Cette thèse traite de l'acquisition des consonnes par des enfants francophones monolingues. Son but est de montrer que l'utilisation des traits distinctifs et des principes qui leur sont associés (hiérarchie des traits, évitement de la marque, économie des traits) rend compte du parcours d'acquisition des consonnes en français. Le corpus de cette thèse est constitué des productions spontanées longitudinales (pendant 16 et 28 mois) de deux enfants francophones. L'analyse a dégagé deux grandes étapes dans le parcours d'acquisition des contrastes consonantiques. Chacune d'elle repose sur l'intervention d'un principe associé aux traits distinctifs. La première étape rend compte de l'acquisition isolée des contrastes opposant les consonnes, dont l'ordre est guidé par le principe de hiérarchie des traits, exprimé par leur robustesse : plus un trait est robuste, plus il sera acquis rapidement. L'acquisition d'un trait suppose également l'acquisition des deux va- leurs de ce trait par l'intervention du principe d'évitement de la marque : la valeur non-marquée de chaque trait sera acquise avant la valeur marquée. La seconde étape consiste en la diffusion, à l'ensemble du système, d'un trait acquis de façon isolée. Cette diffusion est guidée par le principe d'économie des traits : plus un trait participe à l'économie du système, plus il se diffusera rapidement. Afin d'extraire de l'input de l'enfant, l'information utile nous permettant d'exprimer l'actualisation de chaque principe dans la langue, nous avons conçu des calculs de fréquence des traits. Nous avons établi un lien entre l'expression des principes de hiérarchie, d'évitement de la marque et d'économie, et ces différentes fréquences des traits dans le langage adressé à l'enfant. En appréhendant l'acquisition consonantique comme l'acquisition de contrastes au sein d'un système, nous avons modélisé le parcours d'acquisition des consonnes grâce aux traits distinctifs et à leurs principes associés, en le mettant en regard des travaux sur la structuration des inventaires sonores adultes.

Tropical montane cloud forests (TMCF) are one of the most fascinating, but least understood ecosystems in the world, and the interest in the carbon (C) cycle of TMCFs with regard to carbon sequestration and storage practices has increased rapidly in recent years. One feature that prevails in all TMCFs is a decrease in aboveground net primary productivity (ANPP) and standing biomass and leaf area index (LAI) with increasing altitude, together with the stunted growth form of the trees. This thesis focuses on the input part of the TMCF C-cycle, and investigates the controlling factors on photosynthesis on a leaf, canopy, and ecosystem level in the Kosñipata valley in south east Peru, on the eastern slope of the Andes (13º11’28’’S / 71º35’24’’W). Leaf traits are known to relate to foliar C-exchange, and compared with other altitudinal transect studies of TMCFs, the studied sites had similar altitudinal trends for foliar nitrogen (N) content (though not for phosphorus) and leaf mass per area (LMA), with N content decreasing and LMA increasing with altitude. N concentrations were relatively high and LMA values relatively low, but this observed relationship was consistent with those found in global leaf trait surveys. Examining plant stoichiometry (i.e. N:P ratios), the data suggests that unlike the general hypothesis, the Kosñipata forests are not N limited, except for the study site at 2990 m a.s.l. At the 2990 m a.s.l. site, which is the focal study site of the thesis, photosynthetic parameters Vcmax (the carboxylation efficiency of the Rubisco protein) and Jmax (the electron transport efficiency) proved to be similar to those found in lowland tropical rainforest leaves when expressed on an area basis and standardised to 25 °C (55.6 ± 2.6 and 106.5 ± 5.2 mmol m-2 s-1, for Vcmax and Jmax, respectively). However, when standardised to the mean ambient TMCF temperature of 12.5 °C, both photosynthetic parameters were much lower than ambient tropical rainforest Vcmax and Jmax values. The TMCF Jmax -Vcmax relationships were steeper than found in other tropical biomes, indicating a possible adaptation to the lower light availability in TMCFs because of frequent cloud cover, or a consequence of little atmospheric evaporative demand, which is also due to the humid conditions in this forest type. Although N-Vcmax relationships were significant (P<0.05), the fit was not very strong and the relationship between nitrogen use efficiency (NUE) and Vcmax indicates that TMCF species can be regarded as a different plant functional type compared with other tropical forest types. Diurnal measurements of net photosynthesis (A), stomatal conductance (gs) and leaf water potential (Yleaf) showed that different TMCF species experienced non-contrasting diurnal patterns of Yleaf and gs in the dry season. The observed patterns suggest that some TMCF species can be classified as isohydric species, while others behave anisohydrically. Additionally, in situ gs was not very responsive to these to the range of experienced photosynthetically active radiation (PAR), vapour pressure deficit (VPD) or soil water content (SWC), leading to the conclusion that in the studied TMCF, drought stress does not play a role in C-uptake. When using the measured photosynthetic parameters for up-scaling C-uptake to stand scale with a Soil-Plant-Atmosphere model, simulated annual gross primary productivity (GPP) was 16.24 ±1.6 T C ha-1 yr-1, which is about half the GPP observed in neotropical lowland rainforests. Analyses of the modelled results showed that GPP in this TMCF is mostly controlled by temperature, PAR and leaf area index (LAI) and when increasing these three factors to values found in tropical lowland forest, GPP increased up to 75%. In addition, the modelled results indicate that hydraulic limitations on TMCF C-uptake are very unlikely under current climatic conditions. The modelled results also showed that increases in radiation as a result of less cloud cover do not translate to straightforward increases of GPP. The cloudy conditions of TMCFs, which reduced incident PAR in TMCFs, should therefore not be regarded simply as a negative control on TMCF GPP. Instead, the increase in fraction of diffuse radiation partially offsets the decrease in GPP following the reduction in PAR. Overall, the results of this study show that leaves of Andean TMCF forests have similar C-uptake capacity to tropical lowland rainforests when standardized to similar temperatures, but that for in situ C-uptake temperature, radiation and LAI are the key controls.

Background: Patients with anorexia nervosa have been consistently reported to show impairments in set shifting ability. Such deficits may be associated with characteristics commonly observed in this patient group, such as obsessive thoughts and behaviours around eating, maladaptive problem solving and a rigid thinking style. Objective: Much of the preceding literature on set shifting ability has involved inpatient samples meeting strict diagnostic criteria for anorexia nervosa. However most eating disorder patients are outpatients and commonly do not meet full criteria for anorexia nervosa. This study thus aimed to investigate the relationship between set shifting ability and psychological characteristics in a community sample of outpatients with symptoms of anorexia nervosa. Methods: Performance on selected measures of set-shifting ability (Wisconsin Card Sort Test, WCST; Delis-Kaplan Executive Function System, Hayling & Brixton) were compared between an eating disorders group comprising 17 female outpatients with symptoms of anorexia nervosa and a control group comprising 27 students. Set shifting performance was then correlated with eating disorder severity (Eating Disorders Examination), obsessive-compulsive symptoms (Yale-Brown Obsessive Compulsive Scale), and the Social Problem Solving Inventory. Results: The eating disorder group demonstrated significantly worse set shifting ability than the healthy control group on the primary outcome measure (WCST), with 47% of eating disorder participants showing impairment on this measure. Severity of obsessive-compulsive symptoms and an impulsive and careless approach to problem solving were associated with poorer scores on the WCST in the eating disorder group. Although the eating disorder group were significantly more impaired in set shifting than controls, set shifting ability was not associated with eating disorder severity. Conclusions: The results indicate that set shifting impairments are present in outpatients with eating disorders with anorexic symptoms, and may be trait characteristics. Impaired set shifting was associated with obsessive-compulsive symptoms and maladaptive problem solving. These findings highlight a need for neuropsychological assessment of eating disorder outpatients in order to identify individuals who may benefit from psychological interventions to reduce the impact of these impairments.

Knowledge about dispersion is of utmost importance for understanding populations’ reaction to changes in the environment. Expansion of a population range brings with it both spatial sorting and over time, spatial selection. This means that dispersion rates increases over time at the expanding edge. Most studies have so far been performed on continuously expanding populations. This study aims to bring more knowledge about dispersal biology in dynamic systems. I studied dispersal traits in two permanent and two seasonal vegetation habitats of an isopod (Asellus aquaticus), for which differentiation between habitat types has previously been shown. I quantified differences in displacement (dispersal rate) and three morphological traits, head angle (body streamline) and leg of the third and seventh pair of legs. Isopods from the seasonal vegetation had higher displacement rates than animals from permanent vegetation. This inclines that mechanisms driving spatial selection in expanding population ranges also exist in dynamic systems. The more streamlined isopods found in seasonal sites further points towards spatial sorting by dispersion capability. Because no effect of permanence was found on leg length and there was no correlation between streamlining and displacement, the higher dispersion among animals from seasonal habitats most likely derives from behavioral differences.

<p>Nivo zadovoljstva karijerom predstavlja fenomen kojem se u poslednje vreme pri&scaron;lo sa ozbiljnijim interesovanjem. Utvrđivanje odnosa crta ličnosti, strukture radne motivacije za zadovoljstvo karijerom, uspe&scaron;nih ljudi predstavlja plodno tle za polje savetovanja u karijeri. Danas je fokus istraživača pomeren i zadržan na intrinzičkim kriterijumima uspeha u karijeri, gde se pored crta ličnost, strukture radne motivacije sa posebnom pažnjom ispituju i uticaji organizacije ali i ravnoteže između porodičnih i radnih uloga na ukupno zadovoljstvo karijerom. U cilju &scaron;to boljeg razumevanja strukture ličnosti u organizacijskim u konceptu zadovoljstva karijerom, pored osnovnih, aktuelno je prisutan i koncept &bdquo;dodatnih&ldquo; crta ličnosti. Pregled savremene literature ukazuje na nedovoljnu proučenost međusobnog odnosa navedenih fenomena, pogotovo primene teorije samodeterminacije u ovakvomm istraživačkom konceptu.<br />Da bismo detaljnije ispitali značaj crta ličnosti i strukture radne motivacije za zadovoljstvo karijerom, pristupili smo ispitivanju crta ličnosti, strukture radne motivacije u odnosu na nivo zadovoljstva karijerom i to kod uspe&scaron;nih ljudi. Zadovoljstvo karijerom je definisano kao evaluacija ličnog napretka u odnosu na lične ciljeve u karijeri. Povodom ovog rada, konstruisan je utpinik namenjen ispitivanju zadovoljstva karijerom, ZAK i koji je na pilot uzorku dao prihvatljive metrijske karakteristike. Uzorak ispitanika je sastavljen od ukupno 110 osoba sa vrlo uspe&scaron;nom karijerom u oblasti obrazovanja, bankarstva i biznisa u Republici Srbiji. Njihova karijera je ocenjena kao uspe&scaron;na na osnovu sledećih kriterija: akademskog postignuća &ndash; status profesora univerziteta; rukovodeće pozicije u bankama i internacionalnim kompanijama; kao i vlasni&scaron;tvo kompanija koje su imale iznad deset zaposlenih i pozitivan bilans u prethodnim godinama poslovanja. Četrnaest ispitanika je bilo srednjeg obrazovnog nivoa, 22 sa vi&scaron;om stručnom spremom, a sa visokom ukupno 74, od toga sa VII/1 stepenom 37 i VII/2 i VIII stepenom takođe 37 ispitanika. Najmlađi ispitanik je imao 26 godina, najstariji 68, dok je prosečna starost bila 47 godina. Najduži radni staž je bio 44 godine, a prosečan 21 godinu. Primenjeni su sledeći instrumenti: LEKSI 70, namenjen ispitivanju crta ličnosti baziranih na konceptu &bdquo;velikih pet&ldquo; plus dva; SRM-1, za ispitivanje strukture radne motivacije; kao i ZAK, upitnik koji ispituje nivo zadovoljstva karijerom.<br />Nakon primene serije analiza utvrđeno je da su prediktori zadovoljstva karijerom kod vrlo uspe&scaron;nih osoba osobina ličnosti pozitivna emocionalnost, stanje ispunjenosti karijerom, intrinzička motivacija i regulacija identifikacijom. Slično tome, pronađena je veza između crta savesnost i otvorenost sa regulacijom identifikacijom i intrinzičkom motivacijom i zadovoljstvom karijerom. Glavni prediktori zadovoljstva i ispunjeno&scaron;ću karijerom kod vrlo uspe&scaron;nih osoba su izražena crta ličnosti otvorenost i sniženje crte negativna emocionalnost Osoba sklona izbegavanju posla ima manje izraženu savesnost, povi&scaron;enu negativnu emocionalnost, pokazuje sklonost ka introjektovanoj regulaciji. Pored toga, osoba sa izraženom negativnom emocionalno&scaron;ću ima tendenciju ka promeni karijere. Dužina radnog staža sugeri&scaron;e zaključak da su osobe sa dužom uspe&scaron;nom karijerom manje neprijatne i vi&scaron;e savesne. Obrazovni nivo ispitanika je bio u vezi sa ispunjeno&scaron;ću karijerom, tako &scaron;to su najobrazovaniji ispitanici bili zadovoljniji od manje obrazovanih. Ispitivanje značaja oblasti karijere na relacije osobina i strukture motivacije na zadovoljstvo pokazuje da se grupe međusobno razlikuju po tome &scaron;to grupe menadžera i univerzitetskih profesora u odnosu na bankare pokazuju veći stepen zadovoljstva karijerom i imaju izraženije crte otvorenost i pozitivna valenca, dok im je ekstrinzička radna motivacija niža u odnosu na grupu bankara.&nbsp;Ustanovljeno je i da grupa bankara ima izraženiju introjektovanu regulaciju i intrinzičku motivaciju od grupe profesora i grupe menadžera</p> / <p>The level of the satisfaction with the career is a phenomenon that has been lately analysed seriously and with attention. To determine the relationship between personality traits and structures of work motivation for career satisfaction with successful people is a good basis for the field of advising. Up to now it was only discussed in the context of objective, external criterion of satisfaction. Since the industrial-organizational psychology has become interested in the concepts of personality again by creating socio-cognitive approaches to motivation, this relation has occupied an important place in studies of organizational behavior. Today, the focus of researchers is shifted and held on the intrinsic criteria of the success in career and in addition to personality traits, structures of work motivation are examined with special attention in terms of organization and in terms of the influence of family/work balance on the level of satisfaction. Contemporary literature review indicates the insufficient study of the concepts mentioned above, especially the application of the theory of self-determination in this concept of research.<br />In order to examine the importance of personality traits and structure of work motivation we started examining personality traits and structure of work motivation in relation to the level of career satisfaction of successful people. Career satisfaction is defined as the evaluation of personal progress in relation to personal goals. The research included 110 people with very successful careers in fields of education, bankings and business in the Republic of Serbia. Their career was evaluated as successful on the following criteria: academic achievements &ndash; the status of the university professor, managing or senior positions in banks and international companies; entrepreneurs and company owners that have more than ten employees and the positive balance in previous years. Fourteen examinees had secondary school education, 22 with Bachelor&rsquo;s degree, total of 74 with university degree of which 37 had Master&rsquo;s degree and 37 of them PhD.<br />The youngest examinee was 26, the oldest 68, while the average age was 47. The longest years of service was 44 years, and average 21 year. The following tests were applied: LEKSI 70, test designed for testing personal traits based on the &rsquo;&rsquo;Big Five&rsquo;&rsquo; plus two; SRM-1, for testing the structure of work motivation; and For the purpose of this paper, a questionnaire is made to investigate the level of career satisfaction, ZAK which as the pilot sample had given acceptable psychometric characteristics.. After the application of series of results, the following are the most important to mention: the connection between personality traits and positive emotionality, factors for career satisfaction, intrinsic motivation and regulation through identification with successful people. Similarly, the connection between career satisfaction and regulation through identification and intrinsic motivation has been found between openness and conscientiousness. In addition, the quality of openness showed negative correlation with external regulation and conscientiousness with the factor of avoiding work. Examinees who were more prone to regulation through identification showed more distinctive positive emotionality and conscientiousness, but at the same time&nbsp;the higher level of unpleasantness/aggression. Years of service suggest that people with long and successful careers are less unpleasant and more conscientious. The relation between negative valence factors, psychosomatic symptoms, avoiding work and external control stands out as an important highlight. Examined group of managers and university professors in relation to bankers show the higher level of satisfaction with their careers, have more distinctive quality of openness and positive valence while at the same time their extrinsic motivation is lower than in the group of bankers. In addition, people with negative emotions had tendencies for a career change. The educational level connected to the career satisfaction showed that more educated people were more satisfied from less educated. In addition to basic personality traits and in order to understand better the structure of personality in organizational behavior, the concept of &#39;additional&#39; personality traits is also important.</p>

Humans spend a third of their lives sleeping but very little is known about the physiological and genetic mechanisms controlling sleep. Increased data from sleep phenotyping studies in mouse and other species, genetic crosses, and gene expression databases can all help improve our understanding of the process. Here, we present analysis of our own sleep data from the large-scale phenotyping program at The Jackson Laboratory (JAX), to identify the best gene candidates and phenotype predictors for influencing sleep traits. The original knockout mouse project (KOMP) was a worldwide collaborative effort to produce embryonic stem (ES) cell lines with one of mouse’s 21,000 protein coding genes knocked out. The objective of KOMP2 is to phenotype as many as of these lines as feasible, with each mouse studied over a ten-week period (www.mousephenotype.org). The phenotyping for sleep behavior is done using our non-invasive Piezo system for mouse activity monitoring. Thus far, sleep behavior has been recorded in more than 6000 mice representing 343 knockout lines and nearly 2000 control mice. Control and KO mice have been compared using multivariate statistical approaches to identify genes that exhibit significant effects on sleep variables from Piezo data. Using these statistical approaches, significant genes affecting sleep have been identified. Genes affecting sleep in a specific sex and that specifically affect sleep during daytime and/or night have also been identified and reported. The KOMP2 consists of a broad-based phenotyping pipeline that consists of collection of physiological and biochemical parameters through a variety of assays. Mice enter the pipeline at 4 weeks of age and leave at 18 weeks. Currently, the IMPC (International Mouse Phenotyping Consortium) database consists of more than 33 million observations. Our final dataset prepared by extracting biological sample data for whom sleep recordings are available consists of nearly 1.5 million observations from multitude of phenotyping assays. Through big data analytics and sophisticated machine learning approaches, we have been able to identify predictor phenotypes that affect sleep in mice. The phenotypes thus identified can play a key role in developing our understanding of mechanism of sleep regulation.

1. A longstanding goal of ecology and conservation biology is to understand the environmental and biological controls of forest succession. However, the patterns and mechanisms that guide successional trajectories, especially within tropical forests, remain unclear. 2. We collected leaf functional trait and abiotic data across a 110-year chronosequence within a tropical dry forest in Costa Rica. Focusing on six key leaf functional traits related to resource acquisition and competition, along with measures of forest stand structure, we propose a mechanistic framework to link species composition, community trait distributions and forest structure. We quantified the community-weighted trait distributions for specific leaf area, leaf dry matter concentration, leaf phosphorus concentration, leaf carbon to nitrogen ratio and leaf stable isotopic carbon and nitrogen. We assessed several prominent hypotheses for how these functional measures shift in response to changing environmental variables (soil water content, bulk density and pH) across the chronosequence. 3. Increasingly, older forests differed significantly from younger forests in species composition, above-ground biomass and shifted trait distributions. Early stages of succession were uniformly characterized by lower values of community-weighted mean specific leaf area, leaf stable nitrogen isotope and leaf phosphorus concentration. Leaf dry matter concentration and leaf carbon to nitrogen ratio were lower during earlier stages of succession, and each trait reached an optimum during intermediate stages of succession. The leaf carbon isotope ratio was the only trait to decrease linearly with increasing stand age indicating reduced water use efficiency in older forests. However, in contrast with expectations, community-weighted trait variances did not generally change through succession, and when compared to null expectations were lower than expected. 4. The observed directional shift in community-weighted mean trait values is consistent with the 'productivity filtering' hypothesis where a directional shift in water and light availability shifts physiological strategies from 'slow' to 'fast'. In contrast with expectations arising from niche based ecology, none of the community trait distributions were over-dispersed. Instead, patterns of trait dispersion are consistent with the abiotic filtering and/or competitive hierarchy hypotheses.

Magistro darbas: „Dirbančių suaugusiųjų subjektyvios gerovės, asmenybės bruožų ir savęs vertinimo sąsajos“. Darbo tikslas: ištirti sąsajas tarp dirbančiųjų subjektyvios gerovės, asmenybės bruožų ir savęs vertinimo. Pradžioje keliama hipotezė, kad dirbančiųjų subjektyvi gerovė, asmenybės bruožai ir savęs vertinimas yra susiję. Tikslui pasiekti buvo iškelti šie uždaviniai: įvertinti tiriamųjų subjektyvios gerovės, asmenybės bruožų ir savęs vertinimo ypatumus; palyginti tiriamųjų subjektyvios gerovės įverčius pagal: lyties, amžiaus, išsilavinimo, šeimyninės padėties, vaikų turėjimo, gaunamų pajamų, darbo pobūdžio aspektus; nustatyti sąsajas tarp tiriamųjų subjektyvios gerovės ir asmenybės bruožų; nustatyti sąsajas tarp tiriamųjų subjektyvios gerovės ir savęs vertinimo; nustatyti sąsajas tarp tiriamųjų asmenybės bruožų ir savęs vertinimo. Tyrimo rezultatai atskleidė, kad tyrimo grupės (dirbančiųjų) subjektyvi gerovė yra vidutinio lygio; daugumos respondentų vyraujanti asmenybės ypatybė yra sąmoningumas (kiti asmenybės bruožai: ekstraversija, sutariamumas, neurotiškumas ir atvirumas patyrimui); didžiajai tiriamųjų daugumai būdingas teigiamas savęs vertinimas. Buvo nustatyta, kad dirbančiųjų subjektyvi gerovė yra susijusi su gaunamomis pajamomis, bet nesusijusi su kitais sociodemografiniais veiksniais: lytimi, amžiumi, išsilavinimu, šeimine padėtimi, vaikų turėjimu, darbo pobūdžiu. Taip pat nustatyta, kad dirbančiųjų subjektyvi gerovė teigiamai siejosi su tokiais asmenybės bruožais... [toliau žr. visą tekstą] / The aim of this work is examine the connections between workers subjective well-being, personality traits and self-evaluation. In the beginning of the research was raised a hipothesis that workers’ subjective well-being, personality traits and self-evaluation are connected. To reach the aim was raised these objectives: to evaluate investigatives’ subjective well-being, personality traits and self-evaluation features; to compare investigatives’ grades of subjective well-being according to these social-demographic aspects: gender, age, education, family state, having offsprings, getting incomes, job position; to set the connections between investigatives’ subjective well-being and personality traits; to set the connections between investigatives’ subjective well-being and self-evaluation; to set the connections between investigatives’ personality traits self-evaluation. As demonstrate the results of research, investigatives’ subjective well-being is on the middle level; the majority of investigatives’ personality trait is Conscientiousness (other traits: Extraversion, Agreebleness, Neuroticism and Openess to Experience); for the vast majority of the investigatives is typical possitive self-evaluation. It was estimated, that workers‘ subjective well-being is connected with incomes, but does not connected with others social-demographic factors. It was also estimated, that investigatives’ subjective well-being was positively connected with such personality traits as Extraversion... [to full text]

Tidigare forskning menar att det äldsta syskonet anses vara mer auktoritärt, det mellersta barnet minst familjeorienterat och det yngsta barnet mer socialt. Uppväxten kan påverka individens KASAM. Studien undersöker om syskonplacering samverkar med människors KASAM, personlighet utifrån femfaktormodellen samt ser till eventuella könsskillnader. Urvalet bestod av högskolestudenter, varav 145 kvinnor och 80 män. Enkätens material analyserades med tvåvägs variansanalyser. Studien uppvisade ingen signifikant skillnad mellan de tre syskonplaceringarna. En tendens till signifikant interaktion visades mellan könen, där kvinnliga mellanbarn har lägre KASAM än de manliga. Studien visade två signifikanta könsskillnader mellan kvinnor och män. Kvinnorna var mer neurotiska och samvetsgranna än männen. Resultatet uppvisade en tendens till signifikans, gällande att kvinnor hade högre grad av personlighetfaktorn öppenhet än männen. Slutligen konstaterades att syskonplaceringen inte samverkar med individens personlighet eller KASAM, men att det finns vissa personlighetsskillnader mellan könen. Resultatet kan bero på brister i studien, som att familjekonstellation inte tillfrågades deltagarna.

The biochemistry of leaves merges the fates of trees and the atmosphere. Leaf primary metabolism cycles carbon and indirectly drives atmospheric circulation via the latent heat of transpiration. Tropical forests contain half of global forest carbon, and actively cycle carbon and energy year round, making them critical components of the coupled biosphere-climate system. Climate change threatens tropical forests with rising temperatures and increasing variability of precipitation. Their response will influence future biodiversity as well as the fate of the climate. Understanding the physiological attributes that define tropical tree responses and feedbacks to climate is a current research priority. The emission of isoprene gas from plant leaves has been demonstrated to enhance leaf tolerance to high temperatures and drought. Isoprene is a volatile secondary metabolite produced in the chloroplast by approximately one-third of plant species. While the benefits of isoprene are supported by extensive laboratory and greenhouse-based research, work has only begun to explore how the trait is integrated in plant functional strategies. Whether isoprene influences differential species performance and survival across environments has yet to be tested. An impediment to filling this clear ecological research gap has been a lack of instrumentation capable of quantifying isoprene emissions from leaves in remote field settings. The first study presented here tests the hypothesis that isoprene emission influences plant community assembly shifts across environmental gradients and through time in tropical forests. The capacity for a species to produce isoprene was associated with increased relative abundance at higher temperatures and following drought anomalies. A negative relationship with the length of seasonal drought suggests a trade-off between isoprene emission and other plant traits, such as deciduous leaf habit. The second study presents the development of a new instrument that is uniquely optimized for field-based ecological research on leaf volatiles. The new system, named PORCO (Photoionization of Organic Compounds), utilizes custom leaf cuvettes, precision light control, and an optimized commercial photoionization detector to achieve real-time detection of leaf emissions with detection limits better than 0.5 nmol m⁻² leaf s⁻¹. The third study utilizes PORCO to test hypotheses about the structuring of isoprene within plant functional strategies and across forest microenvironments in an eastern Amazonian evergreen tropical forest. The results support the role of isoprene—and potentially other volatile isoprenoids—in mitigating effects of intermittent sun exposure in the sub-canopy. Emissions are structured in a complex, multivariate manner that depends on taxonomy, leaf and wood characteristics, tree height, and light environment. The results from this dissertation work demonstrate that isoprene emission from leaves affects plant responses to climate at ecologically relevant scales. Isoprene influences climate not only by its effect on primary leaf functions, but also by directly altering atmospheric chemistry, and contributing to aerosol and cloud properties. Understanding isoprene's role in forest responses to increasing temperatures and drought will help to predict the feedbacks between forest ecosystems and climatic change.