Use of artificial trees to assess dry deposition in spruce stands

International audienc

Effects of the clear-cutting of a Douglas-fir plantation (Pseudotsuga menziesii F.) on the chemical composition of soil solutions and on the leaching of DOC and ions in drainage waters

The effects of the clear-cutting of a 70-year-old Douglas-fir plantation on the chemical composition of soil solutions and on leaching of nutrients in drainage waters were observed by a continuous monitoring, six years before and three years after the cutting. Forest harvesting was made with very limited soil disturbances. Results showed that the concentration of weakly fixed solutions did not change but that the concentration of gravitational solutions of the upper soil layers drastically fell down after the cutting. The limited increase in nutrients leached with drainage waters was only due to the increase in the water flux, which is difficult to quantify because of the presence of ground vegetation. The monitoring of numerous fluxes before and after the clear-cutting could explain the specific behaviour of the soil solutions. The limited losses of nutrients the after clear-cutting in a potentially responsive ecosystem were unexpected. The initial hypothesis was that the decrease in the mineralization and nitrification rates observed after the cutting was related to a stimulating effect of Douglas-fir on the activity of soil nitrifyers.Effet de la coupe à blanc d'un peuplement de Douglas (Pseudotsuga menziesii F.) sur la composition chimique des solutions du sol et sur le flux d'éléments drainés. Les effets de la coupe à blanc d'une plantation de Douglas de 70 ans ont été observés sur la composition chimique des solutions du sol et les pertes d'éléments par drainage, par un suivi mensuel pendant 6 ans avant, et 3 ans après la coupe. L'exploitation du peuplement a été réalisée avec une perturbation minimum du sol. Les résultats montrent que les solutions liées ont peu évolué après la coupe, alors que le changement des solutions libres a été drastique dans les horizons de surface du sol. Malgré des incertitudes sur le rôle de la végétation spontanée, le drainage d'éléments n'a pas fortement augmenté après la coupe. La prise en compte de l'ensemble des flux mesurés dans cette étude semble pouvoir expliquer les observations. Les pertes limitées après la coupe d'une plantation où l'activité nitrifiante était élevée avant la coupe étaient inattendues. L'hypothèse avancée est l'arrêt du contrôle stimulateur des populations nitrifiantes du sol après la coupe du Douglas

Nutrient budgets for a rotation of a Douglas-fir plantation in the Beaujolais (France) based on a chronosequence study

International audienc

Influence d'un stress hydrique sur la dynamique des élements minéraux dans la sève xylèmique d'un peuplement d'Epicea. Conséquences sur l'apparition des carences minérales des peuplements d'Epicea dépérissants

National audienc

Magnesium Isotope Variations to Trace Liming Input to Terrestrial Ecosystems: A Case Study in the Vosges Mountains

International audienceLiming with Ca and Mg carbonates is commonly used to reduce soil and stream acidity and to improve vegetation growth and nutrition in forests. Ten years ago, dolomite lime was experimentally applied to a forest catchment on granite in the Vosges Mountains (northeast France), which is characterized by acid soils and drained by an acid stream. The average Mg isotope composition of the dolomite lime (-1.75%) was low compared with that of tree foliage (-0.70%), granite and deep soil layers (-0.40%), and stream water (-0.80%) in the control catchment. After liming, the exchangeable Mg concentrations in surface soil layers, which were initially very low, increased, and the Mg isotope composition decreased (up to -0.60%). The decrease was smaller in deeper layers but not in proportion to the increase in exchangeable Mg content, suggesting contributions from mineralization of organic matter and/or displacement of exchangeable Mg from surface layers. Before application, Mg concentration in beech and fir leaves was low, and that of 1-yr-old fir needles was lower than that in current needles. Internal Mg translocation within fir needles also resulted in a lower delta Mg-26 of older needles. Three years after dolomite application, the Mg isotope composition of plant leaves was lower than that in the control catchment; this decrease (up to -1.00%) was attributed to direct uptake of Mg from dissolving dolomite. Liming doubled the concentration of Mg in the stream, whereas the Mg isotope composition decreased correspondingly from -0.80 to -1.20%, indicating a fast transfer of dolomite Mg to the stream. Our findings indicate that monitoring of delta Mg-26 may be a promising tool to study the fate of dolomitic inputs in terrestrial and aquatic ecosystems

Understanding the behavior of the Basse de Courbeligne (Vosges, North-East France)

International audienceThe aim of the project is to be able, ultimately, to model the behavior of the Basse de Courbeligne headstream in response to climate change and anthropogenic pressure (reduction of air pollution, forest management). The Basse de Courbeligne is a headstream flowing on sandstone (mainly Buntsandstein) in the Vosges Mountains (North-East France). Since 2002, the water quality (pH, conductivity, major anions and cations) in its upper section has been monitored monthly within the framework of the Vosges Acidification Observatory (https://deims.org/22915474-7c50-47c1-8239-6c59fa924a1b). Its pH is acidic (5.5, standard deviation (S.D.) = 0.7), its conductivity is low (16.4 µS/cm, S.D. = 5.7µS/cm) and its average concentration in dissolved aluminum is around 240 µg/L (S.D. 125 µg/L) (period 2012-2021). At the headstream source, the aluminum concentration can reach 540 µg/L.In 2016 three plots have been set up on the right steep bank and instrumented to monitor the surface runoff water quality. The pH of each plot runoff is slightly higher than the headstream pH, the conductivity being similar. The main difference with the headstream lies in the dissolved aluminum concentration, which is much lower: 60 to 80 µg/L (S.D. = 50 µg/L) between 2017 and now. In the future, these plots will be submitted to different forest management protocols. Recently the downstream section of the Basse de Courbeligne has been investigated, as an expansion of the monitoring of the headstream to its full watershed is desirable: it has been noticed that the water pH at the watershed outlet (i.e. confluence with the Gentil Sapin stream) might be much more neutral (around 7). A detailed survey of the stream has been done concerning its water quality as well as the watershed geology and soil characteristics. The combined effect of a fault and of lateral springs are playing key roles in the stream flow and its water quality.After summarizing the long-term water quality data collected on the watershed, a first attempt to model its behavior using HYPE will be proposed

The MYB transcription factor emission of methyl anthranilate 1 stimulates emission of methyl anthranilate from Medicago truncatula hairy roots

Plants respond to herbivore or pathogen attacks by activating specific defense programs that include the production of bioactive specialized metabolites to eliminate or deter the attackers. Volatiles play an important role in the interaction of a plant with its environment. Through transcript profiling of jasmonate-elicited Medicago truncatula cells, we identified Emission of Methyl Anthranilate (EMA) 1, a MYB transcription factor that is involved in the emission of the volatile compound methyl anthranilate when expressed in M. truncatula hairy roots, giving them a fruity scent. RNA sequencing (RNA-Seq) analysis of the fragrant roots revealed the upregulation of a methyltransferase that was subsequently characterized to catalyze the O-methylation of anthranilic acid and was hence named M. truncatula anthranilic acid methyl transferase (MtAAMT) 1. Given that direct activation of the MtAAMT1 promoter by EMA1 could not be unambiguously demonstrated, we further probed the RNA-Seq data and identified the repressor protein M. truncatula plant AT-rich sequence and zinc-binding (MtPLATZ) 1. Emission of Methyl Anthranilate 1 binds a tandem repeat of the ACCTAAC motif in the MtPLATZ1 promoter to transactivate gene expression. Overexpression of MtPLATZ1 in transgenic M. truncatula hairy roots led to transcriptional silencing of EMA1, indicating that MtPLATZ1 may be part of a negative feedback loop to control the expression of EMA1. Finally, application of exogenous methyl anthranilate boosted EMA1 and MtAAMT1 expression dramatically, thus also revealing a positive amplification loop. Such positive and negative feedback loops seem to be the norm rather than the exception in the regulation of plant specialized metabolism.NDG, TM, YB and AGh are indebted to the Agency for Innovation by Science and Technology, the VIB International PhD Fellowship Program, the Chinese Scholarship Council (CSC), and the Iranian Ministry for Health and Medical Education, respectively, for pre-doctoral fellowships, and the Research Foundation Flanders (FWO) with a research project grant to AG (G004515N) and a postdoctoral fellowship to JP

The MYB transcription factor Emission of Methyl Anthranilate 1 stimulates emission of methyl anthranilate from Medicago truncatula hairy roots

Plants respond to herbivore or pathogen attacks by activating specific defense programs that include the production of bioactive specialized metabolites to eliminate or deter the attackers. Volatiles play an important role in the interaction of a plant with its environment. Through transcript profiling of jasmonate‐elicited Medicago truncatula cells we identified Emission of Methyl Anthranilate (EMA) 1, a MYB transcription factor that is involved in the emission of the volatile compound methyl anthranilate when expressed in M. truncatula hairy roots, giving them a fruity scent. RNA‐Seq analysis of the fragrant roots revealed the upregulation of a methyltransferase that was subsequently characterized to catalyze the O‐methylation of anthranilic acid and was hence named M. truncatula Anthranilic Acid Methyl Transferase (MtAAMT) 1. Given that direct activation of the MtAAMT1 promoter by EMA1 could not be unambiguously demonstrated, we further probed the RNA‐Seq data and identified the repressor protein M. truncatula Plant AT‐rich sequence and Zinc‐binding (MtPLATZ) 1. EMA1 binds a tandem repeat of the ACCTAAC motif in the MtPLATZ1 promoter to transactivate gene expression. Overexpression of MtPLATZ1 in transgenic M. truncatula hairy roots led to transcriptional silencing of EMA1, indicating that MtPLATZ1 may be part of a negative feedback loop to control the expression of EMA1. Finally, exogenous methyl anthranilate application boosted EMA1 and MtAAMT1 expression dramatically, thus also revealing a positive amplification loop. Such positive and negative feedback loops seem to be a norm rather than an exception in the regulation of plant specialized metabolism