Northeastern France Research Articles

Phenological sensitivity to temperature mediates herbivory.

Species interactions drive ecosystem processes and are a major focus of global change research. Among the most consequential interactions expected to shift with climate change are those between insect herbivores and plants, both of which are highly sensitive to temperature. Insect herbivores and their host plants display varying levels of synchrony that could be disrupted or enhanced by climate change, yet empirical data on changes in synchrony are lacking. Using evidence of herbivory on herbarium specimens collected from the northeastern United States and France from 1900 to 2015, we provide evidence that plant species with temperature-sensitive phenologies experience higher levels of insect damage in warmer years, while less temperature-sensitive, co-occurring species do not. While herbivory might be mediated by interactions between warming and phenology through multiple pathways, we suggest that warming might lengthen growing seasons for phenologically sensitive plant species, exposing their leaves to herbivores for longer periods of time in warm years. We propose that elevated herbivory in warm years may represent a previously underappreciated cost to phenological tracking of climate change over longer timescales.

Severe Intraabdominal Hypertension in Critically Ill COVID-19 Patients With Acute Kidney Injury

Severe Intraabdominal Hypertension in Critically Ill COVID-19 Patients With Acute Kidney Injury

Isolation and Genetic Characterization of Puumala Orthohantavirus Strains from France.

Puumala orthohantavirus (PUUV) causes a mild form of haemorrhagic fever with renal syndrome (HFRS) called nephropathia epidemica (NE), regularly diagnosed in Europe. France represents the western frontier of the expansion of NE in Europe with two distinct areas: an endemic area (north-eastern France) where PUUV circulates in rodent populations, with the detection of many human NE cases, and a non-endemic area (south-western France) where the virus is not detected, with only a few human cases being reported. In this study, we describe the different stages of the isolation of two PUUV strains from two distinct French geographical areas: Ardennes (endemic area) and Loiret (non-endemic area). To isolate PUUV efficiently, we selected wild bank voles (Myodes glareolus, the specific reservoir of PUUV) captured in these areas and that were seronegative for anti-PUUV IgG (ELISA) but showed a non-negligible viral RNA load in their lung tissue (qRT-PCR). With this study design, we were able to cultivate and maintain these two strains in Vero E6 cells and also propagate both strains in immunologically neutral bank voles efficiently and rapidly. High-throughput and Sanger sequencing results provided a better assessment of the impact of isolation methods on viral diversity.

Temporal Distribution and Gas/Particle Partitioning of Polycyclic Aromatic Hydrocarbons (PAHs) in the Atmosphere of Strasbourg, France

Gas and particulate phase ambient air concentrations of polycyclic aromatic hydrocarbons (Ʃ16PAHs) were determined in Strasbourg, a large city located in the Alsace region of northeastern France, from May 2018 to March 2020, to study the evolution of their temporal variations and their potential origins. The analysis of PAHs was performed using a global analytical method permitting the quantification of pesticides, PAHs, and polychlorobiphenyls (PCBs). Filters and Carbon doped silicon carbide NMC@SiC foams were extracted by accelerated solvent extraction (ASE) followed by a solid-phase extraction (SPE). Afterwards, extracts were analyzed using gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). Prior to analysis, a pre-concentration step based on solid-phase microextraction (SPME) was used with a polydimethylsiloxane (PDMS) 100 µm fiber. The average total (gas plus particulate) concentration of Ʃ16PAHs varied from 0.51 to 117.31 ng m−3 with a mean of 16.87 ng m−3, with higher concentrations in the cold season of more than 2.5-fold and 6-fold that in the warm season for the gas and particulate phases, respectively. Moreover, low molecular weight (LMW) (2-ring and 3-ring) and medium molecular weight (MMW) (4-ring) PAHs contribute dominantly to the gas phase, while the particulate phase is associated with MMW (4-ring) and high molecular weight (HMW) (5-ring and 6-ring) PAHs. Gas/particle partitioning coefficient (log Kp) was calculated, and values varied between −4.13 and −1.49. It can be seen that the log Kp increased with the molecular weight of the PAHs and that the log Kp is different between cold and warm seasons for HMW PAHs but not for LMW PAHs. Diagnostic ratios of PAHs, which were employed to estimate the primary source of PAHs in Strasbourg, indicate that fuel combustion and biomass/coal burning are the possible origins of PAHs in Strasbourg’s atmosphere.

Biological aspectss of the Marsh frog Pelophylax ridibundus population from the Shadegan Wetland, Khuzestan Province, Iran

The Marsh frog, Pelophylax ridibundus (Pallas) is distributed in Central Europe from northeastern France, north to the southern shorelines of the Baltic Sea (and extreme southern Finland), south to northeastern Spain, northern Italy and the Balkans including eastern Greece, east to approximately 81° E in Asiatic Russia, and south to western Iran and Afghanistan. The present study has been conducted on populations of P. ridibundus in the northern, eastern and southern regions of the Shadegan Wetland of Khuzestan Province, Iran with the aim of examining some aspects of its morphology and karyotype. Frog specimens were collected from different portions of the Shadegan Wetland during spring and autumn 2016 and transferred to the laboratory. According to the morphological results, three color patterns are identified among the samples in terms of the morphology, morphometry and sex - according to the sex independency test. T-test results between males and females indicate a significant difference in all traits and the results of a T2 Hotelling test show that there is sexual dimorphism between males and females. However, the results of multivariate analysis of variance (MANOVA) illustrate a separation between males of the northern region and the two other regions, and no differentiation between females in the eastern and southern regions of the wetland. The karyotype of the species in the wetland included 2n= 26, one pair of which had a sex chromosome.

Canopy openness and exclusion of wild ungulates act synergistically to improve oak natural regeneration

The recruitment of forest trees is driven by both bottom-up processes (the acquisition of resources) and top-down processes (herbivory). To initiate stand regeneration, foresters commonly reduce tree density to increase light levels for seedlings and enhance primary productivity. These changes in vegetation dynamics, however, could also influence effects of ungulate browsing, resulting in unintended consequences for forest management. Here, we assessed how effects of ungulate exclusion and canopy opening interacted to affect the regeneration of two oak species: Quercus robur and Quercus petraea. We monitored the growth and survival of oak seedlings for two to three growth seasons in paired fenced and unfenced plots under contrasting conditions of canopy openness (8% to 52%) at five sites in southern Sweden and three sites in northeastern France. We scored browsing in the unfenced plots by the four cervids occurring in these areas (Alces alces, Capreolus capreolus, Cervus elaphus and Dama dama). Fencing increased the growth of (mostly taller) seedlings occurring in Sweden and the survival of (mostly smaller) seedlings in France. Both effects increased as canopies became more open. Browsing reduced oak seedling growth in both countries, independently of canopy openness. Canopy openness increased browsing levels in Sweden. Cervid densities did not appear to modify how fencing affected oak seedling growth and survival. In both contrasting forest environments, creating gaps tended to enhance ungulate damage on young forest stands as browsing frequency increased. We conclude that net forest regeneration reflects a subtle equilibrium between enhancing resource availability, boosting seedling growth, and limiting herbivory, which curtails seedling growth and survival.

Association between depressive symptoms and subsequent injuries in early adolescents: a population-based study

Objectives Depressive symptoms (DSs) may be frequent and highly increase the risk of injuries in early adolescents (10–16 years). This study assessed the association between DSs and subsequent school and out-of-school injuries in early adolescents. Methods The study population included 1219 middle-school adolescents from north-eastern France (mean age =12.7 ± 1.3) who completed at the end of school-year a questionnaire gathering socioeconomic features (nationality, family structure, parents’ occupation, parents’ education, and family income), obesity, alcohol use, tobacco use, health status, DSs (Kandel scale higher than the median value, hence including moderate levels), and school and out-of-school injuries during the present school-year. Were only considered the DSs and confounders that had started before the school-year. Data was analyzed using multinomial logistic regression models. Results DSs were strongly associated with one or more school-physical/sports-training injuries (sex-age-adjusted odds ratio ORsa 2.08, p < 0.001), other-school-training injuries (ORsa 2.13, p < 0.01), school-free-time injuries (ORsa 2.84, p < 0.001), out-of-school-sports injuries (ORsa 1.95, p < 0.001), and traffic injuries (ORsa 3.78, p < 0.001). The risk was higher for having two or more injury categories (ORsa 4.03, p < 0.001) than for only one injury category (ORsa 1.80, p < 0.001). These results were robust and remained after further adjustment for socioeconomic features, obesity, alcohol use, tobacco use, and health status. Conclusions DSs strongly increase the injury risk in early adolescents. Injury prevention should include DSs screening and monitoring and help adolescents and their neighborhood be aware of the risk. Highlights Injuries and depressive symptoms (DSs) are frequent in early adolescents. DSs highly predict subsequent school and out-of-school injuries and cumulating several injury types. These results are robust after adjustment for socioeconomic features, being obese, alcohol use, tobacco use and poor health status. Injury prevention should include early DSs screening and monitoring and help adolescents and their neighborhood be aware of the risk.

Epidemiological surveillance of SARS-CoV-2 by genome quantification in wastewater applied to a city in the northeast of France: Comparison of ultrafiltration- and protein precipitation-based methods.

The aim of the present study was to develop a simple, sensitive, and specific approach to quantifying the SARS-CoV-2 genome in wastewater and to evaluate this approach as a means of epidemiological surveillance. Twelve wastewater samples were collected from a metropolitan area in north-eastern France during April and May 2020. In addition to the quantification of the SARS-CoV-2 genome, F-specific RNA phages of genogroup II (FRNAPH GGII), naturally present in wastewater, were used as an internal process control for the viral concentration and processing of RT-PCR inhibitors. A concentration method was required to allow the quantification of the SARS-CoV-2 genome over the longest possible period. A procedure combining ultrafiltration, phenol-chloroform-isoamyl alcohol purification, and the additional purification of the RNA extracts was chosen for the quantification of the SARS-CoV-2 genome in 100-mL wastewater samples. At the same time, the COVID-19 outbreak was evaluated through patients from the neighbouring University Hospital of Nancy, France. A regular decrease in the concentration of the SARS-CoV-2 genome from ~104 gc/L to ~102 gc/L of wastewater was observed over the eight weeks of the study, during which the population was placed under lockdown. The SARS-CoV-2 genome was even undetectable during one week in the second half of May and present but non-quantifiable in the last sample (28 May). A concordant circulation in the human community was highlighted by virological diagnosis using respiratory samples, which showed a decrease in the number of COVID-19 cases from 677 to 52 per week over the same period. The environmental surveillance of COVID-19 using a reliable viral quantification procedure to test wastewater is a key approach. The real-time detection of viral genomes can allow us to predict and monitor the circulation of SARS-CoV-2 in clinical settings and survey the entire urban human population.

Long-term monitoring of activities of badgers (Meles meles L.) in a broadleaved forest in France

European badgers’ behaviors have been studied over a 6-year period (2013–2018) using camera traps settled in a main sett (400 m2; 17 holes) in an oak forest, northeastern France. I analyzed group’s size, grooming, digging, bedding collecting, mating, and the emergence and return times. The burrow was inhabited by 2.8 (± 1.2) badgers. I observed between 2 and 4 new cubs each year in 5 out of 6 years, with a first emergence in mid-April. Grooming was frequent after emergence at dusk and lasted around 10 min (more frequent grooming in April after the births). Bedding collecting was a major activity in February and March during dry nights (mean duration of around 20 min) for years with births. Digging occurred only in winter 2015 and spring 2016, mainly at dusk (mean: 23 min, 2 to 90 min). Mating occurred mainly in January and February with short (< 10 min) and long (> 60 min) duration of copulation. Emergences occurred mainly between 19 and 21 h and returns between 5 and 7 h. For spring and summer, badgers emerged between 30 and 60 min before sunset but 2 h or more after sunset in autumn and winter. Returns occurred before sunrise in the middle of the night (1 h in spring and summer and 2 h or more in autumn and winter). In autumn and winter, warm nights hastened emergences time (i.e., maximum temperature higher than 10 °C) and frost nights hastened returns (i.e., minimum temperature below 0 °C).

From the Neolithic to the present day: The impact of human presence on floristic diversity in the sandstone Northern Vosges (France)

The Northern Vosges and the Pays de Bitche (north-eastern France) are well-known regions for their rich recent industrial heritage. On the other hand, the ancient history of these regions is less well known and the relationships between human populations and their environments during ancient times is still largely unexplored. We carried out a multidisciplinary paleoenvironmental study on the site of the bog pond located below the ruins of the medieval castle of Waldeck in order to reconstruct the history of the vegetation in the region since 6600 cal. BP. Throughout the Holocene, the succession of forest vegetation (pine and hazelnut forests, reduced oak forest, beech forest, oak-beech forest) was largely dominated by pine. Human presence was tenuous during the Neolithic period, then well marked from the Bronze Age onwards with the introduction of crops and livestock crops in the catchment area. From the Middle Ages onwards, anthropic pressure increased dramatically with the building of Waldeck Castle in the thirteenth century, which led to a major opening of the area. The Modern period is characterized by a gradual return of the forest, with decreasing anthropogenic pressure. Over time, occupation phases were interspersed with abandonment phases during which human activities regressed or disappeared. Finally, the rarefaction analysis carried out on pollen data shows that human presence led to a gradual increase in plant diversity, which peaked in the Middle Ages, whereas the forest lost some of its resilience to human disturbance over time.

Soil contamination by Echinococcus multilocularis in rural and urban vegetable gardens in relation to fox, cat and dog faecal deposits.

Echinococcus multilocularis eggs are deposited on the ground with the faeces of the carnivore definitive hosts. A reliable assessment of the spatial distribution of E. multilocularis eggs in environments used by humans is crucial for the prevention of alveolar echinococcosis (AE). This study was conducted in 192 rural and 71 urban vegetable gardens in AE endemic areas of north-eastern France. Its objective was to explore the relationship between the spatial distribution of E. multilocularis estimated from the collection and molecular analysis of two types of samples: faeces and soil. A total of 1024 carnivore faeces and 463 soil samples were collected and analysed by real-time PCR. No fox droppings and no positive soil samples were collected from the urban gardens. Positive soil samples, positive carnivore faeces, or both, were found in 42%, 24% and 6% of the sampled rural gardens, respectively. No significant association was found between the detection of E. multilocularis in soil samples collected from 50 gardens during a single sampling session and the extent and frequency of deposits of fox and cat faeces collected during repeated sampling sessions conducted in the previous months. In 19/50 gardens, E. multilocularis was detected in the soil while no positive faeces had been collected in the previous 12 months. Conversely, in 8/50 gardens, no soil samples were positive although positive faeces had been collected in the previous months. Collecting and analysing faeces provide information on soil contamination at a given time, while analysing soil samples provides an overview of long-term contamination.

A brief history of plants in north-eastern France: 6,000 years of crop introduction in the Plain of Troyes, Champagne

The amount and strength of archaeobotanical and archaeological data available for the territory of the Plain of Troyes, in Champagne (north-eastern France), make it possible to write a local history of domestic plants. The story begins with the arrival of the early Neolithic farmers (5200 bc), introducing agriculture with the first staple crops, the hulled wheats emmer and einkorn, pea, lentil, and possibly opium poppy. Their descendants left few traces, but from the very beginning of the Late Bronze Age (14th century bc), human expansion quickly resumed, supported by a completely remodelled farming system. Many new plants (spelt, millets, pulses…), introduced from far-off countries were cultivated, securing production, and decreasing gathering. This apparently successful agriculture lasted for one millennium till the middle of the Late Iron Age (2nd century bc). Technical innovations in agricultural tools then triggered new changes in production systems, evidenced by a sharp decline in millets and a more modest rise in naked wheats. This trend continued during the Roman era, a time where many agricultural innovations took place, especially concerning fruticulture and possibly viticulture. The true development of the latter occurred during Early Middle Ages. At that time hulled six-row barley and naked wheats were well established as the main crops, while two more species, cultivated oat and rye, were added to the already large panel of cereals. Our investigations do not go further than the 10th century ad, but despite the large gap till today, some legacies of the past are still perceptible in the contemporary agricultural heritage.

Multidimensional assessment demonstrates sustainability of new low-input viticulture systems in north-eastern France

Current demand for more environmentally, socially, and economically sustainable farming practices requires multicriteria assessment of innovative agricultural systems to help enhance cropping systems. We assessed the sustainability of 11 systems intended to substantially reduce inputs, especially pesticides, to viticulture systems. Pesticide use was reduced using three methods: (i) technical (e.g., essential oils instead of some copper use, 100 % soil covering applied); (ii) organizational (e.g., new spraying decision rules, decision aid tools); and (iii) redesign of the entire system (e.g., resistant grape varieties planted). Sustainable performance of the new low-input vine systems (NLIVS) was assessed over 6 years (2013–2018) based on 25 indicators. They covered all aspects of system sustainability: environmental, agronomic, economic, and social. This included the evaluation of human capital and the quality of the wines produced. The results showed that it is possible to combine good environmental performance, such as reducing treatment frequency by up to 89 %, with good agronomic and wine quality performances. The socio-economic performance of these NLIVS was more moderate. Nonetheless, the results demonstrated that the NLIVS are sustainable according to many diversified indicators. NLIVS are also resilient, as shown by the consistent sustainability results over six consecutive years. They are a realistic tool enabling winegrowers to consider reducing viticulture inputs.

Tree rings reveal signs of Europe\u2019s sustainable forest management long before the first historical evidence

To satisfy the increasing demand for wood in central Europe during medieval times, a new system of forest management was developed, one far superior to simple coppicing. The adoption of a sophisticated, Coppice-with-Standards (CWS) management practice created a two-storey forest structure that could provide fuelwood as well as construction timber. Here we present a dendrochronological study of actively managed CWS forests in northern Bavaria to detect the radial growth response to cyclical understorey harvesting in overstorey oaks (Quercus sp.), so-called standards. All modern standards exhibit rapid growth releases every circa 30 years, most likely caused by regular understorey management. We further analyse tree-ring width patterns in 2120 oak timbers from historical buildings and archaeological excavations in southern Germany and north-eastern France, dating between 300 and 2015 CE, and succeeded in identifying CWS growth patterns throughout the medieval period. Several potential CWS standards even date to the first millennium CE, suggesting CWS management has been in practice long before its first mention in historical documents. Our dendrochronological approach should be expanded routinely to indentify the signature of past forest management practices in archaeological and historical oak wood.

Temporal variations in the diagnostic performance of chest CT for Covid-19 depending on disease prevalence: Experience from North-Eastern France

Rationale and ObjectiveThe purpose of this work was to analyze temporal variations in the diagnostic performance of chest CT for Covid-19 throughout the first wave, depending on disease prevalence variations between the ascending, peak and descending phases of the epidemic in North-Eastern France. Materials and MethodsFrom March 6th to April 22nd 2020, all consecutive adult patients referred to the “Covid-19 clinic” of our Emergency Department with the availability of chest CT and of at least one RT-PCR result were retrospectively included in the present study. Chest CT was considered positive when typical Covid-19 lesions were observed (bilateral and predominantly peripheral and sub-pleural ground glass opacities and/or alveolar consolidations). RT-PCR results were considered as the reference standard. Ascending, peak and descending phases were determined based on the number of CT scans performed daily. CT diagnostic performance were calculated and variations between phases were tested for equivalence or difference using Bayesian methods. Results2194 consecutive chest CT were analyzed. Overall CT diagnostic performance was Se = 84.2 [82.0 ; 86.3], Sp = 86.6 [84.5 ; 88.5], PPV = 86.1 [84.0 ; 88.1], NPV = 84.7 [82.6 ; 86.7] and accuracy = 85.4 [83.9 ; 86.8], with no significant differences between chest and non-chest radiologists. Variations between the ascending (11 days, 281 chest CT, disease prevalence 37.0 %), the peak (18 days, 1167 chest CT, disease prevalence 64 %) and the descending phases (19 days, 746 chest CT, disease prevalence 32.2 %) were highest for PPV and NPV with a probability of difference >99.9 %, and smallest for accuracy and specificity with a probability of equivalence >98.8 %. ConclusionIn a homogenous cohort of 2194 consecutive chest CT performed over a 7-week epidemic wave, we observed significant variations of CT predictive values whereas CT specificity appeared marginally affected.

Leafy season length is reduced by a prolonged soil water deficit but not by repeated defoliation in beech trees (Fagus sylvatica L.): comparison of response among regional populations grown in a common garden

Bud-burst and leaf-senescence determine the length of the growing season for deciduous trees and therefore the duration of potential carbon assimilation with consequences on biomass production. In Fagus sylvatica L., leaf phenology depends on both photoperiod and temperature. The future climate is expected to induce more frequent soil water deficits and biotic attacks (possibly resulting in severe defoliation). The aim of the study is to assess whether these constrains may alter leaf phenology. In a common garden, we sowed seeds collected from six beech forests along a small latitudinal gradient (140 km) in North-Eastern France. In 2014, after seven years growth, a rain exclusion was installed above the trees to test how recurrent soil water deficits impacted bud-burst (BB) and leaf-yellowing (LY) over three years. We also analyzed the response of leaf phenology to annual defoliation, aiming at affecting carbon and nitrogen availability in trees. Delayed BB and early LY were observed, reducing the growing season (GS) until 14 days in response to soil water deficit whereas no influence of defoliation was detected. These time lags were not in relation with leaf nitrogen content. In the control treatment, BB occurred earlier and LY later in the northernmost populations than in the southernmost without clear relationships with local climate. A significant treatment x population interaction was observed revealing a plasticity in the leaf phenology response to soil water deficit among populations. These results suggest that beech trees present a genetic differentiation of leaf phenology even within a small latitudinal gradient but that these differentiations could be disrupted by soil water deficit that is predicted to increase in the future.

A Temporary Space Where Development and Planning Emergencies Meet? Notes on an International Building Exhibition (IBA) in the Cross-Border Territories of France and Luxembourg

The cross-border area of southern Luxembourg and north-eastern France, named “Alzette-Belval”, is presently subject to an International Building Exhibition (in German Internationale Bauausstellung,...

1H-NMR metabolomics profiling of zebra mussel (Dreissena polymorpha): A field-scale monitoring tool in ecotoxicological studies.

Biomonitoring of aquatic environments requires new tools to characterize the effects of pollutants on living organisms. Zebra mussels (Dreissena polymorpha) from the same site in north-eastern France were caged for two months, upstream and downstream of three wastewater treatment plants (WWTPs) in the international watershed of the Meuse (Charleville-Mézières "CM" in France, Namur "Nam" and Charleroi "Cr" in Belgium). The aim was to test 1H-NMR metabolomics for the assessment of water bodies' quality. The metabolomic approach was combined with a more "classical" one, i.e., the measurement of a range of energy biomarkers: lactate dehydrogenase (LDH), lipase, acid phosphatase (ACP) and amylase activities, condition index (CI), total reserves, electron transport system (ETS) activity and cellular energy allocation (CEA). Five of the eight energy biomarkers were significantly impacted (LDH, ACP, lipase, total reserves and ETS), without a clear pattern between sites (Up and Down) and stations (CM, Nam and Cr). The metabolomic approach revealed variations among the three stations, and also between the upstream and downstream of Nam and CM WWTPs. A total of 28 known metabolites was detected, among which four (lactate, glycine, maltose and glutamate) explained the observed metabolome variations between sites and stations, in accordance with chemical exposure levels. Metabolome changes suggest that zebra mussel exposure to field contamination could alter their osmoregulation and anaerobic metabolism capacities. This study reveals that lactate is a potential biomarker of interest, and 1H-NMR metabolomics can be an efficient approach to assess the health status of zebra mussels in the biomonitoring of aquatic environments.

U-Pb geochronology of detrital and igneous zircon grains from the Águilas Arc in the Internal Betics (SE Spain): Implications for Carboniferous-Permian paleogeography of Pangea

New U–Pb detrital zircon and U–Pb zircon ages of metaigneous rocks in the Águilas Arc (Betic Chain, SE Spain) allow us to determine the maximum depositional ages of the rocks. Within the Nevado-Filábride Complex, a Late Carboniferous depositional age for the Lomo de Bas schists and quartzites, and a Permian-Triassic maximum depositional age for the Tahal Fm are determined. Within the Alpujárride Complex, the maximum depositional age of the Micaschists and Quartzite Fm is Late Carboniferous and the Meta-detrital Fm was deposited in the Early Permian. Furthermore, the maximum depositional age of the Saladilla Fm in the Maláguide Complex is also Early Permian. The age distribution patterns for the Carboniferous rocks of the Nevado-Filábride and Alpujárride complexes are similar to those from the Cantabrian Zone of the Iberian Massif, suggesting deposition in Carboniferous foreland basins located eastwards of the Iberian Massif. However, age patterns in Maláguide and samples from the North-eastern Iberian Peninsula and South France show strong similarities suggesting that it can be located near those areas in the Late Carboniferous times.The samples with Early Permian maximum depositional ages from the three complexes contain more Paleozoic zircon grains relative to the older Carboniferous samples, but have similar age distribution patterns, suggesting that they were deposited in the same basin. Samples from unconformable Middle Miocene sediments have Early Permian youngest zircon populations and age distribution patterns corresponding to a mixing of detrital zircon grains from the Alpujárride and Maláguide complexes. Furthermore, there is no record of any major felsic rocks formation and/or exhumation event after the Early Permian in those two complexes.

Growth dynamics of fast-growing tree species in mixed forestry and agroforestry plantations

In recent years, plantations of fast-growing tree species have emerged as a possible way to meet the increasing demand for biomass for renewable energy in Europe. Agroforestry plantations including fast-growing tree species could be an attractive option because they reduce land competition for biomass and food production while providing forest benefits. Today, the species interactions that determine whether a given mixture will be more productive than the corresponding monocultures are still poorly understood. Our objective was to assess the performance of fast-growing trees, i.e. poplar (Populus nigra × P. deltoides) and alder (Alnus glutinosa), in association with herbaceous species either N2-fixing species (succession alfalfa (Medicago sativa) and clover (Trifolium pratense)) or graminoids (succession of wheat (Triticum aestivum) – triticale (Triticosecale) – temporary grassland consisting of mixtures of perennial ryegrass (Lolium perenne) and fescue (Festuca ovina)), respectively, and in association together. We compared tree growth in mixed stands to growth in the respective tree monocultures. An experimental plantation composed of three blocks including the different treatments was set up in 2014 in northeastern France. In the forest mixture, poplar and alder were planted in alternating rows, and in the agroforestry plots, every second line of trees was replaced by the crops. No fertilizers (of any kind) were used during the experiments. During six growing seasons, tree growth (height and diameter at breast height) was monitored monthly in the agroforestry stands, the forest mixture stand and the two tree monocultures. By the end of 2019, poplar stem height in association with N2-fixing crops (alfalfa, then clover) was higher than in the forest mixture and the monoculture. During the warmest growing season with a marked dry period in June-July (2018), poplar height growth rate in the agroforestry treatment was between three and five times higher than for the poplars in the monoculture and the forest mixture. A facilitation process in the agroforestry plantations could explain this result due to a significant enrichment of the soil in nitrogen by the N2-fixing crops. This result only appeared several years after tree planting, and management actions were necessary in order to control the strong competition between crops and trees during the early stages. In the forest mixture, poplars associated with alders were smaller than in their monoculture, in spite of a stratification of the canopies of the two species. For alders, tree growth did not appear to be affected by either an association with graminoids or with poplar.