Carbon allocation to root exudates is maintained in mature temperate tree species under drought

- Carbon (C) exuded via roots is proposed to increase under drought and facilitate important ecosystem functions. However, it is unknown how exudate quantities relate to the total C budget of a drought-stressed tree, that is, how much of net-C assimilation is allocated to exudation at the tree level. - We calculated the proportion of daily C assimilation allocated to root exudation during early summer by collecting root exudates from mature Fagus sylvatica and Picea abies exposed to experimental drought, and combining above- and belowground C fluxes with leaf, stem and fine-root surface area. - Exudation from individual roots increased exponentially with decreasing soil moisture, with the highest increase at the wilting point. Despite c. 50% reduced C assimilation under drought, exudation from fine-root systems was maintained and trees exuded 1.0% (F. sylvatica) to 2.5% (P. abies) of net C into the rhizosphere, increasing the proportion of C allocation to exudates two- to three-fold. Water-limited P. abies released two-thirds of its exudate C into the surface soil, whereas in droughted F. sylvatica it was only one-third. - Across the entire root system, droughted trees maintained exudation similar to controls, suggesting drought-imposed belowground C investment, which could be beneficial for ecosystem resilience

Healthcare consumption of patients with left ventricular assist device: real-world data

BACKGROUND: A left ventricular assist device (LVAD) is a life-saving but intensive therapy for patients with end-stage heart failure. We evaluated the healthcare consumption in a cohort of LVAD patients in our centre over 6 years. METHODS: All patients with a primary LVAD implantation at the University Medical Centre Utrecht in Utrecht, the Netherlands from 2016 through 2021 were included in this analysis. Subsequent hospital stay, outpatient clinic visits, emergency department visits and readmissions were recorded. RESULTS: During the investigated period, 226 LVADs were implanted, ranging from 32 in 2016 to 45 in 2020. Most LVADs were implanted in patients aged 40-60 years, while they were supported by or sliding on inotropes (Interagency Registry for Mechanically Assisted Circulatory Support class 2 or 3). Around the time of LVAD implantation, the median total hospital stay was 41 days. As the size of the LVAD cohort increased over time, the total annual number of outpatient clinic visits also increased, from 124 in 2016 to 812 in 2021 (p = 0.003). The numbers of emergency department visits and readmissions significantly increased in the 6‑year period as well, with a total number of 553 emergency department visits and 614 readmissions. Over the years, the annual number of outpatient clinic visits decreased by 1 per patient-year follow-up, while the annual numbers of emergency department visits and readmissions per patient-year remained stable. CONCLUSION: The number of patients supported by an LVAD has grown steadily over the last years, requiring a more specialised healthcare in this particular population

TECRL, a new life‐threatening inherited arrhythmia gene associated with overlapping clinical features of both LQTS and CPVT

Genetic causes of many familial arrhythmia syndromes remain elusive. In this study, whole-exome sequencing (WES) was carried out on patients from three different families that presented with life-threatening arrhythmias and high risk of sudden cardiac death (SCD). Two French Canadian probands carried identical homozygous rare variant in TECRL gene (p.Arg196Gln), which encodes the trans-2,3-enoyl-CoA reductase-like protein. Both patients had cardiac arrest, stress-induced atrial and ventricular tachycardia, and QT prolongation on adrenergic stimulation. A third patient from a consanguineous Sudanese family diagnosed with catecholaminergic polymorphic ventricular tachycardia (CPVT) had a homozygous splice site mutation (c.331+1G>A) in TECRL Analysis of intracellular calcium ([Ca(2+)]i) dynamics in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) generated from this individual (TECRLHom-hiPSCs), his heterozygous but clinically asymptomatic father (TECRLHet-hiPSCs), and a healthy individual (CTRL-hiPSCs) from the same Sudanese family, revealed smaller [Ca(2+)]i transient amplitudes as well as elevated diastolic [Ca(2+)]i in TECRLHom-hiPSC-CMs compared with CTRL-hiPSC-CMs. The [Ca(2+)]i transient also rose markedly slower and contained lower sarcoplasmic reticulum (SR) calcium stores, evidenced by the decreased magnitude of caffeine-induced [Ca(2+)]i transients. In addition, the decay phase of the [Ca(2+)]i transient was slower in TECRLHom-hiPSC-CMs due to decreased SERCA and NCX activities. Furthermore, TECRLHom-hiPSC-CMs showed prolonged action potentials (APs) compared with CTRL-hiPSC-CMs. TECRL knockdown in control human embryonic stem cell-derived CMs (hESC-CMs) also resulted in significantly longer APs. Moreover, stimulation by noradrenaline (NA) significantly increased the propensity for triggered activity based on delayed afterdepolarizations (DADs) in TECRLHom-hiPSC-CMs and treatment with flecainide, a class Ic antiarrhythmic drug, significantly reduced the triggered activity in these cells. In summary, we report that mutations in TECRL are associated with inherited arrhythmias characterized by clinical features of both LQTS and CPVT Patient-specific hiPSC-CMs recapitulated salient features of the clinical phenotype and provide a platform for drug screening evidenced by initial identification of flecainide as a potential therapeutic. These findings have implications for diagnosis and treatment of inherited cardiac arrhythmias

Repetitive seasonal drought causes substantial species-specific shifts in fine-root longevity and spatio-temporal production patterns in mature temperate forest trees

Temperate forest ecosystems are exposed to a higher frequency, duration and severity of drought. To promote forest longevity in a changing climate, we require a better understanding of the long-term impacts of repetitive drought events on fine-root dynamics in mature forests. Using minirhizotron methods, we investigated the effect of seasonal drought on fine-root dynamics in single-species and mixed-species arrangements of Fagus sylvatica (European beech) and Picea abies (Norway spruce) by means of a 4-yr-long throughfall-exclusion experiment. Fine-root production of both species decreased under drought. However, this reduction was not evident for P. abies when grown intermixed with F. sylvatica. Throughfall-exclusion prolonged the lifespan of P. abies roots but did not change the lifespan of F. sylvatica roots, except in 2016. Fagus sylvatica responded to drought by reducing fine-root production at specific depths and during roof closure. This is the first study to examine long-term trends in mature forest fine-root dynamics under repetitive drought events. Species-specific fine-root responses to drought have implications for the rate and depth of root-derived organic matter supply to soil. From a root dynamics perspective, intermixing tree species is not beneficial to all species but dampens drought impacts on the belowground productivity of P. abies

Recycling slaughterhouse waste into fertilizer: how do pyrolysis temperature and biomass additions affect phosphorus availability and chemistry?

BACKGROUND: Pyrolysis of slaughterhouse waste could promote more sustainable phosphorus (P) usage through the development of alternative P fertilizers. This study investigated how pyrolysis temperature (220, 350, 550 and 750°C), rendering before pyrolysis, and wood or corn biomass additions affect P chemistry in bone char, plant availability, and its potential as P fertilizer. RESULTS: Linear combination fitting of synchrotron-based X-ray Absorption Near Edge Structure (XANES) spectra demonstrated that higher pyrolysis temperatures decreased the fit with organic P references, but increased the fit with a hydroxyapatite (HA) reference, used as indicator of high calcium phosphate (CaP) crystallinity. The fit to the HA reference increased approximately from 0 to 69% in bone with meat residue and from 20 to 95% in rendered bone. Biomass additions to the bone with meat residue reduced the fit to the HA reference by 83% for wood and 95% for corn, and additions to rendered bone by 37% for wood. No detectable aromatic P forms were generated by pyrolysis. High CaP crystallinity was correlated with low water-extractable P, but high formic acid-extractable P indicative of high plant availability. Bone char supplied available P which was only 24% lower than Triple Superphosphate fertilizer and two- to five-fold higher than rock phosphate. CONCLUSION: Pyrolysis temperature and biomass additions can be used to design phosphorus fertilizer characteristics of bone char through changing CaP crystallinity that optimize P availability to plants.We are grateful for the support by the Towards Sustainability Foundation, CARE-Cornell Impact through Innovations Fund, McKnight Foundation, Bradfield Award, Fulbright and Huygens Talent Scholarship Program. Use of the National Synchrotron Light Source, Brookhaven National Laboratory, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886. We acknowledge the support by Syed Khalid running beam line X19A

Phenolic root exudate and tissue compounds vary widely among temperate forest tree species and have contrasting effects on soil microbial respiration

Root-soil interactions fundamentally affect the terrestrial carbon (C) cycle and thereby ecosystem feedbacks to climate change. This study addressed the question whether the secondary metabolism of different temperate forest tree species can affect soil microbial respiration. We hypothesized that phenolics can both increase and decrease respiration depending on their function as food source, mobilizer of other soil resources, signaling compound, or toxin. We analyzed the phenolic compounds from root exudates and root tissue extracts of six tree species grown in a greenhouse using high-performance liquid chromatography (HPLC). We then tested the effect of individual phenolic compounds, representing the major identified phenylpropanoid compound classes, on microbial respiration through a five-day soil incubation. Phenolic root profiles were highly species-specific. Of the eight classes identified, flavonoids were the most abundant with flavanols being the predominating sub-class. Phenolic effects on microbial respiration ranged from a 26% decrease to a 46% increase, with reduced respiration occurring in the presence of compounds possessing a catechol ring. Tree species variation in root phenolic composition influences the magnitude and direction of root effects on microbial respiration. Our data support the hypothesis that functional group rather than biosynthetic class determines the root phenolic effect on soil C cycling.We are grateful for the support from the Cornell IGERT Cross-Scale Biogeochemistry and Climate program, David R. Atkinson Center Sustainable Biodiversity Fund, Kieckhefer Adirondack Fellowship, Bartlett Tree Foundation, and Andrew W. Mellon Foundation. We also thank Daniel Buckley, Tim Fahey, Jed Sparks and Kyle Wickings for their advice, Adrian Powell and Tara Webster for discussing HPLC analysis, Leah Rae McEwen for her help with Bio_Rad KnowItAll® 2017 Spectroscopy Software, Stephen Parry from Cornell Statistical Consulting Unit, and Cornell Nutrient Analysis Laboratories (CNAL) and Cornell University Stable Isotope Laboratory (COIL) for soil analysis. Lastly, we thank Juana Muñoz Ucros, Max Heitner, Cari Gostic and Andrew Harner for their help with root exudate collection and respiration measurements

Spatiotemporal patterns of rhizosphere microbiome assembly : From ecological theory to agricultural application

There is urgency in optimizing agricultural production in light of climate uncertainty, human population growth and resource limitations. The rhizosphere microbiome is a promising genetic resource, yet it is poorly understood. Additionally, research into rhizosphere microbial community assembly (MCA) lacks a consistent ecological framework that incorporates the dynamics of the occurring interactions. We explore the ecological principles that guide community establishment as they pertain to the rhizosphere while reviewing relevant research and highlighting the gaps in knowledge. We propose a conceptual model for studying the rhizosphere, and argue for higher resolution characterizations of the rhizosphere, under a framework of root and microbial traits that will determine its resulting composition. For this, we borrow concepts from ecological theory to chronologically describe MCA as a function of colonization, distribution and succession under changing plant-imposed filters. We argue that there is a need to consider the temporal and spatial scale of rhizosphere processes in a manner that is relevant to its microbial components. Finally, we discuss strategies for managing the rhizosphere microbiome for agriculture and the remaining gaps in knowledge that impede their application. Synthesis and applications. We aim to initiate a comprehensive conversation on ecological processes and plant and microbial traits that affect rhizosphere assembly. Rhizosphere microbiome research is relatively new and highly multidisciplinary. The use of a shared vocabulary and ecological theory will facilitate the development and advances in this discipline.</p

Phosphorus availability from bone char in a P-fixing soil influenced by root-mycorrhizae-biochar interactions

Aims: The objectives of this study were to evaluate (1) the fertilizer potential of bone char, (2) the effects of wood biochar on plant-available phosphorus (P), and (3) the role of root-mycorrhizae-biochar interactions in plant P acquisition from a P-fixing soil. Methods: Incubation and pot experiments were conducted with a P-fixing soil and maize with or without root hairs and arbuscular mycorrhizae (AM) inoculation. Olsen-, resin-P and plant P accumulation were used to estimate P availability from bone char, co-pyrolyzed bone char-wood biochar, and separate bone char and wood biochar additions produced at 60, 350 and 750 °C, and Triple Superphosphate (TSP). Results: Maize inoculated with AM showed similar P accumulation when fertilized with either 750 °C bone char or TSP. Pyrolyzing bone did not increase extractable P in soil in comparison to unpyrolyzed bone, apart from a 67 % increase in resin-extractable P after additions of bone char pyrolyzed at 350 °C. Despite greater Olsen-P extractability, co-pyrolysis of bone with wood reduced maize P uptake. Wood biochars reduced resin-P from bone char by 14–26 %, whereas oven-dried wood increased resin-P by 23 %. Conclusions: Bone char is an effective P fertilizer, especially if root-AM interactions are simultaneously considered. Biochar influences plant access to soil P and requires careful management to improve P availability

Specific spatio-temporal dynamics of absorptive fine roots in response to neighbor species identity in a mixed beech-spruce forest

Absorptive fine roots are an important driver of soil biogeochemical cycles. Yet, the spatio-temporal dynamics of those roots in the presence of neighboring species remain poorly understood. The aim of this study was to analyze shifts in absorptive fine-root traits in monoculture or mixtures of Fagus sylvatica [L.] and Picea abies [L.] Karst. We hypothesized that root competition would be higher under single-species than mixed-species interactions, leading to changes in (i) root survivorship, diameter and respiration and (ii) spatio-temporal patterns of root growth and death. Using minirhizotron methods, we monitored the timing and location of absorptive fine-root growth and death at an experimental forest in southern Germany from 2011 to 2013. We also measured root respiration in the spring and fall seasons of 2012 and 2013. Our findings show that the absorptive fine roots of F. sylvatica had a 50% higher risk of root mortality and higher respiration rates in the single-species compared to mixed-species zones. These results support our hypothesis that root competition is less intense for F. sylvatica in mixture versus monoculture. We were unable to find confirmation for the same hypothesis for P. abies. To analyze spatio-temporal patterns of absorptive fine-root production and mortality, we used a mixed-effects model considering root depth (space) and seasons (time) simultaneously. This analysis showed that F. sylvatica shifts root production towards shallower soil layers in mixed-species stands, besides significant seasonal fluctuations in root production depths for both species. Ultimately, the impact of neighbor species identity on root traits observed in this study has important implications for where, when and how fast root-facilitated carbon cycling takes place in single-species versus mixed-species forests. In addition, our study highlights the need for inclusion of absorptive fine-root spatio-temporal dynamics when examining belowground plant interactions and biogeochemical cycles.</p

Phosphorus availability from bone char in a P-fixing soil influenced by root-mycorrhizae-biochar interactions

Aims: The objectives of this study were to evaluate (1) the fertilizer potential of bone char, (2) the effects of wood biochar on plant-available phosphorus (P), and (3) the role of root-mycorrhizae-biochar interactions in plant P acquisition from a P-fixing soil. Methods: Incubation and pot experiments were conducted with a P-fixing soil and maize with or without root hairs and arbuscular mycorrhizae (AM) associations. Olsen-, resin-P and plant P accumulation were used to estimate P availability from bone char, co-pyrolyzed bone char-wood biochar, and separate bone char and wood biochar additions produced at 60, 350 and 750°C, and Triple Superphosphate (TSP). Results: Maize inoculated with AM showed similar P accumulation when fertilized with either 750°C bone char or TSP. Pyrolyzing bone did not increase extractable P in soil in comparison to unpyrolyzed bone, apart from a 67% increase in resin-extractable P after additions of bone char pyrolyzed at 350°C. Despite greater Olsen-P extractability, co-pyrolysis of bone with wood reduced maize P uptake. Wood biochars reduced resin-P from bone char by 14-26%, whereas oven-dried wood increased resin-P by 23%. Conclusions: Bone char is an effective P fertilizer, especially if root-AM interactions are simultaneously considered. Biochar influences plant access to soil P and requires careful management to improve P availability.We are grateful for support from the Towards Sustainability Foundation, CARE-Cornell Impact through Innovations Fund, McKnight Foundation, Bradfield Award, Fulbright and Huygens Talent Scholarship Program. We would also like to thank Cornell Center for Materials Research for help with X-ray Diffraction Analysis under NSF award number DMR-0520404, Berhanu Belay and Gebermedihin Ambaw for support in procuring the soil, and Dawit Solomon for help with data interpretation