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Sodium, an element which is needed by animals but often toxic in high concentrations to plants, may be deficient and limit animal abundance in inland continental regions, but may be overabundant and limit plant productivity in coastal regions. Here we present data from 50 independent plots (including leaf data from more than 2480 individual trees) showing that leaves in the Amazon basin uptake high amounts of sodium (Na) in a manner more similar to the essential cation potassium (K) than to the toxic cation aluminium (Al). Leaf Na increases linearly with soil Na concentrations, and there is no apparent mechanism for selective exclusion of Na in comparison to K, a key attribute of halophytes. This indicates that the Amazon basin is broadly non-halophytic and increased sodium concentrations in non-halophyte plants often decrease plant productivity. Total Na concentrations are ∼ 10 times higher in coastal regions than inland regions. Such concentration gradients in nutrients may have been reduced in the past because large animals that were abundant in the Pleistocene have been hypothesized to play a large role in reducing nutrient concentration gradients at continental scales. We use a diffusion model and a Na loss rate based on empirical data to estimate that large animals may have moved significant quantities of Na inland away from coastal regions in the Amazon Basin. Therefore, our simple model suggests that large animals may play an important, yet diminishing, role in maintaining the sodium balance of the planet. [ABSTRACT FROM AUTHOR]

During the Late Pleistocene and early Holocene 59 species of South American megafauna went extinct. Their extinction potentially triggered population declines of large-seeded tree species dispersed by the large-bodied frugivores with which they co-evolved, a theory first proposed by Janzen and Martin (1982). We tested this hypothesis using species range maps for 257 South American tree species, comparing 63 species thought to be primarily distributed by megafauna with 194 distributed by other animals. We found a highly significant (p < 0.001) decreased mean range size of 26% for the megafauna dispersed fruit (n = 63 species) versus fruit dispersed by other animals (n = 194), results which support the hypothesis. We then developed a mathematical model of seed dispersal to estimate the theoretical impact of megafauna extinction on tree species range and found the estimated dispersal capacity (Φseed) of a 2 g seed decreases by > 95% following disperser extinction. A numerical gap dynamic simulations suggests that over a 10 000 yr period following the disperser extinctions, the average convex hull range size of large-seeded tree species decreased by ∼ 31%, while the estimated decrease in population size was ∼ 54%, indicating a likely greater decrease in species population size than indicated by the empirical range patterns. Finally, we found a positive correlation between seed size and wood density of animal-dispersed tree species implying that the Late Pleistocene and early Holocene megafaunal extinctions reduced carbon content in the Amazon by ∼ 1.5 ± 0.7%. In conclusion, we 1) provide some empirical evidence that megafauna distributed fruit species have a smaller mean range size than wind, water or other animal-dispersed species, 2) demonstrate mathematically that such range reductions are expected from megafauna extinctions ca 12 000 yr ago, and 3) illustrate that these extinctions may have reduced the Amazon's carbon storage capacity. [ABSTRACT FROM AUTHOR]

Understanding the complex role of large-bodied mammals in contemporary ecosystems and the likely consequences of their continued decline is essential for effective management of the remaining wild areas on Earth. The very largest animals are in particular peril owing to a disastrous combination of continued hunting or poaching, habitat alterations, and loss of habitat. Because these threats are ongoing, conservation biologists may not be able to wait for the results of long-term studies before proposing potential mitigation strategies. A recent conference on 'Megafauna and ecosystem function: from the Pleistocene to the Anthropocene' at Oxford Univ. brought together paleontologists, conservation and environmental scientists and others who share an interest in characterizing the influence of large animals on ecosystems. Integrating historical perspectives of Late Pleistocene ecosystems when large-bodied animals were still widespread, with modern studies of areas with varying levels of intact megafauna, the aim was to develop a more holistic understanding of the consequences of the ongoing decline of large-bodied animals around the Earth. The conference resulted in the development of two special features - one in the Proceedings of the National Academy of Science, USA and one in Ecography synthesizing the state of our knowledge about the environmental legacies of the terminal Pleistocene megafauna extinction, the complex role of modern large-bodied animals and what the ongoing loss of their ecological interactions might mean in terms of ecosystem function. Here, we briefly review the main themes developed during the conference and outline promising future research directions. [ABSTRACT FROM AUTHOR]

Has land surface cover in South America been impacted by the loss of most large herbivores following the severe Pleistocene and Early Holocene megafauna extinctions on this continent? Here, we estimate how mean savanna woody biomass may have changed in the Americas following these extinctions by creating an empirical model to understand how large herbivores impact savanna woody biomass. To create this empirical model, we combine a large recently published dataset of savanna woody cover from Lehmann et al. (2014) (n = 2154 plots) with estimates of mammals ranges and weights from the IUCN database. We evaluate how variables such as number of megaherbivores (mammal species ≥ 1000 kg), log10 sum species weights, and total number of mammal species predict changes to woody cover by using both ordinary least squares regression analysis (OLS) and simultaneous auto-regressive (SAR) analysis to control for spatial autocorrelation. Both number of megaherbivores and log10 sum species weights, which both disproportionately weight for megaherbivores, significantly explained much (∼ 5-13%) variance in woody cover, but the third variable weighting all animals equally, did not. We then combined these biotic variables with abiotic variables such as temperature, precipitation, and fire frequency to create a model predicting 36% of the variance of savanna woody cover. We used this model combined with estimated range maps of extinct South American megafauna to estimate that had those South American megafauna not gone extinct, total savanna woody cover in South America could possibly have decreased by ∼ 29% and that savannas would likely have been more open like current African savannas. [ABSTRACT FROM AUTHOR]

In 2005 and 2010 the Amazon basin experienced two strong droughts, driven by shifts in the tropical hydrological regime possibly associated with global climate change, as predicted by some global models. Tree mortality increased after the 2005 drought, and regional atmospheric inversion modelling showed basin-wide decreases in CO2 uptake in 2010 compared with 2011 (ref. 5). But the response of tropical forest carbon cycling to these droughts is not fully understood and there has been no detailed multi-site investigation in situ. Here we use several years of data from a network of thirteen 1-ha forest plots spread throughout South America, where each component of net primary production (NPP), autotrophic respiration and heterotrophic respiration is measured separately, to develop a better mechanistic understanding of the impact of the 2010 drought on the Amazon forest. We find that total NPP remained constant throughout the drought. However, towards the end of the drought, autotrophic respiration, especially in roots and stems, declined significantly compared with measurements in 2009 made in the absence of drought, with extended decreases in autotrophic respiration in the three driest plots. In the year after the drought, total NPP remained constant but the allocation of carbon shifted towards canopy NPP and away from fine-root NPP. Both leaf-level and plot-level measurements indicate that severe drought suppresses photosynthesis. Scaling these measurements to the entire Amazon basin with rainfall data, we estimate that drought suppressed Amazon-wide photosynthesis in 2010 by 0.38 petagrams of carbon (0.23-0.53 petagrams of carbon). Overall, we find that during this drought, instead of reducing total NPP, trees prioritized growth by reducing autotrophic respiration that was unrelated to growth. This suggests that trees decrease investment in tissue maintenance and defence, in line with eco-evolutionary theories that trees are competitively disadvantaged in the absence of growth. We propose that weakened maintenance and defence investment may, in turn, cause the increase in post-drought tree mortality observed at our plots. [ABSTRACT FROM AUTHOR]

What determines the seasonal and interannual variation of growth rates in trees in a tropical forest? We explore this question with a novel four-year high-temporal-resolution data set of carbon allocation from two forest plots in the Bolivian Amazon. The forests show strong seasonal variation in tree wood growth rates, which are largely explained by shifts in carbon allocation, and not by shifts in total productivity. At the deeper soil plot, there was a clear seasonal trade-off between wood and canopy NPP, while the shallower soils plot showed a contrasting seasonal trade-off between wood and fine roots. Although a strong 2010 drought reduced photosynthesis, NPP remained constant and increased in the six-month period following the drought, which indicates usage of significant nonstructural carbohydrate stores. Following the drought, carbon allocation increased initially towards the canopy, and then in the following year, allocation increased towards fine-root production. Had we only measured woody growth at these sites and inferred total NPP, we would have misinterpreted both the seasonal and interannual responses. In many tropical forest ecosystems, we propose that changing tree growth rates are more likely to reflect shifts in allocation rather than changes in overall productivity. Only a whole NPP allocation perspective can correctly interpret the relationship between changes in growth and changes in productivity. [ABSTRACT FROM AUTHOR]

Background:Terra preta do indioor ‘dark earth’ soils formed as a result of a long-term addition of organic matter by indigenous peoples in Amazonia. Aims:Here we report on the first study of productivity, allocation and carbon cycling from aterra pretaplot in eastern Amazonia (Caxiuanã, Pará, Brazil), and contrast its dynamics with a nearby plot on infertile soil (ferralsols). Methods:We determined total net primary production (NPP) for fine roots, wood, and canopy and total autotrophic respiration (rhizosphere, wood, and canopy respiration) from two 1-ha plots on contrasting soils. Results:Both gross primary productivity (GPP) (35.68 ± 3.65 vs. 32.08 ± 3.46 Mg C ha−1year−1) and carbon use efficiency (CUE) (0.44 ± 0.06 vs. 0.42 ± 0.05) were slightly higher at theterra pretaplot. Total NPP (15.77 ± 1.13 Mg C ha−1year−1vs. 13.57 ± 0.60 Mg C ha−1year−1) and rates of fine root production (6.41 ± 1.08 vs. 3.68 ± 0.52 Mg C ha−1year−1) were also greater at theterra pretaplot vs. the tower plot. Conclusions:Forests onterra pretasoil fix slightly more carbon and allocate slightly more of that carbon towards growth than forests on the infertile plot, which leads to greater total NPP, which was disproportionately allocated to fine roots. However, since increased fine root NPP was partially offset by increased heterotrophic soil respiration, the increased root growth was unlikely to greatly enhance soil carbon stocks interra pretasoils. [ABSTRACT FROM PUBLISHER]

Background:The dry transitional forests of the southern Amazonia have received little attention from a carbon cycling and ecosystem function perspective, yet they represent ecosystems that may be impacted by global climate change in the future. Aims:To compare the full carbon cycle for two 1-ha forest plots that straddle the ecotone between humid forest and dry forest in Amazonia, ca. 100 km from Santa Cruz, Bolivia. Methods:2.5 years of measurements of the components of net primary production (NPP) and autotrophic respiration were collected. Results:Total NPP was 15.5 ± 0.89 Mg C ha−1year−1at the humid site and 11.27 ± 0.68 Mg C ha−1year−1at the dry site; a total Gross Primary Production (GPP) of 34.14 ± 2.92 Mg C ha−1year−1and 26.88 ± 2.70 Mg C ha−1year−1at the two sites. Carbon use efficiency for both sites was higher than reported for other Amazonian forests (0.45 ± 0.05 and 0.42 ± 0.05). Conclusions:Drier soil conditions selected for the dry deciduous tree species which had higher leaf photosynthesis and total GPP. NPP allocation patterns were similar at the two sites, suggesting that in terms of carbon allocation, the dry forests of the southern Amazonia behave as a scaled-down version of wetter humid forests. [ABSTRACT FROM PUBLISHER]

Background:The forests of north-west Amazonia are characterised by the highest levels of tree diversity in the world, high rainfall and relatively fertile soils. Aims:Here we present a comprehensive description of the carbon cycle of two 1 ha forests plots in Allpahuayo, near Iquitos, Peru, one on an occasionally inundated alisol/gleysol landscape, the other on an arenosol (sandy soil). Methods:Data on the components of net primary productivity (NPP) and autotrophic respiration were collected over the period 2009–2011, and summed to estimate gross primary productivity (GPP) and carbon use efficiency (CUE). Results:Overall, these forests showed high values of GPP (39.05 ± 4.59 and 41.88 ± 4.60 Mg C ha−1year−1). Despite the lack of a dry season, the forests showed distinct seasonality in tree growth, litterfall, flowering and fine root productivity. This showed that tropical forests with little seasonality in water supply can still exhibit distinct seasonality in NPP and carbon use, apparently synchronised to the solar radiation cycle. We found remarkably little difference in productivity between the alisol/gleysol plot and the arenosol plot. Conclusions:The GPP was higher than those reported for forests in Brazilian Amazonia on more infertile soils. The CUE was also higher, which may be related to the high forest dynamism and natural disturbance rate. These two factors combined to result in amongst the highest NPP values reported for Amazonia. [ABSTRACT FROM PUBLISHER]

Background:Tropical montane cloud forests (TMCF) are unique ecosystems with high biodiversity and large carbon reservoirs. To date there have been limited descriptions of the carbon cycle of TMCF. Aims:We present results on the production, allocation and cycling of carbon for two mid-elevation (1500–1750 m) tropical montane cloud forest plots in San Pedro, Kosñipata Valley, Peru. Methods:We repeatedly recorded the components of net primary productivity (NPP) using biometric measurements, and autotrophic (Ra) and heterotrophic (Rh) respiration, using gas exchange measurements. From these we estimated gross primary productivity (GPP) and carbon use efficiency (CUE) at the plot level. Results:The plot at 1500 m was found very productive, with our results comparable with the most productive lowland Amazonian forests. The plot at 1750 m had significantly lower productivity, possibly because of greater cloud immersion. Both plots had similar patterns ofNPPallocation, a substantial seasonality inNPPcomponents and little seasonality inRa. Conclusions:These two plots lie within the ecotone between lower and upper montane forests, near the level of the cloud base. Climate change is likely to increase elevation of the cloud base, resulting in shifts in forest functioning. Longer-term surveillance of the carbon cycle at these sites would yield valuable insights into the response of TMCFs to a shifting cloud base. [ABSTRACT FROM PUBLISHER]

Background:The forests of western Amazonia are known to be more dynamic that the better-studied forests of eastern Amazonia, but there has been no comprehensive description of the carbon cycle of a western Amazonian forest. Aims:We present the carbon budget of two forest plots in Tambopata in south-eastern Peru, western Amazonia. In particular, we present, for the first time, the seasonal variation in the detailed carbon budget of a tropical forest. Methods:We measured the major components of net primary production (NPP) and total autotrophic respiration over 3–6 years. Results:The NPP for the two plots was 15.1 ± 0.8 and 14.2 ± 1.0 Mg C ha−1year−1, the gross primary productivity (GPP) was 35.5 ± 3.6 and 34.5 ± 3.5 Mg C ha−1year−1, and the carbon use efficiency (CUE) was 0.42 ± 0.05 and 0.41 ± 0.05. NPP and CUE showed a large degree of seasonality. Conclusions:The two plots were similar in carbon cycling characteristics despite the different soils, the most notable difference being high allocation of NPP to canopy and low allocation to fine roots in the Holocene floodplain plot. The timing of the minima in the wet–dry transition suggests they are driven by phenological rhythms rather than being driven directly by water stress. When compared with results from forests on infertile forests in humid lowland eastern Amazonia, the plots have slightly higher GPP, but similar patterns of CUE and carbon allocation. [ABSTRACT FROM PUBLISHER]

Background:The slopes of the eastern Andes harbour some of the highest biodiversity on Earth and a high proportion of endemic species. However, there have been only a few and limited descriptions of carbon budgets in tropical montane forest regions. Aims:We present the first comprehensive data on the production, allocation and cycling of carbon for two high elevation (ca. 3000 m) tropical montane cloud forest plots in the Kosñipata Valley, Peruvian Andes. Methods:We measured the main components and seasonal variation of net primary productivity (NPP), autotrophic (Ra) and heterotrophic (Rh) respiration to estimate gross primary productivity (GPP) and carbon use efficiency (CUE) in two 1-ha plots. Results:NPPfor the two plots was estimated to be 7.05 ± 0.39 and 8.04 ± 0.47 Mg C ha−1year−1,GPPto be 22.33 ± 2.23 and 26.82 ± 2.97 Mg C ha−1year−1andCUEwas 0.32 ± 0.04 and 0.30 ± 0.04. Conclusions:We found strong seasonality inNPPand moderate seasonality ofRa, suggesting that forestNPPis driven by changes in photosynthesis and highlighting the importance of variation in solar radiation. Our findings imply that trees invest more in biomass production in the cooler season with lower solar radiation and more in maintenance during the warmer and high solar radiation period. [ABSTRACT FROM PUBLISHER]

Background: Dysphagia is a major complication of stroke, but factors influencing its recovery are incompletely understood. The goal of this study was to identify important prognostic variables affecting swallowing recovery after acute ischemic stroke. Methods: We retrospectively reviewed our patient database to identify acute ischemic stroke patients who developed dysphagia after stroke but were free of other confounding conditions affecting swallowing. Of the 1774 patients screened, 323 met the study criteria. We assessed the effect of age, sex, baseline National Institutes of Health Stroke Scale (NIHSS) score, level of consciousness (LOC), facial weakness, dysarthria, neglect, bihemispheric infarcts, right hemispheric infarcts, brainstem infarcts, intubation, aspiration, acute stroke therapies, occurrence of symptomatic hemorrhagic transformation, seizures, pneumonia, and length of hospitalization (LOH) on persistence of dysphagia at hospital discharge in a logistic regression analysis. Results: The mean age and NIHSS scores (mean ± standard deviation) were 75.9 ± 13.6 years and 13.5 ± 6.9, respectively; 58.5% were women. In a multivariate analysis, aspiration detected on a clinical swallowing evaluation (odds ratio [OR] 21.83; 95% confidence interval [CI] 8.16-58.42; P < .0001), aspiration on videofluoroscopic swallowing study (OR 10.50; 95% CI 3.35-32.96; P < .0001), bihemispheric infarcts (OR 3.72; 95% CI 1.33-10.43; P = .0123), dysarthria (OR 3.4; 95% CI 1.57-7.35; P = .0019), intubation (OR 2.86; 95% CI 1.10-7.39; P = .0301), NIHSS score ≥12 (OR 2.51; 95% CI 1.19-5.23; P = .0157) were significant predictors of persistent dysphagia. The area under the curve and Somer's D xy statistics of the model were 0.8918 and 0.78, respectively, indicating good calibration and discriminative power. Conclusions: Prognostic factors affecting swallowing recovery identified in this study can help advance dysphagia research methodologies and the clinical care of stroke patients. [Copyright &y& Elsevier]

Forest dynamics and tree species composition vary substantially between Paleotropical and Neotropical forests, but these broad biogeographic regions are treated uniformly in many land models. To assess whether these regional differences translate into variation in productivity and carbon (C) storage, we compiled a database of climate, tree stem growth, litterfall, aboveground net primary production (ANPP), and aboveground biomass across tropical rainforest sites spanning 33 countries throughout Central and South America, Asia, and Australasia, but excluding Africa due to a paucity of available data. Though the sum of litterfall and stem growth (ANPP) did not differ between regions, both stem growth and the ratio of stem growth to litterfall were higher in Paleotropical forests compared to Neotropical forests across the full observed range of ANPP. Greater C allocation to woody growth likely explains the much larger aboveground biomass estimates in Paleotropical forests (~29%, or ~80 Mg DW/ha, greater than in the Neotropics). Climate was similar in Paleo‐ and Neotropical forests, thus the observed differences in C likely reflect differences in the evolutionary history of species and forest structure and function between regions. Our analysis suggests that Paleotropical forests, which can be dominated by tall‐statured Dipterocarpaceae species, may be disproportionate hotspots for aboveground C storage. Land models typically treat these distinct tropical forests with differential structures as a single functional unit, but our findings suggest that this may overlook critical biogeographic variation in C storage potential among regions. [ABSTRACT FROM AUTHOR]

Peripheral neuropathy is commonly encountered in the primary care setting and is associated with significant morbidity, including neuropathic pain, falls, and disability. The clinical presentation of neuropathy is diverse, with possible symptoms including weakness, sensory abnormalities, and autonomic dysfunction. Accordingly, the primary care clinician must be comfortable using the neurologic examination-including the assessment of motor function, multiple sensory modalities, and deep tendon reflexes-to recognize and characterize neuropathy. Although the causes of peripheral neuropathy are numerous and diverse, careful review of the medical and family history coupled with limited, select laboratory testing can often efficiently lead to an etiologic diagnosis. This review offers an approach for evaluating suspected neuropathy in the primary care setting. It will describe the most common causes, suggest an evidence-based workup to aid in diagnosis, and highlight recent evidence that allows for selection of symptomatic treatment of patients with neuropathy. [ABSTRACT FROM AUTHOR]

Summary: Populus fremontii is among the most dominant, and ecologically important riparian tree species in the western United States and can thrive in hyper‐arid riparian corridors. Yet, P. fremontii forests have rapidly declined over the last decade, particularly in places where temperatures sometimes exceed 50°C.We evaluated high temperature tolerance of leaf metabolism, leaf thermoregulation, and leaf hydraulic function in eight P. fremontii populations spanning a 5.3°C mean annual temperature gradient in a well‐watered common garden, and at source locations throughout the lower Colorado River Basin.Two major results emerged. First, despite having an exceptionally high Tcrit (the temperature at which Photosystem II is disrupted) relative to other tree taxa, recent heat waves exceeded Tcrit, requiring evaporative leaf cooling to maintain leaf‐to‐air thermal safety margins. Second, in midsummer, genotypes from the warmest locations maintained lower midday leaf temperatures, a higher midday stomatal conductance, and maintained turgor pressure at lower water potentials than genotypes from more temperate locations.Taken together, results suggest that under well‐watered conditions, P. fremontii can regulate leaf temperature below Tcrit along the warm edge of its distribution. Nevertheless, reduced Colorado River flows threaten to lower water tables below levels needed for evaporative cooling during episodic heat waves. [ABSTRACT FROM AUTHOR]

Ecological restoration is critical for climate and biodiversity resilience over the coming century. Today, there is strong evidence that wildlife can significantly influence the distribution and stoichiometry of elements across landscapes, with subsequent impacts on the composition and functioning of ecosystems. Consequently, any anthropogenic activity that modifies this important aspect of zoogeochemistry, such as changes to animal community composition, diet, or movement patterns, may support or hinder restoration goals. It is therefore imperative that the zoogeochemical effects of such anthropogenic modifications are quantified and mapped at high spatiotemporal resolutions to help inform restoration strategies. Here, we first discuss pathways through which human activities shape wildlife‐mediated elemental landscapes and outline why current frameworks are inadequate to characterize these processes. We then suggest improvements required to comprehensively model, validate, and monitor element recycling and redistribution by wildlife under differing wildlife management scenarios and discuss how this might be implemented in practice through a specific example in the southern Kalahari Desert. With robust ecological forecasting, zoogeochemical impacts of wildlife can thus be used to support ecological restoration and nature‐based solutions to climate change. If ignored in the restoration process, the effects of wildlife on elemental landscapes may delay, or even prevent, restoration success. [ABSTRACT FROM AUTHOR]

Meteorological extreme events such as El Niño events are expected to affect tropical forest net primary production (NPP) and woody growth, but there has been no large-scale empirical validation of this expectation. We collected a large high--temporal resolution dataset (for 1-13 years depending upon location) of more than 172 000 stem growth measurements using dendrometer bands from across 14 regions spanning Amazonia, Africa and Borneo in order to test how much month-to-month variation in stand-level woody growth of adult tree stems (NPPstem) can be explained by seasonal variation and interannual meteorological anomalies. A key finding is that woody growth responds differently to meteorological variation between tropical forests with a dry season (where monthly rainfall is less than 100 mm), and aseasonal wet forests lacking a consistent dry season. In seasonal tropical forests, a high degree of variation in woody growth can be predicted from seasonal variation in temperature, vapour pressure deficit, in addition to anomalies of soil water deficit and shortwave radiation. The variation of aseasonal wet forest woody growth is best predicted by the anomalies of vapour pressure deficit, water deficit and shortwave radiation. In total, we predict the total live woody production of the global tropical forest biome to be 2.16 Pg C yr-1, with an interannual range 1.96-2.26 Pg C yr-1 between 1996-2016, and with the sharpest declines during the strong El Niño events of 1997/8 and 2015/6. There is high geographical variation in hotspots of El Niño--associated impacts, with weak impacts in Africa, and strongly negative impacts in parts of Southeast Asia and extensive regions across central and eastern Amazonia. Overall, there is high correlation (r = 20.75) between the annual anomaly of tropical forest woody growth and the annual mean of the El Niño 3.4 index, driven mainly by strong correlations with anomalies of soil water deficit, vapour pressure deficit and shortwave radiation. This article is part of the discussion meeting issue 'The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications'. [ABSTRACT FROM AUTHOR]

In nutrient-poor wildlife reserves it has become common-practice to provide supplemental mineral resources for wildlife. Yet, the impacts of anthropogenic mineral supplementation on large herbivore nutrition, behaviour, and subsequent impact on ecosystem processes have received little attention. Here, we examine the contribution of anthropogenic mineral lick provision to wildlife nutrient intake across a community of mammalian herbivores (>10 kg) in the southern Kalahari Desert. Based on predicted daily nutrient intake and a faecal nutrient assessment, many large herbivore species appear deficient in phosphorus (P), sodium (Na), or zinc (Zn). For these nutrients, anthropogenic salt and mineral licks constitute an important source of nutrient intake helping to reduce or overcome requirement deficits. Larger-bodied species disproportionately consumed licks, acquiring more nutritional benefits. A comprehensive assessment of animal body condition indicated that, in general, large herbivores display good health. However, bulk grazers, non-ruminants and females displayed poorer body condition. We discuss how provisioning of anthropogenic mineral licks may inflate large herbivore populations beyond the long-term carrying capacity of the reserve by decoupling wildlife fecundity from nutrient-related feedbacks on population growth. Over time, this could compromise ecosystem integrity through habitat degradation, modified species interactions and trophic cascades. Based on results presented here, it is clear that anthropogenic provisioning of mineral licks should be considered cautiously by wildlife managers aiming to conserve natural processes in landscapes. [Display omitted] • Mineral licks are commonly used by wildlife managers. • Impacts of licks on large herbivore nutrition and behaviour is poorly understood. • Larger-bodied species disproportionately consume licks, acquiring benefits. • Anthropogenic licks may inflate herbivore populations beyond carrying capacity. • Wildlife managers should cautiously consider provision of mineral licks. [ABSTRACT FROM AUTHOR]

Abstract: It is known that tropical grasslands such as Serengeti host large populations of arbuscular mycorrhizal (AM) fungi and that they respond to abiotic and biotic factors. It is also known that AM symbioses are important for the uptake of essential plant nutrients, which, in turn, influences the biomass and nutritional quality of herbivores and their predators. The purpose of this study was to investigate the influence of AM symbioses on the biomass of different trophic levels of an ecosystem. To do this, we first measured the neutral lipid fatty acid biomarker 16:1ω5 to estimate the biomass of AM fungi in a long‐term grazing exclusion experiment. Then, we used model selection of Bayesian linear regressions to infer the primary factors that influence AM fungal biomass. Using model selection of different combinations of soil characteristics, we selected the best model using the leave‐one‐out cross‐validation information criterion. Finally, we used the Madingley model to simulate the influence of AM fungi on higher trophic levels. We combined spatially explicit information about soil phosphorus and AM fungal biomass to explore the emergent patterns of the Serengeti resulting from AM symbioses. Our Bayesian analysis indicated that total soil phosphorus was the strongest predictor of AM fungal biomass, and there were significant interactions with grazing. Arbuscular mycorrhizal fungal biomass is lowest in soil where phosphorus is limited and increases with increasing phosphorus concentration. Biomass was also significantly higher in plots that were not grazed. The Madingley model indicated that nutritional benefits of AM symbioses maintain a substantial proportion of the biomass across all trophic levels. Synthesis. Our analysis shows that inputs of phosphorus through arbuscular mycorrhizal symbioses substantially increase the ability of plants to grow and maintain nutritional quality, cascading through the biomass of consumers and predators in the ecosystem. Although they account for less than 1% of the total modelled biomass, the predicted nutritional benefit provided by arbuscular mycorrhizal fungi increased the biomass of macro‐organisms in the Serengeti by 48%. When considering the management of biodiversity, future ecosystem models should account for the influence of arbuscular mycorrhizal fungi on all trophic levels. [ABSTRACT FROM AUTHOR]

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