Review and Improvements of Existing Delimitations of Rural Areas in Europe

This report aims to improve current delimitations of rural areas in Europe as a support to statistical descriptions by introducing the criteria of peripherality/remoteness and ¿natural(non-artificial) area¿ in the Organisation for Economic Co-operation and Development (OECD) typology. In 1994, the OECD developed an easy concept to identify rural and urban areas based on the population density of a geographical unit. This scheme proved to be highly sensitive to the size of the geographical area and the classification of the thresholds. Over the years, endeavours have been made to review and improve the OECD approach and also alternative methodologies have been proposed. The current methods based solely on population distributions, do not allow for detailed and quantified geographical analysis and do not reflect two main characters differentiating rural from urban areas: the ¿natural¿ (non-artificial) surface and the accessibility/remoteness. In this study, a new rural typology has been developed by integrating the peripherality index and the land cover indicator in the OECD methodology. The analyses were carried out at Local Administrative Unit (LAU) 2 and NUTS3 level for 3 Member States (Belgium, France and Poland). The resulting rural typology classes for LAU2 are ¿rural-peripheral¿, ¿rural-accessible¿, ¿urban-open-space¿ and ¿urban-closed space¿. The typology at regional level (NUTS3) does not provide an accurate picture of the rurality. The methodology applied is flexible and the thresholds of accessibility or land cover implemented can easily be modified to fit-for-purpose. Simple queries were applied with standard procedures using Pan-European homogeneous datasets so as to allow to upscale for assessment at European level.JRC.H.5-Rural, water and ecosystem resource

Delimitations of Rural Areas in Europe Using Criteria of Population Density, Remoteness and Land Cover

This report aims to improve current delimitations of rural areas in Europe as a support to statistical descriptions by introducing the criteria of peripherality/remoteness and ¿natural (non-artificial) area¿ in the Organisation for Economic Co-operation and Development (OECD) typology. In 1994, the OECD developed an easy concept to identify rural and urban areas based on the population density of a geographical unit. This scheme proved to be highly sensitive to the size of the geographical area and the classification of the thresholds. Over the years, endeavours have been made to review and improve the OECD approach and also alternative methodologies have been proposed. The current methods based solely on population distributions, do not allow for detailed and quantified geographical analysis and do not reflect two main characters differentiating rural from urban areas: the ¿natural¿ (non-artificial) surface and the accessibility/remoteness. In this study, a new rural typology has been developed by integrating the peripherality index and the land cover indicator in the OECD methodology. The analyses were carried out at Local Administrative Unit (LAU 2) level for EU-27and then aggregated at NUTS3 and NUTS2.The methodology applied is flexible and the thresholds of accessibility or land cover implemented can easily be modified to fit-for-purpose.JRC.H.5-Rural, water and ecosystem resource

Conséquences de la saison 2021 sur le rendement quantitatif en viticulture wallonne

peer reviewedPassant de 150 ha (pour 36 exploitations) en 2018 à 300 ha (pour 64 exploitations) à la fin de 2021, la surface viticole wallonne (Belgique – figure 1.a) n’a cessé de croître ces dernières années. Cependant, en 2021, les vignobles wallons ont été fortement touchés par le mildiou (Plasmopara viticola) dû à des conditions météorologiques exceptionnellement humides et fraîches. Cette étude montre que les pertes quantitatives ont été hétérogènes entre les vignobles. Cette variabilité est expliquée principalement par le type de cépage, le mode de production et la gestion liée aux maladies

Toward estimation of seasonal water dynamics of winter wheat from ground-based L-band radiometry: a concept study

peer reviewedThe vegetation optical depth (VOD) variable contains information on plant water content and biomass. It can be estimated alongside soil moisture from currently operating satellite radiometer missions, such as SMOS (ESA) and SMAP (NASA). The estimation of water fluxes, such as plant water uptake (PWU) and transpiration rate (TR), from these earth system parameters (VOD, soil moisture) requires assessing water potential gradients and flow resistances in the soil, the vegetation and the atmosphere. Yet water flux estimation remains an elusive challenge especially on a global scale. In this concept study, we conduct a field-scale experiment to test mechanistic models for the estimation of seasonal water fluxes (PWU and TR) of a winter wheat stand using measurements of soil moisture, VOD, and relative air humidity (RH) in a controlled environment. We utilize microwave L-band observations from a tower-based radiometer to estimate VOD of a wheat stand during the 2017 growing season at the Selhausen test site in Germany. From VOD, we first extract the gravimetric moisture of vegetation and then determine the relative water content (RWC) and vegetation water potential (VWP) of the wheat field. Although the relative water content could be directly estimated from VOD, our results indicate this may be challenging for the phenological phases, when rapid biomass and plant structure development take place within the wheat canopy. We estimate water uptake from the soil to the wheat plants from the difference between the soil and vegetation potentials divided by the flow resistance from soil into wheat plants. The TR from the wheat plants into the atmosphere was obtained from the difference between the vegetation and atmosphere water potentials divided by the flow resistances from plants to the atmosphere. For this, the required soil matric potential (SMP), the vapor pressure deficit (VPD), and the flow resistances were obtained from on-site observations of soil, plant, and atmosphere together with simple mechanistic models. This pathfinder study shows that the L-band microwave radiation contains valuable information on vegetation water status that enables the estimation of water dynamics (up to fluxes) from the soil via wheat plants into the atmosphere, when combined with additional information of soil and atmosphere water content. Still, assumptions have to be made when estimating the vegetation water potential from relative water content as well as the water flow resistances between soil, wheat plants, and atmosphere. Moreover, direct validation of water flux estimates for the assessment of their absolute accuracy could not be performed due to a lack of in situ PWU and TR measurements. Nonetheless, our estimates of water status, potentials, and fluxes show the expected temporal dynamics, known from the literature, and intercompare reasonably well in absolute terms with independent TR estimates of the NASA ECOSTRESS mission, which relies on a Priestly-Taylor type of retrieval model. Our findings support that passive microwave remote-sensing techniques qualify for the estimation of vegetation water dynamics next to traditionally measured stand-scale or plot-scale techniques. They might shed light on future capabilities of monitoring water dynamics in the soil-plant-atmosphere system including wide-area, remote-sensing-based earth observation data

Observed water and light limitation across global ecosystems

peer reviewedAbstract. With a changing climate, it is becoming increasingly critical to understand vegetation responses to limiting environmental factors. Here, we investigate the spatial and temporal patterns of light and water limitation on photosynthesis using an observational framework. Our study is unique in characterizing the nonlinear relationships between photosynthesis and water and light, acknowledging approximately two regime behaviours (no limitation and varying degrees of limitation). It is also unique in using an observational framework instead of using model-derived photosynthesis properties. We combine data from three different satellite sensors, i.e., sun-induced chlorophyll fluorescence (SIF) from the TROPOspheric Monitoring Instrument (TROPOMI), surface soil moisture from the Soil Moisture Active Passive (SMAP) microwave radiometer, and vegetation greenness from the Moderate Resolution Imaging Spectroradiometer (MODIS). We find both single-regime and two-regime models describe SIF sensitivity to soil moisture and photosynthetically active radiation (PAR) across the globe. The distribution and strength of soil moisture limitation on SIF are mapped in the water-limited environments, while the distribution and strength of PAR limitations are mapped in the energy-limited environments. A two-regime behaviour is detected in 73 % of the cases for water limitation on photosynthesis, while two-regime detection is much lower at 41 % for light limitation on photosynthesis. SIF sensitivity to PAR strongly increases along moisture gradients, reflecting mesic vegetation's adaptation to making rapid usage of incoming light availability on the weekly timescales. The transition point detected between the two regimes is connected to soil type and mean annual precipitation for the SIF–soil moisture relationship and for the SIF–PAR relationship. These thresholds therefore have an explicit relation to properties of the landscape, although they may also be related to finer details of the vegetation and soil interactions not resolved by the spatial scales here. The simple functions and thresholds are emergent behaviours capturing the interaction of many processes. The observational thresholds and strength of coupling can be used as benchmark information for Earth system models, especially those that characterize gross primary production mechanisms and vegetation dynamics

HETEROFOR 1.0: A spatially explicit model for exploring the response of structurally complex forests to uncertain future conditions-Part 2: Phenology and water cycle

Climate change affects forest growth in numerous and sometimes opposite ways, and the resulting trend is often difficult to predict for a given site. Integrating and structuring the knowledge gained from the monitoring and experimental studies into process-based models is an interesting approach to predict the response of forest ecosystems to climate change. While the first generation of models operates at stand level, one now needs spatially explicit individual-based approaches in order to account for individual variability, local environment modification and tree adaptive behaviour in mixed and uneven-Aged forests that are supposed to be more resilient under stressful conditions. The local environment of a tree is strongly influenced by the neighbouring trees, which modify the resource level through positive and negative interactions with the target tree. Among other things, drought stress and vegetation period length vary with tree size and crown position within the canopy. In this paper, we describe the phenology and water balance modules integrated in the tree growth model HETEROFOR (HETEROgenous FORest) and evaluate them on six heterogeneous sessile oak and European beech stands with different levels of mixing and development stages and installed on various soil types. More precisely, we assess the ability of the model to reproduce key phenological processes (budburst, leaf development, yellowing and fall) as well as water fluxes. Two two-phase models differing regarding their response function to temperature during the chilling period (optimum and sigmoid functions) and a simplified one-phase model are. used to predict budburst date. The two-phase model with the optimum function is the least biased (overestimation of 2.46 d), while the one-phase model best accounts for the interannual variability (Pearson's r D 0:68). For the leaf development, yellowing and fall, predictions and observations are in accordance. Regarding the water balance module, the predicted throughfall is also in close agreement with the measurements (Pearson's r D 0:856; biasD 1:3 %), and the soil water dynamics across the year are well reproduced for all the study sites (Pearson's r was between 0.893 and 0.950, and bias was between 1:81 and 9:33 %). The model also reproduced well the individual transpiration for sessile oak and European beech, with similar performances at the tree and stand scale (Pearson's r of 0.84 0.85 for sessile oak and 0.88 0.89 for European beech). The good results of the model assessment will allow us to use it reliably in projection studies to evaluate the impact of climate change on tree growth in structurally complex stands and test various management strategies to improve forest resilience. © 2020 Author(s)

Soil water content estimation using ground-based active and passive microwave remote sensing ground-penetrating radar and radiometer

Soil water content is widely recognized as a key component of the water, energy and carbon cycles and knowledge of its spatiotemporal distribution is in particular needed for developing optimal and sustainable environmental and agricultural management strategies. In that context, we analyzed and further developed advanced ground-penetrating radar (GPR) and microwave radiometry techniques for high-resolution mapping and monitoring of shallow soil water content at the field scale. First, far-field ultra-wideband GPR and L-band radiometer were used for mapping soil water content over two test sites with bare soils and the results were compared to reference ground truths. For GPR, soil water content was derived from full-wave inversion focusing on the surface reflection while for radiometer a radiative transfer model was used. Both techniques provided relatively good results, especially for reconstructing spatial moisture patterns in relation to topography and forced conditions (differential irrigation and soil tilth). Nevertheless, absolute estimates were subject to inherent discrepancies that were attributed to the different characterization scales and local variability. Second, we addressed the roughness modeling problem. For GPR, we combined the full-wave GPR model with a roughness model derived from the Kirchhoff scattering theory. Laboratory experiments showed that this approach performs well for roughness amplitudes reaching up to one fourth the wavelength. For the radiometer, we used an empirical equation which requires calibrating ground truths. This approach was successfully validated in field conditions. Finally, GPR and radiometer measurements were performed over a sand box subject to hydrostatic equilibrium with a range of water table depths. For each technique, all measurements were aggregated in an inversion scheme to reconstruct the vertical water content profiles, which were constrained using the van Genuchten water retention equation. The results were in close agreement with reference time-domain reflectometry measurements. Our results open promising research and application perspectives for the joint use of active and passive microwave remote sensing for soil moisture retrieval. In that respect, we addressed new avenues for characterizing crop canopies and water-stress related phenomena.(AGRO 3) -- UCL, 201

Spatial and temporal patterns of throughfall volume in a deciduous mixed-species stand

The effects of canopy structure on the spatial and temporal patterns of throughfall (TF) in deciduous mixed-species stands remains poorly documented. TF was collected on a rain event basis in an oak–beech stand, within 12 structural units of contrasting densities (low, LD; high, HD) and species composition (beech, oak, mixture) delimited by three neighbouring trees. A roof was installed at the centre of each unit, and gutters were placed at the periphery of the LD units. Based on selected rain events, a simplified mass balance approach was used to describe water fluxes reaching and leaving the canopy. During the leafed season, the proportions of incident rainfall (RF) collected as TF on the roofs steadily increased with increasing RF up to a RF volume of about 5 mm; for larger RF volumes, TF proportions stabilised around 55% under pure (LD, HD) beech and HD mixture, and around 65% under pure (LD, HD) oak and LD mixture. During the leafless period, TF proportions (on average 60%) were independent of RF but were still affected by local stand characteristics (HD mixture < HD beech < HD oak < LD beech and mixture < LD oak). At canopy saturation, lateral transfers as branch flow (BF) were substantial (35<=(BF/RF)%<=46) in all plots, and were significantly higher in the HD units compared to the LD plots in the leafless period; part of BF falled down as indirect TF before reaching the trunks, except in the HD units during the leafless season where stemflow and BF were similar. A mechanistic numerical model using rainfall partitioning parameters determined in this study allowed to successfully describe real-time throughfall measurements

In situ characterization of forest litter using ground-penetrating radar

Decomposing litter accumulated on the soil surface in forests plays a major role in several ecosystem processes; its detailed characterization is therefore essential for thorough understanding of ecosystem functioning. In addition, litter is known to affect remote sensing radar data over forested areas and their proper processing requires accurate quantification of litter scattering properties. In the present study, ultrawideband (0.8-2.2 GHz) ground-penetrating radar (GPR) data were collected in situ for a wide range of litter types to investigate the potential of the technique to reconstruct litter horizons in undisturbed natural conditions. Radar data were processed resorting to full-wave inversion. Good agreement was generally found between estimated and measured litter layer thicknesses, with root-mean-square error values around 1 cm for recently fallen litter (OL layer) and around 2 cm for fragmented litter in partial decomposition (OF layer) and total litter (OL + OF). Nevertheless, significant correlations between estimated and measured thicknesses were found for total litter only. Inaccuracies in the reconstruction of the individual litter horizons were mainly attributed to weak dielectric contrasts amongst litter layers, with absolute differences in relative dielectric permittivity values often lower than 2 between humus horizons, and to uncertainties in the ground truth values. Radar signal inversions also provided reliable estimates of litter electromagnetic properties, with average relative dielectric permittivity values around 2.9 and 6.3 for OL and OF litters, respectively. These results are encouraging for the use of GPR for noninvasive characterization and mapping of forest litter. Perspectives for the application of the technique in biogeosciences are discussed. © 2016. American Geophysical Union. All Rights Reserved

Sap flux density and stomatal conductance of European beech and common oak trees in pure and mixed stands during the summer drought of 2003

Sap flux density of European beech and common oak trees was determined from sap flow measurements in pure and mixed stands during the summer drought of 2003. Eight trees per species and per stand were equipped with sap flow sensors. Soil water content was monitored in each stand at different depths by using time-domain reflectometry (TDR). Leaf area index and vertical root distribution were also investigated during the growing season. From sap flux density (SFD) data, mean stomatal conductance of individual trees (Gs) was calculated by inverting the Penman–Monteith equation. Linear mixed models were developed to analyse the effects of species and stand type (pure vs. mixed) on SFD and Gs and on their sensitivity to environmental variables (vapour pressure deficit (D), incoming solar radiation (RG), and relative extractable water (REW)). For reference environmental conditions, we did not find any tree species or stand type effects on SFD. The sensitivity of SFD to D was higher for oak than for beech in the pure stands (P < 0.0001) but the mixing of species reduced it for oak and increased it for beech, so that the sensitivity of SFD to D became higher for beech than for oak in the mixed stand (P < 0.0001). At reference conditions, Gs was significantly higher for beech compared to oak (2.1 and 1.8 times in the pure and mixed stand, respectively). This was explained by a larger beech sapwood-to-leaf area ratio compared to oak. The sensitivity of Gs to REW was higher for beech than for oak and was ascribed to a higher vulnerability of beech to air embolism and to a more sensitive stomatal regulation. The sensitivity of beech Gs to REW was lower in the mixed than in the pure stand, which could be explained by a better sharing of the resources in the mixture, by facilitation processes (hydraulic lift), and by a rainfall partitioning infavour of beech