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Purpose Root exudation of organic acids (OAs) facilitates plant P uptake from soil, playing a key role in rhizosphere nutrient availability. However, OA exudation responses to CO2 concentrations and water availability remain largely untested. Methods We examined the effects of CO2 and water on OA exudates in three Australian woodland species: Eucalyptus tereticornis, Hakea sericea and Microlaena stipoides. Seedlings were grown in a glasshouse in low P soil, exposed to CO2 (400 ppm [aCO2] or 540 ppm [eCO2]) and water treatments (100% water holding capacity [high-watered] or 25–50% water holding capacity [low-watered]). After six weeks, we collected OAs from rhizosphere soil (OArhizo) and trap solutions in which washed roots were immersed (OAexuded). Results For E. tereticornis, the treatments changed OArhizo composition, driven by increased malic acid in plants exposed to eCO2 and increased oxalic acid in low-watered plants. For H. sericea, low-watered plants had higher OAexuded per plant (+ 116%) and lower OArhizo per unit root mass (–77%) associated with larger root mass but fewer cluster roots. For M. stipoides, eCO2 increased OAexuded per plant (+ 107%) and per unit root mass (+ 160%), while low-watered plants had higher citric and lower malic acids for OArhizo and OAexuded: changes in OA amounts and composition driven by malic acid were positively associated with soil P availability under eCO2. Conclusion We conclude that eCO2 and altered water availability shifted OAs in root exudates, modifying plant–soil interactions and the associated carbon and nutrient economy.

In rice, the lysin motif (LysM) receptor-like kinase OsCERK1, originally identified as the essential molecule for chitin-triggered immunity, plays a key role in arbuscular mycorrhizal (AM) symbiosis. As we previously reported, although AM colonization was largely repressed at 2 weeks after inoculation (WAI), arbuscules were observed at 5 WAI in oscerk1 mutant. Conversely, most mutant plants that defect the common symbiosis signaling pathway exhibited no arbuscule formation. Concerning the reason for this characteristic phenotype of oscerk1, we speculated that OsRLK10, which is a putative paralog of OsCERK1, may have a redundant function in AM symbiosis. The protein sequences of these two genes are highly conserved and it is estimated that the gene duplication occurred 150 million years ago. Here we demonstrated that OsCERK2/OsRLK10 induced AM colonization and chitin-triggered reactive oxygen species production in oscerk1 knockout mutant as similar to OsCERK1. The oscerk2 mutant showed a slight but significant reduction of AM colonization at 5 WAI, indicating the contribution of OsCERK2 for AM symbiosis. However, the oscerk2;oscerk1 double-knockout mutant produced arbuscules at 5 WAI as similar to the oscerk1 mutant, indicating that the redundancy of OsCERK1 and OsCERK2 did not explain the mycorrhizal colonization in oscerk1 at 5 WAI. These results indicated that OsCERK2 has a potential to regulate both chitin-triggered immunity and AM symbiosis and at least partially contributes to AM symbiosis in rice though the contribution of OsCERK2 appears to be weaker than that of OsCERK1.

Here we present a novel model supplementing existing theories of soil organic matter (SOM) decomposition, based on evolutionary-ecological principles rather than chemical or physical limitations to decomposition. We argue that decomposition of some substrates, in particular nitrogen-rich non-hydrolyzable matter (NHLS), may be constrained by spatial competition from opportunists (Bonner et al., 2022). Our model is based on two linked hypotheses: (1) From an evolutionary point of view, microbes should optimise their enzyme production to maximise the net fitness gain (F), and they should only decompose NHLS if the uptake of decomposition products (S) brings a net fitness gain (F > 0) in terms of growth minus costs of enzyme production. (2) F strongly depends on the fraction of decomposition products absorbed by the decomposer, i.e. the return on enzyme investment, which depends on the distance to the substrate and the competition from opportunistic bacteria. A minimum ‘safe’ distance for oxidative decomposition is included, based on the idea that cost of oxidative stress to the decomposer will surpass potential gain from decomposition when the activity is too close. Although the model predictions have not been tested directly against observations, they provide proof-of-concept that substrate can be spared decomposition and accumulate even when it is physically and chemically accessible. Due to the spatial competition effect, it is not profitable for either bacteria or decomposer fungi to decompose NHLS under certain conditions. Our framework can help explain a variety of SOM dynamics, including priming and the suppression of decomposition by nitrogen addition. ReferenceBonner MTL, Franklin O, Hasegawa S, Näsholm T. 2022. Those who can don't want to, and those who want to can't: An eco-evolutionary mechanism of soil carbon persistence. Soil Biology and Biochemistry 174: 108813.

Roughly 2 billion ha of land are degraded and in need of ecological restoration worldwide. Active restoration frequently involves revegetation, which leads to the dilemma of whether to conduct direct seeding or to plant nursery-grown seedlings. The choice of revegetation method can regulate plant survival and performance, with economic implications that ultimately feed back to our capacity to conduct restoration. We followed a peerreviewed protocol to develop a systematic map that collates, describes and catalogues the available studies on how seeding compares to planting in achieving restoration targets. We compiled a database with the characteristics of all retrieved studies, which can be searched to identify studies of particular locations and habitats, objectives of restoration, plant material, technical aspects, and outcomes measured. The search was made in eight languages and retrieved 3355 publications, of which 178 were retained. The systematic map identifies research gaps, such as a lack of studies in the global South, in tropical rainforests, and covering a long time period, which represent opportunities to expand field-based research. Additionally, many studies overlooked reporting on important technical aspects such as seed provenance and nursery cultivation methods, and others such as watering or seedling protection were more frequently applied for planting than for seeding, which limits our capacity to learn from past research. Most studies measured outcomes related to the target plants but avoided measuring general restoration outcomes or economic aspects. This represents a relevant gap in research, as the choice of revegetation method is greatly based on economic aspects and the achievement of restoration goals goes beyond the establishment of plants. Finally, we identified a substantial volume of studies conducted in temperate regions and over short periods (0–5 y). This research cluster calls for a future in-depth synthesis, potentially through meta-analysis, to reveal the overall balance between seeding and planting and assess whether the response to this question is mediated by species traits, environmental characteristics, or technical aspects. Besides identifying research clusters and gaps, the systematic map database allows managers to find the most relevant scientific literature on the appropriateness of seeding vs. planting for particular conditions, such as certain species or habitats., Spanish Ministerio de Ciencia, Innovacion y Universidades/FEDER RTI 2018-096187-J-100 RYC 2020-029407-I, Ministry of Science and Innovation, Spain (MICINN) TED2021.130976 B.I00, Consejeria de Economia, Conocimiento, Empresas y Universidad de la Junta de Andalucia/FEDER P18-RT-1927, Universidad de Granada / CBUA

In recent years, there has been a great deal of research on teleoperation of robots, and many end-effector-oriented control systems have been proposed, but these systems have difficulties in performing manipulation tasks with physical contacts between the target object, the robot, and the environment, such as dual-arm manipulation, because these systems can only express the end-effectors’ pose and force commands. In this study, we propose Target-object-oriented User Interface (TOOUI) that focuses on the target object rather than the end effectors of the robot, and develop a tangible device called Miniature Tangible Cube as a TOOUI. Through this device, the pilot can express the target orientation and contact state of the target object, and the robot can be teleoperated to do dual-arm manipulation tasks with geometric and physical constraints. For dual-arm manipulation tasks, we also implement a dual-arm telemanipulation system with the Miniature Tangible Cube using the motion planner based on state machine. In the experiments, we evaluated our system with the Miniature Tangible Cube by conducting dual-arm manipulation tasks with the dual-arm robot PR2 in the real world.

Background The improvement of anaemia over time by erythropoiesis stimulating agent (ESA) is associated with better survival in haemodialysis patients. We previously reported that erythrocyte creatine content, a marker of erythropoietic capacity, was a reliable marker to estimate the effectiveness of ESA. The aim of this study was to examine the accuracy and clinical usefulness of erythrocyte creatine content to predict the improvement of anaemia in haemodialysis patients. Methods ESA dose was fixed 3 months prior to the enrollment and was maintained throughout the study period. Erythrocyte creatine content and haematologic indices were measured at baseline in 92 patients receiving maintenance haemodialysis. Haemoglobin was also measured 3 months after. Improvement of anaemia was defined as ≥ 0.8 g/dL change in haemoglobin from baseline to 3 months. Results Erythrocyte creatine content was significantly higher in 32 patients with improvement of anaemia compared to 60 patients with no improvement of anaemia (2.47 ± 0.74 vs. 1.57 ± 0.49 μmol/gHb, P = 0.0001). When 9 variables (erythrocyte creatine content, ESA dose, reticulocyte, haptoglobin, haemoglobin at baseline, serum calcium, intact parathyroid hormone, transferrin saturation and serum ferritin) were used in the multivariate logistic regression analysis, erythrocyte creatine emerged as the most important variable associated with the improvement of anaemia (P = 0.0001). The optimal cut-off point of erythrocyte creatine content to detect the improvement of anaemia was 1.78 μmol/gHb (Area under the curve: 0.86). Sensitivity and specificity of erythrocyte creatine content to detect the improvement of anaemia were 90.6% and 83.3%. Conclusion Erythrocyte creatine content is a reliable marker to predict the improvement of anaemia 3 months ahead in patients receiving maintenance haemodialysis.

Purpose: Root exudation of organic acids (OAs) facilitates plant P uptake from soil, playing a key role in rhizosphere nutrient economy. However, OA exudation responses to elevated CO2 concentrations (eCO2) and water availability remain largely untested.Methods: We examined the interactive effects of CO2 and water on OA exudates in three Australian woodland species: Eucalyptus tereticornis, Hakea sericea and Microlaena stipoides. Seedlings were grown in a glasshouse in low P soil, exposed to CO2 (400 ppm [aCO2] or 540 ppm [eCO2]) and water treatments (100% water holding capacity [high-watered] or 25–50% water holding capacity [low-watered]). After six weeks, we collected OAs from rhizosphere soil (OArhizo) and trap solutions in which washed roots were immersed (OAexuded). Results: For E. tereticornis, the treatments changed OArhizo composition, driven by increased malic acid exposed to eCO2 and increased oxalic acid in low-watered plants. For H. sericea, low-watered plants had higher OAexuded per plant (+116%) and lower OArhizo per unit root mass (–77%) associated with larger root mass but fewer cluster roots. For M. stipoides, eCO2 increased OAexuded per plant (+107%) and per unit root mass (+160%), while low-watered plants had higher citric and lower malic acids for OArhizo and OAexuded: changes in OA amounts and composition driven by malic acid were positively associated with soil P availability under eCO2.Conclusion: We conclude that eCO2 and altered water availability shifted OAs in root exudates, modifying plant–soil interactions and the associated carbon and nutrient economy.

Left coronary artery malperfusion is a fatal complication of acute type A aortic dissection. However, effective treatment strategies have not yet been established. Herein, we report two cases of left coronary artery malperfusion successfully treated with different preoperative catheter interventions, followed by a central aortic repair. Preoperative coronary intervention ensuring the blood flow to the left coronary artery might be essential if a coronary angiogram was performed prior to the diagnosis and treatment.

Understorey plant communities comprise a large portion of biodiversity of forests and woodlands globally, where they contribute to tree species dynamics, biogeochemical cycling and carbon sequestration. Here we evaluated the effects of elevated CO2 (400 vs. 550 ppm) on the spatial distribution of understorey plant communities from a mature eucalypt woodland in Eastern Australia (EucFACE experiment). Three years of elevated CO2 resulted in a loss of the characteristic aggregated and segregated spatial pattern of species richness at both short and long distances (20 cm–227 cm), respectively. Changes in spatial patterns emerged over time, indicating that these results are due to a relatively slow reordering of the understorey plant community. In contrast, when analysed from a multivariate perspective, changes in terms of community composition were not as clear as changes in the spatial rearrangement of plant communities. Synthesis. Given that the spatial patterns of communities are likely a reflection of the way in which multiple species interact and how energy and matter flow throw ecosystems, community reordering due to global change may have far-reaching implications in terms of ecosystem functioning. Moreover, subtle early changes in the spatial pattern of understorey plant communities may represent an early-warning indicator of global change impacts in forest ecosystems.

The cystine/glutamate antiporter, system x(c)(-), is essential for the efficient uptake of cystine into cells. Interest in the mechanisms of system x(c)(-)function soared with the recognition that system x(c)(-)presents the most upstream node of ferroptosis, a recently described form of regulated necrosis relevant for degenerative diseases and cancer. Since targeting system x(c)(-)hold the great potential to efficiently combat tumor growth and metastasis of certain tumors, we disrupted the substrate-specific subunit of system x(c)(-), xCT (SLC7A11) in the highly metastatic mouse B16F10 melanoma cell line and assessed the impact on tumor growth and metastasis. Subcutaneous injection of tumor cells into the syngeneic B16F10 mouse melanoma model uncovered a marked decrease in the tumor-forming ability and growth of KO cells compared to control cell lines. Strikingly, the metastatic potential of KO cells was markedly reduced as shown in several in vivo models of experimental and spontaneous metastasis. Accordingly, survival rates of KO tumor-bearing mice were significantly prolonged in contrast to those transplanted with control cells. Analyzing the in vitro ability of KO and control B16F10 cells in terms of endothelial cell adhesion and spheroid formation revealed that xCT expression indeed plays an important role during metastasis. Hence, system x(c)(-)emerges to be essential for tumor metastasis in mice, thus qualifying as a highly attractive anticancer drug target, particularly in light of its dispensable role for normal life in mice.

Recently, robots are introduced to warehouses and factories for automation and are expected to execute dual-arm manipulation as human does and to manipulate large, heavy and unbalanced objects. We ...

Background: One of the main causes of anaemia in patients with end-stage renal disease is relative deficiency in erythropoietin production. Recombinant human erythropoietin (rHuEpo), a potent haematopoietic growth factor, is used to treat anaemia in haemodialysis patients. The effect of rHuEpo is usually assessed by haematological indices such as red blood cell count, haemoglobin concentration and haematocrit, but erythrocyte indices do not provide information of the rapid change in erythropoietic activity. As erythrocyte creatine directly assess erythropoiesis, the aim of this study was to evaluate the effect of rHuEpo in haemodialysis patients by measuring erythrocyte creatine. Methods: rHuEpo dose was fixed 3 months prior to the enrollment and was maintained throughout the entire study period. Eerythrocyte creatine was measured with haematologic indices in 83 haemodialysis patients. Haemoglobin was also measured 3 months after. Results: rHuEpo dose (152.4±62.9 vs. 82.2±45.5 units/kg/week, P=0.0001) and erythrocyte creatine (2.07±0.73 vs. 1.60±0.41 µmol/gHb, p=0.0003) were significantly higher in 27 patients with haemoglobin 0.1g/dL) was observed in 37 patients, whereas haemoglobin did not increase in 46 patients. Erythrocyte creatine was significantly higher in patients with increase in haemoglobin compared to those without (2.04±0.64 vs. 1.52±0.39 µmol/gHb, p Conclusion: Erythrocyte creatine, a useful marker of erythropoietic capacity, is a reliable marker to estimate ameliorative effectiveness of rHuEpo in haemodialysis patients.

Ionic liquids (ILs) have unique physicochemical properties such as favorable solubility of organic and inorganic compounds, relatively high ionic conductivity, no measurable vapor pressure, high thermal stability, low flammability, etc. ILs are also promising liquid materials available for various applications because their function can be easily controlled by changing the combination of cations and anions and by introducing substituents. Although many kinds of ILs have already been investigated, phosphonium cation based ILs have rarely been proposed. We have previously designed and synthesized the phosphonium ILs together with typical sulfonylamide-based anions such as bis(trifluoromethylsulfonyl)amide and bis(fluorosulfonyl)amide anions.1,2) On the other hand, interests in phosphonium ILs consisting of the other anions is increasing for diverse applications. In this work, we design and prepare the ILs based on tetrabutylphosphonium cation (P4444 +) together with various sulfonate-based anions (Fig. 1), characterizing their physicochemical properties as a new family of ILs. The phosphonium IL was prepared by an aqueous neutralization reaction of tetrabutylphosphonium hydroxide with the stoichiometric amounts of various sulfonic acids. The obtained phosphonium ILs were isolated by water evaporation, and were dried in vacuo for at least 1 day. The physicochemical properties of ILs, e.g. density, viscosity, conductivity (ac impedance method) and thermal decomposition temperature (thermogravimetric analysis), were measured under argon atmosphere. The phosphonium salts based on unsubstituted sulfonate anions such as SO3CH3, SO3CH2CH3 and SO3(CH2)2CH3 were white crystalline solids at room temperature, whereas both amino- and hydroxy- substituted sulfonate salts were viscous liquids at room temperature. All phosphonium salts obtained were hydrophilic. Table 1 summarizes the physicochemical properties of phosphonium ILs based on amino- and hydroxy-substituted sulfonate anions. These phosphonium ILs exhibited considerably high viscosities when compared to the previously published viscosity value of P4444-lactate IL (415 mPa s at 25 °C)3), which suggests that the electrostatic interaction between P4444 cation and the sulfonate anions is much stronger than those in the case of carboxylate-based phosphonium ILs. It should be noted that P4444-SO3(CH2)3NH2 obviously indicated not only the highest density but also the highest viscosity and the lowest conductivity, which might be due to the fact that the IL has the largest anion to give a significant van der Waals interaction. Figure 1

For warehouse automation, stocking items in storage shelves (stowing stage) and picking them off the shelves (picking stage) should be automated. To achieve this, we propose a Suction Pinching Hand, an unstable-to-stable transformation (UST) strategy, and an entrance passing (EP) strategy. The Suction Pinching Hand has two underactuated fingers and one extendable and foldable suction finger whose fingertip has a suction cup. The suction finger is useful during the picking stage to enter and manipulate various objects in a cluttered narrow space, with such spaces being typical in efficient warehouses. As this manipulation is sometimes unstable, the underactuated fingers are used simultaneously to stabilize the grasp after the suction finger moves the object to a relatively open space. The UST strategy realizes the transition from unstable object manipulation in a narrow space to stabilization in a relatively open space. In the stowing stage, proximity sensors in the underactuated fingers are used to sense when the object is touched, for securing a direct pinching motion executable in the stowing stage. Finally, the EP strategy ensures that the picked object is able to pass through the entrance of the shelf bin and be successfully stowed. Experiments demonstrate both the ability of our robot hand to grasp various objects stably and safely, and the effectiveness of the UST and EP strategies during the picking and stowing stages.

There is a growing body of evidence that plants uptake a monumental amount of organic forms of nitrogen (N) like amino acids in addition to those in inorganic forms. An amino acid-based fertiliser has been shown to improve seedling development and commercialised. Boreal forests store a substantial amount of carbon (C) in the soil and this is widely known to be further enhanced by the addition of inorganic nitrogen fertiliser via hampered decomposition. However, very little is known about how amino acid-based fertiliser influences C/N cycling in the boreal soils. The organic forms of N supply not only nitrogen but also carbon. If the previously demonstrated suppression of SOM decomposition is owing to altered C:N ratios in substrates, the amino acid-based fertiliser may not have as pronounced effects on the soil as the inorganic fertiliser. We have examined the impacts of the organic fertiliser (100 kg N and 130 kg C ha-1 year-1)—arginine—on the chemical composition of soil organic matter in a boreal forest in comparison to non-fertilised, inorganic fertilised (ammonium-nitrate) and C-controlled inorganic fertilised (sucrose + ammonium-nitrate) conditions. The soil organic matter was characterised using two metrics: pyrolysis GC/MS and 13C solid-state nuclear magnetic resonance (NMR), combined with enzymological and metagenomic analysis.We will be presenting the results following 4-year of the fertiliser treatments. Preliminary results have shown that there is limited evidence that the fertiliser treatments alter soil C/N cycing in four years. Nevertheless, the chemical composition in SOM under the organic fertiliser condition was similar to that under C-controlled compared to inorganic fertiliser treatment.

Reliable manipulation of soil organic matter (SOM) – a necessity for optimal land management – is constrained by our limited mechanistic understanding of SOM formation. Here we add to existing frameworks a novel mechanistic element that may underpin SOM dynamics, based on evolutionary-ecological rather than chemical or physical limitations to decomposition. We argue that decomposition of some substrates may be ecologically constrained in mycelial fungi, evolutionarily constrained in co-operating bacteria, and geometrically constrained in unicellular microbes. We describe and test a mathematical model based on our framework, providing a proof-of-concept that substrate can plausibly be spared decomposition and accumulate even when it is physically and chemically accessible. Our framework can explain a variety of SOM dynamics, including priming and the suppression of decomposition by nitrogen addition, as well as the typical composition of SOM. An augmented mechanistic framework for understanding SOM dynamics can help guide targeted empirical study, which in turn can contribute to more optimised land management.

Machine learning is applied to a large number of modern devices that are essential in building an energy-efficient smart society. Audio and face recognition are among the most well-known technologies that make use of such artificial intelligence. In materials research, machine learning is adapted to predict materials with certain functionalities, an approach often referred to as materials informatics. Here, we show that machine learning can be used to extract material parameters from a single image obtained in experiments. The Dzyaloshinskii–Moriya (DM) interaction and the magnetic anisotropy distribution of thin-film heterostructures, parameters that are critical in developing next-generation storage class magnetic memory technologies, are estimated from a magnetic domain image. Micromagnetic simulation is used to generate thousands of random images for training and model validation. A convolutional neural network system is employed as the learning tool. The DM exchange constant of typical Co-based thin-film heterostructures is studied using the trained system: the estimated values are in good agreement with experiments. Moreover, we show that the system can independently determine the magnetic anisotropy distribution, demonstrating the potential of pattern recognition. This approach can considerably simplify experimental processes and broaden the scope of materials research.

Boreal forests store approximately 470 Pg of carbon (C) in the soil, and rates of soil C accumulation are significantly enhanced by long-term nitrogen (N) enrichment. Dissecting the compositional profile of soils could help better understand the potential mechanisms driving changes in C cycling under enriched N conditions. We examined the impacts of long-term N addition on the chemical composition of soil organic matter (SOM) in a mature boreal forest. Two large experimental plots (15 ha each) were established: a control and a fertilised plot. The latter received NH4NO3 fertilizer at an average rate of 75 kg N ha−1 year−1 for 12 years. While the centre of this plot received the prescribed amounts of fertilizer, the year-to-year variation in distribution of fertilizer around the designated edges of the plot created a gradient in N-loading. Along this gradient, a compositional shift in SOM in the organic horizon was assessed using two methods: pyrolysis-gas chromatography/mass spectrometry (GC/MS) and solid-state 13C nuclear magnetic resonance spectroscopy (13C NMR). Both of these methods revealed that the chemical composition of SOM changed with increasing N loading, with an increased fraction of lignin derivatives (i.e., aromatic, methoxy/N-alkyl C) relative to that of carbohydrate (i.e., O-alkyl C), accompanied by increased soil C mass (kg m−2) at the fertilised plot. Also, the relative abundance of N compounds in the pyrolysis products increased with the N loading, mainly due to increased methyl N-acetyl-α-D-glucosaminide in the F/H horizon, plausibly of microbial origin. Microbial N processing likely contributed to soil accumulation of fertilizer-derived N. Our results corroborate the hypothesis that addition of inorganic N suppresses enzymatic white-rot decomposition relative to non-enzymatic brown-rot oxidation. Taken together, our study suggests that N enrichment leads to a selective accumulation of lignin-derived compounds and points to a key role of such compounds for N-induced SOM accumulation.

Atmospheric carbon dioxide enrichment (eCO2) can enhance plant carbon uptake and growth1–5, thereby providing an important negative feedback to climate change by slowing the rate of increase of the atmospheric CO2 concentration6. Although evidence gathered from young aggrading forests has generally indicated a strong CO2 fertilization effect on biomass growth3–5, it is unclear whether mature forests respond to eCO2 in a similar way. In mature trees and forest stands7–10, photosynthetic uptake has been found to increase under eCO2 without any apparent accompanying growth response, leaving the fate of additional carbon fixed under eCO2 unclear4,5,7–11. Here using data from the first ecosystem-scale Free-Air CO2 Enrichment (FACE) experiment in a mature forest, we constructed a comprehensive ecosystem carbon budget to track the fate of carbon as the forest responded to four years of eCO2 exposure. We show that, although the eCO2 treatment of +150 parts per million (+38 per cent) above ambient levels induced a 12 per cent (+247 grams of carbon per square metre per year) increase in carbon uptake through gross primary production, this additional carbon uptake did not lead to increased carbon sequestration at the ecosystem level. Instead, the majority of the extra carbon was emitted back into the atmosphere via several respiratory fluxes, with increased soil respiration alone accounting for half of the total uptake surplus. Our results call into question the predominant thinking that the capacity of forests to act as carbon sinks will be generally enhanced under eCO2, and challenge the efficacy of climate mitigation strategies that rely on ubiquitous CO2 fertilization as a driver of increased carbon sinks in global forests. Carbon dioxide enrichment of a mature forest resulted in the emission of the excess carbon back into the atmosphere via enhanced ecosystem respiration, suggesting that mature forests may be limited in their capacity to mitigate climate change.