Le rapport spécial du GIEC (SR1.5) publié en octobre 2018 est sans équivoque. Avec un réchauffement global d'environ 1°C en 2017 par rapport au début de l'ère industrielle et une teneur de CO2 dans l'atmosphère de 400 parties par million, l'Homme a d'ores et déjà modifié substantiellement le climat. L'évaluation de scénarios climatiques à bas niveau d'émissions limitant le réchauffement global à venir en deçà de 2°C montre que nous sommes désormais face à un défi scientifique, technique et civilisationnel sans précédent. Le GIEC stipule que chaque année perdue en matière d'atténuation rend un peu plus plausible la perspective d'une véritable "catastrophe" climatique. Dans ce contexte alarmant, les techniques de modification du rayonnement solaire sont de plus en plus étudiées comme une alternative à court terme pouvant limiter les impacts liés à la hausse de la température globale, en attendant la mise en œuvre et/ou la faisabilité de techniques d'atténuation suffisamment efficaces. La modélisation du système Terre reste à ce jour le seul moyen d'étudier dans quelles mesures ces techniques pourraient effectivement s'insérer dans la lutte contre le changement climatique. Le but principal de cette thèse est de quantifier et de réduire les incertitudes quant à la réponse des modèles aux simulations de géo-ingénierie de type modification du rayonnement solaire, en accordant une attention toute particulière aux effets collatéraux sur les cycles de l'eau et du carbone. Dans un premier temps, nous avons exploité les simulations existantes du projet GeoMIP, et avons identifié une relation statistique émergente entre le refroidissement obtenu dans les simulations de modification du rayonnement solaire, et le refroidissement induit par les éruptions volcaniques majeures dans les simulations historiques. Sur la base de plusieurs jeux d'observations, nous avons évalué la réponse des modèles aux éruptions et ainsi contraint la réponse à la modification du rayonnement solaire, réduisant son efficacité potentielle de 20% et l'incertitude associée de 40%. Par la suite, nous nous sommes intéressés à la réponse du cycle du carbone et avons montré que les changements climatiques induits par cette forme de géo-ingénierie tendent à stimuler les puits de carbone continentaux et océaniques. Nous avons cependant pointé l'incertitude qui entoure les processus responsables de cette augmentation, et également la réversibilité du cycle du carbone en cas d'arrêt de la géo-ingénierie. Malgré le renforcement des puits naturels de carbone, ce dernier résultat confirme que cette forme de géo-ingénierie ne peut être considérée comme une technique d'atténuation du fait de la non pérennité du stockage additionnel des émissions anthropiques de carbone dans les réservoirs océanique et terrestre. Enfin, nous nous sommes intéressés à d'autres sources d'incertitudes, liées au choix du protocole expérimental ou du modèle mis en oeuvre. Nous avons en particulier mis en lumière l’influence potentielle de la stratosphère et de son couplage avec la circulation troposphérique sur la réponse régionale des modèles à nos latitudes. / The IPCC Special Report (SR1.5) published in October 2018 is unequivocal. Global warming reached 1°C above preindustrial level in 2017 and atmospheric concentrations of CO2 passed 400 parts per million. Human activities have already substantially altered the Earth's climate. The assessment of low emission scenarios that limit global warming to 2°C above preindustrial levels shows that we are now facing an unprecedented scientific, technological and civilizational challenge, and stipulates that each year lost for mitigation makes the prospect of a real climate "disaster" a little more plausible. In this alarming context, solar radiation modification techniques are increasingly studied as a short-term alternative in order to limit the impacts of dangerous global warming, before the implementation and/or feasibility of sufficiently effective mitigation techniques. Earth System Models remain the only tool to investigate the extent to which these techniques could be used to counteract global warming. The main purpose of this thesis is to quantify and narrow uncertainties in model response to geoengineering simulations such as solar radiation modification, with special attention to side-effects on water and carbon cycles. First, we have used available simulations from GeoMIP, and identified an emerging statistical link between the cooling obtained in solar radiation management simulations, and the cooling induced by major volcanic eruptions in the historical simulations. Using several observational datasets, we have evaluated the model response to volcanic eruptions and, thereby, constrained the response to this geoengineering technique, reducing its potential cooling efficiency by 20%, and the associated uncertainty by 40%. Subsequently, we have focused on the carbon cycle response and have shown that climatic changes induced by this form of geoengineering tends to stimulate continental and oceanic carbon sinks. However, we have pointed out the uncertainty surrounding the processes responsible for this increase, and also the reversibility of the carbon cycle in case of stopping geoengineering. Despite the enhancement of the natural carbon sinks, this last result confirms that this form of geoengineering cannot be considered as a mitigation technique because of the unsustainability of the additional storage of anthropogenic carbon emissions into ocean and terrestrial reservoirs. Finally, we have looked at other sources of uncertainty related to the choice of the implemented experiment design or model. We have in particular highlighted the potentiel influence of the stratosphere and its coupling with the tropospheric dynamics on the regional response in the northern midlatitudes.

The response of the tropical Atlantic Ocean to wind stress forcing on seasonal and interannual time scales is examined using an ocean data assimilation product from the Geophysical Fluid Dynamics Laboratory (GFDL), and an ocean general circulation model which incorporates a three dimensional flux correction technique to correct biases of the mean state of the ocean. On a seasonal time scale, we investigated the impact of the annual migration of the ITCZ on the exchange pathways of the northern tropical Atlantic. The results indicate that seasonal variation of the zonal slope of the thermal ridge along the boundary between the north equatorial countercurrent and north equatorial current in response to changes in the ITCZ controls, to a large extent, the amount of water participating in the equatorial circulation. These changes can be explained in terms of a simple dynamical model where local Ekman pumping dominates thermocline variation in the western part of the basin, and Rossby wave adjustment comes into play in the eastern basin. On an interannual time scale, we examined the upper heat budget of the equatorial Atlantic in order to identify the key mechanisms by which wind-driven ocean dynamics control SST variability during the onset and peak phases of the Atlantic zonal mode. It is found that, in contrast with Pacific ENSO, both Bjerknes and Ekman feedbacks act together to force the zonal mode, although their relative importance and dominance depend on season and location.

abstract: An understanding of the formation of spatial heterogeneity is important because spatial heterogeneity leads to functional consequences at the ecosystem scale; however, such an understanding is still limited. Particularly, research simultaneously considering both external variables and internal feedbacks (self-organization) is rare, partly because these two drivers are addressed under different methodological frameworks. In this dissertation, I show the prevalence of internal feedbacks and their interaction with heterogeneity in the preexisting template to form spatial pattern. I use a variety of techniques to account for both the top-down template effect and bottom-up self-organization. Spatial patterns of nutrients in stream surface water are influenced by the self-organized patch configuration originating from the internal feedbacks between nutrient concentration, biological patchiness, and the geomorphic template. Clumps of in-stream macrophyte are shaped by the spatial gradient of water permanence and local self-organization. Additionally, significant biological interactions among plant species also influence macrophyte distribution. The relative contributions of these drivers change in time, responding to the larger external environments or internal processes of ecosystem development. Hydrologic regime alters the effect of geomorphic template and self-organization on in-stream macrophyte distribution. The relative importance of niche vs. neutral processes in shaping biodiversity pattern is a function of hydrology: neutral processes are more important in either very high or very low discharge periods. For the spatial pattern of nutrients, as the ecosystem moves toward late succession and nitrogen becomes more limiting, the effect of self-organization intensifies. Changes in relative importance of different drivers directly affect ecosystem macroscopic properties, such as ecosystem resilience. Stronger internal feedbacks in average to wetter years are shown to increase ecosystem resistance to elevated external stress, and make the backward shifts (vegetation loss) much more gradual. But it causes increases in ecosystem hysteresis effect. Finally, I address the question whether functional consequences of spatial heterogeneity feed back to influence the processes from which spatial heterogeneity emerged through a conceptual review. Such feedbacks are not likely. Self-organized spatial patterning is a result of regular biological processes of organisms. Individual organisms do not benefit from such order. It is order for free, and for nothing. / Dissertation/Thesis / Doctoral Dissertation Biology 2015

A presente pesquisa teve como objetivo investigar os efeitos da privação das retroalimentações sensoriais (aural, cinestésica e visual) na abordagem inicial de peças para piano por estudantes de diferentes níveis acadêmicos. A metodologia seguiu um delineamento experimental tipo hierárquico no qual 12 pianistas (alunos de início, meio e fim de curso da graduação, e alunos da pós-graduação em Música) foram submetidos a quatro condições de estudo com privação singular e/ou pareada das retroalimentações: (i) Condição A: Decodificação Visual com retroalimentação cinestésica e privação da retroalimentação aural; (ii) Condição B: Decodificação Visual com privação das retroalimentações aural e cinestésica (prática mental); (iii) Condição C: Decodificação Aural com retroalimentação cinestésica e privação da retroalimentação visual da partitura (“tocar a música de ouvido”); (iv) Condição D: Decodificação Aural com privação das retroalimentações cinestésica e visual da partitura. Para a coleta de dados, quatro encontros foram realizados individualmente com os pianistas. Cada encontro foi destinado ao estudo de uma peça em uma das condições de privação, seguidos de uma performance e entrevista semiestruturada. Os dados obtidos foram analisados qualitativamente e quantitativamente acerca do tempo de prática despendido em cada condição de estudo, das estratégias desenvolvidas pelos participantes e do produto das performances. Os resultados apontam que em todas as quatro condições, os participantes demonstraram a necessidade de estratégias de manipulação do conhecimento declarativo/semântico para a leitura e entendimento da linguagem musical, notada ou estimulada de forma aural. Em três das quatro condições (A, B e C), os participantes recorreram à manipulação de estratégias visando: (i) acessar o conhecimento procedimental no instrumento e fora dele a fim de estabelecer e/ou coordenar os movimentos para as situações de performance, (ii) capacitar meios de acesso e/ou de criação de uma representação mental para orientar suas performances e/ou fornecer subsídios básicos para a execução musical e capacidade de retenção das informações sensoriais. Na amostra investigada os pós-graduandos demonstraram níveis de expertise mais desenvolvidos através de produtos qualitativamente superiores aos demais estudantes no que concerne à comunicação expressiva e fluência na execução, nas condições A e B. / The present research aimed at investigating the effects of sensory feedbacks privation (auditory, kinesthetic and visual) during the initial approach to piano pieces by students belonging to different academic levels. The methodology was based on an experimental nested-design in which 12 pianists (freshman, sophomore and senior undergraduate students, and graduate students of Music) were submitted to four different studying conditions with single and/or paired privation of feedbacks: (i) Condition A: Visual Decoding with kinesthetic feedback and auditory feedback privation; (ii) Condition B: Visual Decoding with privation of auditory and kinesthetic feedbacks (mental practice); (iii) Condition C: Auditory Decoding with kinesthetic feedback and privation of visual feedback from the score (‘playing by ear’); (iv) Condition D: Auditory Decoding with privation of kinesthetic and visual (score) feedbacks. Data collection took place in four sections, individually with each pianist. In each section, the participant studied one piece under one condition of feedback privation, followed by performance and semi-structured interview. Data were analyzed qualitatively and quantitatively in terms of the practice time spent in each condition of study, of strategies developed by participants and of performance products. Results have shown that in all four conditions, the participants have shown the necessity of strategies for the manipulation of declarative/semantic knowledge for reading and musical language understanding, notated or auditory stimulated. In three out of four conditions (A, B and C), the participants have manipulated strategies aiming: (i) accessing the procedimental knowledge in and out of the instrument to establish and/or coordinate the movements for the performance; (ii) enabling means of access and/or creation of a mental representation to guide their performances and/or providing basic subsidies for musical execution and the capacity for holding the sensorial information. Within the investigated sample, the graduate students have shown more developed expertise levels through their qualitatively higher products in comparison to the other students in terms of expressive communication and fluency in conditions A and B.

A presente pesquisa teve como objetivo investigar os efeitos da privação das retroalimentações sensoriais (aural, cinestésica e visual) na abordagem inicial de peças para piano por estudantes de diferentes níveis acadêmicos. A metodologia seguiu um delineamento experimental tipo hierárquico no qual 12 pianistas (alunos de início, meio e fim de curso da graduação, e alunos da pós-graduação em Música) foram submetidos a quatro condições de estudo com privação singular e/ou pareada das retroalimentações: (i) Condição A: Decodificação Visual com retroalimentação cinestésica e privação da retroalimentação aural; (ii) Condição B: Decodificação Visual com privação das retroalimentações aural e cinestésica (prática mental); (iii) Condição C: Decodificação Aural com retroalimentação cinestésica e privação da retroalimentação visual da partitura (“tocar a música de ouvido”); (iv) Condição D: Decodificação Aural com privação das retroalimentações cinestésica e visual da partitura. Para a coleta de dados, quatro encontros foram realizados individualmente com os pianistas. Cada encontro foi destinado ao estudo de uma peça em uma das condições de privação, seguidos de uma performance e entrevista semiestruturada. Os dados obtidos foram analisados qualitativamente e quantitativamente acerca do tempo de prática despendido em cada condição de estudo, das estratégias desenvolvidas pelos participantes e do produto das performances. Os resultados apontam que em todas as quatro condições, os participantes demonstraram a necessidade de estratégias de manipulação do conhecimento declarativo/semântico para a leitura e entendimento da linguagem musical, notada ou estimulada de forma aural. Em três das quatro condições (A, B e C), os participantes recorreram à manipulação de estratégias visando: (i) acessar o conhecimento procedimental no instrumento e fora dele a fim de estabelecer e/ou coordenar os movimentos para as situações de performance, (ii) capacitar meios de acesso e/ou de criação de uma representação mental para orientar suas performances e/ou fornecer subsídios básicos para a execução musical e capacidade de retenção das informações sensoriais. Na amostra investigada os pós-graduandos demonstraram níveis de expertise mais desenvolvidos através de produtos qualitativamente superiores aos demais estudantes no que concerne à comunicação expressiva e fluência na execução, nas condições A e B. / The present research aimed at investigating the effects of sensory feedbacks privation (auditory, kinesthetic and visual) during the initial approach to piano pieces by students belonging to different academic levels. The methodology was based on an experimental nested-design in which 12 pianists (freshman, sophomore and senior undergraduate students, and graduate students of Music) were submitted to four different studying conditions with single and/or paired privation of feedbacks: (i) Condition A: Visual Decoding with kinesthetic feedback and auditory feedback privation; (ii) Condition B: Visual Decoding with privation of auditory and kinesthetic feedbacks (mental practice); (iii) Condition C: Auditory Decoding with kinesthetic feedback and privation of visual feedback from the score (‘playing by ear’); (iv) Condition D: Auditory Decoding with privation of kinesthetic and visual (score) feedbacks. Data collection took place in four sections, individually with each pianist. In each section, the participant studied one piece under one condition of feedback privation, followed by performance and semi-structured interview. Data were analyzed qualitatively and quantitatively in terms of the practice time spent in each condition of study, of strategies developed by participants and of performance products. Results have shown that in all four conditions, the participants have shown the necessity of strategies for the manipulation of declarative/semantic knowledge for reading and musical language understanding, notated or auditory stimulated. In three out of four conditions (A, B and C), the participants have manipulated strategies aiming: (i) accessing the procedimental knowledge in and out of the instrument to establish and/or coordinate the movements for the performance; (ii) enabling means of access and/or creation of a mental representation to guide their performances and/or providing basic subsidies for musical execution and the capacity for holding the sensorial information. Within the investigated sample, the graduate students have shown more developed expertise levels through their qualitatively higher products in comparison to the other students in terms of expressive communication and fluency in conditions A and B.

No description available.

Many grasslands in arid and semi-arid regions are undergoing rapid changes in vegetation, including encroachment of woody plants and invasive grasses, which can alter the rates and patterns of fire and sediment transport in these landscapes. We investigated the spatial distribution of sediments at the scale of vegetated microsites for three years following a prescribed fire using a multiple rare earth element (REE) tracer-based approach in a shrub-grass transition zone in the northern Chihuahuan desert (New Mexico, USA). To this end, we applied REE tracers – holmium, europium, and ytterbium on shrub, grass, and bare microsites, respectively in March 2016. Soil samples were collected from both burned and control (not burned) sites before (March) and after (June) the annual windy season, from 2016 through 2018. Results indicate that although the horizontal mass flux (HMF) of wind-borne sediment increased approximately threefold in the first windy season following the fire, and the HMF of both plots were not significantly different after three windy seasons. Comparing REE concentrations in sediments from both plots over the three years and three annual windy seasons, we observed a post-fire shift in source and sink dynamics of sediments. The tracer analysis of wind-borne sediments indicated that the source of the HMF in the burned site was mostly derived from shrub microsites following the fire, whereas the bare microsites were the major contributors for aeolian sediment in control areas. The shift in sources and sinks, and the spatial homogenization of REEs indicate that the removal of shrub vegetation resulted in sediment redistribution to the bare microsites even three years after the prescribed fire. The findings of this study will improve our understanding of post-fire geomorphic processes at a microsite scale in a grassland ecosystem undergoing land degradation induced by shrub encroachment. / Geology

Nous étudions la convergence de systèmes dynamiques vers des équilibres. En particulier, nous nous intéressons à deux types d'équilibres. D'une part, les solutions d'inéquations variationnelles sous contraintes qui interviennent aussi dans la résolution de problèmes d'optimisation hiérarchique. D'autre part l'état stable d'un système dynamique, c'est à dire l'état où l'énergie du système est nulle. Cette thèse est divisée en deux parties principales, chacune focalisée sur la recherche d'un de ces équilibres. Dans la première partie nous étudions une classe d'algorithmes explicite-implicites pour résoudre certaines inéquations variationnelles sous contraintes. Nous introduisons un algorithme proximal-gradient pénalisé, "splitting forward-backward penalty scheme". Ensuite, nous prouvons sa convergence ergodique faible vers un équilibre dans le cas général d'un opérateur maximal monotone, et sa convergence forte vers l'unique équilibre si l'opérateur est de plus fortement monotone. Nous appliquons aussi notre algorithme pour résoudre des problèmes d'optimisation sous contrainte ou hiérarchique dont les fonctions objectif et de pénalisation sont formées d'une partie lisse et d'une autre non lisse. En effet, nous démontrons la convergence faible de l'algorithme vers un optimum hiérarchique lorsque l'opérateur est le sous-différentiel d'une fonction convexe semi-continue inférieurement et propre. Nous généralisons ainsi plusieurs algorithmes connus et nous retrouvons leurs résultats de convergence en affaiblissant les hypothèses utilisées dans nombre d'entre eux.Dans la deuxième partie, nous étudions l'action d'un contrôle interne local sur la stabilisation indirecte d'un système dynamique couplé formé de trois équations d'ondes, le système de Bresse. Sous la condition d'égalité des vitesses de propagation des ondes, nous montrons la stabilité exponentielle du système. En revanche, quand les vitesses sont différentes, nous prouvons sa stabilité polynomiale et nous établissons un nouveau taux de décroissance polynomial de l'énergie. Ceci étend des résultats présents dans la littérature au sens où le contrôle est localement distribué (et non pas appliqué à tout le domaine) et nous améliorons le taux de décroissance polynomial de l'énergie pour des conditions au bord de type Dirichlet et Dirichlet-Neumann. / We study the convergence of dynamical systems towards equilibria. In particular, we are interested in two types of equilibria. On one hand solutions of constrained variational inequations that are also involved in the resolution of hierarchical optimization problems. On the other hand the stable state of a dynamical system, i.e. the state when the energy of the system is zero. The thesis is divided into two parts, each focused on one of these equilibria. In the first part, we study a class of forward-backward algorithms for solving constrained variational inequalities. We consider a splitting forward-backward penalty scheme. We prove the weak ergodic convergence of the algorithm to an equilibrium for a general maximal monotone operator, and the strong convergence to the unique equilibrium if the operator is an addition strongly monotone. We also apply our algorithm for solving constrained or hierarchical optimization problems whose objective and penalization functions are formed of a smooth and a non-smooth part. In fact, we show the weak convergence to a hierarchical optimum when the operator is the subdifferential of a closed convex proper function. We then generalize several known algorithms and we find their convergence results by weakening assumptions used in a number of them. In the second part, we study the action of a locally internal dissipation law in the stabilization of a linear dynamical system coupling three wave equations, the Bresse system. Under the equal speed wave propagation condition we show that the system is exponentially stable. Otherwise, when the speeds are different, we prove the polynomial stability and establish a new polynomial energy decay rate. This extends results presented in the literature in the sense that the dissipation law is locally distributed (and not applied in the whole domain) and we improve the polynomial energy decay rate with both types of boundary conditions, Dirichlet and Dirichlet-Neumann.

Made available in DSpace on 2016-04-29T13:17:57Z (GMT). No. of bitstreams: 1 Ana Alice Reis Pieretti.pdf: 811349 bytes, checksum: aaee4985f16a141c9e4e095e290179a0 (MD5) Previous issue date: 2015-12-15 / In spite of the existence of a fair amount of studies on programmed instruction, previously reported findings show some inconsistencies, and some specific manipulations in the implementation of this technology of teaching have not been satisfactorily investigated yet. The current study assessed the influence of varying the opportunities for receiving feedback as well as the influence of the moment of repetition of items answered incorrectly on learning under a programmed instruction procedure. Sixteen students, divided into two groups, participated in this study. All participants were given a pretest, training and a posttest. However, the conditions described below were manipulated only during the training session. Group 1 was exposed to the varied opportunities of repetition of those frames answered incorrectly under the following conditions: 1a) Repetition at the end of the series only once; 1b) Repetition at the end of the series up to three times; 1c) Repetition after feedback only once; 1d) Repetition after feedback up to three times. A procedure that varied the type of feedback was adopted for Group 2, in accordance with the following conditions: 2e) Feedback after every answered frame; 2f) No feedback for any of the answered frames; 2g) Feedback for every frame answered correctly; 2h) Feedback after every incorrectly answered frame. Results showed that all participants produced a higher percentage of correct posttest answers compared to pretest answers. The highest average percentages occurred in the Repetition after feedback up to three times condition (67.42% correct answers) and the Repetition after feedback only once condition (66.06% correct answers). As for Group 2, the conditions with the highest average percentages for correct answers were Feedback after every frame (69.5%) and Feedback after every incorrectly answered frame (69.2%). The influence of the implementation of the whole procedure in only one session on participants posttest performance is discussed. Furthermore, it is possible to claim that the moment when repetition of items occurred seemed to have exerted more influence on participants performance than the amount of times they could repeat the item answered incorrectly. It is also warranted a discussion about the need for increasing the number of opportunities for repeating the incorrect items / Apesar de haver um razoável número de estudos sobre Instrução Programada tecnologia de ensino desenvolvida por Skinner -, os resultados encontrados apresentam incongruências, e algumas manipulações específicas na aplicação dessa tecnologia de ensino não foram suficientemente investigadas. O presente trabalho avaliou a influência de variações da oportunidade de apresentação do feedback, e do momento e número de repetições dos itens respondidos incorretamente sobre a aprendizagem, em um procedimento de Instrução Programada. O estudo foi realizado com 16 participantes, estudantes do ensino superior, divididos em dois grupos. Todos os participantes passaram por pré-teste, treino e pós-teste, sendo que as condições apresentadas a seguir foram manipuladas apenas durante o treino. O Grupo 1 foi submetido a variação nas oportunidades de repetição dos quadros respondidos incorretamente, nas seguintes condições: 1a) Repetição ao final da série por uma vez; 1b) Repetição ao final da série até três vezes; 1c) Repetição em seguida ao feedback uma vez; 1d) Repetição em seguida ao feedback até três vezes. O Grupo 2 foi submetido a variação no tipo de feedback, nas condições: 2e) Feedback em todos os quadros respondidos; 2f) Feedback para nenhum dos quadros respondidos; 2g) Feedback em todos os quadros respondidos corretamente; 2h) Feedback em todos os quadros respondidos incorretamente. A ordem em que os diferentes participantes passaram pelas diversas condições variou entre eles. Todos os participantes apresentarem uma maior porcentagem de respostas corretas no pós-teste do que no pré-teste. As maiores porcentagens médias de acertos do Grupo 1 ocorreram nas condições Repetição após o feedback até três vezes (67.42% de acertos) e Repetição após o feedback uma vez (66.06% de acertos), nessa ordem. As condições com as maiores porcentagens médias de acertos para o Grupo 2 foram Feedback em todos os quadros (69.5%), seguida da condição Feedback em todos os quadros respondidos incorretamente (69.2%). Além disso, os resultados apontam que o momento da repetição dos itens pareceu ter mais influência sobre o desempenho dos participantes do que a quantidade de vezes em que estes puderam repetir os itens respondidos incorretamente

Dune grasses are integral to biogeomorphic feedbacks that create and alter foredunes and barrier island stability. In a glasshouse study, Ammophila breviligulata Fern. and Uniola paniculata L. were planted together and subjected to sand burial to quantify morphological and physiological response. Ammophila breviligulata physiological and morphological performance declined when planted with U. paniculata but U. paniculata was not affected when planted with A. breviligulata. Burial had a positive effect on A. breviligulata and U. paniculata as indicated by electron transport rate and total biomass at the end of the experiment. Due to their different growth strategies, A. breviligulata and U. paniculata form continuous versus hummocky dunes, respectively. As global temperatures rise and U. paniculata migrates into A. breviligulata dominated habitat, A. breviligulata performance may diminish, and changes in dune form could result in altered island stability via increased overwash. Foredune community structure could also change due to the shift in dominant species which could alter dune succession.