Decadal water balance of a temperate Scots pine forest (Pinus sylvestris L.) based on measurements and modelling

We examined the water balance components of an 80-year-old Scots pine (Pinus sylvestris L.) forest stand in the Campine region of Belgium over a ten year period using five very different approaches; our methods ranged from data intensive measurements to process model simulations. Specifically, we used the conservative ion method (CI), the Eddy Covariance technique (EC), an empirical model (WATBAL), and two process models that vary greatly in their temporal and spatial scaling, the ORCHIDEE global land-surface model and SECRETS a stand- to ecosystem-scale biogeochemical process model. Herein we used the EC technique as a standard for the evapotranspiration (ET) estimates. Using and evaluating process based models with data is extremely useful as models are the primary method for integration of small-scale, process level phenomena into comprehensive description of forest stand or ecosystem function. Results demonstrated that the two process models corresponded well to the seasonal patterns and yearly totals of ET from the EC approach. However, both WATBAL and CI approaches overestimated ET when compared to the EC estimates. We found significant relationships between several meteorological variables (i.e., vapour pressure deficit [VPD], mean air temperature [Tair], and global radiation [Rg]) and ET on monthly basis for all approaches. In contrast, few relationships were significant on annual basis. Independent of the method examined, ET exhibited low inter-annual variability. Consequently, drainage fluxes were highly correlated with annual precipitation for all approaches examined, except CI

No impact of tropospheric ozone on the gross primary productivity of a Belgian pine forest

Imbalance-P paper. Contact with Lore Verryckt: [email protected] stomatal ozone (O3) uptake has been shown to negatively affect crop yields and the growth of tree seedlings. However, little is known about the effect of O3 on the carbon uptake by mature forest trees. This study investigated the effect of high O3 events on gross primary productivity (GPP) for a Scots pine stand near Antwerp, Belgium over the period 1998-2013. Stomatal O3 fluxes were modelled using in situ O3 mixing ratio measurements and a multiplicative stomatal model, which was parameterised and validated for this Scots pine stand. Ozone-induced GPP reduction is most likely to occur during or shortly after days with high stomatal O3 uptake. Therefore, a GPP model within an artificial neural network was parameterised for days with low stomatal O3 uptake rates and used to simulate GPP during periods of high stomatal O3 uptake. Possible negative effects of high stomatal O3 uptake on GPP would then result in an overestimation of GPP by the model during or after high stomatal O3 uptake events. The O3 effects on GPP were linked to AOT40 and POD1. Although the critical levels for both indices were exceeded in every single year, no significant negative effects of O3 on GPP were found, and no correlations between GPP residuals and AOT40 and POD1 were found. Overall, we conclude that no O3 effects were detected on the carbon uptake by this Scots pine stand

Introduction

Le rôle de l’économie privée dans la promotion du développement, que ce soit au Sud ou à l’Est, jouit d’une reconnaissance croissante tant parmi les acteurs du développement au Nord que chez leurs partenaires du Sud. Parallèlement, les organisations internationales (Banque mondiale, institutions de l’ONU) et les agences nationales de développement attachent de plus en plus d’importance à la promotion du secteur privé. Comment les entreprises privées, surtout les petites et moyennes entreprise..

Carbon and water vapor fluxes over four forests in two contrasting climatic zones

AbstractThe inter- and seasonal patterns of water vapor and canopy carbon fluxes were compared for four forest ecosystems in two contrasting climatic zones in Europe. The eddy covariance and ancillary data were taken from the Carboeurope and FLUXNET databases and a linear modeling statistical analysis was made. The four sites were a high-density poplar (Populus spp.) short rotation coppice plantation (in Lochristi, Belgium) and a mature Scots pine (Pinus sylvestris) forest (in Brasschaat, Belgium) in the Temperate climate versus a fast-growing Eucalypt (Eucalyptus) plantation (in Espirra, Portugal) and a Holm oak (Quercus ilex) forest (in Puechabon, France) in the Mediterranean climate.•The Eucalypt stand showed an efficient stomatal control in response to changes in vapor pressure deficit (VPD), suggesting an ideal adaptation of this species to the severe Mediterranean climate.•The fast-growing poplar stand did not show a similar stomatal control under conditions of moderate water stress. But during an intensive dry period a decrease in the development of the leaf area index (LAI) was observed.•The Holm oak stand showed a low GPP, which is typical for a low productive species with a long rotation cycle. The GPP showed low diurnal variability, even under high solar radiation. This behavior suggested a strong stomatal control caused by the severe water stress, a mechanism that allowed this stand to cope with diurnal and seasonal water deficits.•The mature Scots pine forest in the Temperate climate showed no variation in the GPP – radiation relationship. In this forest no water stress was observed, probably because the trees always had access to the water table. Irrespective of the climate the evapotranspiration of the Scots pine forest presented a tight coupling with the atmosphere, i.e. a low decoupling factor, Ω, comparable with the Holm oak and the Eucalypt forests.The high Ω values of the young poplar plantation were not typical for forest canopies. These values confirmed the strong influence of solar radiation and available energy on evapotranspiration and on the dynamics of this fast-developing canopy. At all four sites the forests showed their capacity to react to the environmental drivers, characteristic from their respective climatic types. However, drastic climatic changes – such as heat waves or long drought spells – may compromise the productivity of fast-growing plantations such as the Eucalypt and poplar stands. The response of the poplars to these events is mainly achieved through LAI control in contrast to the stomatal control in the Eucalypts

Consequences of vertical basic wood density variation on the estimation of aboveground biomass with terrestrial laser scanning

Terrestrial laser scanning (TLS) is used to generate realistic 3D tree models that enable a non-destructive way of quantifying tree volume. An accurate value for basic wood density is required to convert tree volume into aboveground biomass (AGB) for forest carbon assessments. However, basic density is characterised by high inter-, intra-species and within-tree variability and a likely source of error in TLS-derived biomass estimates. Here, 31 adult trees of 4 important European timber species (Fagus sylvatica, Larix decidua, Pinus sylvestris, Fraxinus excelsior) were scanned using TLS and then felled for several basic wood density measurements. We derived a reference volume-weighted basic density (ρw) by combining volume from 3D tree models with destructively assessed vertical density profiles. We compared this to basic density retrieved from a single basal disc over bark (ρbd), two perpendicular pith-to-bark increment cores at breast height (ρic), and sourcing the best available local basic wood density from publications. Stump-to-tip trends in basic wood density caused site-average woody AGB estimation biases ranging from −3.3 to + 7.8% when using ρbd and from −4.1 to + 11.8% when using ρic. Basic wood density from publications was in general a bad predictor for ρw as the bias ranged from −3.2 to + 17.2%, with little consistency across different density repositories. Overall, our density-attributed biases were similar to several recently reported biases in TLS-derived tree volume, leading to potentially large compound errors in biomass assessments with TLS if patterns of vertical basic wood density variation are not properly accounted for

Low loss CMOS-compatible PECVD silicon nitride waveguides and grating couplers for blue light optogenetic applications

This paper presents silicon nitride (SixNy) photonic integrated circuits (PICs) with high performance at a wavelength of 450 nm, which, therefore, is suitable for neuronal stimulation with optogenetics. These PICs consist of straight and bent waveguides, and grating couplers that are fabricated in a complementary metal-oxide-semiconductor (CMOS)-compatible plasma enhanced chemical vapor deposition SixNy platform. Their characterization shows propagation losses of 0.96 +/- 0.4 dB/cm on average for straight waveguides that are 1-5 mu m wide and bend insertion losses as low as 0.2 dB/90. for 1 mu m wide waveguides with a radius of 100 mu m. Additionally, the grating coupler characterization shows that they can deliver about 10 mu W of light in an area of 5 x 9 mu m(2) (240 mW/mm(2)), which is captured from an uncollimated laser diode (70 mW). Besides delivering sufficient power for optogenetic applications, the gratings have dimensions that are comparable to the size of a neuron, which would allow single cell interaction. These results demonstrate that, with this SixNy platform, high-density and large-scale implantable neural devices can be fabricated and readily integrated into existing CMOS-compatible neuro-electronic platforms

Copernicus Cal/Val Solution - D3.3 - Copernicus operational FRM network and supersites

- Identify measurement gaps, considering the existing ground-based Cal/Val measurement campaigns and networks (as outcome from Tasks 2.4 and 2.5) - Identify rationalization and optimization pathways: e.g., use of common instrumentation, protocols, and standards across sites; cross-Sentinel use of generic measurements; “supersite” approaches to minimize maintenance costs, as well as possible synergies with other European or international programs - Define a minimum set of requirements for a “Copernicus” label for measurement sites, addressing measurement protocols, documentation, availability, data policy; define a certification process - Principles and need to evaluate degree of equivalence between individual networks and sites (inter-comparisons) and for other comparison measurement

Standardisation of eddy-covariance flux measurements of methane and nitrous oxide

Commercially available fast-response analysers for methane (CH4) and nitrous oxide (N2O) have recently become more sensitive, more robust and easier to operate. This has made their application for long-term flux measurements with the eddycovariance method more feasible. Unlike for carbon dioxide (CO2) and water vapour (H2O), there have so far been no guidelines on how to optimise and standardise the measurements. This paper reviews the state-of-the-art of the various steps of the measurements and discusses aspects such as instrument selection, setup and maintenance, data processing as well as the additional measurements needed to aid interpretation and gap-filling. It presents the methodological protocol for eddy covariance measurements of CH4 and N2O fluxes as agreed for the ecosystem station network of the pan-European Research Infrastructure Integrated Carbon Observation System and provides a first international standard that is suggested to be adopted more widely. Fluxes can be episodic and the processes controlling the fluxes are complex, preventing simple mechanistic gap-filling strategies. Fluxes are often near or below the detection limit, requiring additional care during data processing. The protocol sets out the best practice for these conditions to avoid biasing the results and long-term budgets. It summarises the current approach to gap-filling.Peer reviewe

The Integrated Carbon Observation System in Europe

Since 1750, land-use change and fossil fuel combustion has led to a 46% increase in the atmospheric carbon dioxide (CO2) concentrations, causing global warming with substantial societal consequences. The Paris Agreement aims to limit global temperature increases to well below 2 degrees C above preindustrial levels. Increasing levels of CO2 and other greenhouse gases (GH6s), such as methane (CH4) and nitrous oxide (N2O), in the atmosphere are the primary cause of climate change. Approximately half of the carbon emissions to the atmosphere are sequestered by ocean and land sinks, leading to ocean acidification but also slowing the rate of global warming. However, there are significant uncertainties in the future global warming scenarios due to uncertainties in the size, nature, and stability of these sinks. Quantifying and monitoring the size and timing of natural sinks and the impact of climate change on ecosystems are important information to guide policy-makers' decisions and strategies on reductions in emissions. Continuous, long-term observations are required to quantify GHG emissions, sinks, and their impacts on Earth systems. The Integrated Carbon Observation System (ICOS) was designed as the European in situ observation and information system to support science and society in their efforts to mitigate climate change. It provides standardized and open data currently from over 140 measurement stations across 12 European countries. The stations observe GHG concentrations in the atmosphere and carbon and GHG fluxes between the atmosphere, land surface, and the oceans. This article describes how ICOS fulfills its mission to harmonize these observations, ensure the related long-term financial commitments, provide easy access to well-documented and reproducible high-quality data and related protocols and tools for scientific studies, and deliver information and GHG-related products to stakeholders in society and policy.Peer reviewe

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'