Plant-soil synchrony in nutrient cycles: Learning from ecosystems to design sustainable agrosystems.

Redesigning agrosystems to include more ecological regulations can help feed a growing human population, preserve soils for future productivity, limit dependency on synthetic fertilizers, and reduce agriculture contribution to global changes such as eutrophication and warming. However, guidelines for redesigning cropping systems from natural systems to make them more sustainable remain limited. Synthetizing the knowledge on biogeochemical cycles in natural ecosystems, we outline four ecological systems that synchronize the supply of soluble nutrients by soil biota with the fluctuating nutrient demand of plants. This synchrony limits deficiencies and excesses of soluble nutrients, which usually penalize both production and regulating services of agrosystems such as nutrient retention and soil carbon storage. In the ecological systems outlined, synchrony emerges from plant-soil and plant-plant interactions, eco-physiological processes, soil physicochemical processes, and the dynamics of various nutrient reservoirs, including soil organic matter, soil minerals, atmosphere, and a common market. We discuss the relative importance of these ecological systems in regulating nutrient cycles depending on the pedoclimatic context and on the functional diversity of plants and microbes. We offer ideas about how these systems could be stimulated within agrosystems to improve their sustainability. A review of the latest advances in agronomy shows that some of the practices suggested to promote synchrony (e.g., reduced tillage, rotation with perennial plant cover, crop diversification) have already been tested and shown to be effective in reducing nutrient losses, fertilizer use, and N2 O emissions and/or improving biomass production and soil carbon storage. Our framework also highlights new management strategies and defines the conditions for the success of these nature-based practices allowing for site-specific modifications. This new synthetized knowledge should help practitioners to improve the long-term productivity of agrosystems while reducing the negative impact of agriculture on the environment and the climate.

Systematic Review of the Key Factors Influencing the Indoor Airborne Spread of SARS-CoV-2.

The COVID-19 pandemic due to the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has been plaguing the world since late 2019/early 2020 and has changed the way we function as a society, halting both economic and social activities worldwide. Classrooms, offices, restaurants, public transport, and other enclosed spaces that typically gather large groups of people indoors, and are considered focal points for the spread of the virus. For society to be able to go "back to normal", it is crucial to keep these places open and functioning. An understanding of the transmission modes occurring in these contexts is essential to set up effective infection control strategies. This understanding was made using a systematic review, according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses statement (PRISMA) 2020 guidelines. We analyze the different parameters influencing airborne transmission indoors, the mathematical models proposed to understand it, and discuss how we can act on these parameters. Methods to judge infection risks through the analysis of the indoor air quality are described. Various mitigation measures are listed, and their efficiency, feasibility, and acceptability are ranked by a panel of experts in the field. Thus, effective ventilation procedures controlled by CO2-monitoring, continued mask wearing, and a strategic control of room occupancy, among other measures, are put forth to enable a safe return to these essential places.

Gastric electrical stimulation versus per-oral pyloromyotomy for the treatment of nausea and vomiting associated with gastroparesis: An observational study of two cohorts.

BACKGROUND: Both gastric electrical stimulation (GES) and gastric-peroral endoscopic myotomy (G-POEM) can be offered to patients with gastroparesis and predominant nausea and vomiting. The study's aim was to compare GES and G-POEM efficacy on nausea and vomiting scores in patients with gastroparesis. METHODS: Two multicenter cohorts of patients with medically refractory gastroparesis with predominant nausea and vomiting (defined as a score >2 on nausea and vomiting subscale that varied from 0 to 4) were treated either with GES (n = 34) or G-POEM (n = 30) and were followed for 24 months (M). Clinical response was defined as a decrease of ≥1 point in nausea and vomiting subscale without premature exclusion due to switch from one to the other technique before M24. Changes in symptomatic scales and quality of life were also monitored. KEY RESULTS: Patients from both groups were comparable although the mean score of nausea and vomiting subscale was higher in GES (3.0) compared to G-POEM group (2.6; p = 0.01). At M24, clinical response was achieved in 21/34 (61.7%) patients with GES and in 21/30 (70.0%; p = 0.60) patients with G-POEM. Mean scores of nausea and vomiting subscale decreased at M24 in both GES (from 3.0 to 1.6; p < 0.001) and G-POEM (from 2.6 to 1.2; p < 0.001) groups, although there was no difference between groups (difference adjusted from baseline: -0.28 [-0.77; 0.19]; p = 0.24). Likewise, symptomatic and quality of life scores improved at M24 in both groups, without difference according to treatment group. CONCLUSIONS AND INFERENCES: At M24, we did not observe significant difference in efficacy of GES and G-POEM in medically refractory gastroparesis with predominant nausea and vomiting.

Current controversies on mechanisms controlling soil carbon storage: implications for interactions with practitioners and policy-makers. A review.

There is currently an intense debate about the potential for additional organic carbon storage in soil, the strategies by which it may be accomplished and what the actual benefits might be for agriculture and the climate. Controversy forms an essential part of the scientific process, but on the topic of soil carbon storage, it may confuse the agricultural community and the general public and may delay actions to fight climate change. In an attempt to shed light on this topic, the originality of this article lies in its intention to provide a balanced description of contradictory scientific opinions on soil carbon storage and to examine how the scientific community can support decision-making despite the controversy. In the first part, we review and attempt to reconcile conflicting views on the mechanisms controlling organic carbon dynamics in soil. We discuss the divergent opinions about chemical recalcitrance, the microbial or plant origin of persistent soil organic matter, the contribution of particulate organic matter to additional organic carbon storage in soil, and the spatial and energetic inaccessibility of soil organic matter to decomposers. In the second part, we examine the advantages and limitations of big data management and modeling, which are essential tools to link the latest scientific theories with the actions taken by stakeholders. Finally, we show how the analysis and discussion of controversies can guide scientists in supporting stakeholders for the design of (i) appropriate trade-offs for biomass use in agriculture and forestry and (ii) climate-smart management practices, keeping in mind their still unresolved effects on soil carbon storage.

Bioenergetic control of soil carbon dynamics across depth.

Soil carbon dynamics is strongly controlled by depth globally, with increasingly slow dynamics found at depth. The mechanistic basis remains however controversial, limiting our ability to predict carbon cycle-climate feedbacks. Here we combine radiocarbon and thermal analyses with long-term incubations in absence/presence of continuously 13C/14C-labelled plants to show that bioenergetic constraints of decomposers consistently drive the depth-dependency of soil carbon dynamics over a range of mineral reactivity contexts. The slow dynamics of subsoil carbon is tightly related to both its low energy density and high activation energy of decomposition, leading to an unfavourable 'return-on-energy-investment' for decomposers. We also observe strong acceleration of millennia-old subsoil carbon decomposition induced by roots ('rhizosphere priming'), showing that sufficient supply of energy by roots is able to alleviate the strong energy limitation of decomposition. These findings demonstrate that subsoil carbon persistence results from its poor energy quality together with the lack of energy supply by roots due to their low density at depth.

Compliance with Barrier Gestures during COVID-19 Pandemic as a Function of the Context: A Longitudinal Observational Survey at the University of Liège.

During the COVID-19 pandemic, barrier gestures such as mask wearing, physical distancing, greetings without contact, one-way circulation flow, and hand sanitization were major strategies to prevent the spread of SARS-CoV-2, but they were only useful if consistently applied. This survey was a follow-up of the first survey performed in 2020 at the University of Liège. We aim to evaluate the compliance with these gestures on campuses and examine differences in the extent of the compliance observed in different educational activities and contexts. During 3.5 months, the counting of compliant and non-compliant behaviors was performed each week in randomly selected rooms. Using data collected during both surveys (2020 and 2021), binomial negative regression models of compliance depending on periods (teaching periods and exam sessions), type of rooms, and campuses were conducted to evaluate prevalence ratios of compliance. The percentage of compliance in this second survey was the highest for mask wearing and physical distancing during educational activities (90% and 88%, respectively) and lowest for physical distancing outside educational activities and hand sanitization (45% and 52%, respectively). Multivariate analyses revealed that the compliance with most gestures was significantly higher in teaching rooms than in hallways and restaurants and during exam sessions. The compliance with physical distancing was significantly higher (from 66%) in auditoriums, where students had to remain seated, than during practical works that allowed or required free movement. Therefore, the compliance with barrier gestures was associated with contextual settings, which should be considered when communicating and managing barrier gestures. Further studies should specify and confirm the determining contextual characteristics regarding the compliance with barrier gestures in times of pandemic.

Decision-based interactive model to determine re-opening conditions of a large university campus in Belgium during the first COVID-19 wave.

BACKGROUND: The role played by large-scale repetitive SARS-CoV-2 screening programs within university populations interacting continuously with an urban environment, is unknown. Our objective was to develop a model capable of predicting the dispersion of viral contamination among university populations dividing their time between social and academic environments. METHODS: Data was collected through real, large-scale testing developed at the University of Liège, Belgium, during the period Sept. 28th-Oct. 29th 2020. The screening, offered to students and staff (n = 30,000), began 2 weeks after the re-opening of the campus but had to be halted after 5 weeks due to an imposed general lockdown. The data was then used to feed a two-population model (University + surrounding environment) implementing a generalized susceptible-exposed-infected-removed compartmental modeling framework. RESULTS: The considered two-population model was sufficiently versatile to capture the known dynamics of the pandemic. The reproduction number was estimated to be significantly larger on campus than in the urban population, with a net difference of 0.5 in the most severe conditions. The low adhesion rate for screening (22.6% on average) and the large reproduction number meant the pandemic could not be contained. However, the weekly screening could have prevented 1393 cases (i.e. 4.6% of the university population; 95% CI: 4.4-4.8%) compared to a modeled situation without testing. CONCLUSION: In a real life setting in a University campus, periodic screening could contribute to limiting the SARS-CoV-2 pandemic cycle but is highly dependent on its environment.

Determinants of diaphragm inspiratory motion, diaphragm thickening, and its performance for predicting respiratory restrictive pattern in Duchenne muscular dystrophy.

INTRODUCTION/AIMS: Respiratory status is a key determinant of prognosis in patients with Duchenne muscular dystrophy (DMD). We aimed to evaluate the determinants of diaphragm ultrasound and its performance in predicting restrictive respiratory patterns in DMD. METHODS: This was a retrospective study of DMD patients followed in our center and admitted for an annual checkup from 2015 to 2018. We included DMD patients who underwent diaphragm ultrasound and pulmonary functional tests. RESULTS: This study included 74 patients with DMD. The right diaphragm thickening fraction (TF) was significantly associated with age (P = .001), Walton score (P = .012), inspiratory capacity (IC) (P = .004), upright forced vital capacity (FVC) (P < .0001), supine FVC (P = .038), and maximal inspiratory pressure (MIP) (P = .002). Right diaphragm excursion was significantly associated with age (P < .0001), steroid use (P = .008), history of spinal fusion (P < .0001), body mass index (BMI) (P = .002), Walton score (P < .0001), IC (P < .0001), upright FVC (P < .0001), supine FVC (P < .0001), and MIP (P < .0001). A right diaphragm TF >28% and a right diaphragm excursion>25.4 mm were associated with an FVC >50% with, respectively, an area under the curve (AUC) of 0.95 (P = .001) and 0.93 (P < .001). A left diaphragm TF >26.8% and a left diaphragm excursion >21.5 mm were associated with an FVC >50% with, respectively, an AUC of 0.95 (P = .011) and 0.97 (P < .001). DISCUSSION: Diaphragm excursion and diaphragm TF can predict restrictive pulmonary insufficiency in DMD.

Main determinants of the acceptance of COVID-19 control measures by the population: A first pilot survey at the University of Liege, Belgium.

BACKGROUND: In order to control the COVID-19 pandemic, barrier gestures were used to reduce the transmission of the virus within a community and avoid large peaks of infections with the risk of overwhelming the healthcare systems. The acceptability of these measures is the backbone of their successful implementation. However, population compliance with these measures within a community is uncertain, even when mandatory. At the beginning of the 2020-2021 academic year, the University of Liege complemented these measures, by organizing a weekly screening by saliva testing on a voluntary basis for all its workers and students. Their compliance with the different measures was necessary for effective control program and an intensive communication plan was implemented throughout the 2020-2021 academic year for that purpose METHOD AND PRINCIPAL FINDINGS: An online survey was launched upon the implementation of the saliva testing in order (i) to assess the level of acceptance of the different measures by the university workers and students and (ii) to identify the factors determining their acceptance (based on the Health Belief Model) and their reported level of implementation. A total of 921 responses was received and analysed by sub-group comparison, structural equation modelling and multivariable ordinal logistic regression. Health motivation, susceptibility, severity and perception of benefits were identified as the key determinants of protective measures acceptance CONCLUSION AND SIGNIFICANCE: In order to influence positively these mental constructs and to increase the level of implementation of control measures, it is therefore recommended to raise the awareness of the university workers and students about their self and collective responsibility to protect themselves and the population at risk that can be severely affected by the disease. The non-medical faculties (i.e. the Faculty of Medicine and the Faculty of Veterinary Medicine excluded) should be specifically targeted as their heath motivation was significantly lower. This survey demonstrates that the risk mitigation strategies against COVID-19 should integrate the importance of individual perception. The methodology developed in this survey can be generalised in space and time, in different contexts.

The First Random Observational Survey of Barrier Gestures against COVID-19.

In the context of COVID-19 in Belgium, face-to-face teaching activities were allowed in Belgian universities at the beginning of the 2020-2021 academic year. Nevertheless, several control measures were established to control COVID-19 transmission on the campuses. To ensure compliance with these measures, a random observational survey, based on five barrier gestures, was implemented at the University of Liege (greetings without contact, hand sanitisation, following a one-way traffic flow, wearing a mask and physical distancing). Each barrier gesture was weighted, based on experts' elicitation, and a scoring system was developed. The results were presented as a diagram (to identify the margin of improvement for each barrier gesture) and a risk management barometer. In total, 526 h of observations were performed. The study revealed that some possible improvements could be made in the management of facilities, in terms of room allocation, the functionality of hydro-alcoholic gel dispensers, floor markings and one-way traffic flow. Compliance with the barrier gestures reached an overall weighted score of 68.2 (between 0 and 100). Three barrier gestures presented a lower implementation rate and should be addressed: the use of hydro-alcoholic gel (particularly when exiting buildings), compliance with the traffic flow and the maintenance of a 1.5 m physical distance outside of the auditoriums. The methodology and tool developed in the present study can easily be applied to other settings. They were proven to be useful in managing COVID-19, as the barometer that was developed and the outcomes of this survey enabled an improved risk assessment on campuses, and identified the critical points to be addressed in any further public health communication or education messages.

Factors Determining the Implementation of Measures Aimed at Preventing Zoonotic Diseases in Veterinary Practices.

BACKGROUND: Zoonoses prevention relies mainly on the implementation of different biosecurity measures. This study aimed to assess the level of implementation of biosecurity measures by veterinary practitioners and students and to identify the possible behaviour change determinants. METHODS: The data was collected through a cross-sectional survey (N = 382). Statistical analyses were implemented based on the Health Belief Model to identify the possible determinant of the behaviours and the explanatory variables of the perceptions. RESULTS: The survey showed a good level of implementation of the biosecurity measures (median of 81%). The implementation was associated with a higher perception of the zoonoses' susceptibility and the measures' benefits, and with a lower perception of the zoonoses' severity. The study also revealed that the decision to implement a measure was mainly taken on a case-by-case basis depending on the perceived risk of exposure related to a specific context or intervention. CONCLUSION: The main determining factors identified for the implementation of biosecurity measures (BSMs) were the risk susceptibility and the benefits of the biosecurity measures, which could be influenced by evidence-based communication. The methodology developed can be applied regularly and in other countries to better capture these changes in perceptions over time.

Rhizosphere control of soil nitrogen cycling: a key component of plant economic strategies.

Understanding how plant species influence soil nutrient cycling is a major theme in terrestrial ecosystem ecology. However, the prevailing paradigm has mostly focused on litter decomposition, while rhizosphere effects on soil organic matter (SOM) decomposition have attracted little attention. Using a dual 13 C/15 N labeling approach in a 'common garden' glasshouse experiment, we investigated how the economic strategies of 12 grassland plant species (graminoids, forbs and legumes) drive soil nitrogen (N) cycling via rhizosphere processes, and how this in turn affects plant N acquisition and growth. Acquisitive species with higher photosynthesis, carbon rhizodeposition and N uptake than conservative species induced a stronger acceleration of soil N cycling through rhizosphere priming of SOM decomposition. This allowed them to take up larger amounts of N and allocate it above ground to promote photosynthesis, thereby sustaining their faster growth. The N2 -fixation ability of legumes enhanced rhizosphere priming by promoting photosynthesis and rhizodeposition. Our study demonstrates that the economic strategies of plant species regulate a plant-soil carbon-nitrogen feedback operating through the rhizosphere. These findings provide novel mechanistic insights into how plant species with contrasting economic strategies sustain their nutrition and growth through regulating the cycling of nutrients by soil microbes in their rhizosphere.

Succinate detection using in vivo 1H-MR spectroscopy identifies germline and somatic SDHx mutations in paragangliomas.

PURPOSE: Germline mutations in genes encoding succinate dehydrogenase (SDH) are frequent in patients with pheochromocytoma and paraganglioma (PPGL). They lead to SDH inactivation, mediating a massive accumulation of succinate, which constitutes a highly specific biomarker of SDHx-mutated tumors when measured in vitro. In a recent pilot study, we showed that magnetic resonance spectroscopy (1H-MRS) optimized for succinate detection (SUCCES) could detect succinate in vivo in both allografted mouse models and PPGL patients. The objective of this study was to prospectively assess the diagnostic performances of 1H-MRS SUCCES sequence for the identification of SDH deficiency in PPGL patients. METHODS: Forty-nine patients presenting with 50 PPGLs were prospectively enrolled in our referral center for 1H-MRS SUCCES. Two observers blinded to the clinical characteristics and genetic status analyzed the presence of a succinate peak and confronted the results to a composite gold standard combining PPGL genetic testing and/or in vitro protein analyses in the tumor. RESULTS: A succinate peak was observed in 20 tumors, all of which had proven SDH deficiency using the gold standard (17 patients with germline SDHx mutations, 2 with a somatic SDHD mutation, and 1 with negative SDHB IHC and SDH loss of function). A false negative result was observed in 3 tumors. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 1H-MRS SUCCES were respectively 87%, 100%, 100%, 90%, and 94%. CONCLUSIONS: Detection of succinate using 1H-MRS is a highly specific and sensitive hallmark of SDH-deficiency in PPGLs.

Gastric Electrical Stimulation Reduces Refractory Vomiting in a Randomized Crossover Trial.

BACKGROUND & AIMS: There have been conflicting results from trials of gastric electrical stimulation (GES) for treatment of refractory vomiting, associated or not with gastroparesis. We performed a large, multicenter, randomized, double-blind trial with crossover to study the efficacy of GES in patients with refractory vomiting, with or without gastroparesis. METHODS: For 4 months, we assessed symptoms in 172 patients (66% women; mean age ± standard deviation, 45 ± 12 years; 133 with gastroparesis) with chronic (>12 months) of refractory vomiting (idiopathic, associated with a type 1 or 2 diabetes, or postsurgical). A GES device was implanted and left unactivated until patients were randomly assigned, in a double-blind manner, to groups that received 4 months of stimulation parameters (14 Hz, 5 mA, pulses of 330 µs) or no stimulation (control); 149 patients then crossed over to the other group for 4 months. Patients were examined at the end of each 4-month period (at 5 and 9 months after implantation). Primary endpoints were vomiting score, ranging from 0 (daily vomiting) to 4 (no vomiting), and the quality of life, assessed by the Gastrointestinal Quality of Life Index scoring system. Secondary endpoints were changes in other digestive symptoms, nutritional status, gastric emptying, and control of diabetes. RESULTS: During both phases of the crossover study, vomiting scores were higher in the group with the device on (median score, 2) than the control group (median score, 1; P < .001), in diabetic and nondiabetic patients. Vomiting scores increased significantly when the device was ON in patients with delayed (P < .01) or normal gastric emptying (P = .05). Gastric emptying was not accelerated during the ON period compared with the OFF period. Having the GES turned on was not associated with increased quality of life. CONCLUSIONS: In a randomized crossover study, we found that GES reduced the frequency of refractory vomiting in patients with and without diabetes, although it did not accelerate gastric emptying or increase of quality of life. Clinicaltrials.gov, Number: NCT00903799.

Diagnostic and Therapeutic Uptake of Intrathyroid Metastasis of Midgut Neuroendocrine Tumor on 68Ga-DOTANOC PET/CT and 177Lu-DOTATATE Imaging.

A 58-year-old woman with 5-year history of grade 1 progressive metastatic intestinal neuroendocrine tumor with metachronous liver metastases initially treated by surgery and liver embolization underwent Ga-DOTANOC PET/CT before Lu-DOTATATE therapy. Ga-DOTANOC PET/CT revealed increased uptake in several liver metastases and right iliac lymph nodes, consistent with radiopeptide therapy, including a hypodense isthmic thyroid nodule. Fine needle ultrasound-guided biopsy of the thyroid nodule was realized. Immunohistochemistry was positive for CD56, chromogranin, and synaptophysin and negative for calcitonin, confirming neuroendocrine tumor intrathyroid metastasis. Lu-DOTATATE SPECT/CT showed therapeutic uptake on the thyroid metastasis.

Peroral endoscopic pyloromyotomy is efficacious and safe for refractory gastroparesis: prospective trial with assessment of pyloric function.

BACKGROUND: Gastroparesis is a functional disorder with a variety of symptoms that is characterized by delayed gastric emptying in the absence of mechanical obstruction. A recent series of retrospective studies has demonstrated that peroral endoscopic pyloromyotomy (G-POEM) is a promising endoscopic procedure for treating patients with refractory gastroparesis. The aim of this prospective study was to evaluate the feasibility, safety, and efficacy of G-POEM. METHODS: 20 patients with refractory gastroparesis (10 diabetic and 10 nondiabetic) were prospectively included in the trial. Patients were treated by G-POEM after evaluation of pyloric function using an endoscopic functional luminal imaging probe. Clinical responses were evaluated using the Gastroparesis Cardinal Symptom Index (GCSI), and quality of life was assessed using the Patient Assessment of Upper Gastrointestinal Disorders - Quality of Life scale and the Gastrointestinal Quality of Life Index scores. Gastric emptying was measured using 4-hour scintigraphy before G-POEM and at 3 months. RESULTS: Feasibility of the procedure was 100 %. Compared with baseline values, G-POEM significantly improved symptoms (GCSI: 1.3 vs. 3.5; P < 0.001), quality of life, and gastric emptying (T½: 100 vs. 345 minutes, P < 0.001; %H2: 56.0 % vs. 81.5 %, P < 0.001; %H4: 15.0 % vs. 57.5 %, P = 0.003) at 3 months. The clinical success of G-POEM using the functional imaging probe inflated to 50 mL had specificity of 100 % and sensitivity of 72.2 % (P = 0.04; 95 % confidence interval 0.51 - 0.94; area under the curve 0.72) at a distensibility threshold of 9.2 mm2/mmHg. CONCLUSION: G-POEM was efficacious and safe for treating refractory gastroparesis, especially in patients with low pyloric distensibility.

Incidental Finding of Intrathyroid Metastases of Prostatic Cancer on 18F-Choline PET/CT.

An 85-year-old man with a 2-year history of prostate cancer, treated with radiotherapy and hormonal therapy, presented increased prostatic-specific antigen levels. F-choline PET/CT showed focal prostatic uptake consistent with known local recurrence, increased uptake of 2 hypodense thyroid nodules and of 2 left cervical lymph nodes, suspected as thyroid cancer. Neck ultrasound confirmed the high risk of malignancy, and a guided biopsy (of a thyroid nodule and cervical lymph node) revealed cellular infiltrates thyroid transcription factor-1 (TTF-1) negative and prostatic-specific antigen positive, confirming intrathyroid and cervical lymph node metastases of prostate cancer. PET/CT changed the disease staging. Chemotherapy was initiated.

Soil evaporation and organic matter turnover in the Sub-Taiga and Forest-Steppe of southwest Siberia.

Southwest Siberia encompasses the forest-steppe and sub-taiga climatic zones and has historically been utilized for agriculture. Coinciding with predicted changes in climate for the region is the pressure of agricultural development; however, a characterization of the soil water and carbon dynamics is lacking. We assessed current soil water properties and soil organic carbon turnover in forests and grasslands for two sites that span the forest steppe and sub-taiga bioclimatic zones. Soil evaporation was 0.62 ± 0.17 mm d-1 (mean ± standard error) in grasslands and 0.45 ± 0.08 mm d-1 in the forests of the forest-steppe site. Evaporation at the sub-taiga site was 1.80 ± 1.70 mm d-1 in grasslands and 0.96 ± 0.05 mm d-1 in forest plots. Evaporation was significantly greater at the sub-taiga site than the forest-steppe site. The density of fine roots explained the soil water isotopic patterns between vegetation types and sites. We found soil organic matter turnover to be three times faster in the sub-taiga site than in the forest-steppe site. Our results show that while climate factors, in particular snow levels, between the two sites are drivers for water and carbon cycles, site level hydrology, soil characteristics, and vegetation directly interact to influence the water and carbon dynamics.

Catalytic power of enzymes decreases with temperature: New insights for understanding soil C cycling and microbial ecology under warming.

Most current models of soil C dynamics predict that climate warming will accelerate soil C mineralization, resulting in a long-term CO2 release and positive feedback to global warming. However, ecosystem warming experiments show that CO2 loss from warmed soils declines to control levels within a few years. Here, we explore the temperature dependence of enzymatic conversion of polymerized soil organic C (SOC) into assimilable compounds, which is presumed the rate-limiting step of SOC mineralization. Combining literature review, modelling and enzyme assays, we studied the effect of temperature on activity of enzymes considering their thermal inactivation and catalytic activity. We defined the catalytic power of enzymes (Epower ) as the cumulative amount of degraded substrate by one unit of enzyme until its complete inactivation. We show a universal pattern of enzyme's thermodynamic properties: activation energy of catalytic activity (EAcat ) < activation energy of thermal inactivation (EAinact ). By investing in stable enzymes (high EAinact ) having high catalytic activity (low EAcat ), microorganisms may maximize the Epower of their enzymes. The counterpart of such EAs' hierarchical pattern is the higher relative temperature sensitivity of enzyme inactivation than catalysis, resulting in a reduction in Epower under warming. Our findings could explain the decrease with temperature in soil enzyme pools, microbial biomass (MB) and carbon use efficiency (CUE) reported in some warming experiments and studies monitoring the seasonal variation in soil enzymes. They also suggest that a decrease in soil enzyme pools due to their faster inactivation under warming contributes to the observed attenuation of warming effect on soil C mineralization. This testable theory predicts that the ultimate response of SOC degradation to warming can be positive or negative depending on the relative temperature response of Epower and microbial production of enzymes.