Great Basin bristlecone pine (GBBP) (Pinus longaevaBailey) is one of the longest-lived organisms on Earth, and is one of the most highly fragmented high elevation conifer species. Throughout the Great Basin of the Intermountain West, GBBP are being impacted by changing disturbance regimes, invasive species, and climate change. To better understand the effects of climate variability and ecological disturbances in GBBP systems, three studies were designed and implemented. The first characterized the distribution of forest fuel in stands of GBBP and predicted how fuels may change under future climate scenarios. Using the Forest Inventory Analysis (FIA) plot variables of tree species, height, diameter at breast height (DBH), canopy base height (CBH), coarse (CWD) and fine (FWD) woody debris across elevational gradients, this study examined the effects of changes to fuel loading on predicted changes in fire behavior and severity. All classes of FWD decreased with elevation, and only 1000-hr fuels remained constant across elevational transects. This, combined with lower CBH and foliar moisture and increasing temperatures due to climate change, suggested increased fire potential at the GBBP treeline. The second study examined the role of volatile organic compounds (VOCs) and tree chemistry and their response to the environment. VOCs and within needle chemistry were collected and analyzed along elevational gradients near the northern and southern limits of GBBP. Random Forest analysis distinguished elevation using VOCs, with 83% accuracy, and identified the compounds most important for classification. Ordination revealed that temperature, heat load index, and relative humidity were each significantly correlated with VOCs. Within-needle chemistry provided less predictive value in classifying elevation (68% accuracy) and was correlated only with heat load index. These findings suggest that GBBP VOCs are highly sensitive to the environment. The final study explored the role of VOCs in host selection of mountain pine beetle (MPB). Mountain pine beetles oriented toward VOCs from host limber pine (Pinus flexilis James) and away from VOCs of non-host GBBP using a Y-tube olfactometer. When presented with VOCs of both trees, females overwhelmingly chose limber pine over GBBP. While there were only a few notable differences in VOCs collected from co-occurring GBBP and limber pine, 3-carene and D-limonene were produced in greater amounts by limber pine. There was no evidence that 3-carene is important for beetles when selecting trees, however, addition of D-limonene to GBBP VOCs disrupted the ability of beetles to distinguish between tree species. Climate change will impact how forests are managed and this research could provide insight into the mechanisms underlying the incredible longevity of this iconic tree species.

In the Circum-Caribbean, long timescale paleoenvironmental records, which are used to establish important baseline data for climatological phenomena such as droughts, floods, and hurricanes, are rare. This project uses geological and geochemical proxies (X-Ray fluorescence core scanning data, grain-size analysis, loss on ignition) from a nine-meter-long sediment core from a coastal karst basin near Haiti’s southwestern peninsula to reconstruct Holocene environmental and climatic changes in a region that is both understudied and highly sensitive to the effects of storms, sea level change, tectonics, and anthropogenic impacts. The chronology of the core is established with 4 AMS dates from terrestrial organic matter and shows continuous sedimentation from ~8500 cal BP to the present, with an abrupt increase in sedimentation rate at ~2900 cal BP. High values of Ti and Ti/Ca are associated with finer sediments in the core and indicate relatively humid conditions at ~6500 cal BP, followed by a gradual drying trend. This is consistent with data from elsewhere in the Caribbean that reflects a southward migration of the ITCZ during the early Holocene. After 2500 cal BP, a series of large and abrupt increases in Ti and Ti/Ca are associated with an influx of finer, terrestrially-derived sediment into the bay due to enhanced discharge from the nearby Baradères River, possibly as a result of short-duration shifts to wetter climate conditions, hurricane-induced precipitation, and/or prehistoric-era human settlement. Variations in silicate input (e.g., K/Ti), marine productivity (e.g., Ca/Ti), and redox conditions (e.g., Mn/Fe) are linked to local climate changes and resulting changes in the depositional environment, while peaks in Rb/Sr and Ti/Ca could be signals for erosion related to events such as hurricanes and/or land use changes. Finally, high values of silt and clay, in conjunction with enhanced organics, Ti, Fe, K and P over the last couple centuries reflect historic-era deforestation and erosion. This study presents an excellent opportunity to further our understanding of the diverse relationships between ecosystem dymanics, climate, and anthropogenic forcings and adds to the growing inventory of paleoclimatological records in the Caribbean, improving the spatial distribution of such studies, and ultimately improving our understanding of the driving forces of both short- and long-term climate variability.

Les rats introduits (Rattus spp.) sont des espèces invasives majeures menaçant la biodiversité sur la plupart des îles de laPlanète. Deux espèces, le rat noir (R. rattus) et le rat du Pacifique (R. exulans) vivent en sympatrie au sein des forêts deNouvelle-Calédonie, où la question de la faisabilité et de l' intérêt de leur contrôle (i.e. limitation locale de leur 'abondance)pour la conservation de la biodiversité native est posée. En raison d'un manque de cadre conceptuel des projets de contrôle,nous avons d'abord réalisé une synthèse et une analyse des opérations de contrôle de rats invasifs dans les milieux naturelsdes îles du monde. Puis, nous avons cherché à caractériser et à comprendre la dynamique des populations de ces deux espècesde rats sympatriques ainsi que leurs interactions avec la biodiversité native en forêt dense humide du massif du Mont Panié.Des opérations de piégeage létal et de capture-marquage-recapture ont montré que les rats noirs étaient plus abondants que lesrats du Pacifique. Les analyses de leur régime alimentaire ont révélé que les deux espèces ont à la fois des proies communeset des proies qui leur sont propres impliquant un renforcement ainsi qu'un élargissement de leurs impacts sur la biodiversiténative. Les rats consomment une grande majorité de fruits et de graines, d'invertébrés et de Squamates mais les oiseaux, quijustifient souvent la mise en place de projets de gestion de rats, ne semblent pas ici être une de leur proie préférentielle. Depotentiels effets positifs des rats sur la dispersion des graines ont également été mis en évidence au travers d'une comparaisondu potentiel germinatif de graines après passage par leur tractus digestif et celui de frugivores natifs. Enfin, nous avons puproposer des stratégies de piégeage létal afin de contrôler efficacement les populations de rats invasifs. Une meilleurecompréhension des impacts des rats en situation de sympatrie ainsi qu' une meilleure connaissance du lien entre densité de ratset intensité des effets sur la biodiversité permettraient d'optimiser les stratégies de contrôle de rats invasifs lorsquel'éradication n'est pas envisageable. / Introduced rats (Rattus spp.) are one of the major invasive species threatening native biodiversity on islands worldwide. Twospecies, the black rat (R. rattus) and the Pacifie rat (R. exulans) are sympatric in New Caledonian rainforests, where questionsasto the feasibility and the utility of their control (i.e. local limitation of their abundance) for the conservation of nativebiodiversity remain unanswered. ln response to the lack of a conceptual framework for control projects, we fi rst conducted areview of invasive rat control operations in island natural areas worldwide. Then we sought to characterize and understand thepopulation dynamics of these two sympa tric rat species and the ir interactions with native biodiversity in the rainforest of MontPanié mountain. Lethaltrapping operations and capture-mark-recapture showed that black rats were more abundant thanPacifie rats. Diet analysis revealed that the two species consume both shared and unshared prey likely resulting in astrengthening and a broadening oftheir impacts on native biodiversity, relative to the impact that each species would haveal one. Rats consume a large quantity of fruits and seeds, invertebrates, and Squamates. However, birds, which often justify theimplementation of rat management projects, do not appear here to be one of the ir preferred prey, either as adults or throughnest predation. A potential positive rat impact on seed dispersal was a Iso highlighted through a comparison of seedgermination after seeds had passed through rat versus native frugivore digestive tracts. Finally, we propose lethal trappingstrategies to efficiently control invasive rat populations. A better understanding ofboth rat impacts in sympatric situations,and the link between rat density and the intensity of their effects on biodiversity would allow optimizing rat control strategieswhen eradication is not feas ible.

Le chat haret est l’un des prédateurs invasifs les plus dommageables pour la biodiversité insulaire. Sa présence est associée à une perte de biodiversité sur l’ensemble des îles sur lesquelles il est établi, et où il constitue une menace pour de nombreuses espèces de vertébrés souvent endémiques et menacés. En Nouvelle-Calédonie des populations de chats harets sont présentes dans tous les milieux et habitats et l’étude de son écologie et de ses impacts sur la faune ont fait l’objet de ce travail de thèse. L’analyse du régime alimentaire sur 14 sites d’études représentatifs des 4 habitats majeurs a révélé un régime très diversifié et une forte prédation sur les vertébrés natifs et notamment sur le groupe des scinques, des roussettes et des pétrels. Parmi les 44 espèces de vertébrés retrouvées dans le régime alimentaire de ce prédateur invasif, la plupart sont endémiques et 20 listées comme menacées sur la liste rouge mondiale de l’UICN. Le suivi des déplacements d’individus équipés de colliers GPS au niveau d’une presqu’île abritant une importante colonie d’oiseaux marins, a permis de mettre en évidence de grands domaines vitaux pour les mâles, des domaines vitaux petits pour les femelles et des patrons de déplacements liés aux différentes étapes du cycle reproducteur des oiseaux marins. Ces éléments, couplés aux analyses de régime alimentaire suggèrent une prédation à une large échelle géographique, à la fois sur les adultes reproducteurs mais également sur les jeunes oiseaux proches de l’envol. Une opération expérimentale de contrôle d’une population de chats harets a été conduite sur cette presqu’île et a montré une faible durabilité des effets de la suppression des individus sur les densités observées et une rapide recolonisation du site. Les résultats de ce travail plaident pour la mise en place de mesures de limitation des impacts occasionnés et permettent en particulier de cibler les habitats de maquis et forêt humide comme prioritaires en matière de limitation des abondances. / Feral cat (Felis catus) is one of the most successful and harmful invasive predator species for island biodiversity. The presence of this alien predator species generally lead to dramatic loss of native island biodiversity and represents a serious threat for numerous endemic and threatened species. Feral cats have invaded the whole New-Caledonian archipelago and all its habitats. In this study, we focused on the ecology and impacts of this invasive predator on the outstanding endemic fauna found in the different habitats of the exceptional New-Caledonia biodiversity hotspot. Feral cat diet analyses on 14 selected sites representing the 4 main natural habitats revealed a high diversified diet and high predation rates on native species particularly on squamates, flying foxes and petrels. Among the 44 vertebrates species found into the feral cat diet, 20 are IUCN red-listed threatened species. Cat movements of eleven feral cats fitted with GPS collars have been studied in a western coast Peninsula hosting an important seabird colony. Male cats showed large home ranges while female showed small home ranges. Feral cats exhibited important movements within the studied peninsula linked with the breeding cycles of seabirds. GPS data coupled with dietary informations suggested a predation that concerned both breeding adults and fledgings bird, and at a large geographic scale as some feral cats have their core home range distant to the colony (>3km). We evaluated the effects of a high level but intense cat control on this site that showed a low sustainability of feral cat culling and a rapid recolonization process. Our results are pleading for the future limitation of feral cat impacts and call to focus first abundance limitation measures on maquis mosaic and humid forest habitats This study also provided information on the spatial extent and intensity of future control measures in the special context of a large and highly invaded island.