Ajouter le résultat dans votre panier Visionner les documents numériques Affiner la recherche Interroger des sources externes
Etendre la recherche sur niveau(x) vers le bas
Annual net nitrogen mineralization and litter flux in well-drained downy birch, Norway spruce and Scots pine forest ecosystems / Hardo Becker in Silva fennica, vol 52 n° 4 (September 2018)
Titre : Annual net nitrogen mineralization and litter flux in well-drained downy birch, Norway spruce and Scots pine forest ecosystems Type de document : Article/Communication Auteurs : Hardo Becker, Auteur ; Jürgen Aosaar, Auteur ; Mats Varik, Auteur ; Gunnar Morozov, Auteur ; et al., Auteur Année de publication : 2018 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Végétation
[Termes descripteurs IGN] azote
[Termes descripteurs IGN] betula pubescens
[Termes descripteurs IGN] forêt marécageuse
[Termes descripteurs IGN] nitrification
[Termes descripteurs IGN] Picea abies
[Termes descripteurs IGN] Pinus sylvestris
[Termes descripteurs IGN] sol forestier
Résumé : (Auteur) The main aim of the current study was to estimate the annual net nitrogen mineralization (NNM) flux in stands of different tree species growing on drained peatlands, as well as to clarify the effect of tree species, soil properties and litter on annual NNM dynamics. Three study sites were set up in May 2014: a downy birch (Betula pubescens Ehrh.) stand and a Norway spruce (Picea abies (L.) Karst.) stand in Oxalis full-drained swamp (ODS) and a Scots pine (Pinus sylvestris L.) stand in Myrtillus full-drained swamp (MDS). The NNM flux was estimated using the in situ method with incubated polyethylene bags. The highest value of NNM was found in stands that were growing on fertile ODS: 127.5 kg N ha–1 yr–1 and 87.7 kg N ha–1 yr–1, in the downy birch stand and in the Norway spruce stand, respectively. A significantly lower annual NNM flux (11.8 kg N ha–1 yr–1) occurred in the Scots pine stand growing in MDS. Nitrification was highest at fertile ODS sites and ammonification was the highest at the low fertility MDS site. For all study sites, positive correlation was found between soil temperature and NNM intensity. The difference in annual NNM between the downy birch stand and the Norway spruce stand growing on similar drained fertile peatlands was due to litter quality. The annual N input into the soil through leaf litter was the highest at the downy birch site where also the C/N ratio of litter was the lowest. The second highest N input into the soil was found in the spruce stand and the lowest in the pine stand. Numéro de notice : A2018-506 Thématique : FORET Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.14214/sf.10013 date de publication en ligne : 27/09/2018 En ligne : https://doi.org/10.14214/sf.10013 Format de la ressource électronique : URL article Permalink :
in Silva fennica > vol 52 n° 4 (September 2018)[article]Study and mitigation of calibration factor instabilities in a water vapor Raman lidar / Leslie David in Atmospheric measurement techniques, vol 10 n° 7 (July 2017)
Titre : Study and mitigation of calibration factor instabilities in a water vapor Raman lidar Type de document : Article/Communication Auteurs : Leslie David, Auteur ; Olivier Bock , Auteur ; Christian Thom , Auteur ; Pierre Bosser , Auteur ; Jacques Pelon, Auteur Année de publication : 2017 Projets : VEGA (LEFE/INSU) / Article en page(s) : pp 2745 - 2758 Note générale : bibliographie
This work was developed in the framework of project VEGA and supported by the French national program LEFE/INSU.
Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Atmosphère
[Termes descripteurs IGN] azote
[Termes descripteurs IGN] étalonnage d'instrument
[Termes descripteurs IGN] fibre optique
[Termes descripteurs IGN] lidar Raman
[Termes descripteurs IGN] retard troposphérique
[Termes descripteurs IGN] vapeur d'eau
Résumé : (auteur) We have investigated calibration variations in the Rameau water vapor Raman lidar. This lidar system was developed by the Institut National de l'Information Géographique et Forestière (IGN) together with the Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS). It aims at calibrating Global Navigation Satellite System (GNSS) measurements for tropospheric wet delays and sounding the water vapor variability in the lower troposphere. The Rameau system demonstrated good capacity in retrieving water vapor mixing ratio (WVMR) profiles accurately in several campaigns. However, systematic short-term and long-term variations in the lidar calibration factor pointed to persistent instabilities. A careful testing of each subsystem independently revealed that these instabilities are mainly induced by mode fluctuations in the optic fiber used to couple the telescope to the detection subsystem and by the spatial nonuniformity of the photomultiplier photocathodes. Laboratory tests that replicate and quantify these instability sources are presented. A redesign of the detection subsystem is presented, which, combined with careful alignment procedures, is shown to significantly reduce the instabilities. Outdoor measurements were performed over a period of 5 months to check the stability of the modified lidar system. The calibration changes in the detection subsystem were monitored with lidar profile measurements using a common nitrogen filter in both Raman channels. A short-term stability of 2–3 % and a long-term drift of 2–3 % per month are demonstrated. Compared to the earlier Development of Methodologies for Water Vapour Measurement (DEMEVAP) campaign, this is a 3-fold improvement in the long-term stability of the detection subsystem. The overall water vapor calibration factors were determined and monitored with capacitive humidity sensor measurements and with GPS zenith wet delay (ZWD) data. The changes in the water vapor calibration factors are shown to be fairly consistent with the changes in the nitrogen calibration factors. The nitrogen calibration results can be used to correct the overall calibration factors without the need for additional water vapor measurements to within 1 % per month. Numéro de notice : A2017-868 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.5194/amt-10-2745-2017 date de publication en ligne : 31/07/2017 En ligne : https://doi.org/10.5194/amt-10-2745-2017 Format de la ressource électronique : URL article Permalink :
in Atmospheric measurement techniques > vol 10 n° 7 (July 2017) . - pp 2745 - 2758[article]
Study and mitigation of calibration ... - pdf éditeurAdobe Acrobat PDF
Biodiversity effects on ecosystem functioning in a 15-year grassland experiment: patterns, mechanisms, and open questions / Wolfgang W. Weisser in Basic and Applied Ecology, vol ([26/06/2017])
Titre : Biodiversity effects on ecosystem functioning in a 15-year grassland experiment: patterns, mechanisms, and open questions Type de document : Article/Communication Auteurs : Wolfgang W. Weisser, Auteur ; Christiane Roscher, Auteur ; Sebastian Meyer, Auteur ; et al., Auteur Année de publication : 2017 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Ecologie
[Termes descripteurs IGN] azote
[Termes descripteurs IGN] biomasse
[Termes descripteurs IGN] carbone
[Termes descripteurs IGN] écosystème
[Termes descripteurs IGN] gaz à effet de serre
[Termes descripteurs IGN] nutriment
[Termes descripteurs IGN] placette d'échantillonnage
[Termes descripteurs IGN] potassium
[Termes descripteurs IGN] puits de carbone
[Termes descripteurs IGN] richesse floristique
[Termes descripteurs IGN] sol
[Termes descripteurs IGN] stabilité
Résumé : (auteur) In the past two decades, a large number of studies have investigated the relationship between biodiversity and ecosystem functioning, most of which focussed on a limited set of ecosystem variables. The Jena Experiment was set up in 2002 to investigate the effects of plant diversity on element cycling and trophic interactions, using a multi-disciplinary approach. Here, we review the results of 15 years of research in the Jena Experiment, focussing on the effects of manipulating plant species richness and plant functional richness. With more than 85,000 measures taken from the plant diversity plots, the Jena Experiment has allowed answering fundamental questions important for functional biodiversity research.
First, the question was how general the effect of plant species richness is, regarding the many different processes that take place in an ecosystem. About 45% of different types of ecosystem processes measured in the ‘main experiment’, where plant species richness ranged from 1 to 60 species, were significantly affected by plant species richness, providing strong support for the view that biodiversity is a significant driver of ecosystem functioning. Many measures were not saturating at the 60-species level, but increased linearly with the logarithm of species richness. There was, however, great variability in the strength of response among different processes. One striking pattern was that many processes, in particular belowground processes, took several years to respond to the manipulation of plant species richness, showing that biodiversity experiments have to be long-term, to distinguish trends from transitory patterns. In addition, the results from the Jena Experiment provide further evidence that diversity begets stability, for example stability against invasion of plant species, but unexpectedly some results also suggested the opposite, e.g. when plant communities experience severe perturbations or elevated resource availability. This highlights the need to revisit diversity-stability theory.
Second, we explored whether individual plant species or individual plant functional groups, or biodiversity itself is more important for ecosystem functioning, in particular biomass production. We found strong effects of individual species and plant functional groups on biomass production, yet these effects often occurred mostly in addition to, but not instead of, effects of plant species richness.
Third, the Jena Experiment assessed the effect of diversity on multitrophic interactions. The diversity of most organisms responded positively to increases in plant species richness, and the effect was stronger for above- than for belowground organisms, and stronger for herbivores than for carnivores or detritivores. Thus, diversity begets diversity. In addition, the effect on organismic diversity was stronger than the effect on species abundances.
Fourth, the Jena Experiment aimed to assess the effect of diversity on N, P and C cycling and the water balance of the plots, separating between element input into the ecosystem, element turnover, element stocks, and output from the ecosystem. While inputs were generally less affected by plant species richness, measures of element stocks, turnover and output were often positively affected by plant diversity, e.g. carbon storage strongly increased with increasing plant species richness. Variables of the N cycle responded less strongly to plant species richness than variables of the C cycle.
Fifth, plant traits are often used to unravel mechanisms underlying the biodiversity-ecosystem functioning relationship. In the Jena Experiment, most investigated plant traits, both above- and belowground, were plastic and trait expression depended on plant diversity in a complex way, suggesting limitation to using database traits for linking plant traits to particular functions.
Sixth, plant diversity effects on ecosystem processes are often caused by plant diversity effects on species interactions. Analyses in the Jena Experiment including structural equation modelling suggest complex interactions that changed with diversity, e.g. soil carbon storage and greenhouse gas emission were affected by changes in the composition and activity of the belowground microbial community. Manipulation experiments where particular organisms, e.g. belowground invertebrates, were excluded from plots in split-plot experiments, supported the important role of the biotic component for element and water fluxes.
Seventh, the Jena Experiment aimed to put the results into the context of agricultural practices in managed grasslands. The effect of increasing plant species richness from 1 to 16 species on plant biomass was, in absolute terms, as strong as the effect of a more intensive grassland management, using fertiliser and increasing mowing frequency. Potential bioenergy production from high-diversity plots was similar to that of conventionally used energy crops. These results suggest that diverse ‘High Nature Value Grasslands’ are multifunctional and can deliver a range of ecosystem services including production-related services.
A final task was to assess the importance of potential artefacts in biodiversity–ecosystem functioning relationships, caused by the weeding of the plant community to maintain plant species composition. While the effort (in hours) needed to weed a plot was often negatively related to plant species richness, species richness still affected the majority of ecosystem variables. Weeding also did not negatively affect monoculture performance; rather, monocultures deteriorated over time for a number of biological reasons, as shown in plant-soil feedback experiments.
To summarize, the Jena Experiment has allowed for a comprehensive analysis of the functional role of biodiversity in an ecosystem. A main challenge for future biodiversity research is to increase our mechanistic understanding of why the magnitude of biodiversity effects differs among processes and contexts. It is likely that there will be no simple answer. For example, among the multitude of mechanisms suggested to underlie the positive plant species richness effect on biomass, some have received limited support in the Jena Experiment, such as vertical root niche partitioning. However, others could not be rejected in targeted analyses. Thus, from the current results in the Jena Experiment it seems likely that the positive biodiversity effect results from several mechanisms acting simultaneously in more diverse communities, such as reduced pathogen attack, the presence of more plant growth promoting organisms, less seed limitation, and increased trait differences leading to complementarity in resource uptake. Distinguishing between different mechanisms requires careful testing of competing hypotheses. Biodiversity research has matured such that predictive approaches testing particular mechanisms are now possible.
Numéro de notice : A2017-352 Thématique : BIODIVERSITE/FORET Nature : Article DOI : 10.1016/j.baae.2017.06.002 En ligne : https://doi.org/10.1016/j.baae.2017.06.002 Format de la ressource électronique : URL article Permalink :
in Basic and Applied Ecology > vol [26/06/2017][article]Plant community mycorrhization in temperate forests and grasslands: relations with edaphic properties and plant diversity / Maret Gerz in Journal of vegetation science, vol 27 n° 1 (January 2016)
Titre : Plant community mycorrhization in temperate forests and grasslands: relations with edaphic properties and plant diversity Type de document : Article/Communication Auteurs : Maret Gerz, Auteur ; Carlos Guillermo Bueno, Auteur ; Martin Zobel, Auteur ; Mari Moora, Auteur Année de publication : 2016 Article en page(s) : pp 89 - 99 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes descripteurs IGN] azote
[Termes descripteurs IGN] biodiversité végétale
[Termes descripteurs IGN] ectomycorhize
[Termes descripteurs IGN] Estonie
[Termes descripteurs IGN] forêt tempérée
[Termes descripteurs IGN] humidité du sol
[Termes descripteurs IGN] prairie
[Vedettes matières IGN] Ecologie forestière
Résumé : (auteur) Questions : Mycorrhizal symbiosis plays a key role in plant communities. Its prevalence in plant communities (mycorrhization) at larger spatial scales has so far been mostly qualitative, while quantitative studies incorporating the mycorrhizal traits of plant species are scarce. This study aims to: (1) determine the variation in general and arbuscular mycorrhization in temperate forests and grasslands, (2) study the effects of soil N, pH and moisture on mycorrhization, and (3) determine the relationships between mycorrhization and plant diversity.
Location : Temperate forests and grasslands in Estonia, Northern Europe.
Methods : To quantify mycorrhization we used a plant community mycorrhization index – community mean of mycorrhizal status weighted by plant species abundances. The effects of edaphic factors characterized by cumulative Ellenberg values on mycorrhization were analysed using linear mixed models, and the relationship between mycorrhization and diversity was evaluated with partial correlation and variance partitioning.
Results : General mycorrhization was higher in forests and lower in grasslands, opposite to arbuscular mycorrhization. Soil N, pH and moisture negatively impacted general mycorrhization, whereas arbuscular mycorrhization was positively affected by soil pH and negatively by soil N and moisture. Plant species richness was negatively correlated with general mycorrhization in forests, whereas arbuscular mycorrhization was positively associated with plant species richness, Shannon and Simpson indices in forests and across ecosystems.
Conclusions : Mycorrhization is highly dependent on soil conditions and related to plant diversity, showing its importance for vegetation science. The plant community mycorrhization index used in this study is a promising tool for quantifying the prevalence of mycorrhizal symbiosis along environmental gradients.
Numéro de notice : A2016-361 Thématique : BIODIVERSITE/FORET Nature : Article En ligne : http://dx.doi.org/10.1111/jvs.12338 Format de la ressource électronique : URL article Permalink :
in Journal of vegetation science > vol 27 n° 1 (January 2016) . - pp 89 - 99[article]Phosphorus nutrition of beech (Fagus sylvatica L.) is decreasing in Europe / Ulrike Talkne in Annals of Forest Science [en ligne], vol 72 n° 7 (october 2015)
Titre : Phosphorus nutrition of beech (Fagus sylvatica L.) is decreasing in Europe Type de document : Article/Communication Auteurs : Ulrike Talkne, Auteur ; Karl Josef Meiwes, Auteur ; Nenad Potočić, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 919 - 928 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes descripteurs IGN] azote
[Termes descripteurs IGN] croissance végétale
[Termes descripteurs IGN] défoliation
[Termes descripteurs IGN] Fagus (genre)
[Termes descripteurs IGN] phosphore
[Termes descripteurs IGN] placette d'échantillonnage
[Termes IFN] acidité des sols
[Termes IFN] nutriment végétal
[Vedettes matières IGN] Végétation et changement climatique
Résumé : (auteur) Key message : Foliar phosphorus concentrations have decreased in Europe during the last 20 years. High atmospheric nitrogen deposition and climate change might be responsible for this trend. Continued decrease in foliar P concentrations might lead to reduced growth and vitality of beech forests in Europe.
Context : Increased forest soil acidification, atmospheric nitrogen deposition, and climate change have been shown to affect phosphorus nutrition of forest trees. Low foliar phosphorus levels and high nitrogen/phosphorus ratios have been observed in different European countries and have been related to reduced growth in forests.
Aims : We test the hypothesis that phosphorus concentrations of European beech (F. sylvatica L.) foliage are decreasing at the European scale.
Methods : Foliar phosphorus concentrations in beech were monitored on the basis of the “International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests.” Here, data from 12 European countries, comprising 79 plots and a 20-year sampling period (1991–2010), were evaluated.
Results : Foliar phosphorus concentrations ranged from 0.81 to 1.66 mg g−1 dw (plot median of the 20-year sampling period). On 22 % of the plots, phosphorus concentrations were in the deficiency range of beech (Mellert and Göttlein 2012). On 62 % of the plots, the nitrogen/phosphorus ratio was above 18.9, which is considered to be disharmonious for beech. In addition, foliar phosphorus concentrations were significantly decreasing by, on average, 13 % from 1.31 to 1.14 mg g−1 in Europe (p Conclusion : Our results show that phosphorus nutrition of beech is impaired in Europe. Possible drivers of this development might be high atmospheric nitrogen deposition and climate change. Continued decrease in foliar phosphorus concentrations, eventually attaining phosphorus deficiency levels, might lead to reduced growth and vitality of beech forests in Europe.
Numéro de notice : A2015-719 Thématique : FORET Nature : Article En ligne : http://link.springer.com/article/10.1007/s13595-015-0459-8/fulltext.html Format de la ressource électronique : URL article Permalink :
in Annals of Forest Science [en ligne] > vol 72 n° 7 (october 2015) . - pp 919 - 928[article]Variables related to nitrogen deposition improve defoliation models for European forests / Marco Ferretti in Annals of Forest Science [en ligne], vol 72 n° 7 (october 2015)PermalinkPrediction of the presence of topsoil nitrogen from spaceborne hyperspectral data / Binny Gopal in Geocarto international, vol 30 n° 1 - 2 (January - February 2015)PermalinkNon-linear partial least square regression increases the estimation accuracy of grass nitrogen and phosphorus using in situ hyperspectral and environmental data / A. Ramoelo in ISPRS Journal of photogrammetry and remote sensing, vol 82 (August 2013)PermalinkUne évaluation spatiale des risques agro-environnementaux par une modélisation multicritère combinée avec la méthode PIXAL / Francis Macary in Revue internationale de géomatique, vol 23 n° 1 (mars - mai 2013)PermalinkLandscape controls over major nutrients and primary productivity of Arctic lakes / P. Pathak in Cartography and Geographic Information Science, vol 39 n° 4 (October 2012)PermalinkSpatial variability of soil nutrients and GIS-based nutrient management in Yongji County, China / Qian Zhang in International journal of geographical information science IJGIS, vol 24 n°7-8 (july 2010)PermalinkUsing landscape characteristics to define an adjusted distance metric for improving kriging interpolations / S. Lyon in International journal of geographical information science IJGIS, vol 24 n° 5-6 (may 2010)PermalinkEffects of stand density on ecosystem properties of subalpine forests in the southern Rocky Mountains, USA / Sharon J. Hall ; Peter J. Marchand in Annals of Forest Science, vol 67 n° 1 (January-February 2010)PermalinkRetrieval of dissolved inorganic nitrogen from multi-temporal MODIS data in Haizhou Bay / Y. Xu in Marine geodesy, vol 33 n° 1 (January - March 2010)PermalinkNitrogen mineralization after clearcutting and residue management in a second rotation Eucalyptus globulus Labill. stand in Galicia (NW Spain) / Cristina Fernández in Annals of Forest Science, Vol 66 n° 8 (December 2009)Permalink