Study of vegetation-atmosphere interactions over vineyards: CO2 fluxes and turbulent transport mechanics

The study of vegetation‒atmosphere exchanges is today of great interest in order to understand and model plant responses to environmental conditions and their potential influence on global climate change. A special attention is usually given to carbon dioxide (CO2) fluxes and, in general, natural ecosystems such as forests received more attention. In the present work we investigated vegetation‒atmosphere interactions over vineyards, focusing on the annual carbon budget and turbulent transport processes driving exchanges of mass and energy. Vineyard is a complex ecosystem with distributed sources/sinks of scalars (water vapour, carbon dioxide, heat), where vines and soil surface combine to give the overall flux of the canopy. In Northern Italy vineyard inter-row is often grassed, playing then an important role in the whole carbon budget. In this context, the partitioning of net ecosystem CO2 exchange (NEE) into soil and vine components deserves a special attention. We monitored vineyard NEE applying the eddy covariance (EC) method for three years, while soil CO2 flux measurements have been carried on using soil chambers (transparent and dark). In 2015, the annual carbon budget of the vineyard was about ‒ 80 g C m‒2 y‒1, however the largest part of carbon assimilation was due to grassed soil compartment (‒ 60 g C m‒2 y‒1). The interannual variability of seasonal carbon budget showed to be high and significantly affected by heat waves and drought spells in summer. During the growing season of 2014, characterized by plenty of rainfall, NEE reached its maximum value of about ‒ 250 g C m‒2. The organization in rows of the vineyard determines a peculiar turbulent transport dynamics within the canopy. However, the morphological structure of the vineyard is greatly variable over the year, shifting from an empty canopy during vine dormancy to dense foliage in summer. We investigated the influence of foliage development on turbulence statistics deploying a vertical array of sonic anemometers. Turbulent flow showed to be greatly influenced by canopy structure. Without leaves, turbulent regime is typical of a rough‒wall boundary layer flow, whereas at full foliage development it assumes the features of a mixing‒layer flow, even if the inflection point at canopy top is weak, due to sparseness of the vineyard. Coherent structures involved in momentum transport and their temporal scales have been also investigated, showing the increasing importance of sweeps throughout the growing season. The average duration of dominating coherent structures was in the order of 6 ‒ 10 s and no clear influence by canopy structure evolution was detected. The research demonstrated the importance of long‒term monitoring of vegetation‒atmosphere exchanges, and also the complexity of turbulent transport dynamics in the canopy space. However, only a thorough comprehension of this mechanics could lead to a solid interpretation of the role of vegetation in fundamental biogeochemical cycles

Correlation Analysis of Evapotranspiration, Emissivity Contrast and Water Deficit Indices: A Case Study in Four Eddy Covariance Sites in Italy with Different Environmental Habitats

Evapotranspiration (ET) represents one of the essential processes controlling the exchange of energy by terrestrial vegetation, providing a strong connection between energy and water fluxes. Different methodologies have been developed in order to measure it at different spatial scales, ranging from individual plants to an entire watershed. In the last few years, several methods and approaches based on remotely sensed data have been developed over different ecosystems for the estimation of ET. In the present work, we outline the correlation between ET measured at four eddy covariance (EC) sites in Italy (situated either in forest or in grassland ecosystems) and (1) the emissivity contrast index (ECI) based on emissivity data from thermal infrared spectral channels of the MODIS and ASTER satellite sensors (CAMEL data-set); (2) the water deficit index (WDI), defined as the difference between the surface and dew point temperature modeled by the ECMWF (European Centre for Medium-Range Weather Forecasts) data. The analysis covers a time-series of 1 to 7 years depending on the site. The results showed that both the ECI and WDI correlate to the ET calculated through EC. In the relationship WDI-ET, the coefficient of determination ranges, depending on the study area, between 0.5 and 0.9, whereas it ranges between 0.5 and 0.7 when ET was correlated to the ECI. The slope and the sign of the latter relationship is influenced by the vegetation habitat, the snow cover (particularly in winter months) and the environmental heterogeneity of the area (calculated in this study through the concept of the spectral variation hypothesis using Rao’s Q heterogeneity index)

LIFE15 ENV/IT/000392 − LIFE VITISOM Project, viticulture innovation technology and GHG emission monitoring

The main aim of the LIFE VITISOM Project is to promote an innovative solution for the management of the organic fertilisation in the viticultural sector. In parallel, different activities of monitoring of impacts have been planned. Specifically, a deep study about GHG emissions has been organised. In this context, different studies are being carried out: a continuous monitoring of net carbon fluxes (NEE) through the Eddy Covariance method, followed by University of Padua which allows data to be obtained at vineyard ecosystem level; a spatial monitoring of CH4, N2O and CO2, through a mobile instrument for measuring the variation of GHG developed by West Systems within the LIFE+ IPNOA Project. In the first case, two Eddy Covariance towers have been installed, one at Guido Berlucchi (Franciacorta, Lombardy) and one at Bosco del Merlo (Lison, Veneto). Additionally, spatial monitoring is being carried out in five testing sites involved in the LIFE VITISOM project. In this case, different organic fertilisation managements are compared

Altered energy partitioning across terrestrial ecosystems in the European drought year 2018

Drought and heat events, such as the 2018 European drought, interact with the exchange of energy between the land surface and the atmosphere, potentially affecting albedo, sensible and latent heat fluxes, as well as CO(2)exchange. Each of these quantities may aggravate or mitigate the drought, heat, their side effects on productivity, water scarcity and global warming. We used measurements of 56 eddy covariance sites across Europe to examine the response of fluxes to extreme drought prevailing most of the year 2018 and how the response differed across various ecosystem types (forests, grasslands, croplands and peatlands). Each component of the surface radiation and energy balance observed in 2018 was compared to available data per site during a reference period 2004-2017. Based on anomalies in precipitation and reference evapotranspiration, we classified 46 sites as drought affected. These received on average 9% more solar radiation and released 32% more sensible heat to the atmosphere compared to the mean of the reference period. In general, drought decreased net CO(2)uptake by 17.8%, but did not significantly change net evapotranspiration. The response of these fluxes differed characteristically between ecosystems; in particular, the general increase in the evaporative index was strongest in peatlands and weakest in croplands. This article is part of the theme issue 'Impacts of the 2018 severe drought and heatwave in Europe: from site to continental scale'

Rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART): Study protocol for a randomized controlled trial

Background: Acute respiratory distress syndrome (ARDS) is associated with high in-hospital mortality. Alveolar recruitment followed by ventilation at optimal titrated PEEP may reduce ventilator-induced lung injury and improve oxygenation in patients with ARDS, but the effects on mortality and other clinical outcomes remain unknown. This article reports the rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART). Methods/Design: ART is a pragmatic, multicenter, randomized (concealed), controlled trial, which aims to determine if maximum stepwise alveolar recruitment associated with PEEP titration is able to increase 28-day survival in patients with ARDS compared to conventional treatment (ARDSNet strategy). We will enroll adult patients with ARDS of less than 72 h duration. The intervention group will receive an alveolar recruitment maneuver, with stepwise increases of PEEP achieving 45 cmH(2)O and peak pressure of 60 cmH2O, followed by ventilation with optimal PEEP titrated according to the static compliance of the respiratory system. In the control group, mechanical ventilation will follow a conventional protocol (ARDSNet). In both groups, we will use controlled volume mode with low tidal volumes (4 to 6 mL/kg of predicted body weight) and targeting plateau pressure <= 30 cmH2O. The primary outcome is 28-day survival, and the secondary outcomes are: length of ICU stay; length of hospital stay; pneumothorax requiring chest tube during first 7 days; barotrauma during first 7 days; mechanical ventilation-free days from days 1 to 28; ICU, in-hospital, and 6-month survival. ART is an event-guided trial planned to last until 520 events (deaths within 28 days) are observed. These events allow detection of a hazard ratio of 0.75, with 90% power and two-tailed type I error of 5%. All analysis will follow the intention-to-treat principle. Discussion: If the ART strategy with maximum recruitment and PEEP titration improves 28-day survival, this will represent a notable advance to the care of ARDS patients. Conversely, if the ART strategy is similar or inferior to the current evidence-based strategy (ARDSNet), this should also change current practice as many institutions routinely employ recruitment maneuvers and set PEEP levels according to some titration method.Hospital do Coracao (HCor) as part of the Program 'Hospitais de Excelencia a Servico do SUS (PROADI-SUS)'Brazilian Ministry of Healt

Study of vegetation-atmosphere interactions over vineyards: CO2 fluxes and turbulent transport mechanics

The study of vegetation‒atmosphere exchanges is today of great interest in order to understand and model plant responses to environmental conditions and their potential influence on global climate change. A special attention is usually given to carbon dioxide (CO2) fluxes and, in general, natural ecosystems such as forests received more attention. In the present work we investigated vegetation‒atmosphere interactions over vineyards, focusing on the annual carbon budget and turbulent transport processes driving exchanges of mass and energy. Vineyard is a complex ecosystem with distributed sources/sinks of scalars (water vapour, carbon dioxide, heat), where vines and soil surface combine to give the overall flux of the canopy. In Northern Italy vineyard inter-row is often grassed, playing then an important role in the whole carbon budget. In this context, the partitioning of net ecosystem CO2 exchange (NEE) into soil and vine components deserves a special attention. We monitored vineyard NEE applying the eddy covariance (EC) method for three years, while soil CO2 flux measurements have been carried on using soil chambers (transparent and dark). In 2015, the annual carbon budget of the vineyard was about ‒ 80 g C m‒2 y‒1, however the largest part of carbon assimilation was due to grassed soil compartment (‒ 60 g C m‒2 y‒1). The interannual variability of seasonal carbon budget showed to be high and significantly affected by heat waves and drought spells in summer. During the growing season of 2014, characterized by plenty of rainfall, NEE reached its maximum value of about ‒ 250 g C m‒2. The organization in rows of the vineyard determines a peculiar turbulent transport dynamics within the canopy. However, the morphological structure of the vineyard is greatly variable over the year, shifting from an empty canopy during vine dormancy to dense foliage in summer. We investigated the influence of foliage development on turbulence statistics deploying a vertical array of sonic anemometers. Turbulent flow showed to be greatly influenced by canopy structure. Without leaves, turbulent regime is typical of a rough‒wall boundary layer flow, whereas at full foliage development it assumes the features of a mixing‒layer flow, even if the inflection point at canopy top is weak, due to sparseness of the vineyard. Coherent structures involved in momentum transport and their temporal scales have been also investigated, showing the increasing importance of sweeps throughout the growing season. The average duration of dominating coherent structures was in the order of 6 ‒ 10 s and no clear influence by canopy structure evolution was detected. The research demonstrated the importance of long‒term monitoring of vegetation‒atmosphere exchanges, and also the complexity of turbulent transport dynamics in the canopy space. However, only a thorough comprehension of this mechanics could lead to a solid interpretation of the role of vegetation in fundamental biogeochemical cycles.Lo studio delle interazioni tra vegetazione e atmosfera è oggi un tema di grande interesse nell’ottica di migliorare la comprensione della risposta delle piante alle variabili ambientali e la modellizzazione del loro ruolo nel cambiamento climatico globale. Particolare attenzione è di solito rivolta ai flussi di anidride carbonica (CO2) e, in genere, gli ecosistemi naturali come le foreste hanno ricevuto una maggiore attenzione. In questa ricerca sono state studiate le interazioni vegetatione-atmosfera su una coltura agraria importante per il bacino mediterraneo, quale il vigneto, focalizzandosi sul monitoraggio del bilancio annuale di carbonio e approfondendo lo studio della meccanica del trasporto turbulento che è alla base degli scambi di energia e materia. Il vigneto è un sistema complesso con diverse sorgenti e sink di scalari (vapore d’acqua, anidride carbonica, calore), in cui le due principali componenti, vite e suolo, compongono il flusso totale della canopy in un rapporto che varia nel corso dell’anno. Nei vigneti del Nord Italia, l’interfila è solitamente non lavorata e inerbita, giocando un ruolo importante nel bilancio del carbonio del sistema. In questo contesto, risulta cruciale la ripartizione dello scambio netto di CO2 dell’ecosistema (Net Ecosystem Exchange, NEE) nelle componenti suolo e vite. Nel corso di questa indagine, la NEE di un vigneto è stata monitorata per tre anni utilizzando la tecnica micrometeorologica dell’ eddy covariance (EC), mentre la misura dei flussi di CO2 al suolo è stata effettuata con camere (a cupola trasparente e oscura). Nel 2015, il bilancio annuale di carbonio del vigneto è stato di circa ‒ 80 g C m‒ 2 a‒ 1, dimostrando quindi la capacità di agire da sink, ma la maggior parte dell’assimilazione è risultata legata al suolo inerbito (‒ 60 g C m‒2 a‒1). In ogni caso, il sistema ha dimostrato un’elevata variabilità interannuale del bilancio del carbonio stagionale, in cui ondate di calore e periodi di siccità estivi hanno giocato un ruolo primario. Nella stagione 2014, caratterizzata da un regime di precipitazione abbondante, la NEE ha raggiunto il valore massimo di circa ‒ 250 g C m‒2. L’organizzazione del vigneto in filari determina una particolare dinamica del trasporto turbolento dentro canopy. Inoltre, la struttura morfologica del vigneto è altamente variabile durante il corso dell’anno, passando da una canopy praticamente vuota nel periodo di dormienza della vite a una situazione dove il fogliame è denso e concentrato nelle file al culmine della stagione vegetativa. L’influenza dello sviluppo della densità fogliare sulle statistiche della turbolenza è stato studiato installando un profilo verticale di anemometri ad ultrasuoni. Il flusso turbolento è risultato fortemente influenzato dalla struttura della canopy. Senza foglie, il regime turbolento è caratteristico di un flusso di parete, mentre con lo sviluppo completo del fogliame assume le proprietà tipiche di un flusso con mixing‒layer, sebbene il flesso al limite superiore della canopy sia poco accentuato, a causa della bassa densità fogliare del vigneto. Infine, è stata condotta un’analisi specifica delle strutture coerenti coinvolte nel trasporto di quantità di moto e sulle loro scale temporali. L’importanza di eventi discendenti che trasportano aria più veloce del flusso medio (sweeps) è aumentata nel corso della stagione. La durata media delle strutture coerenti dominanti è stato nell’ordine di 6 ‒ 10 s e, in questo caso, non è stata riscontrata nessuna chiara correlazione con lo sviluppo della struttura della canopy. Lo studio ha messo in evidenza l’importanza del monitoraggio a lungo termine degli scambi tra vegetazione e atmosfera, ma anche la complessità dei fenomeni di trasporto turbolento che li caratterizzano. Tuttavia, solo la piena comprensione della meccanica di questi processi può portare alla corretta interpretazione del ruolo della vegetazione nei cicli biogeochimici più fondamentali

Evolution of turbulent flow characteristics in a hedgerow vineyard during the growing season

The characteristics of turbulent flow at the land-atmosphere interface and within plant canopies are strongly modified by the interactions with vegetation elements. However, only few experimental studies were conducted so far on the effect of changing leaf area on within-canopy turbulence statistics. This aspect is important for deciduous forests and perennial woody crops (orchards and vineyards), where the variation of leaf area is recurrent and substantial during the growing season. Increasing the understanding on canopy turbulence is fundamental to improve the parameterization of multi-layer models to predict vegetation-atmosphere exchanges. In this context, we conducted an experimental campaign in a hedgerow vineyard in North-East Italy carrying out measurements with a vertical array of 3D sonic anemometers, together with canopy structure characterization, in order to analyze the evolution of turbulent flow characteristics from a leafless canopy to full development. Additionally, the effects of wind direction with respect to rows and of atmospheric stability were analyzed. We found that the aerodynamic properties of the vineyard were not only influenced by canopy height and total leaf area, but also by the vertical distribution of leaf density, with the thickness of the mid-upper layer playing a major role in determining the canopy roughness and the mean level of momentum absorption. The characteristics of within-canopy turbulent flow became more similar to a well-defined mixing-layer type flow as foliage developed, but only for diagonal and across-row wind. In contrast, with wind parallel to rows the effect of increasing leaf density was lower and the vineyard was more similar to an open canopy. The influence of atmospheric stability was less important compared to wind direction or leaf density, except for the free convection class. Nevertheless, a variation of canopy aerodynamic parameters with stability was observed and this should be taken into account in atmospheric models