Seasonal variation of LAI in the footprint of a flux measurement tower

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Modélisation de la réponse des flux de respiration d'un sol forestier selon les principales variables climatiques

Modelling of the response of forest soil respiration fluxes to the main climatic variables. The objective of this article is to model the carbon dioxide (CO2) efflux to the atmosphere due to soil respiration. First, we will synthesize the main components of soil respiration fluxes as found in the literature. Then, we will present a system of automatic measurements, which was set up in a forest stand in Vielsalm (Ardennes, Belgium). This system recorded measurements of soil efflux and of climatic variables every 30 minutes. Its spatial resolution was limited to six collars of 20 cm diameter in a two-meter diameter curve. The measurements were analyzed according to their climatic components: temperature and relative soil water content. We analyzed 2 2 , 9 2 6 cycles of soil respiration measurements, and we followed a strict procedure of data selection in order to characterize soil respiration fluxes according to the main environmental components. We modelized those soil temperature-dependent fluxes with a Q1 0 function and A r r h e n i u s ' law with temperature-adjusted activation energ y, which both gave very similar results. Our best estimation for Q1 0 is 3.86 and for A in Arrhenius ' l a w, 17,479. We then adjusted two line segments beneath and beyond 0 . 2 7 m3.m- 3 of water in the soil in order to describe the response of respiration fluxes to soil moisture content. The soil temperature at 4.5 cm could explain over 86 % of the soil respiration fluxes. Relative moisture content narrows this by 2 %

Chamber-based continuous measurement of N2O fluxes in a winter wheat field: comparison of tillage treatments and identification of emission peak dynamic

Agriculture is the first anthropogenic source of N2O, notably through fertilized croplands. Though, few publications have studied through continuous measurement the N2O emissions in cultivated lands. We conducted this study to assess the effect of farming practices and climate on N2O emissions from a winter wheat crop. The experiment was held in an experimental field in the loamy region in Belgium from March 2016 till crop harvest in August 2016. The N2O fluxes are measured on two nearby parcels in a winter wheat field with restitution of the residues from previous crop. For the past 8 years, one parcel was subjected to a reduced tillage (RT, 10 cm depth) and the other one to a conventional tillage (CT, 25 cm depth). On each parcel, the N2O emissions were assessed with homemade automated closed chambers. Measurement continuity and good temporal resolution (one mean flux every 4 hours) of the system allowed a fine detection and quantification of the emission peaks which usually represent the major part of N2O fluxes. In addition to gas fluxes, soil water content at various depths and surface temperature were measured continuously. Soil samples were taken regularly to determine soil pH, soil organic carbon and nitrogen pools (total, NO3- and NH4+) and study microbial diversity and nitrification/denitrification gene expression. Measurements are still in progress. First results suggested that fluxes were about 3 times larger in the RT parcel than in the CT parcel. Several emissions peaks were observed during the measurement period. The peaks occurred after fertilization events and seemed to be triggered by an elevation of soil water content. A comparison of the emissions between RT and CT and a discussion on peak temporal dynamics, focusing on their intensity, duration and starting time will be presented.AgriGE

Etude des capacités langagières résiduelles chez les patients en état de conscience altérée

Language impairment such as receptive aphasia might lead to an underestimation of the level of consciousness in post-comatose patients (Schnakers et al., 2014). Yet, only a few studies focused on the behavioral assessment of residual language function, as based on the Coma Recovery Scale-Revised (CRS-R) and other tools, in line with their neural correlates. As previously recommended by Majerus et al. (2009), we here combined such behavioral and neuroimaging assessments to better explore language functions in patients with disorders of consciousness. In the Experimental part I, we investigated the neural correlates of the clinical sub-categorization of minimally conscious state (MCS), based on the presence (i.e., MCS+) or absence (i.e., MCS-) of language-related signs of consciousness. As expected, language areas were shown to be more activated in MCS+ compared to MCS-, either using resting state FDG-PET or fMRI. These areas mainly encompassed the left-sided temporal lobule, angular gyrus, inferior/middle frontal cortex, caudate and temporo-occipital fusiform cortex. We also observed increased connectivity in the left frontoparietal network in MCS+ compared to MCS- patients, which was previously associated to language function. This result was particularly consistent across studies, either according to FDG-PET or fMRI measurements. Hence, MCS patients and healthy subjects could be placed along a continuum, from severe left frontoparietal network dysfunction, possibly associated to severely impaired language processing in MCS- patients, to preserved network connectivity in healthy subjects, with MCS+ patients being situated between these two groups. By contrast, increase of grey matter volume as assessed by voxel-based morphometry analyses was not significantly associated to the recovery of command-following, intelligible verbalization and/or intentional communication, unless at the individual-level. Finally, with regard to consciousness areas, a lower impairment of default mode network areas in MCS+ compared to MCS- was only revealed at the single subject-level. The MCS sub-categorization would thus reflect distinct levels of language impairments more than different levels of consciousness The Experimental part II presents new bedside language assessments to complement the CRS-R and neuroimaging examinations. The Cognitive Assessment by Visual Election (CAVE) comprises tasks involving semantic and reading abilities (i.e., recognition of objects, pictures, letters, numbers, written words and colors), whereas the Brief Evaluation of Receptive Aphasia (BERA) is composed of three subscales examining different domains of language: phonology, semantics and morphosyntax. Good psychometric properties (reliability, validity and sensitivity) were shown using the BERA in aphasic conscious patients.The use of both tools in addition to the CRS-R in patients with disorders of consciousness allowed refining their behavioral language profiles, which were in line with FDG-PET and structural MRI results

Consciousness and language in disorders of consciousness after a coma

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