8 research outputs found
PropriĂ©tĂ©s fonctionnelles et spectrales dâespĂšces vĂ©gĂ©tales de tourbiĂšres ombrotrophes le long dâun gradient de dĂ©position dâazote
Les tourbieÌres ombrotrophes, ou bogs sont particulieÌrement vulneÌrables aÌ lâaugmentation de la deÌposition atmospheÌrique dâazote. Cet apport dâun nutriment normalement limitant alteÌre la capaciteÌ des tourbieÌres aÌ accumuler le carbone (C), en plus de mener aÌ des changements de leur composition veÌgeÌtale. Lâimagerie spectrale est une approche prometteuse puisquâelle rend possible la deÌtection des espeÌces veÌgeÌtales et de certaines caracteÌristiques chimiques des plantes, aÌ distance. Toutefois, lâampleur des diffeÌrences spectrales intra- et interespeÌces nâest pas encore connue. Nous avons eÌvalueÌ la façon dont la chimie, la structure et la signature spectrale des feuilles changent chez Chamaedaphne calyculata, Kalmia angustifolia, Rhododendron groenlandicum et Eriophorum vaginatum, dans trois tourbieÌres du sud du QueÌbec et de lâOntario, incluant une tourbieÌre ouÌ se deÌroule une expeÌrience de fertilisation aÌ long terme. Nous avons mesureÌ des changements dans les traits fonctionnels dus aux diffeÌrences dans la quantiteÌ dâazote disponible dans les sites. Toutefois, la deÌposition atmospheÌrique dâazote a eu relativement peu dâeffet sur les spectres foliaires ; les variations spectrales les plus importantes eÌtaient entre les espeÌces. En fait, nous avons trouveÌ que les quatre espeÌces ont un spectre caracteÌristique, une signature spectrale permettant leur identification au moyen dâanalyses discriminantes des moindres carreÌs partiels (PLSDA). De plus, nous avons reÌussi aÌ preÌdire plusieurs traits fonctionnels (lâazote, le carbone ; et la proportion dâeau et de matieÌre seÌche) avec moins de 10 % dâerreur graÌce aÌ des reÌgressions des moindres carreÌs partiels (PLSR) des donneÌes spectrales. Notre eÌtude fournit de nouvelles preuves que les variations intraspeÌcifiques, causeÌes en partie par des variations environnementales consideÌrables, sont perceptibles dans les spectres foliaires. Toutefois, les variations intraspeÌcifiques nâaffectent pas lâidentification des espeÌces ou la preÌdiction des traits. Nous deÌmontrons que les spectres foliaires comprennent des informations sur les espeÌces et leurs traits fonctionnels, confirmant le potentiel de la spectroscopie pour le suivi des tourbieÌres.Abstract
Bogs, as nutrient-poor ecosystems, are particularly sensitive to atmospheric nitrogen (N) deposition. Nitrogen deposition alters bog plant community composition and can limit their ability to sequester carbon (C). Spectroscopy is a promising approach for studying how N deposition affects bogs because of its ability to remotely determine changes in plant species composition in the long term as well as shorter-term changes in foliar chemistry. However, there is limited knowledge on the extent to which bog plants differ in their foliar spectral properties, how N deposition might affect those properties, and whether subtle inter- or intraspecific changes in foliar traits can be spectrally detected. Using an integrating sphere fitted to a field spectrometer, we measured spectral properties of leaves from the four most common vascular plant species (Chamaedaphne calyculata, Kalmia angustifolia, Rhododendron groenlandicum and Eriophorum vaginatum) in three bogs in southern QueÌbec and Ontario, Canada, exposed to different atmospheric N deposition levels, including one subjected to a 18 years N fertilization experiment. We also measured chemical and morphological properties of those leaves. We found detectable intraspecific changes in leaf structural traits and chemistry (namely chlorophyll b and N concentrations) with increasing N deposition and identified spectral regions that helped distinguish the site-specific populations within each species. Most of the variation in leaf spectral, chemical and morphological properties was among species. As such, species had distinct spectral foliar signatures, allowing us to identify them with high accuracy with partial least squares discriminant analyses (PLSDA). Predictions of foliar traits from spectra using partial least squares regression (PLSR) were generally accurate, particularly for the concentrations of N and C, soluble C, leaf water, and dry matter content (<10% RMSEP). However, these multi-species PLSR models were not accurate within species, where the range of values was narrow. To improve the detection of short-term intraspecific changes in functional traits, models should be trained with more species-specific data. Our field study showing clear differences in foliar spectra and traits among species, and some within-species differences due to N deposition, suggest that spectroscopy is a promising approach for assessing long-term vegetation changes in bogs subject to atmospheric pollution
Foliar spectra and traits of bog plants across nitrogen deposition gradients
Bogs, as nutrient-poor ecosystems, are particularly sensitive to atmospheric nitrogen (N) deposition. Nitrogen deposition alters bog plant community composition and can limit their ability to sequester carbon (C). Spectroscopy is a promising approach for studying how N deposition aïŹects bogs because of its ability to remotely determine changes in plant species composition in the long term as well as shorter-term changes in foliar chemistry. However, there is limited knowledge on the extent to which bog plants diïŹer in their foliar spectral properties, how N deposition might aïŹect those properties, and whether subtle inter- or intraspeciïŹc changes in foliar traits can be spectrally detected. The objective of the study was to assess the eïŹect of N deposition on foliar traits and spectra. UsinganintegratingsphereïŹttedtoaïŹeldspectrometer,wemeasuredspectralpropertiesof leavesfromthefourmostcommonvascularplantspecies(Chamaedaphnecalyculata,Kalmiaangustifolia, RhododendrongroenlandicumandEriophorumvaginatum)inthreebogsinsouthernQuĂ©becandOntario, Canada, exposed to diïŹerent atmospheric N deposition levels, including one subjected to a 18-year N fertilization experiment. We also measured chemical and morphological properties of those leaves. We found detectable intraspeciïŹc changes in leaf structural traits and chemistry (namely chlorophyll b and N concentrations) with increasing N deposition and identiïŹed spectral regions that helped distinguish the site-speciïŹc populations within each species. Most of the variation in leaf spectral, chemical, and morphological properties was among species. As such, species had distinct spectral foliar signatures, allowing us to identify them with high accuracy with partial least squares discriminant analyses (PLSDA). Predictions of foliar traits from spectra using partial least squares regression (PLSR) were generally accurate, particularly for the concentrations of N and C, soluble C, leafwater,anddrymattercontent(<10%RMSEP).However,thesemulti-speciesPLSRmodelswerenot accuratewithinspecies,wheretherangeofvalueswasnarrow. Toimprovethedetectionofshort-term intraspeciïŹc changes in functional traits, models should be trained with more species-speciïŹc data. Our ïŹeld study showing clear diïŹerences in foliar spectra and traits among species, and some within-speciesdiïŹerencesduetoNdeposition,suggestthatspectroscopyisapromisingapproachfor assessing long-term vegetation changes in bogs subject to atmospheric pollution
Foliar Spectra and Traits of Bog Plants across Nitrogen Deposition Gradients
Bogs, as nutrient-poor ecosystems, are particularly sensitive to atmospheric nitrogen (N) deposition. Nitrogen deposition alters bog plant community composition and can limit their ability to sequester carbon (C). Spectroscopy is a promising approach for studying how N deposition affects bogs because of its ability to remotely determine changes in plant species composition in the long term as well as shorter-term changes in foliar chemistry. However, there is limited knowledge on the extent to which bog plants differ in their foliar spectral properties, how N deposition might affect those properties, and whether subtle inter- or intraspecific changes in foliar traits can be spectrally detected. The objective of the study was to assess the effect of N deposition on foliar traits and spectra. Using an integrating sphere fitted to a field spectrometer, we measured spectral properties of leaves from the four most common vascular plant species (Chamaedaphne calyculata, Kalmia angustifolia, Rhododendron groenlandicum and Eriophorum vaginatum) in three bogs in southern Québec and Ontario, Canada, exposed to different atmospheric N deposition levels, including one subjected to a 18-year N fertilization experiment. We also measured chemical and morphological properties of those leaves. We found detectable intraspecific changes in leaf structural traits and chemistry (namely chlorophyll b and N concentrations) with increasing N deposition and identified spectral regions that helped distinguish the site-specific populations within each species. Most of the variation in leaf spectral, chemical, and morphological properties was among species. As such, species had distinct spectral foliar signatures, allowing us to identify them with high accuracy with partial least squares discriminant analyses (PLSDA). Predictions of foliar traits from spectra using partial least squares regression (PLSR) were generally accurate, particularly for the concentrations of N and C, soluble C, leaf water, and dry matter content (<10% RMSEP). However, these multi-species PLSR models were not accurate within species, where the range of values was narrow. To improve the detection of short-term intraspecific changes in functional traits, models should be trained with more species-specific data. Our field study showing clear differences in foliar spectra and traits among species, and some within-species differences due to N deposition, suggest that spectroscopy is a promising approach for assessing long-term vegetation changes in bogs subject to atmospheric pollution
Nouveaux regards sur lâĂ©ducation et la formation : contributions des jeunes chercheurs du CIDEF 2020
Ce numĂ©ro rassemble six travaux issus des cinquante communications orales et affichĂ©es du Colloque doctoral international de lâĂ©ducation et de la formation (CIDEF 2020), prĂ©sentĂ©es Ă distance les 27 et 28 octobre 2020. Si chacun de ces articles propose un Ă©clairage sur les enjeux pour lâĂ©ducation et la formation de demain, ils traitent cette thĂ©matique Ă partir dâobjets trĂšs diffĂ©rents et de mĂ©thodes variĂ©es : les politiques Ă©ducatives et les politiques de formation, les usagers de lâĂ©ducation et de la formation, ainsi que lâanalyse de pratiques. La complĂ©mentaritĂ© de ces travaux nous offre une vision large de la richesse offerte par cette discipline de recherche. Une premiĂšre partie rend compte de la rĂ©alitĂ© des pratiques lorsquâelles sont imposĂ©es institutionnellement et tĂ©moigne dâune volontĂ© de comprendre les modalitĂ©s dâenseignement et de formation actuelles. Dans le prolongement de ce travail, la deuxiĂšme partie de ce numĂ©ro propose des articles sâintĂ©ressant Ă des initiatives pĂ©dagogiques et interroge leurs effets sur les pratiques des professionnels de lâĂ©ducation et de la formation mais Ă©galement sur lâapprentissage des bĂ©nĂ©ficiaires. This issue offers six studies from the fifty oral and written presentations of the International Doctoral Conference on Education (CIDEF 2020), presented online on 27 and 28 October 2020. While each of these articles sheds light on the challenges for tomorrow's education, they deal with this theme from very different objects and methods: educational policies, users of education, as well as the analysis of practices. The complementarity of this work offers us a broad vision of the richness offered by this research discipline. A first part reflects the reality of practices when they are imposed institutionally and shows a desire to understand current teaching methods. As an extension of this work, the second part of this issue offers articles on pedagogical initiatives. It also questions their effects on the practices of education professionals but also on the learning of beneficiaries