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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)

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 specialization, 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 > 3,000 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 between non‐sister genera pairs. We also demonstrate phylogenetic clustering both above and below 1,750 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.

Andean tropical montane forests (TMF) are hotspots of biodiversity that provide fundamental hydrological services as well as carbon sequestration and storage. Agroforestry systems occupy large areas in the Andes but climatic pressures, market volatility and diseases may result inagroforest abandonment, promoting secondary succession. Secondary forests are well-adapted and efficient carbon sinks whose conservation is vital to mitigate and adapt to climate change and to support biodiversity. Little is known, however, about how secondary TMF recover their aboveground biomass (AGB) and composition after abandonment. We established a 1.5 ha plot at 1780 masl on a 30-year old abandoned agroforest and compared it against two control forest plots at similar elevations. Agroforestry legacies influenced AGB leading to far lower stocks (42.3 +/- 5.4-59.6 +/- 7.9 Mg ha(-1) using allometric equations) than those expected after 30 years (106 +/- 33 Mg ha(-1)) based on IPCC standard growth rates for secondary montane forests. This suggests a regional overestimation of mitigation potentials when using IPCC standards. Satellite-derived AGB largely overestimated our plot values (179 +/- 27.3 Mg ha(-1)). Secondary growth rates (1.41-2.0 Mg ha(-1) yr(-1) for DBH >= 10 cm) indicate recovery times of ca. 69 to 97 years to reach average control AGB values (137 +/- 12.3 Mg ha(-1)). This is 26 years above the average residence time of montane forests at our elevation (71 +/- 1.91 years) suggesting a non-recovery or far slower recovery to control AGB values. Three variables appear to define this outcome compared to the control plots: lower DBH (15.8 +/- 5.9 cm vs 19.8 +/- 11.0 cm), lower basal area (12.67 +/- 0.7 vs 28.03 +/- 1.5 m(2) ha(-1)) and higher abundance of lighter-wood tree genera (0.46 +/- 0.10 vs 0.57 +/- 0.11 gr cm(3)) such as Inga, a common shade-tree in Andean agroforests. With 3.2 million hectares committed to restoration, Peru needs to target currently neglected TMF recovery schemes to support biodiversity, water and carbon storage and fulfill its international commitments. This work was supported by a CONCYTEC (Peru) -World Bank grant (Contract 011-2019-FONDECYT-BM-INC-INV). In Huayopata we thank the Cuba and Povea families for their hospitality and help during field work.

Tropical forest ecosystems are undergoing rapid transformation as a result of changing environmental conditions and direct human impacts. However, we cannot adequately understand, monitor or simulate tropical ecosystem responses to environmental changes without capturing the high diversity of plant functional characteristics in the species-rich tropics. Failure to do so can oversimplify our understanding of ecosystems responses to environmental disturbances. Innovative methods and data products are needed to track changes in functional trait composition in tropical forest ecosystems through time and space. This study aimed to track key functional traits by coupling Sentinel-2 derived variables with a unique data set of precisely located in-situ measurements of canopy functional traits collected from 2434 individual trees across the tropics using a standardised methodology. The functional traits and vegetation censuses were collected from 47 field plots in the countries of Australia, Brazil, Peru, Gabon, Ghana, and Malaysia, which span the four tropical continents. The spatial positions of individual trees above 10 cm diameter at breast height (DBH) were mapped and their canopy size and shape recorded. Using geo-located tree canopy size and shape data, community-level trait values were estimated at the same spatial resolution as Sentinel-2 imagery (i.e. 10 m pixels). We then used the Geographic Random Forest (GRF) to model and predict functional traits across our plots. We demonstrate that key plant functional traits can be accurately predicted across the tropicsusing the high spatial and spectral resolution of Sentinel-2 imagery in conjunction with climatic and soil information. Image textural parameters were found to be key components of remote sensing information for predicting functional traits across tropical forests and woody savannas. Leaf thickness (R2 = 0.52) obtained the highest prediction accuracy among the morphological and structural traits and leaf carbon content (R2 = 0.70) and maximum rates of photosynthesis (R2 = 0.67) obtained the highest prediction accuracy for leaf chemistry and photosynthesis related traits, respectively. Overall, the highest prediction accuracy was obtained for leaf chemistry and photosynthetic traits in comparison to morphological and structural traits. Our approach offers new opportunities for mapping, monitoring and understanding biodiversity and ecosystem change in the most species-rich ecosystems on Earth.

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.

The sizes and shapes of tree crowns are of fundamental importance in ecology, yet understanding the forces that determine them remains elusive. A cardinal question facing ecologists is the degree to which general and non-specific versus ecological and context-dependent processes are responsible for shaping tree crowns. Here, we test this question for the first time across diverse tropical ecosystems. Using trees from 20 plots varying in elevation, precipitation, and ecosystem type (savanna-forest transitions) across the paleo- and neo-tropics, we test the relationship between crown dimensions and tree size. By analyzing these scaling relationships across environmental gradients, biogeographic regions, and phylogenetic distance, we extend Metabolic Scaling Theory (MST) predictions to include how local selective pressures shape variation in crown dimensions. Across all sites, we find strong agreement between mean trends and MST predictions for the scaling of crown size and shape, but large variation around the mean. While MST explained approximately half of the observed variation in tree crown dimensions, we find that local, ecosystem, and phylogenetic predictors account for the half of the residual variation. Crown scaling does not change significantly across regions, but does change across ecosystem types, where savanna tree crowns grow more quickly with tree girth than forest tree crowns. Crowns of legumes were wider and more voluminous than those of other taxa. Thus, while MST can accurately describe the central tendency of tree crown size, local ecological conditions and evolutionary history appear to modify the scaling of crown shape. Importantly, our extension of MST incorporating these differences accounts for the mechanisms driving variation in the scaling of crown dimensions across the tropics. We present allometric equations for the prediction of crown dimensions across tropical ecosystems. These results are critical when scaling the function of individual trees to larger spatial scales or incorporating the size and shape of tree crowns in global biogeochemical models.

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.

Deconstructing functional trait variation and co-variation across a wide range of environmental conditions is necessary to increase the mechanistic understanding of community assembly processes and improve current parameterization of dynamic vegetation models. Here, we present a study that deconstructs leaf trait variation and co-variation into within-species, taxonomic-, and plot-environment components along three tropical environmental gradients in Peru, Brazil, and Ghana. To do so, we measured photosynthetic, chemical, and structural leaf traits using a standardized sampling protocol for more than 1,000 individuals belonging to 367 species. Variation associated with the taxonomic component (species + genus + family) for most traits was relatively consistent across environmental gradients, but within-species variation and plot-environment variation was strongly dependent on the environmental gradient. Trait-trait co-variation was strongly linked to the environmental gradient where traits were measured, although some traits had consistent co-variation components irrespective of gradient. Our results demonstrate that filtering along these tropical gradients is mostly expressed through trait taxonomic variation, but that trait co-variation is strongly dependent on the local environment, and thus global trait co-variation relationships might not always apply at smaller scales and may quickly change under future climate scenarios. Fil: Oliveras, Imma. University of Oxford; Reino Unido Fil: Bentley, Lisa. Sonoma State University; Estados Unidos Fil: Fyllas, Nikolaos M.. University Of The Aegean; Grecia Fil: Gvozdevaite, Agne. University of Oxford; Reino Unido Fil: Shenkin, Alexander Frederick. University of Oxford; Reino Unido Fil: Peprah, Theresa. Forestry Research Institute Of Ghana; Ghana Fil: Morandi, Paulo. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Peixoto, Karine Silva. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Boakye, Mickey. Forestry Research Institute Of Ghana; Ghana Fil: Adu-Bredu, Stephen. Csir - Forestry Research Institute Of Ghana; Ghana Fil: Schwantes Marimon, Beatriz. Universidade Do Estado de Mato Grosso; Brasil Fil: Marimon Junior, Ben Hur. Universidade Do Estado de Mato Grosso; Brasil Fil: Salinas, Norma. Pontificia Universidad Católica de Perú; Perú Fil: Martin, Roberta. Arizona State University; Estados Unidos Fil: Asner, Gregory. Arizona State University; 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.. University of Arizona; Estados Unidos Fil: Malhi, Yadvinder. University of Oxford; Reino Unido

Ultraviolet (UV) radiation is a small fraction of the solar spectrum, which acts as a key environmental modulator of plant function affecting metabolic regulation and growth. Plant species endemic to the Andes are well adapted to the harsh features of high-altitude climate, including high UV radiation. Maca (Lepidium meyenii Walpers) is a member of Brassicaceae family native to the central Andes of Peru, which grows between 3500 and 4500 m of altitude, where only highland grasses and few hardy bushes can survive. Even though maca has been the focus of recent researches, mainly due to its nutraceutical properties, knowledge regarding its adaptation mechanisms to these particular natural environmental conditions is scarce. In this study, we manipulated solar UV radiation by using UV-transmitting (Control) or blocking (UV-block) filters under field conditions (4138 m above the sea level) in order to understand the impact of UV on morphological and physiological parameters of maca crops over a complete growing season. Compared to the UV-blocking filter, under control condition a significant increase of hypocotyl weight was observed during the vegetative phase together with a marked leaf turnover. Although parameters conferring photosynthetic performance were not altered by UV, carbohydrate allocation between above and underground organs was affected. Control condition did not influence the content of secondary metabolites such as glucosinolates and phenolic compounds in hypocotyls, while some differences were observed in the rosettes. These differences were mainly related to leaf turnover and the protection of new young leaves in control plants. Altogether, the data suggest that maca plants respond to strong UV radiation at high altitudes by a coordinated remobilization and relocation of metabolites between source and sink organs via a possible UV signaling pathway.

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

Remote sensing of trait-based ecology can improve our understanding of the effect of trait diversity on ecosystem functioning., Spatially continuous data on functional diversity will improve our ability to predict global change impacts on ecosystem properties. We applied methods that combine imaging spectroscopy and foliar traits to estimate remotely sensed functional diversity in tropical forests across an Amazon-to-Andes elevation gradient (215 to 3537 m). We evaluated the scale dependency of community assembly processes and examined whether tropical forest productivity could be predicted by remotely sensed functional diversity. Functional richness of the community decreased with increasing elevation. Scale-dependent signals of trait convergence, consistent with environmental filtering, play an important role in explaining the range of trait variation within each site and along elevation. Single- and multitrait remotely sensed measures of functional diversity were important predictors of variation in rates of net and gross primary productivity. Our findings highlight the potential of remotely sensed functional diversity to inform trait-based ecology and trait diversity-ecosystem function linkages in hyperdiverse tropical forests.

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

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.

Wet organic-rich mineral and peat soils in the tropical Andes represent a potentially significant, but little studied, source of methane to the atmosphere. Here we report the results of field and laboratory measurements of soil&ndash, atmosphere methane exchange and associated environmental variables from freely draining upland and inundation prone wetland soils in a humid puna ecosystem in the Southeastern Andes of Peru. Between seasons and across the landscape soil&ndash, atmosphere exchange varied between uptake and emission. Notable hotspots of methane emission, peaking during the wet season, were observed from both upland and wetland soils with particularly strong emissions from moss-accumulating topographic lows. This variability was best explained by the influence of oxygen concentration on methane production in superficial soil horizons.

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.

More than 200 years ago, Alexander von Humboldt reported that tropical plant species richness decreased with increasing elevation and decreasing temperature. Surprisingly, coordinated patterns in plant, bacterial, and fungal diversity on tropical mountains have not yet been observed, despite the central role of soil microorganisms in terrestrial biogeochemistry and ecology. We studied an Andean transect traversing 3.5 km in elevation to test whether the species diversity and composition of tropical forest plants, soil bacteria, and fungi follow similar biogeographical patterns with shared environmental drivers. We found coordinated changes with elevation in all three groups: species richness declined as elevation increased, and the compositional dissimilarity among communities increased with increased separation in elevation, although changes in plant diversity were larger than in bacteria and fungi. Temperature was the dominant driver of these diversity gradients, with weak influences of edaphic properties, including soil pH. The gradients in microbial diversity were strongly correlated with the activities of enzymes involved in organic matter cycling, and were accompanied by a transition in microbial traits towards slower‐growing, oligotrophic taxa at higher elevations. We provide the first evidence of coordinated temperature‐driven patterns in the diversity and distribution of three major biotic groups in tropical ecosystems: soil bacteria, fungi, and plants. These findings suggest that interrelated and fundamental patterns of plant and microbial communities with shared environmental drivers occur across landscape scales. These patterns are revealed where soil pH is relatively constant, and have implications for tropical forest communities under future climate change.

Los bosques primarios intactos de la Amazonía peruana se comportan como sumideros de carbono: un servicio ecosistémico clave a nivel mundial. Este sumidero fue cuantificado en 0.54 Mg C ha-1 año-1 (1990-2017) para los bosques amazónicos intactos de las Áreas Naturales Protegidas (ANPs) de Perú y las zonas de amortiguamiento. En otras palabras, la conservación de bosques intactos en ANPs ayudó a remover 9.6 millones de toneladas de carbono de la atmósfera por año, lo cual equivale aproximadamente al 85% de las emisiones de la quema de combustibles fósiles del país durante el 2012. Este servicio de remoción de CO2 atmosférico es necesario incluir en el inventario nacional de gases de efecto invernadero, y en los compromisos nacionales de reducción de emisiones, por dos razones. Primero, debido a ser un flujo importante, nos ayudaría a tener una aproximación más real del balance de carbono en Perú. Segundo, fortalecería la necesidad de mantener la integridad de estos bosques tanto por el servicio de almacenamiento de carbono (evitar emisiones) como el servicio de sumidero (remoción de emisiones) y la diversidad biológica que albergan. La provisión del servicio de sumidero solo se asegurará con una gestión efectiva y adaptativa de las ANPs. El reporte de este servicio ambiental a nivel nacional debe ser implementado a través del monitoreo a largo plazo de la dinámica del carbono y el impacto del cambio climático a través de la red de parcelas forestales permanentes de RAINFOR (Red Amazónica de Inventarios Forestales) y el proyecto MonANPeru. El establecimiento de este sistema de monitoreo permitirá el desarrollo de los mecanismos financieros para cerrar la brecha y lograr la sostenibilidad de la conservación de los bosques en las ANPs de Perú. The primary intact forests of the Peruvian Amazon act as a carbon sink: a key ecosystem service of international importance. This sink has been quantified as 0.54 Mg C ha-1 year-1 (1990-2017) for the intact Amazonian forest in the protected areas and associated buffer zones of Peru. In other words, the conservation of intact forests in protected areas has helped to remove 9.6 million tonnes of carbon from the atmosphere per year, which is equivalent to approximately 85% of the emissions from fossil fuel combustion in Peru during 2012. It is necessary to include this carbon sink in the national inventory of greenhouse gas emissions for two reasons. Firstly, because it is a an important flux, it would help for estimating the carbon balance of Peru more accurately. Secondly, it would strengthen the need to maintain the integrity of these forests, for their role both as a stock and sink of carbon and for their biological diversity. The provision of this service as a sink can only be assured with effective and adaptive management of the protected areas of Peru. Reporting of this environmental service at a national level should be implemented through long-term monitoring of the carbon dynamics and impact of climate change on these forests via the RAINFOR (Amazon Forest Network) network of permanent forest plots and the MonANPeru project. The establishment of this monitoring system would allow the development of the finanancial mechanisms to close the funding gap and achieve sustainable conservation of the forests of the protected area network of Peru.

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.

Aim: To examine variation in the phylogenetic diversity (PD) of tree communities across geographical and environmental gradients in Amazonia. Location: Two hundred and eighty-three c. 1 ha forest inventory plots from across Amazonia. Methods: We evaluated PD as the total phylogenetic branch length across species in each plot (PDss), the mean pairwise phylogenetic distance between species (MPD), the mean nearest taxon distance (MNTD) and their equivalents standardized for species richness (ses.PDss, ses.MPD, ses.MNTD). We compared PD of tree communities growing (1) on substrates of varying geological age; and (2) in environments with varying ecophysiological barriers to growth and survival. Results: PDss is strongly positively correlated with species richness (SR), whereas MNTD has a negative correlation. Communities on geologically young- and intermediate-aged substrates (western and central Amazonia respectively) have the highest SR, and therefore the highest PDss and the lowest MNTD. We find that the youngest and oldest substrates (the latter on the Brazilian and Guiana Shields) have the highest ses.PDss and ses.MNTD. MPD and ses.MPD are strongly correlated with how evenly taxa are distributed among the three principal angiosperm clades and are both highest in western Amazonia. Meanwhile, seasonally dry tropical forest (SDTF) and forests on white sands have low PD, as evaluated by any metric. Main conclusions: High ses.PDss and ses.MNTD reflect greater lineage diversity in communities. We suggest that high ses.PDss and ses.MNTD in western Amazonia results from its favourable, easy-to-colonize environment, whereas high values in the Brazilian and Guianan Shields may be due to accumulation of lineages over a longer period of time. White-sand forests and SDTF are dominated by close relatives from fewer lineages, perhaps reflecting ecophysiological barriers that are difficult to surmount evolutionarily. Because MPD and ses.MPD do not reflect lineage diversity per se, we suggest that PDss, ses.PDss and ses.MNTD may be the most useful diversity metrics for setting large-scale conservation priorities. © 2015 John Wiley & Sons Ltd.

One of the major challenges in ecology is to understand how ecosystems respond to changes inenvironmental conditions, and how taxonomic and functional diversity mediate these changes. Inthis study, we use a trait-spectra and individual-based model, to analyse variation in forest primaryproductivity along a 3.3 km elevation gradient in the Amazon-Andes. The model accuratelypredicted the magnitude and trends in forest productivity with elevation, with solar radiation andplant functional traits (leaf dry mass per area, leaf nitrogen and phosphorus concentration, andwood density) collectively accounting for productivity variation. Remarkably, explicit representationof temperature variation with elevation was not required to achieve accurate predictions offorest productivity, as trait variation driven by species turnover appears to capture the effect oftemperature. Our semi-mechanistic model suggests that spatial variation in traits can potentiallybe used to estimate spatial variation in productivity at the landscape scale. Fil: Fyllas, Nikolaos M.. University of Oxford; Reino Unido Fil: Patrick Bentley, Lisa. University of Oxford; Reino Unido Fil: Shenkin, Alexander. University of Oxford; Reino Unido Fil: Asner, Gregory P.. Carnegie Institution for Science. Department of Global Ecology; Reino Unido Fil: Atkin, Owen K.. The Australian National University. ARC Centre of Excellence in Plant Energy Biology. Research School of Biology; Australia 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: Farfan Rios, William. University Wake Forest; Estados Unidos Fil: Gloor, Emanuel. University of Leeds; Reino Unido Fil: Guerrieri, Rossella. Universitat Autònoma de Barcelona; España. University of Edinburgh; Reino Unido Fil: Huaraca Huasco, Walter. Universidad Nacional de San Antonio Abad del Cusco; Perú Fil: Ishida, Yoko. James Cook University; Australia Fil: Martin, Roberta E.. Carnegie Institution for Science. Department of Global Ecology; Estados Unidos Fil: Meir, Patrick. University of Edinburgh; Reino Unido. The Australian National University. Research School of Biology. Division of Plant Sciences; Australia Fil: Phillips, Oliver. University of Leeds; Reino Unido Fil: Salinas, Norma. University of Oxford; Reino Unido. Pontificia Universidad Católica de Perú; Perú Fil: Silman, Miles. University Wake Forest; Estados Unidos Fil: Weerasinghe, Lasantha K.. The Australian National University. Research School of Biology. Division of Plant Sciences; Australia Fil: Zaragoza Castells, Joana. The Australian National University. Research School of Biology. Division of Plant Sciences; Australia. University of Exeter; Reino Unido Fil: Malhi, Yadvinder. University of Oxford; Reino Unido

Waxy compounds form the boundary layer of the living leaf and contribute biomarkers to soils, and lake and marine sediments. Cataloging the variation in leaf wax traits between species and across environmental gradients may contribute to the understanding of plant functional processes in modern ecosystems, as well as to calibration efforts supporting reconstruction of past ecosystems and environments from the sedimentary archives of leaf wax biomarkers. Towards these goals, we have surveyed the distributions of leaf wax n-alkanes in trees from the lowland tropical rainforest (TR) and montane cloud forest (TMCF) of Peru. Molecular abundances were quantified via gas chromatography flame ionization detection (GC-FID) for 632 individuals, 152 species, 99 genera and 51 families across 9 forest plots spanning 0.2–3.6 km elevation. We found the expected abundance distributions; for example, they were dominated by long chain, odd numbered n-alkanes, especially C29 and C31. New observations included a tendency to increasing total alkane concentration at higher elevation. We propose that the well known leaf economic strategy to increase leaf mass per unit area with elevation, provides a theoretical basis for understanding the increase in leaf wax n-alkane abundance with elevation: we infer an increased investment in foliar defense associated with increased leaf lifespan and in response to environmental pressures including cloud immersion and declining temperature. Furthermore, we combined measurements of n-alkane concentration with estimates of forest productivity to provide new ways to quantify ecosystem-scale forest alkane productivity. We introduce a new concept of n-alkane net primary productivity (NPPalk; the product of alkane concentration and leaf NPP) and find that alkane productivity estimates range from 300 to 5000 g C/ha/yr, associated with ecological and environmental changes across the elevation profile.

Aim Understanding patterns of species turnover along environmental gradients and their consistency across taxonomic groups is central to the study of biodiversity. We may expect congruence in diversity patterns across groups whose ranges could be influenced by species interactions. We explore associations between bird and vegetation communities in the tropical Andes to determine whether patterns of species richness and turnover in birds and trees are congruent with elevation, and whether tree species composition, vegetation structure, elevation, or a combination of these best predicts bird species composition. Location A forested 2600-m elevational gradient on the eastern slope of the Peruvian Andes. Methods Bird surveys and vegetation measurements were conducted at 172 points, and a subset of these were spatially matched with fourteen 1-ha tree inventory plots. Diversity patterns were described for trees, birds, and avian foraging guilds. We used dissimilarity matrices to examine patterns of turnover and nestedness. Turnover of birds and trees was examined by comparing compositional change of adjacent plots along the gradient. Multiple regression on distance matrices was employed to determine contributions of tree species composition, vegetation structure and elevation to explaining variation in bird species composition. Results Species richness was higher for trees than for birds, and whereas diversity in both taxa decreased with elevation, tree richness showed a low-elevation plateau before declining at higher elevations. Tree species had narrower distributions compared to birds, but patterns of turnover were largely congruent between taxa. Nestedness contributed much less to dissimilarity than turnover, although birds showed higher nestedness, particularly at high elevations. Tree species composition, elevation and vegetation structure were all important predictors of bird species composition; the best model explained 78% of bird dissimilarity across plots. Tree species composition was always included in the best models, for all birds and foraging guilds. Main conclusions Our assessment of Andean bird and vegetation communities suggests strong correspondence, perhaps due to direct interactions or similar underlying drivers. We hypothesize that with climate change, range shifts in these groups may not occur independently. Rather, birds may have delayed upslope shifts or may be limited to high-elevation patches where appropriate vegetation communities exist.

A better understanding of the mechanisms controlling the magnitude and sign of carbon components in tropical forest ecosystems is important for reliable estimation of this important regional component of the global carbon cycle. We used the JULES vegetation model to simulate all components of the carbon balance at six sites along an Andes-Amazon transect across Peru and Brazil and compared the results to published field measurements. In the upper montane zone the model predicted a lack of forest vegetation, indicating a need for better parameterization of the responses of cloud forest vegetation within the model. In the lower montane and lowland zones simulated ecosystem productivity and respiration were predicted with reasonable accuracy, although not always within the error bounds of the observations. Model-predicted carbon use efficiency in this transect surprisingly did not increase with elevation, but remained close to the 'temperate' value 0.5. Upper montane forests were predicted to allocate ~50% of carbon fixation to biomass maintenance and growth, despite available measurements showing that they only allocate ~33%. This may be explained by elevational changes in the balance between growth and maintenance respiration within the forest canopy, as controlled by both temperature- and pressure-mediated processes, which is not yet well represented in current vegetation models. © 2012 Blackwell Publishing Ltd.

Fire in tropical montane cloud forests (TMCFs) is not as rare as once believed. Andean TMCFs sit immediately below highly flammable, high-altitude grasslands (Puna/Paramo) that suffer from recurrent anthropogenic fire. This treeline is a zone of climatic tension where substantial future warming is likely to force upward tree migrations, while increased fire presence and fire impacts are likely to force it downwards. TMCFs contain large carbon stocks in their peat soils and their loss through fire is a currently unaccounted for regional source of CO2. This study, conducted in the southern Peruvian Andes (>2800 m), documents differences in live tree biomass, fine root biomass, fallen and standing dead wood, and soil organic carbon in 4 paired-sample plots (burned versus control) following the severe ground fires that occurred during the 2005 Andean drought. Peat soils contributed the most to biomass burning emissions, with lower values corresponding to an 89% mean stock difference compared to the controls (mean ± SE) (54.1 ± 22.3 vs. 5.8 ± 5.3 MgC ha−1). Contrastingly, carbon stocks from live standing trees differed by a non-significant 37% lower value in the burned plots compared to the controls, largely compensated by vigorous resprouting (45.5 ± 17.4 vs. 69.2 ± 13.4 MgC ha−1). Both standing dead trees and fallen dead wood were significantly higher in the burned plots with a three-fold difference from the controls: dead Trees 45.2 ± 9.4 vs. 16.4 ± 4.4 MgC ha−1, and ca. a 2 fold difference for the fallen dead wood: 11.2 ± 5 vs. 6.7 ± 3.2 MgC ha−1 for the burned plots versus their controls. A preliminary estimate of the regional contribution of biomass burning emissions from Andean TMCFs for the period 2000–2008, resulted in mean carbon emission rates of 1.3 TgC yr−1 (max-min: 1.8–0.8 TgC yr−1). This value is in the same order of magnitude than South American annual fire emissions (300 TgC yr−1) suggesting the need for further research on Andean forest fires. On-going projects on the region are working on the promotion of landowner participation in TMCFs conservation through REDD+ mechanism. The heart of the proposed initiative is reforestation of degraded lands with green fire breaks enriched with economically valuable Andean plant species. The cultivation of these species may contribute to reduce deforestation pressure on the Amazonian cloud forest by providing an alternative income to local communities, at the same time that they prevent the spread of fire into Manu National Park and adjacent community-held forests, protecting forest and reducing CO2 emissions.

Aim Climate change causes shifts in species distributions, or ‘migrations’. Despite the centrality of species distributions to biodiversity conservation, the demonstrated large migration of tropical plant species in response to climate change in the past, and the expected sensitivity of species distributions to modern climate change, no study has tested for modern species migrations in tropical plants. Here we conduct a first test of the hypothesis that increasing temperatures are causing tropical trees to migrate to cooler areas. Location Tropical Andes biodiversity hotspot, south-eastern Peru, South America. Methods We use data from repeated (2003/04–2007/08) censuses of 14 1-ha forest inventory plots spanning an elevational gradient from 950 to 3400 m in Manu National Park in south-eastern Peru, to characterize changes in the elevational distributions of 38 Andean tree genera. We also analyse changes in the genus-level composition of the inventory plots through time. Results We show that most tropical Andean tree genera shifted their mean distributions upslope over the study period and that the mean rate of migration is approximately 2.5–3.5 vertical metres upslope per year. Consistent with upward migrations we also find increasing abundances of tree genera previously distributed at lower elevations in the majority of study plots. Main conclusions These findings are in accord with the a priori hypothesis of upward shifts in species ranges due to elevated temperatures, and are potentially the first documented evidence of present-day climate-driven migrations in a tropical plant community. The observed mean rate of change is less than predicted from the temperature increases for the region, possibly due to the influence of changes in moisture or non-climatic factors such as substrate, species interactions, lags in tree community response and/or dispersal limitations. Whatever the cause(s), continued slower-than-expected migration of tropical Andean trees would indicate a limited ability to respond to increased temperatures, which may lead to increased extinction risks with further climate change.

The net primary productivity, carbon (C) stocks and turnover rates (i.e. C dynamics) of tropical forests are an important aspect of the global C cycle. These variables have been investigated in lowland tropical forests, but they have rarely been studied in tropical montane forests (TMFs). This study examines spatial patterns of above- and belowground C dynamics along a transect ranging from lowland Amazonia to the high Andes in SE Peru. Fine root biomass values increased from 1.50 Mg C ha−1 at 194 m to 4.95 ± 0.62 Mg C ha−1 at 3020 m, reaching a maximum of 6.83 ± 1.13 Mg C ha−1 at the 2020 m elevation site. Aboveground biomass values decreased from 123.50 Mg C ha−1 at 194 m to 47.03 Mg C ha−1 at 3020 m. Mean annual belowground productivity was highest in the most fertile lowland plots (7.40 ± 1.00 Mg C ha−1 yr−1) and ranged between 3.43 ± 0.73 and 1.48 ± 0.40 Mg C ha−1 yr−1 in the premontane and montane plots. Mean annual aboveground productivity was estimated to vary between 9.50 ± 1.08 Mg C ha−1 yr−1 (210 m) and 2.59 ± 0.40 Mg C ha−1 yr−1 (2020 m), with consistently lower values observed in the cloud immersion zone of the montane forest. Fine root C residence time increased from 0.31 years in lowland Amazonia to 3.78 ± 0.81 years at 3020 m and stem C residence time remained constant along the elevational transect, with a mean of 54 ± 4 years. The ratio of fine root biomass to stem biomass increased significantly with increasing elevation, whereas the allocation of net primary productivity above- and belowground remained approximately constant at all elevations. Although net primary productivity declined in the TMF, the partitioning of productivity between the ecosystem subcomponents remained the same in lowland, premontane and montane forests.

Aboveground primary productivity is widely considered to be limited by phosphorus (P) availability in lowland tropical forests and by nitrogen (N) availability in montane tropical forests. However, the extent to which this paradigm applies to belowground processes remains unresolved. We measured indices of soil microbial nutrient status in lowland, sub-montane and montane tropical forests along a natural gradient spanning 3400 m in elevation in the Peruvian Andes. With increasing elevation there were marked increases in soil concentrations of total N, total P, and readily exchangeable P, but a decrease in N mineralization determined by in situ resin bags. Microbial carbon (C) and N increased with increasing elevation, but microbial C : N : P ratios were relatively constant, suggesting homeostasis. The activity of hydrolytic enzymes, which are rich in N, decreased with increasing elevation, while the ratio of enzymes involved in the acquisition of N and P increased with increasing elevation, further indicating an increase in the relative demand for N compared to P with increasing elevation. We conclude that soil microorganisms shift investment in nutrient acquisition from P to N between lowland and montane tropical forests, suggesting that different nutrients regulate soil microbial metabolism and the soil carbon balance in these ecosystems.

Yan-Shih Lin [et al.].- Received 16 August 2014, Accepted 16 January 2015, Published online 02 March 2015, Stomatal conductance (gs) is a key land-surface attribute as it links transpiration, the dominant component of global land evapotranspiration, and photosynthesis, the driving force of the global carbon cycle. Despite the pivotal role of gs in predictions of global water and carbon cycle changes, a global-scale database and an associated globally applicable model of gs that allow predictions of stomatal behaviour are lacking. Here, we present a database of globally distributed gs obtained in the field for a wide range of plant functional types (PFTs) and biomes. We find that stomatal behaviour differs among PFTs according to their marginal carbon cost of water use, as predicted by the theory underpinning the optimal stomatal model1 and the leaf and wood economics spectrum2, 3. We also demonstrate a global relationship with climate. These findings provide a robust theoretical framework for understanding and predicting the behaviour of gs across biomes and across PFTs that can be applied to regional, continental and global-scale modelling of ecosystem productivity, energy balance and ecohydrological processes in a future changing climate.