regionally and at the continental scale, within a social-ecological system framework. The work presented here forms the basis for the design of data collection from field measurements and instrumental monitoring stations to parametrise and verify DGVMs. The network is designed to collaborate with and complement existing long-term research initiatives in the region and will adopt existing standard field protocols. Complementary protocols will ensure compatibility between field data collection and data needed for process-based and empirical models.

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.

Territórios Indígenas (TIs) na Amazônia protegem aproximadamente 24.5 gigatoneladas de carbono (GtC) acima do solo, atuam como barreiras significativas contra o desmatamento e a degradação florestal, e funcionam como importantes amortecedores contra as mudanças climáticas. TIs demarcadas apresentam desmatamento significativamente menor do que terras não reconhecidas oficialmente, demonstrando a importância de se demarcar TIs tanto para proteger os meios de subsistência e as culturas dos povos nativos da Amazônia, quanto para conservar suas florestas e rios.

Territorios indígenas (ITs, en sus siglas en inglés) en la Amazonia protegen aproximadamente 24,GtC sobre el suelo, funcionan como barreras significativas contra la deforestación y la degradación del bosque, y sirven como una defensa importante contra el cambio climático. Los ITs demarcados tienen significativamente menos deforestación en comparación con tierras no reconocidas, demostrando la importancia de demarcar ITs para proteger los sustentos y la cultura de los indígenas Amazónicos y para conservar sus bosques y ríos.

Indigenous territories (ITs) in the Amazon protect approximately 24.5 GtC aboveground, act as significant barriers to deforestation and forest degradation, and serve as an important buffer against climate change. Demarcated ITs have significantly less deforestation than unrecognized lands, demonstrating the importance of demarcating ITs to both protect the livelihoods and cultures of the Amazon’s native peoples and to conserve its forests and rivers.

Ant-plant defensive mutualism is a widely studied phenomenon, where ants protect their host plants (myrmecophytes) against herbivores in return for the provision of nesting sites and food. However, few studies addressed the influence of ant colonization and herbivory on the plant's metabolism. We chose the Amazonian plant

Elucidating how environmental factors drive plant species distributions and how they affect latitudinal diversity gradients, remain essential questions in ecology and biogeography. In this study we aimed: 1) to investigate the relationships between all three diversity attributes

Este capítulo discutirá los impactos observados y pronosticados del cambio climático en los ecosistemas terrestres y acuáticos amazónicos. Nos centraremos en los impactos sobre la biodiversidad, los servicios ecosistémicos, el ciclo del carbono, la pesca y las emisiones de quema de biomasa.

En este capítulo resumimos información sobre los ecosistemas amazónicos y sus funciones ecológicas, con un enfoque principal en los árboles. Comenzamos con una breve descripción de los tipos de vegetación de los Andes, seguida de una descripción más detallada de los tipos de vegetación terrestre de las tierras bajas amazónicas y concluimos con los vastos humedales incluidos en el área. Continuamos con un análisis de las principales funciones de los ecosistemas (p. ej., terrestres y acuáticos), con énfasis en la productividad y el secuestro de carbono. El objetivo de este capítulo es revelar la enorme variación de los tipos de vegetación, su diversidad y funcionamiento, y cómo esto es determinado por la dinámica del suelo, el clima y las inundaciones.

To know the quantity of fine root biomass is crucial to understanding ecosystem structure and function. Soil characteristics and fertility are mainly determined by fine root dynamics, the turnover of this material is a major contribution of organic matter to soil structure and mineral nutrient cycles, and also the main source of carbon storage. Many studies of forests are mainly estimates of above-ground biomass. Here we report on differential patterns of fine root biomass allocation in Peruvian forests. Peru is divided into three large sub-regions, Amazon, Andean, and coast. These different ecosystems have also around 84 of the 103 ecosystems types and 28 of the 32 climates on the planet. A field study was conducted installing one-hectare permanent plots in each sub-region, this research was part of an intensive monitoring effort of the carbon cycle and functional traits in primary and secondary forests. To evaluate fine root biomass, 1 m2 cross-section pits were set up in the plots where soil samples were collected every 10 cm up to 1 m depth and every 25 cm up to 2 m depth. Roots were retrieved and sorted into different diameter categories ≤0.5, 0.5 - 2.5, 2.5 - 5, and> 5 cm. Samples were rinsed with tap water over a 500-um sieve to loosen the soil and facilitate root sorting and to ensure that the sieve was fine enough to retain the finer roots. The roots after sorting were weighed fresh and then dried at 80°C for 48 hours, weighed to the nearest 0.0001 g, and stored in plastic vials for chemical analysis.Total root biomass measurements displayed strong regional differences. Coastal dry forest at 370 to 422 m in elevation, where a one ha plot can support 651-681 stems (> 10 cm dbh) had root biomass values ranging from 7960 kg ha-1 to 8130 kg/ha-1. Andean forest plots at 1780 m.a.s.l., with 586 stems contained 17020 kg ha-1 and Amazonian forest at 415 m.a.s.l., with 689 stems, had 33410 kg ha-1 fine root biomass. Our results support the hypothesis that large root biomass in tropical forests is related to ecosystem type, climatic variables (temperature and moisture), and nutrients. The low bulk density and fine root biomass in tropical forests are inversely related to temperature and moisture. Fine-root turnover decreased with soil depth, which can also have important implications for the soil carbon stock and C cycling.

Peru and Chile occupy second place in South America in area devoted to olive cultivation. Although small by Mediterranean standards, the 21,000 ha in each country represent a significant recent expansion of olive cultivation, 500 years after its introduction from Europe. The main climatic characteristic of olive cultivation in Peru is the coastal desert environment with moderate temperatures (12-28 oC), almost nil precipitation and high atmospheric water content in the winter season. There is still insufficient information about olive physiology and water management under these climatic conditions. This report is part of a long-term study of water and carbon fluxes in a drip-irrigated olive grove in sandy soil, located in the Pisco province in Peru (13°45'03.25" S, 76°09'36.77" W at 74 m elevation). Due to the absence of precipitation during the main growing season, plants depend on the local aquifer and drip irrigation for growth and yields. We installed an eddy covariance system in September of 2019 in a 9 m tower over a 5 m canopy height. The canopy covered 60% of the surface, the rest being sandy soil with very limited grass cover. The flux footprint of the system covered 3 ha for 80% of the information gathered. Peak average hourly water flux from the grove to the atmosphere in the summer season took place at 1 pm, with values of 1.8 m3 ha-1 h-1. Average daily fluxes ranged from 5 m3 ha-1 day-1 in August (winter) to 20 m3 ha-1 day-1 in February (summer). EddyPro-calculated ET values are essentially similar and represent 41% of ETo as calculated by the Penman-Monteith equation and 58.6% using a crop coefficient correction. Drip irrigation was set at 63 m3 ha-1 day-1 during the growing season (October through April) and reduced to half that amount in the winter. Optimization of water usage in relation to productivity has been pursued by monitoring photosynthetic efficiency and transpiration with an Li 6800 system in sun and shade leaves of the canopy along with use of Ekomatik digital dendrometer monitoring as a proxy for sap flow.

The divergence between the disappearance of primary forests and the appearance of secondary forests indicates a set of circumstances that simultaneously converge in what we called the society-agriculture-forest complex. Such circumstances vary between places and over time and are associated with internal factors-factors originating within the reference system-and external factors-factors originating outside the borders of the reference system-restrict the use of standard strategies for any reality. We present a quantitative model that helps to understand the relationships of the society-agriculture-forest complex as a whole. This comprehensive understanding will allow a clearer discussion of the positive and negative consequences of prioritizing actions on any of the system components. Our model establishes a set of quantitative relationships among: (i) the requirements of food and timber products for society to maintain its structure and functionality, (ii) the level of openness of the society with respect to other societies for the exchange of resources, and (iii) the interface between the economic productive systems and the ecological productive systems. To test the model, the case of Huayopata (Peru) was studied. Findings suggest that the abandonment of agricultural production and, particularly, of tea favors the appearance of secondary forests. However, projects by the Congress of Peru to reactivate the production of tea without adequate technological support to improve the current processes that use firewood for boilers would put the forestry system at risk. In addition, a potential worker 'pull factor' could reconfigure the food system and impact on the local agricultural sector.The online version contains supplementary material available at 10.1007/s10668-022-02457-6.

This chapter describes the diversity of plants and ecosystems in the lowland Amazon and discusses how complex regional gradients in climate and soil conditions drive regional variability in species composition, vegetation dynamics, carbon stocks, and productivity. The Amazon river network and its role in connecting aquatic and terrestrial ecosystems through organisms and nutrient exchanges is also emphasized.

This chapter presents observed and predicted impacts of climate change on Amazonian ecosystems, focusing on biodiversity, ecosystem services, carbon cycling, fisheries, and emissions from biomass burning. It also considers climate and land-use change feedbacks and highlights knowledge gaps to better understand these complex interactions.

Tropical forests are some of the most biodiverse ecosystems in the world, yet their functioning is threatened by anthropogenic disturbances and climate change. Global actions to conserve tropical forests could be enhanced by having local knowledge on the forestsʼ functional diversity and functional redundancy as proxies for their capacity to respond to global environmental change. Here we create estimates of plant functional diversity and redundancy across the tropics by combining a dataset of 16 morphological, chemical and photosynthetic plant traits sampled from 2,461 individual trees from 74 sites distributed across four continents together with local climate data for the past half century. Our findings suggest a strong link between climate and functional diversity and redundancy with the three trait groups responding similarly across the tropics and climate gradient. We show that drier tropical forests are overall less functionally diverse than wetter forests and that functional redundancy declines with increasing soil water and vapour pressure deficits. Areas with high functional diversity and high functional redundancy tend to better maintain ecosystem functioning, such as aboveground biomass, after extreme weather events. Our predictions suggest that the lower functional diversity and lower functional redundancy of drier tropical forests, in comparison with wetter forests, may leave them more at risk of shifting towards alternative states in face of further declines in water availability across tropical regions.

Tropical soils contain huge carbon stocks, which climate warming is projected to reduce by stimulating organic matter decomposition, creating a positive feedback that will promote further warming. Models predict that the loss of carbon from warming soils will be mediated by microbial physiology, but no empirical data are available on the response of soil carbon and microbial physiology to warming in tropical forests, which dominate the terrestrial carbon cycle. Here we show that warming caused a considerable loss of soil carbon that was enhanced by associated changes in microbial physiology. By translocating soils across a 3000 m elevation gradient in tropical forest, equivalent to a temperature change of ± 15 °C, we found that soil carbon declined over 5 years by 4% in response to each 1 °C increase in temperature. The total loss of carbon was related to its original quantity and lability, and was enhanced by changes in microbial physiology including increased microbial carbon‐use‐efficiency, shifts in community composition towards microbial taxa associated with warmer temperatures, and increased activity of hydrolytic enzymes. These findings suggest that microbial feedbacks will cause considerable loss of carbon from tropical forest soils in response to predicted climatic warming this century.

The functional traits of organisms within multispecies assemblages regulate biodiversity effects on ecosystem functioning. Yet how traits should assemble to boost multiple ecosystem functions simultaneously (multifunctionality) remains poorly explored. In a multibiome litter experiment covering most of the global variation in leaf trait spectra, we showed that three dimensions of functional diversity (dispersion, rarity, and evenness) explained up to 66% of variations in multifunctionality, although the dominant species and their traits remained an important predictor. While high dispersion impeded multifunctionality, increasing the evenness among functionally dissimilar species was a key dimension to promote higher multifunctionality and to reduce the abundance of plant pathogens. Because too-dissimilar species could have negative effects on ecosystems, our results highlight the need for not only diverse but also functionally even assemblages to promote multifunctionality. The effect of functionally rare species strongly shifted from positive to negative depending on their trait differences with the dominant species. Simultaneously managing the dispersion, evenness, and rarity in multispecies assemblages could be used to design assemblages aimed at maximizing multifunctionality independently of the biome, the identity of dominant species, or the range of trait values considered. Functional evenness and rarity offer promise to improve the management of terrestrial ecosystems and to limit plant disease risks., This work was funded by the British Ecological Society (SR17\1297 grant, PI: P.G.-P.) and by the European Research Council (ERC Grant Agreement #647038, BIODESERT, PI: F.T.M.). Y.L.B.-P. was supported by a Marie Sklodowska-Curie Actions Individual Fellowship within the European Program Horizon 2020 (DRYFUN Project #656035). H.S. was supported by a Juan de la Cierva-Formación grant from the Span ish Ministry of Economy and Competitiveness (FJCI-2015-26782). F.T.M. and S.A. were supported from the Generalitat Valenciana (CIDEGENT/ 2018/041). M.D. was supported by a Formación del Profesorado Universi tario (FPU) fellowship from the Spanish Ministry of Education, Culture and Sports (FPU-15/00392). S.A. was supported by the Spanish MINECO for financial support via the DIGGING_DEEPER project through the 2015 to 2016 BiodivERsA3/FACCE‐JPI joint call for research proposals. B.K.S. re search on biodiversity-ecosystem functions was supported by the Austra lian Research Council (DP170104634 and DP190103714). P.G.-P. was supported by a Ramón y Cajal grant from the Spanish Ministry of Science and Innovation (RYC2018-024766-I). R.M. was supported by MINECO (Grants CGL2014-56567-R and CGL2017-83855-R)

SummaryBiogeographic events occurring in the deep past can contribute to the structure of modern ecological communities. However, little is known about how the emergence of environmental gradients shape the evolution of species that underlie community assembly. In this study, we address how the creation of novel environments lead to community assembly via two non-mutually exclusive processes: 1) the immigration and ecological sorting of pre-adapted clades (ISPC), and 2) 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 communities across elevations.

3-hydroxy fatty acids (3-OH FAs) with 10 to 18 C atoms are membrane lipids mainly produced by Gram-negative bacteria. They have been recently proposed as temperature and pH proxies in terrestrial settings. Nevertheless, the existing correlations between pH/temperature and indices derived from 3-OH FA distribution (RIAN, RAN15 and RAN17) are based on a small soil dataset (ca. 70 samples) and only applicable regionally. The aim of this study was to investigate the applicability of 3-OH FAs as mean annual air temperature (MAAT) and pH proxies at the global level. This was achieved using an extended soil dataset of 168 topsoils distributed worldwide, covering a wide range of temperatures (5 °C to 30 °C) and pH (3 to 8). The response of 3-OH FAs to temperature and pH was compared to that of established branched GDGT-based proxies (MBT'5Me/CBT). Strong linear relationships between 3-OH FA-derived indices (RAN15, RAN17 and RIAN) and MAAT/pH could only be obtained locally, for some of the individual transects. This suggests that these indices cannot be used as paleoproxies at the global scale using simple linear regression models, in contrast with the MBT'5Me and CBT. However, strong global correlations between 3-OH FA relative abundances and MAAT/pH were shown by using other algorithms (multiple linear regression, k-NN and random forest models). The applicability of the k-NN and random forest models for paleotemperature reconstruction was tested and compared with the MAAT record from a Chinese speleothem. The calibration based on the random forest model appeared to be the most robust. It showed similar trends with previously available records and highlighted known climatic events poorly visible when using local 3-OH FA calibrations. Altogether, these results demonstrate the potential of 3-OH FAs as paleoproxies in terrestrial settings.

Forests are integral to global carbon cycling but are threatened by anthropogenic degradation and climate change. Assessing this global threat has been hindered by a lack of clear, flexible, and easy-to-use productivity models along with a lack of functional trait and productivity data for parameterizing and testing those models. Current productivity models are either extremely complex requiring up to hundreds of parameters, many sub-models, and considerable computational expense or rely on statistical trait-growth relationships that can be hard to extrapolate to new systems or climates. Here we provide a simple alternative: a remote sensing canopy functional model (RS-CFM) that uses remotely-sensed foliar traits and canopy structure data to efficiently map productivity at high-resolution and large spatial scales. We test this model by quantifying net primary productivity (NPP) at 0.01-ha resolution in 30,040 hectares of Peruvian tropical rainforest along a 3,322-m Amazon-to-Andes elevation gradient. Our model predicts local NPP and elevational shifts in NPP much more accurately and in greater detail than a prominent alternative method—NASA’s MODIS NPP product. Furthermore, we show how NPP estimates depend on light competition and identify the appropriate spatial resolution for remote productivity estimation. Our framework opens up possibilities to fully harness remote sensing data and reliably scale up from traits to map regional or global productivity in a more direct, efficient, and cost-effective manner.

Non-structural carbohydrates (NSC) are major substrates for plant metabolism and have been implicated in mediating drought-induced tree mortality. Despite their significance, NSC dynamics in tropical forests remain little studied. We present leaf and branch NSC data for 82 Amazon canopy tree species in six sites spanning a broad precipitation gradient. During the wet season, total NSC (NSCT) concentrations in both organs were remarkably similar across communities. However, NSCT and its soluble sugar (SS) and starch components varied much more across sites during the dry season. Notably, the proportion of leaf NSCT in the form of SS (SS:NSCT) increased greatly in the dry season in almost all species in the driest sites, implying an important role of SS in mediating water stress in these sites. This adjustment of leaf NSC balance was not observed in tree species less-adapted to water deficit, even under exceptionally dry conditions. Thus, leaf carbon metabolism may help to explain floristic sorting across water availability gradients in Amazonia and enable better prediction of forest responses to future climate change., The role of non-structural carbohydrates (NSC) in mediating the impacts of drought in tropical trees is unclear. Here, the authors analyse leaf and branch NSC in 82 Amazon tree species across a Basin-wide precipitation gradient, finding that allocation of leaf NSC to soluble sugars is higher in drier sites and is coupled to tree hydraulic status.

Understanding how evolutionary constraints shape the elevational distributions of tree lineages provides valuable insight into the future of tropical montane forests under global change. With narrow elevational ranges, high taxonomic turnover, frequent habitat specialisation, and exceptional levels of endemism, tropical montane forests and trees are predicted to be highly sensitive to environmental change. Using plot census data from a gradient traversing >3000 m in elevation on the Amazonian flank of the Peruvian Andes, we employ phylogenetic approaches to assess the influence of evolutionary heritage on distribution trends of trees at the genus level. We find that closely related lineages tend to occur at similar mean elevations, with sister genera pairs occurring a mean 254 m in elevation closer to each other than the mean elevational difference for all genera pairs. We also demonstrate phylogenetic clustering both above and below 1750 m a.s.l, corresponding roughly to the cloud-base ecotone. Belying these general trends, some lineages occur across many different elevations. However, these highly plastic lineages are not phylogenetically clustered. Overall, our findings suggest that tropical montane forests are home to unique tree lineage diversity, constrained by their evolutionary heritage and vulnerable to substantial losses under environmental changes, such as rising temperatures or an upward shift of the cloud base.

Highly weathered soils depleted in minerals and phosphorus (P) support large tracts of the tropical rainforests in the Central Amazon, which significantly contribute to the global carbon (C) sink. In these soils (oxisols and ferrasols), P is either occluded in Al/Fe-oxides, bound to the soil mineral matrix or in soil organic matter, and therefore not directly available for uptake as inorganic phosphate (Pi). To liberate Pi for plant or microbial uptake two processes are key: (i) changes of sorption-desorption equilibria of Pi with the soil matrix and (ii) the release of Pi from organic compounds (Po) catalyzed by enzymes, such as phosphatases. Plant roots and soil microbes have developed strategies to stimulate the release of P by accelerating P dissolution and desorption and by releasing extracellular phosphatases into the soil environment, which requires however C and energy investment. Because of P limitation in this ecosystem, the relative contributions of abiotic and biotic controls over P mineralization is of pivotal importance. Yet conclusive results are still scarce.We therefore aimed to disentangle abiotic and biotic controls over P mineralization in tropical soils. To achieve this, we collected forest soils from the Amazon Basin covering a range of soil texture and P concentrations, determined soil mineralogy and measured gross P desorption and mineralization rates using a 33P isotope pool dilution assay. Moreover, we determined acid phosphatase activity rates and microbial biomass C and P. We found significant differences between the studied sites in gross P influx and efflux rates into the Pi pool. Gross influx rates (i.e. the sum of Pi desorption and organic P mineralization) exceeded efflux (i.e. sorption or biotic Pi uptake rates) only in sandy and silty soils, while in clayey soils efflux rates dominated P fluxes indicating a very high Pi sorption capacity. However, gross influx and efflux rates were not related to total or dissolved P. Microbial biomass and acid phosphatase activity normalized to microbial biomass C were highest in sites with overall low total P microbial biomass P accounting for up to 40 % of total P in low P soils. We therefore conclude that in low P soils organic P turnover plays a major role in soil P cycling, and despite of the high P sorption capacity of clay rich soils, microbes can be strong competitors for plant available P.

Foliar trait adaptation to sun and shade has been extensively studied in the context of photosynthetic performance of plants, focusing on nitrogen allocation, light capture and use via chlorophyll pigments and leaf morphology; however, less is known about the potential sun-shade dichotomy of other functionally important foliar traits. In this study, we measured 19 traits in paired sun and shade leaves along a 3,500-m elevation gradient in southern Peru to test whether the traits differ with canopy position, and to assess if relative differences vary with species composition and/or environmental filters. We found significant sun-shade differences in leaf mass per area (LMA), photosynthetic pigments (Chl ab and Car), and δ13C. Sun-shade offsets among these traits remained constant with elevation, soil substrates, and species compositional changes. However, other foliar traits related to structure and chemical defense, and those defining general metabolic processes, did not differ with canopy position. Our results suggest that whole-canopy function is captured in many traits of sun leaves; however, photosynthesis-related traits must be scaled based on canopy light extinction. These findings show that top-of-canopy measurements of foliar chemistry from spectral remote sensing approaches map directly to whole-canopy foliar traits including shaded leaves that cannot be directly observed from above.

Tropical forest leaf albedo (reflectance) greatly impacts how much energy the planet absorbs; however; little is known about how it might be impacted by climate change. Here, we measure leaf traits and leaf albedo at ten 1-ha plots along a 3,200-m elevation gradient in Peru. Leaf mass per area (LMA) decreased with warmer temperatures along the elevation gradient; the distribution of LMA was positively skewed at all sites indicating a shift in LMA towards a warmer climate and future reduced tropical LMA. Reduced LMA was significantly (P

The response of soil microbial activity to climate warming has been predicted to have a large destabilising effect on the carbon cycle. However, the nature of this feedback remains poorly understood, especially in tropical ecosystems and across annual to decadal timescales. We studied the response of bacterial community growth to 2 and 11 years of altered temperature regimes, by translocating soil across an elevation gradient in the tropical Andes. Soil cores were reciprocally translocated among five sites across 3 km in elevation, where mean annual temperature (MAT) ranged from 26.4 to 6.5°C. The bacterial community growth response to temperature was estimated using a temperature Sensitivity Index (SI): the log-ratio of growth determined by leucine incorporation at 35°C: 4°C. Bacterial communities from soil translocated to their original site (controls) had a growth response assumed to be ‘adapted’ to the original MAT. Translocating soil downslope (warming) resulted in an increased SI relative to their original growth response, and vice versa under cooling, indicating community-level adaptation over the incubation period to the altered MAT. The average level of adaptation (i.e., the extent to which SI converged on the control values) was 77% after 2 years, and was complete after 11 years. The adaptive response was faster when soil was warmed rather than cooled: instances of complete adaptation of SI occurred in soils after 2 years when warmed, but only after 11 years when they were cooled. Taken together, our results show that the majority of the growth adaptation to warming by the bacterial community occurs rapidly, within 2 years, whilst growth adaptation to cooling occurs within a decade. Our analysis demonstrates rapid warm-adaptation of bacterial community growth, with potential consequences for the temperature sensitivity of soil carbon cycling in response to future climate warming.

Nutrients constrain the soil carbon cycle in tropical forests, but we lack knowledge on how these constraints vary within the soil microbial community. Here, we used in situ fertilization in a montane tropical forest and in two lowland tropical forests on contrasting soil types to test the principal hypothesis that there are different nutrient constraints to different groups of microorganisms during the decomposition of cellulose. We also tested the hypotheses that decomposers shift from nitrogen to phosphorus constraints from montane to lowland forests, respectively, and are further constrained by potassium and sodium deficiency in the western Amazon. Cellulose and nutrients (nitrogen, phosphorus, potassium, sodium, and combined) were added to soils in situ, and microbial growth on cellulose (phospholipid fatty acids and ergosterol) and respiration were measured. Microbial growth on cellulose after single nutrient additions was highest following nitrogen addition for fungi, suggesting nitrogen as the primary limiting nutrient for cellulose decomposition. This was observed at all sites, with no clear shift in nutrient constraints to decomposition between lowland and montane sites. We also observed positive respiration and fungal growth responses to sodium and potassium addition at one of the lowland sites. However, when phosphorus was added, and especially when added in combination with other nutrients, bacterial growth was highest, suggesting that bacteria out-compete fungi for nitrogen where phosphorus is abundant. In summary, nitrogen constrains fungal growth and cellulose decomposition in both lowland and montane tropical forest soils, but additional nutrients may also be of critical importance in determining the balance between fungal and bacterial decomposition of cellulose.

UK Natural Environment Research Council [NE/J023418/1, NE/M019160/1]; European Research Council [321131, 291585]; John D. and Catherine T. MacArthur Foundation; U.S. National Science Foundation [DEB - 1209287]; Carnegie Institution for Science; National Science Foundation [DEB - 1146206]; Leverhulme Trust, UK; Jackson Foundation; European Community [290605]; John Fell Fund; Google Earth Engine award

The carbon isotopic composition of plant leaf wax biomarkers is commonly used to reconstruct paleoenvironmental conditions. Adding to the limited calibration information available for modern tropical forests, we analyzed plant leaf and leaf wax carbon isotopic compositions in forest canopy trees across a highly biodiverse, 3.3 km elevation gradient on the eastern flank of the Andes Mountains. We sampled the dominant tree species and assessed their relative abundance in each tree community. In total, 405 sunlit canopy leaves were sampled across 129 species and nine forest plots along the elevation profile for bulk leaf and leaf wax n-alkane (C27–C33) concentration and carbon isotopic analyses (δ13C); a subset (76 individuals, 29 species, five forest plots) were additionally analyzed for n-alkanoic acid (C22–C32) concentrations and δ13C. δ13C values display trends of +0.87 ± 0.16‰ km−1 (95% CI, r2 = 0.96, p

The strength of biotic interactions is generally thought to increase toward the equator, but support for this hypothesis is contradictory. We explored whether predator attacks on artificial prey of eight different colors vary among climates and whether this variation affects the detection of latitudinal patterns in predation. Bird attack rates negatively correlated with model luminance in cold and temperate environments, but not in tropical environments. Bird predation on black and on white (extremes in luminance) models demonstrated different latitudinal patterns, presumably due to differences in prey conspicuousness between habitats with different light regimes. When attacks on models of all colors were combined, arthropod predation decreased, whereas bird predation increased with increasing latitude. We conclude that selection for prey coloration may vary geographically and according to predator identity, and that the importance of different predators may show contrasting patterns, thus weakening the overall latitudinal trend in top‐down control of herbivorous insects., We explored whether predator attacks on artificial prey of eight different colors vary among climates and whether this variation affects the detection of latitudinal patterns in predation. We found that selection for prey coloration varies geographically and according to predator identity. When attacks on models of all colors were combined, arthropod predation decreased, whereas bird predation increased with increasing latitude.

Many studies have tried to assess the role of both deterministic and stochastic processes in community assembly, yet a lack of consensus exists on which processes are more prevalent and at which spatial scales they operate. To shed light on this issue, we tested two nonmutually exclusive, scale-dependent hypotheses: (1) that competitive exclusion dominates at small spatial scales; and (2) that environmental filtering does so at larger ones. To accomplish this, we studied the functional patterns of tropical montane forest communities along two altitudinal gradients, in Ecuador and Peru, using floristic and functional data from 60 plots of 0.1 ha. We found no evidence of either functional overdispersion or clustering at small spatial scales, but we did find functional clustering at larger ones. The observed pattern of clustering, consistent with an environmental filtering process, was more evident when maximizing the environmental differences among any pair of plots. To strengthen the link between the observed community functional pattern and the underlying process of environmental filtering, we explored differences in the climatic preferences of the most abundant species found at lower and higher elevations and examined whether their abundances shifted along the elevation gradient. We found (1) that greater community functional differences (observed between lower and upper tropical montane forest assemblies) were mostly the result of strong climatic preferences, maintained across the Neotropics; and (2) that the abundances of such species shifted along the elevational gradient. Our findings support the conclusion that, at large spatial scales, environmental filtering is the overriding mechanism for community assembly, because the pattern of functional clustering was linked to species' similarities in their climatic preferences, which ultimately resulted in shifts in species abundances along the gradient. However, there was no evidence of competitive exclusion at more homogeneous, smaller spatial scales, where plant species effectively compete for resources.

Forest structure and composition play an essential role in determining the carbon storage capacity of tropical forests. Andean forests, with great potential for carbon accumulation, include large expanses of high-density woody bamboo communities. Woody bamboos can potentially alter forest structure, composition and dynamics and thus can affect carbon storage capacity; however, they are commonly excluded from forest monitoring and modelling. With the aim of documenting patterns of bamboo abundance and disentangling its association with forest structure, we carried out a bamboo census in seven 1-ha long-term forest monitoring plots situated across a large elevation gradient (1000–3600 m a.s.l.) in the Peruvian Andes. We determined that bamboo is a dominant plant group in the study area. In every plot, bamboos were the most common genera in terms of number of stems, and in two of the plots bamboo species were among those with the greatest basal area. We used a combination of Generalized linear mixed models (GLMM) and structural equation modelling (SEM) to hypothesize a causal framework and determine the direction and size of the effects of bamboo abundance (basal area) on number of individual trees, total tree basal area, mean tree basal area, mean tree growth rate and tree mortality rate. We found an overall negative association between bamboo abundance and total tree basal area driven mainly by reduced tree density (directly and indirectly mediated by an increase in tree mortality). However, the decrease in tree density and the increase in tree mortality are also associated with a small increase in tree diameter (mean tree basal area). Overall, the negative association between bamboo abundance and tree basal area suggests a lower biomass accumulation and thus a lower carbon storage capacity of trees in Andean forests where bamboo is dominant. Our results, which show the importance of bamboo in determining forest function, highlight the need for including bamboo in monitoring efforts and modeling studies.

A rich understanding of the productivity, carbon and nutrient cycling of terrestrial ecosystems is essential in the context of understanding, modelling and managing the future response of the biosphere to global change. This need is particularly acute in tropical ecosystems, home to over 60% of global terrestrial productivity, over half of planetary biodiversity, and hotspots of anthropogenic pressure. In recent years there has been a surge of activity in collecting data on the carbon cycle, productivity, and plant functional traits of tropical ecosystems, most intensively through the Global Ecosystems Monitoring network (GEM). The GEM approach provides valuable insights by linking field-based ecosystem ecology with the needs of Earth system science. In this paper, we review and synthesize the context, history and recent scientific output from the GEM network. Key insights have emerged on the spatial and temporal variability of ecosystem productivity and on the role of temperature and drought stress on ecosystem function and resilience. New work across the network is now linking carbon cycling to nutrient cycling and plant functional traits, and subsequently to airborne remote sensing. We discuss some of the novel emerging patterns and practical and methodological challenges of this approach, and examine current and possible future directions, both within this network and as lessons for a more general terrestrial ecosystem observation scheme.

Understanding variation in key functional traits across gradients in high diversity systems and the ecology of community changes along gradients in these systems is crucial in light of conservation and climate change. We examined inter- and intraspecific variation in leaf mass per area (LMA) of sun and shade leaves along a 3330-m elevation gradient in Peru, and in sun leaves across a forest–savanna vegetation gradient in Brazil. We also compared LMA variance ratios (T-statistics metrics) to null models to explore internal (i.e., abiotic) and environmental filtering on community structure along the gradients. Community-weighted LMA increased with decreasing forest cover in Brazil, likely due to increased light availability and water stress, and increased with elevation in Peru, consistent with the leaf economic spectrum strategy expected in colder, less productive environments. A very high species turnover was observed along both environmental gradients, and consequently, the first source of variation in LMA was species turnover. Variation in LMA at the genus or family levels was greater in Peru than in Brazil. Using dominant trees to examine possible filters on community assembly, we found that in Brazil, internal filtering was strongest in the forest, while environmental filtering was observed in the dry savanna. In Peru, internal filtering was observed along 80% of the gradient, perhaps due to variation in taxa or interspecific competition. Environmental filtering was observed at cloud zone edges and in lowlands, possibly due to water and nutrient availability, respectively. These results related to variation in LMA indicate that biodiversity in species rich tropical assemblages may be structured by differential niche-based processes. In the future, specific mechanisms generating these patterns of variation in leaf functional traits across tropical environmental gradients should be explored. Fil: Neyret, Margot. Ecole Normale Supérieure; Francia Fil: Bentley, Lisa Patrick. University of Oxford; Reino Unido. Sonoma State University; Estados Unidos Fil: Oliveras, Imma. University of Oxford; Reino Unido. Wageningen University; Alemania Fil: Marimon, Beatriz S.. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Marimon-Junior, Ben Hur. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Almeida de Oliveira, Edmar. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Barbosa Passos, Fabio. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Castro Ccoscco, Rosa. Universidad San Antonio Abad de Cusco; Perú Fil: Santos, Josias dos. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Matias Reis, Simone. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Morandi, Paulo S.. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Rayme Paucar, Gloria. Universidad San Antonio Abad de Cusco; Perú Fil: Robles Caceres, Arturo. Universidad San Antonio Abad de Cusco; Perú Fil: Valdez Tejeira, Yolvi. Universidad San Antonio Abad de Cusco; Perú Fil: Yllanes Choque, Yovana. Universidad San Antonio Abad de Cusco; Perú Fil: Salinas, Norma Beatriz. University of Oxford; Reino Unido. Pontificia Universidad Católica de Perú; Perú Fil: Shenkin, Alexander. University of Oxford; Reino Unido Fil: Asner, Gregory P.. Carnegie Institution for Science. Department of Global Ecology; Estados Unidos Fil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Enquist, Brian J.. Arizona State University; Estados Unidos Fil: Malhi, Yadvinder. University of Oxford; Reino Unido

We examined whether variations in photosynthetic capacity are linked to variations in the environment and/or associated leaf traits for tropical moist forests (TMFs) in the Andes/western Amazon regions of Peru. We compared photosynthetic capacity (maximal rate of carboxylation of Rubisco (Vcmax), and the maximum rate of electron transport (Jmax)), leaf mass, nitrogen (N) and phosphorus (P) per unit leaf area (Ma, Na and Pa, respectively), and chlorophyll from 210 species at 18 field sites along a 3300-m elevation gradient. Western blots were used to quantify the abundance of the CO2-fixing enzyme Rubisco. Area- and N-based rates of photosynthetic capacity at 25°C were higher in upland than lowland TMFs, underpinned by greater investment of N in photosynthesis in high-elevation trees. Soil [P] and leaf Pa were key explanatory factors for models of area-based Vcmax and Jmax but did not account for variations in photosynthetic N-use efficiency. At any given Na and Pa, the fraction of N allocated to photosynthesis was higher in upland than lowland species. For a small subset of lowland TMF trees examined, a substantial fraction of Rubisco was inactive. These results highlight the importance of soil- and leaf-P in defining the photosynthetic capacity of TMFs, with variations in N allocation and Rubisco activation state further influencing photosynthetic rates and N-use efficiency of these critically important forests. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust

Average responses of forest foliar traits to elevation are well understood, but far less is known about trait distributional responses to elevation at multiple ecological scales. This limits our understanding of the ecological scales at which trait variation occurs in response to environmental drivers and change. We analyzed and compared multiple canopy foliar trait distributions using field sampling and airborne imaging spectroscopy along an Andes-to-Amazon elevation gradient. Field-estimated traits were generated from three community-weighting methods, and remotely sensed estimates of traits were made at three scales defined by sampling grain size and ecological extent. Field and remote sensing approaches revealed increases in average leaf mass per unit area (LMA), water, nonstructural carbohydrates (NSCs) and polyphenols with increasing elevation. Foliar nutrients and photosynthetic pigments displayed little to no elevation trend. Sample weighting approaches had little impact on field-estimated trait responses to elevation. Plot representativeness of trait distributions at landscape scales decreased with increasing elevation. Remote sensing indicated elevation-dependent increases in trait variance and distributional skew. Multiscale invariance of LMA, leaf water and NSC mark these traits as candidates for tracking forest responses to changing climate. Trait-based ecological studies can be greatly enhanced with multiscale studies made possible by imaging spectroscopy. Fil: Asner, Gregory P.. Carnegie Institution for Science. Department of Global Ecology; Estados Unidos Fil: Martin, Roberta E.. Carnegie Institution for Science. Department of Global Ecology; Estados Unidos Fil: Anderson, Christopher Brian. Carnegie Institution for Science. Department of Global Ecology; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Kryston, Katherine. Carnegie Institution for Science. Department of Global Ecology; Estados Unidos Fil: Vaughn, Nicholas. Carnegie Institution for Science. Department of Global Ecology; Estados Unidos Fil: Knapp, David E.. Carnegie Institution for Science. Department of Global Ecology; Estados Unidos Fil: Bentley, Lisa Patrick. University of Oxford; Reino Unido Fil: Shenkin, Alexander. University of Oxford; Reino Unido Fil: Salinas, Norma. University of Oxford; Reino Unido. Pontificia Universidad Católica de Perú; Perú Fil: Sinca, Felipe. Carnegie Institution for Science. Department of Global Ecology; Estados Unidos Fil: Tupayachi, Raul. Carnegie Institution for Science. Department of Global Ecology; Estados Unidos Fil: Quispe Huaypar, Katherine. Universidad Nacional de San Antonio Abad del Cusco; Perú Fil: Montoya Pillco, Milenka. Universidad Nacional de San Antonio Abad del Cusco; Perú Fil: Ccori Álvarez, Flor Delis. Universidad Nacional de San Antonio Abad del Cusco; Perú Fil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Enquist, Brian J.. Arizona State University; Estados Unidos Fil: Malhi, Yadvinder. University of Oxford; Reino Unido

Plant leaf waxes have been found to record the hydrogen isotopic composition of precipitation and are thus used to reconstruct past climate. To assess how faithfully they record hydrological signals, we characterize leaf wax hydrogen isotopic compositions in forest canopy trees across a highly biodiverse, 3 km elevation range on the eastern flank of the Andes. We sampled the dominant tree species and assessed their relative abundance in the tree community. For each tree we collected xylem and leaf samples for analysis of plant water and plant leaf wax hydrogen isotopic compositions. In total, 176 individuals were sampled across 32 species and 5 forest plots that span the gradient. We find both xylem water and leaf wax δD values of individuals correlate (R2 = 0.8 and R2 = 0.3 respectively) with the isotopic composition of precipitation (with an elevation gradient of −21‰ km−1). Minimal leaf water enrichment means that leaf waxes are straightforward recorders of the isotopic composition of precipitation in wet climates. For these tropical forests we find the average fractionation between source water and leaf wax for C29 n-alkanes, −129 ± 2‰ (s.e.m., n = 136), to be indistinguishable from that of temperate moist forests. For C28 n-alkanoic acids the average fractionation is −121 ± 3‰ (s.e.m., n = 102). Sampling guided by community assembly within forest plots shows that integrated plant leaf wax hydrogen isotopic compositions faithfully record the gradient of isotopes in precipitation with elevation (R2 = 0.97 for n-alkanes and 0.60 for n-alkanoic acids). This calibration study supports the use of leaf waxes as recorders of the isotopic composition of precipitation in lowland tropical rainforest, tropical montane cloud forests and their sedimentary archives.

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 Peru, 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.

The temperature sensitivity of soil organic matter (SOM) decomposition in tropical forests will influence future climate. Studies of a 3.5-kilometer elevation gradient in the Peruvian Andes, including short-term translocation experiments and the examination of the long-term adaptation of biota to local thermal and edaphic conditions, have revealed several factors that may regulate this sensitivity. Collectively this work suggests that, in the absence of a moisture constraint, the temperature sensitivity of decomposition is regulated by the chemical composition of plant debris (litter) and both the physical and chemical composition of preexisting SOM: higher temperature sensitivities are found in litter or SOM that is more chemically complex and in SOM that is less occluded within aggregates. In addition, the temperature sensitivity of SOM in tropical montane forests may be larger than previously recognized because of the presence of “cold-adapted” and nitrogen-limited microbial decomposers and the possible future alterations in plant and microbial communities associated with warming. Studies along elevation transects, such as those reviewed here, can reveal factors that will regulate the temperature sensitivity of SOM. They can also complement and guide in situ soil-warming experiments, which will be needed to understand how this vulnerability to temperature may be mediated by altered plant productivity under future climatic change.

Understanding the relationship between photosynthesis, net primary productivity and growth in forest ecosystems is key to understanding how these ecosystems will respond to global anthropogenic change, yet the linkages among these components are rarely explored in detail. We provide the first comprehensive description of the productivity, respiration and carbon allocation of contrasting lowland Amazonian forests spanning gradients in seasonal water deficit and soil fertility. Using the largest data set assembled to date, ten sites in three countries all studied with a standardized methodology, we find that (i) gross primary productivity (GPP) has a simple relationship with seasonal water deficit, but that (ii) site-to-site variations in GPP have little power in explaining site-to-site spatial variations in net primary productivity (NPP) or growth because of concomitant changes in carbon use efficiency (CUE), and conversely, the woody growth rate of a tropical forest is a very poor proxy for its productivity. Moreover, (iii) spatial patterns of biomass are much more driven by patterns of residence times (i.e. tree mortality rates) than by spatial variation in productivity or tree growth. Current theory and models of tropical forest carbon cycling under projected scenarios of global atmospheric change can benefit from advancing beyond a focus on GPP. By improving our understanding of poorly understood processes such as CUE, NPP allocation and biomass turnover times, we can provide more complete and mechanistic approaches to linking climate and tropical forest carbon cycling.

Soils store about four times as much carbon as plant biomass1, and soil microbial respiration releases about 60 petagrams of carbon per year to the atmosphere as carbon dioxide2. Short-term experiments have shown that soil microbial respiration increases exponentially with temperature3. This information has been incorporated into soil carbon and Earth-system models, which suggest that warming-induced increases in carbon dioxide release from soils represent an important positive feedback loop that could influence twenty-first-century climate change4. The magnitude of this feedback remains uncertain, however, not least because the response of soil microbial communities to changing temperatures has the potential to either decrease5,6,7 or increase8,9 warming-induced carbon losses substantially. Here we collect soils from different ecosystems along a climate gradient from the Arctic to the Amazon and investigate how microbial community-level responses control the temperature sensitivity of soil respiration. We find that the microbial community-level response more often enhances than reduces the mid- to long-term (90 days) temperature sensitivity of respiration. Furthermore, the strongest enhancing responses were observed in soils with high carbon-to-nitrogen ratios and in soils from cold climatic regions. After 90 days, microbial community responses increased the temperature sensitivity of respiration in high-latitude soils by a factor of 1.4 compared to the instantaneous temperature response. This suggests that the substantial carbon stores in Arctic and boreal soils could be more vulnerable to climate warming than currently predicted. This work was carried out with Natural Environment Research Council (NERC) funding (grant number NE/H022333/1). K.K. was supported by an Academy of Finland post-doctoral research grant while finalizing this manuscript. P.M. was supported by ARC FT110100457 and NERC NE/G018278/1, and B.K.S by the Grain Research and Development Corporation and ARC DP130104841.

Solar irradiance and precipitation are the most likely drivers of the seasonal variation of net primary productivity (NPP) in tropical forests. Since their roles remain poorly understood, we use litter traps, dendrometer bands and census data collected from one hectare permanent plots to quantify the seasonality of above-groundNPPcomponents and weather parameters in 13 sites distributed along a 2800-m altitudinal gradient ranging from lowland Amazonia to the high Andes. We combine canopy leaf area index and litterfall data to describe the seasonality of canopy production. We hypothesize that solar irradiance is the primary driver of canopy phenology in wetter sites, whereas precipitation drives phenology in drier systems. The seasonal rhythm of canopyNPPcomponents is in synchrony with solar irradiance at all altitudes. Leaf litterfall peaks in the late dry season, both in lowland (averaging 0.54 ± 0.08 Mg C ha y−1, n = 5) and montane forests (averaging 0.29 ± 0.04 Mg C ha y−1, n = 8). Peaks in above-ground coarse woodyNPPappears to be triggered by the onset of rainfall in seasonal lowland rain forests (averaging 0.26 ± 0.04 Mg C ha y−1, n = 5, in November), but not in montane cloud forests.