A global growth-form database for 143,616 vascular plant species

For the majority of plant species in the world, we know little about their functional ecology, and not even one of the most basic traits-the species' growth habit. To fill the gap in availability of compiled plant growth-form data, we have assembled what is, to our knowledge, the largest global database on growth-form as a plant trait. We have, with extensive error checking and data synthesis, assembled a growth-form database from 163 data sources for 143,616 vascular plant species from 445 different plant families. This is 38.6% of the currently accepted vascular plant diversity. For our database, we have chosen seven categories to cover the majority of the diversity in plant growth forms: aquatic plants, epiphytes, hemiepiphytes, climbing plants, parasitic plants, holo-mycoheterotrophs, and freestanding plants. These categories were used because we were able to reconcile the wealth of existing definitions and types of growth-form information available globally to them clearly and unequivocally, and because they are complementary with existing databases. Plants in the database were designated into a category if their adult growth form fit the criterion. We make available two databases: first, the complete data set, including species for which there is currently conflicting information, and second, a consensus data set, where all available information supports one categorization. Of the plant species for which we found information, 103,138 (72%) are freestanding, 21,110 (15%) are epiphytes, and 4,046 (3%) are parasites. Our growth-form data can be used to produce useful summary statistics by clade. For example, current data suggests that half of pteridophytes are epiphytic, that all hemiepiphytes are eudicots, and that there are no parasitic monocots, gymnosperms, or pteridophytes. Growth form is a crucial piece of fundamental plant-trait data with implications for each species' ecology, evolution, and conservation, and thus this data set will be useful for a range of basic and applied questions across these areas of research. No copyright or proprietary restrictions are associated with the use of this data set, other than citation of the present Data Paper. A static version of this dataset is provided as Supporting Information, and a living and updating version of the dataset is available in a GitHub repository.

Lower body negative pressure to safely reduce intracranial pressure

KEY POINTS

During long-term missions, some astronauts experience structural and functional changes of the eyes and brain which resemble signs/symptoms experienced by patients with intracranial hypertension. Weightlessness prevents the normal cerebral volume and pressure 'unloading' associated with upright postures on Earth, which may be part of the cerebral and ocular pathophysiology. By placing the lower body in a negative pressure device (LBNP) that pulls fluid away from cranial compartments, we simulated effects of gravity and significantly lowered pressure within the brain parenchyma and ventricle compartments. Application of incremental LBNP demonstrated a non-linear dose-response curve, suggesting 20 mmHg LBNP as the optimal level for reducing pressure in the brain without impairing cerebral perfusion pressure. This non-invasive method of reducing pressure in the brain holds potential as a countermeasure in space as well as having treatment potential for patients on Earth with traumatic brain injury or other pathology leading to intracranial hypertension.

ABSTRACT

Patients with elevated intracranial pressure (ICP) exhibit neuro-ocular symptoms including headache, papilloedema and loss of vision. Some of these symptoms are also present in astronauts during and after prolonged space-flight where lack of gravitational stress prevents daily lowering of ICP associated with upright posture. Lower body negative pressure (LBNP) simulates the effects of gravity by displacing fluid caudally and we hypothesized that LBNP would lower ICP without compromising cerebral perfusion. Ten cerebrally intact volunteers were included: six ambulatory neurosurgical patients with parenchymal ICP-sensors and four former cancer patients with Ommaya-reservoirs to the frontal horn of a lateral ventricle. We applied LBNP while recording ICP and blood pressure while supine, and during simulated intracranial hypertension by 15° head-down tilt. LBNP from 0 to 50 mmHg at increments of 10 mmHg lowered ICP in a non-linear dose-dependent fashion; when supine (n = 10), ICP was decreased from 15 ± 2 mmHg to 14 ± 4, 12 ± 5, 11 ± 4, 10 ± 3 and 9 ± 4 mmHg, respectively (P < 0.0001). Cerebral perfusion pressure (CPP), calculated as mean arterial blood pressure at midbrain level minus ICP, was unchanged (from 70 ± 12 mmHg to 67 ± 9, 69 ± 10, 70 ± 12, 72 ± 13 and 74 ± 15 mmHg; P = 0.02). A 15° head-down tilt (n = 6) increased ICP to 26 ± 4 mmHg, while application of LBNP lowered ICP (to 21 ± 4, 20 ± 4, 18 ± 4, 17 ± 4 and 17 ± 4 mmHg; P < 0.0001) and increased CPP (P < 0.01). An LBNP of 20 mmHg may be the optimal level to lower ICP without impairing CPP to counteract spaceflight-associated neuro-ocular syndrome in astronauts. Furthermore, LBNP holds clinical potential as a safe, non-invasive method for lowering ICP and improving CPP for patients with pathologically elevated ICP on Earth.

Plant functional trait change across a warming tundra biome

The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature-trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming.

Functional biogeography of angiosperms: life at the extremes

Nonlinear relationships between species and their environments are believed common in ecology and evolution, including during angiosperms' rise to dominance. Early angiosperms are thought of as woody evergreens restricted to warm, wet habitats. They have since expanded into numerous cold and dry places. This expansion may have included transitions across important environmental thresholds. To understand linear and nonlinear relationships between angiosperm structure and biogeographic distributions, we integrated large datasets of growth habits, conduit sizes, leaf phenologies, evolutionary histories, and environmental limits. We consider current-day patterns and develop a new evolutionary model to investigate processes that created them. The macroecological pattern was clear: herbs had lower minimum temperature and precipitation limits. In woody species, conduit sizes were smaller in evergreens and related to species' minimum temperatures. Across evolutionary timescales, our new modeling approach found conduit sizes in deciduous species decreased linearly with minimum temperature limits. By contrast, evergreen species had a sigmoidal relationship with minimum temperature limits and an inflection overlapping freezing. These results suggest freezing represented an important threshold for evergreen but not deciduous woody angiosperms. Global success of angiosperms appears tied to a small set of alternative solutions when faced with a novel environmental threshold.

Living Without a Pulse: The Vascular Implications of Continuous-Flow Left Ventricular Assist Devices

Pulsatility seems to have a teleological role because evolutionary hierarchy favors higher ordered animals with more complex, multichamber circulatory systems that generate higher pulse pressure compared with lower ordered animals. Yet despite years of such natural selection, the modern generation of continuous-flow left ventricular assist devices (CF-LVADs) that have been increasingly used for the last decade have created a unique physiology characterized by a nonpulsatile, nonlaminar blood flow profile with the absence of the usual large elastic artery Windkessel effect during diastole. Although outcomes and durability have improved with CF-LVADs, patients supported with CF-LVADs have a high rate of complications that were not as frequently observed with older pulsatile devices, including gastrointestinal bleeding from arteriovenous malformations, pump thrombosis, and stroke. Given the apparent fundamental biological role of the pulse, the purpose of this review is to describe the normal physiology of ventricular-arterial coupling from pulsatile flow, the effects of heart failure on this physiology and the vasculature, and to examine the effects of nonpulsatile blood flow on the vascular system and potential role in complications seen with CF-LVAD therapy. Understanding these concomitant vascular changes with CF-LVADs may be a key step in improving patient outcomes as modulation of pulsatility and flow characteristics may serve as a novel, yet simple, therapy for reducing complications.

Fluid structure interaction model analysis of cerebrospinal fluid circulation in patients with continuous-flow left ventricular assist devices

PURPOSE

The current 1-dimensional fluid structure interaction model (FSI) for understanding cerebrospinal fluid (CSF) circulation requires pulsatility as a precondition and has not been applied to patients with continuous-flow left ventricular assist devices (CF-LVAD) where pulsatility is chronically reduced. Our study aims to characterize the behavior of CSF pressure and flow in patients with CF-LVADs using a computational FSI model.

METHODS

Utilizing the computational FSI model, CSF production in choroid plexuses of the 4 ventricles was specified as a boundary condition for the model. The other source of production from capillary ultrafiltrate spaces was accounted for by the mass conservation equation. The primary CSF absorption sites (i.e., arachnoid granulations) were treated as the outlet boundary conditions. We established a low pulse wave to represent patients with a CF-LVAD.

RESULTS

From the model, low pulse conditions resulted in a reduction in CSF pressure amplitude and velocity though the overall flow rate was unchanged.

CONCLUSIONS

The existing FSI model is not a suitable representation of CSF flow in CF-LVAD patients. More studies are needed to elucidate the role of pulsatility in CSF flow and the compensatory changes in CSF production and absorption that occur in patients with CF-LVADs in whom pulsatility is diminished.

Are litter decomposition and fire linked through plant species traits?

Contents 653 I. 654 II. 657 III. 659 IV. 661 V. 662 VI. 663 VII. 665 665 References 665 SUMMARY: Biological decomposition and wildfire are connected carbon release pathways for dead plant material: slower litter decomposition leads to fuel accumulation. Are decomposition and surface fires also connected through plant community composition, via the species' traits? Our central concept involves two axes of trait variation related to decomposition and fire. The 'plant economics spectrum' (PES) links biochemistry traits to the litter decomposability of different fine organs. The 'size and shape spectrum' (SSS) includes litter particle size and shape and their consequent effect on fuel bed structure, ventilation and flammability. Our literature synthesis revealed that PES-driven decomposability is largely decoupled from predominantly SSS-driven surface litter flammability across species; this finding needs empirical testing in various environmental settings. Under certain conditions, carbon release will be dominated by decomposition, while under other conditions litter fuel will accumulate and fire may dominate carbon release. Ecosystem-level feedbacks between decomposition and fire, for example via litter amounts, litter decomposition stage, community-level biotic interactions and altered environment, will influence the trait-driven effects on decomposition and fire. Yet, our conceptual framework, explicitly comparing the effects of two plant trait spectra on litter decomposition vs fire, provides a promising new research direction for better understanding and predicting Earth surface carbon dynamics.

Volume loading augments cutaneous vasodilatation and cardiac output of heat stressed older adults

KEY POINTS

Age-related changes in cutaneous microvascular and cardiac functions limit the extent of cutaneous vasodilatation and the increase in cardiac output that healthy older adults can achieve during passive heat stress. However, it is unclear if these age-related changes in microvascular and cardiac functions maximally restrain the levels of cutaneous vasodilatation and cardiac output that healthy older adults can achieve during heat stress. We observed that rapid volume loading, performed during passive heat stress, augments both cutaneous vasodilatation and cardiac output in healthy older humans. These findings demonstrate that the microcirculation of healthy aged skin can further dilate during passive heat exposure, despite peripheral limitations to vasodilatation. Furthermore, healthy older humans can augment cardiac output when cardiac pre-load is increased during heat stress.

ABSTRACT

Primary ageing markedly attenuates cutaneous vasodilatation and the increase in cardiac output during passive heating. However, it remains unclear if these responses are maximally restrained by age-related changes in cutaneous microvascular and cardiac functions. We hypothesized that rapid volume loading performed during heat stress would increase cardiac output in older adults without parallel increases in cutaneous vasodilatation. Twelve young (Y: 26 ± 5 years) and ten older (O: 69 ± 3 years) healthy adults were passively heated until core temperature increased by 1.5°C. Cardiac output (thermodilution), forearm vascular conductance (FVC, venous occlusion plethysmography) and cutaneous vascular conductance (CVC, laser-Doppler) were measured before and after rapid infusion of warmed saline (15 mL kg^-1 , ∼7 min). While heat stressed, but prior to saline infusion, cardiac output (O: 6.8 ± 0.4 vs. Y: 9.4 ± 0.6 L min^-1 ), FVC (O: 0.08 ± 0.01 vs. Y: 0.17 ± 0.02 mL (100 mL min^-1  mmHg^-1 )^-1 ), and CVC (O: 1.29 ± 0.34 vs. Y: 1.93 ± 0.30 units mmHg^-1 ) were lower in older adults (all P < 0.01). Rapid saline infusion increased cardiac output (O: +1.9 ± 0.3, Y: +1.8 ± 0.7 L min^-1 ), FVC (O: +0.015 ± 0.007, Y: +0.048 ± 0.013 mL (100 mL min^-1  mmHg^-1 )^-1 ), and CVC (O: +0.28 ± 0.10, Y: +0.29 ± 0.16 units mmHg^-1 ) in both groups (all P < 0.01). The absolute increase in cardiac output and CVC were similar between groups, whereas FVC increased to a greater extent in young adults (P < 0.01). These results demonstrate that healthy older adults can achieve greater levels of cutaneous vasodilatation and cardiac output during passive heating.

Towards a universal model for carbon dioxide uptake by plants

Gross primary production (GPP)-the uptake of carbon dioxide (CO₂) by leaves, and its conversion to sugars by photosynthesis-is the basis for life on land. Earth System Models (ESMs) incorporating the interactions of land ecosystems and climate are used to predict the future of the terrestrial sink for anthropogenic CO₂¹ . ESMs require accurate representation of GPP. However, current ESMs disagree on how GPP responds to environmental variations ^1,2 , suggesting a need for a more robust theoretical framework for modelling ^3,4 . Here, we focus on a key quantity for GPP, the ratio of leaf internal to external CO₂ (χ). χ is tightly regulated and depends on environmental conditions, but is represented empirically and incompletely in today's models. We show that a simple evolutionary optimality hypothesis ^5,6 predicts specific quantitative dependencies of χ on temperature, vapour pressure deficit and elevation; and that these same dependencies emerge from an independent analysis of empirical χ values, derived from a worldwide dataset of >3,500 leaf stable carbon isotope measurements. A single global equation embodying these relationships then unifies the empirical light-use efficiency model ⁷ with the standard model of C₃ photosynthesis ⁸ , and successfully predicts GPP measured at eddy-covariance flux sites. This success is notable given the equation's simplicity and broad applicability across biomes and plant functional types. It provides a theoretical underpinning for the analysis of plant functional coordination across species and emergent properties of ecosystems, and a potential basis for the reformulation of the controls of GPP in next-generation ESMs.

Dynamic Changes in Aortic Vascular Stiffness in Patients Bridged to Transplant With Continuous-Flow Left Ventricular Assist Devices

OBJECTIVES

The aim of this study was to measure aortic vascular stiffness from orthotopic heart transplant (OHT) patients exposed to varying types of flow as a result of the presence or absence of left ventricular assist device (LVAD) support pre-OHT.

BACKGROUND

The effects of continuous-flow LVADs (CF-LVADs) on vascular properties are unknown, but may contribute to the pathophysiology of CF-LVAD complications such as stroke, hypertension, and bleeding.

METHODS

Echocardiograms were reviewed from 172 OHT patients immediately before LVAD and at 3 time points post-OHT: baseline, 6 months, and 1 year. For each study, pulse pressure and aortic end-systolic and end-diastolic dimensions were used to calculate aortic strain, distensibility, and stiffness index. Patients were categorized into 3 groups based on the presence or absence of a LVAD and a pulse pre-OHT: No LVAD (n = 111), LVAD No Pulse (n = 30), and LVAD With Pulse (n = 31).

RESULTS

The aortic stiffness index among LVAD No Pulse patients increased from 2.8 ± 1.1 pre-CF-LVAD to 10.9 ± 4.7 immediately post-OHT (p < 0.001). This aortic stiffness index was also significantly higher compared with No LVAD (3.4 ± 1.1; p < 0.001) and LVAD With Pulse (3.7 ± 1.4; p < 0.001) immediately post-OHT with attenuation of these differences by 1 year post-OHT. Similar findings were noted for the other indices of aortic stiffness.

CONCLUSIONS

Aortic stiffness is markedly increased immediately post-OHT among patients bridged with CF-LVADs, with attenuation of this increased stiffness over the first year after transplant. These results suggest that aortic vascular properties are dynamic and may be influenced by alterations in flow pulsatility. As more patients are supported with CF-LVADs and as newer pump technology attempts to modulate pulsatility, further research examining the role of alterations in flow patterns on vascular function and the potential resultant systemic sequelae are needed.

Effect of gravity and microgravity on intracranial pressure

KEY POINTS

Astronauts have recently been discovered to have impaired vision, with a presentation that resembles syndromes of elevated intracranial pressure on Earth. Gravity has a profound effect on fluid distribution and pressure within the human circulation. In contrast to prevailing theory, we observed that microgravity reduces central venous and intracranial pressure. This being said, intracranial pressure is not reduced to the levels observed in the 90 deg seated upright posture on Earth. Thus, over 24 h in zero gravity, pressure in the brain is slightly above that observed on Earth, which may explain remodelling of the eye in astronauts.

ABSTRACT

Astronauts have recently been discovered to have impaired vision, with a presentation that resembles syndromes of elevated intracranial pressure (ICP). This syndrome is considered the most mission-critical medical problem identified in the past decade of manned spaceflight. We recruited five men and three women who had an Ommaya reservoir inserted for the delivery of prophylactic CNS chemotherapy, but were free of their malignant disease for at least 1 year. ICP was assessed by placing a fluid-filled 25 gauge butterfly needle into the Ommaya reservoir. Subjects were studied in the upright and supine position, during acute zero gravity (parabolic flight) and prolonged simulated microgravity (6 deg head-down tilt bedrest). ICP was lower when seated in the 90 deg upright posture compared to lying supine (seated, 4 ± 1 vs. supine, 15 ± 2 mmHg). Whilst lying in the supine posture, central venous pressure (supine, 7 ± 3 vs. microgravity, 4 ± 2 mmHg) and ICP (supine, 17 ± 2 vs. microgravity, 13 ± 2 mmHg) were reduced in acute zero gravity, although not to the levels observed in the 90 deg seated upright posture on Earth. Prolonged periods of simulated microgravity did not cause progressive elevations in ICP (supine, 15 ± 2 vs. 24 h head-down tilt, 15 ± 4 mmHg). Complete removal of gravity does not pathologically elevate ICP but does prevent the normal lowering of ICP when upright. These findings suggest the human brain is protected by the daily circadian cycles in regional ICPs, without which pathology may occur.

Species mixture effects on flammability across plant phylogeny: the importance of litter particle size and the special role for non-Pinus Pinaceae

Fire affects and is affected by plants. Vegetation varies in flammability, that is, its general ability to burn, at different levels of ecological organization. To scale from individual plant traits to community flammability states, understanding trait effects on species flammability variation and their interaction is important. Plant traits are the cumulative result of evolution and they show, to differing extents, phylogenetic conservatism. We asked whether phylogenetic distance between species predicts species mixture effects on litterbed flammability. We conducted controlled laboratory burns for 34 phylogenetically wide-ranging species and 34 random two-species mixtures from them. Generally, phylogenetic distance did not predict species mixture effects on flammability. Across the plant phylogeny, most species were flammable except those in the non-Pinus Pinaceae, which shed small needles producing dense, poorly ventilated litterbeds above the packing threshold and therefore nonflammable. Consistently, either positive or negative dominance effects on flammability of certain flammable or those non-flammable species were found in mixtures involving the non-Pinus Pinaceae. We demonstrate litter particle size is key to explaining species nonadditivity in fuelbed flammability. The potential of certain species to influence fire disproportionately to their abundance might increase the positive feedback effects of plant flammability on community flammability state if flammable species are favored by fire.

Healthy aging does not compromise the augmentation of cardiac function during heat stress

During heat stress, stroke volume is maintained in young adults despite reductions in cardiac filling pressures. This is achieved by a general augmentation of cardiac function, highlighted by a left and upward shift of the Frank-Starling relation. In contrast, healthy aged adults are unable to maintain stroke volume during heat stress. We hypothesized that this would be associated with a lack of shift in the Frank-Starling relation. Frank-Starling relations were examined in 11 aged [69 ± 4 (SD) yr, 4 men/7 women] and 12 young (26 ± 5 yr, 6 men/6 women) adults during normothermic and heat stress (1.5°C increase in core temperature) conditions. During heat stress, increases in cardiac output were attenuated in aged adults (+2.5 ± 0.3 (95% CI) vs. young: +4.5 ± 0.5 l/min, P < 0.01) because of an attenuated chronotropic response (+30 ± 4 vs. young: +42 ± 5 beats/min, P < 0.01). In contrast to our hypothesis, a leftward shift of the Frank-Starling relation maintained stroke volume during heat stress in aged adults (76 ± 8 vs. normothermic: 74 ± 8 ml, P = 0.38) despite reductions in cardiac filling pressure (6.6 ± 1.0 vs. normothermic: 8.9 ± 1.1 mmHg, P < 0.01). In a subset of participants, volume loading was used to return cardiac filling pressure during heat stress to normothermic values, which resulted in a greater stroke volume for a given cardiac filling pressure in both groups. These results demonstrate that the Frank-Starling relation shifts during heat stress in healthy young and aged adults, thereby preserving stroke volume despite reductions in cardiac filling pressures.

Strong but diverging clonality - climate relationships of different plant clades explain weak overall pattern across China

The clonal strategy should be relatively important in stressful environments (i.e. of low resource availability or harsh climate), e.g. in cold habitats. However, our understanding of the distribution pattern of clonality along environmental gradients is still far from universal. The weakness and inconsistency of overall clonality-climate relationships across taxa, as reported in previous studies, may be due to different phylogenetic lineages having fundamental differences in functional traits other than clonality determining their climate response. Thus, in this study we compared the clonality-climate relationships along a latitudinal gradient within and between different lineages at several taxonomic levels, including four major angiosperm lineages (Magnoliidae, Monocotyledoneae, Superrosidae and Superasteridae), orders and families. To this aim we used a species clonality dataset for 4015 vascular plant species in 545 terrestrial communities across China. Our results revealed clear predictive patterns of clonality proportion in relation to environmental gradients for the predominant representatives of each of the taxonomic levels above, but the relationships differed in shape and strength between the 4 major angiosperm lineages, between the 12 orders and between the 12 families. These different relationships canceled out one another when all lineages at a certain taxonomic level were pooled. Our findings highlight the importance of explicitly accounting for the functional or taxonomic scale for studying variation in plant ecological strategy across environmental gradients.

Restoration of Pulsatile Flow Reduces Sympathetic Nerve Activity Among Individuals With Continuous-Flow Left Ventricular Assist Devices

Background—

Current-generation left ventricular assist devices provide circulatory support that is minimally or entirely nonpulsatile and are associated with marked increases in muscle sympathetic nerve activity (MSNA), likely through a baroreceptor-mediated pathway. We sought to determine whether the restoration of pulsatile flow through modulations in pump speed would reduce MSNA through the arterial baroreceptor reflex.

Methods and Results—

Ten men and 3 women (54±14 years) with Heartmate II continuous-flow left ventricular assist devices underwent hemodynamic and sympathetic neural assessment. Beat-to-beat blood pressure, carotid ultrasonography at the level of the arterial baroreceptors, and MSNA via microneurography were continuously recorded to determine steady-state responses to step changes (200–400 revolutions per minute) in continuous-flow left ventricular assist device pump speed from a maximum of 10 480±315 revolutions per minute to a minimum of 8500±380 revolutions per minute. Reductions in pump speed led to increases in pulse pressure (high versus low speed: 17±7 versus 26±12 mm Hg; P <0.01), distension of the carotid artery, and carotid arterial wall tension ( P <0.05 for all measures). In addition, MSNA was reduced (high versus low speed: 41±15 versus 33±16 bursts per minute; P <0.01) despite a reduction in mean arterial pressure and was inversely related to pulse pressure ( P =0.037).

Conclusions—

Among subjects with continuous-flow left ventricular assist devices, the restoration of pulsatile flow through modulations in pump speed leads to increased distortion of the arterial baroreceptors with a subsequent decline in MSNA. Additional study is needed to determine whether reduction of MSNA in this setting leads to improved outcomes.

Winners always win: growth of a wide range of plant species from low to future high CO2

Evolutionary adaptation to variation in resource supply has resulted in plant strategies that are based on trade-offs in functional traits. Here, we investigate, for the first time across multiple species, whether such trade-offs are also apparent in growth and morphology responses to past low, current ambient, and future high CO 2 concentrations. We grew freshly germinated seedlings of up to 28 C3 species (16 forbs, 6 woody, and 6 grasses) in climate chambers at 160 ppm, 450 ppm, and 750 ppm CO 2. We determined biomass, allocation, SLA (specific leaf area), LAR (leaf area ratio), and RGR (relative growth rate), thereby doubling the available data on these plant responses to low CO 2. High CO 2 increased RGR by 8%; low CO 2 decreased RGR by 23%. Fast growers at ambient CO 2 had the greatest reduction in RGR at low CO 2 as they lost the benefits of a fast-growth morphology (decoupling of RGR and LAR [leaf area ratio]). Despite these shifts species ranking on biomass and RGR was unaffected by CO 2, winners continued to win, regardless of CO 2. Unlike for other plant resources we found no trade-offs in morphological and growth responses to CO 2 variation, changes in morphological traits were unrelated to changes in growth at low or high CO 2. Thus, changes in physiology may be more important than morphological changes in response to CO 2 variation.